Colistin Induced Assortment of Antimicrobial Resistance in a Clinical Isolate of Acinetobacter baumannii SD01

Abstract

: Colistin was considered as one the most effective antibiotic against Acinetobacter baumannii, a widely-known opportunistic pathogen. In recent years, a number of colistin resistant strains have also been reported. This work is commenced to investigate the contribution of efflux pumps toward resistance to colistin-like cyclic polypeptide antibiotics, as the efflux pumps serve as the escape routes leading to drug-resistance. RNA was extracted from A. baumannii isolates cultured from samples procured by tracheal aspiration of infected patients. The expression of gene(s) that played major roles in the regulation of efflux pump families and involvement of integron systems were studied using real time PCR. Antimicrobial susceptibility tests were conducted to test antibiotic resistance of the isolate. It was observed that genes coding for sugE, ydhE, ydgE, mdfA, ynfA and tolC significantly contributed to resistance against colistin antibiotics, however, no significant transcriptional change was observed in the efflux pump, MexAB-OprM. Results suggest that A. baumanii readily pumps out colistin via efflux pumps belonging to MATE and SMR family. Integral role of efflux pumps and integron 1 genetic system was elucidated towards evolution of multi-drug resistant strain(s). Therefore, for accurate therapeutics, an early detection of efflux genes is crucial before prescribing against colistin resistant A. baumanii.

Acinetobacter baumannii Antibiotic Resistance Mechanisms

“…Moreover, mutations in pheS that encodes phenylalanine-tRNA ligase subunit alpha seem to play a role in colistin resistance [ 164 ]. Beyond the two aforementioned ABC transporters, and as stated before in text, overexpressed RND efflux pump MexAB-OprM correlates with colistin resistance [ 156 , 165 ].…”

“…RND efflux pump MexAB-OprM consists of MexA (the membrane fusion protein), MexB (the carrier located in the inner membrane), and OprM (the transporter positioned in the outer membrane). MexAB-OprM associates with lack of susceptibility to most antibiotics, including trimethoprim and even colistin, when expressed in high levels [ 156 , 165 ]. As mentioned above in text, efflux pumps AdeIJK and LmrS confer resistance to trimethoprim [ 148 ].…”

Article Review: Acentobacter bummanii

“…OmpW has cytotoxic effect towards cells in the host that is implicated in innate tolerance to different ecological stressors. A. baumannii's OmpW mutation decreased adhesion production or hindered the bacterium's capacity to attach to as well as invade A549 cell [70][71]. Furthermore, another research utilizing a rodent intraperitoneal septic paradigm found that a deletion in OmpW had no impact in sensitivity to various medications.…”

Antimicrobial Resistance in Romania: Updates on Gram-Negative ESCAPE Pathogens in the Clinical, Veterinary, and Aquatic Sectors

“…Polymyxins (colistin and polymyxin B) are last-resort antibiotics reintroduced into clinical practice to treat infections caused by MDR Gram-negative bacteria resistant to carbapenems. Resistance to polymixins occurs due to mutations in chromosomal genes involved in lipopolysaccharide structure (mgrB, pmrABC, lpxACD), plasmid-mediated LPS modification (mcr genes), or active efflux [216][217][218][219][220][221][222][223].…”