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Factors affecting microbiological colony count accuracy for bioaerosol sampling and analysis.

Authors
Chang-W; Grinshpun-SA; Willeke-K; Macher-JM; Donnelly-J; Clark-S; Juozaitis-A
Source
Am Ind Hyg Assoc J 1995 Oct; 56(10):979-986
NIOSHTIC No.
00238262
Abstract
The effects of bacterial spore surface density, nutrient concentration in culture medium, sample incubation time and ability of an observation system to identify overlapped colonies on colony masking were investigated using Bacillus-subtilis. A suspension of B-subtilis spores was aerosolized, and the aerosol was sampled using a slit to agar (STA) impactor. Colonies were counted after 12 and 36 hours of incubation. The results indicated that the degree of bacterial colony masking depended on colony density on a collection surface, on colony diameter, and on the ability of an observation system to distinguish overlapped colonies. Colony surface density depended directly on four factors, including bioaerosol concentration in the sampled air, sampler airflow rate, small collection time, and collection surface area. Colony surface density depended indirectly on nutrient concentration and incubation conditions. Colony diameter depended on nutrient concentration, incubation time and temperature, and colony surface density. Colony size was also a function of the specific organism studied and its growth rate and pattern. The occurrence of colony masking for STA impaction samplers, which results in an underestimation of actual colony count, increased with increasing colony surface density and diameter and with decreased ability to distinguish overlapped colonies. The authors offer a method to determine appropriate sample collection time to limit surface density of collected microorganisms and thereby reduce colony masking.
Keywords
NIOSH-Publication; NIOSH-Grant; Respirators; Bacteria; Sampling-methods; Microorganisms; Air-quality-control; Aerosol-sampling
Contact
Environmental Health University of Cincinnati 3223 Eden Avenue Cincinnati, OH 45267-0056
CODEN
AIHAAP
Publication Date
19951001
Document Type
Journal Article
Funding Amount
287049.00
Funding Type
Grant
Fiscal Year
1996
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-02948
Issue of Publication
10
ISSN
0002-8894
Priority Area
Respirator Research; Respirators
Source Name
American Industrial Hygiene Association Journal
State
OH
Performing Organization
University of Cincinnati, Cincinnati, Ohio
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