Occurrence of genetic determinants of resistance to colistin and biofilm in carbapenem-resistant Acinetobacter baumannii isolated from hospitalized patients

Carbapenem-resistant Acinetobacter baumannii (CRAb) is a priority pathogen, according to the World Health Organization (WHO), that is the most threatening to human health, being responsible for pneumonia, bacteraemia, urinary tract, skin and soft tissue infections, with mortality rates approaching 35%. The aim of this study was to evaluate the occurrence of colistin resistance (mcr1-5) and biofilm genes (surA1, bap, ompA, luxR, epsA) in 26 CRAb isolates collected from hospitalised patients and Acinetobacter baumanii ATCC 19606 as the reference strain. Gene prevalence was determined by multiplex or single PCR (polymerase chain reaction), in a 25 µL mixture (12.5 μL of REDTaq® ReadyMix™ PCR Reaction Mix, 1 μL of each primer, 2 μL bacterial DNA). As a result, 92.3% (24/26) and 96.2% (25/26) of the isolates were mcr1- and mcr3-positive, respectively. None of the isolates possessed the mcr2, mcr4 and mcr5 genes. All CRAb isolates had the surA1, bap, ompA and luxR genes, while 61.5% of isolates (16/26) harboured the epsA gene.

CRAb are highly pathogenic bacteria isolated from infections and are increasingly resistant to most available therapies. Every effort should be made to prevent the spread of these microorganisms, including analysing the presence of new genetic determinants in the CRAb genome, and identifying biofilm-related genes whose expression inhibition could more effectively eradicate these pathogens.