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The application of the polymerase chain reaction (PCR) for detection of Clostridium botulinum types A, B and E in foods, environmental and clinical samples was evaluated and compared to the mouse bioassay. Samples inoculated with 10, 100 and 1000 spores of Cl. botulinum types A and B included pasteurized milk, UHT milk, infant formula, infant faeces, meat juice, canned tuna, mushrooms, blood sausage and soil. Clostridium botulinum type E spores were inoculated into fish eggs, canned tuna, picked herring, raw fish and soil at similar levels. Spores were added to 2.5 g of each sample with the exception of soil which was inoculated in 10 g samples. The presence of Cl. botulinum in sample enrichments was determined by both PCR and the bioassay. An overall correlation of 95.6% was observed between PCR results and the mouse bioassay. Of the total of 114 samples tested there was disparity between the mouse bioassay and the PCR in three samples of soil inoculated with 100 type A or E spores and 10 type B spores per 10 g, respectively, and two samples of infant faeces inoculated with 10 type A or B spores per 2.5 g. All of these samples gave negative animal results and positive PCR results.

Paired batches of unpurified and commercially purified oysters from a polluted estuary were examined for a range of indicator and pathogenic microorganisms on 16 occasions over a period of 1 year. Aerobic plate counts of purified oysters (geometric mean of all samples 4.8 × 102/g) were generally lower than those of unpurified oysters (geometric mean of all samples 1.2 × 103/g). Coliforms and Escherichia coli were detected considerably less frequently, and usually at lower levels in purified than in unpurified oysters. Three batches of purified oysters contained unacceptably high concentrations of E. coli. The purification process had little impact on the incidence or concentration of Vibrio parahaemolyticus, which was present at low levels (up to 48/g) in 12 batches of both unpurified and purified oysters. Non-01 serotypes of V. cholerae were also present in purified oysters. Viruses were not detected. In a subsequent survey, 54 oyster samples from 25 different purification plants and 5 estuaries were examined. Twenty one samples contained V. parahaemolyticus at levels up to 48/g and one contained V. cholerae (non-01). Ten samples contained E. coli. The results indicate that small numbers of potentially pathogenic vibrios are frequently a part of the microflora of purified oysters.