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Survival and growth of bacteria on respirator filters.

Wang Z; Reponen T; Willeke K; Grinshpun S
American Industrial Hygiene Conference and Exposition, May 9-15, 1998, Atlanta, Georgia. Fairfax, VA: American Industrial Hygiene Association, 1998 May; :62
All nine types of respirators certified under the 1995 National Institute for Occupational Safety and Health regulations for respirators can be used by health care workers for the prevention of Mycobactmum tubercuiosis (MTB) transmission. The N95 half-mask particulate respirator is the most frequently used for this purpose. Questions have been raised regarding the possibility of MTB growth on respirators due to handling, storage, and reuse. This study was conducted to determine whether MTB may grow, and how long it may survive on a respirator filter. Bacillus subtilis (BS), Pseudomonas fluorescens (PF) and M smegmatrs (MS) were selected as MTB simulant bacteria. Bactena were aerosolized with a Collison nebulizer from three different suspensions: deionized water, human saliva, nutrient broth (tryptic soy broth for BS and PF, Middlebrook 7x10 for MS). Deionized. water represented loading with bacteria only human saliva represented loading during respirator wear, and nutrient broth represented the extreme situation with optimal nutrients. A preconditioned 37-mm filter was cut from a N95 respirator and was challenged 10 minutes with the aerosolized bacteria and nutrients in an aerosol exposure chamber. The airflow rate through the filter was 5 L/min during the loading cyde. This corresponds to a breathing rate of 85 L/min under heavy work load. Loaded. filters were incubated at 85% relative humidity. The incubation temperature was 37lC for BS and MS and 281C for PF. Analyses were conducted after 0, 1,3, 6, 9, and 13 days of incubation. Betore studying the survival, several elution methods were evaluated: vortexing. Ultrasonicing, and mechanical shaking after submerging the exposed filter in a buffer solution. The total bactera were counted with a hemocytometer while the viable count was analyzed. by cultivating diluted bacterial suspensions on agar. The data indicate that vortexing is the best elution method, with the highest totaland ciulturable bacteria_ It was, therefore, used in this study. None of these three test bacteria were able to grow on the N95 respirator material. However, BS could survive on filters Over 13 days while MS survived for 1-3 days depending on the nutriytional conditions. This indicates that used. Respirators may be a potentialMTB transmission source if improperly stored and reused.
Respirators; Health-care; Health-care-personnel; Workers; Face-masks; Face-shields; Particulates; Personal-protection; Personal-protective-equipment; Respiratory-equipment; Respiratory-protection; Respiratory-protective-equipment; Bacteria; Humans; Men; Women
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American Industrial Hygiene Conference and Exposition, May 9-15, 1998, Atlanta, Georgia
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University of Cincinnati, Cincinnati, Ohio
Page last reviewed: May 11, 2023
Content source: National Institute for Occupational Safety and Health Education and Information Division