Damla Damar-Çelik1, Niels Nørskov-Lauritsen2, Berna Özbek-Çelik3. 1. Department of Pharmaceutical Microbiology, Faculty of Pharmacy, University of Istanbul, 34116 Fatih, Istanbul, Turkey. 2. Department of Clinical Microbiology, Aarhus University Hospital, DK-8200 Aarhus N, Denmark. 3. Department of Pharmaceutical Microbiology, Faculty of Pharmacy, University of Istanbul, 34116 Fatih, Istanbul, Turkey. Electronic address: berna.ozbek@istanbul.edu.tr.
Abstract
OBJECTIVES: Achromobacter xylosoxidans is an emerging pathogen in cystic fibrosis (CF). Relatively little is known about its clinical impact and optimal management. In the present study, the in vitro bactericidal activities of meropenem, either alone or in combination with colistin, levofloxacin, or chloramphenicol, were assessed using A. xylosoxidans strains isolated from CF patients. The synergistic interactions of these combinations were also investigated. METHODS: Minimal inhibitory concentrations (MICs) were determined by microbroth dilution. Bactericidal and synergistic effects of the tested antibiotic combinations were assessed by using the time-kill curve technique. RESULTS: Based on the time-kill curves, we found that meropenem-colistin combinations have bactericidal and synergistic activities for 24 h against A. xylosoxidans strains, both at 1 × MIC and 4 × MIC. Although synergistic interactions were seen with meropenem-levofloxacin combinations, no bactericidal interactions were observed. Additionally, the meropenem-chloramphenicol combinations were found to be neither bactericidal nor synergistic. No antagonism was observed with any combination tested. CONCLUSIONS: This study's findings could have important implications for empirical or combination antimicrobial therapy with tested antibiotics.
OBJECTIVES:Achromobacter xylosoxidans is an emerging pathogen in cystic fibrosis (CF). Relatively little is known about its clinical impact and optimal management. In the present study, the in vitro bactericidal activities of meropenem, either alone or in combination with colistin, levofloxacin, or chloramphenicol, were assessed using A. xylosoxidans strains isolated from CFpatients. The synergistic interactions of these combinations were also investigated. METHODS: Minimal inhibitory concentrations (MICs) were determined by microbroth dilution. Bactericidal and synergistic effects of the tested antibiotic combinations were assessed by using the time-kill curve technique. RESULTS: Based on the time-kill curves, we found that meropenem-colistin combinations have bactericidal and synergistic activities for 24 h against A. xylosoxidans strains, both at 1 × MIC and 4 × MIC. Although synergistic interactions were seen with meropenem-levofloxacin combinations, no bactericidal interactions were observed. Additionally, the meropenem-chloramphenicol combinations were found to be neither bactericidal nor synergistic. No antagonism was observed with any combination tested. CONCLUSIONS: This study's findings could have important implications for empirical or combination antimicrobial therapy with tested antibiotics.