Genetic analysis of antimicrobial resistance in Escherichia coli isolated from diarrheic neonatal calves

This study was carried out to screen and analyze the genetic basis of antimicrobial resistance in Escherichia coli strains isolated from neonatal calf diarrhea in Egypt. A total of 182 isolates of E. coli recovered from 91 diarrheic neonatal calves were analyzed for antimicrobial susceptibilities, the presence of class I and class 2 integrons and antimicrobial resistance genes. Nineteen isolates (10.4%) showed multidrug resistance phenotypes and harbored at least three antimicrobial resistance genes. PCR screening detected class 1 integrons in 19 isolates (10.4%) and class 2 integrons in 2 isolates (1.1%). The identified antimicrobial resistance genes within class 1 integrons were dihydrofolate reductase types: dfrA1, dfrA12, dfrA15 and dfrA17, which confer resistance to trimethoprim; aminoglycoside adenyltransferase types: aadA1, aadA2, aadA5, aadA7 and aadA23, which confer resistance to streptomycin and spectinomycin; and aminoglycoside acetyltransferase gene, aac(3)-ld, which confers resistance to gentamicin and sisomicin. Furthermore, many beta-lactamases encoding genes, plasmid-mediated quinolone resistance genes and florfenicol resistance gene were identified in this study. To the best of our knowledge, this is the first report for molecular characterization of antimicrobial resistance in E. coli isolated from diarrheic neonatal calves in Africa. (C) 2008 Elsevier B.V. All rights reserved.