Effect of Antibiotic Consumption on Resistance of Pseudomonas aeruginosa Isolated from Lebanese Patients with Emphasis on MBL Production

Abstract

The relationship between antibioticconsumption and resistance has been widely evaluated. Pseudomonas aeruginosa isone of the most important opportunistic pathogens in the nosocomial setting,and its resistance to antibiotics is increaseing. Production of metallo-β-lactamases (MBLs) is currently themost fearful resistance mechanism due to the potential of dissemination. Thisstudy aimed to evaluate the correlation between antibiotic consumption (expressedin DDD/100 bed days) and resistance (expressed in % of isolates and patients)in different time periods for P. aeruginosa between 2006 and 2009 at SaintGeorge Hospital University Medical Center (SGH-UMC), Beirut. Pearsoncorrelation coefficients (r) were calculated and linear regression wasperformed. Detection of MBL-producing Imipenem resistant P. aeruginosa (IRPA)isolates between 2008 and 2009 was performed using three MBL screening methods:MBL Etest?, Imipenem/EDTA combined disk test and EDTA disk potentiation withfour cephalosporins. The modified Hodge test was also performed. From 2006 till2009, there was a trend of increasing resistance of P. aeruginosa to allantibiotics, and the highest % of resistance was for Ofloxacin. Concerningresistance expressed by isolates, high correlation coefficients resulted among Imipenem,Ciprofloxacin and Tazobactam consumption and resistance to these agents in thesame year correlation; Ceftazidime and Ofloxacin consumption and resistance inthe next year correlation; Gentamicin and Ofloxacin consumption and the changein resistance (ΔR). Concerning resistance expressed by patients, results weresimilar except for Ceftazidime and Ofloxacin correlation in the next yearcorrelation. In MBL screening, three isolates gave accordance among 4methods which showed a positive result. The correlation between antibioticconsumption and resistance is highly dependent on the kind of antibiotic, theorganism and the time of correlation. Various MBL screening phenotypic methodson one isolate can increase accuracy and eliminate false positive and negativeresults.