Dental caries-associated oral streptococci are called the mutans streptococci, with Streptococcus mutans and Streptococcus sobrinus being the most prevalent caries-associated organisms in humans. Strains of the mutans streptococci are highly conserved within not only mothers and their children but also racial groups, suggesting vertical transmission of this organism within human populations. It has been found that the mother-child infection route of the mutans streptococci can be prevented by simply reducing the amount of the mutans streptococci contained in the mothers' saliva. Moreover, a chlorhexidine varnish reduces the salivary mutans streptococci by an average of 3 logs (99.9%), and moved them below detectable levels. We should attempt to eliminate the infection with the mutans streptococci among Japanese people by attempting to break the infectious chain from mothers to children.

The global polio eradication program is under way with the target year of 2000. We reviewed the program progress, in perspective, from the experience of the global smallpox eradication, which is at present a sole disease ever eradicated by orchestrated global efforts. We concluded that despite substantial efforts being made by the World Health Organization and member states with the current progress, it would require additional some three years, namely 2002. This would safe-guard the success. As of January 2000, there are still at least 22 endemic states in Indian Subcontinent and sub-Saharan Africa. Experiences in smallpox eradication, although the disease is different, indicated that to stop transmission in such a large number of endemic states took more than three years, assuming that further support would come toward the final goal.

Laboratory studies were carried out to ascertain the current susceptibility status of adult and larval stages of the Culex tritaeniorhynchus mosquito, vector of Japanese encephalitis, to various insecticides used under public health programs in India. The present study revealed that exposure of adult mosquitoes to diagnostic concentrations of DDT - 4.0%, malathion - 5.0%, fenitrothion - 1.0%, and propoxur - 0.1% could induce only 50.0, 10.0, 15.0, and 5.0% mortality, respectively, indicating that the species was resistant to all of these insecticides. The LT₅₀ and LT₉₅ values calculated using diagnostic concentrations of DDT, malathion, fenitrothion, and propoxur were found to be 56.4 and 136, 138 and 272, 185 and 258, and 187 and 249 min, respectively. However, when adult mosquitoes were exposed to the diagnostic concentration of synthetic pyrethroids, viz., deltamethrin -0.025%, permethrin - 0.25%, and lambdacyhalothrin - 0.1%, 100.0% mortality was observed, indicating that the species was highly susceptible to these adulticides. Larval susceptibility tests carried out using diagnostic dosages of DDT- 0.008, temephos- 0.02, fenthion- 0.008, fenitrothion- 0.125, and malathion- 0.005 mg/l failed to induce any mortality, indicating that larvae were resistant to these larvicides. The LC₅₀ and LC₉₀ values calculated for commonly used larvicides, viz., temephos and fenthion, were 0.1511 and 1.9098, and 0.6151 and 2.395 mg/l, respectively. Increase in tolerance level were estimated at 95.5- and 299.4-fold when these LC₉₀ values were compared with diagnostic dosages of temephos and fenthion, respectively.

We examined the distribution of multidrug-resistant Salmonella enterica serotype Typhimurium definitive phage type 104 (DT104) among Japanese livestock from1973 to 1998. The 144 S. Typhimurium field isolates were tested for susceptibility to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline, kanamycin, trimethoprim, nalidixic acid, and norfloxacin. Thirty-six of 68 strains which exhibited resistance to five or more antimicrobials (ACSSuT+) were identified as DT104. Results of plasmid profiling showed that all DT104 strains retain a 90-kb virulence plasmid, while 20 of 36 strains possessed a few additional small plasmids ranging from 2 to 4 kb. These results showed that DT104 strains have existed in Japanese livestock since 1990, and that this phage type may be an important pathogen for cattle in Japan.

The molluscicidal activity of saponins isolated from the plant Anagallis arvensis (Primulaceae) was studied against schistosome intermediate hosts, Biomphalaria glabrata and Oncomelania quadrasi. Strong molluscicidal activity was found in two compounds called desglucoanagalloside B and anagalloside B. Their structures were identified on the basis of chemical and spectroscopic analyses and their activities are comparable to that of the synthetic molluscicide, niclosamide.