OBJECTIVETo investigate the prevalence of aminoglycoside resistance and genotyping of acetyltransferase in Escherichia coli.

METHODSResistance phenotypes to 12 antibiotics of 44 Escherichia coli isolates were analyzed using agar dilution method and 3 aminoglycoside resistance genes aac(3)-I, II and aac(6')-I were determined by PCR method.

RESULTSIn 44 clinical isolates, the occurrence of ESBLs was 45.45%, resistance rates were discrepant for amikacin (18.18%), gentamicin (56.82%) and tobramycin (61.36%), the prevalence of phenotype TG (tobramycin and gentamicin) indicative of aac(3)-II production and TGA (tobramycin, gentamicin and amikacin) indicative of aac(6')-I production were 36.36% and 18.18%, respectively. The most common aminoglycoside resistance genotype of acetyltransferase was aac(3)-II (52.27%) and aac(6')-I was lower (29.55%), but no aac(3)-I was detected.

CONCLUSIONAt least 2 acetyltransferase genes exist in this area i.e. aac(3)-II and aac(6')-I.

Acyltransferases ; genetics ; Amikacin ; pharmacology ; Aminoglycosides ; pharmacology ; Drug Resistance, Bacterial ; genetics ; Escherichia coli ; enzymology ; genetics ; Genotype ; Gentamicins ; pharmacology ; Phenotype ; Tobramycin ; pharmacology

PURPOSE: Combination antibiotic treatment is preferred in nosocomial infections caused by Pseudomonas aeruginosa (P. aeruginosa). In vitro synergism tests were used to choose the combinations which might be used in clinic. The aim of this study was to investigate the synergistic efficacy of synergistic antibiotic combinations in multidrug resistant P. aeruginosa strains. MATERIALS AND METHODS: Synergistic efficacies of ceftazidime-tobramycin, piperacillin/tazobactam-tobramycin, imipenem-tobramycin, imipenem-isepamycin, imipenem-ciprofloxacin and ciprofloxacin-tobramycin combinations were investigated by checkerboard technique in 12 multiple-resistant and 13 susceptible P. aeruginosa strains. RESULTS: The ratios of synergy were observed in ceftazidime-tobramycin and piperacillin/tazobactam-tobramycin combinations as 67%, and 50%, respectively, in resistant strains, whereas synergy was not detected in other combinations. The ratios of synergy were observed in ceftazidime-tobramycin, piperacillin/tazobactam-tobramycin, imipenem-tobramycin, imipenem-ciprofloxacin and imipenem-isepamycin combinations as 31%, 46%, 15%, 8%, 8%, and respectively, in susceptible strains, whereas synergy was not detected in ciprofloxacin-tobramycin combination. Antagonism was not observed in any of the combinations. CONCLUSION: Although the synergistic ratios were high in combinations with ceftazidime or piperacillin/tazobactam and tobramycin, the concentrations in these combinations could not usually reach clinically available levels. Thus, the solution of the problems caused by multiple resistant P. aeruginosa should be based on the prevention of the development of resistance and spread of the causative agent between patients.
Anti-Bacterial Agents/*pharmacology ; Ceftazidime/pharmacology ; Ciprofloxacin/pharmacology ; Drug Resistance, Multiple, Bacterial/*drug effects ; Drug Synergism ; Imipenem/pharmacology ; Microbial Sensitivity Tests ; Penicillanic Acid/analogs & derivatives/pharmacology ; Piperacillin/pharmacology ; Pseudomonas aeruginosa/*drug effects ; Tobramycin/pharmacology