<it>In-vitro </it>activity of polymyxin B in combination with imipenem, rifampicin and azithromycin versus multidrug resistant strains of <it>Acinetobacter baumannii </it>producing OXA-23 carbapenemases
<p>Abstract</p> <p>Background</p> <p><it>Acinetobacter baumannii </it>has emerged as a major nosocomial pathogen worldwide. Many of the circulating strains exhibit multi-drug resistance remaining consistently susceptible only to polymyxins. <it>In-vitr...
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BMC,
2006-04-01T00:00:00Z.
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| Summary: | <p>Abstract</p> <p>Background</p> <p><it>Acinetobacter baumannii </it>has emerged as a major nosocomial pathogen worldwide. Many of the circulating strains exhibit multi-drug resistance remaining consistently susceptible only to polymyxins. <it>In-vitro </it>studies have reported that polymyxins combined with carbapenems, rifampicin or azithromycin are synergistic against these strains despite <it>in-vitro </it>resistance to these agents alone. The use of antimicrobial combinations have therefore been advocated for the treatment of severe <it>A. baumannii </it>infection in man. In order to determine whether such combinations are synergistic against the prevalent clones of multi-drug resistant <it>A. baumannii </it>causing infection in the UK, we performed synergy testing against representative isolates using two rapid Etest methods.</p> <p>Methods</p> <p>The activity of polymyxin in combination with imipenem, azithromycin or rifampicin was assessed against five strains of multi-drug resistant <it>A. baumannii </it>encoding OXA-23 carbapenemases. Synergy studies were performed by Etest-agar dilution and a combined Etest strip method. Synergy was defined as a FICI of ≤ 0.5.</p> <p>Results</p> <p>All strains were resistant to β-lactams, carbapenems, quinolones and aminoglycosides but susceptible to polymyxins. Marked synergy was not seen with polymyxin in combination with imipenem, rifampicin or azithromycin against any of the strains. Borderline synergy (FICI = 0.5) was seen against one strain belonging to OXA-23 clonal group 2, using the Etest-agar dilution method only.</p> <p>Conclusion</p> <p><it>In-vitro </it>synergy with polymxyin in combination with imipenem, rifampicin or azithromycin is highly strain and method dependent. As reliable synergy could not be demonstrated against the prevalent UK multi-drug resistant strains, use of such combinations should not be used for empirical treatment of these infections in the UK. The optimal treatment for serious multi-drug <it>A. baumannii </it>infection and the role of combination therapy should be addressed in a prospective clinical trial.</p> |
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| Item Description: | 10.1186/1476-0711-5-10 1476-0711 |