Objective To determine the epidemic characteristics of polymyxins resistance (mcr) genes of Enterobacteriales colonized in patients admitted to hospitals in Zhejiang, Henan, Gansu and Shandong provinces in China in 2023.
More...Objective To determine the epidemic characteristics of polymyxins resistance (mcr) genes of Enterobacteriales colonized in patients admitted to hospitals in Zhejiang, Henan, Gansu and Shandong provinces in China in 2023. Methods A comprehensive compilation of 667 fecal specimens from patients admitted to five medical facilities across the provinces of Zhejiang, Henan, Gansu, and Shandong in the year 2023 was conducted. An epidemiological examination was performed on Enterobacteriales bacteria positive for the mcr gene, employing techniques such as microbial culturing, agarose gel electrophoresis, polymerase chain reaction, whole genome sequencing, bioinformatics analysis, and the induction of antimicrobial resistance. Statistical analysis was subsequently applied to the gathered data. Results Among 667 fecal samples from admitted patients, five samples were positive for mcr gene, with a carrier rate of 0.75%(5/667), and two of the samples were isolated with two different strains of mcr gene. A total of 7 strains of Enterobacteriales carrying mcr gene were detected, of which 4 strains carried mcr-1 gene and 3 strains carried mcr-9 gene. The positive isolates comprised three strains of Escherichia coli, one strain each of Citrobacter braakii and Citrobacter freundii, and one strain each of Klebsiella pneumoniae and Enterobacter hormaechei. The seven strains exhibiting mcr positivity were isolated from two distinct geographical locations within China, with four from Zhejiang Province and three from Henan Province. The three isolates of mcr-1 positive Escherichia coli exhibited high levels of homology, whereas the three isolates of mcr-9 positive strains preserved a significant degree of homology within the mcr-9 and wbuc regions. Following polycolistin exposure, there was a marked disparity in the growth kinetics of the ZJ-307, HN-11-1, and HN-135 strains post-induction compared to their pre-induction growth rates, concomitant with a reduction in motility capacity. Conclusion The prevalence of Enterobacteriales harboring the mcr gene was minimal among hospitalized patients; however, it is noteworthy that these genes are susceptible to horizontal transfer into drug-resistant strains with elevated MICs. Furthermore, resistance to colistin can alter the bacterial growth rate and motility, potentially impacting the MICs of other antibiotics, thereby complicating clinical management. Consequently, there is an imperative to concentrate on the proactive screening of susceptible populations to forestall the further dissemination of plasmid-mediated colistin resistance among clinically significant Gram-negative bacterial pathogens.
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