Caracterização fenotípica e molecular de isolados clínicos de Acinetobacter baumannii provenientes da fronteira oeste do Rio Grande do Sul

Abstract

Acinetobacter baumannii is one of the main bacterial species related to nosocomial infections, frequently associated with ventilator-associated pneumonia in ICUs. Antimicrobial resistance in A. baumannii has emerged worldwide in recent decades reaching alarming levels, including for carbapenems, with resistance rates achieving approximately 80% in Brazil. The main mechanism associated to carbapenem resistance is the production of Class D carbapenemases or OXA-carbapenemases. Six families of OXA enzymes have been reported in A. baumannii and OXA-23 is the most prevalent in isolates worldwide. The aim of this study was to characterize carbapenem-resistant A. baumannii (CRAb) clinical isolates from the western border region of Rio Grande do Sul state according to sensitivity profile, prevalence of OXA- carbapenemases and genetic relationship through molecular typing. The isolates were provided from a single health institution and they were collected from 2014 to 2018. The species A. baumannii was identified by the presence of the blaOXA-51 gene and the sensitivity profile was determined by broth microdilution. Phenotypic detection of carbapenemase production was performed by the association test of inhibitors EDTA and phenylboronic acid to carbapenems and by the Blue-Carba test. Molecular confirmation was performed by PCR amplification of the main carbapenemase encoding genes. The genetic relationship among CRAb isolates was determined by REP-PCR and PFGE. During the study period, a total of 36 carbapenem resistant Acinetobacter spp. were isolated, mainly from respiratory tract (66.6%). In addition to resistance to all β-lactams tested and ciprofloxacin, the isolates also showed high level resistance to gentamicin (86.1%) and amikacin (61.1%). On the other hand, all of them were sensitive to polymyxin B (MICs ≤ 1 μg/mL). The blaOXA-23 gene was detected in 34 CRAb isolates. Typing revealed the presence of three main genetically related groups and four clonal strains, two present and prevalent in the institution during the four years of the study and two of more recent origin, in 2017. From the results obtained it was possible to verify a high prevalence of OXA-23 producing AbRC isolates, with the dissemination and permanence of clonal strains in the institution. The resistance in A. baumannii is not a public health problem only in large health centers in the country, serving as a warning about the need for more effective measures for control and prevention. Furthermore, the results of this study provide the first epidemiological data of this species in this region of the country, contributing to the construction of a broader overview of antimicrobial resistance in A. baumannii.