Although maintaining the health of elderly individuals and young children in developed countries is very important and desirable, these populations are always at risk of infection due to a poor or weakened immune function. Therefore, we examined the immunostimulatory effects of yogurt, with a focus on the roles of exopolysaccharide (EPS), which is produced by lactic acid bacteria. We selected Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 (OLL1073R-1) as a high EPS producer. EPS produced by this strain induced the spleen cells of mice to produce interferon-gamma in an in vitro assay. The oral administration of EPS or yogurt fermented with OLL1073R-1 and Streptococcus thermophilus (OLL1073R-1 yogurt) increased NK cell activity in the spleen cells of mice and prolonged the survival periods of mice infected with an influenza virus. Furthermore, the risk of elderly individuals being infected by the common cold and flu was lower after the consumption of OLL1073R-1 yogurt than after consumption of milk. In healthy male college students, increases in specific antibodies against vaccine antigens were greater after the intake of OLL1073R-1 yogurt than after the intake acidified milk.

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In recent years, Matrix Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) has been adopted as a method for routine microbial identification in clinical, pharmaceutical and food microbiology laboratories. In microbial identification by MALDI-TOF MS, bacteria and fungi are identified by acquiring mass spectra within the range of 2,000 to 20,000 Da, a range containing peaks derived from proteins of microbial cells. Compared to other technologies for microbial identification, this method brings results more rapidly by simpler sample preparation, at a lower cost. In addition, it has higher accuracy than the conventional methods, using the molecular method as the reference method. Since colonies on solid culture media are used as samples for spectra acquisition, not only differences in strains of the same species, but also differences in culture conditions result in differences in spectra. Moreover, each commercialized MALDI-TOF MS system for microbiology identification has different databases and algorithms. Users need to consider these characteristics of MALDI-TOF MS microbial identification, especially for adding species or strain information to a database and performing other microbiology applications. To utilize this technology as a method for microbial identification, it is important to understand its advantages and pitfalls to perform identification and further applications.

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Clostridium difficile is a Gram-positive, obligately anaerobic, spore-forming bacillus which is the causative pathogen for pseudomembranous colitis (PMC), and it is associated with a large proportion of inpatient cases of antibiotic-associated diarrhea (AAD). Although C. difficile is known to be present in the normal intestinal microbiota, its growth is inhibited by other intestinal bacteria under normal conditions, and it is the disruption of intestinal microbiota by administration of antibiotics that allows C. difficile to overgrow and produce toxins (e.g., toxin A and toxin B) leading to C. difficile-associated diarrhea (CDAD). Withdrawal of antibiotics and/or administration of oral vancomycin or metronidazole are effective treatments for CDAD. However, recurrent cases are observed in 10 to 35% of CDAD and have become a difficult clinical problem. The main reservoirs of C. difficile are asymptomatic colonized persons and CDAD patients. C. difficile is transmitted through the fecal-oral route and can survive in a hospital environment for a long time in a spore form. It has been reported that the prevalence of C. difficile colonization is correlated to the duration of hospitalization. Some recurrent cases of CDAD are due to the same strain of C. difficile that caused the first episode persisting in the intestine after antibiotic treatment. Therefore, in the treatment and prevention of CDAD and/or recurrent CDAD, the prevention of a disruption of intestinal microbiota by the restriction of antibiotic use and the maintenance or restoration of normal microbiota colonizaiton are important, in addition to treatment with oral vancomycin/metronidazole and prevention through general contact precautions and environmental cleaning. Probiotics are used in the treatment and prevention of CDAD mainly as an adjunct to the antibiotic therapy for the purpose of maintaining or restoring the normal intestinal microbiota, and its efficacy has been reported by many researchers. From the viewpoint that probiotics have an inhibitory effect on the growth of pathogens and can restore the intestinal microbiota, they are seen as one of most theoretically suitable agents for the prevention of CDAD. However, their efficiencies are different across species or strains of probiotics and scientific evidence and proof based on large-scale clinical trials using each species or strain are desired.

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