Ramotar K, Henderson E, Szumski R, Louie T J
Department of Microbiology-Infectious Diseases, University of Calgary, Alberta, Canada.
J Clin Microbiol. 1995 May;33(5):1114-20. doi: 10.1128/jcm.33.5.1114-1120.1995.
During a 10-week period in the summer of 1990, an epidemiologic investigation of the prevalence of verotoxin (VT)-producing Escherichia coli infection was conducted in Calgary, Alberta, Canada. Consecutive stool specimens (n = 3,577) were cultured for E. coli O157:H7, and fecal filtrates were tested for free VTs (FVTs). E. coli O157:H7 was recovered from 22 specimens (0.6%), but VT was detected in 74 specimens (2.1%). Sixty-nine stool specimens positive for FVTs or E. coli O157:H7 were probed for VT genes by colony blot hybridization; 22 of 38 VT gene probe-positive isolates were non-O157:H7 E. coli organisms. Fourteen of 22 strains could not be induced to produce VT in vitro, despite the presence of FVTs in the stool sample, positivity on colony blot hybridization, positive PCR probes with the primers described by Pollard et al. (D. R. Pollard, W. M. Johnson, H. Lior, S. D. Tyler, and K. R. Rozee, J. Clin. Microbiol. 28:540-545, 1990) or Gannon et al. (V. P. Gannon, R. K. King, J. Y. Kim, and E. J. Golsteyn-Thomas, Appl. Environ. Microbiol. 58:3809-3815, 1992) (but not those described by Karch and Meyer [H. Karch and T. Meyer, J. Clin. Microbiol. 27:2751-2757, 1989]), and positive Southern blot analysis of isolates in 10 of 14 strains. The patient survey questionnaire showed that E. coli O157:H7 infection was associated with bloody diarrhea of short duration, whereas infection with other serotypes or persistence of FVT only was associated with longer-duration nonbloody diarrheal illness. We conclude that (i) detection of FVT in stools enhances the diagnosis of VT infection threefold over cultures for E. coli O157:H7, (ii) cultures for E.coli O157:H7 detect the majority of organisms of that serotype, (iii) the spectrum of disease produced by organisms of non-O157:H7 serotypes may include less severe but more protracted illness, and (iv) differences in the in vivo and in vitro expression of toxin and results of genetic probe studies highlight the need to examine control mechanisms of toxin production.
1990年夏天的10周时间里，在加拿大艾伯塔省卡尔加里市针对产志贺毒素（VT）的大肠杆菌感染患病率开展了一项流行病学调查。对连续采集的粪便标本（n = 3577）进行了大肠杆菌O157:H7培养，并对粪便滤液进行了游离VT（FVT）检测。从22份标本（0.6%）中分离出大肠杆菌O157:H7，但在74份标本（2.1%）中检测到了VT。通过菌落杂交印迹法对69份FVT或大肠杆菌O157:H7检测呈阳性的粪便标本进行了VT基因检测；38份VT基因探针检测呈阳性的分离株中，有22株为非O157:H7大肠杆菌菌株。22株菌株中有14株尽管粪便样本中存在FVT、菌落杂交印迹法呈阳性、用Pollard等人（D. R. Pollard、W. M. Johnson、H. Lior、S. D. Tyler和K. R. Rozee，《临床微生物学杂志》28:540 - 545，1990年）或Gannon等人（V. P. Gannon、R. K. King、J. Y. Kim和E. J. Golsteyn - Thomas，《应用与环境微生物学》58:3809 - 3815，1992年）（但不是Karch和Meyer所描述的引物[H. Karch和T. Meyer，《临床微生物学杂志》27:2751 - 2757，1989年]）描述的引物进行PCR探针检测呈阳性，且14株菌株中有10株的分离株Southern印迹分析呈阳性，但仍无法在体外诱导产生VT。患者调查问卷显示，大肠杆菌O157:H7感染与持续时间较短的血性腹泻相关，而其他血清型感染或仅FVT持续存在与持续时间较长的非血性腹泻疾病相关。我们得出以下结论：（i）粪便中FVT的检测比大肠杆菌O157:H7培养在VT感染诊断方面提高了三倍；（ii）大肠杆菌O157:H7培养能检测到该血清型的大多数菌株；（iii）非O157:H7血清型菌株引起的疾病谱可能包括病情较轻但病程更长的疾病；（iv）毒素在体内和体外表达的差异以及基因探针研究结果突出了研究毒素产生控制机制的必要性。
