ABSTRACT
Introducción. Ante la aparición de reportes de la presencia del gen mcr-1 y su posible diseminación por plásmidos en los países de la región y dado que este gen confiere resistencia a colistín, fármaco que es la última línea de tratamiento contra bacterias multirresistentes, es importante conocer su presencia en nuestro país en microorganismos que lo expresen. Métodos. Se realizó un estudio descriptivo y transversal. Se incluyeron microorganismos aislados de urocultivos de pacientes ambulatorios de un centro de salud privado en Lima, Perú, en agosto del año 2017. De 326 urocultivos positivos se seleccionaron 10 aislamientos entre cepas de Escherichia coli y Klebsiella pneumoniae que presentaron concentración mínima inhibitoria ≥ 4µg/ mL (interpretado como resistente para colistín) por el sistema automatizado Microscan Walkaway 96 plus. Se utilizaron los siguientes métodos: colistín agar spot, predifusión con tabletas de colistín, microdilución en caldo colistin y PCR para el gen mcr-1. Resultados. Se determinó que 7 aislamientos, todas Escherichia coli, expresaron la presencia del gen mcr-1 por PCR, el cual confiere resistencia plasmídica a polipéptidos. De las cepas restantes, dos Escherichia coli y una Klebsiella pneumoniae, resultaron positivos para resistencia a colistín en las pruebas fenotípicas pero no en la PCR para gen mcr-1 lo cual sugiere un mecanismo de resistencia a colistín no asociado a gen mcr-1. Conclusiones. Se obtuvieron 7 aislamientos de Escherichia coli resistentes a colistín y con expresión del gen mcr-1.
Introduction. Given the appearance of reports of the presence of the mcr-1 gene and its possible dissemination by plasmids in the countries of the region and given that this gene confers resistance to colistin, the drug that is the last line of treatment against multiresistant bacteria, it is important to know its presence in our country in microorganisms that express it. Methods. Descriptive and cross-sectional study was carried out. Microorganisms isolated from urine culture of outpatients from a private health center in Lima, Peru, were included in august 2017. Out of 326 positive urine cultures, 10 isolates were selected between strains of Escherichia coli and Klebsiella pneumoniae that had a minimum inhibitory concentration ≥4µg/mL (interpreted as resistant for colistín) by the automated system Microscan Walkaway 96 plus. The following methods were used: colistin agar spot, prediffusion with colistin tablets, microdilution in colistin broth and PCR for the mcr-1 gene. Results. It was determined that 7 isolates, all Escherichia coli, expressed the presence of the mcr-1 gene by PCR, which confers plasmid resistance to polypeptides. Of the remaining strains, two Escherichia coli and one Klebsiella pneumoniae, were positive for resistance to colistin in the phenotypic tests but not in the PCR for mcr-1 gene, which suggests a mechanism of colistin resistance not associated with the mcr-1 gene. Conclusions. Seven isolates of Escherichia coli resistant to colistin and with expression of the mcr-1 gene were obtained.