Abstract

The emergence of extreme drug resistant (XDR) Pseudomonas aeruginosa and Acinetobacter baumannii represent a major problem in health care settings. Colistin is the only therapeutic option available for treatment of infections caused by such pathogens. Worryingly, colistin resistance recently emerged which may lead to the return to the pre antibiotic era. The aim of the present study was to assess for the first time the bactericidal activity of four novel triple antibiotic combinations, including imipenem (IMP), amikacin (AK), cefepime (CEF) and tigecycline (TIG) against four XDR P. aeruginosa and A. baumannii clinical pathogens. Antibiotic combinations were evaluated by time-kill assay at the breakpoints. Three combinations (IMP/TIG/AK, TIG/AK/CEF and IMP/TIG/CEF) showed significant bactericidal activity against XDR A. baumannii isolates. Only two combinations (IMP/AK/CEF and IMP/TIG/AK) displayed remarkable killing against XDR P. aeruginosa isolates. These finding revealed that these triple antibiotic combinations are attractive therapeutic options for treatment of infections caused by XDR pathogens and could be utilized as an alternative to colistin. Further studies are warranted to assess the clinical outcomes of such combinations.

Key words: Extreme drug resistant (XDR), Pseudomonas aeruginosa, Acinetobacter baumannii, antibiotic combinations, bactericidal activity.