Stewardship / Resistance Scan for May 23, 2018

NDM plus MCR-1 in E coli
;
C diff and sharps containers

NDM, MCR-1 resistance genes found in same E coli isolates in China

Chinese scientists yesterday reported on the emergence of extensively drug-resistant (XDR) Escherichia coli carrying both New Delhi metallo-beta-lactamase (NDM) and MCR-1 genes in chickens at slaughter in China and detailed the features of two novel NDM-carrying plasmids.

In a letter in the Journal of Antimicrobial Chemotherapy, the investigators said they collected 50 fecal samples from chickens at a slaughterhouse in Qingdao, which sits on the Yellow Sea in eastern China. They recovered 33 E coli isolates from the samples.

Two of the strains showed resistance to imipenem and had an XDR pattern. Polymerase chain reaction and Sanger sequencing confirmed that the strains harbored both NDM and MCR-1. In one isolate the resistance genes were located on separate plasmids, while on the other the NDM gene was on a plasmid and the MRC-1 gene was on a chromosome. Plasmids are mobile pieces of DNA that can transfer to other bacteria of either the same or different species.

NDM-1 was first detected in 2008 and confers resistance to a broad range of beta-lactam antibiotics, including carbapenems. MCR-1 was first identified in China in 2015 and confers resistance to colistin, an antibiotic of last resort. So the detection of both of them in the same bacterium warrants increased concern over XDR pathogens that may be untreatable.

In addition, the scientists write, "To the best of our knowledge, this study identified for the first time the presence of blaNDM-1 gene in phage-like IncY plasmid, which has been associated with mcr-1 and blaVIM-1. Although phage-like plasmid is non-conjugative, it can be integrated into conjugative plasmids via recombination." They also note that one MCR-1 was found on an IncI2 plasmid that was almost 99% identical to a plasmid belonging to IncK2, which has been tied to the spread of MCR-1 in E coli in Europe.
May 22 J Antimicrob Chemother letter

 

Study find sharps containers pose no risk of C difficile infection

A microbiological investigation published yesterday in the American Journal of Infection Control has found the containers used to safely dispose of needles and other sharp medical instruments pose no risk of Clostridium difficile infection (CDI).

The investigation was following up on a 2015 study that found that a significantly lower rate of CDI in hospitals that used disposable sharps containers (DSCs) over those using reusable sharps containers (RSCs), but did not propose a scientific explanation for how the containers might spread CDI to patients. The hypothesis was that the statistical association found in the previous study was an artifact and that DSCs and RSCs may have a low spore burden but no fomite potential.

The study was conducted in three stages. In the first, 197 RSCs were swabbed for the presence of C difficile before processing. In the second stage, RSCs were challenged with high C difficile densities to evaluate the decontamination process. In the third stage, the investigators sampled 50 DSCs and 50 RSCs in CDI patients' rooms in seven hospitals to determine whether they differed in their carriage rate of C difficile spores. The investigators combined this evidence with epidemiologic studies, clinical requirements, and chain-of-infection principles.

The results showed that C difficile spores were found on 9 of 197 (4.6%) RSCs prior to processing, but that processing completely removed all spores. In CDI patient rooms, the C difficile carriage rate was 8% with RSCs and 16% with DSCs, but the investigators found an insufficient number of spores on either type of container to constitute an infective dose. In addition, because sharps containers are no-touch and healthcare workers must remove gloves after sharps disposal, a mode of transmission to the patient is impossible.

"In examining epidemiologic, microbiologic, chain-of-infection and test-of-evidence criteria, we could find no scientific evidence or mechanism whereby sharps containers could be implicated in CDI transmission," the authors write.
May 22 Am J Infect Control study

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