Hydrogen Peroxide Vapor Decontamination of a New Protective Environment: a Banana Peel Issue

Background: Allogeneic bone marrow transplant (BMT) recipients are at risk for invasive fungal disease.  In the 1980’s, laminar air flow units (LAF) were placed in our BMT unit to prevent aspergillosis.  Protective environments (PE) for BMT patients were installed in our newly constructed cancer tower with HEPA filtration of air at the unit’s entrance and at the point of entry into BMT PE.  As part of a quality check, Infection Control personnel carried out air sampling to compare air filtration in the new PE with the older LAF PE.  All rooms except two were comparable; these two rooms yielded 20-fold more fungal isolates than all other areas (0-1fungal colonies vs. 20-26 fungal colonies).  Thus, an investigation was initiated by the Infection Control and Facilities Departments.

Objective: to identify and eliminate the source of the fungal contamination and restore safe PEs for BMT patients.

Methods: Air was sampled with a SAS-Super Microbial Air Sampler (according to ISO standards 14698-1); 500 cubic meter volumes of air were sampled in 5-minute intervals directly onto Sabouraud’s agar and cultured using standard methods.  Inspection of all filters and room closures was performed by Infection Control and Facilities personnel.  The PE ceiling tiles were removed to evaluate the space above. 

Results: Room inspections did not reveal an obvious source of fungi.  However, when the sealed ceiling tiles were removed, investigators found a banana peel with fungal growth above the ceiling in one room and a hole in the wall above the ceiling tiles, which enabled communication between the rooms.  Hydrogen Peroxide Vapor (HPV) room decontamination by a contracted service was carried out in both rooms and the ceiling space using a standard decontamination protocol.  The efficacy of the HPV process was validated using Tyvek^® pouched 6-log Geobacillus stearothermophilus (spore) biological indicators in both rooms and ceiling spaces; all subsequent tests were negative.  Tiles were replaced and clipped down to PE standards.  Post HPV air sampling was negative for fungal growth.  Contractors had failed to meet the standards which prohibited eating in the PE rooms during construction. Further investigation of the new BMT units revealed empty soda cans and food wrappers above the ceilings.  Consequently, all tiles were removed and replaced by contractor.  No other contamination sources were identified.

Conclusions: Failure to comply with construction standards can occur, notwithstanding a signed contract, and can lead to PE contamination.  Thus, more stringent monitoring of construction activities is indicated and evaluation of new PEs should be considered during the post-construction phase.  Fruit left in a PE after HEPA filters can lead to environmental contamination and invasive fungal disease if undetected. HPV technology is a safe and effective way to decontaminate PEs, eliminate fungal contamination, and institute a quick return to service.