Takeaki Wajima

Changes in Capsule and Drug Resistance of Pneumococci after Introduction of PCV7, Japan, 2010–2013

Drastic changes threaten overall effectiveness of this vaccine.

Serotype Changes and Drug Resistance in Invasive Pneumococcal Diseases in Adults after Vaccinations in Children, Japan, 2010-2013

Pneumococcal conjugate vaccination of children is associated with penicillin-resistant Streptococcus pneumoniae in adults.

Direct identification of Streptococcus agalactiae and capsular type by real-time PCR in vaginal swabs from pregnant women

Most group B streptococcus (GBS) infections in newborns are with capsular type Ia, Ib, or III. To prevent these infections more effectively, we developed a real-time PCR method to simultaneously detect GBS species and identify these 3 capsular types in vaginal swab samples from women at 36-39 weeks of gestation. DNA to be detected included those of the dltS gene (encoding a histidine kinase specific to GBS) and cps genes encoding capsular types. PCR sensitivity was 10 CFU/well for a 33-35 threshold cycle. Results were obtained within 2 h. Direct PCR results were compared with results obtained from cultures. Samples numbering 1226 underwent PCR between September 2008 and August 2012. GBS positivity rates by direct PCR and after routine culture were 15.7% (n = 192) and 12.6% (n = 154), respectively. Sensitivity and specificity of direct PCR relative to culture were 96.1% and 95.9%. Of GBS positive samples identified by PCR, capsular types determined directly by real-time PCR were Ia (n = 24), Ib (n = 32), and III (n = 26). Real-time PCR using our designed cycling probe is a practical, highly sensitive method for identification of GBS in pregnant carriers, allowing use of prophylactic intrapartum antibiotics in time to cover the possibility of unexpected premature birth.

Molecular Characterization of Invasive Streptococcus dysgalactiae subsp. equisimilis, Japan

This infection is an increasing threat to aging populations.

Nonhemolytic Streptococcus pyogenes Isolates That Lack Large Regions of the sag Operon Mediating Streptolysin S Production

ABSTRACT Among nonhemolytic Streptococcus pyogenes (group A streptococcus) strains (n = 9) isolated from patients with pharyngitis or acute otitis media, we identified three deletions in the region from the epf gene, encoding the extracellular matrix binding protein, to the sag operon, mediating streptolysin S production.

Prevalence of macrolide-non-susceptible isolates among β-lactamase-negative ampicillin-resistant Haemophilus influenzae in a tertiary care hospital in Japan.

β-Lactamase-negative ampicillin-resistant (BLNAR) Haemophilus influenzae account for a large portion of H. influenzae clinical isolates in Japan. The aim of this study was to clarify the antimicrobial susceptibility of BLNAR H. influenzae clinical isolates as well as the annual changes in susceptibility. BLNAR H. influenzae isolates were collected from a tertiary care hospital from 2007 to 2012. Antimicrobial susceptibility testing was performed and resistance mechanisms were analysed. All of the isolates (n=304) had amino acid substitutions in penicillin-binding protein 3 (PBP3) and isolates were classified by these amino acid substitutions: R517H or N526K (class I); S385T and R517H (class II); and S385T and N526K (class III). Classes I, II and III represented 8.2% (n=25), 9.5% (n=29) and 81.6% (n=248) of the isolates, respectively; 2 isolates could not be classified because they had a PBP3 with a substantially mutated FtsI transpeptidase domain. All of the isolates were highly susceptible to fluoroquinolones and carbapenems. The number of clarithromycin (CAM)-non-susceptible [minimum inhibitory concentration (MIC) ≥16μg/mL] H. influenzae isolates increased significantly between 2010 and 2012. Moreover, CAM-non-susceptible H. influenzae isolates were prevalent among class II and class III BLNAR H. influenzae. Multilocus sequence typing (MLST) of the CAM-resistant (MIC ≥32μg/mL) H. influenzae isolates showed that they were not specific sequence types, suggesting that CAM resistance may occur in any isolates. These results raise concern regarding the occurrence of multidrug-resistant BLNAR H. influenzae.

Clarithromycin Resistance Mechanisms of Epidemic β-Lactamase-Nonproducing Ampicillin-Resistant Haemophilus influenzae Strains in Japan.

ABSTRACT The aim of this study was to clarify the clarithromycin resistance mechanisms of β-lactamase-nonproducing ampicillin-resistant Haemophilus influenzae strains. In all clarithromycin-resistant strains, the transcript level of acrB was significantly elevated, and these strains had a frameshift mutation in acrR. Introduction of the acrR mutation into H. influenzae Rd generated a clarithromycin-resistant transformant with the same MIC as the donor strain. Our results indicate that the acrR mutation confers clarithromycin resistance by the increasing the transcription of acrB.

Molecular characteristics of group B streptococci isolated from adults with invasive infections in Japan

ABSTRACT Streptococcus agalactiae (group B streptococcus) isolates (n = 443) obtained from Japanese adults with invasive infections between April 2010 and March 2013 were analyzed for capsular serotype, multilocus sequence type (ST), antibiotic susceptibility, and resistance genes. Among these cases, bacteremia without primary focus was the most common variety of infection (49.9%), followed by cellulitis (12.9%) and pneumonia (9.0%). Concerning patient age (18 to 59, 60 to 69, 70 to 79, 80 to 89, and 90 years old or older), the incidence of pneumonia increased in patients in their 70s and 80s (P < 0.001), while younger patients (18 to 59 and 60 to 69 years old) were more likely to have abscesses (P < 0.05). The mortality rate was 10.2% for all ages. The most common capsular serotype was Ib (39.5%), followed by V (16.0%), III (13.8%), VI (9.5%), and Ia (8.6%). The main ST of serotype Ib strains was ST10, which belonged to clonal complex 10 (88.0%). The predominant clonal complexes of serotypes V and III, respectively, were 1 (78.9%) and 19 (75.4%). Among these isolates, 9 strains (2.0%) were identified as group B streptococci with reduced penicillin susceptibility, reflecting amino acid substitutions in penicillin-binding protein 2X (PBP2X). In addition, 19.2% of all strains possessed mef(A/E), erm(A), or erm(B) genes, which mediate macrolide resistance, while 40.2% of strains were resistant to quinolones resulting from amino acid substitutions in GyrA and ParC. Our data argue strongly for the continuous surveillance of microbial characteristics and judicious antibiotic use in clinical practice.

Live non-invasive Shigella dysenteriae 1 strain induces homologous protective immunity in a guinea pig colitis model

A non‐invasive live transconjugant Shigella hybrid (LTSHΔstx) strain was constructed from a Shiga toxin gene deleted mutant of Shigella dysenteriae 1 by introducing a plasmid vector pPR1347 that carried a lipopolysaccharide biosynthesis gene (rfb and rfc) of Salmonella typhimurium. In guinea pigs, four successive oral administrations of LTSH Δstx showed complete protection against rectal challenge with wild type S. dysenteriae 1 strain. Exponential increase of the serum IgG and IgA titer against lipopolysaccharide of LTSH Δstx was observed during immunization, peaked on day 28 and remained at that level until day 35 after the initiation of the immunization. In intestinal lavage of the immunized animals, significant increase of IgA titer against lipopolysaccharide of LTSH Δstx was also observed. These data suggested that LTSH Δstx could be a useful candidate to induce protective immunity against S. dysenteriae 1 infection.

Host Factors and Biomarkers Associated with Poor Outcomes in Adults with Invasive Pneumococcal Disease

Background Invasive pneumococcal disease (IPD) causes considerable morbidity and mortality. We aimed to identify host factors and biomarkers associated with poor outcomes in adult patients with IPD in Japan, which has a rapidly-aging population. Methods In a large-scale surveillance study of 506 Japanese adults with IPD, we investigated the role of host factors, disease severity, biomarkers based on clinical laboratory data, treatment regimens, and bacterial factors on 28-day mortality. Results Overall mortality was 24.1%, and the mortality rate increased from 10.0% in patients aged ˂50 years to 33.1% in patients aged ≥80 years. Disease severity also increased 28-day mortality, from 12.5% among patients with bacteraemia without sepsis to 35.0% in patients with severe sepsis and 56.9% with septic shock. The death rate within 48 hours after admission was high at 54.9%. Risk factors for mortality identified by multivariate analysis were as follows: white blood cell (WBC) count <4000 cells/μL (odds ratio [OR], 6.9; 95% confidence interval [CI], 3.7–12.8, p < .001); age ≥80 years (OR, 6.5; 95% CI, 2.0–21.6, p = .002); serum creatinine ≥2.0 mg/dL (OR, 4.5; 95% CI, 2.5–8.1, p < .001); underlying liver disease (OR, 3.5; 95% CI, 1.6–7.8, p = .002); mechanical ventilation (OR, 3.0; 95% CI, 1.7–5.6, p < .001); and lactate dehydrogenase ≥300 IU/L (OR, 2.4; 95% CI, 1.4–4.0, p = .001). Pneumococcal serotype and drug resistance were not associated with poor outcomes. Conclusions Host factors, disease severity, and biomarkers, especially WBC counts and serum creatinine, were more important determinants of mortality than bacterial factors.