Performance of Copan WASP for Routine Urine Microbiology

Abstract

This study compared a manual workup of urine clinical samples with fully automated WASPLab processing. As a first step, two different inocula (1 and 10 μl) and different streaking patterns were compared using WASP and InoqulA BT instrumentation. Significantly more single colonies were produced with the10-μl inoculum than with the 1-μl inoculum, and automated streaking yielded significantly more single colonies than manual streaking on whole plates (P < 0.001). In a second step, 379 clinical urine samples were evaluated using WASP and the manual workup. Average numbers of detected morphologies, recovered species, and CFUs per milliliter of all 379 urine samples showed excellent agreement between WASPLab and the manual workup. The percentage of urine samples clinically categorized as positive or negative did not differ between the automated and manual workflow, but within the positive samples, automated processing by WASPLab resulted in the detection of more potential pathogens. In summary, the present study demonstrates that (i) the streaking pattern, i.e., primarily the number of zigzags/length of streaking lines, is critical for optimizing the number of single colonies yielded from primary cultures of urine samples; (ii) automated streaking by the WASP instrument is superior to manual streaking regarding the number of single colonies yielded (for 32.2% of the samples); and (iii) automated streaking leads to higher numbers of detected morphologies (for 47.5% of the samples), species (for 17.4% of the samples), and pathogens (for 3.4% of the samples). The results of this study point to an improved quality of microbiological analyses and laboratory reports when using automated sample processing by WASP and WASPLab.

FIG 1

Study design and evaluation steps.(A) Part 1: evaluation of the optimal inoculation volume and streaking pattern. (B) Part 2: head-to-head comparison.

FIG 2

Streaking pattern details and resulting numbers of single-colony counts. (A) One manual (routine) and three automated quantitative streaking patterns, with varied numbers of zigzag (zz) lines shown in brackets: WASP single streak type 2 (SST2), WASP single streak type 6 (SST6), and InoqulA. Comparison of single colonies obtained by manual and automated streaking. One and 10 μl E. coli (B) and enterococci (C) bacterial suspensions were used with CFUs ranging from 10⁴ to 10⁶. The mean values of 30 clinical strains per species are shown with standard deviations.

FIG 3

Cumulated numbers of single colonies recovered from mixed cultures containing variable CFU counts of E. coli (10⁴ to 10⁶/ml as indicated) plus fixed CFU counts of 10⁶/ml of both enterococci and coagulase-negative staphylococci. Mean values of 10 mixed cultures prepared with individual clinical strains are shown with standard deviations.

FIG 4

Correlation of morphologies (A), recovered species (B), and CFUs (C) resulting from the head-to-head comparison of 121 and 379 clinical samples, respectively. Data indicate a shift to higher numbers for all three parameters for automated versus manual inoculation.