Impact of Shipping Transit Time on Central Laboratory Processing of Total Colony Forming Units (CFU) and...

Central laboratory processing of anesthesia work area reservoir samples is used to improve infection control measures. Reservoir samples returning ≥ 100 colony forming units (CFU) and Staphylococcus aureus (S. aureus) detection are monitored to identify improvement targets. The impact of sample shipment time under ambient conditions on these meaningful outcomes has not been characterized. Such insight could help to further optimize feedback that has been proven to generate substantial reductions in surgical site infections. In this study, we aimed to assess the impact of ambient shipping conditions on patient intravenous stopcock sample CFU ≥ 100 and S. aureus detection because stopcock contamination is repeatedly associated with increased patient mortality.

We conducted a retrospective analysis involving seven geographically dispersed hospitals over a 4.2-year (October 1, 2018 to December 31, 2022) study period. We chose geographically dispersed sites considering variation in ambient shipping conditions and time. Stopcocks sampled at the end of surgery were shipped to a central laboratory, plated to sheep's blood agar, incubated for 24hr at 36°C, CFU/mL quantified, and distinct isolates assessed by colony morphology, Gram stain, simple rapid tests (e.g., coagulase, oxidase, lactose fermentation, catalase), and selective growth medium.

A total of 969 stopcock samples were analyzed. The percentage of stopcocks with CFU ≥ 100 was stable following sample collection from days 3 to 32 (odds ratio (OR) 1.0086/day, 95% confidence interval (CI) 0.9868-1.0309/day) and from sample kit preparation from days 3 to 143 (OR 1.0044/day, 95% CI 0.9991-1.0099/day). S. aureus detection decreased beyond 14 days from the period of collection during the surgical procedure (P = 0.0024; OR 0.83, 95% CI 0.21-0.71).

When utilizing a central laboratory for processing anesthesia workspace reservoir stopcock set samples, there is stability of ≥ 100 CFU for up to 32 days from collection and up to 143 days from kit preparation. S. aureus detection remains stable for up to 14 days. Therefore, when monitoring stopcock contamination to provide feedback, samples should be processed within 14 days from their collection. Anticipated shipment times should be considered by sample collection personnel to ensure optimal sample yield.