P1-18 Comparison of a Reference Method of Bioaerosol Sampling to a Newly Developed Compressed Air Microbial Testing Unit (CAMTU)

Monday, July 23, 2012
Exhibit Hall (Rhode Island Convention Center)
Youngsu Lee, University of Massachusetts, Amherst, MA
Paul Rebe, Parker Hannifin Corp, Haverhill, MA
Allan Fish, Parker Hannifin Corporation, Haverhill, MA
Lynne McLandsborough, University of Massachusetts-Amherst, Amherst, MA
Introduction: Compressed air is used in a variety of processes in the food industry. Currently, food manufacturers should validate the safety of all ingredients or processes for regulatory compliance, but unfortunately, there is currently no standard method to evaluate the microbial content of compressed air.

Purpose: The objective was to compare the newly developed Compressed Air Microbial Testing Unit (CAMTU) to a reference Andersen single stage viable particle sizing sampler for recovery of aerosolized Micrococcus luteus in compressed air.   

Methods: Micrococcus luteus ATCC 4698 was used in this study.  A biological aerosol was generated using a high pressure nebulizer with 310 kPa air pressure. The biological aerosol within the compressed air was decompressed in a sampling box containing two Andersen single stage viable particle sizing samplers which collected airborne bacteria at a flow rate of 28.3 l/min onto trypticase soy agar (TSA). To test the CAMTU system, compressed air was directly sampled at a flow rate of 46 l/min onto TSA.

Results: Various volumes of air (15, 30, 60 or 121 l) were collected using the Andersen impactor and the compressed air was found to be contaminated at the level of 0.2-0.4 CFU/l. Similar volumes were collected directly into the CAMTU units and aerosolized bacteria were recovered in the range 0.5 -2.5 CFU/l. Low numbers bacteria isolated with both air sampling methods, indicating a large reduction (7-8 log) due to nebulization stress. Despite the low levels in the aerosol, the results show that the CAMTU devise was able to isolate similar cell numbers to the Andersen impactor without a decompression chamber.

Significance:  The CAMTU device has been shown to have similar bacterial recovery to the Andersen impactor method.  The CAMTU device is a portable, fast testing method for direct sampling compressed air in the food processing environment.