DIFFERENT VIRULENCE CAPABILITY AND PATHOGENIC STRATEGY AMONG CLINICAL ISOLATES OF MULTI-DRUG RESISTANT ACINETOBACTER BAUMANNII

Background and Aim:Acinetobacter baumannii causes a variety of nosocomial infections. Serum resistance and antimicrobial resistance are two major capabilities of A. baumannii to establish its infections in patients.Methods:Fifty clinical isolates of multi-drug resistant (MDR) A. baumannii were analyzed for clonal relatedness, serum resistance and in vivo assays.Also, some virulence genes, sequence variation of ompA and its expression were studied.Results:The MLST results showed that there were three sequence types among MDR isolates including ST2 (64%, 32/50), ST513 (30%, 15/50) and ST1 (6%, 3/50). Whereas, all isolates recovered from host interior fluids had high serum resistance. The results of PCR assays and in silico analysis represented that the patterns of virulence genes and ompA variations among MDR isolates were clonally dependent. The in vivo analysis showed that the selected strains differently proliferated in spleen of C57/BL6 mice. Strains causing bacteremia in mice induced higher and significant level of IL-6 in serum compared to isolates without bacteremia capability. qRT-PCR analysis showed that bacteremia producing strains significantly overexpress ompA matched to the level of IL-6 in bloodstream of mice and its expression is clonally independent. Interestingly, AB-38 and AB-40 strains efficiently released in bloodstream, while they had low Log10 CFU/g scores during spleen colonization (4.69 and 4.1, respectively).Conclusion:Our data showed that the patterns of virulence genes strongly related to MLST sequence types. Whereas the virulence traits of clinical isolates were clonally independent.

کلیدواژه ها:

Acinetobacter buamanii ، serum resistance ، In vivo