Background: Acinetobacter baumannii (A. baumannii) has globally emerged as an important pathogen in hospital-acquired infections. Bacterial pathogenesis is associated with numerous virulence factors, such as colonization, invasion, biofilm formation, antimicrobial resistance, etc. The study investigated the antibiotic susceptibility pattern, biofilm formation capabilities, and presence of virulence genes in clinical isolates of A. baumannii.
Materials and Methods: Out of 115 collected isolates, 32 carbapenem-resistant biofilm-forming extensively drug-resistant A. baumannii (XDR-AB) were included in this study. The isolates were identified by VITEK 2 and confirmed by polymerase chain reaction (PCR) targeting the blaOXA-51 gene. Antibiotic susceptibility pattern was determined by VITEK 2. All the isolates were examined for biofilm formation using the tube method, and PCR was performed to detect virulence genes.
Results: All study isolates were carbapenem-resistant XDR-AB and showed a high resistance rate (84.38%-100%) to most of the antibiotics except colistin and minocycline. Biofilm formation was documented in 100% (32/32) of isolates and categorized as strong, moderate, and weak biofilm formation in 7 (21.88%), 12 (37.5%), and 13 (40.62%) isolates, respectively. Out of 32 isolates, 30 (93.75%) harbored virulence genes, including Bap (30, 93.75%), OmpA (29, 90.62%), cnf1 (7, 21.87%), and csgA (5, 15.62%). The study also reported the presence of multiple genes in a single isolate (30/32, 93.75%).
Conclusion: The study highlights that colistin and minocycline are effective antibiotics for treating carbapenem-resistant biofilm-forming XDR-AB infections, which can be included in our hospital antibiotic policy. However, the combination therapy of colistin with minocycline can have better results compared to monotherapy. Nearly one-fourth (21.88%) of the biofilm-forming isolates were strong biofilm producers. The study also documented a high prevalence (93.75%) of virulence genes and the existence of genetic heterogeneity in study isolates that can trigger further dissemination of the gene. Therefore, molecular surveillance of local isolates for the virulence factor genes is crucial for containing transmission, diseases, and outbreaks.
Keywords: Acinetobacter baumannii, Hospital-acquired infections, Antibiotic resistance, Biofilm, Virulence genes.
