Tolerance of Staphylococcal Thermonuclease to Stress

Remarkable tolerance to prolonged heating, prolonged storage, and bacterial proliferation was exhibited by staphylococcal thermonuclease in foods and broth. A purified enzyme preparation added to Brain Heart Infusion broth was unaffected by the growth of five bacterial species. Minimal inactivation was effected by Bacillus subtilis. Optimal growth of Streptococcus faecalis var. liquifaciens caused extensive inactivation of thermonuclease. However, storage at room temperature or the addition of 5% NaCl caused only minimal inactivation.     

Dielectric breakdown measurements of human and bovine erythrocyte membranes using benzyl alcohol as a probe molecule

Dielectric breakdown of intact erythrocytes and subsequent haemolysis in the presence of increasing concentrations of benzyl alcohol were investigated by means of an electrolytical discharge chamber and a hydrodynamic focusing Coulter Counter.Low concentrations of the drug stabilized human and bovine erythrocytes against haemolysis induced by dielectric breakdown of the cell membrane in isotonic solutions, while high concentrations caused lysis similar to hypotonic and mechanical haemolysis. The stabilizing effect of the drug on electrically induced haemolysis depends on the pulse length of the applied electric field. The critical dielectric breakdown voltage of the membranes of intact cells decreases progressively with increasing benzyl alcohol concentrations, at which the membrane is also more stabilized against electrical and osmotic haemolysis. Occasionally, an increase in the dielectric breakdown voltage is observed at drug concentrations at which lysis occurs. A similar dependence of the breakdown voltage on drug concentration was found for human erythrocyte ghost cells prepared by dielectric breakdown.The results are consistent with the electromechanical model suggested for the dielectric breakdown mechanism and with the assumption of Metcalfe, using NMR and ESR techniques, that the fluidity of the membrane increases with increasing benzyl alcohol concentration.     

Temperate phages of Clostridium perfringens type C1.

Four phages isolated from carrier strains of Clostridium perfringens type C belong to two classes. The three phages of class I, c1, c3, and c4, and homoimmune and serologically closely related. The phage of class II, c5, is heteroimmune to the class I phages and not related to them serologically. Transduction experiments with several of the phages were negative. Mutants of the indicator strain with surface alterations occurred spontaneously in stock cultures. Electron micrographs show the phages of each class to be distinct yet similar, having polyhedral heads of about the same diameter 55 nm, and long, flexible tails without sheaths or collars. Phages c4 and c5 were characterized for their lysogenic properties. Phage c4 was inducible with mitomycin C. Both c4 and c5 were temperate viruses by the test of stability of their respective lysogens to phage-specific antisera.     

Destruction of Toxic Fungi with Low Concentrations of Methyl Bromide

Aspergillus parasiticus and Penicillium rubrum spores at the level of 10(4) to 10(5) / g were completely killed by prolonged exposure to 30 to 45 mg of methyl bromide per liter.     

Survey of Q-fever agglutinins in birds and small rodents in Northern California, 1975-76

Serum samples from 15 species of rodents and 33 species of birds were tested for agglutinins against Coxiella burnetii by the microagglutination test. Of 759 rodents tested, 21 (3%) were seropositive. Antibody positive rodents included muskrats, Ondatra zebethica, (11%), Rattus spp. (10%), Beechey ground squirrels, Otospermophilus beecheyi, (6%), wood rats, Neotoma fuscipes, (5%), and Peromyscus spp. (2%). Of 583 birds tested, 118 (20%) were seropositive. This included white crowned sparrows, Zonotrichia leucophrys, gold crowned sparrows, Z. atricapilla, and English sparrows, Passer domesticus, (68% in the composite); coots, Fulica americana, (29%); blackbirds, Euphagus cyanocephalus, (33%); crows, Corvus brachyrhyncos, (29%); robins, Turdus migratorius, (16%); pigeons, Columba fasciata, (10%); and mallard ducks, Anas platyrhynchos, (7%). There was a tendency for the seropositive animals to have been collected in the vicinity of endemically infected livestock.     

IL-12 breaks dinitrothiocyanobenzene (DNTB)-mediated tolerance and converts the tolerogen DNTB into an immunogen

Epicutaneous application of dinitrothiocyanobenzene (DNTB) induces tolerance against its related compound dinitrofluorobenzene (DNFB), because DNTB-pretreated mice cannot be sensitized against the potent hapten DNFB. This tolerance is hapten-specific and transferable. In this study, we demonstrate that IL-12 can break DNTB-mediated tolerance. Furthermore, naive mice treated with IL-12 before DNTB application responded to DNFB challenge with a pronounced ear swelling response without previous sensitization to DNFB, showing that IL-12 can convert the tolerogen DNTB into an immunogen. No differences in numbers or regulatory activity were observed between CD4+CD25+ regulatory T cells isolated from mice treated with DNFB, DNTB, or IL-12 followed by DNTB. However, the number of CD207+ Langerhans cells in regional lymph nodes of DNTB-treated mice was significantly lower than in animals treated with DNFB or IL-12 plus DNTB. Additionally, CD11c+ dendritic cells (DC) isolated from regional lymph nodes of DNTB-treated mice had a significantly lower ability to stimulate T cell proliferation and produced reduced amounts of inflammatory cytokines. Application of both DNFB and DNTB induced apoptotic cell death of DC in the epidermis and the regional lymph nodes. However, the number of apoptotic DC in regional lymph nodes was significantly higher in DNTB-treated animals compared with mice treated with DNFB or IL-12 plus DNTB. Therefore, we conclude that DNTB-mediated tolerance is secondary to inefficient Ag presentation as a result of apoptotic cell death of DC and that IL-12 converts the tolerogen DNTB into an immunogen by preventing DNTB-induced apoptosis of DC.     

Detection of Salmonella by a Single-Culture Technique

Dulcitol-selenite enrichment medium in a motility flask was used for the detection of Salmonella in food. A drop in pH of the dulcitol-selenite enrichment motility broth indicated the presence of Salmonella; this phenomenon was confirmed by fluorescent-antibody staining. A complete correlation was found between fluorescent-antibody staining and recovery on Brilliant Green agar. Testing of 332 samples of 8 different kinds of foods and feeds indicated no significant difference in sensitivity between the new technique and a conventional Salmonella detection technique. The new technique permitted detection of even small numbers of Salmonella in 1 to 2 days.     

Evaluation of the Minitek system for characterization of Bacillus species

Minitek (BBL Microbiology Systems, Cockeysville, Md.) substrate disks were evaluated as alternatives to conventional tests for the characterization of Bacillus species. Results were compared for 10 reference isolates and 87 isolates from food sources. The overall agreement of results between the Minitek and conventional tests was 92% for reference strains and 86% for food isolates.