Stewardship / Resistance Scan for Feb 22, 2019

Antibiotic Rx for skin infections
MCR-1, MCR-3 hybrid E coli

Nursing home survey highlights antibiotic overuse for skin infections

A study today in Epidemiology and Infection reports that less than a third of the residents in Australian nursing homes who were prescribed an antimicrobial for a skin infection had a confirmed bacterial infection.

The data come from the Aged Care National Antimicrobial Prescribing Survey, a structured point-prevalence survey of Australian nursing homes conducted from June to September 2017. The researchers focused on skin and other soft-tissue infections (SSTIs), because findings from previous surveys have indicated that SSTIs are the second most common infection among nursing home residents. Data collected about antimicrobials prescribed on the survey day included clinical indication, rationale, route, frequency, and duration.

Of the 12,319 surveyed residents from 292 aged care facilities, 452 (3.7%) were prescribed an antimicrobial for an SSTI. The most frequently reported clinical indications among residents were cellulitis, soft tissue or wound infection (n = 130), followed by fungal skin infection (60), conjunctivitis (49) and oral candidiasis (18). Confirmed infection was documented in only 29% of cases. Topical clotrimazole was most frequently prescribed, often for unspecified indications. Where an indication was documented, antimicrobial choice was generally aligned with recommendations.

"While targeted antimicrobial prescribing is generally aligned with national recommendations, we observed a large proportion of prescribed antimicrobial agents to be for unspecified clinical indications," the authors of the study write. "Methods to enhance clinician documentation of indications for antimicrobial therapy are required, and development of standardised tools for assessing appropriateness of antimicrobial agents in elderly populations would support these interventions."
Feb 22 Epidemiol Infect abstract


Chinese researchers report MCR-1, MCR-3 resistance genes together

Chinese scientists have identified a novel hybrid plasmid with both MCR-1 and MCR-3 colistin-resistance genes from an Escherichia coli isolate, they noted yesterday in the Journal of Antimicrobial Chemotherapy.

The isolate was obtained from pig manure in Sichuan province. Via whole-genome sequencing and other tests, the scientists identified both MCR-1 and MCR-3.19 on a single plasmid, which are mobile segments of DNA that can transfer resistance genes to other pathogens, including non–E coli microbes. Colistin is a last-resort antibiotic used against multidrug-resistant bacteria.

The genetic structure of the two genes was similar to those found previously in plasmids. The researchers also identified three other plasmids in the isolate, two of which harbored resistance genes.

"This finding suggested that evolution of mcr genes among various plasmids was being driven by mobile elements," the authors conclude. "Molecular surveillance of mcr gene co-occurrence warrants further investigation to evaluate the public health risk."
Feb 21 J Antimicrob Chemother abstract

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