A collaborative study of a method for enumeration of probiotic enterococci in animal feed.

AIMS: Validation of an enumeration method to be used as an official control method in the framework of Council Directive 70/524/EEC for probiotic enterococci used as feed additives. METHODS AND RESULTS: Twenty laboratories in 12 European countries carried out a collaborative study. A plate count method using bile esculin azide (BEA) agar was used. Precision data in terms of repeatability (r) and reproducibility (R) of the method using different feeding stuffs and three inoculation levels were determined. Enterococci were present in the samples as a single component or in mixtures with other probiotic feed additives. The enumeration of enterococci on BEA agar showed a relative standard deviation (RSD)r of 1.5-3.6% and an RSD(R) between 2.9 and 7.4%. BEA agar was selective for enterococci in the presence of other probiotic micro-organisms such as pediococci, lactobacilli and yeast. CONCLUSIONS: For routine analysis of viable enterococci concentrations in feeding stuffs, the use of BEA is recommended. This methodology is not applicable for mineral feeds. SIGNIFICANCE AND IMPACT OF THE STUDY: An official control method for enumeration of authorized probiotic enterococci in feeding stuffs was validated. The results are intended for consideration for adoption as CEN and ISO standards.

Measurements and predictions of growth for Listeria monocytogenes and Salmonella during fluctuating temperature II. Rapidly changing temperatures.

Growth of Listeria monocytogenes and Salmonella was examined during various rates of increase and decrease in temperature from and to the minimum for growth. Growth was little affected by even the most rapid changes and injury or lag was not observed. Subsequent investigations of growth during periods of rapid variation in temperature from and to temperatures below the growth minimum again had little effect and growth was satisfactorily predicted using the dynamic model of Baranyi and Roberts [Int. J. Food Microbiol. 23 (1994) 277] in conjunction with the data of Food Micromodel.

Comparison of selective media for the recovery and enumeration of probiotic yeasts from animal feed.

Six selective media (acidified malt extract agar, CHROMagar Candida, dichloran rose bengal chloramphenicol, molybdate, oxytetracycline glucose yeast extract and Petrifilm Yeast and Mould agar) were examined for the recovery of three yeasts commonly used in animal feeds as probiotic additives (Candida pintolopesii, C. saitoana and Saccharomyces cerevisiae). The highest recovery was obtained on oxytetracycline glucose yeast extract agar, although this was susceptible to overgrowth by moulds. CHROMagar Candida also gave good recovery and species were easily discriminated by the differential colour formation of colonies.

Predictions of growth for Listeria monocytogenes and Salmonella during fluctuating temperature.

We studied the predictive performance of a dynamic modelling approach, combined with predictions from the Food MicroModel software, applied to the growth of Listeria monocytogenes and Salmonella in pasteurised milk, chicken liver pâté and minced chicken, under constant as well as fluctuating temperatures. We found that, in general, the accuracy of a prediction under fluctuation temperature was similar to that under constant temperature. Generally, there was a good agreement between predictions and observations. However, the growth of Listeria monocytogenes in pasteurised milk was inhibited largely by the natural flora present.

The growth of Treponema hyodysenteriae and other porcine intestinal spirochaetes in a liquid medium.

A new simple method for the preparation of a liquid medium containing rabbit serum for the propagation of Treponema hyodysenteriae and other porcine intestinal spirochaetes is described. The medium, when dispensed in shallow layers and sealed under 10 per cent CO2 in nitrogen, had a redox potential not greater than -125mV and an initial pH of about 6.9 when buffered with bicarbonate. Growth of T hyodysenteriae developed more rapidly and viable counts reached higher levels at 42 degrees C than at 37 degrees C. Viable counts increased at least 10,000-fold after two to five days' incubation, depending on the temperature. Growth could be initiated from small inocula that failed to produce colonies on blood agar. Using a 1 per cent inoculum, the medium supported the growth of two strains of T hyodysenteriae through 10 serial passages.

The occurrence of salmonellas, mycobacteria and pathogenic strains of Escherichia coli in pig slurry.

Ninety-eight samples of pig slurry from 54 farms were examined for the presence of salmonellas, porcine enteropathogenic strains of haemolytic Escherichia coli and mycobacteria. Salmonellas were isolated from 12 farms (22%) and enteropathogenic E. coli from 13 farms (24%). Pathogenic mycobacteria were not isolated. Salmonellas were isolated from 7 of 16 farms (44%) stocked with 'minimal disease' pigs compared with only 5 of 38 farms (13%) stocked with conventionally reared pigs. Conversely enteropathogenic coliforms were isolated from 3 of 16 farms (19%) stocked with 'minimal disease' pigs compared with 10 of 38 farms (26%) stocked with conventionally reared pigs.

An investigation into the potential hazard to animal health of effluent sludge from dairy factories.

Sixty-three samples of the more solid material (sludge) separated from the effluent plants of dairy factories were examined for the presence of salmonellas and brucellas. Salmonellas were isolated from two samples (S. heidelberg. [1]; S. indiana [1]. No brucellas were isolated. None of the samples supported the growth of S. dublin. Salmonellas added to effluent sludge at a concentration of 10(6) organisms/ml. survived less than 70 days. The sludge from dairy factory effluent plants does not appear to be a source for the spread of salmonellosis or brucellosis.