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 (2)

Bacteria Tryptic soy agar (TSA), casein soy peptone agar (CSPA) and nutrient agar (NA) are broad spectrum media for the collection and enumeration of bacteria. Special purpose media (i.e., selective media) are often used to select for specific microorganisms of interest. As with the media for fungi, chemicals may be added to the media which restrict growth of selected fungi and bacteria [DIFCO 1984].

(3)

Thermophilic Actinomycetes Thermophilic Actinomycetes is a special class of bacteria that has been associated with indoor environmental quality problems [Nevalainen 1989]. CSPA, TSA, and tryptone glucose yeast agar (also known as standard methods agar [SMA] and standard plate count agar [SPCA]) are broad spectrum media for the collection and enumeration of thermophilic Actinomycetes [DIFCO 1984; Amner et al. 1989; ACGIH 1989, Bacteria].

(4)

Additional Media Other media for the detection and enumeration of fungi and bacteria may be used. To discriminate for a general class of microorganisms by inhibiting or eliminating other microorganisms, a selective medium containing an antibiotic or other growthrestricting chemical may be used. To distinguish among species, a differential media may be used. Differential media contain indicators that permit the recognition of microorganisms with particular metabolic activities. Different incubation times or temperatures can also be used to get differential growth on the same medium. When a specific medium (i.e., selective or differential) is needed, the investigator(s) should refer to the most recent Manual of Clinical Microbiology published by the American Society for Microbiology, DIFCO Manual: Dehydrated Culture Media and Reagents for Microbiology published by DIFCO Laboratories, or the various catalogues published by the American Type Culture Collection (ATCC) [DIFCO 1984; Murray et al. 1995; Gherna et al. 1992; Jong and Edwards 1991].

e.

Blanks (1)

Laboratory Media Blanks Laboratory media blanks are unexposed, fresh media samples. These samples are generally not taken into the field. Before using any batch of media, incubate at least three culture plates under the same conditions as planned for the field samples, in order to check for sterility of the media. Approximately five media blanks should be included with each sample set. If the samples are to be analyzed by an outside

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NIOSH Manual of Analytical Methods