Viability of Salmonella in bone meal.

The ability of Salmonella to survive varying concentrations of sodium metabisulphite incorporated into bone meal (rendered animal by-product) was investigated. No viable Salmonella was detected after 4 days of exposure of the micro-organisms to 5,000 ppm of sodium metabisulphite. The minimum killing concentration of metabisulphite was also established at 4,000 ppm. However, the killing effect of the metabisulphite was moisture-dependent, being most potent at a moisture level of 8 to 12%.

Effect of disulphite on protein and pyridine-2,6-dicarboxylic acid synthesis in sporulating cells of bacterial species.

The effect of disulphite on protein and pyridine-2,6-dicarboxylic acid (dipicolinic acid, DPA) synthesis was investigated in sporulating cells of Bacillus subtilis E52 and B. cereus W18. Progressive reductions were evident in the protein and DPA concentrations for both sporulating cells with increasing concentrations (100 to 600 micrograms ml-1) of disulphite. A significant (P less than 0.05) reduction in protein synthesis by disulphite was exhibited, culminating in a decrease in protein synthesis ranging from 50% to 1.4%, and 50% to 2.5%, in B. subtilis E52 and B. cereus W18, respectively. The same disulphite concentrations caused a significant (P less than 0.05) decrease in DPA synthesis ranging from 75% to 12.5% and 70% to 5%, for B. subtilis E52 and B. cereus W18, respectively. DPA synthesis was completely prevented at 500 and 600 micrograms ml-1 for B. subtilis E52 and B. cereus W18, respectively. A plausible mechanism for the inhibitory action of disulphite on sporulating cells of the bacteria is proposed.

Effect of metabisulphite on sporulation and alkaline phosphatase in Bacillus subtilis and Bacillus cereus.

The effect of metabisulphite on spore formation and alkaline phosphatase activity/production in Bacillus subtilis and Bacillus cereus was investigated both in liquid and semi-solid substrates. While supplementary nutrient broth (SNB) and sporulation medium (SM) were used as the liquid growth media, two brands of powdered milk were used as the food (semi-solid) substrates. Under both aerobic and anaerobic conditions, B. subtilis was more resistant to metabisulphite than B. cereus while the level of enzyme production and spores formed were generally higher under aerobic than anaerobic conditions. The metabisulphite concentrations required to inhibit spore production as well as alkaline phosphatase synthesis/activity were found to be relatively low and well within safety levels for human consumption. It is concluded that metabisulphite is an effective anti-sporulation agent and a recommendation for its general use in semi-solid and liquid foods is proposed.

Sporulation of bacterial species in the presence of metabisulphite.

The effect of metabisulphite on the sporulating ability of Bacillus subtilis E52 and B. cereus W18 was studied. Whereas metabisulphite concentrations of 500 and 600 micrograms ml-1 prevented sporulation of B. subtilis and B. cereus, respectively, lower concentrations caused reductions in their percentage sporulations. Glucose dehydrogenase (GDH) and alkaline phosphatase (ALP) activities of both sporulating bacteria were not detected at the stated metabisulphite concentrations. A relationship between the percentage sporulation of the bacteria and the activity of the enzymes in the presence of metabisulphite was exhibited. ALP activity may serve as an index of the effectiveness of the antisporulating activity of metabisulphite. Both enzymes are likely to be among the few targets for the antisporulating activity of metabisulphite.

The choice of adjuvants in Mycoplasma vaccines.

The use of adjuvants in vaccine production is an important aspect of potent vaccines. This investigation was concerned with finding the most efficient adjuvants for use in Mycoplasma vaccines produced in Nigeria. Four different vaccines were produced from the Gladysdale strain of Mycoplasma mycoides subspecies mycoides. They differed depending on the type of adjuvants used. Each vaccine was used to vaccinate eight cattle using a dose of 1 ml. Two other groups of eight cattle were used as controls. One of the two groups received 1 ml dose of inactivated Gladysdale vaccine without adjuvant while the second group received 1 ml dose of saline. The number of cattle that had the peak complement fixing (CF) antibody titres of 1/80 in each group of cattle was four for vaccine containing aluminium hydroxide gel, eight for vaccine containing liquid paraffin, one for vaccine containing sodium alginate and one for vaccine without adjuvant. Seven cattle from the group vaccinated with vaccine containing Freund's incomplete adjuvant had peak CF antibody titres of 1/80 or higher. The two groups vaccinated with vaccine containing liquid paraffin and Freund's incomplete adjuvant survived challenge at 6 months post vaccination. Freund's incomplete adjuvant and liquid paraffin containing 10% Arlacel A are the most efficient adjuvants.

Aflatoxin distribution in edible oil-extracting plants and in poultry feedmills.

The occurrence and distribution of aflatoxins B1, B2, G1 and G2 in the raw materials and products of three plants for extracting edible oils and in two poultry feedmills in which by-products of the oil extraction were used for feed formulation were investigated. While levels of aflatoxins were high in the products and by-products from the three extraction plants, the levels in the poultry feeds produced in the feedmills were found to be relatively low. The latter finding may reflect the proportion of pellets included in the feedstock formulation, while the climatic differences in the areas in which the extraction plants were situated were a possible factor in the differing levels of aflatoxin found in the samples from the three extraction plants.

Aflatoxin distribution and total microbial counts in an edible oil extracting plant. I. Preliminary observations.

Groundnut (peanut) kernels, groundnut and cotton-seed pellets and groundnut and cotton-seed oils (crude and refined) were screened for aflatoxins. The groundnut kernels and groundnut and cotton-seed pellets were additionally examined for total microbial counts as well as for certain types of micro-organism. All samples contained aflatoxins (B1, B2, G1 and G2) while a quantitative estimation of aflatoxin B1 revealed that all samples contained this aflatoxin in varying amounts. The study identified in substantial numbers several types of micro-organisms that have been associated with industrial and health hazards.

The chemical stability of metabisulphite in bone meal and gelatin.

The chemical stability of metabisulphite, an anti-microbial preservative, was investigated in rehydrated bone meal and in gelatin. Metabisulphite-treated bone meal rehydrated to a total moisture level of 10%, and metabisulphite-treated gelatin was sampled over 4 weeks to determine the levels of residual metabisulphite, as measured by the available sulphur dioxide. Results revealed that the levels of metabisulphite in the bone meal declined quite rapidly and significantly after 10 days of metabisulphite incorporation into the bone meal, but no major decrease in the levels of metabisulphite incorporated into the gelatin was observed throughout the 4 weeks of investigation. Reasons for the differences in the stability of metabisulphite in the two products have been suggested.

A comparative study of the lethal effect of metabisulphite on the viability of three bacterial species in bone meal and gelatin.

An investigation into the effect of sodium metabisulphite on the viability of three bacterial species, Salmonella typhimurium 59143, Escherichia coli ES-1 and Pseudomonas aeruginosa 8602, in bone meal and gelatin has been reported in this paper. Methods used in detecting the viability of the bacteria after exposure to metabisulphite-treated bone meal and gelatin have been presented. Results have shown that the bacterial species were all susceptible to metabisulphite in both rendered by-products but in all cases, the micro-organisms were far more susceptible in metabisulphite-treated gelatin than in metabisulphite-treated bone meal. Reasons for the difference in susceptibility were also adduced.

Viability of Salmonella typhimurium in metabisulphite-treated bone meal: effect of inocula and moisture variation on the lethal potency of metabisulphite.

The susceptibility of different inocula of Salmonella typhimurium to the antimicrobial action of various concentrations of metabisulphite in rehydrated bone meal has been investigated. Furthermore, the lethal potency of metabisulphite in the presence of various metabisulphite and moisture concentrations has been examined. It has been shown that the lethal potency of metabisulphite was dependent upon the inocula used in the simulated contamination and the moisture content of the bone meal. A study of the longevity of the potency of metabisulphite has revealed that such a potency could be maintained without a decrease in efficacy for 14--28 days depending on the metabisulphite level in the bone meal.