Katsutoshi Saruta

Use of immunoglobulin enriched bovine colostrum against oral challenge with enterohaemorrhagic Escherichia coli O157:H7 in mice.

An immunoglobulin enriched bovine colostrum preparation, IMMULAC™ (New Zealand Dairy Group, Cambridge, New Zealand), contains antibodies against various bacterial antigens. In the present study, we investigated the protective effects of a commercial bovine colostrum preparation against infections with enterohaemorrhagic Escherichia coli (EHEC) O157:H7 in a murine model. Balb/c mice were given drinking water containing streptomycin for 3 days before and following oral challenge with streptomycin‐resistant EHEC O157:H7 strain (O157‐SMR). In mice pretreated with streptomycin, EHEC O157:H7 maintained stable levels of bacterial colonization in the intestines for the 3‐week experimental time period. Oral administration of colostrum resulted in rapid decrease in the bacteria numbers compared with administration of skim‐milk. Colostrum showed no direct in vitro bactericidal properties against either EHEC O157:H7. When sections prepared from cecum walls of streptomycin‐pretreated mice were incubated in vitro with EHEC O157:H7, the colostrum significantly prevented the attachment of the organisms to the sections when compared with skim‐milk. These results indicate that oral administration of bovine colostrum effectively protects mice against food‐borne infections by inhibiting bacterial attachment to the intestinal mucous membrane, colonization and growth in the intestinal tract.

Genetic identification of Staphylococcus aureus by polymerase chain reaction using single-base-pair mismatch in 16S ribosomal RNA gene

Staphylococcus aureus is the most predominant and important pathogen in clinical microbiology. A DNA amplification assay using the polymerase chain reaction (PCR) was designed to identify S. aureus through a single‐base‐pair mismatch in the sequences of staphylococcal 16S ribosomal RNA (16S rRNA) genes. It was able to detect and identify S. aureus without requiring additional analytical techniques. Twenty‐eight staphylococcal and non‐staphylococcal strains were tested to verify the specificity of the assay, and only S. aureus strains gave a positive reaction. It may be possible to provide immediate and exact information for the identification of S. aureus.