Listeria monocytogenes was able to grow in multispecies biofilms formed on stainless steel at 10°C in the presence of bacteria isolated from dairy and meat plant environments. Biofilm L. monocytogenes increased more slowly in the presence of competing microflora than in monoculture, but none of the eight competing isolates studied were able to completely exclude L. monocytogenes from the biofilm within 25 days of incubation. Once a population of L. monocytogenes was established on the surface, it invariably increased in numbers. In biofilms containing a mixture of 4 competitive cultures, L. monocytogenes maintained itself at about 1% of the total population.

No abstract

Use of glucose oxidase as a possible means to inhibit microbial growth on processed poultry was evaluated. Muscle and skin sections of chicken breast were inoculated with Pseudomonas spp. or Salmonella typhimurium and subjected to either: (I) 60 s dip in 2 unitslml of glucose oxidase without glucose supplementution or (2) 60 s dip in 2 units of glucose oxidase with 4 % glucose supplementation. Controi? groups were dipped in sterilized, distilled water. The Pseudomonas and Salmonella populations were determined for each section. Neither enzyme treatment reduced the initial Pseudomonas or Salmonella populations nor did the treatments inhibit the growth of Pseudomonas during the storage period. Salmonella was inhibited by the low temperature. Therefore, a glucose oxidase enzyme treatment has little potential for extending the shelf-life of chicken.

A granular formulation of 1.0% temephos (temephos G) was tested for its efficacy in mosquito larval control, residual effects and effects on non‐target microorganisms. Culex pipiens complex in septic tanks in Yangsan, Republic of Korea were used for this study. Microorganisms in the same septic tanks were used for study of non‐target organisms. After the application of temephos G at the rates of 2.0 and 5.0 mg/L to selected septic tanks, mortalities were recorded for 50 days. The effect of temephos G on non‐target organisms was studied by evaluating its effects on the bacterial populations in the treated septic tanks. It was observed that using 1.0% temephos G at a rate of 2.0 mg/L resulted in 100% mortality against Cx. pipiens larvae by the eighth day after treatment. The residual activity of temephos G was observed to continue for a time; for example 29 days after treatment, average larval mortality rates of >68.0% were observed for both concentrations. At the 50th day after treatment, the mortality rates of the Cx. pipiens larvae were observed to decrease to below 42.7% for both concentrations. Application of temephos G did not have significant effects on the bacteria populations in the septic tanks. Since temephos did not seem to have any major effects on the microorganisms, it was concluded that it is a safe and effective larvicide to use in the septic tanks at a rate of 2.0–5.0 mg/L of 1.0% temephos G.

The effect of fortifying skim milk with non-fat dried milk on growth and proteolysis of psychrotrophic bacteria was determined. Raw skim milk of 8.7% total solids was fortified to 10% and 12% total solids and pasteurized. Growth rates of proteolytic psychrotrophic bacteria were determined in these milks during incubation at 4°C. Proteolysis was determined by measuring the concentration of free amino groups throughout the incubation period. Seven of nine psychrotrophic isolates grew to greater numbers in the fortified milks during the early log phase of growth than they did in the unfortified milks. Growth stimulation was slight in most cases, however, one isolate exhibited a ten-fold increase in numbers when growing in the 10% solids fortified milk. The greatest increases in growth were observed when comparing unfortified milk to milk at 10% solids. Early log phase growth in 12% solids milk was often less than in 10% solids milk but still greater than in unfortified milk. All isolates exhibited increased proteolysis in the fortified milks within 48 h of incubation. These results indicate that increasing the solids content of skim milk with non-fat milk powder produces a microbiological growth medium more suitable for growth and protease production for selected psychrotrophic bacteria.