Category: Infectious Agents Surveillance Report (IASR) Published Date Hits: 3528
(IASR 36: 147-149, August 2015)
Many streptococci that cause suppurative disease in humans are β-haemolytic. They are classified according to the antigenicity of the cell wall polysaccharides; group A [Group A Streptococcus (GAS); mostly Streptococcus pyogenes], group B [Group B Streptococcus (GBS); mostly S. agalactiae], and group C or G [Group C or G Streptococcus (GCS or GGS); mostly S. dysgalactiae subsp. equisimilis (SDSE)]. GAS causes acute pharyngitis and other acute suppurative infections, such as cellulitis; scarlet fever and streptococcal toxic shock syndrome (STSS) by bacterial toxin; and rheumatic fever (see p. 160 of this issue) and acute glomerulonephritis by immunological mechanisms. GBS causes bacteremia or meningitis in neonates and sepsis or pneumonia in adults. SDSE causes septicemia and STSS in adults.
1. National Epidemiological Surveillance of Infectious Diseases (NESID)
Group A streptococcal (GAS) pharyngitis: Under the Infectious Diseases Control Law, GAS pharyngitis is a Category V infectious disease that is monitored at approximately 3,000 pediatric sentinel (see http://www.nih.go.jp/niid/images/iasr/36/426/de4261.pdf for notification criteria).
Number of cases reported annually during 2011 to 2015 was 264,043, 276,090, 253,089, 303,160 and 202,830, respectively (as of week 24 for year 2015). GAS pharyngitis exhibits seasonality and the number of patients increases from winter to spring each year (Fig. 1). In 2014-2015, the number of patients began to increase from the end of 2014 and by week 24 of 2015, the weekly report per sentinel attained the highest level (3.64) in the past 10 years (Fig. 1, see p. 149 of this issue). The cumulative reported number of patients per sentinel from the 1st week of 2014 to the 24th week of 2015 was highest in Yamagata, Tottori, Niigata, Fukuoka, Hokkaido, Ishikawa, Yamaguchi, Shimane, Kagoshima and Fukui prefectures (see p. 149 of this issue). An outbreak in a care facility was also reported (see p. 150 of this issue). In 2015 (as of week 24), 84% of the GAS pharyngitis patients were 9 years of age or younger, and 5-year-olds were the most reported age, occupying 9.4% of all reported cases.
Streptococcal toxic shock syndrome (STSS): Any GAS, GBS or SDSE can cause STSS. STSS is a Category V infectious disease that requires notification of all cases (see http://www.nih.go.jp/niid/images/iasr/36/426/de4262.pdf for notification criteria). Since April 2006, notifications include all cases in which samples from the normally sterile sites or organs were positive for any GAS, GBS or SDSE, and manifesting shock with two or more of the following: liver failure, renal failure, acute respiratory distress syndrome, disseminated intravascular coagulation, soft tissue inflammation, acute generalized exanthema and central nervous system involvements.
The number of STSS cases has been increasing since 2011; 241, 201, and 270 cases were reported in respective years from 2012 to 2014 (Table 1). In 2015, number of reported cases reached 204 within the first 24 weeks (see p. 153 of this issue). During 2012-2014, STSS was reported from all 47 prefectures in Japan; prefectures that reported more than 1 patient per 100,000 population were Toyama (1.86), Tottori (1.38), Fukui (1.13) and Ehime (1.07). Median age of patients was 67 years and male to female ratio 1.1 (370 males vs. 342 females). Among 712 patients, 207 (29%) were deceased at the time of notification (Fig. 2). The median age of deceased patients was 72 years. Seventy-six percent of deceased patients died within 3 days after disease onset. Group A (58%) was the most frequent causative streptococci identified among STSS in 2012-2014, followed by group G (27%), which are currently increasing (Table 1).
2. Pathogen surveillance
Since 1992, when the first STSS case was reported in Japan, Streptococcus Reference Center (SRC), jointly established by prefectural and municipal public health institutes (PHIs) and the National Institute of Infectious Diseases (IASR 18: 25-26, 1997; IASR 31: 76-77, 2010; IASR 33: 211-212, 2012), has been conducting pathogen surveillance, including T-serotyping, genotyping of emm gene (encoding M protein responsible for pathogenicity of S. pyogenes and SDSE), and antimicrobial susceptibility tests.
1) T-serotyping: In 2011-2014, PHIs conducted T-serotyping for 947-1,240 isolates annually from GAS pharyngitis cases (Fig. 3a in p.149 of this issue). During 2011-2012, T1 and T12 were dominant, while in 2013-2014, T12 and TB3264 became dominant (Fig. 3a). On the other hand, among the 321 total isolates from STSS cases, T-serotype distribution (Fig. 3b in p.149 of this issue) was as follows: 153 (48%) T1, 58 (18%) TB3264, 23 (7%) T12, and 20 (6%) T28. T1 was dominant and occupied 60-70% in 2010-2011 (IASR 33: 209-210, 2012), although decreased to 26-49% in 2012-2014 (Fig. 3b). Among streptococci isolates from GAS pharyngitis and STSS cases in metropolitan Tokyo, many were similarly TB3264 in 2013-2014 (see p. 151 of this issue).
2) emm typing: As for emm typing, which can provide epidemiologically useful information, among 243 GAS isolates from STSS cases in 2012-2014, isolates with emm1 genotype occupied 41% (100 isolates) (see p. 154 of this issue).
3) Antimicrobial susceptibility: The first choice for treating β-haemolytic streptococci infections is penicillin-derivatives. The 1,608 isolates from GAS pharyngitis patients in 13 prefectures from 2011 to 2014 were all susceptible to β-lactam antibiotics, although about 60% were resistant to macrolides and 25% resistant to lincomycin and tetracycline (see p. 152 of this issue). The recommended therapy for STSS is combination of high dose administration of penicillin-derivative antibiotics and clindamycin. The 243 isolates from STSS patients during 2012-2014 were all susceptible to penicillin G, ampicillin, cefazolin, cefotaxime, meropenem and linezolid. However, 28 isolates (12%) were resistant to clindamycin (see p. 155 of this issue).
3. Group B Streptococcus (GBS): GBS may cause not only STSS but also invasive streptococcal infection in neonates via vertical transmission. Recently, invasive GBS infection cases have been increasing, with the rate of invasive GBS infection among neonates within 3 months of birth in 2014 reaching 1.8 per 10,000 births (see p. 158 of this issue). Among bacterial meningitis cases reported from approximately 500 sentinel hospitals under NESID, GBS has been the most frequent (bacterial meningitis caused by Haemophilus influenzae and Streptococcus pneumoniae that had been dominant until 2011 are now monitored separately).
Recently, GBS with reduced penicillin susceptibility (PRGBS) has emerged. Among all GBS isolates, about 15% of GBS were PRGBS and 10% were PRGBS with resistance to both macrolides and fluoroquinolones (see p. 156 of this issue).
Additional comments: The reported number of GAS pharyngitis and STSS cases has been increasing in recent years. Several food poisoning outbreaks due to S. pyogenes have been reported (IASR 34: 266-267 & 268-269, 2013). Pediatric sentinel-based monitoring of GAS cases and notification of all STSS cases should be further strengthened. Pathogen surveillance should be further intensified by means of T-serotyping, emm typing and antimicrobial susceptibility monitoring. The pathogen surveillance data should be promptly fed back to clinicians so that the information can be used for understanding of ongoing streptococcal epidemics and for early diagnosis and therapy. Streptococcal infection caused by S. suis that claimed many lives in Southeast Asia has been reported from Japan (see p. 159 of this issue) but do not exhibit the typical β-hemolysis (IASR 26: 241-242, 2005). Paying attention to streptococci at large beyond those associated with β-hemolysis is important.