Modes of inhibition of foodborne non-Salmonella bacteria by selenite cystine selective broth.
Various cell densities of six common foodborne non-Salmonella bacteria were exposed to selenite cystine (SC) Salmonella selective medium. The insensitivity of Pseudomonas aeruginosa and Proteus vulgaris to SC was confirmed. Selenite cystine selective medium was effective against the sensitive bacteria up to certain cell densities, beyond which the bacteria survived. As judged from the minimum cell number required for survival in SC, Staphylococcus aureus was the most sensitive to SC, followed by Bacillus cereus, Escherichia coli and Citrobacter freundii. When sensitive bacteria were grown in SC, they enriched resistant variants which exhibited no or reduced sensitivity to SC. The change in density of sensitive cells after exposure to SC suggested that bacterial sensitivity to SC depended on the efficiency of killing and growth inhibition by SC as well as the fraction of resistant variants in the bacterial population. Since Salmonella samples generally contain unknown numbers and types of sensitive bacteria, it is difficult to predict the effectiveness of their selective inhibition by SC.
Chen
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Department of Biology, Carleton University, Ottawa, Ontario, Canada.
Fraser
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Yamazaki
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D000818:Animals; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development; D003470:Culture Media; D003553:Cystine / Q000494:pharmacology*; D005516:Food Microbiology; D012475:Salmonella / Q000302:isolation & purification*; D018038:Sodium Selenite / Q000494:pharmacology*
D003470:Culture Media; D003553:Cystine; D018038:Sodium Selenite