[Antibiotic resistance of Acinetobacter baumannii, Pseudomonas aeruginosa and Stenotrophomonas maltophilia in the University Hospital Olomouc in 2018-2023].

Due to increasing bacterial resistance to a wide range of antibiotics, there is a renaissance of colistin, an old polymyxin antibiotic that was previously abandoned for its adverse effects and is now increasingly used worldwide as a reserve antibiotic, especially in intensive care patients. Given the global increase in the prevalence of multidrug-resistant bacteria, this study focuses on secondary colistin resistance in clinically significant gram-negative non-fermenting bacteria Acinetobacter baumannii, Pseudomonas aeruginosa and Stenotrophomonas maltophilia at the University Hospital Olomouc in 2018-2023. According to the results of the present study, the prevalence of colistin-resistant isolates of Acinetobacter baumannii, Pseudomonas aeruginosa and Stenotrophomonas maltophilia at the hospital was 1 %, 2 % and 45 %, respectively, with none of the species showing an increasing trend over the six-year period. Additionally, no increase in the prevalence of multidrug-resistant and extensively drug-resistant isolates was observed in colistin-resistant gram-negative non-fermenting bacteria. The highest proportion of colistin-resistant Stenotrophomonas maltophilia strains was detected in departments providing the highest level of acute intensive care, which correlates with the nature of these facilities. Colistin consumption peaked in the COVID-19 year 2021, but returned to its original level by the end of the study period. In the selected set of colistin-resistant Pseudomonas aeruginosa isolates, no plasmid-mediated mcr 1-5 genes were detected. A significant finding was the detection of clonal spread of colistin-resistant Pseudomonas aeruginosa strains between acute admission and intensive care units, em-phasizing the need for strict adherence to preventive measures in these departments.