Infection Control & Hospital Epidemiology Adjacent to the screening, a prescribing and dispensing area
was established for patient examination. Privacy screens were used to create examination areas, and personal protective equipment, patient gowns, and linens were provided. Physicians staffed the clinic to assess patients who were concerned that they might have scabies. Supplies for skin scrapings and slide pre- paration were available, and a lab technician was on-call to collect specimens for processing. More than 1,000 doses of permethrin were distributed during the
clinics. There was 1 confirmed case of scabies and 3 probable cases of secondary transmission as a result of this outbreak.
263 Establishing a centrally located clinic using the incident
command system structure provided rapid and effective screening and prophylactic treatment of scabies to prevent a larger outbreak of scabies within the institution.
Acknowledgments. None. Financial support. No financial support was provided relevant to this article.
Conflicts of interest. All authors report no conflicts of interest relevant to this article.
Low prevalence of the mcr-1 gene among carbapenemase- producing clinical isolates of Enterobacterales
Tanise Vendruscolo Dalmolin1,2, Priscila Lamb Wink1, Daiana de Lima-Morales1 and Afonso Luís Barth1,2 1Laboratório de Pesquisa em Resistência Bacteriana, LABRESIS, Centro de Pesquisa Experimental, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil
and 2Programa de Pós-Graduação em Ciências Farmacêuticas, Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
To the Editor—Polymyxins are the last resort for the treatment of infections caused by multidrug-resistant bacteria, in particular carbapenem-resistant Enterobacterales (CRE). Resistance to polymyxins used to be due only to chromosomal mutations, but in November 2015, Liu et al1 described for the first time a colistin resistance mechanism mediated by a new gene (mcr-1) that was present in a transferable plasmid. The mcr-1 has already been described on most continents, being detected in different species and obtained from several sources, including carbapenemase- producing clinical isolates.2,3 Infections due to clinical isolates harboring the mcr-1 and a carbapenem resistance gene is of particular concern because the treatment options would be ser- iously compromised.4 The aim of this study was to evaluate the prevalence of car-
bapenemase and mcr-1 genes co-occurring among Enterobacterales clinical isolates in southern Brazil between April 2013 and May 2018. We evaluated the occurrence of the mcr-1 gene among 4,778
isolates of Enterobacterales with reduced susceptibility to carba- penems obtained from an epidemiologic study in several hospitals in southern Brazil. All isolates were submitted to multiplex real- time polymerase chain reaction with high-resolution melting (RT-PCR-HRM) analysis with primers for blaKPC, blaNDM, blaOXA-48-like, blaGES, blaIMP, and blaVIM and presented positive results for at least 1 of the carbapenemase gene(s) tested. The presence of the mcr-1 gene was evaluated by pooling 10
isolates together and submitting them to DNA extraction and conventional PCR with specific primers for the mcr-1 gene.1 All isolates from a pool with mcr-1 positive result were retested individually by the same conventional PCR to identify the isolate (s) that presented the gene. The amplicons from the individual
Author for correspondence: Afonso Luís Barth, LABRESIS, Hospital de Clínicas de Porto Alegre, Ramiro Barcelos 2350, Porto Alegre, Brazil. E-mail:
albarth@hcpa.edu.br
Cite this article: Dalmolin TV, et al. (2019). Low prevalence of the mcr-1 gene among carbapenemase-producing clinical isolates of Enterobacterales. Infection Control & Hospital Epidemiology 2019, 40, 263–264. doi: 10.1017/ice.2018.301
© 2018 by The Society for Healthcare Epidemiology of America. All rights reserved.
isolates with positive result in the conventional PCR were sub- mitted to Sanger sequencing and were confirmed as the mcr-1 variant. The minimal inhibitory concentrations (MICs) of several antibiotics were evaluated using broth microdilution method for the individual isolates positive for the mcr-1 gene, and the results were interpreted according to European Committee on Anti- microbial Susceptibility Testing (EUCAST) guidelines.5 We found only 5 isolates that presented the mcr-1 gene and a carbapenemase gene. All coharboring isolates presented the mcr-1 and the blaKPC genes. We obtained 2 coharboring isolates (Klebsiella pneumoniae 3111F and Escherichia coli 3431F) in 2014, 1 coharboring isolate (E. coli 5798F) in 2016, and the other 2 coharboring isolates (K. pneumoniae 6701F and E. coli 6699F) in 2018. All 5 isolates were recovered from rectal swabs, with exception of E. coli 6699F, which was recovered from an ascites fluid. Moreover, 4 isolates presented low-level resistance to colistin
(4 mg/L), and 1 isolate (K. pneumoniae 6701F) was susceptible to colistin (0.25 mg/L). All isolates were resistant to ertapenem, meropenem, imipenem, and ciprofloxacin and were susceptible to tigecycline. Susceptibility to aminoglycosides was variable, with most isolates susceptible to gentamicin and intermediate to amikacin (Table 1). Theprevalenceofthe mcr-1 gene was very low (0.1%) among carbapenemase-producing Enterobacterales (CPE) in our study. This rate is lower than that reported in Portugal, where 6.69% of the CPE isolates from colonized and infected patients were positive for the mcr-1 gene.6 In Belgium, the prevalence reported was <1% among CRE of human origin.7 These findings demonstrate that the prevalence of mcr-1 with carbapenemase genes is normally very low, although it can differ among countries. The mcr-1 gene is usually evaluated only among colistin-
resistant isolates (MIC>2 mg/L); however, the isolate K. pneumoniae 6701F was susceptible to colistin. Some isolates are mcr-1 positive; nonetheless they are colistin susceptible. One explanation for this is the assumption that the gene might be truncated in isolates positive for the mcr-1 but susceptible to
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