High incidence of multidrug-resistant Escherichia coli coharboring mcr-1 and bla CTX-M-15 recovered from pigs

Muhammad Shafiq; Jinhu Huang; Sadeeq Ur Rahman; Jan Mohammad Shah; Li Chen; Yi Gao; Mengli Wang; Liping Wang

doi:10.2147/IDR.S209473

High incidence of multidrug-resistant Escherichia coli coharboring mcr-1 and bla _CTX-M-15 recovered from pigs

Infect Drug Resist. 2019 Jul 16:12:2135-2149. doi: 10.2147/IDR.S209473. eCollection 2019.

Authors

Muhammad Shafiq¹, Jinhu Huang¹, Sadeeq Ur Rahman², Jan Mohammad Shah¹, Li Chen¹, Yi Gao¹, Mengli Wang¹, Liping Wang¹

Affiliations

¹ Moe Joint International Research Laboratory of Animal Health and Food Safety, Laboratory of Veterinary Pharmacology and Toxicology, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
² College of Veterinary Sciences and Animal Husbandry, Section Microbiology, Abdul Wali Khan University, Mardan, KP, Pakistan.

Abstract

Purpose: The coexistence of mobile colistin (COL)-resistant gene mcr-1 with extended-spectrum beta-lactamase (ESBL) gene in Escherichia coli has become a serious threat globally. The aim of this study was to investigate the increasing resistance to COL and in particular its coexistence with ESBL-producing E. coli recovered from pig farms in China.

Materials and methods: E. coli were isolated from 14 pig farms in Jiangsu China. Susceptibility testing was identified by micro-dilution method. PCR assay and nucleotide sequencing were used to detect COL-resistant genes, mcr-1 to -5, as well as ESBL genes, bla _CTX-M, bla _SHV and bla _TEM. Conjugation experiment, plasmid replicon typing of the multidrug resistance (MDR), S1-PFGE and DNA southern hybridization were performed to study the transferability of these genes.

Results: Overall, 275 E. coli isolates were recovered from a total of 432 cloacal and nasal swabs. More than 90% of the isolates were MDR, of which 70.18% were resistant to COL. Of these 275 isolates, mcr-1 was identified as the most predominant gene carried by 71.63% (197/275) of isolates, 39.59% (78/197) of the isolates were harboring both mcr-1 and ESBL genes (bla _CTX-M, bla _SHV and bla _TEM). ESBL genotyping showed that bla _CTX-M was the most predominant ESBL (68.49%) followed by bla _SHV (16.4%) and bla _TEM (15%). Sequencing revealed that the most common variants of bla _CTX-M identified were, bla _CTX-M-15 (69%), bla _CTX-M-55 (29%) and bla _CTX-M-1 (1.8%). IncHI2, IncFIB, IncFIC, IncN and IncX4 were found to be the most common Inc-types found both in donors and in transconjugants and were associated with the transfer of the mcr-1 and ESBL encoding genes. Six strains carried a total of five different plasmids: approximately 97-, 130-, 160-, 227- and 242-kb plasmids.

Conclusion: The coexistence of the mcr-1- and bla _CTX-M-15-carrying isolates displaying high MDR, recovered from E. coli of pig origin, is a major concern for both humans and veterinary medicine.

Keywords: E. coli; ESBL; coexistence; colistin; mcr-1.