Abstract
Shigatoxigenic Escherichia coli (STEC) strains are worldwide zoonotic pathogen responsible for different cases of human disease including hemolytic uremic syndrome (HUS). Transmission of STEC to humans occurs through the consumption of food and water contaminated by faeces of carriers and by person-to-person contact. The objective of this study was two-fold: (1) to investigate whether synanthropic rodents are possible reservoirs of STEC in the urban area and (2) whether a particular genus out of synanthropic rodent is the principal carrier of STEC. One hundred and forty-five rodents were captured in Buenos Aires City. Screening for stx1/stx2 and rfbO157 was done by PCR from the confluence zone. STEC isolates were further characterized with biochemical tests by standard methods. Additional virulence factors (eae, ehxA, and saa) were also determined by PCR. Forty-one of the rodents were necropsied and sample of kidney and small and large intestine were taken for histopathological diagnosis. The samples sections were stained with hematoxylin-eosin, and observed by light microscopy to evaluate the systemic involvement of these species in natural infections. STEC was isolated from seven out of 27 suspect animals at screening. The following genotypes were found in the STEC strains: stx1/stx2/ehxA (1), stx2 (4), stx2/ehxA (1), stx2/ehxA/eae (1). Neither gross nor microscopic lesions compatible with those produced by Shiga toxin were observed in the studied organs of necropsied rodents. The bivariate analysis including the 145 rodent's data showed that the isolation of STEC is associated positively to Rattus genus. This synanthropic species may play a role in the transmissibility of the agent thus being a risk to the susceptible population. Their control should be included specifically in actions to dismiss the contamination of food and water by STEC in the urban area, as additional strategies for epidemiological control.
Highlights
Shigatoxigenic Escherichia coli (STEC) strains are a worldwide zoonotic pathogen responsible for different cases of human disease including diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome (HUS) (Karmali, 1989).Unlike other commensal E. coli strains, STEC strains have several virulence genes which permit the evaluation of its pathogenic nature in the laboratory (Paton and Paton, 1998a, 2002)
Rodents captured belonged to the following species: Deltamys kempi (n:4), Mus musculus (n:66), Oligoryzomys flavescens (n:16), Rattus norvegicus (n:31), Rattus rattus (n:28)
All the isolates were detected as non-O157 strains by PCR
Summary
Unlike other commensal E. coli strains, STEC strains have several virulence genes which permit the evaluation of its pathogenic nature in the laboratory (stx, stx, eae, ehxA, saa) (Paton and Paton, 1998a, 2002). These strains may be screened by PCR of stx genes in cultured bacteriological samples and subsequent isolation of colonies stx+. Over years cattle has been involved as the principal reservoir of STEC, isolated strains are partially similar to those which have impact on public health (Boerlin et al, 1999; Rosser et al, 2008)
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