Changes in Susceptibility Profiles of Acinetobacter baumannii Clinical Isolates in a Multi-Profile Hospital in Years 2020-2024 in Lodz, Poland.

Background

Acinetobacter baumannii is a non-fermenting Gram-negative bacillus responsible for severe nosocomial infections, particularly in intensive care units (ICUs). The increasing prevalence of multidrug-resistant (MDR) and carbapenem-resistant A. baumannii (CRAB) strains has become a significant challenge for infection control and antimicrobial therapy worldwide.

Objectives

This study aimed to analyze the antimicrobial susceptibility patterns of clinical A. baumannii isolates recovered from a multi-profile hospital in years 2020-2024 in Lodz, Poland.

Methods

Clinical isolates from various specimen types (blood, urine, wound swabs, biopsies, sputum, and bronchoalveolar lavage fluid) were obtained during routine microbiological diagnostics. Identification was performed using MALDI-TOF MS. Antimicrobial susceptibility testing (AST) was conducted using the automated VITEK®2 system with EUCAST/CLSI interpretive criteria. Minimum inhibitory concentrations (MICs) for colistin were determined by broth microdilution. Carbapenemase production was assessed using the Carbapenem Inactivation Method (CIM) and immunochromatographic assays for OXA-23, OXA-40/58, and NDM detection.

Results

A total of 244 A. baumannii isolates were recovered over the study period. Susceptibility to carbapenems (meropenem, imipenem) declined markedly, with resistance exceeding 90% by 2023-2024. Aminoglycosides exhibited variable activity, with gentamicin demonstrating the highest susceptibility rates (up to 88% in 2022). Resistance to ceftazidime and cefepime remained consistently high (>90% in 2023-2024). No fully susceptible isolates were identified for ciprofloxacin.

Conclusions

The high prevalence of CRAB strains highlights the urgent need for effective infection control measures, optimized antimicrobial stewardship, and consideration of novel treatment options in the clinical setting.