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Aerosol and Airborne Transmission of Listeria Monocytogenes: A Potential Source of Cross Contamination

Investigators
Dickson, James
Institutions
Iowa State University
Start date
2006
End date
2009
Objective
The methods for recovering airborne and aerosolized Listeria monocytogenes will be will be optimized. Both recovery media and sample collection devices will be compared to determine the optimum combination of media and collection devices to recover the maximum number of Listeria. The effects of bacteria stress will be evaluated on the survival of airborne and aerosolized Listeria monocytogenes. Bacterial stressors will include but not be limited to nutrient deprivation, acid and alkaline adaptation and osmotic stress. The effects of environmental stress will be evaluated on the survival of airborne and aerosolized Listeria monocytogenes. Environmental stressors will include to temperature and relative humidity. A surrogate microorganism will be dispersed in a contained environment. The dispersion of the microorganism will be determined both temporally and spatially. Temporal and spatial models will be constructed from the data obtained from a variety of environmental conditions.
More information
NON-TECHNICAL SUMMARY: It is widely assumed that Listeria monocytogenes can be transmitted to processed foods by means or airborne or aerosol transmission. "Airborne" bacteria may best be defined as bacteria which are attached to dust particles, while "aerosolized" bacteria may be defined as bacteria which are suspended in liquid, which then become airborne by physical actions which develop droplets. However, there is very little scientific data to support this assumption, or to provide the food industry with reliable information to help control airborne or aerosol transmission. This project will determine the optimum methods of recovery of airborne Listeria monocytogenes, and determine the effects of stress on the survival of airborne bacteria.

APPROACH: We propose to conduct a systematic study of the aerosol and airborne characteristics of Listeria monocytogenes under laboratory conditions. These studies will evaluate recovery methods as well as the effects of pre-existing environmental stress on the survival of the bacteria. Using this data, we will develop both temporal and spatial models of both airborne and aerosol dispersal of Listeria monocytogenes in a laboratory environment. We will also release Listeria innocua in a biologically secure food processing environment, and develop temporal and spatial models for the airborne and aerosol dispersal of this organism. To enable the research team and others to intuitively understand and query the research results, the models will be visualized in a virtual research environment ("virtual reality"). While visualization of the data and environment is one part of creating this research environment, a more critical aspect of a virtual research environment is the coupling of all of the models (temporal and spatial), data, and other information available together.

PROGRESS: 2007/08 TO 2008/08
OUTPUTS: It is widely assumed that Listeria monocytogenes can be transmitted to processed foods by means or airborne or aerosol transmission. "Airborne" bacteria may best be defined as bacteria which are attached to dust particles, while "aerosolized" bacteria may be defined as bacteria which are suspended in liquid, which then become airborne by physical actions which develop droplets. However, there is very little scientific data to support this assumption, or to provide the food industry with reliable information to help control airborne or aerosol transmission. There are two available research studies specifically relating to aerosolized L. monocytogenes, and none, other than anecdotal reports, relating to airborne L. monocytogenes. Given the limited scientific data, and that the methodology to recover airborne or aerosolized L. monocytogenes may not be as well developed, it is impossible to assess the true risk of cross contamination of this organism in foods, particularly ready to eat foods. In addition, the limited data available has been conducted (by necessity) in laboratory hoods or other containment vessels. There are no data within the public domain on the potential dispersion of Listeria spp. in a food processing environment. While it is generally acknowledged that Listeria spp. is an "environmental" contaminant, our knowledge of the interaction of this bacterium in the air environment within a food processing establishment is quite limited. The first objective of this project was to evaluate recovery methods and determine the optimum conditions for the recovery of airborne and aerosolized Listeria. We have almost completed this objective, although the research has been delayed by repeated difficulties with the aerosol chamber.

IMPACT: 2007/08 TO 2008/08
One of the difficulties with the evaluation of airborne microorganisms is the relative inefficiency of the recovery methods. Recovery methodology is perhaps the single most important requirement in further studies. We believe that the results of the research with recovery methods will be significant in future studies with airborne Listeria.

PROGRESS: 2006/08/15 TO 2007/08/14
Preliminary experiments have begun to develop protocols for the aerosolization and recovery of Listeria monocytogenes. Significant progress progress has been made on Objectives 1 and 2, determining optimal recovery methods for aerosolized and airborne Listeria monocytogenes and developing temporal models for the dispersion of L. monocytogenes in a laboratory environment. A preliminary temporal model is expected within the next 6 months.

IMPACT: 2006/08/15 TO 2007/08/14
It is widely assumed that Listeria monocytogenes can be transmitted to processed foods by airborne transmission. However, there is little scientific data to support this assumption, or to provide the food industry with reliable information to help control airborne or aerosol transmission. Given the limited scientific data, and that the methodology to recover airborne or aerosolized L. monocytogenes may not be as well developed, it is impossible to assess the true risk of cross contamination of this organism in foods, particularly ready-to-eat foods. The data generated in this study will allow food processors and regulatory agencies to better assess the potential airborne transmission of Listeria monocytogenes. Specifically, the spatial and temporal models developed as part of this research will allow the food industry to model and predict airborne transmission within their processing facilities, and to identify areas which may be critical in controlling this transmission. The methodology developed in this research will further the research in aerobiology, and will also assist the food industry and regulatory agencies in monitoring air quality in food processing establishments.

Funding Source
Nat'l. Inst. of Food and Agriculture
Project source
View this project
Project number
IOW05096
Accession number
207482
Categories
Listeria
Prevention and Control