title: In vitro activity of polymyxins in combination with β-lactams against clinical strains of Pseudomonas aeruginosa.
abstract: The emergence of multidrug-resistant (MDR) strains has made it difficult to treat infections caused by Pseudomonas aeruginosa. In order to develop new alternative therapies for the treatment of MDR P. aeruginosa infections, the antimicrobial activities of different antibiotic combinations have been studied in vitro and in vivo. In this study, the in vitro antimicrobial activities of six different combinations of polymyxins and β-lactams against 34 clinical isolates of P. aeruginosa were evaluated. For the combinations tested by the checkerboard method, an indifferent effect was observed for all strains. However, 27 strains (19 MDR) showed reductions in their minimal inhibitory concentration (MIC) for at least one of the antibiotics in the combinations evaluated. Combination with polymyxins resulted in reductions of the β-lactam MICs, with a change in the resistance category to susceptible in eight MDR strains. These results from the in vitro evaluation suggest that combinations of polymyxins and β-lactams may significantly reduce the MICs of the antibiotics tested. These combinations require further evaluation for use in medical practice.
authors.affiliation: Department of Basic Health Sciences, Universidade Estadual de Maringá, Avenida Colombo 5790, Maringá, PR, 87020-900, Brazil.
authors.forename: Cecília Saori
authors.initials: CS
authors.lastname: Mitsugui
authors.forename: Maria Cristina Bronharo
authors.initials: MC
authors.lastname: Tognim
authors.forename: Celso Luíz
authors.initials: CL
authors.lastname: Cardoso
authors.forename: Floristher Elaine
authors.initials: FE
authors.lastname: Carrara-Marroni
authors.forename: Lourdes
authors.initials: L
authors.lastname: Botelho Garcia
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003091:Colistin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004359:Drug Therapy, Combination; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D011113:Polymyxins / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D011113:Polymyxins; D047090:beta-Lactams; D003091:Colistin