Characteristics and genetic diversity of multi-drug resistant extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli isolated from bovine mastitis

// Tariq Ali 1, * , Sadeeq ur Rahman 2, * , Limei Zhang 1 , Muhammad Shahid 1 , Dandan Han 1 , Jian Gao 1 , Shiyao Zhang 1 , Pamela L. Ruegg 3 , Umer Saddique 4 and Bo Han 1 1 Department of Clinical Veterinary Medicine, College of Veterinary Medicine, China Agricultural University, Beijing, P.R. China 2 College of Veterinary Sciences and Animal Husbandry, Abdul Wali Khan University, Garden Campus, Mardan, Pakistan 3 Department of Dairy Science, University of Wisconsin, Madison, WI, USA 4 Department of Animal Health, The University of Agriculture, Peshawar, Pakistan * These authors have contributed equally and co-first authors Correspondence to: Bo Han, email: hanbo@cau.edu.cn Keywords: E. coli , ESBL, multilocus sequence typing, PCR-based replicon typing, split network analysis Received: June 15, 2017      Accepted: August 23, 2017      Published: October 04, 2017 ABSTRACT A characterization of the drug resistance profiles, identification of PCR-based replicon typing, and multilocus sequence typing (MLST) and analysis of 46 ESBL-producing Escherichia coli from cows with mastitis are described. All multidrug-resistant isolates of various phylogenetic groups (A = 31, B1= 3, B2 = 2, D = 10) were ESBL-producers of genotypes CTX-M-15 (29), CTX-M-55 (4), CTX-M-14 (4), CTX-M-3 (1), CTX-M-1 (1), TEM (22) and SHV (8) that were found on conjugative plasmids of diverse incompatibility groups (primarily IncF). Transconjugation experiments indicated successful (100%) trans-conjugation, which was verified phenotypically and genotypically. A total of 28 sequence types (ST) were identified, with 10% of isolates being ST410, and 9 other ST that were assigned arbitrary numbers, reflecting the degree of diversity. Multilocus sequence analysis revealed two lineages, a dominant and a small lineage. Split-decomposition showed intraspecies recombination clearly contributed in genetic recombination generating genotypic diversity among the isolates, and a lack of interspecies recombination. This coherent analysis on genetic structure of multidrug-resistant pathogenic E. coli population isolated from mastitic-milk weaponized with resistance elements from a large, rapidly developing country will be a helpful contribution for epidemiology and surveillance of drug resistance patterns, and understanding their global diversity.