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

Aims: Biofilm formation supports the persistence of Acinetobacter baumannii (A. baumannii) in hospital environments and can reduce antimicrobial effectiveness. Therefore, phenotypic and genotypic studies of this bacterium in intensive care units (ICUs), can be helpful in the control and containment of infection. This study aimed to investigate the phenotypic and genotypic characteristics of biofilm formation in Acinetobacter baumannii isolates obtained from ICUs.
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 the ompA, csuE and bap genes was determined by PCR.
Findings: Among the 81 patients, 42 (51.9%) were male and 39 (48.1%) were female. Piperacillin-tazobactam (96.3%, n=78/81) and imipenem (93.8%, n=76/81) showed the highest rates of resistance, and cefotaxime (56.8%, n=46/81), followed by gentamicin (46.9%, n=38/81), were the most susceptible antibiotics among the isolates. The ability to produce biofilm can be described as follows: 5 (6.17%) had no ability, while 76 (93.8%) were able to form biofilm. Moderate formation was the most common biofilm pattern (42 isolates, 51.85%), followed by weak (32, 39.50%) and strong formation (2, 2.47%). PCR detected bap, csuE, and ompA in 93.8%, 86.4%, and 82.7% of isolates, respectively.
Conclusion: Phenotypic and genotypic information on biofilm production in isolates commonly found in ICUs could strengthen infection-control measures and antimicrobial stewardship.