Prevalence of Streptococcus pneumoniae serotypes causing invasive and non-invasive disease in South East Asia: a review

Prevalence of Streptococcus pneumoniae serotypes causing pneumococcal diseases in the Chinese Mainland: A systematic review and meta-analysis

Pneumococcal disease (PD) caused by Streptococcus pneumoniae (Sp) continues to be a global public health concern. Monitoring the prevalence and shift of Sp serotypes causing PD is critical for vaccination and local policies for PD management. A systematic review of published work on pneumococcal serotype distribution in the Chinese Mainland from January 1997 to July 2023 was conducted. The literature was searched in Medline, Embase, the Cochrane Library, Web of Science, CNKI, and Wanfang. Distribution of the Sp serogroups/serotypes was presented as count and proportion. Pooled distributions were calculated using a double arcsine transformation. Subgroup analyses were performed according to isolate location, strain source, patient age, period, and clinical manifestation. In total 36,477 Sp isolates in 159 studies were included. In the Chinese Mainland, the highest proportion of Sp in PD was serotype 19F, followed by 19A, 23F, 14 and 6B. Serotype 19F was the most predominant circulating serotype through all time periods. PD cases caused by non-vaccine serotypes showed a significant increase after 2019. In summary, from 1997 to 2023, the top 10 prevalent Sp serotypes causing PD in the Chinese Mainland were 19F, 19A, 6, 23F, 14, 6B, 6A, 3, 15B, and 9 V. Although the distribution of serotypes varied according to the subgroups, the increase in non-vaccine serotypes (e.g. 15A), and diversity distribution of serotypes 6A and 3 in different age groups should not be ignored.

Epidemiology of pneumococcal meningitis in sentinel hospital surveillance of Viet Nam, 2015-2018

BACKGROUND

Streptococcus pneumoniae (S. pneumoniae), Haemophilus influenzae (H. influenzae), and Neisseria meningitidis (N. meningitidis) are leading causes of childhood bacterial meningitis and preventable by vaccines. The aim of this hospital-based sentinel surveillance is to describe the epidemiological characteristics of pneumococcal meningitis, including disease burden, and to provide baseline data on pneumococcal serotype distribution to support decision making for pneumococcal conjugate vaccine (PCV) introduction in Vietnam.

METHODS

Surveillance for probable bacterial meningitis in children 1-59 months of age is conducted in three tertiary level pediatric hospitals: one in Hanoi and two in Ho Chi Minh City. Cerebrospinal fluid (CSF) specimens were collected via lumbar puncture from children with suspected meningitis. Specimens were transferred immediately to the laboratory department of the respective hospital for cytology, biochemistry, and microbiology testing, including culture. PCR testing was conducted on CSF specimens for bacterial detection (S. pneumoniae, H. influenzae, and N. meningitidis) and pneumococcal serotyping.

RESULTS

During 2015-2018, a total of 1,803 children with probable bacterial meningitis were detected; 1,780 had CSF specimens available for testing. Of 245 laboratory-confirmed positive cases, the majority were caused by S. pneumoniae (229,93.5%). Of those with S. pneumoniae detected, over 70% were caused by serotypes included in currently available PCV products; serotypes 6 A/6B (27.1%), 14 (19.7%), and 23 F (16.2%) were the most common serotypes. Children with laboratory-confirmed pneumococcal meningitis were more likely to live in Hanoi (p < 0.0001) and children 12-23 months of age were at greater odds (OR = 1.65, 95% CI: 1.11, 2.43; p = 0.006) of having confirmed pneumococcal meningitis compared to children < 12 months of age when compared to those without laboratory-confirmed bacterial meningitis. Additionally, children with confirmed pneumococcal meningitis were more likely to exhibit signs and symptoms consistent with clinical meningitis compared to negative laboratory-confirmed meningitis cases (p < 0.0001) and had a greater odds of death (OR = 6.18, 95% CI: 2.98, 12.86; p < 0.0001).

CONCLUSIONS

Pneumococcal meningitis contributes to a large burden of bacterial meningitis in Vietnamese children. A large proportion are caused by serotypes covered by PCVs currently available. Introduction of PCV into the routine immunization program could reduce the burden of pneumococcal meningitis in Viet Nam.

Retrospective database analysis for clinical diagnoses commonly associated with pneumococcal diseases in the Malaysian healthcare system over a 3-year period (2013-2015)

BACKGROUND

Pneumococcal disease caused by Streptococcus pneumoniae is an important cause of morbidity and mortality across all ages, particularly in younger children and older adults. Here, we describe pneumococcal disease hospitalizations at Ministry of Health (MoH) facilities in Malaysia between 2013 and 2015.

METHODS

This was a retrospective databases analysis. Tabular data from the Malaysian Health Data Warehouse (MyHDW) were used to identify microbiologically confirmed, pneumococcal disease hospitalizations and deaths during hospitalization, using hospital-assigned ICD-10 codes (i.e., classified as meningitis, pneumonia, or non-meningitis non-pneumonia). Case counts, mortality counts, and case fatality rates were reported by patient age group and by Malaysian geographic region.

RESULTS

A total of 683 pneumococcal disease hospitalizations were identified from the analysis: 53 pneumococcal meningitis hospitalizations (5 deaths and 48 discharges), 413 pneumococcal pneumonia hospitalizations (24 deaths and 389 discharges), and 205 non-meningitis non-pneumonia pneumococcal disease hospitalizations (58 deaths and 147 discharges). Most hospitalizations occurred in children aged < 2 years. Crude mortality was highest among children aged < 2 years (for all three disease categories), among adults aged ≥ 65 years (for pneumococcal pneumonia), or among adults aged 65-85 years (for non-meningitis non-pneumonia pneumococcal disease). The case fatality rate, all ages included, was 5.8% for pneumococcal pneumonia, 9.1% for pneumococcal meningitis, and 28.3% for non-meningitis non-pneumonia pneumococcal disease.

CONCLUSIONS

Our study is the first to document pneumococcal disease hospitalizations and deaths during hospitalization in Malaysia. Although this database analysis likely underestimated case counts, and the true disease burden could be even greater, the study demonstrates a substantial burden of pneumococcal disease. Public health measures, including vaccination, would significantly contribute to the prevention of hospitalizations and deaths associated with pneumococcal disease in Malaysia.

Adult non-invasive pneumococcal pneumonia in Portugal is dominated by serotype 3 and non-PCV13 serotypes 3-years after near universal PCV13 use in children

Introduction

Non-invasive pneumococcal pneumonia (NIPP) is possibly the most frequent infection by Streptococcus pneumoniae in adults. However, the herd effect of vaccinating children in adult NIPP (aNIPP) remains poorly characterized.

Methods

We determined the serotype distribution and antimicrobial susceptibility of isolates causing aNIPP (>18 years) in 2016-2018 in Portugal; 3 years with near universal vaccination of children with the 13-valent conjugate vaccine (PCV13), following over a decade of significant PCV use in children in the private market.

Results and discussion

Among the 1,149 aNIPP isolates, the most frequent serotypes detected were: 3 (n = 168, 14.6%), 11A (n = 102, 8.9%), 19F (n = 70, 6.1%), 23A and 23B (n = 62, 5.4% each), 9N (n = 60, 5.2%), 8 and 29/35B (n = 43, 3.7% each); together accounting for 53% of all isolates. The serotype distribution causing aNIPP was stable in 2016-2018, with the serotypes included in PCV7 still being important causes of disease and serotype 3, a PCV13 serotype, remaining the leading cause of aNIPP. There was an increase in penicillin non-susceptibility from 17% in 2016 to 24% in 2018 (p = 0.018). Some PCV13 serotypes, such as 14, 19A and 19F were associated to resistance, which may have contributed to their persistence. The fact that close to 20% of aNIPP is caused by four non-vaccine serotypes (23A, 23B, 9N, and 29/35B) and that there were significant differences in serotype distribution relative to invasive disease, stress the importance of maintaining the surveillance of these infections. The lack of a continued herd effect from vaccinating children and the significant fraction of aNIPP potentially preventable by PCV13 (30%), PCV15 (34%), PCV20 (53%) and the 23-valent polysaccharide vaccine (61%) underscore the importance of considering the broader use of pneumococcal vaccines in adults.

Assessment of interleukin 1 receptor antagonist (IL-1RA) levels in children with and without community acquired pneumonia: a hospital based case-control study

The primary objective was to compare serum interleukin-1 receptor antagonist (IL-1RA) levels in cases of community acquired pneumonia (CAP) and healthy age-gender-matched controls. The secondary objective was to compare serum IL-1RA levels in cases which were positive or negative for Streptococcus pneumoniae in the blood by real-time-polymerase chain reaction (RT-PCR). Hospitalized children with World Health Organization defined CAP, aged 2-59 months, were included as cases. Healthy controls were recruited from the immunization clinic of the hospital. Enzyme-linked immunosorbent assay (ELISA) test was used to detect serum IL-1RA levels. Identification of S.pneumoniae in blood was done by RT-PCR. From October 2019 to October 2021, 330 cases (123, 37.27% female) and 330 controls (151, 45.75% females) were recruited. Mean serum IL-1RA levels (ng/ml) were 1.36 ± 0.95 in cases and 0.25 ± 0.25 in controls (p < 0.001). Within cases, serum IL-1RA levels were significantly higher in those whose RT-PCR was positive for S.pneumoniae. Thus serum IL-1RA levels may be evaluated as a surrogate marker of S.pneumoniae in future studies.

The Molecular Approaches and Challenges of Streptococcus pneumoniae Serotyping for Epidemiological Surveillance in the Vaccine Era

Streptococcus pneumoniae (pneumococcus) belongs to the Gram-positive cocci. This bacterium typically colonizes the nasopharyngeal region of healthy individuals. It has a distinct polysaccharide capsule - a virulence factor allowing the bacteria to elude the immune defense mechanisms. Consequently, it might trigger aggressive conditions like septicemia and meningitis in immunocompromised or older individuals. Moreover, children below five years of age are at risk of morbidity and mortality. Studies have found 101 S. pneumoniae capsular serotypes, of which several correlate with clinical and carriage isolates with distinct disease aggressiveness. Introducing pneumococcal conjugate vaccines (PCV) targets the most common disease-associated serotypes. Nevertheless, vaccine selection pressure leads to replacing the formerly dominant vaccine serotypes (VTs) by non-vaccine types (NVTs). Therefore, serotyping must be conducted for epidemiological surveillance and vaccine assessment. Serotyping can be performed using numerous techniques, either by the conventional antisera-based (Quellung and latex agglutination) or molecular-based approaches (sequetyping, multiplex PCR, real-time PCR, and PCR-RFLP). A cost-effective and practical approach must be used to enhance serotyping accuracy to monitor the prevalence of VTs and NVTs. Therefore, dependable pneumococcal serotyping techniques are essential to precisely monitor virulent lineages, NVT emergence, and genetic associations of isolates. This review discusses the principles, associated benefits, and drawbacks of the respective available conventional and molecular approaches, and potentially the whole genome sequencing (WGS) to be directed for future exploration.

Rapid identification of Streptococcus pneumoniae serotypes by cpsB gene-based sequetyping combined with multiplex PCR

BACKGROUND/PURPOSE

Streptococcus pneumoniae is an important human pathogen that causes invasive infections in adults and children. Accurate serotyping is important to study its epidemiological distribution and to assess vaccine efficacy.

METHODS

Invasive S. pneumoniae isolates (n = 300) from 27 teaching hospitals in China were studied. The Quellung reaction was used as the gold standard to identify the S. pneumoniae serotypes. Subsequently, multiplex PCR and cpsB gene-based sequetyping methods were used to identify the serotypes.

RESULTS

Based on the Quellung reaction, 299 S. pneumoniae isolates were accurately identified to the serotype level and 40 different serotypes were detected. Only one strain was non-typeable, and five most common serotypes were identified: 23F (43, 14.3%), 19A (41, 13.7%), 19F (41, 13.7%), 3 (31, 10.3%), and 14 (27, 9.0%). Overall, the multiplex PCR method identified 73.3 and 20.7% of the isolates to the serotype and cluster levels, respectively, with 1.7% of the isolates misidentified. In contrast, the cpsB sequetyping method identified 59.0 and 30.3% of the isolates to the serotype and cluster levels, respectively, and 7% were misidentified.

CONCLUSIONS

The cpsB gene sequetyping method combined with multiplex PCR, can greatly improve the accuracy and efficiency of serotyping, besides reducing the associated costs.

Modeling of pneumococcal serogroup 10 capsular polysaccharide molecular conformations provides insight into epitopes and observed cross-reactivity

Streptococcus pneumoniae is an encapsulated gram-negative bacterium and a significant human pathogen. The capsular polysaccharide (CPS) is essential for virulence and a target antigen for vaccines. Although widespread introduction of pneumococcal conjugate vaccines (PCVs) has significantly reduced disease, the prevalence of non-vaccine serotypes has increased. On the basis of the CPS, S. pneumoniae serogroup 10 comprises four main serotypes 10A, 10B, 10C, and 10F; as well as the recently identified 10D. As it is the most prevalent, serotype 10A CPS has been included as a vaccine antigen in the next generation PCVs. Here we use molecular modeling to provide conformational rationales for the complex cross-reactivity reported between serotypes 10A, 10B, 10C, and 10F anti-sera. Although the highly mobile phosphodiester linkages produce very flexible CPS, shorter segments are conformationally defined, with exposed β-D-galactofuranose (β DGalf) side chains that are potential antibody binding sites. We identify four distinct conformational epitopes for the immunodominant β DGalf that assist in rationalizing the complex asymmetric cross-reactivity relationships. In particular, we find that strongly cross-reactive serotypes share common epitopes. Further, we show that human intelectin-1 has the potential to bind the exposed exocyclic 1,2-diol of the terminal β DGalf in each serotype; the relative accessibility of three- or six-linked β DGalf may play a role in the strength of the innate immune response and hence serotype disease prevalence. In conclusion, our modeling study and relevant serological studies support the inclusion of serotype 10A in a vaccine to best protect against serogroup 10 disease.

Persistence of Immunity Following 2-Dose Priming with a 10-Valent Pneumococcal Conjugate Vaccine at 6 and 10 Weeks or 6 and 14 Weeks of Age in Nepalese Toddlers

BACKGROUND

The pneumococcal conjugate vaccine has had a substantial impact on invasive pneumococcal disease. Previously, we compared immunity following vaccination with the 10-valent pneumococcal conjugate vaccine (PCV10) administered at 2 slightly different schedules: at 6 and 10 weeks of age, and at 6 and 14 weeks of age, both followed by a 9-month booster. In this study, we followed up those participants to evaluate the medium-term persistence of serotype-specific pneumococcal immunity at 2-3 years of age.

METHOD

Children from the previous studies were contacted and after taking informed consent from their parents, blood samples and nasopharyngeal swabs were collected. Serotype-specific IgG antibody concentrations were determined by enzyme-linked immunosorbent assay, for the 10 vaccine serotypes, at a WHO pneumococcal serology reference laboratory.

FINDINGS

Two hundred twenty of the 287 children who completed the primary study returned at 2-3 years of age to provide a blood sample and nasopharyngeal swab. The nasopharyngeal carriage rate of PCV10 serotypes in the 6 + 14 group was higher than the 6 + 10 group (13.4% vs. 1.9%). Nevertheless, the proportion of toddlers with serum pneumococcal serotype-specific IgG greater than or equal to 0.35 µg/mL was comparable for all PCV10 serotypes between the 6 + 10 week and 6 + 14 week groups. Similarly, the geometric mean concentrations of serum pneumococcal serotype-specific IgG levels were similar in the 2 groups for all serotypes, except for serotype 19F which was 32% lower in the 6 + 10 group than the 6 + 14 group.

CONCLUSION

Immunization with PCV10 at 6 + 10 weeks or 6 + 14 weeks, with a booster at 9 months in each case, results in similar persistence of serotype-specific antibody at 2-3 years of age. Thus, protection from pneumococcal disease is expected to be similar when either schedule is used.

Carriage of Streptococcus pneumoniae in children under five years of age prior to pneumococcal vaccine introduction in Southeast Asia: A systematic review and meta-analysis (2001-2019)

A number of pneumococcal carriage studies in children have been conducted in recent years. However, summary data of carriage prevalence and serotype distribution from South East Asia Region (SEAR) are limited. This may lead to the misconception that Streptococcus pneumoniae vaccine-types are uncommon in the region. Systematic reviews of pneumococcal carriage and the distribution of serotypes are critically important for evidence-based decision-making. We aimed to summarize published data on the serotype prevalence of S. pneumoniae carried in the nasopharynx of children under 5 years of age in SEAR. We performed a systematic review and meta-analysis for relevant studies on S. pneumoniae carriage conducted prior to PCV program implementation from online journal databases published between January 2001 to December 2019. The pooled prevalence of S. pneumoniae in healthy children under 5 years of age in SEAR was 36.0% (95% CI 34.2%-37.8%), and ranged from 68.0% (95% CI: 61.9%-74.0%) in Cambodia to 7.6% (95% CI: 5.7%-9.6%) in Malaysia. Serotypes 6A/B, 23F and 19F were the most common serotypes in children <5 years, accounting for 12.9% (95% CI: 9.4%-16.3%), 9.3% (95% CI: 5.9%-12.8%) and 10.1% (95% CI: 6.6%-13.5%) of isolates, respectively. Vaccine policy makers should take these results into account when making decisions on pneumococcal conjugate vaccine programs implementation. Given the paucity of data, collection of more extensive and updated information of S. pneumoniae serotype epidemiology in children under five years in SEAR is also very important for future studies.

Serotype distribution of invasive, non-invasive and carried Streptococcus pneumoniae in Malaysia: a meta-analysis

Background

Pneumococcal pneumonia is the leading cause of under-five mortality globally. The surveillance of pneumococcal serotypes is therefore vital for informing pneumococcal vaccination policy and programmes. Pneumococcal conjugate vaccines (PCVs) have been available as an option in the private healthcare setting and beginning December 2020, PCV10 was incorporated as part of routine national immunisation programme (NIP) in Malaysia. We searched existing literature on pneumococcal serotype distribution across Malaysia to provide an overall view of this distribution before the implementation of PCV10.

Methods

Online databases (PubMed, Ovid MEDLINE and Scopus), reference lists of articles identified, and grey literature (Malaysian Ministry of Health website, WHO website) were systematically searched for relevant literature on pneumococcal serotype distribution across Malaysia up to 10th November 2020. No lower date limit was set to maximise the number of target reports returned. Results of serotypes were split by age categories, including ≤5 years, > 5 years and unreported for those that did not specify.

Results

The search returned 18 relevant results, with a total of 2040 isolates. The most common serotypes across all disease types were 19F (n = 313, 15.3% [95%CI: 13.8–17.0]), 23F (n = 166, 8.1% [95%CI: 7.0–9.4]), 14 (n = 166, 8.1% [95%CI: 7.0–9.4]), 6B (n = 163, 8.0% [95%CI: 6.9–9.2]) and 19A (n = 138, 6.8% [95%CI: 5.8–7.9]).

Conclusion

Four of the most common serotypes across all isolate sources in Malaysia are covered by PCV10, while PCV13 provides greater serotype coverage in comparison to PCV10. There is still a need for surveillance studies, particularly those investigating serotypes in children under 5 years of age, to monitor vaccine effectiveness and pneumococcal population dynamic following implementation of PCV10 into routine immunisation.

Cost-Effectiveness and Budget Impact Analyses of Pneumococcal Vaccination in Indonesia

As a country with the high number of deaths due to pneumococcal disease, Indonesia has not yet included pneumococcal vaccination into the routine program. This study aimed to analyse the cost-effectiveness and the budget impact of pneumococcal vaccination in Indonesia by developing an age-structured cohort model. In a comparison with no vaccination, the use of two vaccines (PCV10 and PCV13) within two pricing scenarios (UNICEF and government contract price) was taken into account. To estimate the cost-effectiveness value, a 5-year time horizon was applied by extrapolating the outcome of the individual in the modelled cohort until 5 years of age with a 1-month analytical cycle. To estimate the affordability value, a 6-year period (2019-2024) was applied by considering the government's strategic plan on pneumococcal vaccination. In a comparison with no vaccination, the results showed that vaccination would reduce pneumococcal disease by 1,702,548 and 2,268,411 cases when using PCV10 and PCV13, respectively. Vaccination could potentially reduce the highest treatment cost from the payer perspective at $53.6 million and $71.4 million for PCV10 and PCV13, respectively. Applying the UNICEF price, the incremental cost-effectiveness ratio (ICER) from the healthcare perspective would be $218 and $162 per QALY-gained for PCV10 and PCV13, respectively. Applying the government contract price, the ICER would be $987 and $747 per QALY-gained for PCV10 and PCV13, respectively. The result confirmed that PCV13 was more cost-effective than PCV10 with both prices. In particular, introduction cost per child was estimated to be $0.91 and vaccination cost of PCV13 per child (3 doses) was estimated to be $16.61 and $59.54 with UNICEF and government contract prices, respectively. Implementation of nationwide vaccination would require approximately $73.3-$75.0 million (13-14% of routine immunization budget) and $257.4-$263.5 million (45-50% of routine immunization budget) with UNICEF and government contract prices, respectively. Sensitivity analysis showed that vaccine efficacy, mortality rate, and vaccine price were the most influential parameters affecting the ICER. In conclusion, pneumococcal vaccination would be a highly cost-effective intervention to be implemented in Indonesia. Yet, applying PCV13 with UNICEF price would give the best cost-effectiveness and affordability values on the routine immunization budget.

Carriage of upper respiratory tract pathogens in rural communities of Sarawak, Malaysian Borneo

Introduction

Pneumonia is a leading cause of death in Malaysia. Whilst many studies have reported the aetiology of pneumonia in Western countries, the epidemiology of pneumonia in Malaysia remains poorly understood. As carriage is a prerequisite for disease, we sought to improve our understanding of the carriage and antimicrobial resistance (AMR) of respiratory tract pathogens in Malaysia. The rural communities of Sarawak are an understudied part of the Malaysian population and were the focus of this study, allowing us to gain a better understanding of bacterial epidemiology in this population.

Methods

A population-based survey of bacterial carriage was undertaken in participants of all ages from rural communities in Sarawak, Malaysia. Nasopharyngeal, nasal, mouth and oropharyngeal swabs were taken. Bacteria were isolated from each swab and identified by culture-based methods and antimicrobial susceptibility testing conducted by disk diffusion or E test.

Results

140 participants were recruited from five rural communities. Klebsiella pneumoniae was most commonly isolated from participants (30.0%), followed by Staphylococcus aureus (20.7%), Streptococcus pneumoniae (10.7%), Haemophilus influenzae (9.3%), Moraxella catarrhalis (6.4%), Pseudomonas aeruginosa (6.4%) and Neisseria meningitidis (5.0%). Of the 21 S. pneumoniae isolated, 33.3 and 14.3% were serotypes included in the 13 valent PCV (PCV13) and 10 valent PCV (PCV10) respectively. 33.8% of all species were resistant to at least one antibiotic, however all bacterial species except S. pneumoniae were susceptible to at least one type of antibiotic.

Conclusion

To our knowledge, this is the first bacterial carriage study undertaken in East Malaysia. We provide valuable and timely data regarding the epidemiology and AMR of respiratory pathogens commonly associated with pneumonia. Further surveillance in Malaysia is necessary to monitor changes in the carriage prevalence of upper respiratory tract pathogens and the emergence of AMR, particularly as PCV is added to the National Immunisation Programme (NIP).

Supplementary Information

The online version contains supplementary material available at 10.1186/s41479-021-00084-9.

Protective efficacy of mucosal and subcutaneous immunization with DnaJ-ΔA146Ply against influenza and Streptococcus pneumoniae co-infection in mice

Respiratory tract coinfections, specifically involving influenza A virus (IAV) and Streptococcus pneumoniae (S. pneumoniae), remain a major health problem worldwide. Secondary bacterial pneumonia is a common complication and an important cause of mortality related to seasonal and pandemic influenza infections. Vaccination is a basic control strategy against influenza and S. pneumoniae. The fusion protein DnaJ-ΔA146Ply is a vaccine candidate which can induce immune responses against pneumococcal infections via mucosal and subcutaneous immunization in mice. In the present study, we established a co-infection model using mouse-adapted laboratory strains of IAV (PR8) and S. pneumoniae (19F) in mice intranasally and subcutaneously immunized with DnaJ-ΔA146Ply. Our results showed that vaccinated mice suffered decreased weight loss compared with control mice. The survival rates were higher in intranasally and subcutaneously immunized mice than in control mice. In addition, the bacterial loads in nasal washes and lung homogenates were lower in vaccinated mice than in control mice. Furthermore, lung damage was alleviated in vaccinated mice compared with control mice, with less broken alveoli and less proinflammatory cytokine production. Taken together, these results indicate that vaccination with DnaJ-ΔA146Ply shows protective potential against influenza and S. pneumoniae co-infection in mice.

Synthetic Analogs of Streptococcus pneumoniae Capsular Polysaccharides and Immunogenic Activities of Glycoconjugates

Streptococcus pneumoniae is a Gram-positive bacterium (pneumococcus) that causes severe diseases in adults and children. It was established that some capsular polysaccharides of the clinically significant serotypes of S. pneumoniae in the composition of commercial pneumococcal polysaccharide or conjugate vaccines exhibit low immunogenicity. The review considers production methods and structural features of the synthetic oligosaccharides from the problematic pneumococcal serotypes that are characterized with low immunogenicity due to destruction or detrimental modification occurring in the process of their preparation and purification. Bacterial serotypes that cause severe pneumococcal diseases as well as serotypes not included in the composition of the pneumococcal conjugate vaccines are also discussed. It is demonstrated that the synthetic oligosaccharides corresponding to protective glycotopes of the capsular polysaccharides of various pneumococcal serotypes are capable of inducing formation of the protective opsonizing antibodies and immunological memory. Optimal constructs of oligosaccharides from the epidemiologically significant pneumococcal serotypes are presented that can be used for designing synthetic pneumococcal vaccines, as well as test systems for diagnosis of S. pneumoniae infections and monitoring of vaccination efficiency .

The upper respiratory tract microbiome of indigenous Orang Asli in north-eastern Peninsular Malaysia

Much microbiome research has focused on populations that are predominantly of European descent, and from narrow demographics that do not capture the socio-economic and lifestyle differences which impact human health. Here we examined the airway microbiomes of the Orang Asli, the indigenous peoples of Malaysia. A total of 130 participants were recruited from two sites in the north-eastern state of Terengganu in Peninsular Malaysia. Using 16S rRNA sequencing, the nasal microbiome was significantly more diverse in those aged 5-17 years compared to 50+ years (p = 0.023) and clustered by age (PERMANOVA analysis of the Bray-Curtis distance, p = 0.001). Hierarchical clustering of Bray-Curtis dissimilarity scores revealed six microbiome clusters. The largest cluster (n = 28; 35.4%) had a marked abundance of Corynebacterium. In the oral microbiomes Streptococcus, Neisseria and Haemophilus were dominant. Using conventional microbiology, high levels of Staphylococcus aureus carriage were observed, particularly in the 18-65 age group (n = 17/36; 47.2% 95% CI: 30.9-63.5). The highest carriage of pneumococci was in the <5 and 5 to 17 year olds, with 57.1% (4/7) and 49.2% (30/61), respectively. Sixteen pneumococcal serotypes were identified, the most common being the nonvaccine-type 23A (14.6%) and the vaccine-type 6B (9.8%). The prevalence of pneumococcal serotypes covered by pneumococcal conjugate vaccines support introduction into a Malaysian national immunisation schedule. In addition, the dominance of Corynebacterium in the airway microbiomes is intriguing given their role as a potentially protective commensal with respect to acute infection and respiratory health.

Serotypes and Vaccine Coverage of Streptococcus Pneumoniae Colonization in the Nasopharynx of Thai Children in Congested Areas in Chiang Mai

Streptococcus pneumoniae causes around 10% of all deaths in children younger than five years of age. This study aimed to examine the serogroups/serotypes of S. pneumoniae colonization and vaccine serotype coverage of this organism among Thai children. Nasopharyngeal swabs of children less than or equal to 15 years of age were obtained in congested areas in Chiang Mai from 1 February 2013 to 1 August 2013. The serotyping of S. pneumoniae isolates was performed using the ImmuLex™ kit and the vaccine serotype coverage for this organism was evaluated. A total of 292 children were enrolled. One hundred and thirty children (44.5%) had nasopharyngeal colonization with Streptococcus pneumoniae. Eighty-seven (66.9%) isolates were from children younger than five years of age, seventeen (13.1%) were from children aged 6-10 years, and twenty-six (20%) were from children aged 11-15 years. The five most common serogroups/serotypes isolated were 6 (6A, 6B, 6C) (46.1%), 23 (23F, 23A, 23B) (14.6%), 19 (19F, 19A, 19B, 19C) (8.5%), 15 (15F, 15A, 15B, 15C) (6.9%), and 14 (6.1%). Vaccine serotype coverages in pneumococcal conjugate vaccines (PCV):PCV7, PCV10, and PCV13 were 79.1%, 83.6%, and 85.9%, respectively. There were significant increases in coverage between PCV7 and PCV10 (from 79.1% to 83.6%, p < 0.001), PCV7 and PCV13 (from 79.1% to 85.9%, p < 0.001), and PCV10 and PCV13 (from 83.6% to 85.9%, p < 0.001). The majority of pneumococcal serogroup/serotype colonization in the nasopharynx of Thai children in the studied areas was included in the current licensed pneumococcal conjugated vaccines (PCVs). PCV vaccination should be considered for high-risk children to reduce the incidence of invasive pneumococcal disease among Thai children.

Pilus islets and the clonal spread of piliated Streptococcus pneumoniae: A review

Pneumococci are a common cause of severe infections, such as otitis media, pneumonia, meningitis and bacteremia. Pili are detected in a small proportion of pneumococcal population, but these structures have recently been associated with bacterial virulence in humans. Therefore, the epidemiological relationships between pneumococcal pili, serotype and antimicrobial resistance are of interest. This study aims to discuss the virulence contribution of the Streptococcus pneumoniae pili and the epidemiological relationships among the pilus genes, antimicrobial resistance trends, regional serotypes and genotypic variations. Previous reports have characterized the pneumococcal pilus islet as a clonal feature in the pneumococcal serotypes that are covered by the pneumococcal conjugate vaccine (PCV), including serotypes 19A, 19F, 23F and 7F. Many of the pneumococcal molecular epidemiology network (PMEN) clones are piliated isolates that are also strongly associated with a high frequency of multidrug resistance. Most of these piliated pneumococcal isolates belong to a few clonal complexes (CC), such as CC320, CC199, CC271, CC191 and CC156. Additional molecular epidemiology and genomic studies, particularly whole genome sequence analysis (WGS), are needed to develop an in-depth understanding of the piliated pneumococcal isolates.

Disruption of the cpsE and endA Genes Attenuates Streptococcus pneumoniae Virulence: Towards the Development of a Live Attenuated Vaccine Candidate

The majority of deaths due to Streptococcus pneumoniae infections are in developing countries. Although polysaccharide-based pneumococcal vaccines are available, newer types of vaccines are needed to increase vaccine affordability, particularly in developing countries, and to provide broader protection across all pneumococcal serotypes. To attenuate pneumococcal virulence with the aim of engineering candidate live attenuated vaccines (LAVs), we constructed knockouts in S. pneumoniae D39 of one of the capsular biosynthetic genes, cpsE that encodes glycosyltransferase, and the endonuclease gene, endA, that had been implicated in the uptake of DNA from the environment as well as bacterial escape from neutrophil-mediated killing. The cpsE gene knockout significantly lowered peak bacterial density, BALB/c mice nasopharyngeal (NP) colonisation but increased biofilm formation when compared to the wild-type D39 strain as well as the endA gene knockout mutant. All constructed mutant strains were able to induce significantly high serum and mucosal antibody response in BALB/c mice. However, the cpsE-endA double mutant strain, designated SPEC, was able to protect mice from high dose mucosal challenge of the D39 wild-type. Furthermore, SPEC showed 23-fold attenuation of virulence compared to the wild-type. Thus, the cpsE-endA double-mutant strain could be a promising candidate for further development of a LAV for S. pneumoniae.

Molecular detection and genotypic characterisation of Streptococcus pneumoniae isolated from children in Malaysia

Streptococcus pneumoniae (S. pneumoniae) is one of the main causative agents of pneumococcal diseases. To date, more than 90 distinct serotypes have been identified. Implementation of vaccines has caused a drastic reduction in vaccine-serotype pneumococcal diseases but increase in cases due to non-vaccine serotype has been observed in Malaysia. However, further investigation on different serotype incidence in Malaysia is needed and the rate of pneumococcal vaccination for new-born babies in Malaysia remains low. The recent emergence of drug-resistant S. pneumoniae (DRSP) has also been a global concern, especially penicillin resistance. This study determined the serotypes of S. pneumoniae strains (n = 95) isolated from nasopharyngeal specimens from children admitted to UMMC from 2013 to 2015. In accordance with previous studies, PCR result showed 40% of NT isolates were successfully typed as 3 less common serotypes, namely 9N/L, 17A, and 23B. The repetitive-element PCR (REP-PCR) result revealed genetic variations among the strains whereby five major clusters were observed at the similarity of 80% by clustering analysis based on fingerprint data. Penicillin-binding proteins (pbps) of selected isolates were studied by PCR and sequencing. Three strains with ≤19-mm diameter zone for Oxacillin Disc Diffusion (ODD) test previously were recorded to have mutation on all pbp1a, pbp2b, and pbp2x with MIC of 4 µg/ml, which were penicillin-intermediate resistance according to the CLSI breakpoints.

Estimating the population health and economic impacts of introducing a pneumococcal conjugate vaccine in Malaysia- an economic evaluation

Pneumococcal disease is a potentially fatal bacterial infection that is vaccine-preventable. Malaysia has yet to adopt a pneumococcal conjugate vaccine (PCV) into its national immunization program (NIP). In 2016, pneumonia was the 3^rd leading cause of death in children under five in Malaysia, accounting for 3.8% of under-five deaths. Introducing a pneumococcal conjugate vaccine (PCV) is an effective strategy to reduce the disease burden. This study used a decision-analytic model to assess the potential impacts of introducing the available PCVs (13-valent and 10-valent) in Malaysia. Epidemiological and costs inputs were sourced from published literature. For each vaccination program, health outcomes and associated healthcare costs were estimated. The scenarios of initiating PCV13 vs. PCV10 and the status quo (no pneumococcal vaccine) were compared. Serotype trends of Finland and the U.K. were used to model the clinical impacts of PCV10 and PCV13 respectively. The base-case analysis used a societal perspective over a 5-year time horizon. Compared with PCV10, PCV13 was projected to avert an additional 190,628 cases of pneumococcal disease and 1126 cases of death. The acquisition of PCV13 was estimated to cost an incremental US$89,904,777, offset by a cost reduction of -US$250,219,914 on pneumococcal disease-related medical care and lost productivity. PCV13 demonstrated a higher cost-saving potential over PCV10. Compared with no vaccination, PCV13 was estimated as cost-saving. Results were robust across a series of sensitivity analyses. The introduction of PCV13 in a NIP was estimated to reduce a significant burden of disease and to be a cost-saving for the Malaysian health system.

Evaluation of Modified Sequential Multiplex PCR for Streptococcus pneumoniae Serotyping

The aims of this study were to develop modified sequential multiplex PCR (SM-PCR) primer sets and to evaluate their ability and efficiency for serotype determination. We selected target serotypes for SM-PCR testing according to serotype prevalence as reported in Asian publications. The modified SM-PCR consisted of 6 groups of PCR reactions, and each reaction was performed using 5 primer pairs. We evaluated the efficiency and performance of this modified multiplex PCR using 378 pneumococcal strains by comparing the findings with the results of the Quellung reaction. A total of 30 primer pairs were used in a consecutive set of 6 reactions. All results were concordant with those of the Quellung reaction and there was no cross-reactivity to unintended serotypes. We could identify the final serotypes of 370 isolates (97.9%). The coverage rates of modified SM-PCR were 42.6%, 65.9%, and 79.4% in reactions1, 2, and 3, respectively. The modified SM-PCR showed acceptable performance for detecting pneumococcal serotypes and can serve as useful alternative to the Quellung reaction.

Serotypes & penicillin susceptibility of Streptococcus pneumoniae isolated from children admitted to a tertiary teaching hospital in Malaysia

Background & objectives:

Streptococcus pneumoniae (pneumococcus) is a highly invasive extracellular pathogen that causes diseases such as pneumonia, otitis media and meningitis. This study was undertaken to determine the serotype diversity and penicillin susceptibility of S. pneumoniae isolated from paediatric patients in a tertiary teaching hospital in Malaysia.

Methods:

A total of 125 clinical isolates collected from January 2013 to May 2015 were serotyped using seven sequential multiplex polymerase chain reactions. The susceptibility of these isolates to penicillin was also investigated.

Results:

Serotypes detected among the isolates were serotypes 3, 6A/B, 6C, 11/A/D/F, 15A/F, 19A, 19F, 23A, 23F, 34. Serotypes 19F and 6A/B were the most prevalent serotypes detected. Most of the S. pneumoniae were isolated from nasopharyngeal samples of children below five years of age. Majority of the isolates were penicillin susceptible. Only 5.6 per cent of the isolates were non-susceptible to penicillin, mostly of serotype 19F.

Interpretation & conclusions:

Our study revealed the distribution of various serotypes in S. pneumoniae isolates obtained from children in a teaching hospital at Kuala Lumpur, Malaysia and decreasing rates of penicillin resistance among them. The shifts in serotypes and susceptibility to penicillin from time to time have been observed. Continuous monitoring and surveillance are pivotal for better infection control and management of pneumococcal infections among children.

Pneumococcal serotype distribution and antibiotic susceptibility in Malaysia: A four-year study (2014-2017) on invasive paediatric isolates

OBJECTIVE

This study was performed to analyze the serotype distribution of Streptococcus pneumoniae causing invasive pneumococcal disease (IPD) in children aged 5 years and under in Malaysia and to assess the antimicrobial resistance.

METHODS

From 2014 to 2017, a total of 245 invasive S. pneumoniae isolates from children ≤5 years of age were received from hospitals all around Malaysia. All isolates were identified and subjected to serotyping and antimicrobial susceptibility testing.

RESULTS

Of the 245 isolates, 117 (48.0%) were from children aged <1year, 46 (19.05%) were from children aged 1-2 years, and 82 (33.0%) were from children aged 2-5 years. The most common serotypes were 14 (26.9%), 6B (19.6%), 19A (11.8%), 6A (10.6%), and 19F (6.9%) and vaccine coverage was 88.2% for PCV13, 64.1% for PCV10, and 63.3% for PCV7. Resistance to penicillin was 0.2% for non-meningitis cases and 22.2% for meningitis cases; erythromycin resistance was reported in 42.9%, co-trimoxazole in 35.9%, and tetracycline in 42.9%.

CONCLUSIONS

Serotypes 14, 6B, 19A, 6A, and 19F were the most common serotypes isolated from children with IPD in Malaysia during this pre-vaccination era. The lack of reports on the serotype distribution has limited action for the implementation of PCV in the national immunization programme (NIP). The information from this study may benefit future policies for the introduction of PCV in the Malaysian NIP and ultimately may reduce the morbidity and mortality among children in Malaysia.

Pneumococcal vaccine impacts on the population genomics of non-typeable Haemophilus influenzae

The implementation of pneumococcal conjugate vaccines (PCVs) has led to a decline in vaccine-type disease. However, there is evidence that the epidemiology of non-typeable Haemophilus influenzae (NTHi) carriage and disease can be altered as a consequence of PCV introduction. We explored the epidemiological shifts in NTHi carriage using whole genome sequencing over a 5-year period that included PCV13 replacement of PCV7 in the UK’s National Immunization Programme in 2010. Between 2008/09 and 2012/13 (October to March), nasopharyngeal swabs were taken from children <5 years of age. Significantly increased carriage post-PCV13 was observed and lineage-specific associations with Streptococcus pneumoniae were seen before but not after PCV13 introduction. NTHi were characterized into 11 discrete, temporally stable lineages, congruent with current knowledge regarding the clonality of NTHi. The increased carriage could not be linked to the expansion of a particular clone and different co-carriage dynamics were seen before PCV13 implementation when NTHi co-carried with vaccine serotype pneumococci. In summary, PCV13 introduction has been shown to have an indirect effect on NTHi epidemiology and there exists both negative and positive, distinct associations between pneumococci and NTHi. This should be considered when evaluating the impacts of pneumococcal vaccine design and policy.

Retrospective analysis assessing the spatial and temporal distribution of paediatric acute respiratory tract infections in Ho Chi Minh City, Vietnam

BACKGROUND

Acute respiratory tract infections (ARIs) are the leading cause of morbidity and mortality in young children in low/middle-income countries. Using routine hospital data, we aimed to examine the spatial distribution, temporal trends and climatic risk factors of paediatric ARIs in Vietnam.

METHODS

Data from hospitalised paediatric (<16 years) patients with ARIs residing in Ho Chi Minh City (HCMC) between 2005 and 2010 were retrieved from the two main Children's Hospitals and the Hospital for Tropical Diseases in HCMC. Spatial mapping and time series analysis were performed after disaggregating data into upper respiratory tract infections (URIs) and lower respiratory tract infections (LRIs).

RESULTS

Over the study period, there were 155 999 paediatric patients admitted with ARIs (33% of all hospital admissions). There were 68 120 URIs (14%) and 87 879 LRIs (19%). The most common diagnoses were acute pharyngitis (28% of all ARI), pneumonia (21%), bronchitis (18%) and bronchiolitis (16%). A significant increasing trend over time was found for both URIs (mean weekly incidence per 1000 population, I=3.12), incidence rate ratio for 1-week increase in time (RR 1.0, 95% CI 1.02 to 1.17) for URI and (I=4.02, RR 1.08 (95% CI 1.006 to 1.16)) for LRI. The weekly URI incidence peaked in May-June and was significantly associated with lags in weekly URI incidence and the average humidity, rainfall and water level. The weekly LRI incidence exhibited significant seasonality (P<0.0001), with an annual peak in September-October and was significantly associated with lags in weekly LRI incidence and lags in weekly average temperature, rainfall and water level.

CONCLUSIONS

ARIs are a leading cause of childhood hospitalisation in HCMC, Vietnam. The incidence of ARIs was higher in the wet season and in specific HCMC districts. These results may guide health authorities in where and when to effectively allocate resources for the prevention and control of ARIs.

Serotype Distribution of Clinical Streptococcus pneumoniae Isolates before the Introduction of the 13-Valent Pneumococcal Conjugate Vaccine in Cambodia

Childhood vaccination with the 13-valent pneumococcal conjugate vaccine (PCV13) was introduced in Cambodia in January 2015. Baseline data regarding circulating serotypes are scarce. All microbiology laboratories in Cambodia were contacted for identification of stored isolates of Streptococcus pneumoniae from clinical specimens taken before the introduction of PCV13. Available isolates were serotyped using a multiplex polymerase chain reaction method. Among 166 identified isolates available for serotyping from patients with pneumococcal disease, 4% were isolated from upper respiratory samples and 80% were from lower respiratory samples, and 16% were invasive isolates. PCV13 serotypes accounted for 60% (95% confidence interval [CI] 52–67) of all isolates; 56% (95% CI 48–64) of noninvasive and 77% (95% CI 57–89) of invasive isolates. Antibiotic resistance was more common among PCV13 serotypes. This study of clinical S. pneumoniae isolates supports the potential for high reduction in pneumococcal disease burden and may serve as baseline data for future monitoring of S. pneumoniae serotypes circulation after implementation of PCV13 childhood vaccination in Cambodia.

Serotyping of Brunei pneumococcal clinical strains and the investigation of their capability to adhere and invade a brain endothelium model

INTRODUCTION

Pneumococcal infections have caused morbidity and mortality globally. Streptococcus pneumoniae (pneumococci) are commensal bacteria that colonize the nasopharynx, asymptomatically. From there, pneumococci can spread in the lungs causing pneumonia and disseminate in the bloodstream causing bacteremia (sepsis) and reach the brain leading to meningitis. Endothelial cells are one of the most important components of the blood-brain barrier that separates the blood from the brain and plays the first protective role against pneumococcal entry. Thus this study aimed to investigate on the ability of non-meningitis pneumococcal clinical strains to adhere and invade a brain endothelium model.

METHODS

Two pneumococcal Brunei clinical strains were serotyped by multiplex PCR method using oligonucleotide sequences derived from Centers for Disease Control and Prevention. A validated immortalised mouse brain endothelial cell line (bEnd.3) was used as a brain endothelium model for the study of the pneumococcal breach of the blood-brain barrier using an adherence and invasion assay.

RESULTS

Both of the pneumococcal clinical strains were found to be serotype 19F, a common circulating serotype in Southeast Asia and globally and possess the ability to adhere and invade the brain endothelial cells.

CONCLUSION

In addition, this is the first report on the serotype identification of pneumococci in Brunei Darussalam and their application on a brain endothelium model. Further studies are required to understand the virulence capabilities of the clinical strains.

Subcutaneous Immunization with Fusion Protein DnaJ-ΔA146Ply without Additional Adjuvants Induces both Humoral and Cellular Immunity against Pneumococcal Infection Partially Depending on TLR4

Subunit vaccines that are poorly immunogenic are often combined with adjuvants for immunization. Our previous research identified a pneumolysin variant (ΔA146Ply), a Toll-like receptor 4 agonist, that was an effective adjuvant in the protection of fusion protein DnaJ-ΔA146Ply against mucosal Streptococcus pneumoniae infections. For pneumococcal vaccines, World Health Organization recommend injection as a regular vaccination approach. Subcutaneous immunization is a common and effective method of injection, so we explored the immunity mechanism of subcutaneous immunization with DnaJ-ΔA146Ply. We found that mice immunized subcutaneously with fusion proteins ΔA146Ply-DnaJ and DnaJ-ΔA146Ply produced a higher anti-DnaJ IgG titer than when DnaJ alone was administered. DnaJ-ΔA146Ply induced both B-cell and T-cell-dependent protection against both colonization and lethal pneumococcal infections. Levels of IFN-γ, IL-4, and IL-17A were also elevated in DnaJ-ΔA146Ply immunized mice. However, all these effects were negated in TLR4^-/- mice compared to WT mice immunized with DnaJ-ΔA146Ply. B-cell-deficient μMT mice, nude mice, IFN-γ^-/-, and IL-4^-/- mice immunized with DnaJ-ΔA146Ply could not resist infection with pneumococci. IL-17A^-/- and TLR4^-/- mice did not benefit from DnaJ-ΔPly immunization in colonization experiments although their survival was not impaired compared with WT mice. Collectively, our data indicated that ΔA146Ply can be a potential subcutaneous adjuvant, and the DnaJ-ΔA146Ply fusion protein induces both humoral and cellular immune response to resist S. pneumoniae infection. The protective effect of colonization also depends on TLR4.

Neoglycoconjugate of Tetrasaccharide Representing One Repeating Unit of the Streptococcus pneumoniae Type 14 Capsular Polysaccharide Induces the Production of Opsonizing IgG1 Antibodies and Possesses the Highest Protective Activity As Compared to Hexa- and Octasaccharide Conjugates

Identifying protective synthetic oligosaccharide (OS) epitopes of Streptococcus pneumoniae capsular polysaccharides (CPs) is an indispensable step in the development of third-generation carbohydrate pneumococcal vaccines. Synthetic tetra-, hexa-, and octasaccharide structurally related to CP of S. pneumoniae type 14 were coupled to bovine serum albumin (BSA), adjuvanted with aluminum hydroxide, and tested for their immunogenicity in mice upon intraperitoneal prime-boost immunizations. Injections of the conjugates induced production of opsonizing anti-OS IgG1 antibodies (Abs). Immunization with the tetra- and octasaccharide conjugates stimulated the highest titers of the specific Abs. Further, the tetrasaccharide ligand demonstrated the highest ability to bind OS and CP Abs. Murine immune sera developed against tetra- and octasaccharide conjugates promoted pathogen opsonization to a higher degree than antisera against conjugated hexasaccharide. For the first time, the protective activities of these glycoconjugates were demonstrated in mouse model of generalized pneumococcal infections. The tetrasaccharide conjugate possessed the highest protective activities. Conversely, the octasaccharide conjugate had lower protective activities and the lowest one showed the hexasaccharide conjugate. Sera against all of the glycoconjugates passively protected naive mice from pneumococcal infections. Given that the BSA-tetrasaccharide induced the most abundant yield of specific Abs and the best protective activity, this OS may be regarded as the most promising candidate for the development of conjugated vaccines against S. pneumoniae type 14 infections.

Cost-effectiveness analysis of infant universal routine pneumococcal vaccination in Malaysia and Hong Kong

Pneumococcal disease causes large morbidity, mortality and health care utilization and medical and non-medical costs, which can all be reduced by effective infant universal routine immunization programs with pneumococcal conjugate vaccines (PCV). We evaluated the clinical and economic benefits of such programs with either 10- or 13-valent PCVs in Malaysia and Hong Kong by using an age-stratified Markov cohort model with many country-specific inputs. The incremental cost per quality-adjusted life year (QALY) was calculated to compare PCV10 or PCV13 against no vaccination and PCV13 against PCV10 over a 10-year birth cohort's vaccination. Both payer and societal perspectives were used. PCV13 had better public health and economic outcomes than a PCV10 program across all scenarios considered. For example, in the base case scenario in Malaysia, PCV13 would reduce more cases of IPD (+2,296), pneumonia (+705,281), and acute otitis media (+376,967) and save more lives (+6,122) than PCV10. Similarly, in Hong Kong, PCV13 would reduce more cases of IPD cases (+529), pneumonia (+172,185), and acute otitis media (+37,727) and save more lives (+2,688) than PCV10. During the same time horizon, PCV13 would gain over 74,000 and 21,600 additional QALYs than PCV10 in Malaysia and Hong Kong, respectively. PCV13 would be cost saving when compared against similar program with PCV10, under both payer and societal perspective in both countries. PCV13 remained a better choice over PCV10 in multiple sensitivity, scenario, and probabilistic analyses. PCV13s broader serotype coverage in its formulation and herd effect compared against PCV10 were important drivers of differences in outcomes.

Cost-effectiveness and Health Benefits of Pediatric 23-valent Pneumococcal Polysaccharide Vaccine, 7-valent Pneumococcal Conjugate Vaccine and Forecasting 13-valent Pneumococcal Conjugate Vaccine in China

BACKGROUND

Each year in China, approximately 700,000 children under 5 years old are diagnosed with pneumonia, and 30,000 die of the disease. Although 7-valent pneumococcal conjugate vaccine (PCV-7) and 23-valent pneumococcal polysaccharide vaccine (PPV-23) are available in China, the costs are borne by the consumer, resulting in low coverage for PCV-7. We aimed to conduct a simulation study to assess the cost-effectiveness and health benefits of PCV-7, 13-valent pneumococcal conjugate vaccine (PCV-13) and PPV-23 to prevent childhood pneumonia and other vaccine-preventive diseases in China.

METHODS

An economic evaluation was performed using a Markov simulation model. Parameters including demographic, epidemiological data, costs and efficacy of vaccines were obtained from previous studies. A hypothetical cohort of 100,000 newborns (focusing on pneumococcal diseases ≤7 years old) was followed up until death or 100 years of age. The model incorporated the impact of vaccination on reduction of incidence of pneumococcal diseases and mortality of children ≤7 years. Outcomes are presented in terms of disease cases averted, quality-adjusted life years (QALYs) and incremental cost-effectiveness ratio.

RESULTS

Under baseline assumptions, PPV-23 is currently the only cost-effective option, whereas PCV-13 showed the greatest impact on pneumococcal disease burden, reducing invasive pneumococcal diseases by 31.3%, pneumonia by 15.3% and gaining 73.8 QALYs (10,000 individuals at discount rate of 3%). Incremental cost-effectiveness ratios of PCV-13 and PCV-7 are US$29,460/QALY and US$104,094/QALY, respectively, showing no cost-effectiveness based on the World Health Organization recommended willingness-to-pay threshold. On the other hand, the incremental cost-effectiveness ratios of PCVs were most sensitive to vaccination costs; if it reduces 4.7% and 32.2% for PCV-7 and PCV-13, respectively, the vaccination will be cost-effective.

CONCLUSIONS

To scale up current vaccination strategies and achieve potential health benefits, the replacement of PCV-7 with PCV-13 should be considered. As well, PCV's costs need to be reduced by increasing public subsidies and providing financial support to poor families.

Characterisation of Invasive Streptococcus pneumoniae Isolated from Cambodian Children between 2007 - 2012

BACKGROUND

The 13-valent pneumococcal vaccine (PCV13) was introduced in Cambodia in January 2015. There are limited data concerning the common serotypes causing invasive pneumococcal disease (IPD). Knowledge of the circulating pneumococcal serotypes is important to monitor epidemiological changes before and after vaccine implementation.

METHODS

All episodes of IPD defined by the isolation of Streptococcus pneumoniae from blood, cerebrospinal fluid or other sterile site in Cambodian children admitted to the Angkor Hospital for Children in Siem Reap, Northwestern Cambodia, between 1st January 2007 and 1st July 2012 were retrospectively studied. Streptococcus pneumoniae isolates that could be retrieved underwent phenotypic typing and whole genome sequencing.

RESULTS

There were 90 Cambodian children hospitalized with IPD with a median (IQR) age of 2.3 years (0.9-6.2). The case fatality was 15.6% (95% CI 8-23). Of 50 Streptococcus pneumoniae isolates available for further testing, 46% were penicillin non-susceptible and 8% were ceftriaxone non-susceptible, 78% were cotrimoxazole resistant, 30% were erythromycin resistant and 30% chloramphenicol resistant. There were no significant changes in resistance levels over the five-year period. The most common serotypes were 1 (11/50; 22%), 23F (8/50; 16%), 14 (6/50; 12%), 5 (5/50; 10%) and 19A (3/50; 6%). Coverage by PCV7, PCV10 and PCV13 was 44%, 76% and 92% respectively. We identified novel multilocus sequence types and resistotypes using whole genome sequencing.

CONCLUSIONS

This study suggests IPD is an important disease in Cambodian children and can have a significant mortality. PCV13 coverage of the serotypes determined in studied strains was high and consistent with another recent study. The phenotypic resistance patterns observed were similar to other regional studies. The use of whole genome sequencing in the present study provides additional typing and resistance information together with the description of novel sequence types and resistotypes.

The Effect of a BSA Conjugate of a Synthetic Hexasaccharide Related to the Fragment of Capsular Polysaccharide of Streptococcus pneumoniae Type 14 on the Activation of Innate and Adaptive Immune Responses

We report the effect of a bovine serum albumin (BSA) conjugate of a synthetic hexasaccharide (HS) related to the fragment of the capsular polysaccharide (PS) of Streptococcus pneumoniae type 14 on the stimulation of innate immune system and the subsequent development of a PS-specific antibody response. Glycoconjugate (GC) in the presence (GC + AL) or absence of aluminum hydroxide was administered to mice twice. GC increased the number of TLR2-expressing cells and induced the maturation of dendritic cells (CD11c(+), CD80(+) and, MHCII(+)), which secreted IL-1β, IL-6, and TNFα into the culture medium. The level of IL-1β, IL-10, IFNγ, and TNFα in the blood increased within 24 h after the single GC administration to mice. On day 7, the numbers of splenic CD4(+) and CD8(+) T lymphocytes and B lymphocytes increased. After the second immunization, the levels of CD4(+) and CD8(+) T lymphocytes were lower than in the control, whereas the B cell, NK cell, and MHC class II-expressing cell numbers remained enhanced. However, of the presence of anti-PS, IgG antibodies were not detected. The addition of aluminum hydroxide to GC stimulated the production of GM-CSF, IL-1β, IL-5, IL-6, IL-10, IL-17, IFNγ, and TNFα. Anti-PS IgG1 antibody titers 7 days after the second immunization were high. During that period, normal levels of splenic CD4(+) T lymphocytes were maintained, whereas reduced CD8(+) T lymphocyte numbers and increased levels of B lymphocytes, NK cells, and MHC class II-expressing cell numbers were observed. Anti-PS IgG levels diminished until day 92. A booster immunization with GC + AL stimulated the production of anti-PS IgG memory antibodies, which were determined within 97 days. The elucidation of specific features of the effect of the synthetic HS conjugate on the stimulation of innate, cell-mediated immunity, and antibody response can favor the optimization of GC vaccine design.

Serotypes and genotypes of Streptococcus pneumoniae isolates from Trinidad and Tobago

OBJECTIVES

There are currently 94 known pneumococcal capsular polysaccharide serotypes and their prevalence differs by geographic region and the period studied. Streptococcus pneumoniae infections have been diagnosed clinically in Trinidad and Tobago and other Caribbean countries, however data on the serotype and sequence type distributions in this country are limited. The objective of this study was to determine serotypes and multilocus sequence types (MLSTs) of invasive and non-invasive pneumococcal isolates from Trinidad and Tobago.

METHODS

Ninety-eight pneumococcal isolates from several regional hospitals in the country were analyzed using both standard microbiological methods and molecular analysis. These isolates included invasive (n=83) and selected non-invasive (n=15) strains recovered before (n=25) and after (n=73) the introduction of the pneumococcal conjugate vaccine.

RESULTS

More than half of the isolates (54.1%) were recovered from children under 15 years of age, with the largest proportion being from children under 2 years of age (24.5%). The most prevalent serotypes were 19F (18.4%), 6B (15.3%), 23F (14.3%), 3 (11.2%), 19A (6.1%), 6A (5.1%), 14 (5.1%), and 9V (4.1%). The most common serotype/MLST combinations were 6B/ST138 (n=10, 10.2%), 3/ST180 (n=5, 5.1%), 23F/ST629 (n=5, 5.1%), 19F/ST8398 (n=4, 4.1%), and three each of 6B/ST145, 14/9V/ST156, 9V/ST162, 19A/320, and 3/ST10440.

CONCLUSIONS

This report provides the first glimpse of the prevailing pneumococcal sequence types in the country. Most of the isolates represented serotypes in the 10-valent (61.2% of isolates) and 13-valent (83.7%) pneumococcal conjugate vaccines. A detailed population study is warranted to fully determine the circulating pneumococcal sequence types. Furthermore, the implementation of an effective and continuous surveillance system in Trinidad and Tobago is paramount to monitor vaccine impact.

Serotype Distribution and Antimicrobial Susceptibilities of Invasive Streptococcus pneumoniae Isolates from Adults in Korea from 1997 to 2012

In Republic of Korea, a 7-valent pneumococcal conjugated vaccine (PCV7) was licensed for use in infants in 2003, and 13-valent PCV (PCV13) replaced it since 2010. We investigated trends in serotype distribution and antibiotic susceptibility of pneumococcal isolates from adult patients with invasive pneumococcal diseases (IPD). Invasive pneumococcal isolates from adult patients of ≥ 16 years of age were collected from 1997 to 2012. Serotypes of the isolates were determined by the Quellung reaction. Distribution of serotypes was analyzed according to the vaccine types. Antibiotic susceptibility was tested by using E-test strips. A total of 272 invasive pneumococcal isolates were included. The most common serotypes were serotype 19F (8.5%, 23/272), and serotype 3 (8.1%, 22/272), and 24.6% (67/272) of the isolates were of non-vaccine serotypes. Of the 272 isolates, 2.6% (7/272) were penicillin MICs of ≥ 4 µg/mL. The proportion of the PCV13 serotypes decreased from 63.3% (50/79) in 1997-2003 to 48.6% (17/35) in 2011-2012, whereas that of non-vaccine serotypes was 26.6% (21/79) and 25.7% (9/35), respectively, for the same periods. The proportion of the PCV13 serotypes showed a decreasing trend among adult patients with IPD over the study period.

Nonencapsulated Streptococcus pneumoniae: Emergence and Pathogenesis

While significant protection from pneumococcal disease has been achieved by the use of polysaccharide and polysaccharide-protein conjugate vaccines, capsule-independent protection has been limited by serotype replacement along with disease caused by nonencapsulated Streptococcus pneumoniae (NESp). NESp strains compose approximately 3% to 19% of asymptomatic carriage isolates and harbor multiple antibiotic resistance genes. Surface proteins unique to NESp enhance colonization and virulence despite the lack of a capsule even though the capsule has been thought to be required for pneumococcal pathogenesis. Genes for pneumococcal surface proteins replace the capsular polysaccharide (cps) locus in some NESp isolates, and these proteins aid in pneumococcal colonization and otitis media (OM). NESp strains have been isolated from patients with invasive and noninvasive pneumococcal disease, but noninvasive diseases, specifically, conjunctivitis (85%) and OM (8%), are of higher prevalence. Conjunctival strains are commonly of the so-called classical NESp lineages defined by multilocus sequence types (STs) ST344 and ST448, while sporadic NESp lineages such as ST1106 are more commonly isolated from patients with other diseases. Interestingly, sporadic lineages have significantly higher rates of recombination than classical lineages. Higher rates of recombination can lead to increased acquisition of antibiotic resistance and virulence factors, increasing the risk of disease and hindering treatment. NESp strains are a significant proportion of the pneumococcal population, can cause disease, and may be increasing in prevalence in the population due to effects on the pneumococcal niche caused by pneumococcal vaccines. Current vaccines are ineffective against NESp, and further research is necessary to develop vaccines effective against both encapsulated and nonencapsulated pneumococci.

Vaccine preventable meningitis in Malaysia: epidemiology and management

Worldwide bacterial meningitis accounts for more than one million cases and 135,000 deaths annually. Profound, lasting neurological complications occur in 9-25% of cases. This review confirms the greatest risk from bacterial meningitis is in early life in Malaysia. Much of the disease burden can be avoided by immunization, particularly against Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae. Despite inclusion of the Hib vaccine in the National Immunisation Programme and the licensure of pneumococcal vaccines, these two species are the main contributors to bacterial meningitis in Malaysia, with Neisseria meningitidis and Mycobacterium tuberculosis, causing a smaller proportion of disease. The high Hib prevalence may partly be due to dated, small-scale studies limiting the understanding of the current epidemiological situation. This highlights the need for larger, better quality surveillance from Malaysia to evaluate the success of Hib immunization and to help guide immunization policy for vaccines against S. pneumoniae and N. meningitidis.

Streptococcus pneumoniae as cause of infection in infants less than 60 days of age: serotypes and antimicrobial susceptibility

OBJECTIVE

The aim of this study was to determine the distribution of serotypes and the antimicrobial susceptibilities of Streptococcus pneumoniae clinical isolates causing invasive and non-invasive disease in children aged ≤60 days in hospitals in Mexico.

METHODS

A 15-year retrospective study was conducted for the period 2000 to 2014. Pneumococcal clinical isolates were serotyped by Quellung reaction, and antimicrobial susceptibility testing was performed with the broth microdilution method.

RESULTS

A total of 126 pneumococcal isolates were collected. Pneumonia was the most frequent diagnosis (40.5%), followed by meningitis (29.4%), septicemia (16.7%), and other clinical entities, including otitis media and conjunctivitis (13.5%). The most frequent serotypes before the introduction of heptavalent pneumococcal conjugate vaccine (PCV7) were 19F, 23F, 7F, and 35B. Serotypes 3, 6A, 10A, 12F, and 15A/B increased after the introduction of PCV7. Serotype 19A was isolated most frequently in the pneumonia and meningitis cases only after the introduction of PCV7, and it displayed a high resistance to penicillin.

CONCLUSIONS

Although the number of infections in infants aged ≤60 days was low, such infections were not unusual events. New vaccination strategies should be evaluated to limit the risks in this age group.

Serotype distribution and antibiotic resistance of Streptococcus pneumoniae isolates collected at a Chinese hospital from 2011 to 2013

BACKGROUND

Streptococcus pneumoniae infections are a major cause of global morbidity and mortality, and the emergence of antibiotic-resistant Streptococcus pneumoniae strains has been increasingly reported. This study provides up-to-date information on bacterial serotype distribution and drug resistance from S. pneumoniae clinical isolates that could guide prevention and treatment strategies for pneumococcal disease in China.

METHODS

A total of 94 S. pneumoniae isolates were collected from outpatients and inpatients at one Chinese hospital from 2011-2013. Drug susceptibility and resistance was determined by minimum inhibitory concentrations (MICs). Capsular serotypes were identified by the quellung reaction test and multiplex polymerase chain reaction.

RESULTS

Fifteen serotypes were identified among the 94 S. pneumoniae clinical isolates that were collected. Prevalent serotypes were 19F (42.6 %), 19A (8.5 %), 3 (8.5 %), and 6B (7.4 %). Potential immunization coverage rates for the 7-, 10- and 13-valent pneumococcal polysaccharide conjugate vaccines were 59.6, 62.6, and 79.6 %, respectively. Resistance rates to tetracycline, erythromycin, and trimethoprim/sulfamethoxazole were 91.2, 80.2 and 63.8 %, respectively. Resistance rates to penicillin, amoxicillin, ceftriaxone, and cefotaxime were 47.3, 34.1, 19.8, and 18.7 %, respectively. In almost all cases, antimicrobial resistance of the S. pneumoniae isolates in patients five years or younger was higher than isolates collected from patients aged 51 years or older.

CONCLUSION

Prevalent serotypes among the 94 S. pneumoniae clinical isolates were 19F, 19A, 3, and 6B. The 13-valent pneumococcal polysaccharide conjugate vaccine covered the majority of the serotypes identified in this sample. Drug resistance varied among different serotypes and age groups. Clinical precautions should be taken to avoid the development of multidrug resistance in this potential human pathogen.

Dynamics of serotype 14 Streptococcus pneumoniae population causing acute respiratory infections among children in China (1997-2012)

Background

In the last decade, the Streptococcus pneumoniae population has changed, mainly due to the abuse of antibiotics. The aim of this study was to determine the genetic structure of 144 S. pneumonia serotype 14 isolates collected from children with acute respiratory infections during 1997–2012 in China.

Methods

All isolated pneumococci were tested for their sensitivity to 11 kinds of antibiotics with the E-test method or disc diffusion. The macrolides resistance genes ermB and mefA, as well as the sulfamethoxazole-trimethoprim resistance gene dihydrofolate reductase (DHFR) were detected by polymerase chain reaction (PCR). The sequence types (STs) were analyzed with multilocus sequence typing (MLST).

Results

From 1997 to 2012, the percentage of serotype 14 S. pneumonia isolates in the whole isolates increased. All of the 144 serotype 14 S. pneumonia isolates were susceptible to amoxicillin-clavulanic acid, vancomycin and levofloxacin. No penicillin resistant isolate was found, and the intermediate rate was as low as 0.7 %. Erythromycin resistance was confirmed among 143 isolates. The ermB gene was determined in all erythromycin resistant isolates, and the mefA gene was positive additionally in 13 of them. The non-susceptibility rate to the tested cephalosporins increased from 1997–2012. All trimethoprim-resistant isolates contained the Ile100-Leu mutation. Overall, 30 STs were identified, among which ST876 was the most prevalent, followed by ST875. During the study period, the percentage of CC876 increased from 0 % in 1997–2000 to 96.4 % in 2010–2012, whereas CC875 decreased from 84.2 to 0 %. CC876 showed higher non-susceptibility rates to β-lactam antibiotics than CC875.

Conclusion

The percentage of serotype 14 S. pneumonia isolates increased over time in China. The increase of resistance to β-lactam antibiotics in this serotype isolates was associated with the spread of CC876.

Changing trends in serotype distribution and antimicrobial susceptibility of Streptococcus pneumoniae causing invasive diseases in Central Thailand, 2009-2012

To describe the trends in serotype distribution and antimicrobial susceptibility of S. pneumoniae causing invasive pneumococcal diseases (IPD) we tested 238 pneumococci isolates from normally sterile sites between 2009 and 2012 and compared these findings with previous data collected within our network. Serotyping was performed for 15 serotypes contained in the 7-,10-, 13-, and experimental 15-valent pneumococcal conjugate vaccines (PCV). The most common serotypes found were 6B (13.9%), 19A (12.6%), 14 (8.0%), 18C (5.9%), and 6A (3.8%); and 39.9% were non-PCV15 serotypes. One of 81 patients with available data had breakthrough infection with vaccine serotype (19F). There was a significant increase of serotype 19A among children ≤5 years (5.6% in 2000-2009 vs 18.3% in 2009-2012, P = 0.003). The all-age serotype coverage was 36.4%, 41.5%, 59.3%, and 59.7% for PCV7, PCV10, PCV13, and PCV 15, respectively. The corresponding coverage in children ≤5 years were 46.4%, 48.8%, 73.2%, and 73.2% respectively. High susceptibilities to penicillin (89.7%), cefotaxime (95.7%), cefditoren (90.2% by Spanish breakpoints), ofloxacin (97.9%), and levofloxacin (100%), but low to cefdinir (50.0%), cefditoren (45.1% by US-FDA breakpoints), macrolides (<50%), clindamycin (67.7%), tetracycline (41.4%), and trimethoprim-sulfamethoxazole (32.4%) were observed. Serotype 19A was less susceptible to penicillin (80.0 vs 91.2%, P = 0.046), cefditoren (66.7 vs 95.5% by Spanish breakpoints, P = 0.004), and tetracycline (9.1 vs 45.5%, P = 0.024) than non-19A isolates. These data emphasize the need for continued surveillance to monitor changes in serotypes as well as antimicrobial susceptibilities in order to guide strategies for prevention and treatment.

Antimicrobial Activity of Novel Synthetic Peptides Derived from Indolicidin and Ranalexin against Streptococcus pneumoniae

Antimicrobial peptides (AMPs) represent promising alternatives to conventional antibiotics in order to defeat multidrug-resistant bacteria such as Streptococcus pneumoniae. In this study, thirteen antimicrobial peptides were designed based on two natural peptides indolicidin and ranalexin. Our results revealed that four hybrid peptides RN7-IN10, RN7-IN9, RN7-IN8, and RN7-IN6 possess potent antibacterial activity against 30 pneumococcal clinical isolates (MIC 7.81-15.62µg/ml). These four hybrid peptides also showed broad spectrum antibacterial activity (7.81µg/ml) against S. aureus, methicillin resistant S. aureus (MRSA), and E. coli. Furthermore, the time killing assay results showed that the hybrid peptides were able to eliminate S. pneumoniae within less than one hour which is faster than the standard drugs erythromycin and ceftriaxone. The cytotoxic effects of peptides were tested against human erythrocytes, WRL-68 normal liver cell line, and NL-20 normal lung cell line. The results revealed that none of the thirteen peptides have cytotoxic or hemolytic effects at their MIC values. The in silico molecular docking study was carried out to investigate the binding properties of peptides with three pneumococcal virulent targets by Autodock Vina. RN7IN6 showed a strong affinity to target proteins; autolysin, pneumolysin, and pneumococcal surface protein A (PspA) based on rigid docking studies. Our results suggest that the hybrid peptides could be suitable candidates for antibacterial drug development.

Choosing between 7-, 10- and 13-valent pneumococcal conjugate vaccines in childhood: a review of economic evaluations (2006-2014)

BACKGROUND

Seven-valent pneumococcal conjugate vaccines (PCV7) have been used in children for more than a decade. Given the observed increase in disease caused by pneumococcal serotypes not covered by PCV7, an increasing number of countries are switching from 7-valent to 10- and 13-valent PCVs ("PCV10" and "PCV13"). Economic evaluations are important tools to inform decisions and price negotiations to make such a switch.

OBJECTIVE

This review aims to provide a critical assessment of economic evaluations involving PCV10 or PCV13, published since 2006.

METHODS

We searched Scopus, ISI Web of Science (SCI and SSCI) and Pubmed to retrieve, select and review relevant studies, which were archived between 1st January 2006 and 31st January 2014. The review protocol involved standard extraction of assumptions, methods, results and sponsorships from the original studies.

RESULTS

Sixty-three economic evaluations on PCVs published since January 2006 were identified. About half of these evaluated PCV10 and/or PCV13, the subject of this review. At current prices, both PCV13 and PCV10 were likely judged preferable to PCV7. However, the combined uncertainty related to price differences, burden of disease, vaccine effectiveness, herd and serotype replacement effects determine the preference base for either PCV10 or PCV13. The pivotal assumptions and results of these analyses also depended on which manufacturer sponsored the study.

CONCLUSION

A more thorough exploration of uncertainty should be made in future analyses on this subject, as we lack understanding to adequately model herd and serotype replacement effects to reliably predict the population impact of PCVs. The introduction of further improved PCVs in an environment of evolving antibiotic resistance and under the continuing influence of previous PCVs implies that the complexity and data requirements for relevant analyses will further increase. Decision makers using these analyses should not just rely on an analysis from a single manufacturer.

A randomised trial to evaluate the immunogenicity, reactogenicity, and safety of the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) co-administered with routine childhood vaccines in Singapore and Malaysia

Background

The immunogenicity, reactogenicity, and safety of the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) co-administered with routine childhood vaccines were evaluated among infants from Singapore and Malaysia, where PHiD-CV has been licensed.

Methods

In the primary vaccination phase, 298 infants from Singapore and 168 infants from Malaysia were randomised to receive the Phase III Clinical (Clin) or the Commercial (Com) lot of PHiD-CV at 2, 3, and 5 months of age. In the booster vaccination phase, 238 toddlers from Singapore received one dose of the PHiD-CV Commercial lot at 18–21 months of age. Immune responses to pneumococcal polysaccharides were measured using 22F-inhibition enzyme-linked immunosorbent assay (ELISA) and functional opsonophagocytic activity (OPA) assay and to protein D, using ELISA.

Results

Immune responses induced by primary vaccination with the PHiD-CV Commercial lot were non-inferior to the Phase III Clinical lot in terms of adjusted antibody geometric mean concentration (GMC) ratios for each vaccine pneumococcal serotype and protein D. For each vaccine pneumococcal serotype, ≥93.6% and ≥88.5% of infants from Malaysia and Singapore had post-primary vaccination antibody concentrations ≥0.2 μg/mL and OPA titres ≥8, in the Clin and Com groups, respectively. For each vaccine pneumococcal serotype, ≥60.8% and ≥98.2% of toddlers from Singapore had pre- and post-booster antibody concentrations ≥0.2 μg/mL, in the Clin and Com groups, respectively. All children, except one, had measurable anti-protein D antibodies and the primary and booster doses of the co-administered vaccines were immunogenic. The incidence of each grade 3 solicited symptom was ≤11.1% in both study phases. No serious adverse events considered causally related to vaccination were reported throughout the study.

Conclusions

PHiD-CV given as three-dose primary vaccination to infants in Singapore and Malaysia and booster vaccination to toddlers in Singapore was shown to be immunogenic with a clinically acceptable-safety profile.

This study has been registered at http://www.clinicaltrials.govNCT00808444 and NCT01119625.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2334-14-530) contains supplementary material, which is available to authorized users.

Novel clones of Streptococcus pneumoniae causing invasive disease in Malaysia

Although Streptococcus pneumoniae is a leading cause of childhood disease in South East Asia, little has previously been reported regarding the epidemiology of invasive pneumococcal disease in Malaysia and very few studies have explored pneumococcal epidemiology using multilocus sequence typing (MLST). Here we describe serotype, multilocus sequence type (ST), and penicillin susceptibility of thirty pneumococcal invasive disease isolates received by the University of Malaya Medical Centre between February 2000 and January 2007 and relate this to the serotypes included in current pneumococcal conjugate vaccines. A high level of diversity was observed; fourteen serotypes and 26 sequence types (ST), (11 of which were not previously described) were detected from 30 isolates. Penicillin non-susceptible pneumococci accounted for 33% of isolates. The extent of molecular heterogeneity within carried and disease-causing Malaysian pneumococci remains unknown. Larger surveillance and epidemiological studies are now required in this region to provide robust evidence on which to base future vaccine policy.