Beatriz Quinones
United States Department of Agriculture-Agricultural Research Service, USA
Title: Virulence and antimicrobial resistance profiles of Shiga toxin-producing Escherichia coli O157 and non-O157 recovered from domestic farm animals in rural communities in Northwestern Mexico
Biography
Biography: Beatriz Quinones
Abstract
Shiga toxin-producing Escherichia coli (STEC) are zoonotic enteric pathogens associated with human gastroenteritis worldwide.
Our study characterized the genotypic diversity and virulence profiles of O157 and non-O157 STEC strains, recovered from
domestic animals in the agricultural Culiacan Valley in Northwestern Mexico. By using a selective enrichment and isolation protocol,
serotype O157:H7 isolates were identified in 40% (26/65) of the recovered isolates from cattle, sheep and chicken feces. The clinicallyrelevant
non-O157 serotypes O8:H19, O75:H8, O111:H8 and O146:H21 represented 35.4% (23/65) of the isolates, mostly from sheep.
Analysis of the allelic diversity indicated that the O157:H7 isolates were highly related but a greater genotypic diversity was observed
in the non-O157 isolates. Genotyping assays revealed the presence of virulence genes coding for adhesins, cytotoxins, effectors and
Shiga toxin (Stx) subtypes in the tested strains. To examine the relative toxicities of the STEC strains, a fluorescent Vero cell based
assay was employed to measure the inhibition of protein synthesis by Stx. Non-O157 strains with serotypes O8:H19 O75:H8 and
O146:H8 were found to have an enhanced ability to inhibit protein synthesis in Vero cells while a reduced cytotoxicity was observed
for all O157:H7 strains. The STEC strains exhibited antimicrobial resistance to aminoglycosides, tetracyclines, cephalosporins and
penicillin which are commonly used in Mexico. In conclusion, zoonotic STEC with virulent genotypes are present in animals on
small farms in the Culiacan Valley and these findings emphasize the need for the development of control measures and surveillance
of antimicrobial resistance in an important agricultural region in Northwestern Mexico.