Serotypes, virulence genes profiles and antimicrobial resistance patterns of Escherichia coli recovered from feces of healthy lambs in Mexico

Abstract

A B S T R A C THealthy lambs are one of the major reservoirs of Shiga toxin-producing Escherichia coli (STEC) and it is known as the cause of foodborne diseases (FBD). The work objective is to characterize (STEC) isolates obtained from rectal swabs of healthy lambs herds, a total of 183 samples were obtained from sheep production units of the State of Mexico. E. coli isolates were confirmed through the amplification of the uid A gene. antimicrobial sensitivity pattern was determined through Kirby-Bauer (CLSI, 2012) test and the presence stx 1 , stx 2 and eae genes from isolates by multiplex PCR. Serotyping was performed using specific anti-O and anti-H sera (SERUNAM, Mexico) for 185 Somatic and 56 flagellar antigens. 126 isolates biochemically and molecularly identified as E. coli were obtained, of which 80 did not express any virulence factor and 46 expressed at least some (STEC) virulence factor. The highest percentage of E. coli resistance was for tetracycline 48.7% (39/80), followed by nalidixic acid 13.7% (11/80), gentamicin 6.2% (5/80) and Ciprofloxacin 3.7% (3/80). Resistance to amikacin, cefotaxime and ceftazidime were not detected. A frequency of 46 STEC isolates (36.2%) were obtained, of which 28/46 (22.0%) expressed stx 1 , stx 2 3/46 (6.5%), stx 1 , stx 2 13/46 (10.2%) and eae 2/46 (1.6%). Thirty different serotypes were obtained. The three serotypes with the highest number of isolates (four each) were: O76:H19, O118:H27 and O146:H21 which have been identified as a cause of diarrhea in human population. An isolate of serogroup O104 was obtained, with a significant importance for European public health. In virtue of the discovered serotypes and the virulence factors distribution, we can affirm that the obtained isolates from lambs in the State of Mexico are classifiable as atypical STEC of low virulence.

Diversity of Potentially Pathogenic Escherichia coli O104 and O9 Serogroups Isolated before 2011 from Fecal Samples from Children from Different Geographic Regions

“…Another interesting serotype identified in our study was E. coli O104:H7. This serotype presented the eae gene and for this reason, it was classified as atypical EPEC (a-EPEC), which is a difference from other strains with the same serotype isolated from cases of human diarrhea and sheep that were reported as being positive for stx and negative for eae [41][42][43]. With this in mind, it has been proposed that cattle and sheep could be possible reservoirs for O104:H7 [41,43].…”

“…This serotype presented the eae gene and for this reason, it was classified as atypical EPEC (a-EPEC), which is a difference from other strains with the same serotype isolated from cases of human diarrhea and sheep that were reported as being positive for stx and negative for eae [41][42][43]. With this in mind, it has been proposed that cattle and sheep could be possible reservoirs for O104:H7 [41,43]. Another serotype identified in our study was O104:H12 from Mexico, Argentina and Bangladesh, which was classified as STEC, and STEC/EAEC.…”