Molecular Characterization of Escherichia coli Isolates Carrying mcr-1 , fosA3 , and Extended-Spectrum-β-Lactamase Genes from Food Samples in China

Abstract

This study surveyed the prevalence of mcr-1 in extended-spectrum-␤-lactamase (ESBL)-producing Escherichia coli strains of food origin in China and identified strains that carried mcr-1, fosA3, and ESBL genes, which were carried in various plasmids. The mcr-1 and ESBL genes could be cotransferred by one or more types of plasmids. The presence of these multidrug-resistant E. coli strains in food products might pose a huge threat to public health.KEYWORDS mcr-1, fosA3, ESBL-producing E. coli, transmission, circular intermediate, Tn6330, plasmids C linical and public health problems due to multidrug-resistant (MDR) bacterial infections have been further aggravated in recent years following the emergence of bla NDM-1 , a resistance gene that can mediate development of carbapenem resistance in the host strain and possesses the ability to disseminate rapidly among various species of bacterial pathogens worldwide (1, 2). Polymyxins have been regarded as the antibiotic of last resort to treat severe infections caused by carbapenem-resistant Enterobacteriaceae (CRE). Recently, a new plasmid-mediated colistin resistance mechanism, mediated by the MCR-1 protein, a phosphoethanolamine transferase that modifies bacterial lipid A through modification of its phosphoethanolamine moiety, was discovered (3). Since the initial discovery of mcr-1-positive Enterobacteriaceae strains in China in 2015, this resistance mechanism has been reported in various parts of the world (3, 4). However, there is still a lack of comprehensive information regarding the prevalence of mcr-1 in Escherichia coli of food origin. This study reports the isolation and characterization of foodborne E. coli strains that carried mcr-1, fosA3, and ESBL genes.A total of 408 nonrepeated cefotaxime-resistant E. coli isolates were obtained from 828 retail food samples (484 pork, 76 beef, 143 chicken, and 125 shrimp) purchased from open-air markets and supermarkets in Shenzhen, China, during the period of 10 August 2015 to 22 February 2016. E. coli isolates were selected on MacConkey agar plates supplemented with 2 g/ml cefotaxime and identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) using a Bruker MicroFlex LT mass spectrometer (Bruker Daltonics). E. coli isolates were further confirmed by API20E test strips (bioMérieux, Inc.). All the E. coli strains were subjected to antimicrobial susceptibility testing for 11 antimicrobials using the agar dilution method according to the CLSI guidelines (5). All isolates were shown to be resistant to ampicillin, cefotaxime, ceftriaxone, and sulfamethoxazole-trimethoprim. They also exhibited resistance to other antibiotics, such as tetracycline (96%), nalidixic acid (84%), chloramphenicol (86%), Citation Liu X, Li R, Zheng Z, Chen K, Xie M, Chan EW-C, Geng S, Chen S. 2017. Molecular characterization of Escherichia coli isolates carrying mcr-1, fosA3, and extended-spectrum-β-lactamase genes from food samples in China. Antimicrob Agents Chemother 61:e00064-17.

Increased prevalence of Escherichia coli strains from food carrying blaNDM and mcr-1-bearing plasmids that structurally resemble those of clinical strains, China, 2015 to 2017

“…Until 2015, almost all reported polymyxin resistance mechanisms were coded on the chromosome and mediated by mutations in two component regulatory systems (PmrAB, PhoPQ), loss of lipopolysaccharide, or mgrB inactivation in the case of K. pneumoniae [10,11]. Importantly, a report by Liu et al in November 2015 described the emergence of a conjugative plasmid-mediated colistin resistance gene, mcr-1 , which encodes an enzyme (MCR-1) that belongs to the phosphoethanolamine transferase enzyme family and leads to altered bacterial lipid A in Enterobacteriaceae through modification of the phosphoethanolamine moiety [10-12]. Identification of mcr-1 as a plasmid-mediated resistance mechanism highlights its potential to act as a transmissible colistin resistance determinant.…”

Dissemination and Comparison of Genetic Determinants of mcr-Mediated Colistin Resistance in Enterobacteriaceae via Retailed Raw Meat Products

“…The dissemination of mcr genes in gram-negative bacteria isolated from food-producing animals and from food in Asian countries (Kawanishi et al, 2016;Liu et al, 2017;Wu et al, 2018) was confirmed by the detection of E. coli and C. braakii with the mcr-1 gene in two samples of rabbit meat imported from China. The examined rabbit meat samples from Hungary and the Czechia did not contain bacteria with mcr genes.…”

“…The plasmidmediated fosA3 gene variant is the most commonly reported in E. coli and other Enterobacteriaceae in Asia (Ito et al, 2017). Liu et al (2017) detected the fosA3 gene in seven ESBL-producing E. coli strain carrying the mcr-1 gene that were isolated from food of animal origin. The occurrence of fosfomycin resistance in Asia, but also its sporadic detection in strain of animal origin in Europe , represents another public health concern.…”

The Prevalence of Colistin Resistant Strains and Antibiotic Resistance Gene Profiles in Funan River, China

“…We identified two strains (E29 and E36) that carried mcr-1 , fosA3 , and bla CTX-M-9 genes from river samples (Table 3). The mcr-1 , fosA3 , and ESBLs genes were previously identified in E. coli isolated from animal and food samples (Liu X. et al, 2017; Lupo et al, 2018), and the presence of these multidrug-resistant strains in urban river may present a serious threat to public health.…”