Susceptibility of Aminoglycoside Resistant Acinetobacter baumannii to Antibiotic Combinations

Abstract

ACINETOBACTER baumannii (A. baumannii ) is considered one of the predominant antibiotic resistance pathogens involved in hospital acquired infections worldwide problem. The study investigated the effect of antibiotic combination of β-lactams (ceftriaxone, cefixime, carpabenem and impenim) and aminoglycosides against 5 clinical isolates of A. baumannii multidrug resistant. Over one year, 250 bacterial isolates were collected from 5 Egyptian hospitals from various infection sites. Two hundred out of 250 bacterial isolates were identified as A. baumannii based on phenotypic and genotypic techniques. The susceptibility of two-hundred A. baumannii strains against 21 different antibiotics was studied. The results showed that the highest resistance was to Cephalosporins, group was 99% followed by Quinolones & Fluoroquinolone was 90, 5 followed by penicillin 87.5, then Sulfa drugs was 75.5 then Carbapenem was 73 and finally Aminoglycosides was 60.5%. The minimum inhibitory concentration (MICs) values of aminoglycosides resistant A. baumannii strains ranged from 32 to >512mg/ml and β-lactam group ranged from 16 to >512mg/ml. Forty-five combined microtitre checkerboards were performed against the 5 totally aminoglycoside resistant A. baumannii strains to assess the potential for combination therapy. Combination of aminoglycoside antibiotics with β-lactams showed synergy action in thirty- eight (84%) of total forty-five combinations. Synergy was achieved with 100%, with the following combinations GN/IMP, GN/CRO, GN/CFM, AK/CRO, AK/CFM, TOB/CRO and TOB/CFM. No synergism was observed with combination between amikacin and imipenem.