<b>The in vitro antimicrobial effect of polymyxin B associated with ceftazidime in pseudomonas aeruginosa clinical isolates</b> - DOI: 10.4025/cienccuidsaude.v7i0.6569

Abstract

The antibiotics association is an alternative to treat infectious diseases, either caused by polymicrobial etiology or those caused by multidrug-resistant bacteria, such as Pseudomonas aeruginosa. In this study, the in vitro antimicrobial activity of the polymyxin B and ceftazidime combination was investigated in 20 clinical isolates of P. aeruginosa. Initially, the minimum inhibitory concentration (MIC) of those agents was determined by using the broth microdilution technique for each of the selected strains. Afterwards, based on MIC values, the antimicrobial effect of the polymyxin B and ceftazidime combination was evaluated by making use of "checkerboard" method. The results demonstrated that all P. aeruginosa strains studied were sensitive to polymyxin B, with MICs varying from 1 to 2 µg/ml. In relation to ceftazidime, MICs varied from 2 to 8 µg/ml in nine sensitive strains, and from 16 to 1.024 µg/ml in 11 strains resistant to that antibiotic. For all strains tested, the antimicrobial effect of the polymyxin B and ceftazidime combination was indifferent, thus suggesting that such an association, when used as a combined in vivo therapy, sometimes does not present any activity superior to the one obtained with monotherapy.