A Study of the Effectiveness of the Containment Level-4 (CL-4) Chemical Shower in Decontaminating Dover Positive-Pressure Suits

Abstract

Objectives: The decontamination or physical removal of contaminants from personal protective equipment upon exit from high containment laboratories is crucial to maintain containment and safety of laboratory workers. The current methodology for exiting from high-containment level 4 (CL-4) laboratory calls for laboratory personnel to decontaminate their worn positive pressure suits via “mechanical washing” during a 5-minute chemical/water rinse cycle. This study was carried out to evaluate the effectiveness of the current shower methodology and to test the efficacy of the physical removal of any contaminants from the positive pressure suits following the application of water alone and of a milder detergent. Method: Brushed stainless steel test carriers were inoculated with Vesicular Stomatitis Virus (VSV), a surrogate for filoviruses, and a soil load based on mucin, tryptone, and bovine serum albumen (BSA) to mimic serum. The virus mixture was then dried and secured with magnets onto a pre-washed Dover positive pressure suit. The suit was subjected to varying shower cycles, and once complete, carriers were removed and further analyzed. Any remaining virus was quantified using a TCID50 assay on Vero E6 cells showing cytopathic effects after 3–5 days. Three positive control carriers with dried inoculum were left untreated by the shower cycle, and negative control carriers (no inoculum) were also included on the suit during shower testing and analyzed alongside the test carriers. Results: No residual virus was detected using the TCID50 method following the normal shower cycle (2-minute chemical wash and 3-minute water rinse). Shower cycles consisting of 5 minutes of water-only rinses were equally as effective in removing virus from the suit. Cycles consisting of only a 1-minute water rinse showed a 5.5 log decrease from an average initial 6 log viral concentration. Varying time points between 1 and 5 minutes were evaluated during the normal shower cycle as well as varying concentrations of chemical disinfectant. Conclusion: The current chemical shower protocol is effective in removing all virus from the Dover positive pressure suits worn in high-containment laboratories. However, data show that reducing the need for a high-level decontamination chemical and using any surfactant carries the same effectiveness as the current protocol used, which would serve as a more cost-effective and eco-friendly alternative to the currently implemented shower protocol.