Performance of direct rapid antimicrobial susceptibility testing on urine

Abstract

Urinary tract infections (UTIs) are a medical threat with the high morbidity of 150 million people worldwide a year. UTIs like other infections are treated with the broad-spectrum antibiotics which consequently leads to the increase of resistances and the conventional method for the diagnosis of urinary tract infections takes 48-72h for the identification of the bacteria and antimicrobial susceptibility testing (AST) results to be available to the physicians. Hence the rapid AST would increase the adequate choice of antibiotics for the better outcome of the patients. Therefore, our study aimed to demonstrate that AST can be performed directly on urine samples using the disk diffusion method within 8 hr’ incubation. A total of 103 urine samples containing ≥ 2.104 bacterial/ml and monobacterial (Enterobacteriaceae) after gram staining was tested using disk diffusion method with 8 hr’ incubation. And the results were compared to the standardized VITEK-2 AST. We compared the categorical agreements and the correlation between both methods. Over the 1545 tested drug combinations in all isolates studied, the overall categorical agreement of the direct rapid disk diffusion and the standardized susceptibility testing using VITEK-2 was 92.9%, with 4.9% minor errors, 0.9% major error 1.2% very major errors. Our results showed an excellent categorical agreement and correlations between diameters for dRAST and VITEK-2 susceptibility. The direct rapid AST on urine containing monobacterial Enterobacteriaceae can predict the reliable result of AST within 8 hr. The rapid AST reports by using DST in UTIs can facilitate the timely and adequate antimicrobial treatment.