MCR: modern colistin resistance

Abstract

Recently, plasmid-mediated and, therefore, transferable bacterial polymyxin resistance was discovered in strains from both humans and animals. Such a trait may widely spread geographically, while simultaneously crossing microbial species barriers. This may ultimately render the Blast resort^polymyxin antibiotics therapeutically useless. Colistin is currently used to treat infections caused by Gram-negative carbapenemase producers and colistin resistance may lead to practical panantibiotic resistance. We here analyzed the medical and diagnostic consequences of (emerging) colistin resistance and propose pathways toward adequate diagnostics for timely detection of both asymptomatic carriage and infection. Culture-based testing using chromogenic and selective media for screening clinical (and veterinary) specimens may constitute key tools for that purpose. Relevant molecular tests are also discussed.

Clinical Validation of SensiTest Colistin, a Broth Microdilution-Based Method To Evaluate Colistin MICs

“…This document highlights different actions for the implementation of surveillance strategies and antimicrobial stewardship about this topic. Moreover, the development of improved laboratory methods for the determination of the correct colistin MIC and molecular mcr-1 detection is considered beneficial and necessary (21). For colistin, a reliable evaluation of MICs, together with the possibility of therapeutic drug monitoring (TDM), is also necessary for the correct management of patients, given colistin's potential significant adverse effects, in order to avoid toxic effects while maintaining sufficient antibacterial activity (21).…”

Detection of mcr-1-Carrying Escherichia coli Causing Bloodstream Infection in a New York City Hospital: Avian Origins, Human Concerns?

“…Fortunately, isolate KP1749 retained susceptibility to multiple β-lactam agents, thus allowing adequate treatment and a satisfactory outcome. Since the description of mcr-1 , several other transferable mechanisms of colistin resistance have been identified [2]. Therefore, we need to develop more active surveillance approaches for detecting resistance to colistin.…”

“…Although phenotypic susceptibility testing forms the cornerstone, there are limitations in accuracy depending on the method used [8]. This problem is further compounded by the finding that most mcr-1 -producing isolates have lower colistin MICs in the range of 2–4 mcg/mL, and some isolates that are phenotypically susceptible may produce mcr-1 [2]. Therefore, our study may have underdetected mcr-1 , both due to issues with polymyxin susceptibility testing and because our screening strategy required isolates to initially have resistance to third-generation cephalosporins.…”

“…After initially being described in isolates from food animals, human carriage of mcr-1 was noted in Escherichia coli and Klebsiella pneumoniae in urine and blood samples from hospitalized patients. By January 2016, cases had been reported from 19 countries worldwide [2]. In the United States, 12 human mcr-1 cases have been reported in 9 states to date [3–7].…”

“…In the United States, 12 human mcr-1 cases have been reported in 9 states to date [3–7]. Most mcr-1 infections have occurred in patients that had not received polymyxins, leading to speculation that colonization with mcr-1 may have occurred after ingestion of contaminated meat products [2]. Underdetection of colistin resistance is possible because many microbiology laboratories do not perform routine colistin susceptibility testing on carbapenem-susceptible isolates [8].…”