ABSTRACT
Acinetobacter baumannii is an opportunistic pathogen that causes healthcare-associated infections in hospitalised patients in intensive care units. A. baumannii can quickly develop resistance to antimicrobials through different mechanisms. Infections caused by multidrug-resistant (MDR) isolates have high morbidity and mortality and require long-term hospitalisation. Colistin is one of the last antimicrobials that can be used against MDR A. baumannii isolates. Due to the increase of these isolates, the use of colistin has increased worldwide. Our study aimed to investigate colistin resistance rates, minimum inhibitory concentration (MIC) values and plasmid-mediated resistance genes in isolates from the blood cultures of patients hospitalised in intensive care units.
A total of 97 A. baumannii isolates from blood culture samples were included in our study. MIC values of the isolates were investigated by the broth microdilution method according to The European Committee for Antimicrobial Susceptibility Testing recommendations. Colistin resistance gene regions mcr 1-5 were studied by polymerase chain reaction.
Eight (8.2%) of the A. baumannii isolates were resistant, and 89 (91.8%) were sensitive. The colistin MIC50 value was 0.5 μg/mL, and its MIC90 value was 2 μg/mL. The plasmid-mediated mcr gene regions (1-5 mcr genes) investigated for the risk of horizontal spread of colistin resistance could not be determined.
Colistin is an important antimicrobial that can still be used effectively to treat infections due to A. baumannii isolates in our intensive care units. However, to prevent the development of resistance against colistin, irrational antibiotic use should be prevented, and treatment according to antimicrobial susceptibility test results is required. In addition, we believe that it is important to take the necessary infection control measures to prevent the colonisation of resistant isolates in hospitals.
Keywords: Acinetobacter baumannii, colistin, intensive care units