PATHOGENICITY TESTING OF HEAT-RESISTANT M ESOPHILIC SPOREFORMERS FROMUHT-MILK

Highly heat resistant mesophilic sporeformers (HRS) were first detecte d in UHT-milk in 1985 when new regulations (EC-Directive 85/397) conce rning the bacterial cell count came into effect. By genetical and bioc hemical characterization a new Bacillus species was established. To pr event a possible health hazard for the consumer the HRS has to be test ed for pathogenicity. For this reason 15 HRS strains were tested in a cell-culture modell and in embryonized chicken eggs. The cell culture was evaluated for cytotoxicity by morphological examination of the cel l and an enzyme-release test with no cytotoxic effects observed. The c hicken embryos were examined for pathological signs, teratogenic effec ts, growth retardation and the relative embryo weight. These parameter s were statistically evaluated by analysing variances by a linear cont rast method and additional Tukey-, Scheffe- and I-test. No significant differences between eggs inoculated with HRS strains and noninoculate d strains were observed. In combining the results of cytotoxicity test s and chicken embryo assays the HRS can be estimated most likely as ap athogenic.