Incidence survey of acute otitis media in children in Sado Island, Japan--Sado Otitis Media Study (SADOMS).

BACKGROUND: Acute otitis media (AOM) is one of the most common forms of bacterial infection and cause for clinic visits in children. The incidence of AOM was 0.9-1.2 episodes per person-year during the first 2 years of life in previous reports conducted before 2000. The aim of this study was to 1) evaluate the latest AOM incidence in pediatric outpatients and 2) identify the bacterial pathogens from these patients and ascertain their serotypes and resistance. METHODS: The study was conducted in a closed population, involving all pediatricians and otolaryngologists in Sado Island allowing accurate determination of AOM incidence. In each month, one week was assigned as "surveillance week", and all outpatients with acute illness aged 0-18 years examined during the surveillance weeks were enrolled. AOM was diagnosed on the basis of otoscopic findings and clinical symptoms were recorded. Specimens were collected from the nasopharynx or middle ear cavity of AOM patients and examined for bacteria. Antimicrobial susceptibilities, serotypes, and molecular typing for resistance were determined among Streptococcus pneumoniae and Haemophilus influenzae. RESULTS: In total, 8,283 clinic visits were conducted, and 354 episodes (4.3%, 95% CI: 3.9-4.7%) among 312 children were diagnosed as AOM. The incidence of AOM was highest in children of 1 year of age (0.54 episodes/child/year, 95% CI: 0.44-0.64). Serotype coverage of 7- and 13-valent pneumococcal conjugate vaccines in this study were 38.0% (95% CI: 29.3-47.3) and 62.8% (95% CI: 53.6-71.4), respectively. Of 122 H.influenzae isolates available for typing, 120 were nontypeable and 2 were type b. A high proportion of S. pneumoniae isolates (46%) showed resistance to penicillin. Approximately half of H. influenzae isolates had genetic markers for beta-lactamase-negative ampicillin-resistance. CONCLUSIONS: Approximately 4-5% of pediatric outpatients, even without AOM-related symptoms, had AOM in our study. Pediatricians as well as otolaryngologists should check the tympanic membrane findings of all pediatric outpatients.

Molecular epidemiology of methicillin-resistant Staphylococcus aureus isolated from children in a community with low antimicrobial pressure in Japan.

Sado Island in Japan is an area with low antimicrobial pressure. A total of 41 community-onset methicillin-resistant Staphylococcus aureus (MRSA) isolates were obtained from pediatric outpatients and healthy children between August 2009 and January 2012, and genotyping and antimicrobial susceptibility testing of the MRSA isolates were performed. Additionally, the sources of MRSA isolated from healthy 1-month-old neonates were assessed. All isolates were negative for the Panton-Valentine leukocidin genes. Our data showed a lower prevalence of staphylococcal cassette chromosome (SCC)mecII on Sado Island (31.7% in total and 46.7% in healthy carriage) than that in the other areas of Japan, suggesting that a low level of antimicrobial use may be related to a low SCCmecII carriage rate in the community. To our knowledge, this is the first report of sequence type (ST)81/SCCmecIVg strains as well as the novel ST strain (ST2180/SCCmecIVa) in Japan. In addition, we detected an arginine catabolic mobile element (ACME)-arcA-positive ST764/SCCmecIIa clone that could disseminate successfully in the community. Intrafamilial transmission was observed in neonates identified with the SCCmecIV MRSA strains, and these strains were genetically typed as community-associated MRSA; the transmission routes of the remaining SCCmecIIa MRSA (genetically typed as healthcare-associated MRSA) strains could not be defined. In this study, we have shown that multiple MRSA strains can circulate in a community even under low antimicrobial pressure.

Genotyping of Haemophilus influenzae type b in pre-vaccination era.

Identification of Haemophilus influenzae type b (Hib) in asymptomatic carriers is critical to control the spread of disease. This study was conducted between January 2008 and August 2011 as part of a birth cohort study in Sado Island, Japan, to elucidate the prevalence of Hib and its clones in a specific region. Nasopharyngeal cultures were obtained from 349 subjects at 4-, 7-, 10-, 18-, and 36-month health checkups and analyzed for H. influenzae. The Hib and nontypeable H. influenzae detection rates ranged from 0 to 1.5% (12 isolates) and from 7.9 to 32.9%, respectively. Twelve pediatric patients diagnosed with invasive or non-invasive Hib infections during the study period were also enrolled. The Hib isolates were analyzed for carriage of the beta-lactamase gene and ftsI mutations, and multilocus sequence type (MLST, ST type). Of the 24 Hib isolates, 18 (75%) were ST54, 5 (21%) were ST190, and 1 isolate (4%) was ST95. All of the ST190 isolates were genetically beta-lactamase-negative ampicillin-susceptible isolates, while all but one of the ST54 isolates were genetically beta-lactamase-positive amoxicillin/clavulanic acid-resistant isolates. The geographic distribution of Hib isolates in the study period was scattered. There were 2 day-care cases and 1 family case of Hib infection. The ST54 and ST190 strains circulated in Sado Island and were detected in both asymptomatic carriers and patients. We note that surveillance of healthy subjects to identify Hib carriers is important to understand the transmission of Hib.

Prevalence of methicillin-resistant Staphylococcus aureus among children in a region with controlled antimicrobial use.

Since 2002, we have conducted a series of intervention programs in Sado Island, Japan, to increase awareness of the appropriate use of antimicrobials among public and health-care staff. The objective of our study was to determine the antimicrobial susceptibility of Staphylococcus aureus among children in a semi-closed geographic region with controlled antimicrobial use. The average hospital visit-based rate for antimicrobial drug prescription drastically decreased from 535 per 1,000 clinic visits before the intervention programs to 45-75 per 1,000 clinic visits after the intervention programs (P < 0.0001). We obtained 1,260 clinical isolates of S. aureus from 957 pediatric outpatients aged 0-15 years between 2002 and 2010 at Sado General Hospital. The prevalence of methicillin-resistant S. aureus (MRSA) in the final year of the study (2010, 7.9%) was significantly lower than that in the early period of the study (2003, 23.6%; P < 0.001). All tested S. aureus isolates were susceptible to trimethoprim/sulfamethoxazole, teicoplanin, linezolid, and vancomycin. The prevalence of gentamicin-resistant S. aureus in isolates from skin lesions was significantly higher than in isolates from other lesions (41.3% versus 28.5%; P < 0.05). In conclusion, prevalence of MRSA in children in our study population could be decreased by eliminating unnecessary antimicrobial drug prescriptions.