Pneumococcal conjugate vaccination and nasopharyngeal acquisition of pneumococcal serotype 19A strains

Traditional Japanese herbal medicine Hochuekkito protects development of sepsis after nasal colonization in mice

INTRODUCTION

Streptococcus pneumoniae, a commensal in the nasopharynx, can cause invasive pneumococcal diseases (IPDs). To prevent the aggravation of IPDs, it is important to enhance host immune defense against S. pneumoniae. Hochuekkito (HET) is expected to have an immunostimulatory effect against infections.

METHODS

HET was administrated by gavage to adult BALB/cA mice before and after intranasal inoculation of S. pneumoniae. We evaluated the effect of HET on pneumococcal nasal colonization and subsequent development of lethal pneumococcal infections.

RESULTS

No effect on nasal colonization was observed, but HET significantly reduced bacterial count in the blood, decreased the incidence of bacteremia, and improved survival. HET also reduced nasal tissue damage 3 days after intranasal infection. Neutrophils from HET-treated mice showed significantly higher bactericidal activity against S. pneumoniae in the presence of the serum from the HET group compared with from the control group.

CONCLUSIONS

The non-specific immunostimulatory effect of HET is suggested by this study to be effective in preventing the progression in IPDs and provided insights into novel strategy in the post-pneumococcal vaccine era.

To the question of the relevance of the development and prospects for the use of the bacteriophage <i>Streptococcus pneumoniae</i>

Introduction. The prevalence of Streptococcus pneumoniae strains causing invasive forms of pneumococcal infection and the growing rates of antibiotic resistance of individual serotypes of the pathogen pose a number of urgent and socially significant tasks the search for new antimicrobial agents for prevention and treatment. Objective. To analyze the data of scientific publications of domestic and foreign authors on the problems of practical use and prospects for the development of the bacteriophage S. pneumoniae drug aimed at the actual serotypes of the pathogen. Results. Analysis of literary sources in scientific electronic databases and publishing houses eLibrary.Ru, ScienceDirect, Scopus, PubMed, Springerlink, Wiley Online Library, Annual reviews allowed us to summarize information about four isolated lytic bacteriophages of S. pneumoniae and their endolysins, as well as about two lysogenic phages, to present data on the clinical efficacy of streptococcal bacteriophage in pneumococcal infection in animals and humans. The results of search queries on the most significant and widespread serotypes of S. pneumoniae in the territory of the Russian Federation have established the predominance in the structure of variants 19F, 14, 9V/A, 15 A/F, 6 A/B/C/D, 3 and 23F. Some of them are characterized by a high level of antibiotic resistance and cause invasive forms of the disease, and serotypes 15 A/F/C, 6 C/D are not represented in modern vaccines, which increases the relevance of the development and use of pneumococcal bacteriophage, including intraspecific typing of significant and common serotypes. Conclusion. Based on the analysis of the current state of the issue of pneumococcal bacteriophages, the information obtained on the circulation of topical strains of S. pneumoniae on the territory of the Russian Federation and their serotype landscape, it is concluded that the development of the bacteriophage S. pneumoniae drug is relevant as a means of targeted action for the prevention, diagnosis and personalized therapy of human diseases of pneumococcal etiology.

Using genomics to examine the persistence of Streptococcus pneumoniae serotype 19A in Ireland and the emergence of a sub-clade associated with vaccine failures

BACKGROUND

Streptococcus pneumoniae serotype 19A remains a significant cause of invasive pneumococcal disease (IPD) in Ireland despite the successful introduction of a 13-valent pneumococcal conjugate vaccine (PCV13) in 2010 which reduced the overall incidence of IPD in children.

METHODS

Invasive Streptococcus pneumoniae serotype 19A isolates from the Irish reference laboratory between 2007-08 and 2017-18 were analysed using whole genome sequencing (WGS) to investigate the persistence of this vaccine-preventable serotype. We compared the entire national 19A collection to other international collections using a standardised nomenclature of Global Pneumococcal Sequencing Clusters (GPSC).

RESULTS

Expansion of GPSCs and clonal complexes (CCs) may have been associated with vaccine introduction and antimicrobial prescribing policies. A sub-clade of GPSC1-CC320 (n = 25) unique to Ireland, included five of the ten vaccine failures/breakthrough cases identified (p = 0.0086). This sub-clade was not observed in a global GPSC1-CC320 collection. All isolates within the sub-clade (n = 25) contained a galE gene variant rarely observed in a global pneumococcal collection (n = 37/13454, p < 0.001) nor within GPSC1-CC320 (n = 19/227) (p < 0.001). The sub-clade was estimated to have emerged at the start of the PCV-vaccine era (ancestral origin 2000, range 1995-2004) and expanded in Ireland, with most isolated after PCV13 introduction (n = 24/25).

CONCLUSIONS

The identification of a sub-clade/variant of serotype 19A highlights the benefit of using WGS to analyse genotypes associated with persistence of a preventable serotype of S. pneumoniae. Particularly as this sub-clade identified was more likely to be associated with IPD in vaccinated children than other 19A genotypes. It is possible that changes to the galE gene, which is involved in capsule production but outside of the capsular polysaccharide biosynthesis locus, may affect bacterial persistence within the population. Discrete changes associated with vaccine-serotype persistence should be further investigated and may inform vaccine strategies.

Impact and effectiveness of the 10-valent pneumococcal conjugate vaccine on invasive pneumococcal disease among children under 5 years of age in the Netherlands

BACKGROUND

In 2011, the 7-valent pneumococcal conjugate vaccine (PCV7) was replaced by the 10-valent vaccine (PCV10) in the Netherlands. We report on impact and effectiveness against invasive pneumococcal disease (IPD) in children aged under 5 years by switching from PCV7 to PCV10.

METHOD

We included IPD cases between 2004 and 2019 in children aged < 5 years reported via the national surveillance system. To assess the impact of the PCV10 vaccination program we compared IPD incidence 6-8 years after PCV10 introduction (2017-2019) to the two years just before the switch to PCV10 (2009-2011). We estimated vaccine effectiveness (VE) using the indirect cohort method, comparing vaccination status (at least two vaccine doses) in IPD-cases caused by PCV10 serotypes (cases) to non-PCV10 IPD cases (controls), in children eligible for PCV10.

RESULTS

The overall incidence decreased from 8.7 (n = 162) in 2009-2011 to 7.3 per 100.000 (n = 127) in 2017-2019 (Incidence rate ratio (IRR) 0.83, 95%CI: 0.66; 1.05). IPD caused by the additional serotypes included in PCV10 declined by 93% (IRR 0.07, 95%CI: 0.02; 0.23). Incidence of non-PCV10 IPD showed a non-significant increase (IRR 1.25, 95%CI: 0.96; 1.63). Among 231 IPD-cases eligible for PCV10, the overall VE was 91% (95%CI: 67; 97) and did not differ by sex or age at diagnosis. Effectiveness against non-PCV10 serotype 19A IPD was non-significant with an estimate of 28% (95%CI:-179; 81).

CONCLUSION

PCV10 is highly effective in protecting against IPD in Dutch children under 5 years with limited serotype replacement after switching from PCV7 to PCV10. We found no evidence for significant cross-protection of PCV10 against 19A serotype IPD.

Pneumococcal vaccination: Direct and herd effect on carriage of vaccine types and antibiotic resistance in Icelandic children

BACKGROUND

Since the introduction of pneumococcal conjugate vaccines, vaccine type pneumococcal carriage and disease has decreased world-wide. The aim was to monitor changes in the nasopharyngeal carriage of pneumococci, the distribution of serotypes and antimicrobial resistance in children before and after initiation of the 10-valent pneumococcal vaccination in 2011, in a previously unvaccinated population.

METHODS

Repeated cross-sectional study at 15day-care centres in greater Reykjavik area. Nasopharyngeal swabs were collected yearly in March from 2009 to 2015. The swabs were selectively cultured for pneumococci, which were serotyped using latex agglutination and/or PCR and antimicrobial susceptibility determined. Two independent studies were conducted. In study 1, on total impact, isolates from children aged <4years were included. The vaccine-eligible-cohort (birth-years: 2011-2013, sampled in 2013-2015) was compared with children at the same age born in 2005-2010 and sampled in 2009-2012. In study 2 on herd effect, isolates from older non-vaccine-eligible children (3.5-6.3years) were compared for the periods before and after the vaccination (2009-2011 vs 2013-2015. Vaccine impact was determined using 1-odds-ratio.

RESULTS

Following vaccination, the vaccine impact on vaccine type acquisition was 94% (95% CI: 91-96%) in study 1 and 56% (95% CI: 44-65%) in study 2. The impact on serotype 6A was 33% (95% CI: -9%; 59%) in study 1 and 42% (95% CI: 10-63%) in study 2 with minimal effect on 19A. The non-vaccine serotypes/groups 6C, 11, 15 and 23B were the most common serotypes/groups after vaccination. Isolates from the vaccine-eligible-cohort had lower penicillin MICs, less resistance to erythromycin and co-trimoxazole and less multi resistance than isolates from the control-group.

CONCLUSIONS

The efficacy of the vaccination on vaccine serotypes was high, and a milder effect on vaccine-associated-serotype 6A was observed for the vaccine-eligible-cohort. There was a significant herd effect on vaccine types in older non-vaccine-eligible children. Overall antimicrobial non-susceptibility was reduced.

Dynamics of nasopharyngeal pneumococcal carriage during the course of viral bronchiolitis

The effect of viral infection on nasopharyngeal carriage of Streptococcus pneumoniae during childhood is not well known. We studied dynamics of pneumococcal colonization by quantitative PCR during the natural course of viral bronchiolitis. At time of admission, 47 (47%) of 100 patients with bronchiolitis carried pneumococci. In patients with viral bronchiolitis who did not receive antibiotics, pneumococcal load decreased from time of admission to discharge (n = 35, cycle threshold 23 vs. 25, P = 0.0017) and from discharge to follow-up (n = 22, cycle threshold 25 vs. 40, P = 0.003). We conclude that viral respiratory infection is negatively associated with pneumococcal colonization of the upper airways. Pediatr Pulmonol. 2016;51:863-867. © 2016 Wiley Periodicals, Inc.

Direct, indirect and total effects of 13-valent pneumococcal conjugate vaccination on invasive pneumococcal disease in children in Navarra, Spain, 2001 to 2014: cohort and case–control study

We estimated the direct, indirect and total effects of the 13-valent pneumococcal conjugate vaccine (PCV13) on invasive pneumococcal disease (IPD) in children. A population-based cohort study followed children aged between 2.5 and 59 months between 2001 and 2014 in Navarra, Spain. IPD incidence was compared by PCV status and period. All cases diagnosed from July 2010 to December 2014 and eight matched controls per case were analysed to estimate the adjusted direct effect of PCV13. A total of 120,980 children were followed and 206 IPD cases were detected. Compared with unvaccinated children in the baseline period (2001–2004), overall IPD incidence in 2011–2014 (76% average PCV coverage) declined equally in vaccinated (total effect: 76%; hazard ratio (HR): 0.24; 95% confidence interval (CI): 0.14–0.40) and unvaccinated children (indirect effect: 78%; HR: 0.22; 95% CI: 0.09–0.55). IPD incidence from non-PCV13 serotypes increased among vaccinated children (HR: 2.84; 95% CI: 1.02–7.88). The direct effect of one or more doses of PCV13 against vaccine serotypes was 95% (odds ratio: 0.05; 95% CI: 0.01–0.55). PCV13 was highly effective in preventing vaccine-serotype IPD. The results suggest substantial and similar population-level vaccine benefits in vaccinated and unvaccinated children through strong total and indirect effects.

Invasive pneumococcal disease: Clinical outcomes and patient characteristics 2-6 years after introduction of 7-valent pneumococcal conjugate vaccine compared to the pre-vaccine period, the Netherlands

BACKGROUND

Implementation of 7-valent pneumococcal conjugate vaccine (PCV7) in the Dutch national immunization program for infants led to a shift from vaccine to non-vaccine serotypes in invasive pneumococcal disease (IPD) in all age groups. We studied the impact of the serotype shift on clinical syndromes and outcomes.

METHODS

Pneumococcal isolates from hospitalized IPD patients obtained from nine sentinel microbiology laboratories, covering 25% of the Dutch population, were serotyped. Clinical syndromes, outcomes and patient characteristics in the post-PCV7 (2008-2012) period were compared with the pre-PCV7 period (2004-2006). Serotype specific propensity of the association with empyema, meningitis and death was calculated.

RESULTS

Invasive pneumonia incidence significantly decreased in children <5 years and elderly ≥65 years, but increased in 5-64 years old from 4.92 to 5.58 cases/100.000/year (RR 1.13 95% CI 0.99-1.29). Empyema incidence significantly increased in elderly 65 years and older from 0.61 to 2.60 cases/100.000/year (RR 4.28 95% CI 1.97-9.33), mainly due to serotype 1. The incidence of meningitis only declined significantly in children <5 years. IPD case-fatality decreased in children <5 years from 5% to 3%, in 5-64 years old from 9% to 7% and in elderly ≥65 years significantly from 22% to 17%, due to lower case-fatality rates for most emerging non-PCV7 serotypes.

CONCLUSIONS

An increase in empyema incidence was observed in persons ≥65 years old in the post-PCV7 era, mainly due to the emergence of serotype 1, although overall IPD case-fatality decreased. Extended conjugate vaccines that target serotype 1 or serotypes with high case-fatality may offer further reduction of pneumococcal disease burden.

Nasopharyngeal carriage of Streptococcus pneumoniae and other bacteria in the 7th year after implementation of the pneumococcal conjugate vaccine in the Netherlands

After introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in the infant national immunization program (NIP) in the Netherlands in 2006, Streptococcus pneumoniae strains of the non-vaccine serotype 19A emerged and became the dominant serotype in carriage in children and their parents. Similar patterns were observed in other European countries and the United States. Increases in carriage rates of Staphylococcus aureus and non-typeable (NT) Haemophilus influenzae were also observed. After switching of PCV7 to 10-valent vaccine (PCV10) in 2011, a new carriage surveillance study was performed in the winter of 2012/2013. Nasopharyngeal carriage of S. pneumoniae, H. influenzae, S. aureus, and Moraxella catarrhalis was determined by conventional culture in 330 PCV10-vaccinated 11-month-old children, 330 PCV7-vaccinated 24-month-old children, and their parents. Carriage prevalence was compared with similar carriage studies conducted in 2005, 2009, and 2010/2011. Although serotype 19A remained the most frequently carried pneumococcal serotype in children, prevalence of 19A significantly declined in PCV7-vaccinated 24-month-old children (14% to 8%, p=0.01), but less in PCV10-vaccinated 11-month-old children (12% to 9%, p=0.31). Carriage of H. influenzae remained stable at an elevated level (65% in 11-month-olds and 69% in 24-month-olds), while the carriage of S. aureus returned to pre-PCV7 levels in 11-month-old children (14% in 2010/2011 to 7% in 2012/2013), but not in 24-month-olds (remained at 7%). Our results might indicate a new balance between replacing non-vaccine pneumococcal serotypes and other potential pathogenic bacteria in nasopharyngeal carriage. Carriage studies are valuable tools in assessing vaccine effects on pathogens circulating in the population, for evaluation of PCV impact, and in predicting changes in respiratory and invasive disease.

Effect on nasopharyngeal pneumococcal carriage of replacing PCV7 with PCV13 in the Expanded Programme of Immunization in The Gambia

INTRODUCTION

In 2011, two years after the introduction of 7-valent Pneumococcal conjugate vaccine (PCV7), the Gambian immunization programme replaced PVC7 with PCV13 (13-valent). Our objective was to assess the additional impact of PCV13 on prevalence of pneumococcal nasopharyngeal carriage.

METHODS

We recruited healthy Gambian infants who had received three PCV doses. Nasopharyngeal swabs were collected from infants and their mothers during two cross-sectional surveys (CSS) conducted in infants vaccinated with PCV7 (CSS1) and vaccinated with PCV13 (CSS2). Pneumococci were isolated and serotyped following standardized methods. Whole genome sequencing was performed on non-typable pneumococcus isolated in CSS1 and CSS2.

RESULTS

339 and 350 infants and their mothers were recruited in CSS1 and CSS2, respectively. Overall prevalence of pneumococcal carriage was 85.4% in infants. Among infants, prevalence of vaccine type (VT) carriage was lower in CSS2 [9.4% versus 4.9% (p=0.025) for PCV7-VT; 33.3% versus 18.3% (p<0.001) for PCV13-VT and 23.9% versus 13.7% (p=0.001) for the 6 additional serotypes included in PCV13]. At CSS2, there was a decrease of serotypes 6A (from 15.3% to 5.7%, p<0.001) and 19F (from 5.6% to 1.7%, p=0.007), and an increase of non-typable pneumococci (0.3-6.0%, p<0.001), most of which (82.4%) were from typable serotype backgrounds that had lost the ability to express a capsule. Prevalence of overall and VT carriage in mothers was similar in CSS1 and CSS2.

CONCLUSIONS

Replacing PCV7 for PCV13 rapidly decreased prevalence of VT carriage among vaccinated Gambian infants. An indirect effect in mothers was not observed yet. Vaccine-driven selection pressure may have been responsible for the increase of non-typable isolates.

Epidemiological analysis of pneumococcal serotype 19A in healthy children following PCV7 vaccination

After the introduction of conjugate vaccines, a strong rearrangement of pneumococcal serotypes was observed globally. Probably most concerning was the emergence of serotype 19A, which has not only high invasive disease potential, but also high antibiotic resistance. In the current study we focused on the increased prevalence of serotype 19A after the PCV vaccination rate became widely used in Hungary. A total of 2262 children aged 3-6 years were screened for pneumococcus carriage using nasal swabs. Children were divided into two groups according to the vaccination rates, low level (group 1) vs. high level (group 2). While the carriage rate did not change over time (average 32·9%), the serotype distribution differed greatly in the two groups. The prevalence of serotype 19A increased >eightfold. Almost all 19A isolates had high-level macrolide resistance and elevated penicillin minimum inhibitory concentrations. Genotyping methods revealed that these new 19A isolates are different from the previously frequent Hungary19A-6 PMEN clone. Both the carriage rate and the overall penicillin and macrolide resistance remained stable over time, but while several serotypes were represented in group 1, serotype 19A alone was clearly dominant in group 2.

Five winters of pneumococcal serotype replacement in UK carriage following PCV introduction

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PCV7 serotype replacement was near complete 5 years after PCV7 introduction.

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The carriage rate remained stable through out the 5 year period.

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Serotypes unique to PCV13 significantly decreased by the final winter.

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Clonal expansion of existing genotypes was primarily responsible for replacement.

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Continued surveillance is needed to monitor replacement until equilibrium is reached.

The seven-valent pneumococcal conjugate vaccine (PCV7) was added to the UK national immunisation programme in September 2006. PCV13 replaced PCV7 in April 2010. As carriage precedes disease cases this study collected carried pneumococci from children each winter from 2006/7 to 2010/11 over PCV introduction. Conventional microbiology and whole genome sequencing were utilised to characterise pneumococcal strains.

Overall prevalence of pneumococcal carriage remained stable. Vaccine serotypes (VT) decreased (p < 0.0001) with concomitant increases in non-vaccine serotypes (NVT). In winter 2010/11 only one isolate of PCV7 VT was observed (6B). PCV13 unique VTs decreased between winters immediately preceding and following PCV13 introduction (p = 0.04). Significant decreases for VTs 6B, 19F, 23F (PCV7) and 6A (PCV13) and increases for NVT 21, 23B, 33F and 35F were detected. The serotype replacement was accompanied by parallel changes in genotype prevalence for associated sequence types with clonal expansion contributing to replacement. By winter 2010/11, serotype coverage of PCV7 and PCV13 was 1% and 11% respectively.

VT replacement was observed for PCV7 and PCV13 serotypes. Conjugate vaccine design and use requires continuous monitoring and revision.

Radical serotype rearrangement of carried pneumococci in the first 3 years after intensive vaccination started in Hungary

Streptococcus pneumoniae is responsible for a significant amount of morbidity and mortality worldwide. Healthy carriers, mainly young children, are the most important sources of infections. In the current study, we aimed to determine the changes that have occurred since the introduction of PCV-7 in Hungary. Nasal specimens were collected from 1,022 healthy children aged 3-6 years attending day-care centres. After thorough identification, pneumococcal isolates were serotyped, and their antibiotic sensitivity was determined. The carriage rate was found to be 34.9%. A huge serotype rearrangement was detected compared to earlier results, with the previously leading serotype 14 having completely disappeared. Serotypes 11A, 35F, 19A, 6B, 15B, 3 and 38 were most prevalent, and 29 different types were identified in total. The PCV-7 types were responsible for 16.5% of all serotypes, and 36.0% are not covered by any pneumococcal vaccines. The isolates were sensitive to most tested antibiotics, except erythromycin (resistance was 21.6%). Only one penicillin-resistant strain was found. The newly and rapidly emerging non-vaccine serotypes are much more sensitive, except serotype 19A.

CONCLUSION

Due to PCV vaccination, a complete serotype arrangement occurred also in Hungary. The old "paediatric" serotypes were replaced by serotypes 11A, 35F, 19A, 6B, 15B, 3 and 38.

Acquisition of Streptococcus pneumoniae in South African children vaccinated with 7-valent pneumococcal conjugate vaccine at 6, 14 and 40 weeks of age

BACKGROUND

Seven-valent pneumococcal conjugate vaccine (PCV7) was introduced into the South African immunization program using 6, 14 and 40 weeks dosing schedule (2+1), with no catch-up in older children since April 2009. We investigated pneumococcal colonization acquisition in children who received this schedule and also compared it to historical cohorts of PCV-naïve children (n=123 in 2007) and children who received a 3+1 PCV7 schedule (n=124 in 2005/06).

METHODS

Two hundred and fifty children aged 6-12 weeks were enrolled from December 2009 to April 2010. Participants had nasopharyngeal swabs collected on eight occasions between enrolment and 2-years of age. Standard methods were undertaken for bacterial culture and Streptococcus pneumoniae were serotyped using the Quellung method. Pneumococcal and Staphylococcus aureus colonization in the present study was compared to colonization in two historical longitudinal cohorts.

RESULTS

S. pneumoniae was identified in 1081 (61.4%) of 1761 swabs collected in the current cohort. Pneumococcal colonization peaked at 41-weeks of age (76.8%) and decreased to 62.8% by 2-years of age (p=0.002); PCV7-serotype colonization decreased during the same period from 28.6% to 15.6% (p=0.001). Children from the current cohort compared to PCV-naïve children were less likely to be colonized by PCV7-serotypes from 40-weeks to 2-years of age and acquired PCV7-serotypes less frequently. No differences in overall pneumococcal, PCV7-serotype and non-PCV7-serotype colonization or new serotype acquisitions were detected comparing the current cohort to the historical cohort who received the 3+1 PCV7 schedule. Staphylococcus aureus colonization was similar in all three cohorts.

CONCLUSION

A 2+1 PCV7 schedule implemented in South Africa was temporally associated with reduced risk of vaccine-serotype colonization compared to historically unvaccinated children. Also, vaccine-serotype acquisition rate using the 2+1 schedule was similar to that in the 3+1 dosing cohort, suggesting that similar indirect protection against pneumococcal disease could be derived from either schedule in South Africa.

Seven-valent pneumococcal conjugate vaccine and nasopharyngeal microbiota in healthy children

Careful monitoring of vaccines against common bacterial colonizers is needed.

Seven-valent pneumococcal conjugate vaccine (PCV-7) is effective against vaccine serotype disease and carriage. Nevertheless, shifts in colonization and disease toward nonvaccine serotypes and other potential pathogens have been described. To understand the extent of these shifts, we analyzed nasopharyngeal microbial profiles of 97 PCV-7–vaccinated infants and 103 control infants participating in a randomized controlled trial in the Netherlands. PCV-7 immunization resulted in a temporary shift in microbial community composition and increased bacterial diversity. Immunization also resulted in decreased presence of the pneumococcal vaccine serotype and an increase in the relative abundance and presence of nonpneumococcal streptococci and anaerobic bacteria. Furthermore, the abundance of Haemophilus and Staphylococcus bacteria in vaccinees was increased over that in controls. This study illustrates the much broader effect of vaccination with PCV-7 on the microbial community than currently assumed, and highlights the need for careful monitoring when implementing vaccines directed against common colonizers.

Experience with pneumococcal polysaccharide conjugate vaccine (conjugated to CRM197 carrier protein) in children and adults

Streptococcus pneumoniae-related infections are a major cause of morbidity and mortality in people of all ages worldwide. Pneumococcal vaccine development started in 1911 with a whole cell vaccine and more recently multivalent plain polysaccharide and polysaccharide conjugate vaccines have been developed. The recent vaccines rely on capsular polysaccharide antigens to induce serotype-specific immune responses. We summarize here the presentations on pneumococcal polysaccharide conjugate vaccine (conjugated to CRM197 carrier protein) given during the integrated symposium organized and funded by Pfizer International Operations during the 22nd European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) 31 March to 3 April 2012, London, UK. A dramatic reduction in the incidence of invasive pneumococcal diseases (IPD) due to vaccine serotypes (VST-IPD) has been reported since the introduction of a hepta-valent pneumococcal conjugate vaccine (PCV7). An indirect (herd) effect has been demonstrated to be associated with PCV7 infant vaccination programmes, with many studies reporting reductions in VST-IPD in populations that are not eligible for PCV7 vaccination. Since 2010, a 13-valent pneumococcal conjugate vaccine (PCV13) has been introduced into national immunization programmes and results from early surveillance suggest that this vaccine also has an impact on the serotypes unique to PCV13, as well as continuing to protect against the PCV7 serotypes. Data from a passive surveillance system in Europe in 2009, for instance, showed that the highest incidence of IPD remains in those aged >65 years and in children <5 years. PCV13 has now been licensed for vaccination of adults >50 years based on safety and immunogenicity data; an efficacy trial is being conducted. Regardless of previous pneumococcal vaccination status, if the use of 23-valent polysaccharide is considered appropriate, it is recommended to give PCV13 first. Novel immunization strategies remain the only practical means to reduce significantly the remaining global mortality and morbidity due to S. pneumoniae in adults.

Pneumococcal serotype-specific antibodies persist through early childhood after infant immunization: follow-up from a randomized controlled trial

Background

In a previous UK multi-center randomized study 278 children received three doses of 7-valent (PCV-7) or 13-valent (PCV-13) pneumococcal conjugate vaccine at 2, 4 and 12 months of age. At 13 months of age, most of these children had pneumococcal serotype-specific IgG concentrations ≥0.35 µg/ml and opsonophagocytic assay (OPA) titers ≥8.

Methods

Children who had participated in the original study were enrolled again at 3.5 years of age. Persistence of immunity following infant immunization with either PCV-7 or PCV-13 and the immune response to a PCV-13 booster at pre-school age were investigated.

Results

In total, 108 children were followed-up to the age of 3.5 years and received a PCV-13 booster at this age. At least 76% of children who received PCV-7 or PCV-13 in infancy retained serotype-specific IgG concentrations ≥0.35 µg/ml against each of 5/7 shared serotypes. For serotypes 4 and 18C, persistence was lower at 22–42%. At least 71% of PCV-13 group participants had IgG concentrations ≥0.35 µg/ml against each of 4/6 of the additional PCV-13 serotypes; for serotypes 1 and 3 this proportion was 45% and 52%. In the PCV-7 group these percentages were significantly lower for serotypes 1, 5 and 7F. A pre-school PCV-13 booster was highly immunogenic and resulted in low rates of local and systemic adverse effects.

Conclusion

Despite some decline in antibody from 13 months of age, these data suggest that a majority of pre-school children maintain protective serotype-specific antibody concentrations following conjugate vaccination at 2, 4 and 12 months of age.

Trial Registration

ClinicalTrials.gov NCT01095471

Initial effects of the National PCV7 Childhood Immunization Program on adult invasive pneumococcal disease in Israel

Background

PCV7 was introduced as universal childhood vaccination in Israel in July 2009 and PCV13 in November 2010. Here we report data on adult invasive pneumococcal disease (IPD), two years post PCV7 implementation and before an expected effect of PCV13.

Methods

An ongoing nationwide active-surveillance (all 27 laboratories performing blood cultures in Israel), providing all blood & CSF S. pneumoniae isolates from persons >18 y was initiated in July 2009. Capture-recapture method assured reporting of >95% cases. All isolates were serotyped in one central laboratory. IPD outcome and medical history were recorded in 90%. Second year post PCV implementation is compared to the first year.

Results

During July 2009 to June 2011, 970 IPD cases were reported (annual incidence [/100,000] of 9.17 and 10.16 in the two consecutive years, respectively). Respective case fatality rates (CFRs) were 20% and 19.1%. Incidence of IPD and CFR increased with age and number of comorbidities. Incidence rate was significantly greater during the second winter, 7.79/100,000 vs. 6.14/100,000 in first winter, p = 0.004, with a non-significant decrease during summer months (3.02 to 2.48/100,000). The proportion of IPD cases due to PCV7-serotypes decreased from 27.5% to 13.1% (first to second year) (p<0.001). Yet, non-PCV13-strains increased from 32.7% to 40.2% (p = 0.017). The increase in non-PCV13-strains was highly significant in immunocompromised patients and to a lesser degree in non-immunocompromised at risk or in older patients (>64 y). Among younger/healthier patients serotype 5 was the major increasing serotype. Penicillin and ceftriaxone resistance decreased significantly in the second year.

Conclusions

While overall annual incidence of IPD did not change, the indirect effect of PCV7 vaccination was evident by the significant decrease in PCV7 serotypes across all age groups. Increase in non-VT13 strains was significant in immunocompromised patients. A longer follow-up is required to appreciate the full effect of infant vaccination on annual IPD.

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

Antibiotic resistance in Streptococcus pneumoniae is a major concern worldwide. However, it is unclear whether resistance is associated with only a few highly prevalent clones or numerous and diverse clones. We monitored 349 healthy children and obtained nasopharyngeal cultures at five time points coinciding with health check-ups (4, 7, 10, 18 and 36 months) between 2008 and 2012. A total of 497 S. pneumoniae isolates from 257 healthy children were characterized using capsular serotyping, multilocus sequence typing and antibiotic resistance genotyping (ermB, mefA/E and pbp mutations). Among these isolates, 25 serotypes and 66 sequence types (STs) were found, including 24 new STs with 11 new alleles. Although resistance was present in a variety of ST clones, most of the clones (57/66, 86.4 %) had one specific resistant or susceptible genotype. Of 233 phenotypically penicillin-non-susceptible isolates, 196 (84.1 %) belonged to only six clones, comprising ST906B, ST23619F, ST24223F, ST37876A, ST143723F and ST33823A and their variants. We concluded that drug-resistant S. pneumoniae is associated with a limited number of highly prevalent clones that are capable of adapting to the community setting. Furthermore, we analysed the capsular gene evolution in serogroup 6. The strain ST29246D was probably the result of recombination of a 3563 bp fragment of the capsule locus acquired by an ST29246C strain from an ST906B or ST29246B strain. Compared with previous studies, our results showed a different recombination site (wciN and wzx) and a different cps profile (8-7-11), indicating that serogroup 6 strains have multiple sites for cps recombination as a mechanism of vaccine escape.

Nasopharyngeal carriage of pneumococci four years after community-wide vaccination with PCV-7 in The Gambia: long-term evaluation of a cluster randomized trial

Background

A village-randomized trial of a seven-valent pneumococcal-conjugate-vaccine (PCV-7) conducted in rural Gambia showed a decrease of vaccine-type (VT) and a non-significant increase in non-vaccine-type (NVT) nasopharyngeal carriage of pneumococci two years after vaccination. Here, we report findings four years after vaccination.

Methods

PCV-7 was given to all children below 30 months of age enrolled in the trial and to those born during its course in all study villages. Villages were randomized (older children and adults) to receive PCV-7 (wholly vaccinated villages) or serogroup-C-meningococcal-conjugate-vaccine (partly vaccinated villages). Cross-sectional surveys (CSS) to collect nasopharyngeal swabs were conducted before and at various intervals after vaccination. Sixteen of these randomized villages (8 wholly vaccinated and 8 partly vaccinated) participated in a CSS conducted four years after vaccination started.

Results

Four years after vaccination, the prevalence of VT pneumococcal carriage was slightly higher in partly than in wholly vaccinated villages [6.4% versus 3.9% (p = 0.120)] compared to 24.4% in the pre-vaccination CSS (p<0.001). Prevalence of NVT four years after vaccination was similar between study groups [32.7% versus 29.8% (p = 0.392), respectively] compared to 51.1% in the pre-vaccination CSS (p<0.001). Four years after vaccination started, lower prevalence of serotype 6A was detected in wholly vaccinated than in partly vaccinated villages (1.6% versus 3.5%, p = 0.093) whilst the prevalence of serotype 19A was similar between groups (2.9% versus 2.5%, p = 0.779). The most prevalent serotype 19A clone was ST 847. The most prevalent serotype 6A clone before vaccination was ST3324 whilst after vaccination ST913 and ST1737 predominated. Fourteen out of 26 STs detected among the serotype 6A isolates were new while no new 19A serotype ST was found.

Conclusions

The decline in prevalence of VT pneumococci seen shortly after PCV-7 vaccination was sustained four years later with only a small difference between study arms. No significant serotype replacement was detected.

Trial Registration

ClinicalTrials.gov ISRCTN51695599

Microbiology of bacteria causing recurrent acute otitis media (AOM) and AOM treatment failure in young children in Spain: shifting pathogens in the post-pneumococcal conjugate vaccination era

OBJECTIVE

To prospectively identify the bacterial aetiology and antimicrobial susceptibility of problematic (recurrent and treatment failure) acute otitis media in Spanish children several years after the introduction of 7-valent pneumococcal conjugate vaccine.

METHODS

Tympanocentesis or careful sampling of spontaneous otorrhoea was performed on children aged 3 to <36 months with recurrent acute otitis media, acute otitis media treatment failure or unresolved acute otitis media.

RESULTS

105 acute otitis media episodes (77 sampled by tympanocentesis, 28 otorrhoea samples) were evaluated: 46 recurrent, 35 treatment failures, 24 unresolved acute otitis media. 74 episodes (70.4%) had at least one bacterium identified on culture: Streptococcus pneumoniae was identified in 21 episodes, Haemophilus influenzae (all non-typeable) in 44, Streptococcus pyogenes in 2, Moraxella catarrhalis in 2. No statistically significant difference in bacterial aetiology by episode type was detected. Non-typeable H. influenzae was the most commonly isolated pathogen in all acute otitis media types and in all age sub-groups. Forty percent of S. pneumoniae isolates were multi-drug resistant. Pneumococcal serotype 19A was the most frequently identified serotype (7/21 episodes). Multi-drug resistance was found in 56% of 19A isolates. Of non-typeable H. influenzae isolates, 15% were ampicillin resistant and 13% were amoxicillin/clavulanate resistant. S. pneumoniae and non-typeable H. influenzae DNA were each detected in 57% of samples culture negative for these pathogens, including 12 co-infections.

CONCLUSION

Combining culture and polymerase chain reaction results, H. influenzae and S. pneumoniae may be implicated in 70% and 43% of clinically problematic bacterial acute otitis media episodes, respectively. The impact of new vaccines to prevent both S. pneumoniae and non-typeable H. influenzae acute otitis media may be substantial in this population and is worth investigating.

Distribution of carried pneumococcal clones in UK children following the introduction of the 7-valent pneumococcal conjugate vaccine: a 3-year cross-sectional population based analysis

The success of Streptococcus pneumoniae (pneumococcus) in both colonisation and disease is associated with the increased prevalence of genetic clones expressing virulence factors that assist host invasion. We studied the distribution of pneumococcal clones in paediatric carriage as part of an ongoing longitudinal study of pneumococcal carriage in children less than 5 years of age. Across three years, 87 different sequence types (STs) were found amongst 310 pneumococci. A decline in PCV-7 related STs was observed during the study period. STs 62, 199, 433 and 1692 increased after the implementation of PCV-7 and were related to increases in serotypes 11A, 19A, 22F, and to serotype 6C, respectively. Overall, a strong correlation was observed between ST and serotype. Thirteen STs contained multiple serotypes and 74 STs were associated with only one serotype. On-going molecular epidemiological surveillance of pneumococcal carriage is warranted during the implementation of pneumococcal conjugate vaccines.

Changes in serotype prevalence and antimicrobial resistance among invasive Streptococcus pneumoniae isolates in Korea, 1996-2008

We investigated changes in serotypes and antimicrobial susceptibilities among 386 isolates of invasive Streptococcus pneumoniae collected from numerous hospitals in Korea from 1996 to 2008. Serotypes 19F (9.8 %), 23F (8.3 %), 19A (7.8 %), 6A (7.5 %), 3 (7.3 %), 9V (6.5 %), 6B (6.2 %), 14 (4.9 %), 1 (3.9 %), 11A (3.9 %) and 4 (3.1 %) represented 69.2 % of all isolates. While the overall proportion of PCV7 serotypes was stable over time, we observed modest decreases in children <5 years old and in adults ≥65 years old between 1996-1999 and 2007-2008. An increased prevalence of non-PCV7 serotypes in these age groups was primarily attributable to an increase in serotypes 3, 6A and 19A. Most invasive S. pneumoniae isolates showed high resistance rates to erythromycin (74.9 %), tetracycline (71.1 %) and clindamycin (61.7 %). Between 1996-2003 and 2004-2008, non-susceptibility rates to cefotaxime and multi-drugs (three or more classes) in PCV7 serotypes showed a declining trend, while in non-PCV7 serotypes there was an increasing trend. Non-PCV7 serotypes 6A and 19A, which mostly exhibited multidrug-resistant phenotypes (69.0 % and 76.7 % respectively), increased between 1996-2003 and 2004-2008. Although PCV7 was introduced in Korea in November 2003, pneumococcal vaccination has not been included in the national child vaccination programme. Our results provide details of serotype occurrence that will be useful when adoption of universal pneumococcal vaccination in Korea is being considered.

Invasive pneumococcal disease and 7-valent pneumococcal conjugate vaccine, the Netherlands

Disease incidence and case fatality rates declined 4 years after introduction of the vaccine.

Expansion and evolution of Streptococcus pneumoniae serotype 19A ST320 clone as compared to its ancestral clone, Taiwan19F-14 (ST236)

BACKGROUND

The Streptococcus pneumoniae serotype 19A sequence type (ST) 320 clone, derived from an international Taiwan(19F)-14 (ST236) clone, has become prevalent in many countries.

METHODS

The dynamics of invasive pneumococcal disease (IPD) were determined using the database of the National Notifiable Disease Surveillance System in Taiwan. The virulence of 19A ST320 and Taiwan(19F)-14 (ST236) were assessed in mice. By constructing an isogenic serotype 19F variant of the 19A ST320 strain (19F ST320), we analyzed the role of capsular type and genetic background on the difference in virulence between 19A ST320 and Taiwan(19F)-14 (ST236).

RESULTS

Between 2008 and 2011, IPD due to serotype 19A increased from 2.1 to 10.2 cases per 100 000 population (P < .001); IPD due to any serotype also significantly increased (P = .01). Most serotype 19A isolates belonged to ST320. Using competition experiments in a murine model of colonization, we demonstrated that 19A ST320 outcompeted Taiwan(19F)-14 (ST236; competitive index, 20.3; P = .001). 19F ST320 was 2-fold less competitive than the 19A ST320 parent (competitive index, 0.47; P = .04) but remained 14-fold more competitive than Taiwan(19F)-14 (ST236; competitive index, 14.7; P < .001).

CONCLUSIONS

Genetic evolution of pneumococcal clones from Taiwan(19F)-14 (ST236) to 19A ST320 has made this pneumococcus better able to colonize of the nasopharynx. This evolution reflects not only a switch in capsular serotype but also changes in other loci.

Epidemiology of serotype 19A isolates from invasive pneumococcal disease in German children

BACKGROUND

This study presents an analysis of 159 serotype 19A isolates from IPD in children before and after the general recommendation for childhood pneumococcal conjugate vaccination in Germany in July 2006. Vaccination formulations used were PCV7, PCV10 (from April 2009) and PCV13 (from Dec. 2009, replacing PCV7).

METHODS

Isolates from invasive pneumococcal disease in children were serotyped using the Quellung reaction, tested for antibiotic susceptibility and analysed for their multi locus sequence type.

RESULTS

In an analysis of 3328 isolates from invasive pneumococcal disease (IPD) in children that were sent to the German National Reference Center for Streptococci between July 1997 and June 2011, we show that the proportion of 19A isolates ranged between 1.7 and 4.2% in the period 1997 to 2006. After the recommendation for pneumococcal conjugate childhood vaccination, which was issued in July 2006, the proportion of 19A isolates increased significantly to 15.0% in 2010/11. Eight clonal complexes (CC) and groups accounted for 77.2% and 65.3% of all serotype 19A isolates before and after vaccination, respectively. While three CCs and several STs were not detected after vaccine introduction, four CCs and several STs first appeared after vaccination, including three ST320 isolates that could be traced to recent imports from the US, UK and India. The proportion of penicillin-nonsusceptible and of multidrug-resistant 19A isolates moderately increased after vaccine introduction. A significant increase in the use of cephalosporins and azithromycin was noted post-vaccination (p=0.00001 and p=0.0013 respectively).

CONCLUSIONS

The prevalence of serotype 19A in Germany has increased significantly between July 2007 and June 2011. Possible reasons for this are the introduction of pneumococcal conjugate vaccination, increased use of cephalosporins and azithromycin, import of multidrug-resistant isolates and increased reporting.

Multivariate approach for studying interactions between environmental variables and microbial communities

To understand the role of human microbiota in health and disease, we need to study effects of environmental and other epidemiological variables on the composition of microbial communities. The composition of a microbial community may depend on multiple factors simultaneously. Therefore we need multivariate methods for detecting, analyzing and visualizing the interactions between environmental variables and microbial communities. We provide two different approaches for multivariate analysis of these complex combined datasets: (i) We select variables that correlate with overall microbiota composition and microbiota members that correlate with the metadata using canonical correlation analysis, determine independency of the observed correlations in a multivariate regression analysis, and visualize the effect size and direction of the observed correlations using heatmaps; (ii) We select variables and microbiota members using univariate or bivariate regression analysis, followed by multivariate regression analysis, and visualize the effect size and direction of the observed correlations using heatmaps. We illustrate the results of both approaches using a dataset containing respiratory microbiota composition and accompanying metadata. The two different approaches provide slightly different results; with approach (i) using canonical correlation analysis to select determinants and microbiota members detecting fewer and stronger correlations only and approach (ii) using univariate or bivariate analyses to select determinants and microbiota members detecting a similar but broader pattern of correlations. The proposed approaches both detect and visualize independent correlations between multiple environmental variables and members of the microbial community. Depending on the size of the datasets and the hypothesis tested one can select the method of preference.

Laboratory surveillance of invasive pneumococcal disease in New South Wales, Australia, before and after introduction of 7-valent conjugate vaccine: reduced disease, but not antibiotic resistance rates

We compared serotype distributions of Streptococcus pneumoniae isolates from patients aged <5 and o5 years with invasive pneumococcal disease in New South Wales, Australia, and antibiotic susceptibilities of isolates from the <5 years age group only, before (2002–2004) and after(2005–2009) introduction of the 7-valent pneumococcal conjugate vaccine (PCV7). Overall, there were significant decreases in the mean annual number of referred isolates (770 vs. 515) and the proportion belonging to PCV7 serotypes (74% vs. 38%), but non-PCV7 serotypes, particularly 19A, increased (5% vs. 18%). All changes were more marked in the <5 years age group.Susceptibility testing of isolates from the <5 years age group showed variation in resistance between serotypes, but significant overall increases in penicillin non-susceptibility (23% vs. 31%),ceftriaxone resistance (2% vs. 12%) and multidrug resistance (4% vs. 7%) rates ; erythromycin resistance fell (32% vs. 25%). Continued surveillance is needed to monitor changes following the introduction of 13-valent PCV in 2012.

Nasal carriage of Streptococcus pneumoniae serotypes and Staphylococcus aureus in Streptococcus pneumoniae-vaccinated and non-vaccinated young children

Since the implementation of Streptococcus pneumoniae (SPn) conjugate vaccination (PCV), non-vaccine types have prevailed in invasive pneumococcal disease (IPD), and an increase in Staphylococcus aureus (SA) burden has been suggested. Here, we assess the epidemiology of SA and SPn nasal carriage in 620 children at day-care centres; 141 of these children had received 1-4 PCV7 doses. A higher vaccine dosage was associated with non-vaccine-type SPn carriage. Of all SPn isolates, 45% were PCV7 types, 1% were additional PCV10 types and 22% were the three additional PCV13 types. SA carriage was inversely associated with vaccine-type SPn carriage. SPn serotype 19A showed higher SA co-carriage rates compared to other SPn serotypes. PCV7 implementation does not prevent children from being part of the IPD-related SPn transmission chain. These results contribute to the monitoring of SA- and SPn-related disease and add to the debate on the current national vaccination policy that recently included a change from PCV7 to PCV10.

Impact of pneumococcal vaccination in Denmark during the first 3 years after PCV introduction in the childhood immunization programme

BACKGROUND AND AIMS

The 7-valent pneumococcal conjugate vaccine (PCV7) was introduced in Denmark in October 2007 in a 2+1 schedule with a catch-up programme for children up to 17 months of age. To assess the impact of PCV we evaluated on the whole population: (1) direct and indirect effects on incidence of invasive pneumococcal disease (IPD), (2) changes in pneumococcal serotype distribution and (3) IPD related mortality.

METHODS

We compared disease incidence in pre-PCV (years 2000-2007) and PCV periods (years 2008-2010) based on national surveillance data.

RESULTS

In children aged 0-5 years the overall incidence of IPD decreased from 26.7 to 16.3 cases per 100,000 (IRR 0.58; 95% Confidence Interval (CI) [0.48-0.69]) and case fatality declined from 1.8% (12 deaths) in the eight-year pre-PCV period to 0% (no deaths) in the three-year PCV period. In the whole population the overall incidence of IPD and of IPD caused by vaccine serotypes declined significantly from 19.5 to 17.7 and from 7.7 to 3.8 cases per 100,000 persons comparing the two periods. The incidence of IPD due to non-vaccine serotypes (NVT-IPD) increased significantly from 11.8 to 13.9 cases per 100,000 in the whole population (incidence rate ratio 1.18; 95% CI [1.12-1.24]) with predominance of the serotypes 1.7F and 19A.

CONCLUSIONS

We report a marked decline in incidence in IPD in both vaccinated and non-vaccinated age groups and a minor but statistically significant increase in incidence of IPD due to NVTs in both vaccinated and non-vaccinated groups with predominance of serotypes covered by higher valence pneumococcal conjugate vaccines.

Virulence of Streptococcus pneumoniae serotype 6C in experimental otitis media

Increases in colonization with serotypes of Streptococcus pneumoniae not contained within the 7-valent pneumococcal conjugate vaccine (PCV) have been reported among children following introduction. Serotype 6C has emerged as prevalent in nasopharyngeal colonization and acute otitis media (AOM), though it is uncommonly recovered from children with invasive pneumococcal disease. Vaccine serotypes within PCV7 have been replaced by nonvaccine serotypes without significant changes in the overall carriage rate. We hypothesize 1) that serotypes vary in their ability to evade host defenses and establish AOM following colonization and 2) the observed reduction in pneumococcal otitis results from a reduced disease potential by some 'replacement serotypes'. We compared the capacity of S. pneumoniae serotypes 6C and 19A to produce experimental otitis media (EOM) in a chinchilla model. The proportion of chinchillas that developed culture positive EOM and density of middle ear infection was evaluated. EOM was found in 28/82 (34%) ears challenged with 6C compared to 13/18(72.2%) with 19A [p = 0.0003]. When disease due to 6C did occur, it was characterized by low-density infection. Our findings demonstrate that challenge with serotype 6C results in EOM less frequently than 19A. These data support the need for greater knowledge regarding differences among serotypes to produce AOM.

Pneumococcal carriage and antibiotic resistance in young children before 13-valent conjugate vaccine

BACKGROUND

We sought to measure trends in Streptococcus pneumoniae carriage and antibiotic resistance in young children in Massachusetts communities after widespread adoption of heptavalent 7-valent pneumococcal conjugate vaccine (PCV7) and before the introduction of the 13-valent PCV (PCV13).

METHODS

We conducted a cross-sectional study including collection of questionnaire data and nasopharyngeal specimens among children aged <7 years in primary care practices from 8 Massachusetts communities during the winter season of 2008-2009 and compared with similar studies performed in 2001, 2003-2004, and 2006-2007. Antimicrobial susceptibility testing and serotyping were performed on pneumococcal isolates, and risk factors for colonization in recent seasons (2006-2007 and 2008-2009) were evaluated.

RESULTS

We collected nasopharyngeal specimens from 1011 children, 290 (29%) of whom were colonized with pneumococcus. Non-PCV7 serotypes accounted for 98% of pneumococcal isolates, most commonly 19A (14%), 6C (11%), and 15B/C (11%). In 2008-2009, newly targeted PCV13 serotypes accounted for 20% of carriage isolates and 41% of penicillin-nonsusceptible S. pneumoniae. In multivariate models, younger age, child care, young siblings, and upper respiratory illness remained predictors of pneumococcal carriage, despite near-complete serotype replacement. Only young age and child care were significantly associated with penicillin-nonsusceptible S. pneumoniae carriage.

CONCLUSIONS

Serotype replacement post-PCV7 is essentially complete and has been sustained in young children, with the relatively virulent 19A being the most common serotype. Predictors of carriage remained similar despite serotype replacement. PCV13 may reduce 19A and decrease antibiotic-resistant strains, but monitoring for new serotype replacement is warranted.

Contribution of vaccines to our understanding of pneumococcal disease

Pneumonia is the leading cause of mortality in children in developing countries and is also the leading infectious cause of death in adults. The most important cause of pneumonia is the Gram-positive bacterial pathogen, Streptococcus pneumoniae, also known as the pneumococcus. It has thus become the leading vaccine-preventable cause of death and is a successful and diverse human pathogen. The development of conjugate pneumococcal vaccines has made possible the prevention of pneumococcal disease in infants, but has also elucidated aspects of pneumococcal biology in a number of ways. Use of the vaccine as a probe has increased our understanding of the burden of pneumococcal disease in children globally. Vaccination has also elucidated the clinical spectrum of vaccine-preventable pneumococcal infections; the identification of a biological niche for multiple pneumococcal serotypes in carriage and the differential invasiveness of pneumococcal serotypes; the impact of pneumococcal transmission among children on disease burden in adults; the role of carriage as a precursor to pneumonia; the plasticity of a naturally transformable pathogen to respond to selective pressure through capsular switching and the accumulation of antibiotic-resistance determinants; and the role of pneumococcal infections in hospitalization and mortality associated with respiratory viral infections, including both seasonal and pandemic influenza. Finally, there has been a recent demonstration that pneumococcal pneumonia in children may be an important cause of hospitalization for those with underlying tuberculosis.

Whole genome analysis of linezolid resistance in Streptococcus pneumoniae reveals resistance and compensatory mutations

BACKGROUND

Several mutations were present in the genome of Streptococcus pneumoniae linezolid-resistant strains but the role of several of these mutations had not been experimentally tested. To analyze the role of these mutations, we reconstituted resistance by serial whole genome transformation of a novel resistant isolate into two strains with sensitive background. We sequenced the parent mutant and two independent transformants exhibiting similar minimum inhibitory concentration to linezolid.

RESULTS

Comparative genomic analyses revealed that transformants acquired G2576T transversions in every gene copy of 23S rRNA and that the number of altered copies correlated with the level of linezolid resistance and cross-resistance to florfenicol and chloramphenicol. One of the transformants also acquired a mutation present in the parent mutant leading to the overexpression of an ABC transporter (spr1021). The acquisition of these mutations conferred a fitness cost however, which was further enhanced by the acquisition of a mutation in a RNA methyltransferase implicated in resistance. Interestingly, the fitness of the transformants could be restored in part by the acquisition of altered copies of the L3 and L16 ribosomal proteins and by mutations leading to the overexpression of the spr1887 ABC transporter that were present in the original linezolid-resistant mutant.

CONCLUSIONS

Our results demonstrate the usefulness of whole genome approaches at detecting major determinants of resistance as well as compensatory mutations that alleviate the fitness cost associated with resistance.

Effects of community-wide vaccination with PCV-7 on pneumococcal nasopharyngeal carriage in the Gambia: a cluster-randomized trial

BACKGROUND

Introduction of pneumococcal conjugate vaccines (PCVs) of limited valency is justified in Africa by the high burden of pneumococcal disease. Long-term beneficial effects of PCVs may be countered by serotype replacement. We aimed to determine the impact of PCV-7 vaccination on pneumococcal carriage in rural Gambia.

METHODS AND FINDINGS

A cluster-randomized (by village) trial of the impact of PCV-7 on pneumococcal nasopharyngeal carriage was conducted in 21 Gambian villages between December 2003 to June 2008 (5,441 inhabitants in 2006). Analysis was complemented with data obtained before vaccination. Because efficacy of PCV-9 in young Gambian children had been shown, it was considered unethical not to give PCV-7 to young children in all of the study villages. PCV-7 was given to children below 30 mo of age and to those born during the trial in all study villages. Villages were randomized (older children and adults) to receive one dose of PCV-7 (11 vaccinated villages) or meningococcal serogroup C conjugate vaccine (10 control villages). Cross-sectional surveys (CSSs) to collect nasopharyngeal swabs were conducted before vaccination (2,094 samples in the baseline CSS), and 4-6, 12, and 22 mo after vaccination (1,168, 1,210, and 446 samples in CSS-1, -2, and -3, respectively). A time trend analysis showed a marked fall in the prevalence of vaccine-type pneumococcal carriage in all age groups following vaccination (from 23.7% and 26.8% in the baseline CSS to 7.1% and 8.5% in CSS-1, in vaccinated and control villages, respectively). The prevalence of vaccine-type pneumococcal carriage was lower in vaccinated than in control villages among older children (5 y to <15 y of age) and adults (≥15 y of age) at CSS-2 (odds ratio [OR] = 0.15 [95% CI 0.04-0.57] and OR = 0.32 [95% CI 0.10-0.98], respectively) and at CSS-3 (OR = 0.37 [95% CI 0.15-0.90] for older children, and 0% versus 7.6% for adults in vaccinated and control villages, respectively). Differences in the prevalence of non-vaccine-type pneumococcal carriage between vaccinated and control villages were small.

CONCLUSIONS

Vaccination of Gambian children reduced vaccine-type pneumococcal carriage across all age groups, indicating a "herd effect" in non-vaccinated older children and adults. No significant serotype replacement was detected. Please see later in the article for the Editors' Summary.

Sequence diversity within the capsular genes of Streptococcus pneumoniae serogroup 6 and 19

The main virulence factor of Streptococcus pneumoniae is the capsule. The polysaccharides comprising this capsule are encoded by approximately 15 genes and differences in these genes result in different serotypes. The aim of this study was to investigate the sequence diversity of the capsular genes of serotypes 6A, 6B, 6C, 19A and 19F and to explore a possible effect of vaccination on variation and distribution of these serotypes in the Netherlands. The complete capsular gene locus was sequenced for 25 serogroup 6 and for 20 serogroup 19 isolates. If one or more genes varied in 10 or more base pairs from the reference sequence, it was designated as a capsular subtype. Allele-specific PCRs and specific gene sequencing of highly variable capsular genes were performed on 184 serogroup 6 and 195 serogroup 19 isolates to identify capsular subtypes. This revealed the presence of 6, 3 and a single capsular subtype within serotypes 6A, 6B and 6C, respectively. The serotype 19A and 19F isolates comprised 3 and 4 capsular subtypes, respectively. For serogroup 6, the genetic background, as determined by multi locus sequence typing (MLST) and multiple- locus variable number of tandem repeat analysis (MLVA), seemed to be closely related to the capsular subtypes, but this was less pronounced for serogroup 19 isolates. The data also suggest shifts in the occurrence of capsular subtypes within serotype 6A and 19A after introduction of the 7-valent pneumococcal vaccine. The shifts within these non-vaccine serotypes might indicate that these capsular subtypes are filling the niche of the vaccine serotypes. In conclusion, there is considerable DNA sequence variation of the capsular genes within pneumococcal serogroup 6 and 19. Such changes may result in altered polysaccharides or in strains that produce more capsular polysaccharides. Consequently, these altered capsules may be less sensitive for vaccine induced immunity.

Serotype distribution and antibiotic resistance of 140 pneumococcal isolates from pediatric patients with upper respiratory infections in Beijing, 2010

In the present study, the serotype distribution and antibiotic resistance of S. pneumoniae from pediatric patients with upper respiratory infections in Beijing, 2010 were described. 140 pneumococcal isolates were obtained, and the prevailing five serotypes were 19F (18.6%), 23F (9.3%), 14 (9.3%), 15 (9.3%), and 6A (7.1%). The vaccine coverage of PCV7, PCV10, and PCV13 were 43.6%, 43.6%, and 60.0%, respectively. According to the CLSI 2010 criteria, 99.3% of the S. pneumoniae isolates were susceptible to penicillin. The resistance rates to erythromycin and azithromycin were 96.4% and 97.1%, respectively. Meanwhile, 64.3% (90/140) of all pneumococcal isolates were multidrug-resistant S. pneumoniae (MDRSP). PCV13 covered 68.9% (62/90) of MDRSP strains, whereas it was 47.8% (43/90) for PCV7. ErmB was the dominant macrolide-resistance gene, whereas 30.4% pneumococcal isolates expressed both ermB and mefA. No isolate expressed ermTR. The potential coverage of PCV13 is higher than PCV7 and PCV10 because high rates of serotypes 6A and 19A, and the conjugate vaccines could prevent the spread of MDRSP. S. pneumoniae is still sensitive to penicillin. The resistance rate of S. pneumoniae to macrolides is high and ermB is the dominant macrolide-resistance gene in China, so continued surveillance of the antimicrobial susceptibility of S. pneumoniae may be necessary.

Update on childhood and adolescent immunizations: selected review of US recommendations and literature: part 1

PURPOSE OF REVIEW

To provide a clinically relevant synopsis of research findings regarding childhood and adolescent vaccines.

RECENT FINDINGS

Much research confirms the safety, immunogenicity, and efficacy of specific vaccines as well as the positive impact on overall morbidity and mortality. Prevention and control strategies involve the expansion of vaccine recommendations to include more individuals and/or more vaccine doses. In addition, the role of universal infant vaccination, the advantages of even partial immunization, and the documented benefits of recently introduced vaccines are explored. The material in this review includes important areas of clinical practice improvement, such as awareness of interim recommendations or monitoring of vaccine failures. Literature on hepatitis B, rotavirus, Haemophilus influenzae type b conjugate, and pneumococcal vaccines is included in this first of two articles.

SUMMARY

New research on childhood and adolescent vaccines is anticipated to shape the practice of pediatric providers. Research will continue to provide the science to optimize protection and to promote the health and well being of all children and adolescents.

Carriage of Streptococcus pneumoniae 3 years after start of vaccination program, the Netherlands

To evaluate the effectiveness of the 7-valent pneumococcal conjugate vaccine (PCV7) program, we conducted a cross-sectional observational study on nasopharyngeal carriage of Streptococcus pneumoniae 3 years after implementation of the program in the Netherlands. We compared pneumococcal serotypes in 329 prebooster 11-month-old children, 330 fully vaccinated 24-month-old children, and 324 parents with age-matched pre-PCV7 (unvaccinated) controls (ages 12 and 24 months, n = 319 and n = 321, respectively) and 296 of their parents. PCV7 serotype prevalences before and after PCV7 implementation, respectively, were 38% and 8% among 11-month-old children, 36% and 4% among 24-month-old children, and 8% and 1% among parents. Non-PCV7 serotype prevalences were 29% and 39% among 11-month-old children, 30% and 45% among 24-month-old children, and 8% and 15% among parents, respectively; serotypes 11A and 19A were most frequently isolated. PCV7 serotypes were largely replaced by non-PCV7 serotypes. Disappearance of PCV7 serotypes in parents suggests strong transmission reduction through vaccination.

Effect of seven-valent pneumococcal conjugate vaccine on Staphylococcus aureus colonisation in a randomised controlled trial

BACKGROUND

Heptavalent pneumococcal conjugate vaccine (PCV7) shifts nasopharyngeal colonisation with vaccine serotype pneumococci towards nonvaccine serotypes. Because of the reported negative association of vaccine serotype pneumococci and Staphylococcus aureus in the nasopharynx, we explored the effect of PCV7 on nasopharyngeal colonisation with S. aureus in children and parents.

METHODOLOGY/PRINCIPAL FINDINGS

This study was part of a randomised controlled trial on the effect of PCV7 on pneumococcal carriage, enrolling healthy newborns who were randomly assigned (1:1:1) to receive PCV7 (1) at 2 and 4 months of age (2) at 2, 4 and 11 months or (3) no PCV7 (controls). Nasopharyngeal colonisation of S. aureus was a planned secondary outcome. Nasopharyngeal swabs were obtained from all children over a 2-year period with 6-months interval and from one parent at the child's age of 12 and 24 months and cultured for Streptococcus pneumoniae and S. aureus. Between July 2005 and February 2006, 1005 children were enrolled and received either 2-doses of PCV7 (n = 336), 2+1-doses (336) or no dose (n = 333) before PCV7 implementation in the Dutch national immunization program. S. aureus colonisation had doubled in children in the 2+1-dose group at 12 months of age compared with unvaccinated controls (10.1% versus 5.0%; p = 0.019). A negative association for co-colonisation of S. pneumoniae and S. aureus was observed for both vaccine serotype (adjusted odds ratio (aOR) 0.53, 95% confidence interval (CI) 0.38-0.74) and nonvaccine serotype pneumococci (aOR 0.67, 95% CI 0.52-0.88).

CONCLUSIONS/SIGNIFICANCE

PCV7 induces a temporary increase in S. aureus colonisation in children around 12 months of age after a 2+1-dose PCV7 schedule. The potential clinical consequences are unknown and monitoring is warranted.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00189020.