Occurrence and characterisation of enterohaemorrhagic Escherichia coli isolates from diarrhoeic calves

Shiga Toxin-Producing Escherichia coli (STEC) Associated with Calf Mortality in Uruguay

In Uruguay, the mortality of dairy calves due to infectious diseases is high. Escherichia coli is a natural inhabitant of the intestinal microbiota, but can cause several infections. The aim of the work was to characterize E. coli isolates from intestinal and extraintestinal origin of dead newborn calves. Using PCR, virulence gene characteristics of pathogenic E. coli were searched. The pathogenic E. coli were molecularly characterized and the phylogroup, serogroup and the Stx subtype were determined. Antibiotic susceptibility was determined using the Kirby-Bauer disk diffusion method and plasmid-mediated quinolone resistance (PMQR) genes with PCR. Finally, clonal relationships were inferred using PFGE. Gene characteristics of the Shiga toxin-producing E. coli (STEC), Enteropathogenic E. coli (EPEC) and Necrotoxigenic E. coli (NTEC) were identified. The prevalence of the iucD, afa8E, f17, papC, stx1, eae and ehxA genes was high and no f5, f41, saa, sfaDE, cdtIV, lt, sta or stx2 were detected. The prevalence of STEC gene stx1 in the dead calves stood out and was higher compared with previous studies conducted in live calves, and STEC LEE+ (Enterohemorrhagic E. coli (EHEC)) isolates with stx1/eae/ehxA genotypes were more frequently identified in the intestinal than in the extraintestinal environment. E. coli isolates were assigned to phylogroups A, B1, D and E, and some belonged to the O111 serogroup. stx1a and stx1c subtypes were determined in STEC. A high prevalence of multi-resistance among STEC and qnrB genes was determined. The PFGE showed a high diversity of pathogenic strains with similar genetic profiles. It can be speculated that EHEC (stx1/eae/ehxA) could play an important role in mortality. The afa8E, f17G1 and papC genes could also have a role in calf mortality. Multidrug resistance defies disease treatment and increases the risk of death, while the potential transmissibility of genes to other species constitutes a threat to public health.

Prevalence of shiga toxins (stx1, stx2), eaeA and hly genes of Escherichia coli O157:H7 strains among children with acute gastroenteritis in southern of Iran

OBJECTIVE

To survey the prevalence severe diarrhea arising from these bacteria in children under 5 years old in Marvdasht.

METHODS

In this study faecal sample from 615 children aged <5 years old who were hospitalized for gastroenteritis in Fars hospitals in Iran were collected and then enriched in Escherichia coli (E. coli) broth and modified tryptone soy broth with novobiocin media. Fermentation of sorbitol, lactose and β -glucoronidase activity of isolated strains was examined by CT-SMAC, VRBA and chromogenic media respectively. Then isolation of E. coli O157:H7 have been confirmed with the use of specific antisera and with multiplex PCR method presence of virulence genes including: stx1, stx2, eaeA, hly has been analyzed.

RESULTS

E. coli O157:H7 was detected in 7 (1.14%) stool specimens. A significant difference was seen between detection rate of isolated bacteria from age groups 18-23 months and other age groups (P=0.004). Out of considered virulence genes, only 1 of the isolated strains (0.16%) the stx1 and eaeA genes were seen and also all isolated bacteria had resistance to penicillin, ampicillin and erythromycin antibiotics.

CONCLUSIONS

We found that children < 2 years of age were at highest risk of infection with E. coli O157:H7. Regarding severity of E. coli O157:H7 pathogenesis, low infectious dose and lack of routine assay for detection of these bacteria in clinical laboratory, further and completed studies on diagnosis and genotyping of this E. coli O157:H7 strain has been recommended.