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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT OF DETECTION TECHNOLOGIES FOR TOXINS AND THEIR VALIDATION IN FOOD MATRICES Title: Phloxine B, aversatile bacterial stain

Author
item RASOOLY, REUVEN

Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 25, 2006
Publication Date: February 1, 2007
Citation: Rasooly, R. 2007. Phloxine B, aversatile bacterial stain. International Journal of Food Microbiology.157: 29-34.

Interpretive Summary: Gram staining is the first test performed for identification of bacteria. However in this staining some Gram-positive bacteria such as Bacillus strains appear incorrectly as Gram-negative. Many modifications of the Gram stain procedure have been developed to overcome these difficulties but the success of these modifications has been limited. We previously showed that Phloxine B; a color additive for foods, drugs, and cosmetics; has an immediate antimicrobial effect against Gram-positive bacteria but not Gram negative bacteria, when used at a concentration lower than that approved for human consumption by the FDA. Phloxine B can be used as an alternative to Gram staining, correctly identifying the bacteria that were misidentified by Gram staining. The data also show that this nontoxic staining is faster, cheaper and simpler than Gram. It is possible to differentiate among Gram- negative and Gram-positive bacteria by visual determination under normal room lighting, light microscopy, fluorescence microscopy and confocal microscopy.

Technical Abstract: We have previously shown that Phloxine B, a color additive for foods drugs, and cosmetics, has an immediate antimicrobial effect against Gram-positive bacteria, but not Gram-negative bacteria when used at a lower concentration than that approved for human consumption by the FDA. The data presented here suggest that Phloxine B has a potential use as a nontoxic, faster (< 2 min), inexpensive (350 tests for < 1 cent material) and simpler alternative use to Gram staining. Using Phloxine B staining it was possible to differentiate among Gram-negative and Gram-positive bacteria by visual determination under normal room lighting, light microscopy, fluorescence microscopy and confocal microscopy. This work demonstrated that Phloxine B can be used as a differential versatile bacterial stain and establishes a correlation between the staining properties of the dye and its bactericidal effect.

Last Modified: 7/28/2014
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