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Survival of Mycobacteria on N95 Personal Respirators

Published online by Cambridge University Press:  02 January 2015

Tiina A. Reponen ,
Zheng Wang ,
Klaus Willeke  and
Sergey A. Grinshpun
Tiina A. Reponen*
Affiliation:
Aerosol Research and Exposure Assessment Laboratory, Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio
Zheng Wang
Affiliation:
Aerosol Research and Exposure Assessment Laboratory, Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio
Klaus Willeke
Affiliation:
Aerosol Research and Exposure Assessment Laboratory, Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio
Sergey A. Grinshpun
Affiliation:
Aerosol Research and Exposure Assessment Laboratory, Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio
*
Aerosol Research and Exposure Assessment Laboratory, Department of Environmental Health, University of Cincinnati, PO Box 670056, Cincinnati, OH 45267-0056
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Abstract

Objectives:

The overall aim of this study was to investigate the survival and possible growth of Mycobacterium tuberculosis simulant bacteria on respirator filters.

Methods:

Mycobacterium smegmatis was used as a biochemical simulant for M tuberculosis. Bacterial survival was tested on National Institute for Occupational Safety and Health-certified N95 respirators from three manufacturers. The first experiments simulated one-time respirator use and subsequent storage for 1 to 9 days under ideal conditions for the growth of mycobacteria: 37°C and 85% relative humidity. The bacteria were loaded on the respirator filters under three different nutritional conditions: in the absence of nutrients; in the presence of human saliva (simulating conditions when the respirator is worn); and in the presence of nutrient broth (for ideal growth potential). The subsequent experiments simulated respirator wear for 2 hours under medium workload conditions at a breathing rate of 56 L/min.

Results:

It was found that M smegmatis did not grow on the tested respirators, even when the respirators were stored at temperature, humidity, and nutrition conditions most favorable for microbial growth. However, these bacteria could survive on respirators for up to 3 days during storage. The culturability of M smegmatis was not affected by airflow that simulated the breathing rate associated with medium work-load conditions for 2 hours.

Conclusions:

This study shows that M tuberculosis surrogate bacteria collected on a respirator are not able to grow and are able to survive only in ideal (ie, not clinically relevant) conditions. Based on these experiments, we conclude that M tuberculosis is unlikely ever to become an infectious problem in the air again, once it is removed by a respirator.

Type
Orginal Articles
Information
Infection Control & Hospital Epidemiology , Volume 20 , Issue 4 , April 1999 , pp. 237 - 241
Copyright
Copyright © The Society for Healthcare Epidemiology of America 1999

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