Molecular characterization of extended-spectrum β-lactamase-producing Escherichia coli isolated from postpartum uterine infection in dairy cattle in India

Selection and dissemination of plasmid-encoded extended-spectrum β-lactamase (ESBL) among confers resistance to beta-lactam antibiotics. The purpose of this study was to determine the prevalence and molecular characteristics of ESBL-producing organisms isolated from dairy cattle with a uterine infection. Bacterial isolates (n=62) were characterized by biochemical test for genus and species determination. Antimicrobial susceptibility tests were performed by Kirby-Bauer disk diffusion method using panel of antibiotics for initial screening of ESBL organism. Phenotypic confirmation of ESBL-suspected strains was done by combination disk method and double-disk method. Multiplex polymerase chain reaction (PCR) was carried out for phylogrouping of isolates as well as for genotyping ESBL genes. Enterobacterial repetitive intergenic consensus-PCR method was used for genotypic characterization of isolates. Antibiotic susceptibility profile of (n=40) isolates showed high rates of resistance for ampicillin (95.0%), cefpodoxime (97.5%), cefotaxime (87.5%), and ceftriaxone (70%). However, low rates of resistance were observed for cefoxitin (25%), amoxicillin/clavulanic acid (20%), ceftazidime (17.5%), gentamicin (10%), and ertapenem (7.5%). A total of 39/40 isolates were confirmed as ESBL with Epsilometer test as well as the genotypic method and 28 (70%) of them were multidrug-resistant. Genotype was observed as a predominant beta-lactamase type with the preponderance of CTX-M Group 1. The following combinations were observed: + in 15 (36.2%) isolates, / in 8 (5.2%) isolates, and / in 6 (5.2%) isolates. The phylogenetic grouping of strains revealed the highest prevalence for B1 (22.0%) followed by A (20%). This report shows a high frequency of ESBL from cattle with postpartum uterine infections. These isolates showed reduced susceptibility to common antibiotics used for the treatment of uterine infections greater affecting the therapeutic outcome.