Surveillance of severe invasive group-G streptococcal infections and molecular typing of the isolates in Japan.

The number of patients with severe invasive group-G streptococcal (Streptococcus dysgalactiae subsp. equisimilis) infections has been increasing in Japan. The emm genotypes and SmaI-digested pulsed-field gel electrophoresis DNA profiles were variable among the strains isolated, suggesting there has not been clonal expansion of a specific subpopulation of strains. However, all strains carried scpA, ska, slo and sag genes, some of which may be involved in the pathogenesis of the disease.

Changing prevalent T serotypes and emm genotypes of Streptococcus pyogenes isolates from streptococcal toxic shock-like syndrome (TSLS) patients in Japan.

We surveyed T serotypes and emm genotypes of Streptococcus pyogenes isolates from streptococcal toxic shock-like syndrome (TSLS) patients. T1 (emm1) remained dominant through 1992 to 2000, but the dominant T3 (emm3.1) strains from 1992 to 1995 disappeared during 1996-2000. Strains of several emm genotypes emerged during 1996-2000, indicating alterations in the prevalent strains causing TSLS.

Serotyping of Streptococcus pyogenes isolated from common and severe invasive infections in Japan, 1990-5: implication of the T3 serotype strain-expansion in TSLS. The Working Group for Group A Streptococci in Japan.

To clarify the relationship between the epidemics of severe invasive group A streptococcal infections (streptococcal Toxic Shock-Like Syndrome: TSLS) and common group A streptococcal infections in Japan, we examined the T serotypes of S. pyogenes strains (group A streptococci) isolated from clinical specimens of the streptococcal infections (17999 cases) in the period 1990-5, including the severe infections (TSLS) (29 cases) in the period 1992-5. Characteristic points of the analyses were: (1) dominant serotypes of the infections in these periods were T12, T4, T1, T28 and TB3264, which were consistently isolated; (2) isolates of T3 rapidly increased through 1990 to 1994 while T6 decreased in the period 1990-3; (3) when Japanese area was divided into three parts, T3 serotype tended to spread out from the north-eastern to the south-western area; (4) strains of T3 and T1 serotypes were dominant in the TSLS. Dominant-serotype strains of streptococcal infections did not always induce severe infections and dominance of T3 serotype in the TSLS seemed to be correlated with the increase of T3 in streptococcal infections. These results may indicate that certain clones of S. pyogenes are involved in the pathogenesis of the TSLS.

[Bacteriological studies on sporadic diarrhea diseases in Oita District, 1985-1996].

Approaching the problem of how close the sporadic diarrhea diseases correlate with epidemics of infectious diarrheas, including food poisonings, bacteriological studies were made on the characteristics of sporadic diarrheas in the past 10 years and analyzed. In collaboration with physicians, mostly pediatricians, in Oita district during 1985 to 1986 and 1989 to 1996, a total of 1707 specimens was obtained from diarrhea patients, suspected of bacterial cause. We have isolated 717 strains from 670 specimens (ca 40% of the total). The majority were; Campylobacter, Salmonella and EPEC with the rate of about 40, 24 and 23% respectively. On the other hand, isolation of Vibrio spp. and Staphylococcus were very few. The yearly trend of detection rates of such major agents were as follows: Campylobacter had the highest rate in the early period, 1989, but thereafter tended to decrease. In contrast, Salmonella continued to increase in rate through the study period until the present when it exceeds that of Campylobacter. This alternation is due primarily to the rapid increase of S. Enteritidis since its recent appearance. VTEC stays at a low rate with a slow increase showing no prevalence so far. From the above results the following may meet with attention. Vibrios and Staphylococci, known as popular agents for food poisonings, seem unlikely to correlate with sporadic diarrheas. Instead, the evidence that recent food poisoning is often represented by Salmonella, especially S. Enteritidis, suggests that epidemics of infectious diarrhea may be attributed to the background of common sporadic diarrheas.

Pathogenesis of Vibrio parahaemolyticus: intraperitoneal and orogastric challenge experiments in mice.

It has been noted that V. parahaemolyticus isolated from patients with food poisoning are almost always thermostable direct hemolysin (TDH)-positive, whereas, isolates from foods or environmental sources are usually TDH-negative. The virulence of V. parahaemolyticus in mice was examined by using intraperitoneal and orogastric challenge models, where the strains used were those isolated from patients and foods with food poisoning and included TDH-positive and -negative. The LD50 in mice was estimated to be approximately 10(7) in the former and 10(8) in the latter challenge model. In the mice killed by challenge, either intraperitoneal or orogastric, the following pathological changes were almost always observed: swelling, redness and fluid accumulation in the small intestine, particularly the upper part of it. Histologically, congestion, edema, and vacuolation were observed in mucosal and submucosal tissues; furthermore, ulceration at tips of some villi was noticed. The lethality and pathological finding in mice due to V. parahaemolyticus were demonstrated similarly in both challenge models and irrespective of the TDH phenotype of the strain used. It will be suggested that the findings in challenged mice may be attributed to enteropathogenic factor(s) other than TDH of V. parahaemolyticus.