Comparative Evaluation of Inoculation of Urine Samples with the Copan WASP® and BD Kiestra™ InoqulA™ Instruments

This study evaluated quantitative results as well as the quality of the inoculation patterns on urine specimens produced by two automated instruments, the Copan WASP® and the BD InoqulA™. 526 urine samples submitted in 10 ml canisters containing boric acid were processed within 30 minutes on an InoqulA, plating 10 ul of specimen, and two WASP instruments, one plating 1 ul of specimen (WASP-1) and the second WASP 10 ul (WASP-10). All samples were incubated, analysed, and digitally imaged using the BD Kiestra™ Total Lab Automation system. Results were evaluated using a quantitative protocol as well as for presence or absence of ≥5 distinct colonies. Separate studies were conducted using QC organisms to determine the relative accuracy of WASP-1, WASP-10 and InoqulA compared to results obtained with a calibrated pipet. Results with QC organisms were calculated as ratios of the counts of the automated instruments divided by the counts for the calibrated pipet (golden standard). Ratios for the InoqulA were closest to 1,0 with the smallest standard deviations indicating that, compared to a calibrated pipet, the InoqulA results were more accurate than the WASP.. For clinical samples, the WASPs produced higher colony counts and more commensals than the InoqulA, with differences most notable for WASP-1. InoqulA was significantly better in dispersing organisms at counts ≥ 10(5) bacteria/ml of urine in comparison to WASP-1 and WASP-10 (p < 0.05). Our results suggest that InoqulA quantitative results are more accurate than WASP results and, moreover, the number of isolated colonies produced by the InoqulA was significantly greater than were produced by the WASP.