Molecular Characterization of Putative Antibiotic Resistance Determinant and Virulence Factors Genes of Acinetobacter baumannii Strains Isolated from Intensive Care Unit Patients in Riyadh, Saudi Arabia

Multidrug resistance in Acinetobacter baumannii (A. baumannii) is a major global health threat. The resistance in A. baumannii is attributed to numerous factors, including antimicrobial resistance and virulence-determinant genes. Hence, the present study aimed to screen antibiotic resistance and virulence factors genes in 67 A. baumannii strains isolated from patients admitted to several hospitals in Riyadh City, Saudi Arabia. The A. baumannii isolates were confirmed by the VITEK-2 automated system and 16S rRNA phylogenetic relatedness. The phenotypic and genotypic resistance patterns of these isolates were also analyzed using conventional and molecular methods. Our finding showed that 94 % of isolated strains were MDR, and more than 94 % were resistant to the β-lactams group, particularly carbapenems, and the ciprofloxacin group. An intermediate resistance pattern was obtained with trimethoprim-sulfamethoxazole (71.6 %) and gentamicin (59.7 %). The lowest resistant patterns showed with colistin (5 %). The distribution of of resistance genes oxa-23, imp-like, oxa-24-like, tem, oxa-40, carb, oxa-58, floR, dfrA1 and qnrS were 100 %, 76.1 %, 64.1 %, 25.3 %, 23.8 %, 16.4 %, 14.9 %, 44.7 %, 5.9 % and 2.9 %, respectively. The distribution of virulence genes baP, pld, paaE, and surA1 was 98.5 %, followed by basD, traT, Omp33-36, and bauA were 97 %, 77.6 %, 74.4 %, and 64.1 %, respectively. The study showed a strong relationship between virulence factors, especially biofilm formation, and antibiotic resistance.