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PubMed1963

ANTIMICROBIAL ACTION OF NITROGEN-CONTAINING STEROIDS.

Smith, Rodney F. (University of Maryland, Baltimore), Donald E. Shay, and Norman J. Doorenbos. Antimicrobial action of nitrogen-containing steroids. J. Bacteriol. 85:1295-1299. 1963.-A new group of 16 synthetic nitrogen-containing steroids have been tested against a variety of microorganisms for antimicrobial properties. The gradient plate screening method, serial dilution, and dry weight techniques were used in the studies. The organisms tested consisted of 14 gram-negative bacteria, 10 gram-positive bacteria, 2 actinomycetes, 7 yeasts, and 8 molds. Inhibitory properties were found to be specific and potent in four compounds, with inhibitory concentrations as low as 0.37 mug/ml. Three of the active steroids are 4-aza cholestanes and one is a 4-nor-3,5-secocholestane amide. Sensitivity to the compounds was greatest in the gram-positive bacteria, followed by the yeasts and molds. The gram-negative bacteria were not inhibited. All 16 steroids interfered to some extent with pigmentation in Serratia marcescens but not with pigment production in Pseudomonas aeruginosa. In a few instances, some of the molds were stimulated by the steroids at a concentration of 250 mug/ml.

Actinomycetales↗
PubMed1996

Analysis of Lactobacillus phages and bacteriocins in American dairy products and characterization of a phage isolated from yogurt.

Yogurt and acidophilus milk that contain Lactobacillus acidophilus could promote human health because L. acidophilus can inhibit enteric and food-borne microbial pathogens. To evaluate the stability of diary L. acidophilus cultures, we studied whether some diary lactobacilli could be inhibited by phages or bacteriocins released by other dairy lactobacilli. From 20 yogurts and two acidophilus milks purchased at local food markets, 38 Lactobacillus strains were isolated. Eight Lactobacillus type strains were used as controls. With mitomycin induction and agar spot assay, phages and bacteriocins were isolated from these strains and their activities were analyzed. Lactobacillus strains from 11 yogurts released phages, while the strains from most of the remaining products released bacteriocins. One phage, designated phi y8, was characterized. It was spontaneously released from its host strain L. acidophilus Y8, at a rate of about 10(4)/ml. This phage lysed nine other dairy Lactobacillus strains tested. It had a burst size of 100, an elongated prolate head of 39 by 130 nm, a long, flexible but noncontractile tail of 300 nm, and a 54.3-kb linear double-stranded DNA. DNA fingerprinting analysis indicated that L. acidophilus phages of nine yogurts in this study belonged to the same type as phi y8. Although they may be sensitive to bacteriocins, all lysogens resisted further phage attacks, whereas most nonlysogens were sensitive to both phages and bacteriocins. Therefore, Lacotbacillus cultures of some American yogurts and acidophilus milks may be unstable or unsafe because they can either be inhibited by phages or bacteriocins or release them to inhibit lactobacilli or other diary products.

Animals↗
PubMedDate not supplied

[Use of molecular methods in food microbiology with the example of probiotic use of lactobacilli].

The aim of molecular methods in food microbiology is the identification or strain specific differentiation of microorganisms. Identification methods include besides taxonomic purposes also the detection of virulence genes or resistance markers. Strain specific differentiation is used for epidemiological investigations or the quality control of technologically used bacteria. Probiotic strains of the Lactobacillus acidophilus-group were investigated with different molecular methods: for identification proteinfingerprinting and RAPD-PCR (Random Amplified Polymorphic DNA-PCR) were applied, for strain specific differentiation pulsed field gel electrophoresis (PFGE) and again RAPD-PCR were used. The molecular methods applied should be chosen depending on the objective (identification, differentiation) and with respect to the organism to be tested. In case of probiotic lactic acid bacteria like the L. acidophilus-group proteinfingerprinting has proved to be successful for identification and with some limitation also RAPD-PCR. For differentiation PFGE is suitable as well as RAPD-PCR. Those methods differ substantially in their work load and in personal requirements, and show different power of discrimination and reproducibility within and between laboratories. This should be considered while choosing the appropriate method.

DNA, Bacterial↗