The Topic of This Month Vol.21 No.11(No.249)

Streptococcal infections in Japan, 1996-2000
(IASR 2000; 21: 240-241)

According to the National Epidemiological Surveillance of Infectious Diseases (NESID) established in 1981, identified and suspected cases of pharyngitis (including scarlet fever) caused by group A Streptococcus (Streptococcus pyogenes) were previously reported under the name "streptococcal infections" from sentinel clinics (pediatricians and general physicians). From some clinics, pharyngeal specimens are sent to prefectural and municipal public health institutes (PHIs) for bacterial examinations. Under the Infectious Diseases Control Law, enacted in April 1999, the disease was renamed to "group A streptococcal pharyngitis", but still remained as a member of the category IV infectious diseases to be reported from sentinel clinics (pediatricians only). Under the same law, "severe invasive streptococcal infections" was added in the category IV notifiable infectious diseases.

Group A streptococcal pharyngitis

The reported cases of group A streptococcal pharyngitis per sentinel clinic being decreasing every summer (Fig. 1), counted at 30.7 in 1996, 34.9 in 1997, 34.1 in 1998, 39.9 in 1999, and 42.1 (117,134 cases) in 2000 as of the 41st week. The age distributions of cases showed a stability during the period from 1996 through 1999 (Fig. 2 and see IASR Vol.15, No.11).

T serotyping is seen as a method that can be used for serological classification of S. pyogenes. The T serotypes obtained at PHIs during 1982-1999 are shown in Fig. 3. The predominant T serotypes were T12, T1 and T4, all of which accounted for over 50% of all the isolates in each year. Yearly changes were hardly seen in the ratios of these serotypes as well as T11, T18, T22, T28, and TB3264 to the total isolates. On the other hand, serotypes T3, T6, and T25 resulted in large yearly changes; T3 showed sudden changes with peaks during 1985-1986 and 1993-1994, T6 with peaks during 1988-1989 and in 1997, and T25 with a peak in 1999. Some T serotypes keep the yearly ratios to the total isolates constant, while some change abruptly from one year to another.

Severe invasive streptococcal infections

From the late 1980s, toxic-shock-like syndrome (TSLS) caused by S. pyogenes (severe invasive infections due to so-called "flesh-eating bacteria") has become a serious problem in Western as well as in Asian countries. Although only few cases have such underlying diseases as immunodeficiency, symptoms suddenly develop in many cases. The early symptoms are pharyngitis, melalgia, fever, and blood pressure loss. These symptoms progress very rapidly and are fulminant from the onset. Once attacked, the patients may develop necrosis of soft tissues, acute kidney failure, adult respiratory distress syndrome (ARDS), disseminated intravascular coagulopathy (DIC), and multiorgan failure (MOF) within scores of hours, leading to shock and death.

Since 1992, when a typical TSLS patient was first reported in Japan, this disease has been under surveillance (see IASR, Vol. 18, No. 2). By August 2000, the Streptococcus Reference Center of the Association of Public Health Laboratories for Microbiological Technology analyzed 64 strains isolated from TSLS patients for serotypes. Serotype T1 was found in 31 cases, accounting for 47% of all isolates, followed by T3, T12, and T28 (Fig. 4A). As stated earlier, group A streptococcal pharyngitis is caused mainly by serotypes T12, T1, and T4 (Fig. 4B), nevertheless neither T4 nor T12 necessarily is the main serotype causing TSLS. A similar tendency has been reported in other countries. It is of interest that with sudden increase of serotype T3 (with a peak during 1993-1994) TSLS cases also increased. Thereafter, with the decrease in pharyngitis-originating isolates, TSLS cases due to serotype T3 showed the same pattern.

The TSLS patients notified after the enactment of the Infectious Disease Control Law in April 1999 counted at 22 in 1999 and 37 in 2000 (as of October 16, 2000); fatal cases at the time of notification numbered at 25 (Fig. 5). The patients were found in 26 different prefectures in the whole country, showing no regional differences in the incidence (Fig. 6). The average age of the patients stood at 55.7 (Fig. 7).

Attention has recently been paid to Vibrio vulnificus that also evokes fluminant symptoms. The severe invasive infections with this organism tend to occur among those who have such an underlying disease as hepatic disease and ingest contaminated fish or shellfish (see p. 242-243 of this issue) or when the organisms invade through their open wounds. It resembles TSLS clinically in many respects, but for therapy, penicillins or clindamycin is used for TSLS, while in general the third generation cephems or minocycline is used for V. vulnificus infections. Adequate differential diagnosis between them, therefore, is important.

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