Growth and toxin production by Clostridium botulinum in moldy tomato juice.

Tomato juice inoculated with Cladosporium sp. or Penicillium sp. developed pH gradients with the upper portions near the mold mats having pH values near neutrality and the lower portions remaining more acid. Clostridium botulinum spores in these moldy tomato juices germinated, grew out, and produced toxin.

Microfermentation series for identification of single colonies of Enterobacteriaceae.

Microfermentation tests for members of the family Enterobacteriaceae were devised by using agar solutions in disposable, multi-welled, plastic trays. The tests could be made directly from isolated colonies picked from agar plates and represented a considerable saving in time, labor, and materials over the conventional methods. Tests were formulated for determining carbohydrate fermentations, citrate utilization, motility, amino acid decarboxylation, and production of H(2)S, indole, urease, and acetyl-methyl-carbinol.

Efficiency of Salmonella isolation from meat-and-bone meal of one 300-g sample versus ten 30-g samples.

Twenty-five meat-and-bone meal samples were analyzed for salmonellae, comparing a single 300-g to ten 30-g samples. Seventeen were positive using the larger sample; eighteen were positive with the smaller. The 300-g sample showed a significantly higher (P < 0.01) percentage of confirmed salmonellae at 2 days of incubation than at 1 day. The ten 30-g samples did not show changes at 2 days. At 2 days, the 30-g samples showed significantly fewer confirmed salmonellae than the 300-g sample; however, there was no difference at 1 day. Of 1,417 presumptive colonies picked, 1,215 (85.7%) were lysine decarboxylase-positive and 1,152 (81.3%) were agglutinated by one of the somatic antisera. There were no significant differences in diversity or total numbers of different somatic groups between the large and small samples.

Effect of type of enrichment and duration of incubation on salmonella recovery from meat-and-bone meal.

Twenty-five meat-and-bone meal samples were enriched with either selenite-cystine or tetrathionate and incubated for 1 and 2 days. Seven were previously found to be positive; of the other 18, 16 were positive for salmonella. The number of somatic serogroups per sample ranged from 1 to 11 with a mean of 3.8. Significantly more (P < 0.01) group C(1) salmonellae were isolated using tetrathionate than selenite, whereas significantly more of groups G, 35, and Difco poly-valent D were isolated from selenite than tetrathionate. Seventy-six percent of the presumptive colonies from Brilliant Green agar showed a positive lysine decarboxylase reaction, and there were no differences between media or times of incubation. Ninety-four per cent of the lysine decarboxylase-positive cultures showed a positive somatic antiserum response; again there were no differences between times or enrichments although there were significantly more total positive serogroups at 2 days than at 1 day from tetrathionate but not from selenite. There were indications that certain serogroups preferred either one or the other enrichment. There were no differences in total positive samples with the two enrichments although neither alone was sufficient to identify all positives. Several lactose-positive salmonellae were recovered.