IDENTIFICACIÓN DE Escherichia coli DIARREOGÉNICAS EN MUESTRAS CLÍNICAS (HECES) Y DE ALIMENTOS EN EL ESTADO DE SINALOA

Abstract

Contaminated food is the principal vehicle for transmission of pathogenic strains of diarrheagenic Escherichia coli (DEC) to humans. This study reports the epidemiological surveillance of Escherichia coli strains in 5162 food service establishment and retail food samples, consisting of Ice and Water (n=1596), restaurant-made food or street food (n=1594), dairy products (n=669), fish and seafood (n=656), meat and meat products (n=647). Samples were collected in 10 municipalities of Sinaloa State located at the NorthWest of Mexico during January- December in 2007 and 2008. Materials and Methods. E. coli strains were isolates by conventional methods of food microbiology. To detect DEC strains, multiplex PCR and single PCR reactions were performed that amplified genes of recognized virulence factors of enteroaggregative (EAEC; aggr and aafII genes), enteroinvasive (EIEC; Ipah and VirF), enteropathogenic (EPEC Typical; eae and bfp or EPEC Atypical; eae), enterotoxigenic (ETEC; st y lt), diffusely adherent (DAEC; daaE) or shiga toxin-producing (STEC; stx1/stx2 or EHEC; eae, stx1/stx2, or hlya) E. coli strains. For this study were designed primers for the category of EPEC (eae and bfp) and EHEC (stx1/stx2) with oligo software version 7. Results. Bacteriological analysis detected that 8.0% (412/5162) of the food samples were contaminated with E. coli strains, with non-permissive levels for human consumption. Of those, 13.2% corresponded to DEC strains (54/412), as detected by multiplex PCR. The diarrheagenic category most frequently isolated was EPEC with 83% (45/54; 9 typical and 36 atypical) followed by STEC (9%; 5/54), ETEC (4%; 2/54) and EAEC (4%; 2/54) also. None of our E. coli isolates harbored virulence genes corresponding to DAEC and EIEC. The food items most contaminated with DEC strains were dairy products, meat samples and prepared foods, although we did not find a tendency for a specific diarrheagenic category. Conclusion. We conclude that potentially pathogens DEC strains (EPEC, STEC, EAEC and ETEC pathotypes) are present (1.1%; 54/5162) in food products that are consumed, sold or/and distributed at Northwest of Mexico. Diarrheagenic Escherichia coli strains are being recognized as important clinical enteropathogens worldwide. However, it is unclear whether there are differences in age-related susceptibility to specific strains. This study aimed at investigating DEC among patients (from 3 months to 99 year old) with acute/persistent diarrhea at Northwest of Mexico during January- December in 2008 and 2009. Materials and Methods. DEC were isolated from stool samples collected from 117 patients with acute/persistent diarrhea. Fecal samples were cultured and identified according to the standard biochemical methods and three oligonucleotide primers 16E1, 16E2 and 16E3 were used to identify specifically all E. coli isolates by PCR. To detect DEC strains, multiplex PCR and single PCR reactions were performed that amplified genes of recognized virulence factors of enteroaggregative (EAEC; aggr and aafII genes), enteroinvasive (EIEC; Ipah and VirF), enteropathogenic (EPEC Typical; eae and bfp or EPEC Atypical; eae), enterotoxigenic (ETEC; st y lt), diffusely adherent (DAEC; daaE) or shiga toxinproducing (STEC; stx1/stx2 or EHEC; eae, stx1/stx2, or hlya) E. coli strains. For this study were designed primers for the category of EPEC (eae and bfp) and EHEC (stx1/stx2) with oligo software version 7. Results. Thirty-one patients (26.4%) harbored DEC (from 117). The most frequently isolated pathogen was Enteropathogen (EPEC) Escherichia coli with 42% (13/31; 8 typical and 5 atypical) followed by EAEC with 29% (9/31), ETEC with 26% (8/31) and DAEC with 3% (1/31). None of our E. coli isolates harbored virulence genes corresponding to STEC and EIEC. By the age group; EPEC typical or atypical (19.2%, 11/57) and EAEC (12%, 7/57) were more prevalent among the age group 0-2 years old. ETEC was more prevalent among the age group 11-20 (33%, 2/6) years old, followed by 6-10 (30%, 3/10) and 51-99 (18%, 2/11) years old. DAEC only was identified among the age group 3-5 years old (5%, 1/18). None of DEC isolates were identified among the age group 21-30 and 31-50 years old. The results show a high proportion of DEC among patients with acute/persistent diarrhea at Northwest of Mexico, with typical EPEC predominating.