Background: Automated plating instruments are available to reduce labor associated with specimen inoculation and improve the quality of plating. The two most common instruments on the market are the WASP (Copan Diagnostics) and Kiestra InoqulA (Becton Dickinson). The impact of inoculum size differences (1 µL WASP, 10 µL for Kiestra) was studied on the time necessary for reading cultures.
Methods: 50 specimens submitted for routine culture were inoculated by WASP onto a Blood-Agar/MacConkey (BAP/MAC) bi-plate using a dual 1µL loop with streaking pattern WASP1, and on BAP and MAC whole plates using a 1µL loop with streaking pattern WASP2. They were also plated using the InoqulA onto BAP and MAC whole plates using 10 µL with streaking pattern KI1. All plates were incubated in the WASPLab™ (CO2) incubator for 18 hours. Technologists were presented with images for WASP1, WASP2 and KI1 (total of 150 images for each). The examination time of each set of plates was recorded and averaged between three technologists.
Results: Average technologist read times for each inoculated set of plates was 17.47 minutes (WASP1), 19.04 minutes (WASP2), and 28.78 minutes (KI1). When compared to the KI1 set, the WASP1 set was read 11.31 minutes faster and the WASP2 set 9.74 minutes faster. Given an average technologist wage of $58.59/hr within the Sutter Health System (SHS) the potential labor cost savings is approximately $22.09/100 urine cultures for WASP1 and $19.02/100 urine cultures for WASP2, compared to KI1.
Conclusions: Technologists within SHS analyzed plates processed on WASP faster than those processed on InoqulA. We believe the improvement in reading times for plates inoculated with the WASP is reflective of better isolation of colonies along with easier calculation of colony counts due to the 1µl volume used for plating. SHS processes 700 urines/day and using either the WASP1 or WASP2 streaking patterns was shown to provide an approximate labor savings (excluding benefits) of $56,439.95/year and $48,596.10/year, respectively, compared to KI1.