Stewardship / Resistance Scan for Feb 08, 2017

MCR-1 increase in China
Resistant Acinetobacter

Chinese study finds increasing rate of MCR-1 carriage in humans

A new study out of China indicates that human fecal carriage of MCR-1-positive, multidrug-resistant Enterobacteriaceae is on the rise.

For the study, posted yesterday on the preprint server bioRxiv, Chinese investigators tested 8,022 human fecal samples collected from three hospitals in Guangdong from April 2011 through March 2016. They were looking for the presence of the MCR-1 gene, which was first identified in Escherichia coli samples from pigs, pork products, and humans in China in 2015.

MCR-1 has since become a major health concern because it confers resistance to colistin, a last-resort antibiotic used in the treatment of multidrug-resistant infections. An additional concern is the co-existence of the gene, which is carried on mobile pieces of DNA called plasmids, with other resistance mechanisms.

Of the 8,022 fecal samples, the investigators found that 497 (6.2%) were MCR-1 positive, and 182 (2.3%) were MCR-1 positive and resistant to cefotaxime, a broad-spectrum cephalosporin. From the fecal samples harboring MCR-1-positive/cefotaxime-resistant Enterobacteriaceae, the team identified 187 distinct Enterobacteriaceae isolates from 179 individuals. The vast majority of the isolates (173) were Escherichia coli.

The rate of MCR-1 gastrointestinal carriage noted in the study is significantly higher than previous studies have found. The investigators also found that the MCR-1-positive and MCR-1-positive/cefotaxime-resistant samples increased significantly over the 5 years of the study, with a specific increase after January 2014. In addition, genetic analysis showed that the MCR-1 gene is spreading through a diverse set of genetic mechanisms (including strains, plasmids, and insertion sequences) that are helping contribute to its dissemination and could help facilitate its persistence.

"Our genetic analyses suggest the rapid emergence of several major plasmid vectors of mcr-1 within numerous multidrug-resistant E. coli strains carried by humans, and highlight the significant degree of plasticity in these plasmid vectors harbouring mcr-1 over short periods of time," the authors write.

The study has not yet been peer-reviewed.
Feb 8 bioRxiv abstract

Report notes high levels of highly resistant Acinetobacter in Nepal

Almost all isolates of Acinetobacter baumannii in Nepal were found to be resistant to multiple antibiotics, according to a small study yesterday in Antimicrobial Resistance & Infection Control.

Nepalese researchers analyzed 44 isolates of A baumannii, an increasingly important pathogen. The found that 43 (98%) were resistant to carbapenems, an important tool for combating antibiotic-resistant bacteria. The same number of isolates were multidrug resistant, but all were susceptible to colistin. The bla-OXA-23 gene was detected in all of the isolates, while the New Delhi Metallo-beta-lactamase-1 (NDM-1) gene was identified in 6 (14%).

The authors conclude, "Systemic network surveillance should be established for monitoring and controlling the spread of these resistant strains."
Feb 7 Antimicrob Resist Infect Control study

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