Phenotypic and genotypic study of biofilm formation in Acinetobacter baumannii isolated from intensive care units

Background: Biofilm formation supports the persistence of Acinetobacter baumannii in hospital environments and could reduce antimicrobial effectiveness. Therefore, phenotypic and genotypic studies of this bacterium in intensive care units
(ICUs) could be helpful in controlling and containing infection. This study aimed to investigate the phenotypic and genotypic characteristics of biofilm formation in A. baumannii isolates from ICUs.
Materials & Methods: Between March and September 2021, 81 sputum-derived A. baumannii isolates were recovered from ICU patients. Species confirmation was performed by polymerase chain reaction (PCR) targeting the blaOXA-51-like gene. Antibiotic susceptibility testing was used to determine the phenotypic resistance pattern. Biofilm formation was assessed phenotypically for all isolates. The presence of ompA, csuE, and bap genes was determined by PCR.
Findings: Of the 81 patients, 42 (51.9%) were male, and 39 (48.1%) were female. Piperacillin-tazobactam (96.3%, n=78) and imipenem (93.8%, n=76) showed the highest resistance rates, while cefotaxime (56.8%, n=46) and gentamicin (46.9%, n=38) were the most effective antibiotics against the isolates. The biofilm formation ability could be described as follows: five (6.17%) isolates had no ability, while 76 (93.8%) isolates were able to form biofilm. Moderate biofilm formation was the most common biofilm pattern (n=42, 51.85%), followed by weak biofilm (n=32, 39.50%) and strong biofilm (n=2, 2.47%). Also, bap, csuE, and ompA were detected
in 93.8, 86.4, and 82.7% of the isolates by PCR, respectively.
Conclusion: Phenotypic and genotypic information on biofilm formation ability of commonly-found isolates in ICUs could strengthen infection control measures and antimicrobial stewardship programs.