Direct microscopic examination detects sample contamination in clinical bacteriology
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Peer-reviewed literature indicates that microscopic examination, such as staining and visual checks of media, is utilized to assess and detect bacterial contamination in samples.
AbstractNamed after Hans Christian Gram who developed the method in 1884, the Gram stain allows one to distinguish between Gram‐positive and Gram‐negative bacteria on the basis of differential staining with a crystal violet‐iodine complex and a safranin counterstain. The cell walls of Gram‐positive organisms retain this complex after treatment with alcohol and appear purple, whereas gram‐negative organisms decolorize following such treatment and appear pink. The method described here is useful for assessing bacterial contamination of tissue culture samples or for examining the Gram stain status and morphological features of bacteria isolated from mixed or isolated bacterial cultures.
Procedures involving lipid media for detection of bacterial contamination in breweries.
The liquid equivalent of universal beer agar, designated universal beer liquid medium, and its beer-free equivalent, universal liquid medium (UL), were equally effective in demonstrating bacterial contamination in 120 of 200 samples from different stages of commercial brewing process. Growth of the contaminants after 3 days was consistently more luxuriant in the UL medium. A yeast-water substrate medium failed to reveal many contaminants detected with UL in 392 samples from three breweries and revealed only a few not detected with UL. The use of UL and a lactose-peptone medium, with microscope examination of the media for bacterial growth, permitted detection of 93% of the known contaminants compared to 87%, detected with UL alone; this combination or universal beer liquid medium plus lactose-peptone medium can therefore be recommended for the detection of bacterial contaminants in brewery samples. Bacterial contamination of pitching yeasts appeared to be a particular problem in the breweries investigated.
Published in Applied and environmental microbiology (1977)
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