Molecular Analysis of Whole Genomic Sequencing for Acinetobacter Baumannii Isolates under Antibiotic Stress in a Hospital Outbreak

Abstract

A study was conducted to identify specialised genes in two types of Acinetobacter baumannii, namely MDR, XDR, and PDR. These genes may play a crucial role in the ability of these species to coexist with the human host and show a wide range of diversity in genes that contribute to antibiotic resistance and lipopolysaccharide barrier.Methodology: The identification of 70 A. baumannii isolates was carried out through morphology and culture on CHROM agar, followed by biochemical testing. Genotypic identification was performed using 16S rRNA and blaOxa-51 gene for A. baumannii species. Based on the antibiotic resistance categories, two isolates (AB32 and AB51) were selected for whole genome sequencing (WGS) using Illumina MiSeq technology. The analysis identified specialised genes in these isolates that contribute to antibiotic stress and lipopolysaccharide barrier, including complex sets of partial and complete integrons and transposons. Results:The recent findings showed that A. baumannii exhibits the highest resistance to gatifloxacin. The genome analysis revealed that AB3, AB32, and AB51 belong to unique STs (ST/1418, and ST/441), while AB R75 belongs to a known international clone of a high-risk strain (ST/195). The presence of efflux pump genes EmrAB-TolC, MacA, MacB, MdfA/ Cmr, TolC/ OpmH, and atG catalase gene encoding an antibiotic activation enzyme was identified in the WGS results. In addition, antibiotic target protection and replacement proteins that confer resistance against gatifloxacin and colistin sulphates were encoded by BcrC, FabG, and HtdX genes.Conclusions: Our study provided a detailed genomic picture of both innate and acquired plasmid-encoded AMR genes.