[Survival of Salmonella Weltevreden and S. Senftenberg in black tiger shrimp under frozen storage].

Survival of Salmonella in black tiger shrimps during frozen storage was investigated following our previous study on Salmonella contamination in frozen shrimps imported into Japan. Salmonella (S.) Weltevreden and S. Senftenberg were inoculated onto the surface and inside of black tiger shrimps without the shell. After storage at -10 degrees C, -20 degrees C and -30 degrees C for 12 weeks, the Salmonella population decreased in all cases; the decrease was smallest at the lowest temperature. Viability of Salmonella inoculated onto the surface of the shrimp was greater than that inside the shrimp. In addition, viability of S. Senftenberg was greater than that of S. Weltevreden. These results suggest that hygienic handling during thawing of shrimps is important from the viewpoint of Salmonella contamination.

[Antibiotic susceptibility of Neisseria meningitidis from healthy and diseased persons in Japan].

We examined the susceptibilities of 100 Neisseria meningitidis strains isolated between 1990 and 2004 to 12 antimicrobial agents, finding the MIC50 to be 0.031 microg/mL and that of MIC90 of benzylpenicillin (PCG), a type of penicillin, to be 0.063 microg/mL. Two strains showed intermediate resistance (MIC of 0.125-0.25 microg/mL). Two strains of the same origin also showed intermediate resistance (0.25-1 microg/mL) to ampicillin (ABPC). For cephems, MIC50 and MIC90 of cefotaxime (CTX) were both 0.004 microg/mL, while the MICs of ceftriaxone (CTRX) were all 0.004 microg/mL, showing the strongest antibacterial spectrum. The three carbapenems surveyed meropenem (MEPM), panipenem (PAPM), and imipenem (IPM) also had a strong antibacterial spectrum in ascending order, with the MIC50 and MIC90 of MEPM, which was lowest, being 0.008 microg/mL and 0.016 microg/mL. Some 97% of MICs for ciprofloxacin (CPFX) were 0.004 microg/mL but 3 strains showed resistance (0.125 microg/mL). No difference was seen between MICs of N. meningitidis strains originated from meningitis patients, patients other than meningitis, and healthy carriers. No difference was seen in MICs by serogroup (A, B, C, Y, W135 and NG).

[Bacterial contamination in an egg-breaking factory and its control].

From January to November, 2003, bacterial contamination was surveyed in a small egg-breaking factory that produced non pasteurized liquid egg. Test egg samples were taken at various stages of the egg processing operation. Salmonella Enteritidis was isolated from liquid egg yolk and liquid egg white on October, but was not found in any other samples (50 liquid egg samples, 21 containers and 94 attached production facilities and gloves). The data suggest that the contamination rate (3.8%) is lower than those reported previously. Levels of bacterial standard plate counts, gram-positive bacterial counts and gram-negative bacterial counts were in the ranges of 2 to 5 log CFU/g, 2 to 3 log CFU/g, 2 to 5 log CFU/g, respectively. Liquid egg containers returned from customers was contaminated with bacteria at the level of 8 log CFU per container. However, washing and application of a sanitizer containing sodium hypochlorite reduced the bacterial counts.

[Evaluation of selective plating media for the detection of heat- or freeze-injured Staphylococcus aureus].

The efficacy of Baird-Parker (BP) agar, mannitol-salt-egg yolk (MSEY) agar and mannitol salt (MS) agar in detecting Staphylococcus aureus FRI-100 heated at 52 degrees C for 20 min in 100 mmol/L potassium phosphate buffer was determined. Brain heart infusion agar with 1% pyruvate (BHIP agar) supported the highest recovery of injured cells and was used as the control medium. Of the three selective media, significantly higher recovery of heat-injured cells was observed on BP agar than MSEY agar, and the poorest recovery was observed on MS agar (p < 0.05). Low recovery of unheated cells was obtained for MS compared with other media (p < 0.05). A reduction in populations occurred gradually in reagent-grade water stored for 14 days at -20 degrees C. There was no significant difference between BHIP agar and MS agar in the number of freeze-injured cells recovered from 1 to 14 days.