Serotype replacement in disease after pneumococcal vaccination

Designing ecologically optimized pneumococcal vaccines using population genomics

Streptococcus pneumoniae (the pneumococcus) is a common nasopharyngeal commensal that can cause invasive pneumococcal disease (IPD). Each component of current protein-polysaccharide conjugate vaccines (PCVs) generally induces immunity specific to one of the approximately 100 pneumococcal serotypes, and typically eliminates it from carriage and IPD through herd immunity. Overall carriage rates remain stable owing to replacement by non-PCV serotypes. Consequently, the net change in IPD incidence is determined by the relative invasiveness of the pre- and post-PCV-carried pneumococcal populations. In the present study, we identified PCVs expected to minimize the post-vaccine IPD burden by applying Bayesian optimization to an ecological model of serotype replacement that integrated epidemiological and genomic data. We compared optimal formulations for reducing infant-only or population-wide IPD, and identified potential benefits to including non-conserved pneumococcal carrier proteins. Vaccines were also devised to minimize IPD resistant to antibiotic treatment, despite the ecological model assuming that resistance levels in the carried population would be preserved. We found that expanding infant-administered PCV valency is likely to result in diminishing returns, and that complementary pairs of infant- and adult-administered vaccines could be a superior strategy. PCV performance was highly dependent on the circulating pneumococcal population, further highlighting the advantages of a diversity of anti-pneumococcal vaccination strategies.

Co-carriage of Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis among three different age categories of children in Hungary

Background

The nasopharynx can from time to time accommodate otherwise pathogenic bacteria. This phenomenon is called asymptomatic carriage. However, in case of decreased immunity, viral infection or any other enhancing factors, severe disease can develop. Our aim in this study was to survey the nasal carriage rates of four important respiratory pathogens in three different age groups of children attending nurseries, day-care centres and primary schools. This is the first study from Hungary about the asymptomatic carriage of H. influenzae and M. catarrhalis.

Methods

Altogether 580 asymptomatic children were screened in three Hungarian cities. Samples were collected from both nostrils with cotton swabs. The identification was based on both colony morphology and species-specific PCRs. Serotyping was performed for S. pneumoniae, H. influenzae and M. catarrhalis. Antibiotic susceptibility was determined with agar dilution, according to the EUCAST guidelines. Clonality was examined by PFGE.

Results and conclusions

Whereas the carriage rates of S. pneumoniae, H. influenzae and M. catarrhalis clearly decreased with age, that of S. aureus showed an opposite tendency. Multiple carriage was least prevalent if S. aureus was one of the participants. The negative association between this bacterium and the others was statistically significant. For pneumococcus, the overall carriage rate was lower compared to earlier years, and PCV13 serotypes were present in only 6.2% of the children. The majority of H. influenzae isolates was non-typeable and no type b was detected; serotype A was dominant among M. catarrhalis. All four bacteria were more sensitive to antibiotics compared to clinical isolates. No MRSAs were detected, but we found three mupirocin resistant strains. The positive effect of Hib- and PCV-vaccination is undoubted. Continued surveillance of these pathogens is required.

Serotype and clonal distribution dynamics of invasive pneumococcal strains after PCV13 introduction (2011-2016): Surveillance data from 23 sites in Catalonia, Spain

Background

The objective of this study is to describe incidence and shifts of serotype and clonal distribution of invasive Streptococcus pneumoniae strains in four different age groups (<5 years, 5–17 years, 18–64 years and >65 years) during a period of intermediate PCV13 vaccination coverage (2011–2016) in Catalonia, Spain.

Methods

We included all pneumococcal strains systematically sent to the Catalan support laboratory for molecular surveillance of invasive pneumococcal disease (IPD) located at Hospital Sant Joan de Deu, Barcelona. Two study periods were considered: 2011–13, early PCV13 vaccination period (EVP) and 2014–2016, late vaccination period (LVP).

Results

A total of 2142 strains were included in the study. Five years after intermediate introduction of PCV13 in our population, a significant decrease of overall incidence of IPD in children <5 years was observed (incidence rate ratio 0.5, 95% confidence interval 0.4–0.8). However, in seniors older than 65 years, a significant increase of overall incidence of IPD was observed (IRR 1.4, 95% CI 1.1–1.7). The contribution of PCV13 vaccine serotypes to IPD declined significantly in all age groups: from 59% to 38.1% in <5 years; 82.7% to 59% in 5–17 years, 47.8% to 34.1% in 18–64 years and 48.2% to 37% in >65 years. Results found when comparing both periods were consistent with IRRs observed year by year. In children <5 years, the three major serotypes detected were 1, 24F and 19A in EVP vs 24F, 14 and 10A in LVP. Among patients 5–17 years the first three serotypes were 1, 12F and 14 both in EVP and LVP. Among adults 18–64, the three major serotypes detected were 1, 12F and 8 vs 8, 12F and 3, respectively. Finally, in patients >65 years the most frequently isolated serotypes were 3, 19A and 7F vs 3, 14 and 12F, respectively. Regarding clonal complexes (CCs) expressing mainly PCV13 serotypes, significant decreases of the proportions of CC306, CC191 and CC320 were observed, while CC156 showed a significant increase. As for CCs expressing mostly non-PCV13 serotypes, significant increases in ST989, CC53 and CC404 were showed.

Conclusions

Despite low vaccine coverage in our setting a significant decrease of incidence of IPD was observed in children younger than 5 years. The modest indirect protection against vaccine serotypes causing IPD in elderly indicate the need for the inclusion of more serotypes in future high-valent PCV and vaccinating old adults should be considered.

Will HPV vaccination prevent cervical cancer?

We conducted a critical appraisal of published Phase 2 and 3 efficacy trials in relation to the prevention of cervical cancer in women. Our analysis shows the trials themselves generated significant uncertainties undermining claims of efficacy in these data. There were 12 randomised control trials (RCTs) of Cervarix and Gardasil. The trial populations did not reflect vaccination target groups due to differences in age and restrictive trial inclusion criteria. The use of composite and distant surrogate outcomes makes it impossible to determine effects on clinically significant outcomes. It is still uncertain whether human papillomavirus (HPV) vaccination prevents cervical cancer as trials were not designed to detect this outcome, which takes decades to develop. Although there is evidence that vaccination prevents cervical intraepithelial neoplasia grade 1 (CIN1) this is not a clinically important outcome (no treatment is given). Trials used composite surrogate outcomes which included CIN1. High efficacy against CIN1+ (CIN1, 2, 3 and adenocarcinoma in situ (AIS)) does not necessarily mean high efficacy against CIN3+ (CIN3 and AIS), which occurs much less frequently. There are too few data to clearly conclude that HPV vaccine prevents CIN3+. CIN in general is likely to have been overdiagnosed in the trials because cervical cytology was conducted at intervals of 6-12 months rather than at the normal screening interval of 36 months. This means that the trials may have overestimated the efficacy of the vaccine as some of the lesions would have regressed spontaneously. Many trials diagnosed persistent infection on the basis of frequent testing at short intervals, i.e. less than six months. There is uncertainty as to whether detected infections would clear or persist and lead to cervical changes.

Human Papillomavirus Genotype Replacement: Still Too Early to Tell?

Background

Although human papillomavirus (HPV) vaccines are highly efficacious in protecting against HPV infections and related diseases, vaccination may trigger replacement by nontargeted genotypes if these compete with the vaccine-targeted types. HPV genotype replacement has been deemed unlikely, based on the lack of systematic increases in the prevalence of nonvaccine-type (NVT) infection in the first decade after vaccination, and on the presence of cross-protection for some NVTs.

Methods

To investigate whether type replacement can be inferred from early postvaccination surveillance, we constructed a transmission model in which a vaccine type and an NVT compete through infection-induced cross-immunity. We simulated scenarios of different levels of cross-immunity and vaccine-induced cross-protection to the NVT. We validated whether commonly used measures correctly indicate type replacement in the long run.

Results

Type replacement is a trade-off between cross-immunity and cross-protection; cross-immunity leads to type replacement unless cross-protection is strong enough. With weak cross-protection, NVT prevalence may initially decrease before rebounding into type replacement, exhibiting a honeymoon period. Importantly, vaccine effectiveness for NVTs is inadequate for indicating type replacement.

Conclusions

Although postvaccination surveillance thus far is reassuring, it is still too early to preclude type replacement. Monitoring of NVTs remains pivotal in gauging population-level impacts of HPV vaccination.

Evaluation of inactivated Bordetella pertussis as a delivery system for the immunization of mice with Pneumococcal Surface Antigen A

Pneumococcal Surface Protein A (PspA) has been successfully tested as vaccine candidate against Streptococcus pneumoniae infections. Vaccines able to induce PspA-specific antibodies and Th1 cytokines usually provide protection in mice. We have shown that the whole cell pertussis vaccine (wP) or components from acellular pertussis vaccines, such as Pertussis Toxin or Filamentous Hemagglutinin (FHA), are good adjuvants to PspA, suggesting that combined pertussis-PspA vaccines would be interesting strategies against the two infections. Here, we evaluated the potential of wP as a delivery vector to PspA. Bordetella pertussis strains producing a PspA from clade 4 (PspA4Pro) fused to the N-terminal region of FHA (Fha44) were constructed and inactivated with formaldehyde for the production of wPPspA4Pro. Subcutaneous immunization of mice with wPPspA4Pro induced low levels of anti-PspA4 IgG, even after 3 doses, and did not protect against a lethal pneumococcal challenge. Prime-boost strategies using wPPspA4Pro and PspA4Pro showed that there was no advantage in using the wPPspA4Pro vaccine. Immunization of mice with purified PspA4Pro induced higher levels of antibodies and protection against pneumococcal infection than the prime-boost strategies. Finally, purified Fha44:PspA4Pro induced high levels of anti-PspA4Pro IgG, but no protection, suggesting that the antibodies induced by the fusion protein were not directed to protective epitopes.

Changes in pneumococcal carriage prevalence and factors associated with carriage in Norwegian children, four years after introduction of PCV13

Background

Streptococcus pneumoniae carriage is often asymptomatic but can cause invasive pneumococcal disease. Pneumococcal carriage is a prerequisite for disease, with children as main reservoir and transmitters. Childhood carriage can therefore be used to determine which serotypes circulate in the population and which may cause disease in the non-vaccinated population. In 2006, a pneumococcal conjugate vaccine (PCV7) was introduced into the Norwegian Childhood Immunisation Programme, which was replaced by the more valent PCV13 in 2011. We investigated changes in pneumococcal carriage prevalence 4 years after switching to PCV13 compared to three previous surveys, and analysed factors associated with carriage in children.

Methods

We conducted a cross-sectional study in Norway, autumn 2015, among children attending day-care centres. We collected questionnaire data and nasopharyngeal swabs to identify pneumococcal serotypes. We compared the carriage prevalence in 2015 with surveys conducted in the same setting performed before widespread vaccination (2006; n = 610), 2 years after PCV7 introduction (2008; n = 600), and 2 years after switching to PCV13 (2013; n = 874). Using multilevel logistic regression we determined the association between pneumococcal carriage and previously associated factors.

Results

In 2015, 896 children participated, with age ranging from 8 to 80 months. The overall carriage prevalence was 48/100 children [95%CI 44–53] in 2015, 38% [29–46] lower than in 2006 pre-PCV7, and 23% [12–32] lower than in 2013, 2 years after switching to PCV13. The PCV13 carriage prevalence was 2.8/100 children [1.9–4.2] in 2015. Increasing age (p < 0.001), recent antimicrobial use (odds ratio = 0.42 [0.21–0.57]) and being vaccinated (odds ratio = 0.37 [0.29–0.47]) were negatively associated with carriage.

Conclusions

Our study showed a continued decrease in overall pneumococcal carriage, mainly fuelled by the decline in vaccine serotypes after vaccine introduction. Childhood vaccination with PCV13 should be continued to keep low PCV13 carriage, transmission and disease. Furthermore, the low prevalence of PCV13-type carriage in children endorse the choice of not recommending PCV13 in addition to the 23-valent pneumococcal polysaccharide vaccine to most medical risk groups in Norway, as little disease caused by these serotypes can be expected.

Changing Epidemiology and Predisposing Factors for Invasive Pneumococcal Disease at Two Australian Tertiary Hospitals

BACKGROUND

Invasive pneumococcal disease (IPD) is associated with significant morbidity and mortality in children. Universal pneumococcal conjugate vaccination has changed the epidemiology of IPD. In vaccinated children, IPD can be a marker of an underlying immunodeficiency.

METHODS

This is a retrospective audit of children younger than 18 years with IPD admitted to 2 tertiary pediatric hospitals in Australia between 2011 and 2017. Data on predisposing conditions, immunologic evaluation, pneumococcal serotype, antibiotic susceptibility and treatment were collected.

RESULTS

During the 7-year period, there were 131 presentations with IPD in 127 children; 3 children had recurrent IPD. Patients presented with sepsis (41%), empyema (29%), meningitis (18%), mastoiditis (12%), pneumonia (10%) and septic arthritis (4%). In 19 (15%) presentations, risk factors for IPD were present, including malignancy, hematologic disorder, chronic liver disease, chronic kidney disease and cochlear implant. Pneumococcal serotypes were determined in 78/131 (60%) of presentations: the most frequent serotypes were 19A (19%), 3 (13%), 7F (10%) and 19F (8%) and non-vaccine serotypes 22F (8%), 35B (6%), 15A (4%) and 38 (4%). Overall, 11% of isolates were non-susceptible to ceftriaxone. Only 36 patients (32%) had an immunologic evaluation, and 4 patients had proven or probable immunodeficiency.

CONCLUSION

Although pneumococcal conjugate vaccine serotypes 19A, 3, 19F and 7F remain frequent causes of IPD, non-vaccine serotypes are emerging. Our data support vancomycin treatment for children with pneumococcal meningitis given 11% of our isolates were not susceptible to ceftriaxone. It is important to consider underlying conditions predisposing to IPD in a population with high rates of pneumococcal vaccination.

The Use of Test-negative Controls to Monitor Vaccine Effectiveness: A Systematic Review of Methodology

BACKGROUND

The test-negative design is an increasingly popular approach for estimating vaccine effectiveness (VE) due to its efficiency. This review aims to examine published test-negative design studies of VE and to explore similarities and differences in methodological choices for different diseases and vaccines.

METHODS

We conducted a systematic search on PubMed, Web of Science, and Medline, for studies reporting the effectiveness of any vaccines using a test-negative design. We screened titles and abstracts and reviewed full texts to identify relevant articles. We created a standardized form for each included article to extract information on the pathogen of interest, vaccine(s) being evaluated, study setting, clinical case definition, choices of cases and controls, and statistical approaches used to estimate VE.

RESULTS

We identified a total of 348 articles, including studies on VE against influenza virus (n = 253), rotavirus (n = 48), pneumococcus (n = 24), and nine other pathogens. Clinical case definitions used to enroll patients were similar by pathogens of interest but the sets of symptoms that defined them varied substantially. Controls could be those testing negative for the pathogen of interest, those testing positive for nonvaccine type of the pathogen of interest, or a subset of those testing positive for alternative pathogens. Most studies controlled for age, calendar time, and comorbidities.

CONCLUSIONS

Our review highlights similarities and differences in the application of the test-negative design that deserve further examination. If vaccination reduces disease severity in breakthrough infections, particular care must be taken in interpreting vaccine effectiveness estimates from test-negative design studies.

Pathogens Causing Respiratory Tract Infections in Children Less Than 5 Years of Age in Senegal

Introduction:

While acute respiratory tract infections are the main cause of paediatric mortality and morbidity worldwide, pathogen patterns shift due to factors such as hygiene, vaccinations, and antibiotic resistance. Knowledge about current cause of respiratory infections is lacking, particularly in low- and middle-income countries. The aim of this study was to identity the various respiratory pathogens causing acute respiratory tract infections in children below 5 years of age visiting a sub-urban primary care clinic in Senegal.

Methods:

A case-control study was performed in September and October 2018. Oropharyngeal swabs were collected from cases; infants with fever and respiratory symptoms, and controls; children involved in the vaccination programme. Viral identification was conducted by polymerase chain reaction for 21 different viruses; bacteria were identified by culture studies. Associations between microorganisms, acute respiratory infection and severity of disease were calculated by multivariate regression adjusting for confounders such as age, sex, and living area.

Results:

Overall, 102 cases and 96 controls were included. Microorganisms were detected in 90.1% of cases and 53.7% of controls (P < .001). Influenza virus A (including H1N1), influenza virus B, respiratory syncytial virus (RSV), and Streptococcus pneumoniae were independently associated with acute respiratory tract infections. Co-detection of two or more pathogens was present in 49.5% of cases; 31.7% of cases had a pneumonia and 90.2% was treated with antibiotics.

Conclusions:

This case-control study in a primary care setting in sub-Saharan Africa found influenza virus A and B, RSV, and S pneumoniae to be the main causes of acute respiratory tract infections in children below 5 years of age. We recommend evaluation of antibiotics prescription behaviour in this setting.

Epidemiological and molecular characterization of invasive Streptococcus pneumoniae isolated following introduction of 7-valent conjugate vaccine in Kinki region, Japan, 2008-2013

Streptococcus pneumoniae is one of the most common bacteria causing community-acquired pneumonia and meningitis. The use of 7-valent pneumococcal conjugate vaccine (PCV7) has reduced the incidence of pneumococcal disease while changing pneumococcal population through herd immunity and non-vaccine pneumococci replacement. This study investigated molecular epidemiologic characteristics of pneumococcal strains in the Kinki region of Japan from 2008 to 2013. A total of 159 invasive pneumococcal isolates were characterized by serotyping, antibiotic susceptibility testing, PCR analysis of penicillin-binding protein genes, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). In adult populations, pediatric PCV7 introduction decreased isolates expressing PCV7 serotypes via herd immunity and increased isolates expressing non-PCV7 serotypes. The rate of penicillin resistance and isolates with alterations in all three pbp genes was higher in PCV7 type isolates than in non-PCV7 type isolates. In MLST analysis, all of serotype 19F isolates were of the same sequence type, ST236, which is the antimicrobial-resistant clone Taiwan^19F-14, and the majority of serotypes 23F and 19A isolates were of ST1437 and ST3111 respectively, which are the predominant clones of antimicrobial-resistant pneumococci in Japan. In PFGE profiles, serotype 6B-ST2224, serotype 19F-ST236, serotype 19A-ST3111, and serotype 23F-ST1437 formed six separate clusters composed of genetically identical strains, and genetically identical serotype 22F-ST433 formed two different clusters between the pre- and post-PCV7 period. The results of molecular analysis suggest the spread and persistence of these identical antimicrobial resistant clones in the Kinki region and genetic changes of epidemic clone serotype 22F-ST433 before and after pediatric PCV7 introduction.

Routine infant vaccination of pneumococcal conjugate vaccines has decreased pneumonia across all age groups in Northern Spain

Since the early 2000s, pneumococcal conjugate vaccines (PCVs) have been shown to be effective in the prevention of pneumonia and invasive pneumococcal diseases. In 2011, the Galician region incorporated PCV in the routine infant immunization, the very first stable program in Spain. We aim to assess direct and indirect benefits of PCV vaccination on all-cause pneumonia in the region across different age groups using an ecological study design. For this, we calculated the annual hospitalization rates using a hospital-based disease registry. We identified all-cause pneumonia, pneumococcal pneumonia and pneumococcal invasive diseases within the registry. Hospitalization rates were computed and compared across three study periods: pre-vaccination (1998-2003), early-vaccination (2005-2009) and routine-vaccination (2011-2015). Across Northern Spain, we identified 114,873 all-cause pneumonia hospitalizations, of which 24,808 were further diagnosed with pneumococcal pneumonia. The majority were elderly > 64 years (67.3%). Hospitalizations from all-cause pneumonia had a net increase from 20.6 (pre-PCV) and 21.4/10,000 (early) to 28.4/10,000 (routine) (+32.7%, p < .0001), this is attributed to the huge number of cases in the elderly age group. In contrast, a net reduction of incidence of hospitalized pneumococcal pneumonia was observed from 6.3/10,000 (pre-PCV) and 5.7/10,000 (early) to 2.4/10,000 (routine) cases (-57.9%, p < .0001). Thus, routine infant vaccination may have resulted to an overall decline of pneumococcal pneumonia in infants, as well as in elderly age groups. However, a paradoxical increase on all-cause pneumonia was observed in Galicia, mostly attributed to the growing number of cases in the elderly population.

HPV33+ HNSCC is associated with poor prognosis and has unique genomic and immunologic landscapes

OBJECTIVE

To determine the influence of high-risk HPV genotype on outcomes in HNSCC patients.

MATERIALS AND METHODS

This is a retrospective analysis of The Cancer Genome Atlas HNSCC cohort.

RESULTS

Using multivariate Cox regression analysis, we revealed that HPV33+ HNSCC patients have inferior overall survival compared to HPV16+ HNSCC patients independent of anatomical site (HR 3.59, 95% CI 1.58-8.12; p = 0.002). A host anti-viral immune response, apolipoprotein B mRNA editing enzyme, and catalytic polypeptide-like mutational signature, was under represented and, aneuploidy and 3p loss were more frequent in HPV33+ tumors. A deconvolution RNA-Seq algorithm to infer immune cell fractions revealed that CD8+ cytotoxic T-cell infiltration was reduced in HPV33+ compared to HPV16+ tumors (1.3% vs. 2.7%, p = 0.007). TGFB1, a negative modulator of T-cell infiltration and function, showed expression and pathway enrichment in HPV33+ tumors.

CONCLUSIONS

Our work reveals that HPV genotype, in particular HPV33, has a powerful impact on HNSCC patient survival. We argue that p16 immunohistochemistry as a surrogate biomarker for HPV+ status will lead to sub-optimal risk stratification and advocate HPV genotype testing as standard of care.

Determinants of high residual post-PCV13 pneumococcal vaccine-type carriage in Blantyre, Malawi: a modelling study

BACKGROUND

In November 2011, Malawi introduced the 13-valent pneumococcal conjugate vaccine (PCV13) into the routine infant schedule. Four to 7 years after introduction (2015-2018), rolling prospective nasopharyngeal carriage surveys were performed in the city of Blantyre. Carriage of Streptococcus pneumoniae vaccine serotypes (VT) remained higher than reported in high-income countries, and impact was asymmetric across age groups.

METHODS

A dynamic transmission model was fit to survey data using a Bayesian Markov-chain Monte Carlo approach, to obtain insights into the determinants of post-PCV13 age-specific VT carriage.

RESULTS

Accumulation of naturally acquired immunity with age and age-specific transmission potential were both key to reproducing the observed data. VT carriage reduction peaked sequentially over time, earlier in younger and later in older age groups. Estimated vaccine efficacy (protection against carriage) was 66.87% (95% CI 50.49-82.26%), similar to previous estimates. Ten-year projected vaccine impact (VT carriage reduction) among 0-9 years old was lower than observed in other settings, at 76.23% (CI 95% 68.02-81.96%), with sensitivity analyses demonstrating this to be mainly driven by a high local force of infection.

CONCLUSIONS

There are both vaccine-related and host-related determinants of post-PCV13 pneumococcal VT transmission in Blantyre with vaccine impact determined by an age-specific, local force of infection. These findings are likely to be generalisable to other Sub-Saharan African countries in which PCV impact on carriage (and therefore herd protection) has been lower than desired, and have implications for the interpretation of post-PCV carriage studies and future vaccination programs.

Prevalence of PspA families and pilus islets among Streptococcus pneumoniae colonizing children before and after universal use of pneumococcal conjugate vaccines in Brazil

In 2010, the 10-valent (PCV10) and 13-valent (PCV13) pneumococcal conjugate vaccines were introduced in Brazil to immunize children, resulting in serotype replacement. We analyzed 253 carriage isolates recovered from children aged <6 years in Brazil, including 124 and 129 isolates from the pre-PCV10/13 (December 2009-July 2010) and post-PCV10/13 (September-December 2014) periods, respectively, to investigate the prevalence of PspA families and pilus islets, potential vaccine candidates. Serotypes and resistance profiles were previously characterized. We used PCR to type PspA families (Fam1-3) and pilus islets (PI-1 and PI-2). We identified the PspA family of 130 (51.4%) isolates. PspA families 1, 2, and 3 were identified in 12.2%, 38.7%, and 0.4% of the isolates, respectively. Eighteen (58.1%) Fam1 isolates were serogroup 6. Nine (81.8%) of 11 serotype 14 isolates were Fam2. Fam1 isolates resistant to penicillin (50%), erythromycin (43.7%), clindamycin (31.2%), and chloramphenicol (6.2%) were only found after PCV10/13 introduction. Resistance among Fam2 isolates was higher in the post-PCV10/13 period to erythromycin (1.8% vs. 18.6%), clindamycin (0 vs. 13.9%), and tetracycline (10.9% vs. 16.3%). PI-I was detected in 42 (16.6%) isolates. Fourteen (56%) of 25 serotype 15B/C and nine (81.8%) of 11 serotype 14 isolates had PI-1 (p < 0.01). Eight (3.2%) isolates had PI-2, and six (75%) were serogroup 19. Five (2%) serogroup 19 isolates had both PI-1 and PI-2. We found associations between serogroups/serotypes, PspA families, and pilus islets, but distribution of PspA families and pilus islets was similar in both periods. After universal vaccination, we observed higher antimicrobial resistance frequencies, regardless PspA or pilus types.

Increasing Rates of Pediatric Empyema and Disease Severity With Predominance of Serotype 3 S. pneumonia: An Australian Single-center, Retrospective Cohort 2011 to 2018

BACKGROUND

The impact of universal 13-valent pneumococcal conjugate vaccine immunization on pediatric empyema rates and pathogens in Australia is not known. We aimed to describe empyema epidemiology, clinical characteristics and treatment during an 8-year period.

METHODS

A retrospective study between 2011 and 2018 of empyema cases admitted to a large pediatric referral hospital, for management with either pleural drainage and fibrinolytics or surgical intervention.

RESULTS

There were 195 cases in 8 years. Empyema incidence and ICU admission rates significantly increased during the study with a peak incidence of 7.1/1000 medical admissions in 2016 (χ for trend of incidence 37.8, P < 0.001 and for ICU admissions 15.3, P < 0.001). S. pneumoniae was the most common pathogen (75/195, 39%) with serotype 3 the most detected (27/75: 27%). S. pyogenes compared with S. pneumoniae had significantly fewer days of fever before admission (3.9 vs. 6.4, mean difference 2.4, 95% CI: 0.84-4.08, P = 0.003) and higher proportion requiring direct ICU admission (6/75; 8% vs. 7/15; 47%, P < 0.001). Compared with S. pneumoniae, cases with no pathogen detected by culture or PCR had fewer days of fever post intervention (4.4 vs. 7.4 days, mean difference 2.7 days, P = 0.002). S. aureus occurred more commonly in infants (10/25; 40% vs. 1/75; 1%, P < 0.001) and children of indigenous background (5/25; 20% vs. 1/75; 1%, P < 0.001) compared with S. pneumoniae.

CONCLUSIONS

We report increasing rates of pediatric empyema with higher proportions requiring ICU treatment. The most common pathogens detected were S. pneumoniae, S. aureus and S. pyogenes. Despite high 13-valent pneumococcal conjugate vaccine coverage, serotype 3 was the most common S. pneumoniae serotype identified.

Pneumococcal conjugate serotype distribution and predominating role of serotype 3 in German adults with community-acquired pneumonia

INTRODUCTION

Implementation of the 7-valent pneumococcal conjugate vaccine (PCV7) in infant vaccination programs has substantially reduced the burden of PCV7 serotypes also in adult community-acquired pneumonia (CAP). Currently, it is unclear, if this extensive herd protection effect can be extrapolated to the additional 6 serotypes included in the 13-valent pneumococcal conjugate vaccine (PCV13), which replaced PCV7 in Germany in 2010.

OBJECTIVES

We investigated changing trends for PCV13 serotypes in adult CAP patients between three to seven years after implementation of PCV13 infant immunization in Germany.

METHODS

Between December 2012 and January 2017, urine samples from German adult patients with radiologically confirmed CAP were prospectively collected by the multi-center cohort study CAPNETZ and analyzed by the serotype-specific multiplex urinary antigen detection assay (SSUAD) allowing for the detection of PCV13 serotypes.

RESULTS

PCV13 serotypes were found in 59 of 796 (7.4%) patients with all-cause CAP, most prevalent was serotype 3 (30 of 59 patients, 50.8%). All patients with serotype 3-CAP were admitted to hospital and the majority required oxygen at admission (83.3% of patients with serotype 3-CAP versus 50.9% of patients with pneumococcal CAP by other serotypes, p = 0.005). Compared to SSUAD testing, conventional microbiological workup missed 27 of 30 (90.0%) serotype 3-CAP cases. We could not observe a time trend in the proportions of PCV13 serotypes and serotype 3 in all-cause CAP between 2013 and 2016 (OR trend per year 0.84, 95% CI 0.64-1.11 for PCV13 serotypes and OR trend per year 0.95, 95% CI 0.70-1.28 for serotype 3).

CONCLUSIONS

Conventional methods underestimate serotype 3-CAP that can cause severe disease. Changes in overall PCV13 coverage were not detected during the years 2013 to 2016, mostly driven by a high proportion of serotype 3.

Expression of the Nontypeable Haemophilus influenzae Type IV Pilus Is Stimulated by Coculture with Host Respiratory Tract Epithelial Cells

The type IV pilus (Tfp) of nontypeable Haemophilus influenzae (NTHI) mediates adherence, colonization, motility, and biofilm formation, and the major protein subunit, PilA, is a promising vaccine candidate. Thus, it is crucial to understand how Tfp expression is regulated within the microenvironments of the human nasopharynx, which NTHI colonizes asymptomatically, and the more distal regions of the respiratory tract where NTHI-induced diseases occur. Here, we examined the effects of coculture of NTHI with human airway epithelial cells and heme availability on Tfp expression at temperatures typical of the human nasopharynx (34°C) or warmer anatomical sites during infection (37°C). Tfp expression was estimated by pilA promoter activity, pilA gene expression, and relative abundances of PilA and pilin protein. The results revealed that at both temperatures, NTHI cocultured with airway epithelial cells demonstrated significantly greater expression of pilA, PilA/pilin protein, and likely, fully assembled Tfp than NTHI cultured on an abiotic surface. Because NTHI is a heme auxotroph, we hypothesized that availability of heme from host cells might be a signal for Tfp expression. Thereby, we cultured NTHI in iron-limited medium, and we observed that supplementation with heme significantly increased pilA promoter activity. Collectively, our data suggested that NTHI Tfp expression was stimulated by soluble factor(s) released by epithelial cells, which are present in all microenvironments of the respiratory tract. The expression of this target antigen under conditions that mimic the human airway strongly supports the rationale for the use of PilA as a vaccine immunogen to prevent NTHI-induced diseases of the respiratory tract.

Identification of Pneumococcal Serotypes by PCR-Restriction Fragment Length Polymorphism

Streptococcus pneumoniae shows more than 90 capsular serotypes that can be distinguished by their reactivity against antisera. The main objective of this work was the development of a molecular method for serotyping without the use of antisera. A computer program containing an algorithm was used to search in a database for potentially useful enzymes for Restriction Fragment Length Polymorphism-RFLP typing, in order to maximize the discrimination between different serotypes. DNA sequences of 90 serotypes for the region between dexB and aliA genes were compiled, and a computer screening of restriction enzymes was performed. The wzg–wzh–wzd–wze region and Sse9I restriction predicted unique PCR-RFLP patterns for 39 serotypes and eight serogroups. A second restriction enzyme resolved fragment specific patterns for 25 serotypes. The method was tested with 98 serotype-unknown clinical isolates. PCR-RFLP analysis deduced correct serotypes that were confirmed by Quellung reaction for 78.5% of the isolates.

Pneumococcal Vaccines

Streptococcus pneumoniae is a Gram-Positive pathogen that is a major causative agent of pneumonia, otitis media, sepsis and meningitis across the world. The World Health Organization estimates that globally over 500,000 children are killed each year by this pathogen. Vaccines offer the best protection against S. pneumoniae infections. The current polysaccharide conjugate vaccines have been very effective in reducing rates of invasive pneumococcal disease caused by vaccine type strains. However, the effectiveness of these vaccines have been somewhat diminished by the increasing numbers of cases of invasive disease caused by non-vaccine type strains, a phenomenon known as serotype replacement. Since, there are currently at least 98 known serotypes of S. pneumoniae, it may become cumbersome and expensive to add many additional serotypes to the current 13-valent vaccine, to circumvent the effect of serotype replacement. Hence, alternative serotype independent strategies, such as vaccination with highly cross-reactive pneumococcal protein antigens, should continue to be investigated to address this problem. This chapter provides a comprehensive discussion of pneumococcal vaccines past and present, protein antigens that are currently under investigation as vaccine candidates, and other alternatives, such as the pneumococcal whole cell vaccine, that may be successful in reducing current rates of disease caused by S. pneumoniae.

Phosphorylcholine intranasal immunization with a 13-valent pneumococcal conjugate vaccine can boost immune response against Streptococcus pneumoniae

OBJECTIVE

This study aimed to investigate whether systemic immunization with a 13-valent pneumococcal conjugate vaccine (PCV13) followed by intranasal (IN) immunization with phosphorylcholine (PC) can boost immune response against Streptococcus pneumoniae.

MATERIALS AND METHODS

Two weeks after the intraperitoneal (IP) injection of PCV13, mice were divided into two groups (mice requiring another IP injection of PCV13 and mice requiring PC-keyhole limpet hemocyanin IN immunization in combination with cholera toxin as a mucosal adjuvant) to compare the magnitude of systemic and mucosal immune responses against S. pneumoniae and PC.

RESULTS

Serum immunoglobulin (Ig) G antibody titer against the vaccine strains of S. pneumoniae was similar between the PCV13 systemic immunization group and PC IN immunization group, while the serum IgG antibody titer against PC was significantly higher in the PC IN immunization group. PC-specific IgA antibody titer in the nasal lavage and PC-specific IgA-producing cell number in the nasal mucosa were also significantly higher in the PC IN immunization group. Induction of PC-specific IgA in the PC IN immunization group enhanced the clearance of bacteria from the middle ear.

CONCLUSION

Additional IN immunization with PC after PCV13 immunization, which is currently conducted under a periodic vaccination program, can produce a booster effect comparable to that achieved by additional systemic immunization as well as PC-specific mucosal immune response, thereby providing protection against S. pneumoniae serotypes not contained in PCV13.

The impact of routine childhood immunization with higher-valent pneumococcal conjugate vaccines on antimicrobial-resistant pneumococcal diseases and carriage: a systematic literature review

Introduction: The introduction of 7-valent pneumococcal conjugate vaccine (PCV7) in childhood immunization programs reduced antimicrobial-resistant pneumococcal infections by vaccine serotypes. However, emerging antimicrobial-resistant non-vaccine serotypes, particularly serotype 19A, attenuated the overall effect. In 2010, higher-valent PCVs became available containing serotypes that are prone to become antimicrobial-resistant, like serotype 7F in PCV10 and PCV13, and serotype 19A in PCV13.Areas covered: This review evaluated literature published between June 1, 2008 and June 1, 2017 reporting on the effect of PCV10 or PCV13 implementation in routine infant immunization schedules on antimicrobial-resistant invasive pneumococcal disease (IPD), otitis media (OM), and nasopharyngeal carriage (NPC) in children and adults.Expert opinion: In countries with relatively high prior pneumococcal antimicrobial resistance (AMR), PCV13 childhood vaccination programs have reduced antimicrobial-resistant IPD, OM, and NPC in children and IPD in adults. The effectiveness of PCV13 against serotype 19A is likely an important contributing factor. Only few studies have documented the impact of PCV10 on AMR. Multiple factors may influence observed decreases in pneumococcal AMR including antimicrobial stewardship, case definition, time since PCV10/13 introduction, and pre-PCV10/13 AMR levels. This review emphasizes the importance of including impact on AMR when evaluating the full public health of pneumococcal vaccination programs.

Next-Generation Whole-Cell Pneumococcal Vaccine

Streptococcus pneumoniae remains a major public health hazard. Although Pneumococcal Conjugate Vaccines (PCVs) are available and have significantly reduced the rate of invasive pneumococcal diseases, there is still a need for new vaccines with unlimited serotype coverage, long-lasting protection, and lower cost to be developed. One of the most promising candidates is the Whole-Cell Pneumococcal Vaccine (WCV). The new generation of whole-cell vaccines is based on an unencapsulated serotype that allows the expression of many bacterial antigens at a lower cost than a recombinant vaccine. These vaccines have been extensively studied, are currently in human trial phase 1/2, and seem to be the best treatment choice for pneumococcal diseases, especially for developing countries.

Impact of pneumococcal conjugate vaccines introduction on antibiotic resistance of Streptococcus pneumoniae meningitis in children aged 5 years or younger, Israel, 2004 to 2016

Background

Empiric treatment of pneumococcal meningitis includes ceftriaxone with vancomycin to overcome ceftriaxone resistant disease. The addition of vancomycin bears a risk of adverse events, including increased antibiotic resistance. We assessed antibiotic resistance rates in pneumococcal meningitis before and after pneumococcal conjugate vaccine (PCV) implementation.

Methods

All pneumococcal meningitis episodes in children aged 5 years and younger, from 2004 to 2016, were extracted from the nationwide bacteremia and meningitis surveillance database. For comparison purposes, we defined pre-PCV period as 2004–2008 and PCV13 period as 2014–2016. Minimal inhibitory concentration (MIC) > 0.06 and > 0.5 μg/mL were defined as penicillin and ceftriaxone resistance, respectively.

Results

Overall, 325 episodes were identified. Pneumococcal meningitis incidence rates declined non-significantly by 17%, comparing PCV13 and pre-PCV periods. Throughout the study, 90% of isolates were tested for antibiotic susceptibility, with 26.6%, 2.1% and 0% of isolates resistant to penicillin, ceftriaxone and vancomycin, respectively. Mean proportions (± SD) of meningitis caused by penicillin-resistant pneumococci were 40.5% ± 8.0% and 9.6% ± 7.4% in the pre-PCV and the PCV13 periods, respectively, resulting in an overall 83.9% reduction (odd ratio:0.161; 95% confidence interval: 0.059–0.441) in penicillin resistance rates. The proportions of meningitis caused by ceftriaxone resistant pneumococci were 5.0% ± 0.8% in the pre-PCV period, but no ceftriaxone resistant isolates were identified since 2010.

Conclusions

PCV7/PCV13 sequential introduction resulted in > 80% reduction of penicillin- resistant pneumococcal meningitis and complete disappearance of ceftriaxone resistant disease. These trends should be considered by the treating physician when choosing an empiric treatment for pneumococcal meningitis.

Receptor Blockade: A Novel Approach to Protect the Brain From Pneumococcal Invasion

Background

Pneumococci are the major cause of bacterial meningitis globally. To cause meningitis pneumococci interact with the 2 endothelial receptors, polymeric immunoglobulin receptor (pIgR) and platelet endothelial cell adhesion molecule (PECAM-1), to penetrate the blood-brain barrier (BBB) and invade the brain.

Methods

C57BL/6 mice were infected intravenously with bioluminescent pneumococci, and treated with ceftriaxone (1 hour postinfection) and anti-pIgR and PECAM-1 antibodies (1 or 5 hours postinfection), then monitored for 5 and 10 days. Bacterial brain invasion was analyzed using IVIS imaging and bacterial counts.

Results

Ceftriaxone, given early after pneumococcal challenge, cleared pneumococci from the blood but not from the brain. After combining ceftriaxone with receptor blockade, using anti-pIgR and PECAM-1 antibodies, we found 100% survival after 5 and 10 days of infection, in contrast to 60% for ceftriaxone alone. Combined antibiotic and antibody treatment resulted in no or few viable bacteria in the brain and no microglia activation. Antibodies remained bound to the receptors during the study period. Receptor blockade did not interfere with antibiotic permeability through the BBB.

Conclusions

We suggest that adjunct treatment with pIgR and PECAM-1 antibodies to antibiotics may prevent pneumococcal meningitis development and associated brain damages. However, further evaluations are required.

Designing self-assembled peptide nanovaccine against Streptococcus pneumoniae: An in silico strategy

Streptococcus pneumoniae is the main cause of diseases such as meningitis, pneumoniae and sepsis, especially in children and old people. Due to costly antibiotic treatment, and increasing resistance of pneumococcus, developing high-efficient protective vaccine against this pathogen is an urgent need. Although the pneumoniae polysaccharide vaccine (PPV) and pneumonia conjugate vaccines (PCV) are the efficient pneumococcal vaccine in children and adult groups, but the serotype replacement of S. pneumoniae strains causes the reduction in efficacy of such vaccines. For overcoming the aforesaid drawbacks epitope-based vaccines are introduced as the relevant alternative. In our previous research, the epitope vaccine was designed based on immunodominant epitopes from PspA, CbpA antigens as cellular stimulants and PhtD, PiuA as humoral stimulants. Because the low immunogenicity is the main disadvantage of epitope vaccine, in the current study, we applied coiled-coil self-assembled structures for developing our vaccine. Recently, self-assembled peptide nanoparticles (SAPNs) have gained much attention in the field of vaccine development due to their multivalency, self-adjuvanticity, biocompatibility, and size similarity to pathogen. In this regard, the final designed vaccine is comprised of cytotoxic T lymphocytes (CTL) epitopes from PspA and CbpA, helper T lymphocytes (HTL) epitopes from PhtD and PiuA, the pentamer and trimmer oligomeric domains form 5-stranded and 3-stranded coiled-coils as self-assembled scaffold, Diphtheria toxoids (DTD) as a universal T-helper, which fused to each other with appropriate linkers. The four different arrangements based on the order of above-mentioned compartments were constructed, and each of them were modeled, and validated to find the 3D structure. The structural, physicochemical, and immunoinformatics analyses of final vaccine construct represented that our vaccine could stimulate potent immune response against S. pneumoniae; however, the potency of that should be approved via various in vivo and in vitro immunological tests.

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Stimulating cellular and especially humoral immunities are essential for protection against Streptococcus Pneumoniae.

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Immunodominant epitopes were selected from highly protective antigens of S. pneumoniae: PspA, CbpA, PiuA, PhtD.

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In order to bypass the low immunogenicity of epitope-based peptide vaccine the self-assembled motifs, coiled-coil structure, was applied as the vaccine scaffold.

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The structural, physicochemical, and immunoinformatics results indicate that the designed vaccine can incite strong immune response against S. pneumoniae.

Using pneumococcal carriage studies to monitor vaccine impact in low- and middle-income countries

Pneumococcal disease is a leading cause of childhood mortality, globally. The pneumococcal conjugate vaccine (PCV) has been introduced to many countries worldwide. However there are few studies evaluating PCV impacts in low- and middle-income countries (LMIC) because measuring the impact of PCV on pneumococcal disease in LMICs is challenging. We review the role of pneumococcal carriage studies for the evaluation of PCVs in LMICs and discuss optimal methods for conducting these studies. Fifteen carriage studies from 13 LMICs quantified the effects of PCV on carriage, and identified replacement carriage serotypes in the post-PCV era. Ten studies reported on the indirect effects of PCV on carriage. Results can be used to inform cost-effectiveness evaluations, guide policy decisions on dosing and product, and monitor equity in program implementation. Critically, we highlight gaps in our understanding of serotype replacement disease in LMICs and identify priorities for research to address this gap.

Molecular serotyping and genotyping of penicillin non-susceptible pneumococci: the introduction of new sequence types, Tehran, Iran

The emergence of penicillin non-susceptible Streptococcus pneumoniae (PNSP) isolates can pose significant challenges to today's health-care system. Resistant clonal isolates are disseminated in different regions and countries, and this study was focused on the description of the epidemiological spread of these strains. Clinical samples were collected from individuals admitted to hospitals affiliated to the Tehran University of Medical Sciences, Iran. To investigate the molecular characteristics of PNSP isolates, they were subjected to molecular typing using multi-locus sequence typing (MLST). Serotype distributions of S. pneumoniae isolates were also evaluated by multiplex PCR assay. The most prevalent serotypes in the PNSP isolates were 23F, 19F, 14, 3 and 9V. Two isolates were considered as a non-vaccine serotype. The MLST analysis showed that PNSP isolates belonged to five different clonal complexes (CC180, CC217, CC81, CC63 and CC320) and 42% (5/12) of the sequence types were novel (12936, 12937, 12938, 12939 and 12940). This study indicates the high level of heterogeneity that is present among PNSP isolates. Unexpected high genetic diversity in small populations indicates consecutive diversification of resistant strains.

Effectiveness of pneumococcal conjugate vaccine against hospital admissions for pneumonia in Australian children: a retrospective, population-based, record-linked cohort study

BACKGROUND

Reductions in pneumonia hospitalisations following introduction of pneumococcal conjugate vaccines (PCVs) have been reported from high-incidence and low-incidence settings but long-term data comparing vaccinated with unvaccinated children are sparse.

METHODS

We did a retrospective, population-based, record-linkage cohort study in Australian children using administrative health data from the Western Australian Midwives' Notification System and New South Wales Perinatal Data Collection, and the birth and death registries in both states. PCV vaccination details, pneumonia-coded hospital admissions, and invasive pneumococcal disease notification records were individually linked for children born between 2001 and 2012. The primary outcome was defined as the first hospital admission for all-cause pneumonia. Cox models were used to calculate adjusted hazard ratios (HR) to estimate the effect of PCV doses on pneumonia-coded hospital admissions by Aboriginal status, birth period, remoteness, and pneumonia diagnostic category in children younger than 2 years. Person-time of follow-up time for each child started at birth and was censored at the earliest of first hospital admission for all-cause pneumonia, death, invalid PCV dose, when the child reached age 24 months, or the end date of the study period (Dec 31, 2013) FINDINGS: The study cohort comprised 1 365 893 children liveborn between Jan 1, 2001, and Dec 31, 2012, of whom 66 484 (4·9%) were identified as Aboriginal. The overall rate for all-cause pneumonia hospital admissions for children younger than 2 years over the entire study period was 17·6/1000 child-years in Aboriginal children and 5·5/1000 child-years in non-Aboriginal children. Compared with children born between 2001 and 2004 (ie, the pre-universal PCV period), the incidence of pneumonia-coded hospital admissions decreased in both vaccinated (6·5 vs 5·7 per 1000 child-years [12% reduction, 95% CI 3-21; p=0·01]) and unvaccinated non-Aboriginal children (6·8 vs 3·7 [45% reduction; 41-49]) born 2005-12 (the universal PCV period); among Aboriginal children, declines were significant only among those vaccinated (27·4 vs 14·1 [49% reduction, 40-55]). Among Aboriginal children born 2005-12, the risk of pneumonia-coded hospital admission after three doses of PCV was lower than those unvaccinated (adjusted HR 0·83, 95% CI 0·65-0·99) but, among non-Aboriginal children, the risk was similar (adjusted HR 1·09, 0·98-1·22). Overall, remote-born Aboriginal children had the highest incidence of hospital admission for pneumonia and among children born 2005-12, the adjusted risk was 37% lower (adjusted HR 0·63, 95% CI 0·42-0·96) among those fully vaccinated than those unvaccinated.

INTERPRETATION

Reductions in pneumonia-coded hospital admissions in unvaccinated children predominated in non-Aboriginal children with low incidence of pneumonia but were not significant in Aboriginal children with high incidence. These findings have potential implications for measuring PCV effect using a non-specific endpoint such as all-cause pneumonia in high-incidence populations.

FUNDING

Commonwealth Government Collaborative Research Infrastructure Strategy and Education Investment Fund Super Science Initiative and the Australian National Health and Medical Research Council.

Effectiveness of pneumococcal conjugate vaccination against invasive pneumococcal disease among children with and those without HIV infection: a systematic review and meta-analysis

Background

HIV-infected children are at a higher risk of Invasive Pneumococcal Disease (IPD) and its mortality, even in the era of antiretroviral therapy. Therefore, an effective vaccination strategy would be beneficial. To investigate the effectiveness of Pneumococcal Conjugate Vaccination (PCV) against IPD among HIV-Infected and HIV-Uninfected Children through a systematic review and meta-analysis.

Methods

Observational studies and randomized trials on 7 years old or older children were searched in the Cochrane Library, Web of Science core collection, Embase, Medline/PubMed, and Google Scholar. Critical appraisal was done using the Cochrane risk of bias tool and the Newcastle-Ottawa quality assessment form. Effectiveness and efficacy of at least one dose of PCV was investigated among children with and without HIV considering subgroups of pneumococcal serotypes. We meta-analyzed the effect sizes using random-effects modeling.

Results

Efficacy of PCV was estimated as 45.0% (31.2, 56.1) and 52.6% (25.7, 69.8) among HIV-infected and HIV-uninfected children, respectively. Effectiveness of PCV among HIV-infected children as − 6.2% (− 67.6, 32.7) was significantly lower than HIV-uninfected children 65.1% (47.3, 76.9). Effectiveness of PCV among HIV-infected children for IPDs caused by vaccine serotypes was estimated as 7.7(− 66.7, 48.9), and for IPDs caused by non-vaccine serotypes was estimated as − 402.8(− 1856, − 29.2).

Conclusion

Unlike the evidence on the efficacy of PCV against IPD among both of HIV-infected and HIV-uninfected children, its effectiveness against IPD among HIV-infected children is much less limited.

Review registration

The study protocol was registered at PROSPERO (registration ID: CRD42018108187).

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4325-4) contains supplementary material, which is available to authorized users.

Evaluation of the impact of 13-valent pneumococcal conjugate vaccine immunization in children by surveillance of culture-confirmed pneumococcal disease: A prospective clinical microbiological study

The study aimed to investigate the impact of 13-valent pneumococcal conjugate vaccine (PCV13) immunization on the overall pneumococcal disease in children in Taiwan by surveillance of culture-confirmed pneumococcal disease (CCPD). This study was conducted in a medical center from 2012 to 2016. Clinical isolates of Streptococcus pneumoniae were prospectively collected from pediatric patients. Serotyping, multi-locus sequence typing, and antimicrobial susceptibility testing were performed. A total of 473 patients with CCPD, including 58 with invasive pneumococcal disease (IPD), were identified. The incidence of CCPD per 10,000 admissions decreased from 71.7 in 2012 to 27.0 in 2016. The proportion of additional PCV13 serotypes significantly decreased from 52.0% in 2012 to 21.7% in 2015 but increased slightly to 26.7% because of serotype 19A in 2016 (P < 0.0001). The proportion of non-vaccine serotypes (NVTs) increased significantly from 18.4% in 2012 to 66.7% in 2016, but the increase of the incidence of CCPD caused by NVTs was not considered significant (P = 0.0885). Genotyping identified predominant clones, ST63^15A, ST83^15B, and ST166/338^23A, for major NVTs. The penicillin non-susceptibility of PCV13 serotypes was significantly higher than that of NVTs (P < 0.0001). Surveillance of CCPD appears superior to IPD alone for evaluation of the overall impact of pneumococcal immunization. Serotype replacement occurred quickly after the use of PCV13, while the incidence of NVT infection did not show a significant increase in children over the years. The gradual introduction of PCV13 into national immunization program is effective in reducing overall pneumococcal disease in children.

Progress in mucosal immunization for protection against pneumococcal pneumonia

Introduction: Lower respiratory tract infections are the fourth cause of death worldwide and pneumococcus is the leading cause of pneumonia. Nonetheless, existing pneumococcal vaccines are less effective against pneumonia than invasive diseases and serotype replacement is a major concern. Protein antigens could induce serotype-independent protection, and mucosal immunization could offer local and systemic immune responses and induce protection against pneumococcal colonization and lung infection. Areas covered: Immunity induced in the experimental human pneumococcal carriage model, approaches to address the physiological barriers to mucosal immunization and improve delivery of the vaccine antigens, different strategies already tested for pneumococcal mucosal vaccination, including live recombinant bacteria, nanoparticles, bacterium-like particles, and nanogels as well as, nasal, pulmonary, sublingual and oral routes of vaccination. Expert opinion: The most promising delivery systems are based on nanoparticles, bacterial-like particles or nanogels, which possess greater immunogenicity than the antigen alone and are considered safer than approaches based on living cells or toxoids. These particles can protect the antigen from degradation, eliminating the refrigeration need during storage and allowing the manufacture of dry powder formulations. They can also increase antigen uptake, control release of antigen and trigger innate immune responses.

Direct effect of the 13-valent pneumococcal conjugate vaccine use on pneumococcal colonization among children in Brazil

BACKGROUND

The 13-valent pneumococcal conjugate vaccine (PCV13) has been commercially available in Brazil since 2010. We investigated the carriage prevalence, capsular types, and antimicrobial resistance among pneumococci isolated from children immunized with PCV13 in Brazil.

METHODS

We analyzed 500 children < 6 years old attending public (n = 270) and private (n = 230) clinics in Niterói/RJ, Brazil, in 2014. We determined the antimicrobial susceptibility and capsular types for all isolates.

RESULTS

Thirty-eight (7.6%) of 500 children had received at least one PCV13 dose. Since only two (0.7%) of 270 children at the public clinic were vaccinated with PCV13, major analyses focused on 36 (15.7%) of 230 children attending private clinics. Nine (25%) of 36 children were pneumococcal carriers. Characteristics associated with carriage were age ≥ 2 years, cough/expectoration, and childcare center attendance (p ≤ 0.01). The capsular types found were 15B/C (n = 2), 6C, 11A/D, 16F, 23A, and 23F. Two isolates were non-typeable (NT). Three (33.3%) isolates were multidrug resistant. We found four (44.4%) penicillin non-susceptible pneumococci, with penicillin and ceftriaxone MICs ranging from 0.12 to 4.0 µg/ml and 0.023-0.5 µg/ml, respectively. We also detected two (22.2%) erythromycin-resistant isolates (MICs of 3.0 and 256 µg/ml).

CONCLUSIONS

Colonization with PCV13 serotype was rare among the vaccinated children. Increasing PCV13 coverage might help reduce the frequency of major serotypes currently associated with invasive pneumococcal diseases in Brazil, such as 3 and 19A. The isolation of multidrug-resistant serotype 6C and NT isolates in carriage, however, requires close monitoring.

Epidemiology of community-acquired bacterial meningitis

PURPOSE OF REVIEW

The epidemiology of bacterial meningitis has been dynamic in the past 30 years following introduction of conjugated vaccines against Haemophilus influenzae type B, Streptococcus pneumoniae and Neisseria meningitidis. The purpose of this review is to describe recent developments in bacterial meningitis epidemiology.

RECENT FINDINGS

The incidence of bacterial meningitis in Western countries (Finland, Netherlands, and the United States) gradually declined by 3-4% per year to 0.7-0.9 per 100 000 per year in the past 10-20 years. In African countries (Burkina Faso and Malawi), incidence rates are still substantially higher at 10-40 per 100 000 persons per year. Introduction of pneumococcal conjugate vaccines have not consistently decreased overall pneumococcal meningitis incidence because of serotype replacement. Following the introduction of serogroup A and C meningococcal vaccines, the incidence of meningococcal meningitis because of these serogroups strongly decreased. Novel outbreaks in the African meningitis belt by serogroup C and increased incidence of serogroup W in the United Kingdom and the Netherlands were observed recently.

SUMMARY

Bacterial meningitis remains an important infectious disease, despite a gradual decline in incidence after large-scale vaccination campaigns. Further development of vaccines with broader coverage is important, as is continuous surveillance of bacterial meningitis cases.

Diminished Capsule Exacerbates Virulence, Blood-Brain Barrier Penetration, Intracellular Persistence, and Antibiotic Evasion of Hyperhemolytic Group B Streptococci

Group B streptococci (GBS) are encapsulated, β-hemolytic bacteria that are a common cause of infections in human newborns and certain adults. Two factors important for GBS virulence are the sialic acid capsular polysaccharide that promotes immune evasion and the hemolytic pigment that induces host cell cytotoxcity. These virulence factors are often oppositely regulated by the CovR/CovS two-component system. Clinical GBS strains exhibiting hyperhemolysis and low capsule due to pathoadaptive covR/S mutations have been isolated from patients. Given the importance of capsule to GBS virulence, we predicted that a decrease or loss of capsule would attenuate the virulence of covR/S mutants. Surprisingly, hyperhemolytic GBS with low or no capsule exhibit increased virulence, intracellular persistence, and blood-brain barrier penetration, which was independent of a Trojan horse mechanism of barrier penetration. Additionally, intracellular persistence enabled both hemolytic and hyperhemolytic GBS to evade antibiotics routinely used to treat these infections. The finding that diminished capsule expression promotes GBS virulence, intracellular persistence, and antibiotic evasion has important implications for sustained antibiotic therapy and efficacy of capsule-based vaccines.

Identification and capsular serotype sequetyping of Streptococcus pneumoniae strains

PURPOSE

Correct serotype identification of Streptococcus pneumoniae (pneumococcus) is important for monitoring disease epidemiology and assessing the impacts of pneumococcal vaccines. Furthermore, correct identification and differentiation of the pathogenic S. pneumoniae from closely related commensal species of the mitis group of the genus Streptococcus are essential for correct serotype identification.

METHODOLOGY

A new protocol for determining the existing 98 serotypes of pneumococcus was developed, applying two PCR amplifications and amplicon sequencing, using newly designed internal primers. The new protocol was validated using S. pneumoniae genome sequences, reference strains with confirmed serotypes and clinical isolates, and comparing the results with those from the traditional Quellung reaction or antiserum panel gel precipitation, in addition to real-time PCR analysis. The taxonomic identifications of 422 publicly available (GenBank) genome sequences of S. pneumoniae, Streptococcus pseudopneumoniae and Streptococcus mitis were assessed by whole-genome sequence average nucleotide identity based on blast (ANIb) analysis.

RESULTS

The proposed sequetyping protocol generates a 1017 bp whole cpsB region sequence, increasing resolution for serotype identification in pneumococcus isolates. The identifications of all GenBank genome sequences of S. pneumoniae were confirmed, whereas most of the S. pseudopneumoniae and almost all of the S. mitis genome sequences did not fulfil the ANIb thresholds for species-level identification. The housekeeping biomarker gene, groEL, correctly identified S. pneumoniae but often misclassified S. pseudopneumoniae and S. mitis as S. pneumoniae.

CONCLUSIONS

These studies affirm the importance of applying reliable identification protocols for S. pneumoniae before serotyping; our protocols provide reliable diagnostic tools, as well as an improved workflow, for serotype identification of pneumococcus and differentiation of serogroup 6 types.

Population structure of Streptococcus pneumoniae colonizing children before and after universal use of pneumococcal conjugate vaccines in Brazil: emergence and expansion of the MDR serotype 6C-CC386 lineage

Objectives

To determine the population structure and change in drug resistance of pneumococci colonizing children before and after the introduction of the 10-valent and 13-valent pneumococcal conjugate vaccines (PCV10/13) in Brazil.

Methods

We used MLST to analyse 256 pneumococcal isolates obtained from children aged <6 years before (2009-10; n = 125) and after (2014; n = 131) the introduction of the PCV10 and PCV13. Antimicrobial susceptibility and capsular types were previously determined.

Results

We identified 97 different STs. Ninety (35.2%) isolates were related to international clones. The most frequent lineages were serogroup 6-CC724 (where CC stands for clonal complex) and the MDR serotype 6C-CC386 in the pre- and post-PCV10/13 periods, respectively. Penicillin-non-susceptible pneumococci (PNSP) formed 24% and 38.9% of the pre- and post-PCV10/13 isolates, respectively (P = 0.01). In the pre-PCV10/13 period, serotype 14-ST156 was the predominant penicillin-non-susceptible lineage, but it was not detected in the post-PCV10/13 period. Serotype 14-ST156 and serotype 19A-ST320 complex isolates had the highest penicillin and ceftriaxone MICs in the pre- and post-PCV10/13 periods, respectively. In turn, serotype 6C-CC386 comprised almost 30% of the PNSP and over 40% of the erythromycin-resistant isolates (MIC >256 mg/L) in the post-PCV10/13 period.

Conclusions

Although PNSP strains were polyclonal, most resistant isolates belonged to a single genotype from each period. Higher erythromycin resistance prevalence (42%) in the post-PCV10/13 period was mainly attributed to MDR serotype 6C-CC386. Ongoing surveillance of pneumococcal clonal composition is important to evaluate PCV use outcomes and to identify factors other than PCVs that drive pneumococcal drug resistance evolution.

Relationship between immune response to pneumococcal conjugate vaccines in infants and indirect protection after vaccine implementation

Introduction: Streptococcus pneumoniae is a leading cause of morbidity and mortality worldwide. Widespread infant vaccination with pneumococcal conjugate vaccines (PCVs) substantially reduced vaccine-serotype pneumococcal disease by direct protection of immunized children and indirect protection of the community via decreased nasopharyngeal carriage and transmission. Essential to grasping the public health implications of pediatric PCV immunization is an understanding of how PCV formulations impact carriage. Areas covered: Using clinical evidence, this review examines how the immune response to PCVs is associated with subsequent nasopharyngeal carriage reduction in vaccinated infants and toddlers. By combining direct and indirect protection, carriage reduction results in a reduced spread of vaccine serotypes, and eventually, a decrease in vaccine serotype disease incidence in community members of all ages. Expert opinion: The current review presents some of the aspects that influence the overall impact of PCVs on vaccine-serotype carriage, and thus, spread. The link between reduction of vaccine-serotype carriage and the eventual reduction of vaccine-serotype disease in the wider community is described by comparing data from current PCVs, specifically with respect to their ability to reduce carriage of some cross-reacting serotypes (i.e. 6A versus 6B and 19A versus 19F).

The impact of childhood pneumococcal vaccination on hospital admissions in England: a whole population observational study

Background

Pneumococcal infections are major causes of morbidity and mortality worldwide. We use routine hospital admissions data and time-series modelling analysis to estimate the impact of the seven and thirteen valent pneumococcal conjugate vaccines (PCV7 and PCV13) on hospital admissions due to pneumococcal disease in England.

Methods

Hospital admissions for pneumococcal meningitis, bacteraemia and pneumonia between January 1, 2003 and December 31, 2015 were identified from the national Hospital Episode Statistics database for all age groups in England. We model the impact of pneumococcal vaccination using interrupted time series analysis. Hospital admissions prior to vaccine introduction were extrapolated to predict the expected number of admissions in the absence of pneumococcal vaccines. Admissions avoided over time were estimated by comparing the fitted interrupted time series and the expected model for no vaccination in a Bayesian framework.

Results

Overall, there were 43,531 (95% credible interval (CrI): 36486–51,346) fewer hospital admissions due to bacteraemia, meningitis and pneumonia in England during the period from 2006 to 2015 than would have been expected if pneumococcal vaccines had not been implemented, with the majority of hospital admissions avoided due to pneumonia. Among young children reductions in meningitis were more common, while among adults reductions in pneumonia admissions were relatively more important, with no evidence for reduced bacteraemia and meningitis among older adults. We estimated that 981 (95% CrI: 391–2018), 749 (95% CrI: 295–1442) and 1464 (95% CrI: 793–2522) bacteraemia, meningitis and pneumonia related hospital admissions, respectively, were averted in children < 2 years of age.

Conclusions

Substantial reductions in hospital admissions for bacteraemia, meningitis and pneumonia in England were estimated after the introduction of childhood vaccination, with indirect effects being responsible for most of the hospital admissions avoided.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4119-8) contains supplementary material, which is available to authorized users.

Synergy Between Two Chimeric Lysins to Kill Streptococcus pneumoniae

Phage lysins constitute a new generation of antimicrobials that are becoming a promising alternative and complementation to current antibiotic therapies, which are nowadays called into question by the increasing numbers of multiresistant bacteria. Streptococcus pneumoniae is a leading human pathogen causing serious infectious diseases in children and adults. Within the host-parasite interplay system of pneumococcus and its phages, several antipneumococcal lysins have been described and, among them, chimeric lysins Cpl-711 and PL3 stand out for their potent bactericidal activities. Here, evidence is presented on the synergistic cooperation of the catalytically diverse lysins Cpl-711 and PL3 in different assays, like purified cell wall enzymatic degradation, in vitro bacterial cell growth inhibition, and killing of both planktonic and biofilm grown cells. Synergy between Cpl-711 and PL3 has been shown to reduce the amount of enzyme necessary to inhibit growth in checkerboard assays with a sum of fractional inhibitory concentrations ≤0.5 for all pneumococcal strains tested, while also significatively increasing bactericidal effect by ≥2 logs with respect to the sum of activities of Cpl-711 and PL3 individual treatments. Moreover, the combination of these two lysins showed synergy in an adult zebrafish model of pneumococcal infection. This study consolidates the possibility of formulating highly efficient and synergistic antibacterial enzymes that could improve our ability to fight multiresistant bacterial infections.

Pneumococcal carriage in children in Ulaanbaatar, Mongolia before and one year after the introduction of the 13-valent pneumococcal conjugate vaccine

BACKGROUND

Nasopharyngeal carriage of Streptococcus pneumoniae precedes disease, is the source of pneumococcal community spread, and the mechanism for herd protection provided by pneumococcal conjugate vaccines (PCVs). There are few PCV impact studies in low- and middle-income countries, particularly in Asia. In 2016, Mongolia introduced the 13-valent PCV (PCV13) in a phased manner using a 2 + 1 schedule, with catch-up. We aimed to assess the impact of PCV13 introduction on nasopharyngeal pneumococcal carriage and density in children in Mongolia.

METHODS

We conducted two cross-sectional carriage surveys (pre- and one year post-PCV) at community health clinics in two districts of the capital city, Ulaanbaatar in both May-July 2015 and 2017. The study analysis included 961 children too young to be vaccinated (5-8 weeks old) and 989 children eligible for vaccination (12-23 months old). Pneumococci were detected by quantitative real-time PCR and molecular serotyping performed using DNA microarray.

FINDINGS

One year post-PCV introduction, PCV13 serotype carriage reduced by 52% in 12-23 month olds (adjusted prevalence ratio [aPR] 0.48 [95% confidence interval [CI] 0.39-0.59]), with evidence of non-PCV13 serotype replacement (aPR 1.55 [95% CI 1.30-1.85]), compared with the pre-PCV period. In 5-8 week olds, PCV13 serotype carriage reduced by 51% (aPR 0.49 [95% CI 0.33-0.73]) with no significant change in non-PCV13 serotype carriage (aPR 1.10 [95% CI 0.83-1.46]). An increase was observed in both PCV13 and non-PCV13 pneumococcal density post-PCV introduction. Antimicrobial resistance (AMR) genes were common, with 82.3% of samples containing at least one of the 10 AMR genes assessed.

CONCLUSION

This study demonstrates substantive PCV13 impact on pneumococcal carriage one year post-vaccine introduction in Mongolia. The reductions in PCV13 serotype carriage are likely to result in reductions in pneumococcal disease including indirect effects. Increases in non-PCV13 serotypes require further monitoring.

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.

Serotype distribution and antibiotic resistance among invasive Streptococcus pneumoniae from Oman post 13-valent vaccine introduction

OBJECTIVE

This study was undertaken to determine the serotype distribution and drug susceptibility patterns in pneumococcal isolates recovered from patients with invasive pneumococcal disease (IPD).

METHODS

All invasive pneumococcal isolates received between June 2014 and June 2016 were included in the study as part of a national laboratory-based IPD surveillance program. Isolates recovered from clinical specimens of normally sterile body sites were included.

RESULTS

A total of 41 different serotypes were identified among the 132 pneumococcal isolates included in this study. The most prevalent serotypes/serogroups were 12 (8.3%), 15 (8.3%), 19F (7.6%), 3 (6.1%), and 19A (6.1%);. It was observed that overall vaccine coverage rates for pneumococcal conjugate vaccines (PCV), PCV7, PCV10 and PCV13 were 15.9%, 24.2% and 37.1% respectively. 56.8% (n=75) of the isolates were non-susceptible to at least one antibiotic and 40.9% (n=54) of the isolates were resistant to PEN (M). 18.9% (n=25) of the isolates were multi-drug resistant (MDR).The case fatality rate was 15.9%.

CONCLUSION

Our study results call for broader vaccine coverage, emphasizes the need to introduce the conjugate pneumococcal vaccine for the high risk adult population and stress the importance of continuous surveillance of serotypes and antimicrobial resistance to guide vaccine development and antimicrobial stewardship activities.