Modern food microbiology 6th ed james m jay

Modern Food Microbiology Sixth Edition James M Jay Professor Emeritus Wayne State University Detroit, Michigan Adjunct Professor University of Nevada Las Vegas Las Vegas, Nevada AN ASPEN PUBLICATION® Aspen Publishers, Inc Gaithersburg, Maryland 2000 The author has made every effort to ensure the accuracy of the information herein However, appropriate information sources should be consulted The author, editors, and the publisher cannot be held responsible for any typographical or other errors found in this book Library of Congress Cataloging-in-Publication Data Jay, James M (James Monroe), 1927— Modern food microbiology / James M Jay.—6th ed p cm — (Aspen food science text series) Includes bibliographical references and index ISBN 0-8342-1671-X Food—Microbiology I Title II Series QR115.J3 2000 664'001'579—dc21 99-054735 Copyright O 2000 by Aspen Publishers, Inc A Wolters Kluwer Company www.aspenpublishers.com All rights reserved Aspen Publishers, Inc., grants permission for photocopying for limited personal or internal use This consent does not extend to other kinds of copying, such as copying for general distribution, for advertising or promotional purposes, for creating new collective works, or for resale For information, address Aspen Publishers, Inc., Permissions Department, 200 Orchard Ridge Drive, Suite 200, Gaithersburg, Maryland 20878 Orders: (800) 638-8437 Customer Service: (800) 234-1660 About Aspen Publishers • For more than 40 years, Aspen has been a leading professional publisher in a variety of disciplines Aspen's vast information resources are available in both print and electronic formats We are committed to providing the highest quality information available in the most appropriate format for our customers Visit Aspen's Internet site for more information resources, directories, articles, and a searchable version of Aspen's full catalog, including the most recent publications: www.aspenpublishers.com Aspen Publishers, Inc • The hallmark of quality in publishing Member of the worldwide Wolters Kluwer group Editorial Services: Joan Sesma Library of Congress Catalog Card Number: 99-054735 ISBN: 0-8342-1671-X Printed in the United States of America Preface The sixth edition of Modern Food Microbiology, like the previous edition, focuses on the general biology of the microorganisms that are found in foods Thus, the contents are suitable for its use in a second or subsequent course in a microbiology curriculum, or as a primary food microbiology course in a food science or food technology curriculum Although organic chemistry is a desirable prerequisite, it is not necessary for one to get a good grasp of the topics covered When used as a microbiology text, the following sequence has been found to be suitable A synopsis of the information in Chapter will provide students with a sense of the historical developments that have shaped this discipline and how it continues to evolve Memorization of the many dates and events is not recommended since much of this information is presented again in the respective chapters The material in Chapter is designed to provide a brief background on microorganisms in nature with emphasis on those that are important in foods This material can be combined with the intrinsic and extrinsic parameters of growth in Chapter as they exist in food products and as they affect the common foodborne organisms Chapters to deal with specific food products and they may be covered to the extent desired with appropriate reviews of the relevant topics in Chapter Chapters 10 to 12 cover methods for culturing and identifying foodborne organisms and/or their products, and these topics may be dealt with in this sequence or just before foodborne pathogens The food preservation methods in Chapters 13 to 19 include information that goes beyond the usual scope of a second course Chapters 14 and 19 are new to the sixth edition Chapter 14 consolidates information from the previous edition that was scattered throughout several chapters, and it contains much new information on modified atmosphere packaging Chapter 19 covers high pressure and pulsed electric field processing of foods, and it contains two sections taken from the chapter on high temperature processing in the previous edition Chapters 20 and 21 deal with food sanitation, indicator organisms, and the HACCP system, and coverage of these topics is suggested before dealing with the pathogens Chapters 22 to 31 deal with the known (and some suspected) foodborne pathogens including their biology and methods of control Chapter 22 is also new to this edition and it is intended to provide an overview of the chapters that follow The material in this chapter that deals with mechanisms of pathogenesis is probably best dealt with when the specific pathogens are covered in their respective chapters For most semester courses with a 3-credit lecture and accompanying or credit laboratory, only about 70% of the material in this edition is likely to be covered The remainder is meant for reference purposes Citations for new and updated material can be found in the Reference lists at the end of the chapters The following individuals assisted me by critiquing various parts or sections of the sixth edition, and I pay my special thanks to each: P Druggan, P Feng, R.B Gravani, D.R Henning, YJ Lee, J.A Seiter, L.A Shelef, J.N Sofos, A.C.L Wong, and A.E Yousef Those who assisted me with the previous five editions are acknowledged in the respective editions Contents Preface xv Part I Historical Background 1 History of Microorganisms in Food Historical Developments Part II Habitats, Taxonomy, and Growth Parameters 11 Taxonomy, Role, and Significance of Microorganisms in Foods 13 Bacterial Taxonomy 13 Primary Sources of Microorganisms Found in Foods 17 Synopsis of Common Foodborne Bacteria 19 Synopsis of Common Genera of Foodborne Molds 24 Synopsis of Common Genera of Foodborne Yeasts 29 Intrinsic and Extrinsic Parameters of Foods That Affect Microbial Growth 35 Intrinsic Parameters 35 Extrinsic Parameters 49 Combined Intrinsic and Extrinsic Parameters: The Hurdle Concept 53 Part III Microorganisms in Foods 57 Fresh Meats and Poultry 59 Biochemical Events That Lead to Rigor Mortis 60 The Biota of Meats and Poultry 60 Incidence/Prevalence of Microorganisms in Fresh Red Meats 60 Microbial Spoilage of Fresh Red Meats 68 Spoilage of Fresh Livers 76 Incidence/Prevalence of Microorganisms in Fresh Poultry 77 Microbial Spoilage of Poultry 78 Carcass Sanitizing/Washing 81 This page has been reformatted by Knovel to provide easier navigation v vi Contents Processed Meats 87 Curing 87 Smoking 89 Sausage, Bacon, Bologna, and Related Products 89 Bacon and Cured Hams 91 Fermented Meat Products 93 Seafoods 101 Microbiological Quality of Various Fresh and Frozen Products 101 Fermented Fish Products 104 Spoilage of Fish and Shellfish 105 Fermentation and Fermented Dairy Products 113 Fermentation 113 Dairy Products 119 Apparent Health Benefits of Fermented Milks 124 Diseases Caused by Lactic Acid Bacteria 128 Fruit and Vegetable Products: Whole, Fresh-Cut, and Fermented 131 Fresh and Frozen Vegetables 131 Spoilage of Fruits 141 Fresh-Cut Produce 141 Fermented Products 146 Miscellaneous Fermented Products 154 Miscellaneous Food Products 163 Delicatessen and Related Foods 163 Eggs 164 Mayonnaise and Salad Dressing 167 Cereals, Flour, and Dough Products 168 Bakery Products 168 Frozen Meat Pies 168 Sugar, Candies, and Spices 169 Nutmeats 169 Dehydrated Foods 170 Enteral Nutrient Solutions (Medical Foods) 171 Single-Cell Protein 171 This page has been reformatted by Knovel to provide easier navigation Contents vii Part IV Determining Microorganisms and/or Their Products in Foods 177 10 Culture, Microscopic, and Sampling Methods 179 Conventional Standard Plate Count 179 Membrane Filters 182 Microscope Colony Counts 184 Agar Droplets 184 Dry Film and Related Methods 185 Most Probable Numbers 186 Dye Reduction 186 Roll Tubes 187 Direct Microscopic Count 187 Microbiological Examination of Surfaces 188 Metabolically Injured Organisms 190 Viable but Nonculturable Organisms 194 11 Physical, Chemical, Molecular, and Immunological Methods 201 Physical Methods 201 Chemical Methods 206 Methods for Characterizing and Fingerprinting Foodborne Organisms 214 Immunological Methods 221 12 Bioassay and Related Methods 237 Whole-Animal Assays 237 Animal Models Requiring Surgical Procedures 242 Cell Culture Systems 243 Part V Food Preservation and Some Properties of Psychrotrophs, Thermophiles, and Radiation-Resistant Bacteria 251 13 Food Preservation with Chemicals 253 Benzoic Acid and the Parabens 253 Sorbic Acid 255 The Propionates 257 Sulfur Dioxide and Sulfites 257 This page has been reformatted by Knovel to provide easier navigation viii Contents Nitrites and Nitrates 258 NaCl and Sugars 264 Indirect Antimicrobials 265 Acetic and Lactic Acids 268 Antibiotics and Bacteriocins 268 Antifungal Agents for Fruits 274 Ethylene and Propylene Oxides 274 Miscellaneous Chemical Preservatives 275 14 Food Preservation with Modified Atmospheres 283 Definitions 283 Primary Effects of CO2 on Microorganisms 286 Food Products 288 The Safety of MAP Foods 290 Spoilage of MAP and Vacuum-Packaged Meats 293 15 Radiation Preservation of Foods and Nature of Microbial Radiation Resistance 301 Characteristics of Radiations of Interest in Food Preservation 301 Principles Underlying the Destruction of Microorganisms by Irradiation 303 Processing of Foods for Irradiation 305 Application of Radiation 305 Radappertization, Radicidation, and Radurization of Foods 306 Legal Status of Food Irradiation 312 Effect of Irradiation on Food Quality 313 Storage Stability of Irradiated Foods 315 Nature of Radiation Resistance of Microorganisms 315 16 Low-Temperature Food Preservation and Characteristics of Psychrotrophic Microorganisms 323 Definitions 323 Temperature Growth Minima 324 Preparation of Foods for Freezing 324 Freezing of Foods and Freezing Effects 325 Storage Stability of Frozen Foods 327 This page has been reformatted by Knovel to provide easier navigation Contents ix Effect of Freezing on Microorganisms 327 Some Characteristics of Psychrotrophs and Psychrophiles 331 The Effect of Low Temperatures on Microbial Physiologic Mechanisms 333 Nature of the Low Heat Resistance of Psychrotrophs 336 17 High-Temperature Food Preservation and Characteristics of Thermophilic Microorganisms 341 Factors Affecting Heat Resistance in Microorganisms 342 Relative Heat Resistance of Microorganisms 346 Thermal Destruction of Microorganisms 348 Some Characteristics of Thermophiles 351 Other Aspects of Thermophilic Microorganisms 354 Canned Food Spoilage 356 18 Preservation of Foods by Drying 363 Preparation and Drying of Low-Moisture Foods 363 Effect of Drying on Microorganisms 364 Storage Stability of Dried Foods 366 Intermediate-Moisture Foods 367 19 Other Food Preservation Methods 375 High-Pressure Processing 375 Pulsed Electric Fields 379 Aseptic Packaging 380 Manothermosonication (Thermoultrasonication) 381 Part VI Indicators of Food Safety and Quality, Principles of Quality Control, and Microbial Criteria 385 20 Indicators of Food Microbial Quality and Safety 387 Indicators of Product Quality 387 Indicators of Food Safety 388 The Possible Overuse of Fecal Indicator Organisms 401 Predictive Microbiology/Microbial Modeling 402 21 The HACCP System and Food Safety 407 Hazard Analysis Critical Control Point System 407 Microbiological Criteria 415 This page has been reformatted by Knovel to provide easier navigation x Contents Part VII Foodborne Diseases 423 22 Introduction to Foodborne Pathogens 425 Introduction 425 Host Invasion 425 Pathogenesis 428 Summary 434 23 Staphylococcal Gastroenteritis 441 Species of Concern in Foods 441 Habitat and Distribution 443 Incidence in Foods 443 Nutritional Requirements for Growth 444 Temperature Growth Range 444 Effect of Salts and Other Chemicals 444 Effect of pH, Water Activity, and Other Parameters 444 Staphylococcal Enterotoxins: Types and Incidence 445 The Gastroenteritis Syndrome 453 Incidence and Vehicle Foods 454 Ecology of S aureus Growth 455 Prevention of Staphylococcal and Other Food-Poisoning Syndromes 455 24 Food Poisoning Caused by Gram-Positive Sporeforming Bacteria 461 Clostridium perfringens Food Poisoning 461 Botulism 466 Bacillus Cereus Gastroenteritis 477 25 Foodborne Listeriosis 485 Taxonomy of Listeria 485 Growth 488 Distribution 492 Thermal Properties 494 Virulence Properties 497 Animal Models and Infectious Dose 498 Incidence and Nature of the Listeriosis Syndromes 500 Resistance to Listeriosis 502 This page has been reformatted by Knovel to provide easier navigation A hydrophila is an aquatic bacterium found more in salt waters than in fresh waters It is a significant pathogen to fish, turtles, frogs, snails, and alligators and a human pathogen, especially in compromised hosts It is a common member of the bacterial flora of pigs Diarrhea, endocarditis, meningitis, soft-tissue infections, and bacteremia are caused by A hydrophila Virulent strains of A hydrophila produce a 52-kDa single polypeptide that possesses enterotoxic, cytotoxic, and hemolytic activities This multifunctional molecule displays immunological cross-reactivity with the cholera toxin.84 According to some investigators,103 it resembles aerolysin while others contend that it is aerolysin.7 Aerolysin is a pore- or channel-forming toxin that kills cells by forming discrete channels in their plasma membranes.9 Ion channels are created by the oligomerization of toxin molecules Cytotonic activity has been associated with an A hydrophila toxin, which induced rounding and steroidogenesis inY-I adrenal cells Also, positive responses in the rabbit ileal loop, suckling mouse, and CHO assays have been reported for a cytotonic toxin.25 A large number of studies have been conducted on A hydrophila isolates from various sources In one study, 66 of 96 (69%) isolates produced cytotoxins, whereas 32 (80%) of 40 isolates from diarrheal disease victims were toxigenic, with only 41% of nondiarrheal isolates being positive for cytotoxin production Most enterotoxigenic strains are VP (VogesProskauer test) and hemolysin positive and arabinose negative10 and produce positive responses in the suckling mouse, Y-I adrenal cell, and rabbit ileal loop assays In a study of 147 isolates from patients with diarrhea, % were enterotoxigenic, whereas only 70% of 94 environmental strains produced enterotoxin as assessed by the suckling mouse assay.11 All but four of the clinical isolates produced hemolysis of rabbit red blood cells Of 116 isolates from the Chesapeake Bay, 71% were toxic by the Y1I adrenal cell assay, and toxicity correlated with Iysine decarboxylase and VP reactions.50 In yet another study, 48 of 51 cultures from humans, animals, water, and sewage produced positive responses in rabbit ileal loop assays with 103 or more cells, and cell-free extracts from all were loop positive.2 Isolates from meat and meat products possessed biochemical markers that are generally associated with toxic strains of other species, with the mouse median lethal dose (LD50) being log 8-9 colony-forming units (cfu) for most strains tested.78 The latter investigators suggested the possibility that immunosuppressive states are important factors in food-associated infections by this organism, a suggestion that could explain the difficulty of establishing this organism as the sole etiological agent of foodborne gastroenteritis With regard to growth temperature and habitat, of 13 strains displayed growth at 0-5 C, of 13 at 100C, and at a minimum of 15°C.85 The psychrotrophs had optimum growth between 150C and 200C The maximum growth temperature for some strains was 40—450C with optimum at 35°C.42 Regarding distribution, the organism was found in all but 12 of 147 lotic and lentic habitats.42 Four of those habitats that did not yield the organism were either hypersaline lakes or geothermal springs Some waters contained up to 9,000/mL An ecological study of A hydrophila in the Chesapeake Bay revealed numbers ranging from less than 0.3/L to x 103/mL in the water column, and about 4.6 x 102/g of sediment.50 The presence of this organism correlated with total, aerobic, viable, and heterotrophic bacterial counts, and its presence was inversely related to dissolved O2 and salinity, with the upper salt level being about 15% Fewer were found during the winter than during the summer months Plesiomonas P shigelloides is found in surface waters and soil and has been recovered from fish, shellfish, other aquatic animals, as well as from terrestrial meat animals It differs from A hydrophila in having G + C content of DNA of 51%, versus 58-62% for A hydrophila It has been isolated by many investigators from patients with diarrhea and is associated with other general infections in humans It produces a heat-stable enterotoxin, and serogroup 0:17 strains react with Shigella group D antisera.1 In a study of 16 strains from humans with intestinal illness, R shigelloides did not always bind Congo red, the strains were noninvasive in HEp-2 cells, and they did not produce Shiga-like toxin on Vero cells.1 Although a low-level cytolysin was produced consistently, the mean LD50 for outbred Swiss mice was 3.5 x 108 cfu Heat-stable enterotoxin was not produced by either of the 16 strains, and it was the conclusion of these investigators that this organism possesses a low pathogenic potential.1 R shigelloides was recovered by Zajc-Satler et al.105 from the stools of six diarrheal patients It was believed to be the etiological agent, although salmonellae were recovered from two patients Two outbreaks of acute diarrheal disease occurred in Osaka, Japan, in 1973 and 1974, and the only bacterial pathogen recovered from stools was R shigelloides In the 1973 outbreak, 978 of 2,141 persons became ill, with 88% complaining of diarrhea, 82% of abdominal pain, 22% of fever, and 13% of headaches.96 Symptoms lasted to days Of 124 stools examined, 21 yielded R shigelloides 017:H2 The same serovar was recovered from tap water In the 1974 outbreak, 24 of 35 persons became ill with symptoms similar to those noted R shigelloides serovar 024:H5 was recovered from three of eight stools "virtually in pure culture."96 The organism was recovered from 39% of 342 water and mud samples, as well as from fish, shellfish, and newts A 15-year-old female contracted gastroenteritis, and hours after she took one tablet of trimethoprim-sulfadiazine,/? shigelloides could be recovered from her blood.79 The latter investigators noted that 10 of the previously known 12 cases of R shigelloides bacteremia were in patients who were either immunocompromised or presented with other similar conditions The 15-year-old had a temperature of 39°C and passed up to 10 watery stools daily The isolated strain reacted with S dysenteriae serotype antiserum, placing it in O group 22 of R shigelloides.11 Growth of R shigelloides has been observed at 100C,85 and 59% of 59 fish from Zaire waters contained the organism.98 In the latter study, the organism was found more in river fish than lake fish It appeared not to produce an enterotoxin since only of 29 isolates produced positive responses in rabbit ileal loops.87 Foodborne cases have not been documented, but the organism has been incriminated in at least two outbreaks.68 Bacteroides fragilis This obligately anaerobic, gram-negative bacterium is of potential significance as a foodborne pathogen since it produces an ileal loop-positive enterotoxin and is often associated with human diarrhea, as are A hydrophila and P shigelloides The enterotoxin was first demonstrated in 1984, and enterotoxic strains of B fragilis were first associated with human diarrhea in 1987 B fragilis is estimated to constitute between 1% and 2% of the human intestinal flora As a non-spore former, it is more sensitive to aerated environments than the clostridia and yet it has been recovered from municipal sewage This species differs from most other Bacteroides in being catalase positive, and like most others it can grow in the presence of 20% bile The B fragilis enterotoxin is produced as a single chain with a molecular weight of about 20,000 Da It differs from the classic bacterial enterotoxins in belonging to a class of zinc-binding metalloprotease, designated metzincins The enterotoxin has a wide range of protein substrates, and it undergoes autodigestion The intestinal damage that it causes is believed to be due, at least in part, to its proteolytic action It elicits a positive response in ileal loops of lambs and other animals (for more information see references 69 and 76) Since the etiological agent is identified in only around 50% of foodborne outbreaks in the United States, it is clear that previously unrec- ognized agents need to be included B fragilis along with Klebsiella pneumoniae54 and Enterobacter cloacae55 may warrant more attention The latter two organisms produce heatstable enterotoxins that are similar to the heatstable enterotoxin (ST) of E coll, and their potential significance in foods has been noted.97 Erysipelothrix rhusiopathiae This bacterium (Erysipe'lothrix rhu-si-o-pa' -thi-ae) is phylogenetically closely related to Listeria (see Chapter 25), and like L monocytogenes, it causes disease in animals and humans It is the cause of erysipelas in swine and erysipeloid in humans Because of these similarities, it seems to be a "logical" candidate for a foodborne pathogen although such cases seem not to have been reported In general, erysipeloid is a localized disease of the hands and arms of handlers of fresh meat and fish, but systemic involvements are not unknown The organism is a facultative anaerobe, catalase negative (in contrast to the listeriae), oxidase negative, and generally produces H2S At least 23 serovars are known The only other species is E tonsillarum, which was separated from E rhusiopathiae based on its primary habitat of porcine tongues, and because of serovar differences.90 One of the first if not the first studies of the incidence of this organism in foods is that of Ternstrom and Molin,94 who in 1982 undertook a study of foodborne pathogens in meats in Sweden They examined 135 samples consisting of equal numbers of chicken, beef, and pork, and founds, rhusiopathiae in 36% and 13%, respectively, of pork and chicken, but none in beef In one plant, 54% of pork loins were positive, and many of the isolates possessed mouse virulence Of 112 retail pork samples examined in Japan, 34% contained this bacterium, and the 38 isolates represented 14 serovars.88 In a study of meat samples from 93 wild boar and 36 deer in Japan, 44% of the wild boar and 50% of the deer samples contained E rhusiopathiae, represent- ing 13 serovars.49 In a study of 750 chickens in Japan, Erysipelothrix spp were recovered from 15.7% of skin samples, and from 59.2% of 179 feather samples.71 E rhusiopathiae represented 273 of 297 isolates and the remainder were E tonsillarum In another study of 153 chicken samples in Japan, 30% contained Erysipelothrix spp with 65 of 67 being E rhusiopathiae.72 Klebsiella pneumoniae About hours after consuming a fast-food chain hamburger, an individual complained of not feeling well After hospital admission, this organism along with generic E coli was isolated from leftover hamburger and from the patient's blood, and the two matched by cultural methods.86 The strain of K pneumoniae was LT+ and ST- The coliform count in leftover hamburger was 3.0 x 106/g, and 1.9 x 105/g of bun Streptococcus iniae There have been at least six human infections by this organism traced to a fish product S iniae was first recognized in 1972 as the cause of a disease in Amazon dolphins.16 It was next recorded in Israel in 1986 as the cause of disease in tilapia and trout, and later seen in Taiwan and the United States.81 The first human case was recorded in 1991 in Texas, and the second in 1994 in Ottawa.16 Four human cases occurred in Ontario, Canada, in 1995-1996 and the organism was isolated from both fish and patients The fish was tilapia that was imported from fish farms in the United States S iniae appears to be a fish pathogen that causes disease in humans In the Ontario cases, it appeared that the organism entered the body through hand lesions It is beta-hemolytic on sheep blood Prion Diseases Prions are unique proteins in that they can convert other proteins into damaging ones by causing them to alter their shape The normal cell prion protein (PrP) exists in the brain cell membrane where it carries out some vital functions and is then degraded by proteases However, the pathogenic form is distorted and is resistant to proteases, and thus it accumulates in brain tissue and gives rise to disease (see below) It has been postulated that the distorted prion molecule, acting as a template, converts normal protein to a distorted form.7 These particles were named around 1982 by Stanley Prusiner, who was awarded the 1997 Nobel Prize in physiology for his pioneering work." Prions cause the disease scrapie in sheep, goats, and hamsters; and kuru in humans Another prion disease of humans in CreutzfeldtJakob disease (CJD) Bovine spongiform encephalopathy (BSE) is a prion disease of cattle and sheep that has in the past been referred to as "mad cow disease." All of these belong to a family of diseases called transmissible spongiform encephalopathies (TSEs) In all prion neurodegenerative diseases, the pathogenic forms are termed PrPres The latter has a strong tendency to aggregate into amyloid fibrils, and PrPres along with PrP cause nerve cell degeneration and lead to clinical signs of disease Although the TSEs are widely believed to be caused by prions, the possibility that a virus is the agent has been raised.26 BSE was first recognized in Great Britain in 1984 and specifically diagnosed in cattle in 1986 Four years later, over 14,000 confirmed cases out of a population of 10 million cattle had been recognized in Great Britain The epidemic seemed to peak around 1,000 new cases per week in 1993 By February 1998, a total of 172,324 cases were seen in cattle in the United Kingdom.7 A total of 600 cases were recorded in countries outside the United Kingdom with 256 (42.7%) in Switzerland.7 No confirmed cases of BSE in cattle have been seen in the United States Since humans are susceptible to the prions that cause CJD, the concern is whether humans can contract BSE from cattle In March 1996, a new variant of CJD (nvCJD, V-CJD) was reported in the United Kingdom in a small group of people, all of whom were much younger than most indi- viduals with CJD This prompted speculation that nvCJD had been contracted from cattle Normally, CJD appears in persons around age 60 or older, but nvCJD in the United Kingdom was found to afflict individuals in age from the late teens to the early 40s It has been suggested that nvCJD is the human equivalent of BSE,102 and the agents for BSE and nvCJD appear to be the same based on studies using mice.8 Between February 1994 and October 1995, 10 persons in the United Kingdom were found to have the new variant form of CJD, and died Most were under age 30 (in the United States, most CJD victims are over age 55; see below) Through April 6, 1998, a total of 24 cases of nvCJD had been recognized in the United Kingdom.7 For the 5-year period 1991-1995, 94 CJD deaths were recorded in the United States and were below age 55.17 None conformed to nvCJD BSE is thought to have been contracted by cattle through specified bovine offal (that contained brain, spinal cord, and the like) from infected animals, a practice that was banned in 1989 Using a mouse assay, prions could not be detected in beef muscle and milk from infected cattle.7 The incubation period for BSE is between and 15 years Regarding the heat destruction of the prions of nvCJD, studies are wanting However, data on scrapie and CJD have been presented and summarized.12 The latter investigator suggested that the brain tissue of a TSE-infected cow can be expected to contain about 1011 prions per gram Assuming that the nerve tissue is ground with muscle tissue, about 108 prions per gram may be expected in ground beef, or 1010 prions in a 100g portion To effect a 12-D reduction, 22D is required (10 + 12 = 22) Thus, some of the times in minutes needed to achieve a 22D were calculated as follows: D160°c = -0; D140°c =11.0; D120°c = 110.12 It has been suggested that there is a need for new processing or packaging technologies such that high-temperature short-time treatments can be carried out in order to render products free of prions.12 For more information, see references and 29 TOXIGENIC PHYTOPLANKTONS Paralytic Shellfish Poisoning This syndrome is contracted by eating toxic mussels, clams, oysters, scallops, or cockles These bivalves become toxic after feeding on certain dinoflagellates of which Gonyaulax catenella is representative of the U.S Pacific Coast flora Along the North Atlantic Coast of the United States and over to northern Europe, G tamarensis is found, and its poison is more toxic than that of G catenella G acatenella is found along the coast of British Columbia Masses or blooms of these toxic dinoflagellates give rise to the red tide condition of seas In 1996, about 150 manatees were killed during a red tide off the coast of Florida The paralytic shellfish poison (PSP) is saxitoxin, and its structural formula is as follows: year period 1973-1987, 19 outbreaks (with a mean of cases) were reported by state health departments to the CDC In 1990, there were 19 cases from two outbreaks in the states of Massachusetts and Alaska alone In the former, six fishermen became ill after eating boiled mussels that contained 4,280 jig/100 g saxitoxin.20 The raw mussels contained 24,400 jug/100 g.The 13 cases in Alaska resulted in death, and gastric contents from the victim who died contained 370 jLig/100 g of PSP toxin, whereas a sample of the butterclam that was consumed contained 2,650 ug/100 g.20The maximum safe level of PSP toxinis80|Lig/100g.20 Outbreaks of PSP seem to occur between the months of May and October on the U.S West Coast and between August and October on the East Coast Mollusks may become toxic in the absence of red tides Detoxification of mollusks can be achieved by their transfer to clean water, and a month or more may be required Ciguatera Poisoning Saxitoxin exerts its effect in humans through cardiovascular collapse and respiratory failure It blocks the propagation of nerve impulses without depolarization, and there is no known antidote It is heat stable, water soluble, and generally not destroyed by cooking It can be destroyed by boiling 3-4 hours at pH of 3.0 A D value at 2500F of 71.4 minutes in soft-shell clams has been reported.41 Symptoms of PSP develop within hours after ingestion of toxic mollusks, and they are characterized by paresthesia (tingling, numbness, or burning), which begins about the mouth, lips, and tongue and later spreads over the face, scalp, and neck, and to the fingertips and toes The mortality rate is variously reported to range from I%to22% Between 1793 and 1958, some 792 cases were recorded, with 173 (22%) deaths.66 In the 15- This syndrome is contracted from the ingestion of any one of over 300 fish species (barracuda, grouper, sea bass, etc.) that feed on herbivorous or reef fishes, which in turn feed on phytoplankton, especially the dinoflagellates The responsible dinoflagellate is Gambierdiscus toxicus, which produces ciguatoxin This toxin is concentrated more in fish organs such as the liver than in muscle tissue Upon ingestion of toxic fish, symptoms occur within 3-6 hours (about the same as for staphylococcal food poisoning), and consist of nausea and paresthesia about the mouth, tongue, and throat In general, the symptoms are quite similar to those for paralytic shellfish poisoning Respiratory paralysis is the consequence in the absence of appropriate therapy For the years 1983-1992, 129 outbreaks were reported to the CDC involving 508 persons with no deaths.13 An outbreak in Texas in 1997 involved 17 crew members of a cargo ship, and the vehicle food was barracuda.13 DomoicAcid This is an uncommon amino acid that antagonizes glutamic acid in the central nervous system It is produced by a diatom, Pseudonitzschia pungens, and its structure is as indicated (Diatoms are single-celled algae with walls of silicon.) Domoic acid causes amnesic shellfish poisoning (ASP) following the consumption of mussels or scallops harvested from marine waters with a bloom of the diatom noted The first recorded outbreak of human cases occurred in eastern Canada in 1988 following the consumption of mussels from Prince Edward Island,80 and there were 107 victims and three deaths Since this episode, domoic acid-producing diatoms have been found in other parts of the world An ASP episode affected scallops in northwest Spain in 1996.65 The largest quantity of domoic acid was found in the hepatopancreas—from 52% to 88% of the total.65 During frozen storage, some domoic acid transferred to other parts of the scallops It was found that canning of scallops did not destroy this toxic principal According to Leira et al.,65 the Canadian regulatory level is 20 ug/g of tissue for fresh bivalve mollusks Pfiesteria piscicida This dinoflagellate was first recognized in the early 1990s as the cause of death of thousands offish in tributaries of the Chesapeake Bay It is an animal-like organism that produces potent toxins One toxin stuns fish within a few seconds, and the animals die within a few minutes It is heat stable Another toxin causes the fish epidermis to slough off The dinoflagellate reproduces sexually after a fish kill, and it can encyst The exact identity of the toxins is unclear, as are their effect on humans Those who have been exposed have a history of memory loss, confusion, acute skin burning, and usually general symptoms such as headache, skin rash, muscle cramps, and the like.14 REFERENCES Abbott, S.L., R.P Kokka, and J.M Janda 1991 Laboratory investigations on the low pathogenic potential of Plesiomonas shigelloides J CHn Microbiol 29:148-153 Annapurna, E., and S C Sanyal 1977 Enterotoxicity of Aeromonas hydrophila J Med Microbiol 10: 317-323 Appleton, H., and M.S Pereira 1977 A possible virus aetiology in outbreaks of food-poisoning from cockles Lancet 1:780-781 Atmar, R.L., RH Neill, J.L Romalde, et al 1995 Detection of Norwalk virus and hepatitis A virus in shellfish tissues with the PCR Appl Environ Microbiol 61:3014-3018 Behling, A.R., and S.L Taylor 1982 Bacterial histamine production as a function of temperature and time of incubation J Food ScL 47:1311-1314, 1317 Blackwell, J.H., D Rickansrud, P.D McKercher, et al 1982 Effect of thermal processing on the survival of foot-and-mouth disease virus in ground meat J Food Sd 47:388-392 Blanchfield, J.R 1998 Bovine spongiform encephalopathy (BSE)—a review Int J Food Sd Technol 33:81-97 Bruce, M.E., R.G Will, IW Ironside, et al 1997 Transmissions to mice indicate that 'new variant' CJD is caused by the BSE agent Nature 389:498-501 Buckley, J.T., and S.P Howard 1999 The cytotoxic enterotoxin of Aeromonas hydrophila is aerolysin Infect Immun 67:466-467 10 Burke, V, J Robinson, H.M Atkinson, et al 1982 Biochemical characteristics of enterotoxigenic Aeromonas spp J CHn Microbiol 15:48-52 11 Burke, V, J Robinson, M Cooper, et al 1984 Biotyping and virulence factors in clinical and envi- 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 ronmental isolates of Aeromonas species Appl Environ Microbiol 47:1146-1149 Casolari, A 1998 Heat resistance of prions and food processing Food Microbiol 15:59-63 Centers for Disease Control and Prevention 1998 Ciguatera fish poisoning—Texas, 1997 MMWR Morb Mort WkIy Rep 47:692-694 Centers for Disease Control and Prevention 1997 Results of the public health response to Pfiesteria workshop—Atlanta, Georgia, September 29-30, 1997 MMWR Morb Mort WUy Rep 46:951-952 Centers for Disease Control and Prevention 1997 Viral gastroenteritis associated with eating oysters— Louisiana, December 1996-January 1997 MMWR Morb Mort WkIy Rep 46:1109-1112 Centers for Disease Control and Prevention 1996 Invasive infection with Streptococcus iniae—Ontario, 1995-1996 MMWR Morb Mort WkIy Rep 45: 650-653 Centers for Disease Control and Prevention 1996 Surveillance for Crutzfeldt-Jakob disease—United States 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Control and Prevention 1987 Outbreak of viral gastroenteritis—Pennsylvania and Delaware MMWR Morb Mort WkIy Rep 36: 709-711 Chakraborty, T., M.A Montenegro, S.C Sanyal, et al 1984 Cloning of enterotoxin gene fromAeromonas hydrophila provides conclusive evidence of production of a cytotonic enterotoxin Infect Immun 46:435^441 Chesebro, B 1998 BSE and prions: Uncertainties about the agent Science 219A2-42> 27 Cliver, D.O., R.D Ellender, and M.D Sobsey 1983 Methods for detecting viruses in foods: Background and general principles J Food Protect 46:248-259 28 Cliver, D.O (and the IFT Expert Panel on Food Safety and Nutrition) 1988 Virus transmission via foods Food Technol 42, no 10: 241-248 29 Collinge, J., and M.S Palmer, eds 1997 Prion diseases New York: Oxford University Press 30 Cromeans,T.L.,O.VNainan,andH.S.Margolis 1997 Detection of hepatitis A virus RNA in oyster meat Appl Environ Microbiol 63:2460-2463 31 Cukor, G., and N.R Blacklow 1984 Human viral gastroenteritis Microbiol Rev 48:157-179 32 DiGirolamo, R., J Liston, and J.R Matches 1970 Survival of virus in chilled, frozen, and processed oysters Appl Microbiol 20:58-63 33 Dix, A.B., and L.-A Jaykus 1998 Virion concentration method for the detection of human enteric viruses in extracts of hard-shelled clams J Food Protect 61:458-465 34 Dowell, S.F., C Groves, K.B Kirkland, et al 1995 A multistate outbreak of oyster-associated gastroenteritis: Implications for interstate tracing of contaminated shellfish J Infect Dis 171:1497-1503 35 Eyles, M.J., G.R Davey, and EJ Huntley 1981 Demonstration of viral contamination of oysters responsible for an outbreak of viral gastroenteritis J Food Protect 44:294-296 36 Frank, H.A., D.H Yoshinaga, and L-P Wu 1983 Nomograph for estimating histamine formation in skipjack tuna at elevated temperatures Mar Fish Rev 45:40-44 37 Fugate, KJ., D.O Cliver, and M.T Hatch 1975 Enteroviruses and potential bacterial indicators in Gulf Coast oysters J Milk Food Technol 38:100-104 38 Gerba, C.P., and S.M Goyal 1978 Detection and occurrence of enteric viruses in shellfish: A review J Food Protect 41:743-754 39 Gerba, C.P., S.M Goyal, R.L LaBeIIe, et al 1979 Failure of indicator bacteria to reflect the occurrence of enteroviruses in marine waters Am J Public Health 69:1116-1119 40 Gilbert, RJ., G Hobbs, G.K Murray, et al 1980 Scombrotoxic fish poisoning: Features of the first 50 incidents to be reported in Britain (1976-1979) Br Med J 281:71-72 41 Gill, TA., J.W Thompson, and S Gould 1985 Thermal resistance of paralytic shellfish poison in softshell clams J Food Protect 48:659-662 42 Hazen, T.C., CB Fliermans, R.P Hirsch, et al 1978 Prevalence and distribution of Aeromonas hydrophila in the United States Appl Environ Microbiol 36:731-738 43 Hejkal, T.W., and CP Gerba 1981 Uptake and survival of enteric viruses in the blue crab, Callinectes sapidus Appl Environ Microbiol 41:207-211 58 Konowalchuk, J., and J.I Speirs 1975 Survival of enteric viruses on fresh fruit J Milk Food Technol 38:598-600 44 Herrmann, J.E., and D.O Cliver 1973 Enterovirus persistence in sausage and ground beef J Milk Food Technol 36:426-428 59 Koo, D., K Maloney, and R Tauxe 1996 Epidemiology of diarrheal disease outbreaks on cruise ships, 1986 through 1993 JAMA 275:545-547 60 Kostenbader, K.D., Jr., and D.O Cliver 1977 Quest for viruses associated with our food supply J Food ScL 42:1253-1257, 1268 61 Kuritsky, J.N., M.T Osterholm, J.A Korlath, et al 1985 A statewide assessment of the role of Norwalk virus in outbreaks of food-borne gastroenteritis J Infect Dis 151:568 45 Hopkins, R.S., G.B Gaspard, KP Williams, Jr., et al 1984 A community waterborne gastroenteritis outbreak: Evidence for rotavirus as the agent Am J Public Health 74:263-265 46 Hudson, S.H., and W.D Brown 1978 Histamine (?) toxicity from fish products Adv Food Res 24: 113-154 47 Hwang, D.-E, S.-H Chang, C-Y Shiau, et al 1995 Biogenic amines in the flesh of sailfish (Istiophorus platypterus) responsible for scombroid poisoning J Food ScL 60:926-928 48 Jaykus, L.-A., R de Leon, and M.D Sobsey 1996 A virion concentration method for detection of human enteric viruses in oysters by PCR and oligoprobe hybridization Appl Environ Microbiol 62:2074-2080 49 Kanai, Y., H Hayashidani, K.-L Kaneko, et al 1997 Occurrence of zoonotic bacteria in retail game meat in Japan with special reference to Erysipelothrix J Food Protect 60:328-331 50 Kaper, J.B., H Lockman, R.R Colwell, et al 1981 Aeromonas hydrophila: Ecology and toxigenicity on isolates from an estuary J Appl Bacteriol 50: 359-377 51 Kaplan, XE., G.W Gary, R.C Baron, et al 1982 Epidemiology of Norwalk gastroenteritis and the role of Norwalk virus in outbreaks of acute nonbacterial gastroenteritis Ann Intern Med 96:756-761 52 Kaplan, J.E., R Feldman, D.S Campbell, et al 1982 The frequency of a Norwalk-like pattern of illness in outbreaks of acute gastroenteritis Am J Public Health 72:1329-1332 53 Keswick, B.H., T.K Satterwhite, P C Johnson, et al 1985 Inactivation of Norwalk virus in drinking water by chlorine Appl Environ Microbiol 50:261-264 62 Landry, E.F., J.M Vaughn, TJ Vicale, et al 1982 Inefficient accumulation of low levels of monodispersed and feces-associated poliovirus in oysters Appl Environ Microbiol 44:1362-1369 63 Larkin, E.P 1981 Food contaminants—viruses J Food Protect 44:320-325 64 Le Guyader, F., EH Neill, M.K Estes, et al 1996 Detection and analysis of a small round-structured virus strain in oysters implicated in an outbreak of acute gastroenteritis Appl Environ Microbiol 62:4268-4272 65 Leira, F.J., J.M Vieites, L.M Botana, et al 1998 Domoic acid levels of naturally contaminated scallops as affected by canning J Food ScL 63: 1081-1083 66 McFarren, E.F., M.L Shafer, XE Campbell, et al 1960 Public health significance of paralytic shellfish poison Adv Food Res 10:135-179 67 McKercher, PD., W.R Hess, and F Hamdy 1978 Residual viruses in pork products Appl Environ Microbiol 35:142-145 68 Miller, M.L., and XA Koburger 1985 Plesiomonas shigelloides: An opportunistic food and waterborne pathogen J Food Protect 48:449^*57 69 Moncrief, XS., R Obiso, Jr., L.A Barroso, et al 1995 The enterotoxin of Bacteroides fragilis is a metalloprotease Infect Immun 63:175-181 54 Klipstein, F.A., and R.F Engert 1976 Purification and properties of Klebsiella pneumoniae heat-stable enterotoxin Infect Immun 13:373-381 70 Murphy, A.M., G.S Grobmann, PJ Christopher, et al 1979 An Australia-wide outbreak of gastroenteritis from oysters caused by Norwalk virus Med J Austr 2:329-333 55 Klipstein, F.A., and R.F Engert 1976 Partial purification and properties of Enterobacter cloacae heatstable enterotoxin Infect Immun 13:1307-1314 71 Nakazawa, H., H Hayashidani, X Higashi, et al 1998 Occurrence of Erysipelothrix spp in broiler chickens at an abattoir J Food Protect 61:907-909 56 Kohn, M.A., T.A Farley, T Ando, et al 1995 An outbreak of Norwalk virus gastroenteritis associated with eating raw oysters JAMA 273:466-471 72 Nakazawa, H., H Hayashidani, X Higashi, et al 1998 Occurrence of Erysipelothrix spp in chicken meat parts from a processing plant J Food Protect 61:1207-1209 57 Konowalchuk, 1, and J.I Speirs 1975 Survival of enteric viruses on fresh vegetables J Milk Food Technol 38:469-472 73 Namdari, H., and EJ Bottone 1990 Cytotoxin and enterotoxin production as factors delineating 74 75 76 77 enteropathogenicity of Aeromonas caviae J CHn Microbiol 28:1796-1798 Niu, M.T., L.B Plish, B.H Robertson, et al 1992 Multistate outbreak of hepatitis A associated with frozen strawberries J Infect Dis 166:518-524 Niven, CK, Jr., M.B Jeffrey, and D.A Corlett, Jr 1981 Differential plating medium for quantitative detection of histamine-producing bacteria Appl Environ Microbiol 41:321—322 Obiso, R.J., Jr., D.M Lyerly, R.L Van Tassell, et al 1995 Proteolytic activity of the Bacteroides fragilis enterotoxin causes fluid secretion and intestinal damage in vivo Infect Immun 63:3820-3826 Omura, Y., RJ Price, and H.S Olcott 1978 Histamine-forming bacteria isolated from spoiled shipjack tuna and jack mackerel J Food ScL 43:1779-1781 78 Palumbo, S.A., M.M Bencivengo, B Del Corral, et al 1989 Characterization of the Aeromonas hydrophila group isolated from retail foods of animal origin J CUn Microbiol 27:854-859 87 Sanyal, S C , S J Singh, and R C Sen 1975 Enteropathogenicity of Aeromonas hydrophila and Plesiomonas shigelloides J Med Microbiol 8:195-198 88 Shiono, H., H Hayashidani, K.-I Kaneko, et al 1990 Occurrence of Erysipelothrix rhusiopathiae in retail raw pork J Food Protect 53:856-858 89 Sullivan, R., R.M Marnell, E.P Larkin, et al 1975 Inactivation of poliovirus and coxsackievirus B-2 in broiled hamburgers J Milk Food Technol 38:473^475 90 Takahashi,T., T Fujisawa, Y Tamura, et al 1992 DNA relatedness among Erysipelothrix rhusiopathiae strains representing all twenty-three serovars and Erysipelothrix tonsillarum Int J System Bacteriol 91 Taylor, D.M 1998 Inactivation of the BSE agent J Food Saf 18:265-274 92 Taylor, S.L., L.S Guthertz, M Leatherwood, et al 1979 Histamine production by Klebsiella pneumoniae and an incident of scombroid fish poisoning Appl Environ Microbiol 37:274—278 79 Paul, R., A Siitonen, and P Karkkainen 1990 Plesiomonas shigelloides bacteremia in a healthy girl with mild gastroenteritis J CHn Microbiol 28: 1445-1446 93 Taylor, S.L., TJ Keefe, E.S Windham, et al 1982 Outbreak of histamine poisoning associated with consumption of Swiss cheese J Food Protect 45: 455-457 80 Perl, T.M., L Bedard, T Kotsatsky, et al 1990 An outbreak of toxic encephalopathy caused by eating mussels contaminated with domoic acid N Engl J Med 322:1775-1780 94 Ternstrom, A., and G Molin 1987 Incidence of potential pathogens on raw pork, beef and chicken in Sweden, with special reference to Erysipelothrix rhusiopathiae J Food Protect 50:141-146 81 Pier, G.B., S.H Madin, and S Al-Nakeeb 1978 Isolation and characterization of a second isolate of Streptococcus iniae Int J System Bacteriol 28:311—314 95 Traore, O., C Arnal, B Mignotte, et al 1998 Reverse transcriptase PCR detection of astrovirus, hepatitis A virus, and poliovirus in experimentally contaminated mussels: Comparison of several extraction and concentration methods Appl Environ Microbiol 64:3118-3122 82 Portnoy, B.L., PA Mackowiak, CT Caraway, et al 1975 Oyster-associated hepatitis: Failure of shellfish certification programs to prevent outbreaks JAMA 233:1065-1068 83 Rodriguez-Jerez, J.J., E.I Lopez-Sabater, A.X RoigSagues, et al 1994 Histamine, cadaverine and putrescine forming bacteria from ripened Spanish semipreserved anchovies J Food Sci 59:998-1001 84 Rose, J.M., CW Houston, D.H Coppenhaver, et al 1989 Purification and chemical characterization of a cholera toxin-cross-reactive cytolytic enterotoxin produced by a human isolate of Aeromonas hydrophila Infect Immun 57:1165-1169 85 Rouf, M.A., and M.M Rigney 1971 Growth temperatures and temperature characteristics of Aeromonas Appl Microbiol 22:503-506 86 Sabota,J.M.,W.L.Hoppes,J.R.Ziegler,Jr.,etal 1998 A new variant of food poisoning: Enteroinvasive Klebsiella pneumoniae and Escherichia coli sepsis from a contaminated hamburger Am J Gastroenterol 93:118-119 96 Tsukamoto, T., Y Konoshita, T Shimada, et al 1978 Two epidemics of diarrhoeal disease possibly caused by Plesiomonas shigelloides J Hyg 80:275-280 97 Twedt, R.M., and B.K Boutin 1979 Potential public health significance of non-Escherichia coli coliforms in food J Food Protect 42:161-163 98 Van Damme, L.R., and J Vandepitte 1980 Frequent isolation of Edwardsiella tarda and Plesiomonas shigelloides from healthy Zairese freshwater fish: A possible source of sporadic diarrhea in the tropics Appl Environ Microbiol 39:475-479 99 Vogel, G 1997 Prusiner recognized for once-heretical prion theory Science 278:214 100 Wait, D.A., CR Hackney, RJ Carrick, et al 1983 Enteric bacterial and viral pathogens and indicator bacteria in hard shell clams J Food Protect 46: 493-496 101 Wei, C L , C-M Chen, J.A Koburger, et al 1990 Bacterial growth and histamine production on vacuum packaged tuna J Food Sci 55:59-63 102 Williams, N 1997 New studies affirm BSE-human link Science 278:31 103 Xu, X.-J., M.R Ferguson, VL Popov, et al 1998 Role of cytotoxic enterotoxin in Aeromonas-mediated infections: Development of transposon and isogenic mutants Infect Immun 66:3501-3509 104 Yoshinaga, D.R., and H.A Frank 1982 Histamineproducing bacteria in decomposing shipjack tuna (Katsuwonus pelamis) Appl Environ Microbiol 44:447-452 105 Zajc-Satler, J., A.Z Dragav, and M Kumelj 1972 Morphological and biochemical studies of strains of Plesiomonas shigelloides isolated from clinical sources ZbL Baktr Hyg Abt OHg A 219:514-521 Relationships of Common Foodborne Genera of Gram-Negative Bacteria Gram-negative bacteria Pigmented Nonpigmented Oxidase Lactose i Negative Positive Negative Alteromonas (most) Chromobacterium Flavobacterium Photobacterium Vibrio Xanthomonas Erwinia Pantoea Photobacterium Serratia Xanthomonas Oxidase Oxidase Positive Aeromonas Alteromonas Plesiomonas Shewanella Note: For details, consult Bergey's Manual of Systematic Bacteriology Negative Citrobacter Enterobacter Escherichia Klebsiella Pantoea Salmonella Serratia Yersinia Positive Aeromonas Alcaligenes Alteromonas Arcobacter Campylobacter Moraxella Plesiomonas Pseudomonas Psychrobacter Vibrio Negative Acetobacter Acinetobacter Burkholderia Gluconobacter Hafnia Pantoea Proteus Providencia Pseudomonas Salmonella Serratia Shigella Yersinia APPENDIX A Positive APPENDIX B Relationships of Common Foodborne Genera of Gram-Positive Bacteria Gram-positive bacteria Endospores Present Absent Aerobes Anaerobes A licyclobacillus Bacillus Paenibacillus Sporolactobacillus Clostridium Catalase Positive Negative Arthrobacter Brevibacterium Brochothrix Corynebacterium Kocuria Kurthia Listeria Micrococcus Planococcus Propionibacterium Staphylococcus Bifidobacterium Carnobacterium Enterococcus Erysipelothrix Lactococcus Lactobacillus Lactosphera Leuconostoc Oenococcus Pediococcus Streptococcus Tetragenococcus Vagococcus Weissella Note: For details, consult Bergey's Manual of Systematic Bacteriology APPENDIX C Biofilms The importance of biofilms to food safety and spoilage warrants a better understanding of their biology, structure, and function Reviews of the early history of our knowledge of these entities have been presented by Carpentier and Cerf,4 Costerton et al.,6 and Zottola.13 A biofilm consists of the growth of bacteria, fungi, and/or protozoa alone or in combination bound together by an extracellular matrix that is attached to a solid or firm surface Common examples include the slimy surfaces on rocks or logs in bodies of running water, dental plaques, and the slime layer on refrigerator-spoiled fresh meats and poultry They form on surfaces in large part because nutrients are found in higher concentrations than in the open liquid In laboratory studies, surface adherence is best in rich media.2 Attachment is facilitated by the microbial excretion of an exopolysaccharide matrix sometimes referred to as a glycocalyx Microcolonies form within this microenvironment in a manner that leads to microbial communities that allow water channels to form between and around the microcolonies The latter has been likened to a primitive circulatory system where nutrients are brought in and toxic by-products are carried out Microbial cells in liquids that are not in a biofilm are in a planktonic (free floating) state From the standpoint of food safety and spoilage, biofilms are important because of their accumulation on foods, food utensils, and surfaces; and because of the difficulty of their removal While under natural conditions biofilms tend to be composed of mixed cultures, pure culture systems are often used in laboratory studies Some of the solid surfaces employed to study foodborne bacteria include floor sealant, glass slides, nylon, polycarbonate, polypropylene, rubber, stainless steel, and Teflon Glass and stainless steel are widely used From the many studies that have been carried out on biofilm formation in food environments, the following summaries can be made: • Although biofilm formation by single cultures in rich media (e.g., tryptic soy broth) may be evident after 24 hours when appropriate growth temperatures are used, three to four days or more are necessary for maximum development On glass slides in a culture medium for three days at 24°C, Listeria monocytogenes grew to about log10 6-7/cm2.1 • Microorganisms in biofilms are considerably more resistant to removal by commonly used cleaning and sanitizing agents • In general, microorganisms in biofilms are more difficult to destroy by lethal agents, i.e., they are protected by the biofilm matrix.57 • The attachment of a given pathogen to surfaces may be aided by the formation of a mixed-culture biofilm.3912 • Microorganisms in biofilms may exhibit different physiologic reactions than planktonic forms, and the biofilm may contain cells in the viable but nonculturable state.45 • The use of cleansers and sanitizers in combination rather than singly appears to be more effective in removing biofilm growth.111 • Not all strains of the same species are equally capable of initiating biofilm formation;10 and surface attachment and biofilm development are different processes.8 REFERENCES Arizcun, C , et al 1998 Effect of several decontamination procedures on Listeria monocytogenes growing in biofilms J Food Protect 61:731-734 Blackman, LC, and XF Frank 1996 Growth of Listeria monocytogenes as a biofilm on various food-processing surfaces J Food Protect 59:827-831 Buswell, CM., et al 1998 Extended survival and persistence of Campylobacter spp in water and aquatic biofilms and their detection by immunofluorescentantibody and -rRNA staining Appl Environ Microbiol 64:733-741 Carpentier, B., and O Cerf 1993 Biofilms and their consequences, with particular reference to hygiene in the food industry J Appl Bacteriol 75:499-511 Chumkhunthod, R, et al 1998 Rapid monitoring method to assess efficacy of sanitizers against Pseudomonas putida biofilms J Food Protect 61:1043-1046 Costerton, J.W., et al 1994 Biofilms, the customized microniche J Bacteriol 176:2137-2142 Frank, I F , and R.A Koffi 1990 Surface-adherent growth of Listeria monocytogenes is associated with 10 11 12 13 increased resistance to surfactant sanitizers and heat J Food Protect 53:550-554 Kim, K Y., and J.F Frank 1995 Effect of nutrients on biofilm formation by Listeria monocytogenes on stainless steel J Food Protect 58:24-28 Leriche, V, and B Carpentier 1995 Viable but nonculturable Salmonella typhimurium in single- and binary-species biofilms in response to chlorine treatment J Food Protect 58:1186-1191 Michiels, CW., et al 1997 Molecular and metabolic typing of resident and transient fluorescent pseudomonad flora from a meat mincer J Food Protect 60:1515-1519 Oh, D.-H., and D.L Marshall 1996 Monolaurin and acetic acid inactivation of Listeria monocytogenes attached to stainless steel J Food Protect 59:249-252 Sasahara, K.C., and E.A Zottola 1993 Biofilm formation by Listeria monocytogenes utilizes a primary colonizing microorganism in flowing systems J Food Protect 56:1022-1028 Zottola, E.A 1994 Microbial attachment and biofilm formation: A new problem for the food industry? Food Technol 48(7):107-114 APPENDIX D Grouping of the Gram-Negative Asporogenous Rods, Polar-Flagellate, Oxidase Positive, and Not Sensitive to 2.5 IU Penicillin, on the Results of Four Other Tests Behavior in the test of Hugh and Leifson Oxidative Green fluorescent diffusible pigment No diffusible pigment Alkaline No action Fermentative No diffusible pigment No diffusible pigment No diffusible pigment Acid, no gas in Acid, much glucose (some gas in glucose at 20° strains form traces of gas) Pseudomonas, Group I Pseudomonas, Group II Pseudomonas, Group III Pseudomonas, Group IV Sensitive to the pteridine compound (0/129) Insensitive to the pteridine compound (O/129) Vibrio Aeromonas Source: After J.M Shewan, G Hobbs, and W Hodgkiss, 1960 A determinative scheme for the identification of certain genera of gram-negative bacteria, with special reference to the Pseudomonadaceae J Appl Bacteriol 23:379—390 ... James M (James Monroe), 1927— Modern food microbiology / James M Jay. 6th ed p cm — (Aspen food science text series) Includes bibliographical references and index ISBN 0-8 34 2-1 671-X Food Microbiology. .. group Editorial Services: Joan Sesma Library of Congress Catalog Card Number: 9 9-0 54735 ISBN: 0-8 34 2-1 671-X Printed in the United States of America Preface The sixth edition of Modern Food Microbiology, ... detailed review of the history of food microbiology has been presented by Hartman Hartman, P.A 1997 The evolution of food microbiology In Food Microbiology Fundamentals and Frontiers, eds M.P Doyle,