An agclr plate ~~~et~~o~ for the diagrzosis of intestinal strorzgyloidiasis was compared %o%kestandard forl~la~i~-e%ky~ acetate concentration method A total of 13 of 225 patients witk eosino~~i~jahad positive s%ookforstroizg$oides !arzla hy agar plate compared to six of 225 by tke fou~nalin-etlzylacetate Strongyloides stercoralis ~~et~zo~ (P = 0455) Mine positive stool s~ec~?i?ei~s by tke agar plate metkod were tes%edby tke Baermann %ec~~i~~qMe~ and five wue positiw Tke agar plate metkod is a sensiti-oe and eficier~t tecknique for the diagnosis of s%r~~gytQidias~s is asp ende Southeastern United States (Berk et al., 1987) In corn-promised hosts and patients om steroids, the organism has the potential to cause fatal disse fections (Filho, 1978; Igra-Siegman et al., 1981; Scowden et al., 1978) Hence, detection of larva in stools is of the utmost importance oratory diagnosis of strongyloidiasis is very difficult because of the often scant and i~te~itte~t excretion of larva (Neva, 1986; Pelletier et al., 1988; Lima et al., 1961; Filho, 1978; Goka et al., 1990) The formalin-ethyl acetate concentration method, although commonly employed, has a low yield and is labor intensive Welletier et al., 1988) The Baermann technique may be more sensitive but is even more labor intensive and impractical in most commercial laboratories (Lima et al., 1961, Filho, 1978) Our study used an agar plate method first described From the Department of Internal Medicine, East Tennessee State University, College of Medicine, Laboratory Service, Veterans Affairs Medical Center, Mountain I+me, Tennessee Address reprilzf reqwsts to Dr S.A Sdazar, Baptist Medical Building, 631 R.B Wilson Drive, Huntingdon, TN 38344, USA Received July 1995; revised and accepted 30 October 1995 DIAGN MICROBIOL INFECT DIS 1995;23:141-145 1995 Elsevier Science inc 655 Avenue of the Americas, New York, NY 10010 stools that were the Baermann technique.) ish with beef extract agar beef extract, 1.0% peptone, 0.5% NaCB, and ‘B5% agar) was introduced into a 150 x 15-mm Pe The space between the Petri dishes was fill 50% aqueous glycerin solution to 0732~5593/95/$15.00 SSDI 0732-8893(95)00247-2 contamination We placed 2-4 g of stool in the center of the beef extract-filled Petri dish and stored it at room temperature The plates were examined through a dissecting microscope (Fisher Stereomaster, Atlanta, x60) every 24 h, for a total of 72 h A positive test was defined as visualization of motile strongyloides larval forms on agar using the dissecting microscope Larval furrows were also seen in all positive cases Formalin-preserved fecal suspension (10 ml) was strained into a 15-ml conical centrifuge tube The suspension was centrifuged at 650 x g for Then, 10% buffered formalin was added to the sediment and vortexed thoroughly Next, ml of ethyl acetate was added, and the tube was stoppered and again vortexed thoroughly The solution was centrifuged at 450-500 x g for Four layers resulted: The top three layers were discarded and the bottom (sediment) layer was examined Wet mounts were prepared by a standard method aemann Technique A 6-inch funnel with rubber tubing and a pinch clamp attached at the bottom was filled with warm FIGURE1 Larval furrows seen in agar plate water A piece of wire gauze and two layers of cotton gauze were placed on the to imately 100 g of stool was warm water was added to appar? FUSwas allowed to stand for h, the pin clamp was opened and 10.0 ml of was collected in a centrifuge habe tion, a drop of the sediment was of Lugol’s iodine and examined (x10) for larvae We collected 225 stools the agar plate method a n-ethyl acetate method The a cted all but one of the positive results from the formallyether method The fo~rna~i~-etcher method miss eight positive results from the agar plate meth The agar plate method’s positivity was significantly different from t method proportion (2.7%), with p = correlated proportions ( sner, 1995) Positive stools larval furrows in agar by agar plate showed (Figure 1) and the motile larva ~~~~~re2) Nine positive stool specimens underwent examination by the Motile Strongy~oides larva seen in agar plate (dissecting microscope) Baermann technique Five of these nine samples (positive by agar) were confirmed positive by the Baermann technique One stool diagnosed as posiy ~~r~~a~~~-et~~y~ acetate was not &agnoseJ1 by the agar plate method Ckble 19 The diagnosis of strongyloidiasis can be suggested by clinical signs and symptoms, essinophilia, and EE Comparison of Methods in the Diagnosis of Strongyloidiasis Results No of Specimens Method Examined No Positive Agar plate Formalirt-ethyl acetate Baermann 225 13 225 9b 6” “One positive sample was negative by the agar plate method bAMnine were known positive samples serologic studies, tnt demons niques in the detection of lowloides infection has been well et al., 1988; Jones, 195fV As earl ied 100 hospitalized male smear, concentratlon techni rates A total of 20 patients wit aspirates could not be shov stools, even though more than five stools from eat patient were examined The value of repeated stool examinations for increasing the yield of diagnosis has been suggested Grove (1980) increased of diagnosis through direct stool micros 68% to 84% by repeating stool examinati more times PeUetier (1984) noted an i agnostic yield in the proportion of time ining the stool samples through the fo method e was able to diagnose 50% after 1.7 h at microscopy, a yield which increased to 100% after 10 h at microscopy per case Htis a possible that more rapid centrifugation meth may improve yield in the formalin-ether method, but we have no data on this issue The Baermann technique, which takes advantage of the hydrotropism and thermotropism of strongyloides, is believed to be a more sensitive method for the diagnosis of strongyloidiasis (Filho, 1978; Genta, 1986) Lima et al (1958) fo*und the Baermann technique to be more sensitive than concentration methods In 1988, Arakaki (1988) described the agar plate technique for the detection of strongyloidiasis Ne and co-workers in Okinawa, Japan, had noted a network of furrows left by S sterconrlison the surface of the agar plate media Arakaki compared the agar plate method to formalin-ether and test-tube culture techniques Among 246 samples examined by the agar plate method and formalin-ether technique, 14 were positive using the agar plate method, whereas only two were positive by the formalin-ether technique other studies have substantiated these findings (Arakaki, 1990; Koga et al., 1990) Koga et al (1990)examined 148 specimens and found 18 cases to be positive by the agar plate method and four cases by the formalin-ether method Furthermore, Arakaki et al (1990)noted the agar plate method to be two to four times as efficient as the formalin-ether concentration method in the detection of strongyloidiasis We are unaware of any trials comparing the formalin-ethyl acetate, agar plate, and Baermann techniques The agar plate method has not been previously studied in North America, where endemic larval counts may be different We found the agar plate method to be much more sensitive than the standard method Patients noted to be positive using the agar plate method but negative by the formalinether method had repeat stool samples submitted Arakakl T, Hasegawa H, Asato R, et al (1988) A new method to detect Strongyloides stercoralis from human stool Jpn J Trap Med Hyg 16~11-17 Arakaki T, Iwanaga M, Kinjo F, et al (1990) Efficacy of agar-plate culture in detection of Strongyloides stercorulis infection J Parasitol 76425-428 samples and fields One o itive results one s e was not received until the agar medium have been well (1990) All were seen in our labor reentering the stool There were when only furrows were noted the stool before a motile larva der the dissecting scope was very small (~5 min/ plate) The superiority of the agar late method is striking In addition to the improved ~ensitivity~ it is less time-consuming than e er the Baermann or the formalin-ethyl acetate me ds Very little technical expertise is needed, and the cost is minimal The agar plat chnique should become the method of choice for diagnosis of strongyloidiasis in the LJnited States The alrthors thank Shirley Berk, for Sechrricalassisfaiice, Christa Dison for preparation of the manuscript, and John Kalbfleischfor statisticalconsultation Goka AKJ, Rolston DDK, Mathan VI, et al (1990) Diagnosis of strongyloides and hookworm infections: comparison of faecal and duodenal fluid microscopy Trans R Sor Trap Med Hyg 84:829-831 Grove DI (1980) Strongyloidiasis in allied ex-prisoners of war in south-east Asia Br Med J Mar 280~598601 Berk SL, Verghese A, Alvarez S, et al (1987) Clinical and epidemiologic features of strongyloidiasis: a prospective study in rural Tennessee Arch Intern Med 147:12571261 Igra-Siegman Y, Kapila R, Sen I’, et al (1981) Syndrome of hyperinfection with Strongyloides stevcarn!is.Rev Infect Dis X397-407 Filho EC (197% Strongyloidiasis ChinGastroenferol 7:1792QO Jones CA (1950) Clinical studies in human strongyloidiasis I Semeiology Gastroenterology 16~743-756 Genta RM (1989) Global prevalence of strongyloidiasis: Koga K, Kasuya S, Khamboonruang C (1990) An evaluation of the agar plate method for the detection of Strongyloides stercoralis in northern Thailand Trop Med Hyg 93:183-188 Genta RM (1986) Strongyloidiasis In lmmtrnodiagnosis of Parasitic Diseases Eds, KWWalls and PM Sehantz New Lima JP, Delgado PG (19611 Diagnosis of strongyloidiasis: importance of Baermann’s method Am Dig Dis 6:899904 critical review with epidemiologic insights into the prevention of disseminated disease Rev Infect Dis 11:755767 York: Academic Press, pp 183-198 ... agar plate method a n-ethyl acetate method The a cted all but one of the positive results from the formallyether method The fo~rna~i~-etcher method miss eight positive results from the agar plate. .. the surface of the agar plate media Arakaki compared the agar plate method to formalin-ether and test-tube culture techniques Among 246 samples examined by the agar plate method and formalin-ether... different We found the agar plate method to be much more sensitive than the standard method Patients noted to be positive using the agar plate method but negative by the formalinether method had repeat