Fecal carriage of mcr-1-positive Enterobacteriaceae increases in China

Fecal carriage of mcr-1-positive Enterobacteriaceae has increased substantially in Guangzhou, China, in recent years, study data showed. The mcr-1 gene has been associated with resistance to colistin, the so-called “antibiotic of last resort.”

“Transmissible mcr-1-mediated colistin resistance was recently identified in Escherichia coli and Klebsiella pneumoniae isolates from hospitalized humans, animals (pigs) and raw meat (pigs and chickens) in China, with higher rates in animal samples,” Nicole Stoesser, MD, DPhil, of the Nuffield Department of Medicine at the University of Oxford, and colleagues wrote. “Prevalence in humans remains low, and mostly restricted to hospitalized patients. However, mcr-1 can be carried in the healthy human gut.”

The researchers collected fecal samples from both inpatients and outpatients who submitted samples to three hospitals in Guangzhou from 2011 to 2016 (n = 8,022). Stoesser and colleagues evaluated mcr-1 carriage trends using iterative sequential regression.

Overall, 497 samples (6.2%) were mcr-1 positive, the researchers wrote, and 182 (2.3%) of the samples contained mrc-1-positive, third-generation cephalosporin-resistant Enterobacteriaceae.

The incidence of mcr-1 rose significantly, from 0% in April 2011 to 31% in March 2016, Stoesser and colleagues wrote, and the same was true of mcr-1-positive, third-generation cephalosporin-resistant Enterobacteriaceae, which increased from 0% in April 2011 to 15% in March 2016 (P < .001). The mcr-1-positive, third-generation cephalosporin-resistant isolates were frequently multidrug resistant, the researchers reported.

Whole-genome sequencing (WGS) of mcr-1-positive, third-generation cephalosporin-resistant isolates — three K. pneumoniae and 70 E. coli isolates — revealed a large diversity of bacterial strains, including 48 E. coli sequence subtypes, Stoesser and colleagues wrote. The mcr-1 gene was associated with common plasmid backbones and sometimes occurred in multiple plasmids. Sequencing also showed a “high mobility of the mcr-1-associated insertion sequence ISApl1.

“In this, the largest study of human fecal carriage and WGS of mcr-1 isolates to our knowledge, we observed alarming sequential increases in carriage of mcr-1, and of mcr-1-positive, cefotaxime-resistant Enterobacteriaceae fecal carriage over 5 years,” the researchers wrote. “We also found significant diversity and genetic plasticity of [mobile genetic elements] harboring mcr-1 that may explain some of these dramatic increases.” – by Andy Polhamus

 

Disclosures: The authors report no relevant financial disclosures.