Efflux MexAB-Mediated Resistance in P. aeruginosa Isolated from Patients with Healthcare Associated Infections.

Today, one of the most important challenges for physicians is the adequate treatment of infections due to multidrug resistant organism (MDR). Pseudomonas aeruginosa is considered an opportunistic organism causing different types of healthcare associated infections (HAIs). We aimed to investigate the MDR and pandrug resistance (PDR) rate in P. aeruginosa in our region and detect efflux-pump mexAB genes and the proposed binding interactions of five different categories of antimicrobial agents with the mexB pump. A total of 180 non-duplicated P. aeruginosa strains were isolated from patients with HAIs in the Suez Canal University Hospital. Phenotypically, minimum inhibitory concentration (MIC) was done for all MDR and PDR strains before and after addition of efflux pump inhibitor carbonyl cyanide m-chlorophenyl hydrazone (CCCP). Molecular detection of mexA and mexB genes was done by using polymerase chain reaction (PCR). Most of the isolated strains (126 strains) were MDR (70%); only 10 samples (5.5%) were PDR. MexA and mexB genes were detected in 88.2% (120 strains) and 70.5% (96 strains) of stains, respectively. All PDR strains (10 stains) carried both mexA and mexB genes. Efflux mexAB genes were detected in all MDR and PDR strains (136 strains). Molecular modeling studies were performed to investigate the modes of intermolecular binding interactions between the antimicrobial agents and mexB key amino acids that resulted in MDR and PDR. The current study reported high prevalence of MDR and PDR P. aeruginosa in patients with HAIs in the Suez Canal University Hospitals.