Tracking strains across time and geography
Distinguishing endemic from epidemic disease occurrence Stratification of data to refine study designs
Distinguishing pathovars vs commensal flora or saprophytes
Identifying new modes of transmission
Studying microorganisms associated with healthcare or institutional infections Surveillance and monitoring response to intervention
Characterizing population distribution and determinants of distribution of parasitic organisms Identifying genetic basis for disease transmission
Validating microdiversity genotyping methods applied to epidemiology
Virus quasispecies population structure analysis
Identifying direction and chain of transmission
Identifying hidden social networks and transmission links
Analyzing microbiomes to study non-infectious disease epidemiology
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¢Outbreaks provide an opportunity to validate new Strain typing methods
Once validated, the same method can be applied to investigate other outbreaks and sporadic diseases ¢eWith some infectious diseases, strain typing
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¢To identify unrecognized outbreaks among what looks like sporadic (endemic) cases of disease °To identify vehicles of infection in which
conventional methods are not useful
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eA small fraction of reported cases come from
recognized outbreaks (7% in salmonellosis in the US)
¢ Identifying risk factors for sporadic infections is difficult ¢ May provide information about attributable risk
¢ May provide information about the dynamics of disease
transmission in a community
¢ transmission by a food vehicle
¢ transmission by person-to-person contact
Trang 9, : selected rural and urban counties in the US (n=378) Co et “1 JID, 1984;149:878) f : selected counties in the US (n=341) (MacDonald et al, JAMA 1987; 258:1496) 1989-1990: selected counties in the US (n=484) (Lee et al, nie 1994; eit 128)
1994-95: National Salmonella Antimicrobial Resistance Study —— (50 state and territories)
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1979-80 Salmonella antimicrobial resistance stud
S TYPHIMURIUM CARRYING A 140-Mp PLasmIpD ANTIBIOGRAM No, AKSSuTCNCEG ai AKSSuTCN AKSSUTCE ASSUTCE AKSSuT 1 ASSuT KSSuT AKST AST A eo Colo oi op Ore = Oe In ` `) Fe = STATE TX MA FL.PA CT.SC C0,FL.,6A.MA.,NY,OH.PA,RI.TX iP, NJ.NY iP, Mele RI
A-AMPICILLIN C-CHLORAMPHENICOL, CE-CEPHALOTHIN G-GENTAMICIN K-KANAMYCIN N-NITROFURANTOIN
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PLASMID PROFILES OF SELECTED MULTIRESISTANT S, TYPHIMURIUM STRAINS
1979-80 ANTIMICROBIAL RESISTANCE STUDY, UNITED STATES
Trang 15PLASMID PROFILES OF S, TYPHIMURIUM STRAINS RESISTANT To
Trang 16PLASMID PROFILES OF MULTIRESISTANT S TYPHIMURIUM STRAINS
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¢Human infections with drug-resistant Salmonella have animal origin
¢ Measures of incidence and prevalence of drug
resistance in a community is dependent on the number
of drug-resistant clones that happen to be circulating in that community at the time of the study
elt is meaningless to discuss increasing or decreasing
prevalence of drug-resistance without specifying the clonal composition of the isolates tested for
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Trang 23Salmonellosis in New Jersey and Pennsylvania, June-Aug, 1981
0 Background:
e Salmonellosis outbreak at a wedding in New Jersey across the river from Philadelphia, Pennsylvania
e Salmonellosis outbreak in a Eye Hospital in Philadelphia
® Precooked roast beef implicated as the vehicle for both outbreaks ® Precooked roast beef prepared
at a meat processing plant in
Trang 24Question: How many cases of salmonellosis
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chr
S newport from outbreaks, June-
Trang 26AGAROSE GEL ELECTROPHORESIS OF S NEWPORT FROM ISOLATED CASES IN
PENNSYLVANIA AND NEW JERSEY, JUNE-AUGUST 1981
ASB SC Ds (ES SEG
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Period of isolation Number of isolates analyzed Jan-March, 1981 June-August, 1931* Nov 1981-Jan 1982 June 1981-Feb 1982 Total Pennsylvania 14 Pennsylvania, New Jersey 33 Pennsylvania, New Jersey 12
Georgia, Michigan, Texas 45 104
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Period Total number Number analyzed RB associated
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Association between roast beef consumption
and plasmid profile in 19 patients with
| Salmonella newport infections,
New Jersey & Pennsylvania, Summer 1981
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® Contaminated food product was introduced into a community © Increased prevalence ot salmonellosis was found to be associated
with one predominant strain of Salmonella
eA single tood product was found to be responsible for nearly 40% of sporadic salmonellosis cases in NJ and PA in the summer of
1981
e After recall of the implicated food item, salmonellosis caused by
the epidemic clone continued in the community by person-to-