Antimicrobial Synergy Testing By Time-Kill Methods For Extensively Drug-Resistant Acinetobacter Baumannii Isolates.
Journal Title: IOSR Journal of Dental and Medical Sciences (IOSR-JDMS) - Year 2017, Vol 16, Issue 12
Abstract
Introduction:The emergence of colistin or tigecycline resistance as well as imipenem resistance in Acinetobacter baumannii poses a great therapeutic challenge. Increasing reports of polymyxin heteroresistance have suggested that rapid resistance to polymyxins can develop upon treatment with polymyxin B monotherapy, especially upon exposure to subtherapeutic polymyxin concentrations. To circumvent this phenomenon, experts have advocated that polymyxins should be used in combination with one or more antibiotics for the treatment of carbapenem resistant isolates. Aims & Objectives: The aim of this study is to assess the in vitro activity of different combinations of polymyxin B, rifampicin, meropenem and tigecycline against selected clinical isolates of A. baumannii . Materials & Methods: Twelve representative imipenem-resistant A.baumannii clinical isolates were included in present study. Minimal inhibitory concentration (MIC) was determined using agar dilution method according to Clinical and Laboratory Standards Institute (CLSI) guideline.Time-kill studies were performed on four antimicrobial agents and combinations of these agents according to a previously reported method. Results: Only polymyxin-B was consistently effective as a single agent against all 12 isolates, but showed bacterio-static activity when used singly. Among the combinations of 0.5 x MIC antimicrobial agents, the combination of polymyxin-B and tigecycline showed synergistic or bactericidal effects against 8 of the isolates. Antimicrobial combinations are effective for killing imipenem-resistant A. baumannii isolates, even if they are simultaneously resistant to either carbapenems or tigecycline. Discussion & Conclusions: The Time-kill assay method used in this study can be used for individualized treatment of patients suffering from critical infections caused by extremely drug resistant Acinetobacter isolates. The use of these lower MIC values obtained from synergy studies can be as a guide to determine effective individualized therapeutic doses can help to decrease the emergence of resistance and can also minimize the side effects associated with using a single agent at a higher dose.
Authors and Affiliations
Simit Kumar, Maitreyi Bandyopadhyay, Mohiruddin Sk, Prabir Kumar Mukhopadhyay, Manas Kumar Bandyopadhyay, Anindita Chatterjee, Mitali Chatterjee
Keywords
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- EP ID EP251511
- DOI 10.9790/0853-1612107984
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