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China banned colistin as growth promoter for animals in the year of 2017. A decrease of colistin-resistant Escherichia coli (COREC) and mcr-1-positive Escherichia coli (MCRPEC) were observed in livestock (pigs and chickens) and humans after the ban policy. However, the prevalence of COREC among Chinese companion animals after the ban policy has not been investigated. Here, we recovered 771 E. coli isolates from the China Antimicrobial Resistance Surveillance Network for Pets (CARPet) surveillance system (19 provinces/municipalities) from 2018 to 2021. We identified 12 COREC from eight dogs and four cats, among which one feline and three canine isolates were MCRPEC. The prevalence of COREC and MCRPEC in pets from 2018–2021 (1.1%–2.2% and 0.8%–1.1%) were lower than those from 2012–2016 (7.1%–17.8% and 6.1%–14.3%). The phylogenetic analysis revealed that the four MCRPEC isolates displayed genetic diversity, while one canine isolate exhibited only 26 SNPs difference with one human MCRPEC isolate in the same city, suggesting the exchange of MCRPEC isolates between companion animals and humans. In three MCRPEC isolates, mcr-1 was located on an IncI2 plasmid, which exhibited 99.5%–99.9% nucleotide sequence identity with plasmid pHNSD133-MCR from E. coli of chicken origin. In the remaining MCRPEC, mcr-1 was chromosomally located flanked by intact ISApl1 elements forming a unit of ISApl1-mcr-1-pap2-ISApl1. Despite the low prevalence of COREC and MCRPEC observed in companion animals after the ban policy, the association of pet-derived MCRPEC and mcr-carrying plasmids with those from humans and farm animals suggest that annual surveillance of colistin resistance in bacteria of pet origin is essential. [ABSTRACT FROM AUTHOR]

ABSTRACT Despite no carbapenem use in food animals, carbapenem-resistant Klebsiella pneumoniae (CRKP) perseveres within food animals, rising significant concerns regarding public health risks originating from these non-clinical reservoirs. To investigate the potential link between CRKP in food animals and its infections in humans, we conducted a cross-sectional study encompassing human clinical, meat products, and farm animals, in Qingdao city, Shandong province, China. We observed a relatively higher presence of CRKP among hospital inpatients (7.3%) compared to that in the meat products (2.7%) and farm animals (pig, 4.6%; chicken, 0.63%). Multilocus sequence typing and core-genome phylogenetic analyses confirm there is no evidence of farm animals and meat products in the clinical acquisition of K. pneumoniae isolates and carbapenem-resistant genes. However, potential transmission of K. pneumoniae of ST659 and IncX3 plasmid harbouring bla NDM-5 gene from pigs to pork and farm workers was observed. Our findings suggest a limited role of farm animals and meat products in the human clinical acquisition of K. pneumoniae , and the transmission of K. pneumoniae is more common within settings, than between them.

Mobile colistin resistance gene mcr-1 and extended-spectrum β -lactamase gene bla CTX-M are highly prevalent in human - and pet-derived bacteria. Isolation of identical strains of mcr-1 -positive Escherichia coli (MCRPEC) or bla CTX-M -positive E. coli (CTX-MPEC) from pets and humans highlighted the potential for co-colonization of antibiotic-resistant bacteria which can be a risk for dissemination of resistance genes. In this study, the prevalence of mcr-1 and bla CTX-M carriage from rectal swabs in 299 families (dogs and their owners) were 2.7 and 5.3%, respectively. We identified a significant association of mcr-1 carriage between dogs and their owners. Whilst antibiotic use in the previous three months was associated with bla CTX-M carriage in dogs. Only one instance of dog and owner carrying identical CTX-MPEC was observed. Although the prevalence of identical strains in one family is rare, the huge number of dog ownership worldwide suggest that this threat should not be underestimated.