Dataset MDR A. baumannii y2020m01d30

Efflux pump expression in MDR Acinetobacter baumannii strains from a tertiary care hospital in Lima, Peru

ABSTRACT

Background: Acinetobacter baumannii is an important nosocomial opportunistic pathogen worldwide and causes ventilator-associated as well as bloodstream infections in critically ill patients, with mortality rates between 10 and 43%. Express several resistance mechanisms, including the production of β-lactamases, changes in cellular membrane and production of efflux pumps. These latter represent an important factor for development of multidrug resistance against aminoglycosides, fluoroquinolones, tetracyclines, erythromycin, chloramphenicol, trimethoprim and some beta-lactams. In order to evaluate the role of this latter resistance mechanism efflux pumps inhibitors have been widely tested.

Methods: Acinetobacter spp. were identified by BD Phoenix ™ automated system and A. baumannii strains were detected by amplification of the blaOXA-51 gene by PCR. Antimicrobial susceptibility to fluoroquinolones and aminoglycosides was assessed by broth microdilution technique, according to CLSI guidelines. The activity of the efflux pumps system was assessed by the addition of phenylalanine inhibitor of arginine-β-naphthylamide (PAβN). Efflux pump expression was detected by the measurement of MIC with and without inhibitors decreasing the MIC values in 4-fold dilutions. Patients information was coded to avoid identification and their characteristics were assessed from their clinical records.

Results: A total of nineteen Acinetobacter baumannii strains were included in the study. All were positive for the blaOXA-51 gene by PCR and had clinical information associated. The samples were non-duplicate and collected from different sources. Non-susceptibility rates were as following: tobramicin (6, 31.6%), ciprofloxacin (6, 31.6%), levofloxacin (4, 21.1%), nalidixic acid (5, 26.3%) and amikacin (3, 15.8%). A total of eight strains (42,1%) demonstrated an increase in the susceptibility rates and sixteen (84,2%) expressed efflux pumps.

Conclusions: In the present study, the decrease in antimicrobial resistance against quinolones and aminoglycosides was demonstrated by the addition of the PABN, acting as efflux pump inhibitor. Therefore, efflux pumps still have an important role in the emergence of multi-drug resistant strains of A. baumannii. Efflux pump inhibitors may be useful as a complementary therapy for this pathogen as further research should evaluate.