Minoru Okazaki

Individual risk factors associated with nasopharyngeal colonization with Streptococcus pneumoniae and Haemophilus influenzae: a Japanese birth cohort study.

Background: The first step in a bacterial disease is the establishment of nasopharyngeal carriage. Methods: We conducted a birth cohort study to identify factors associated with colonization in healthy children and evaluate the serotype distributions and resistances of Streptococcus pneumoniae/Haemophilus influenzae. Nasopharyngeal cultures were obtained from 349 subjects at 5 time points coinciding with health checkups (4, 7, 10, 18 and 36 months). Results: A total of 551 S. pneumoniae (penicillin resistance rate: 46.3%) and 301 H. influenzae (ampicillin resistance rate: 44.5%) isolates were obtained from 1654 samples. In this study, 47.5% and 60.9% of S. pneumoniae isolates were included in the serotypes of 7- and 13-valent pneumococcal conjugate vaccines, respectively. Analyzing by Cox proportional hazards models, cohabiting older sibling(s) attending day-care (hazard ratios: 2.064–3.518, P < 0.001) and an early start of day-care attendance by the subjects themselves (2.259–2.439, P < 0.001) were associated with a higher risk of early colonization regardless of their susceptibility. Recent exposure to antimicrobials was also significantly associated with increased risk of colonization (odds ratios: 2.032–2.999, P < 0.001) but not with resistance rates. This data indicated that introduction of appropriate antimicrobial usage in areas of overuse of antimicrobials could contribute to lower colonization of S. pneumoniae/H. influenzae, resulting in a decrease in the absolute number of resistant isolates. Conclusions: Strategies to control transmission at day-care centers or from older sibling(s) as well as appropriate use of antimicrobials are essential for reducing colonization and the absolute number of resistant isolates.

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.

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 2xa0day-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.

Resistance of nasopharyngeal pathogens and antimicrobial prescription rates for children in an area under controlled antimicrobial use.

Background: To reduce the spread of drug-resistant pathogens, appropriate use of antimicrobials is an indispensable measure. From January 2002, we undertook campaigns about antimicrobial treatment in Sado Island, Japan. Methods: The subjects were born in 1996 (group-1996) or during 2002–2004 (group-2002–2004) and received outpatient treatment at our hospital. We evaluated the subjects’ medical information from patient records during their first 3 years of life. Demographic data, duration of breast-feeding, and attending a day-care center (DCC) were evaluated using a questionnaire. Results: Average visit-based antimicrobial prescription rates significantly decreased from 535 for group-1996, to 70 for group-2002–2004 per 1000 hospital visits (P < 0.001). The rate of cephalosporin prescriptions significantly decreased (77.1%–16.7%; P < 0.001), while amoxicillin (0.8%–29.5%) and macrolides (21.0%–52.4%) significantly increased (P < 0.001). Regarding 417 nasopharyngeal cultures from group-2002–2004, 77.8% (179/230) of Streptococcus pneumoniae strains were nonsusceptible to penicillin. For Haemophilus influenzae strains, 30.6% (59/193) were nonsusceptible to ampicillin. Living with older sibling(s) and early DCC attendance were associated with carriage of resistant pathogens. Conclusions: In a closed area under controlled antimicrobial use, our data indicated that decreasing antimicrobial prescriptions alone could not achieve elimination of resistant pathogens. Strategies to control transmission at DCCs or from older sibling(s) are also essential.

Molecular epidemiology and serogroup 6 capsular gene evolution of pneumococcal carriage in a Japanese birth cohort study

Antibiotic resistance in Streptococcus pneumoniae is a major concern worldwide. However, it is unclear whether resistance is associated with only a few highly prevalent clones or numerous and diverse clones. We monitored 349 healthy children and obtained nasopharyngeal cultures at five time points coinciding with health check-ups (4, 7, 10, 18 and 36 months) between 2008 and 2012. A total of 497 S. pneumoniae isolates from 257 healthy children were characterized using capsular serotyping, multilocus sequence typing and antibiotic resistance genotyping (ermB, mefA/E and pbp mutations). Among these isolates, 25 serotypes and 66 sequence types (STs) were found, including 24 new STs with 11 new alleles. Although resistance was present in a variety of ST clones, most of the clones (57/66, 86.4u200a%) had one specific resistant or susceptible genotype. Of 233 phenotypically penicillin-non-susceptible isolates, 196 (84.1u200a%) belonged to only six clones, comprising ST90(6B), ST236(19F), ST242(23F), ST3787(6A), ST1437(23F) and ST338(23A) and their variants. We concluded that drug-resistant S. pneumoniae is associated with a limited number of highly prevalent clones that are capable of adapting to the community setting. Furthermore, we analysed the capsular gene evolution in serogroup 6. The strain ST2924(6D) was probably the result of recombination of a 3563 bp fragment of the capsule locus acquired by an ST2924(6C) strain from an ST90(6B) or ST2924(6B) strain. Compared with previous studies, our results showed a different recombination site (wciN and wzx) and a different cps profile (8-7-11), indicating that serogroup 6 strains have multiple sites for cps recombination as a mechanism of vaccine escape.

Influenza Virus Shedding in Laninamivir-Treated Children upon Returning to School.

The current School Health and Safety Act in Japan states that children with influenza infection should stay home until day 6(th) after symptoms onset. This was an amendment of a previous version recommending school return on day 3 after defervescence. Here, we investigated the duration of fever and virus shedding after laninamivir treatment in 7 children infected with influenza A(H3N2) virus and 21 children with influenza B virus in relation to the school return timing recommended by the School Health and Safety Act during the 2011-2012 influenza season. Nasal discharge was collected on the first, second, and third hospital visits and virus titers were assessed by virus culture and real-time PCR. Duration of fever after laninamivir treatment was 1 day longer for influenza B than for influenza A(H3N2). Virus detection rates with 50% tissue culture infectious dose and viral RNA were highest at the first visit and gradually decreased at subsequent visits. Virus positivity rates were detectable at the time of defervescence in less than half of the enrolled patients (14.3-42.9%). Virus shedding rates were similarly low (0.0-19.0%) on day 3 or later from defervescence and on day 6 or later from fever onset (school return dates per the old and current School Health and Safety Act) regardless of the influenza type. In conclusion, despite the higher efficacy of laninamivir against A(H3N2) viruses than B viruses, viral shedding is low after return to school for both types, regardless of the version of the School Health and Safety Act.

Successful Combined Treatment for Atrophic Thyroiditis With Growth Hormone Deficiency

Persons with untreated atrophic thyroiditis develop a permanent height deficit. Adequate thyroxine replacement therapy can improve growth and the probability of attaining normal adult height. However, height deficit is related to duration of thyroxine deficiency, regardless of the adequacy of thyroxine replacement therapy after diagnosis.1 Several studies reported that use of adjunctive therapy with growth hormone (GH) and gonadotropin-releasing hormone agonist (GnRHa) to improve the final height of patients.2-5 The rationale for this therapy is to prolong the growth period by inhibiting pubertal progression and delaying epiphyseal fusion,6 although GH deficiency in atrophic thyroiditis patients usually improves after L-thyroxine treatment. n nWe report a case of autoimmune atrophic thyroiditis in a boy who presented with GH deficiency even after his enlarged pituitary gland had decreased in size. Combined treatment with GH, GnRHa, and L-thyroxine was successful in allowing the patient to attain normal adult height.