Open AccessInvolvement of the AcrAB-TolC Efflux Pump in the Resistance, Fitness, and Virulence of Enterobacter cloacae
Author(s) -
Astrid Pérez,
Margarita Poza,
Ana Fernández,
María del Carmen Fernández,
Susana Mallo,
María Merino,
Soraya RumboFeal,
María P. Cabral,
Germán Bou
Publication year - 2012
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.05509-11
Subject(s) - efflux , enterobacter cloacae , biology , microbiology and biotechnology , virulence , antibiotics , antibiotic resistance , multiple drug resistance , mutant , enterobacteriaceae , gene , escherichia coli , genetics
Multidrug efflux pumps have emerged as important mechanisms of antimicrobial resistance in bacterial pathogens. In order to cause infection, pathogenic bacteria require mechanisms to avoid the effects of host-produced compounds, and express efflux pumps may accomplish this task. In this study, we evaluated the effect of the inactivation of AcrAB-TolC on antimicrobial resistance, fitness, and virulence inEnterobacter cloacae , an opportunistic pathogen usually involved in nosocomial infections. Two different clinical isolates ofE. cloacae were used, EcDC64 (multidrug resistance overexpressing the AcrAB-TolC efflux pump) and Jc194 (basal AcrAB-TolC expression). TheacrA andtolC genes were deleted in strains EcDC64 and Jc194 to produce, respectively, EcΔacrA and EcΔtolC and JcΔacrA and JcΔtolC knockout (KO) derivatives. Antibiotic susceptibility testing was performed with all isolates, and we discovered that these mechanisms are involved in the resistance ofE. cloacae to several antibiotics. Competition experiments were also performed with wild-type and isogenic KO strains. The competition index (CI), defined as the mutant/wild-type ratio, revealed that theacrA andtolC genes both affect the fitness ofE. cloacae , as fitness was clearly reduced in theacrA andtolC KO strains. The median CI values obtainedin vitro andin vivo were, respectively, 0.42 and 0.3 for EcDC64/EcΔacrA , 0.24 and 0.38 for EcDC64/EcΔtol C, 0.15 and 0.11 for Jc194/JcΔacrA , and 0.38 and 0.39 for Jc194/JcΔtolC . Use of an intraperitoneal mouse model of systemic infection revealed reduced virulence in bothE. cloacae clinical strains when either theacrA ortolC gene was inactivated. In conclusion, the structural components of the AcrAB-TolC efflux pump appear to play a role in antibiotic resistance as well as environmental adaptation and host virulence in clinical isolates ofE. cloacae .