Investigation of Biofilm Formation, Virulence Genes and Antibiotic Resistance of Acinetobacter baumannii Isolates Obtained from Clinical Samples

The ability of Acinetobacter baumannii to form biofilms and its multiple antibiotic resistance may be responsible for the bacterium's survival in various environments. This study was aimed to investigate the biofilm-forming ability, antibiotic resistance phenotypes, frequency of genes associated with biofilm genes (bap, bap , omp A, aba I, csu E, bfm S), and integron genes (int1, int 1, int 2) in A. baumannii isolates obtained from human and bovine clinical samples. A total of 30 A. baumannii isolates were used, including 25 from human blood samples and 5 from mastitis-infected bovine milk samples. After conventional isolation methods, identification and antibiotic susceptibility tests were performed using an automated microbiology system (BD Phoenix (TM) 100, USA). Phenotypic biofilm formation was quantitatively assessed using the microplate test, and virulence genes associated with biofilm and integron genes were examined using polymerase chain reaction. Pearson's Chi-square (chi 2) test was used to compare the study data. The highest resistance rate among all isolates was observed against ampicillin, followed by ertapenem and cefepime. Ninety three percent of the isolates exhibited multidrug resistance (MDR), and all could form biofilms (60% strong, 27% moderate, 13% weak). All A. baumannii isolates carried at least one gene associated with biofilm formation. The most commonly observed virulence gene associated with biofilm was bfm S, followed by csu E, bap, , ompA A and aba I. Integron genes were detected in 90% of the isolates (23 from humans, 4 from bovines). Statistical analysis revealed no significant relationship between the origin of isolates and the severity of biofilm formation. However, significant associations were found between the origin of isolates and the presence of abaI I and bfmS S virulence genes, as well as between strong biofilm formation and carrying all virulence genes or integron genes. Analyses of isolates obtained from human and bovine clinical samples indicate that A. baumannii's 's biofilm formation capacity and resistance to antibiotics pose significant health threats. Particularly, the significant associations between strong biofilm formation and carrying all virulence genes or integron genes highlight the bacterium's complex adaptation strategies. In conclusion, this study demonstrates the comparative analysis of antimicrobial resistance profiles, biofilm formation abilities, and virulence gene carriage of A. baumannii isolates, emphasizing its importance as a threat to both human and animal health.