Molecular Epidemiology Revealed Distinct Patterns Among Multidrug Resistant Clinical <i>Acinetobacter baumannii</i> Strains in Different Periods in the Main Hospital in Molise Region, Central Italy

Abstract

Background: Acinetobacter baumannii is a major cause of nosocomial infections in critically ill patients, and strains are frequently multidrug resistant (MDR). This study aimed to characterize 45 clinical A. baumannii isolates collected in different periods in the main hospital in the Molise Region, central Italy. Methods: Antimicrobial susceptibility was evaluated using an automated system, and PCRs were performed to detect resistance-associated genes. Pulsed-field gel electrophoresis (PFGE) was carried out with AscI and ApaI, and Multi-locus sequence typing (MLST) was performed according to the Oxford scheme. Results: All isolates exhibited MDR profiles, showing total susceptibility towards colistin. All strains harbored the blaOXA-23, blaOXA-51, and blaAmpC genes, as well as adeB, adeJ, adeG, abeS, and soxR. Dendrogram with AscI and ApaI revealed eleven and three clusters, respectively, and twenty-three and eighteen pulsotypes (Simpson’s index 0.96 and 0.93), and isolates from different periods were clearly distinguished. MLST revealed five sequence types, which varied depending on the isolation period, and ST1720 and ST369 were prevalent, followed by ST281, ST218, and ST513. Conclusions: Molecular characterization enables the identification of distinct patterns of MDR A. baumannii over time, underscoring its usefulness for improving epidemiological surveillance and combating antimicrobial resistance. This study provides previously unavailable information regarding A. baumannii circulating in the examined setting.

Keywords

• <i>Acinetobacter baumannii</i>
• antimicrobial resistance
• pulsed-field gel electrophoresis
• resistance genes
• sequence types