Evaluation of HB&L Uroquattro System for Rapid Antimicrobial Susceptibility Testing Directly from Positive Urine Samples

The aim of the study was to evaluate the concordance of the rapid antimicrobial susceptibility testing (AST) results obtained by the HB&L Uroquattro instrument performed directly from positive urine sam¬ples in comparison with the standard Kirby-Bauer disk-diffusion method performed with isolated colonies. We included 122 urine samples defined as positive by the HB&L system screening method. The AST was performed directly from them by the HB&L instrument. Simultaneously, all positive urine samples were cultured on CLED, MacConkey and Blood agar and incubated for 24h at 37°C. Species identification and AST of the pathogens isolated on solid media were done by the VITEK 2 automated system (bioMerieux) and respectively by the Kirby-Bauer disk-diffusion method. We defined one hundred and twenty-two pos¬itive urine samples:60 Enterobacterales, 42 Enterococcus faecalis, and 20 Staphylococcus saprophyticus isolates. A total of 690 susceptibility determinations were performed with a categorical agreement with the standard method of 94.8%. Thirty-six errors (5.2%) were found. Of these, only 5 very major errors were detected, associated with trimethoprime/sulfamethoxazole susceptibility testing among Enterobacterales, glycopeptides, and HLAR among enterococci and cefoxitin susceptibility among staphylococci. The turn¬around time for AST directly from positive urine samples was between 3 and 5 hours versus 48 hours for the standard disk-diffusion method from isolated colonies. The rapidity of the HB&L AST method and its very good categorical correlation with the standard disk-diffusion method determine the potential of the system for wide application in routine laboratory practice.