Molecular and phenotypic characterization of Escherichia coli from calves in an important meat-producing region in Brazil

Abstract

Introduction: Escherichia coli strains that lead to enteritis are considered an important cause of diarrhea in calves. For correct identification, these microorganisms must be differentiated from non-pathogenic members of the intestinal microbiota. The aim of the present work was to characterize E. coli isolates in calves regarding the presence of virulence genes that cause enteritis and evaluate the sensitivity of the isolates to different antimicrobials.

Methodology: One hundred forty-nine samples from beef cattle and 27 samples from dairy cattle were evaluated. All samples were submitted to microbiological identification and the disk diffusion antibiogram test. The polymerase chain reaction method was used to detect virulence genes.

Results: A hundred seventy-six samples were biochemically identified as E. coli and antibiograms were determined. The samples were then submitted to PCR; 35 were positive for the eae gene (19.88%), 135 (76.70%) for the stx1 gene, 62 (35.22%) for the stx2 gene, 159 (90.34%) for the sta gene and 35 (19.88%) for the ltII gene. No samples were positive for the cnf gene. Based on these results, the E. coli isolates were classified into pathotypes: enteropathogenic (n = 3), enterohemorrhagic (n = 32), Shiga toxin-producing (n = 122) and enterotoxigenic (n = 163). The antimicrobial sensitivity tests revealed that 77.2% of the isolates were resistant to three or more pharmacological groups, characterizing these isolates as multidrug resistant.

Conclusions: Enterotoxigenic E. coli was the predominant pathotype. Moreover, the prevalence of multidrug-resistant isolates was very high, accounting for the vast majority of isolates.