Risk factors and pathogen characteristics associated with unfavorable outcomes among adults with pneumococcal meningitis in Japan, 2006 to 2016.

PURPOSE: In this study, we aimed to clarify the risk factors associated with unfavorable outcomes in adults with pneumococcal meningitis (PnM). METHODS: Surveillance was conducted between 2006 and 2016. Adults with PnM (n = 268) were followed up for outcomes within 28 days after admission using the Glasgow Outcome Scale (GOS). After classifying the patients into the unfavorable (GOS1-4) and favorable (GOS5) outcome groups, i) the underlying diseases, ii) biomarkers at admission, and iii) serotype, genotype, and antimicrobial susceptibility for all isolates were compared between both groups. RESULTS: Overall, 58.6% of patients with PnM survived,15.3% died, and 26.1% had sequelae. The number of living days in the GOS1 group was highly heterogeneous. Motor dysfunction, disturbance of consciousness, and hearing loss were the commonest sequelae. Of the underlying diseases identified in 68.9% of the PnM patients, liver and kidney diseases were significantly associated with unfavorable outcomes. Of the biomarkers, creatinine and blood urea nitrogen, followed by platelet and C-reactive protein had the most significant associations with unfavorable outcomes. There was a significant difference in the high protein concentrations in the cerebrospinal fluid between the groups. Serotypes 23F, 6C, 4, 23A, 22F, 10A, and 12F were associated with unfavorable outcomes. These serotypes were not penicillin-resistant isolates possessing three abnormal pbp genes (pbp1a, 2x, and 2b), except for 23F. The expected coverage rate of the pneumococcal conjugate vaccine (PCV) was 50.7% for PCV15 and 72.4% for PCV20. CONCLUSIONS: In the introduction of PCV for adults, the risk factors for underlying diseases should be prioritized over age, and serotypes with unfavorable outcomes should be considered.

Diversity of amino acid substitutions of penicillin-binding proteins in penicillin-non-susceptible and non-vaccine type Streptococcus pneumoniae.

PURPOSE: In Japan, the introduction of pneumococcal conjugate vaccine (PCV) in children has decreased vaccine-type (VT) pneumococcal infections caused by penicillin (PEN)-non-susceptible Streptococcus pneumoniae. PEN-non-susceptible strains have gradually emerged among non-vaccine types (NVT). In this study, we aim to investigate the pbp gene mutations and the characteristics of PEN-binding proteins (PBPs) that mediate PEN resistance in NVT strains. MATERIALS AND METHODS: Pneumococcal 41 strains of NVT isolated from patients with invasive pneumococcal infection were randomly selected. Nucleotide sequences for pbp genes encoding PBP1A, PBP2X, and PBP2B were analyzed, and amino acid (AA) substitutions that contribute to ß-lactam resistance were identified. In addition, the three-dimensional (3D) structure of abnormal PBPs in the resistant strain was compared with that of a reference R6 strain via homology modeling. RESULTS: In PEN-non-susceptible NVT strains, Thr to Ala or Ser substitutions in the conserved AA motif (STMK) were important in PBP1A and PBP2X. In PBP2B, substitutions from Thr to Ala, adjacent to the SSN motif, and from Glu to Gly were essential. The 3D structure modeling indicated that AA substitutions are characterized by accumulation around the enzymatic active pocket in PBPs. Many AA substitutions detected throughout the PBP domains were not associated with resistance, except for AA substitutions in or adjacent to AA motifs. Clonal complexes and sequence types showed that almost all NVT cases originated in other countries and spread to Japan via repeat mutations. CONCLUSIONS: NVT with diverse AA substitutions increased gradually with pressure from both antimicrobial agents and vaccines.

Comparative characteristics of the background and blood test findings in adults with pneumococcal pneumonia and invasive pneumococcal disease: A retrospective study.

INTRODUCTION: Invasive pneumococcal disease (IPD) is often fatal, requiring prompt diagnosis and treatment. To evaluate the factors associated with IPD in adults, we retrospectively investigated its characteristics compared to pneumococcal pneumonia without confirmation of invasion (PP). METHODS: Patients >18 years with PP (n = 79) and IPD (n = 53) from whom Streptococcus pneumoniae was isolated were enrolled from two hospitals between 2011 and 2017. Clinical backgrounds, blood test results at admission, initial antimicrobials administered, isolate serotypes, and outcomes were compared between the PP and IPD groups. RESULTS: Patients with IPD exhibited higher mortality (28.3%) than those with PP (2.5%) (p<0.001), regardless of the type of antimicrobials first administered. The majority (80.0%) of fatal cases of IPD were due to vaccine serotypes. Almost all patients with PP (97.4%) and IPD (88.7%) had underlying disease. C-reactive protein (CRP) ≥17.0 mg/dL (odds ratio [OR], 7.1; 95% CI, 2.7-19.0; p<0.001), white blood cell counts <11.0 × 103/µL (OR, 3.2; 95% CI, 1.3-8.4; p = 0.016), and platelet (PLT) counts <16.2 × 104/µL (OR, 2.8; 95% CI, 1.1-7.4; p = 0.036) were significantly more common in IPD. Moreover, 89.5% of cases with both CRP ≥23.8 mg/dL and PLT <18.5 × 104/µL were diagnosed with IPD. CONCLUSION: Laboratory blood test findings at admission, particularly high CRP and low PLT values, are useful early indicators of IPD in adults. These results could be used to initiate rapid and intensive treatment and improve prognosis.

Multiple comorbidities increase the risk of death from invasive pneumococcal disease under the age of 65 years.

INTRODUCTION: Risk factors for death from invasive pneumococcal disease (IPD) have not been clearly established in patients aged under 65 years. We aimed to evaluate contributions of host and bacterial factors to the risk of death from IPD in patients aged under 65 years in Japan. METHODS: In this prospective, observational, multicenter cohort study, patients with IPD (n = 581) aged 6-64 years were enrolled between 2010 and 2017. We investigated the role of host and bacterial factors in 28-day mortality. RESULTS: The mortality rate increased from 3.4% to 6.2% in patients aged 6-44 years to 15.5%-19.5% in those aged 45-64 years. Multivariable analysis identified the following risk factors for mortality: age 45-64 years (hazard ratio [HR], 3.4; 95% confidence interval [CI], 1.6-6.8, p = 0.001), bacteremia with unknown focus (HR, 2.0; 95% CI, 1.1-3.7, p = 0.024), meningitis (HR, 2.1; 95% CI, 1.1-4.0, p = 0.019), underlying multiple non-immunocompromising conditions (HR, 2.6; 95% CI, 1.1-7.4, p = 0.023), and immunocompromising conditions related to malignancy (HR, 2.4; 95% CI, 1.0-5.2, p = 0.039). Pneumococcal serotype was not associated with poor outcomes. CONCLUSIONS: Host factors, including age of 45-64 years and underlying multiple non-immunocompromising conditions, are important for the prognosis of IPD. Our results will contribute to the development of targeted pneumococcal vaccination strategies in Japan.

Molecular epidemiological characterization in mucoid-type Streptococcus pneumoniae isolates obtained from invasive pneumococcal disease patients in Japan.

INTRODUCTION: Streptococcus pneumoniae with a mucoid-type capsule is associated with invasive pneumococcal diseases (IPDs). Despite the introduction of pneumococcal vaccines, IPDs caused by mucoid-type isolates are still prevalent. The present study aimed to characterize mucoid-type S. pneumoniae isolated from IPD patients throughout Japan in 2017 (post-vaccination era). METHODS: A total of 225 mucoid-type isolates were collected. The serotype, antimicrobial susceptibility, and multilocus sequence type of these isolates were determined. RESULTS: The prevalence of IPDs caused by mucoid-type isolates was high in adults, especially in the elderly (≥65 years of age), and prognosis in these patients was significantly poor. Of the mucoid-type isolates, the predominant serotype was serotype 3 (84.4%), and the remaining were serotypes 37 (15.1%) and 8 (0.4%). Antimicrobial susceptibility showed that most mucoid isolates exhibited the penicillin-intermediate resistant S. pneumoniae genotype (gPISP). However, the serotype 3 isolate exhibited the penicillin-resistant S. pneumoniae genotype (gPRSP). This gPRSP isolate was classified into ST166, which is related to serotypes 9 V and 11 strains. Sequence analysis of the capsule-coding regions and its flanking regions indicated that recombination occurred upstream and downstream of the capsule-coding region, suggesting that gPRSP (serotype 9 V/ST166) obtaining the type-3 capsule gene cluster resulted in the emergence of gPRSP (serotype 3/ST166). CONCLUSIONS: Our findings indicated that IPDs caused by mucoid-type S. pneumoniae are still a serious concern and mucoid-type S. pneumoniae with novel phenotype could emerge via capsular switching in response to environmental changes such as introduction of vaccines and improper use of antimicrobial agents.

Drastic reduction in pneumococcal meningitis in children owing to the introduction of pneumococcal conjugate vaccines: Longitudinal analysis from 2002 to 2016 in Japan.

INTRODUCTION: The characteristics of pneumococcal isolates and their associations with outcomes in pediatric meningitis are unclear. This study aimed to clarify serotypes and resistance genotypes of Streptococcus pneumoniae from children with meningitis and evaluate the patient prognoses and backgrounds. METHODS: Large-scale surveillance was conducted from 2002 to 2016 through periods I-V. Serotypes and penicillin (PEN) resistance genotypes were analyzed for pneumococcal isolates (n = 459) and cerebrospinal fluid (CSF) samples (n = 25). Furthermore, underlying diseases (n = 251), prognoses (n = 202), and laboratory data were evaluated. RESULTS: The number of meningitis cases decreased drastically after the introduction of 7-valent pneumococcal conjugate vaccine (PCV7) to -53.6% and after switching to PCV13 to -70.2%. In particular, this reduction was apparent at ≤3 years of age. The proportion of the PCV7 serotype decreased sharply from 70.1% before introduction to 2.6% during period V; however, the non-vaccine type increased from 17.5% to 87.2%. The PEN resistance rate (gPRSP) was decreased from approximately 49% to 12.2% during period V. Among cases revealed prognosis, sequelae and mortality rates were 16.3% and 5.4%, respectively. The rate of the patients with underlying diseases was 26.3% and relatively high in ≥6 years. Laboratory data associated with a poor prognosis were low white blood cell count (<12.7 × 103/µL), low platelet count (<28.1 × 104/µL), low CSF-glucose (<36 mg/dL), and high CSF-protein (≥142 mg/dL). CONCLUSIONS: Changes in serotype prevalence warrant continuous monitoring to observe future trends of pneumococcal meningitis, and further developments in multivalent conjugate vaccines are required.

Effects of Pneumococcal Conjugate Vaccine on Genotypic Penicillin Resistance and Serotype Changes, Japan, 2010-2017.

To clarify year-to-year changes in capsular serotypes, resistance genotypes, and multilocus sequence types of Streptococcus pneumoniae, we compared isolates collected from patients with invasive pneumococcal disease before and after introductions of 7- and 13-valent pneumococcal conjugate vaccines (PCV7 and PVC13, respectively). From April 2010 through March 2017, we collected 2,856 isolates from children and adults throughout Japan. Proportions of PCV13 serotypes among children decreased from 89.0% in fiscal year 2010 to 12.1% in fiscal year 2016 and among adults from 74.1% to 36.2%. Although nonvaccine serotypes increased after introduction of PCV13, genotypic penicillin resistance decreased from 54.3% in 2010 to 11.2% in 2016 among children and from 32.4% to 15.5% among adults. However, genotypic penicillin resistance emerged in 9 nonvaccine serotypes, but not 15A and 35B. Multilocus sequence typing suggested that resistant strains among nonvaccine serotypes may have evolved from clonal complexes 156 and 81. A more broadly effective vaccine is needed.

Etiology of Acute Otitis Media and Characterization of Pneumococcal Isolates After Introduction of 13-Valent Pneumococcal Conjugate Vaccine in Japanese Children.

BACKGROUND: Acute otitis media is a leading cause of childhood morbidity and antibiotic prescriptions. We examined etiologic changes in acute otitis media after introduction of 13-valent pneumococcal conjugate vaccine as routine immunization for Japanese children in 2014. Serotypes, resistance genotypes, antibiotic susceptibilities and multilocus sequence typing of pneumococcal isolates were also characterized. METHODS: Otolaryngologists prospectively collected middle ear fluid from 582 children by tympanocentesis or sampling through a spontaneously ruptured tympanic membrane between June 2016 and January 2017. Causative pathogens were identified by bacterial culture and real-time polymerase chain reaction for bacteria. Serotypes, resistance genotypes, sequence types and susceptibilities to 14 antimicrobial agents were determined for pneumococcal isolates. RESULTS: At least 1 bacterial pathogen was identified in 473 of the samples (81.3%). Nontypeable Haemophilus influenzae (54.8%) was detected most frequently, followed by Streptococcus pneumoniae (25.4%), Streptococcus pyogenes (2.9%) and others. Pneumococci of current vaccine serotypes have decreased dramatically from 82.1% in 2006 to 18.5% (P < 0.001). Commonest serotypes were 15A (14.8%), 3 (13.9%) and 35B (11.1%). Serotype 3 was significantly less frequent among children receiving 13-valent pneumococcal conjugate vaccine compared with 7-valent pneumococcal conjugate vaccine (P = 0.002). Genotypic penicillin-resistant S. pneumoniae accounted for 28.7%, slightly less than in 2006 (34.2%; P = 0.393); the penicillin-resistant serotypes 15A and 35B had increased. Serotypes 15A, 3 and 35B most often belonged to sequence types 63, 180 and 558. CONCLUSIONS: Our findings are expected to assist in development of future vaccines, and they underscore the need for appropriate clinical choice of oral agents based on testing of causative pathogens.

Enhancement of bactericidal activity against group B streptococci with reduced penicillin susceptibility by uptake of gentamicin into cells resulting from combination with ß-lactam antibiotics.

Combined effects of penicillin (PEN) and gentamicin (GM) against Streptococcus agalactiae, i.e. group B streptococci (GBS), are known to occur, but synergy has not been examined in strains with reduced PEN susceptibility, usually called PEN-resistant GBS (PRGBS). We therefore studied combined effects of ß-lactam antibiotics and GM in cultures of 3 PRGBS strains belonging to serotype Ia or III that were isolated from Japanese adults with invasive infections. Killing kinetics were determined at 2-h intervals from 0 to 6 h after exposure to ampicillin (AMP) or cefotaxime (CTX) combined with GM. Concentrations of GM in bacterial cells were measured by liquid chromatography-tandem mass spectrometry. Morphologic changes after exposure to agents were observed by transmission electron microscopy. Combining AMP or CTX with GM synergistically increased bactericidal activity against PRGBS beyond that of either ß-lactam alone. GM concentrations in bacterial cells increased 5- to 8-fold when GM was combined with AMP or CTX. Electron microscopically, bacterial cells showed aggregates of strands and ribosomal damage most likely reflecting enhanced GM uptake into bacterial cells. This uptake appeared to result from cell wall damage caused by ß-lactam antibiotics. This study suggests that combining ß-lactam antibiotics with GM might be useful against severe PRGBS infection.

Molecular Characteristics of Group B Streptococci Isolated from Adults with Invasive Infections in Japan.

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.

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.