A phage set for typing Bacillus cereus was developed . Ninety-six phages were isolated from 85 soil samples using B. cereus pilot strains for 36 H-serovars as indicator strains. Eleven phages were selected based on their stability and host range, and were classified into 5 groups using a neutralization test with antisera . We used 5 phages, Φa, Φb, Φc, Φd and Φe as a typing phage set. The typing phage set typed 36 pilot strains for H-serovars into 17 phage patterns (83.3% typeable) and 11 phage patterns (100% typeable), 25 isolates from powdered fish meal samples into 9 phage patterns (48% typeable) and 9 phage patterns (100% typeable), and 100 isolates from soil samples into 24 phage patterns (79% typeable) and 14 phage patterns (100% typeable) at routine test dilution (1×RTD) and 100×RTD, respectively.
The sensitivities of 3 test methods, LB-BGBL and 2 chromogenic substrate medium methods (minimal medium o-nitrophenyl-D-galactopyranoside-4-methyl-umbelliferyl-β-Dglucuronide: MMO and 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside: X-GAL methods) for the detection of E. coli and coliforms present in spring water were compared. A total of 158natural spring water and simulated spring water samples were examined. The pH range for the bacteria to grow in LB-BGLB was 4.5-9.5, while that in chromogenic substrate media was 5.0-9.0. It was found that Na2S (equivalent to≥50mg/l of H2S) and Cu (≥20 mg/l) in the culture media inhibited the growth of bacteria. Complete coincidence of the results by the 3 test methods was obtained for the detection of E. coli, while, 92.4%coincidence was obtained for coliforms. The coincidences between the 2 test methods for coliforms were between 92.4% and 94.3% with the highest coincidence found between the MMO and X-GAL methods. The practical use of the MMO and X-GAL methods was evaluated. The culture media in the positive reaction by the MMO method turned yellow which sometimes caused difnculty when reading the results, since many natural spring water samples were slightly yellow. A positive reaction by X-GAL turned blue which was easier to read, thus the X-GAL method may be superior over the MMO method. These results indicate that the chromogenic substrate medium methods are rapid and easy and can be used for the detection of E. coli and coliforms in spring water if pH, H2S and Cu are properly adjusted.
Between 1986 and 1996, bacterial contamination of 1, 445 commercial raw fish and shellfish in Tama, Tokyo was investigated. Each year, the median of standard plate counts decreased, whereas that of the coliform group was nearly constant. Vibrio parahaemolyticus was detected in 71 (4.9%) samples, and high contamination was observed in shellfish such as ark shell (25 samples). Staphylococcus aureus was also detected in 77 (5.3%) samples, especially tuna (24 samples). In addition, Bacillus cereus was found in 25 (1.7%) samples, but no Salmonella was detected. By introducing enriched cultures for S. aureus, the detection ratio markedly increased, and marked contamination in tuna was observed. In the testing of coagulase and enterotoxin on the 105 strains of S. aureus, all isolates were typable to 8 different kinds of coagulase type, but enterotoxigenicity was confirmed in only 29 strains.