Genomic characteristics of mcr-1 and blaCTX-M-type in a single multidrug-resistant Escherichia coli ST93 from chicken in China

Abstract

This study was undertaken to discern the transmission characteristics of mcr-1 and bla CTX-M-type in one multidrug-resistant Escherichia coli LWY24 from chicken in China. The genetic profiles of LWY24 isolate were determined by conjugation, S1-pulsed-field gel electrophoresis, southern blot hybridization, and whole genome sequencing analysis. Meanwhile, co-transfer of plasmids in LWY24 isolate was screened by dual conjugation assays. The LWY24 isolate was identified as ST93, and harbored 3 conjugative plasmids, pLWY24J-3 ( bla CTX-M-55 -bearing IncFⅡ), pLWY24J- mcr-1 ( mcr-1 -carrying IncI2), and pLWY24J-4 (non-resistance-conferring IncI1), and one nonconjugative plasmid pLWY24 ( bla CTX-M-14 -containing IncHI2/IncHI2A). Numerous resistance genes, insertion sequences (especially IS 26 ), and transposons were found in the 4 plasmids, suggesting that horizontal transmission have occurred by plasmid mating, homologous recombination, and transpositions. Under the selection pressure of cefotaxime and colistin or cefotaxime alone, the mcr-1 -bearing plasmid and the bla CTX-M-55 -harboring plasmid could be co-transferred at a similar frequency, with 8.00 × 10 −4 or 9.00 × 10 −4 transconjugants per donor cell, respectively. The specific shufflon region in mcr-1 -encoding plasmid could generate up to 6 diverse PilV structures, which may further accelerate the horizontal transfer of plasmid. In conclusion, the transmission characteristics of mcr-1 and bla CTX-M-type in LWY24 isolate could due to clonal spread of ST93, selective pressure of cefotaxime, IS 26 -mediate homologous recombination and transposition, and the specific shufflon region.

Spreading Advantages of Coresident Plasmids bla CTX-M -Bearing IncFII and mcr-1 -Bearing IncI2 in Escherichia coli

“…Intriguingly, when plasmids FII and I2 coresided in the host, almost no plasmid loss was detected over the 15 days of the experiment, which implied that the stability of bla CTX-M -carrying FII plasmid and mcr-1 -harboring I2 plasmid could significantly improve by coresidence. The results were consistent with previous studies that the stability of coexistent plasmids increased ( 17 ), which contributed to elucidating why bla CTX-M and mcr-1 are easier to locate on diverse plasmids in the same bacterial host worldwide ( 13 – 15 ).…”

“…3b ). Together, E. coli coharboring plasmids FII and I2 will not confer more fitness costs than bacteria carrying one plasmid FII or I2, which helps to promote the coexistence of plasmid-carried bla CTX-M and mcr-1 in E. coli and to clarify why more and more Enterobacteriaceae carry both bla CTX-M and mcr-1 ( 11 , 15 ).…”

“…Recently, resistant genes bla CTX-M and mcr-1 have been simultaneously detected in Enterobacteriaceae species isolated from humans and animals ( 8 , 10 , 11 ). Although they sometimes coexist on the same plasmid ( 8 , 12 ), the bla CTX-M and mcr-1 genes are usually located on diverse plasmids of the same bacterial host ( 13 – 15 ). In a previous survey on antimicrobial-resistant bacterial isolates in China, Escherichia coli LWY24 was isolated from healthy chicken feces in Henan Province ( 15 ).…”

“…Although they sometimes coexist on the same plasmid ( 8 , 12 ), the bla CTX-M and mcr-1 genes are usually located on diverse plasmids of the same bacterial host ( 13 – 15 ). In a previous survey on antimicrobial-resistant bacterial isolates in China, Escherichia coli LWY24 was isolated from healthy chicken feces in Henan Province ( 15 ). The isolate LWY24 harbored bla CTX-M-55 and mcr-1 , which were located on an IncFII replicon pLWY24J-3 ( bla CTX-M-55 -bearing, MN702385 ) and an IncI2 replicon pLWY24Jmcr-1 ( mcr-1 -carrying, MN689940 ), respectively, and could carry out horizontal transfer by plasmid conjugation, independently or simultaneously.…”

Genomic Epidemiology of Colistin-resistant Enterobacterales from Dutch Patients: A Prospective Matched Case-control Study

“…18 Colistin resistance may be triggered directly by selection during treatment with colistin 11 or indirectly during treatment with other antibiotics by cotransfer of the mcr gene with other resistance genes on the same plasmid or different plasmids. 19,20 Little is known about the genomic epidemiology of colistin resistance in the Netherlands. One outbreak with colistin-resistant carbapenemase-producing K. pneumoniae has been described.…”