The influence of glucose added urine on the in vitro antimicrobial activity of various antibiotics.

BACKGROUND & OBJECTIVE Factors associated with the medium, including calcium and magnesium ion concentration and pH have been shown to affect the results of susceptibility testing but very little is known about glycosuria and the effect of glucose on the antimicrobial effect of antibiotics. In this study we assessed the influence of glucose added urine on the in vitro activities of various antibiotics by the microbroth dilution method. METHODS Sixteen Escherichia coli isolates from patients with urinary infections were used in this study. Nine antibiotics were tested for their antimicrobial activity. Minimum inhibitory concentrations (MICs) were performed by the microbroth dilution method parallel in Mueller Hinton broth and glucose added urine. RESULTS MICs of nearly all antibiotics were higher in glucose added urine than MICs in broth. MIC(90) against ampicillin was 32-fold higher in glucose added urine than MIC(90) in broth. MIC(90)s against ampicillin-sulbactam, cephalothin, cefuroxime, ceftriaxone and ciprofloxacin in glucose added urine were significantly (P<0.05) higher than MIC(90) in broth. Equal MIC(90) in glucose added urine and broth were obtained for amikacin, sulphamethoxazole and trimethoprime. INTERPRETATION & CONCLUSION Our findings demonstrated that MICs of antibiotics are influenced by the glucose added urine.