Association Between Antibiotic Resistance Patterns and Analysis of Virulence Genes in Multi-drug Resistant <i>Acinetobacter baumannii</i> in Iran (2018)

Background: Acinetobacter baumannii is one of the pathogens considered highly potent for developing multi-drug resistance (MDR) isolates. Several groups of virulent genes have been identified as involved in the development of MDR isolates of A. baumannii. Objectives: In this study, we aimed to detect the "outer membrane components" genes, including lipopolysaccharide biotinylated (LpsB), outer membrane protein A (OmpA), capsule (Cap), phospholipase (PLD), and type VI secretion system (T6SS), in MDR A. baumannii samples collected from different cities around Iran and find their relationship with resistance to different antibiotics. Methods: This cross-sectional study was performed on 50 A. baumannii identified by microbiological and biochemical assays. The blaOXA-51 gene in PCR confirmed their identification. Antibiotic susceptibility testing was used for MDR strain identification. Phenotypic and molecular assays identified the active efflux pumps. PCR detected OmpA, T6SS, Cap, LpsB, and PLD as virulence genes. Results: A total of 50 valid data points were analyzed, of which 62.0% were related to males. The mean age of participants was 51.82, and 61.5% of patients were hospitalized in ICUs. 59.2% of samples were collected from the tracheobronchial tract. The samples' frequency of OmpA, T6SS, Cap, LpsB, and PLD genes was 50%, 92%, 56%, 96%, and 92%, respectively. The MDR samples were 100% resistant to cefepime (CPM), cefotaxime, ceftazidime (CAZ), imipenem (IPM), meropenem (MEM), and piperacillin/tazobactam (PTZ); and least resistant to colistin, minocycline (MN; 20%, 64% respectively). The carbonyl cyanide m-chlorophenyl hydrazine (CCCP) test was positive in 26% of strains, and an increase in AdeB gene expression was observed in 46% of them. Conclusions: The presence of "outer membrane components" virulent genes in MDR A. baumannii is considerably high. Also, the presence of these genes was mostly related to resistance to CPM, cefotaxime, CAZ, IPM, MEM, and PTZ antibiotics, but less related to resistance to colistin and MN.