What is different about serotype 1 pneumococci?

Emerging pneumococcal serotypes in Iraq: scope for improved vaccine development

Pneumococcal disease is a global public health concern as it affects the young, aged and the immunocompromised. The development of pneumococcal vaccines and their incorporation in the immunization programs has helped to reduce the global burden of disease. However, serotype replacement and the emergence of non-vaccine serotypes as well as the persistence of a few vaccine serotypes underscores the need for development of new and effective vaccines against such pneumococcal serotypes. In the Middle East, places of religious mass gatherings are a hotspot for disease transmission in addition to the global risk factors. Therefore, the periodic surveillance of pneumococcal serotypes circulating in the region to determine the effectiveness of existing prevention strategies and develop improved vaccines is warranted. Currently, there is a lack of serotype prevalence data for Iraq due to inadequate surveillance in the region. Thus, this review aims to determine the pneumococcal serotypes circulating in Iraq which may help in the development and introduction of improved pneumococcal vaccines in the country.

Nasopharyngeal carriage of Streptococcus pneumoniae serotypes among sick and healthy children in northern India: A case-control study

BACKGROUND

Streptococcus pneumoniae is leading bacterial cause of community acquired pneumonia and according to World Health Organization, responsible for 14 % death in children. There is effective vaccine available against Streptococcus pneumoniae. Hence the primary objective was to isolate Streptococcus pneumoniae from nasopharyngeal swabs in children aged 2-59 months with and without community acquired pneumonia and to assess their serotypes.

METHODS

This case-control study was conducted in tertiary teaching institutes in northern India. Hospitalized children, aged 2-59 months, with World Health Organization-defined community acquired pneumonia were included as cases. Age matched healthy controls were recruited from immunization clinic. All enrolments were done after written informed parental consent. Nasopharyngeal swabs were taken from both cases and controls, and were cultured on 5 % sheep blood agar with gentamycin plate for growth of Streptococcus pneumoniae and incubated in a jar at 370 for 18-24 hrs. Quellung reaction test was used for serotyping.

RESULTS

From March 2017 to December 2022, 2693 children (1910 cases and 783 controls), were recruited. The median age of cases was 7 months and controls 10 months. Almost all the cases had received antibiotics prior to hospitalization. Streptococcus pneumoniae positivity in nasopharyngeal swab was 8.1 % in cases, of which 56.8 % were vaccine serotypes and 23.6 % in controls, of which 37.8 % were vaccine serotypes. Adjusted odds ratio of isolating vaccine serotypes among cases as compared to controls was 1.77 (95 % CI, 1.09-2.88).

CONCLUSION

Streptococcus pneumoniae isolation from nasopharyngeal was found to be in lower proportion in cases as compared to control, though colonization with vaccine serotypes was higher in cases as compared to control. Therefore, pneumococcal vaccine coverage must be increased to prevent community acquired pneumonia.

Serotype 1 pneumococcus: epidemiology, genomics, and disease mechanisms

Streptococcus pneumoniae (the 'pneumococcus') is a significant cause of morbidity and mortality worldwide, causing life-threatening diseases such as pneumonia, bacteraemia, and meningitis, with an annual death burden of over one million. Discovered over a century ago, pneumococcal serotype 1 (S1) is a significant cause of these life-threatening diseases. Our understanding of the epidemiology and biology of pneumococcal S1 has significantly improved over the past two decades, informing the development of preventative and surveillance strategies. However, many questions remain unanswered. Here, we review the current state of knowledge of pneumococcal S1, with a special emphasis on clinical epidemiology, genomics, and disease mechanisms.

Comparative Genomics of Disease and Carriage Serotype 1 Pneumococci

The isolation of Streptococcus pneumoniae serotypes in systemic tissues of patients with invasive disease versus the nasopharynx of healthy individuals with asymptomatic carriage varies widely. Some serotypes are hyper-invasive, particularly serotype 1, but the underlying genetics remain poorly understood due to the rarity of carriage isolates, reducing the power of comparison with invasive isolates. Here, we use a well-controlled genome-wide association study to search for genetic variation associated with invasiveness of serotype 1 pneumococci from a serotype 1 endemic setting in Africa. We found no consensus evidence that certain genomic variation is overrepresented among isolates from patients with invasive disease than asymptomatic carriage. Overall, the genomic variation explained negligible phenotypic variability, suggesting a minimal effect on the disease status. Furthermore, changes in lineage distribution were seen with lineages replacing each other over time, highlighting the importance of continued pathogen surveillance. Our findings suggest that the hyper-invasiveness is an intrinsic property of the serotype 1 strains, not specific for a "disease-associated" subpopulation disproportionately harboring unique genomic variation.

Changes in Invasive Pneumococcal Disease Caused by Streptococcus pneumoniae Serotype 1 Following Introduction of PCV10 and PCV13: Findings from the PSERENADE Project

Streptococcus pneumoniae serotype 1 (ST1) was an important cause of invasive pneumococcal disease (IPD) globally before the introduction of pneumococcal conjugate vaccines (PCVs) containing ST1 antigen. The Pneumococcal Serotype Replacement and Distribution Estimation (PSERENADE) project gathered ST1 IPD surveillance data from sites globally and aimed to estimate PCV10/13 impact on ST1 IPD incidence. We estimated ST1 IPD incidence rate ratios (IRRs) comparing the pre-PCV10/13 period to each post-PCV10/13 year by site using a Bayesian multi-level, mixed-effects Poisson regression and all-site IRRs using a linear mixed-effects regression (N = 45 sites). Following PCV10/13 introduction, the incidence rate (IR) of ST1 IPD declined among all ages. After six years of PCV10/13 use, the all-site IRR was 0.05 (95% credibility interval 0.04–0.06) for all ages, 0.05 (0.04–0.05) for <5 years of age, 0.08 (0.06–0.09) for 5–17 years, 0.06 (0.05–0.08) for 18–49 years, 0.06 (0.05–0.07) for 50–64 years, and 0.05 (0.04–0.06) for ≥65 years. PCV10/13 use in infant immunization programs was followed by a 95% reduction in ST1 IPD in all ages after approximately 6 years. Limited data availability from the highest ST1 disease burden countries using a 3 + 0 schedule constrains generalizability and data from these settings are needed.

Pneumococcal nasopharyngeal carriage among Bhutanese children hospitalized with clinical pneumonia: serotypes and viral co-infection

BACKGROUND

Pneumococcal nasopharyngeal colonization (PNC) generally precedes pneumococcal disease. The purpose of this study was to determine the prevalence of PNC and to identify the pneumococcal serotypes circulating among Bhutanese children under five years of age admitted with clinical pneumonia, before the introduction of pneumococcal conjugate vaccine (PCV13) in the country. We also aimed to contribute to the understanding of the interplay between PNC and viral co-infection among this population.

METHODS

This was a prospective study conducted at the Jigme Dorji Wangchuck National Referral Hospital in Bhutan over 12 consecutive months. Children aged 2 to 59 months admitted with WHO-defined clinical pneumonia were eligible for recruitment. We collected blood for bacterial culture and molecular identification of S. pneumoniae, and nasopharyngeal washing for screening of respiratory viruses, and for the detection and capsular typing of S. pneumoniae by real-time polymerase chain reaction (RT-PCR).

RESULTS

Overall, 189 children were recruited, and PNC was tested in 121 of them (64.0%). PNC was found in 76/121 children (62.8%) and S. pneumoniae was identified in blood (both by culture and RT-PCR) in a single child. Respiratory viruses were detected in a similar proportion among children with (62/70; 88.6%) and without PNC (36/40; 90.0%; p = 1.000), but rhinovirus detection was less common among children with PNC (20/70; 28.6% versus 19/40; 47.5%; p = 0.046). Capsular typing identified 30 different serotypes. Thirty-nine children (51.3%) were colonised with two to five different serotypes. A third of the children presented with serotypes considered highly invasive. Over half of the children (44/76; 57.9%) were carrying at least one serotype included in PCV13.

CONCLUSIONS

This study provides baseline information on the status of PNC among Bhutanese children admitted with clinical pneumonia prior to the introduction of PCV13, which is valuable to monitor its potential impact. PCV13 could theoretically have averted up to 58% of the pneumococcal infections among the children in this study, suggesting a future role for the vaccine to significantly reduce the burden associated with S. pneumoniae in Bhutan.

Lower Density and Shorter Duration of Nasopharyngeal Carriage by Pneumococcal Serotype 1 (ST217) May Explain Its Increased Invasiveness over Other Serotypes

Streptococcus pneumoniae is a frequent colonizer of the human nasopharynx and a major cause of life-threating invasive infections such as pneumonia, meningitis and sepsis. Over 1 million people die every year due to invasive pneumococcal disease (IPD), mainly in developing countries. Serotype 1 is a common cause of IPD; however, unlike other serotypes, it is rarely found in the carrier state in the nasopharynx, which is often considered a prerequisite for disease. The aim of this study was to understand this dichotomy. We used murine models of carriage and IPD to characterize the pathogenesis of African serotype 1 (sequence type 217) pneumococcal strains obtained from the Queen Elizabeth Central Hospital in Blantyre, Malawi. We found that ST217 pneumococcal strains were highly virulent in a mouse model of invasive pneumonia, but in contrast to the generally accepted assumption, can also successfully establish nasopharyngeal carriage. Interestingly, we found that cocolonizing serotypes may proliferate in the presence of serotype 1, suggesting that acquisition of serotype 1 carriage could increase the risk of developing IPD by other serotypes. RNA sequencing analysis confirmed that key virulence genes associated with inflammation and tissue invasiveness were upregulated in serotype 1. These data reveal important new insights into serotype 1 pathogenesis, with implications for carriage potential and risk of invasive disease through interactions with other cocolonizing serotypes, an often-overlooked factor in transmission and disease progression.IMPORTANCE The pneumococcus causes serious diseases such as pneumonia, sepsis, and meningitis and is a major cause of morbidity and mortality worldwide. Serotype 1 accounts for the majority of invasive pneumococcal disease cases in sub-Saharan Africa but is rarely found during nasopharyngeal carriage. Understanding the mechanisms leading to nasopharyngeal carriage and invasive disease by this serotype can help reduce its burden on health care systems worldwide. In this study, we also uncovered the potential impact of serotype 1 on disease progression of other coinfecting serotypes, which can have important implications for vaccine efficacy. Understanding the interactions between different serotypes during nasopharyngeal carriage may lead to improved intervention methods and therapies to reduce pneumococcal invasive disease levels.

Structural insights into loss of function of a pore forming toxin and its role in pneumococcal adaptation to an intracellular lifestyle

The opportunistic pathogen Streptococcus pneumoniae has dual lifestyles: one of an asymptomatic colonizer in the human nasopharynx and the other of a deadly pathogen invading sterile host compartments. The latter triggers an overwhelming inflammatory response, partly driven via pore forming activity of the cholesterol dependent cytolysin (CDC), pneumolysin. Although pneumolysin-induced inflammation drives person-to-person transmission from nasopharynx, the primary reservoir for pneumococcus, it also contributes to high mortality rates, creating a bottleneck that hampers widespread bacterial dissemination, thus acting as a double-edged sword. Serotype 1 ST306, a widespread pneumococcal clone, harbours a non-hemolytic variant of pneumolysin (Ply-NH). Performing crystal structure analysis of Ply-NH, we identified Y150H and T172I as key substitutions responsible for loss of its pore forming activity. We uncovered a novel inter-molecular cation-π interaction, governing formation of the transmembrane β-hairpins (TMH) in the pore state of Ply, which can be extended to other CDCs. H150 in Ply-NH disrupts this interaction, while I172 provides structural rigidity to domain-3, through hydrophobic interactions, inhibiting TMH formation. Loss of pore forming activity enabled improved cellular invasion and autophagy evasion, promoting an atypical intracellular lifestyle for pneumococcus, a finding that was corroborated in in vivo infection models. Attenuation of inflammatory responses and tissue damage promoted tolerance of Ply-NH-expressing pneumococcus in the lower respiratory tract. Adoption of this altered lifestyle may be necessary for ST306 due to its limited nasopharyngeal carriage, with Ply-NH, aided partly by loss of its pore forming ability, facilitating a benign association of SPN in an alternative, intracellular host niche.

Hypervirulent pneumococcal serotype 1 harbours two pneumolysin variants with differential haemolytic activity

Streptococcus pneumoniae is a devastating global pathogen. Prevalent in sub-Saharan Africa, pneumococcal serotype 1 is atypical in that it is rarely found as a nasopharyngeal coloniser, yet is described as one of the most common causes of invasive pneumococcal disease. Clonal sequence type (ST)-306 and ST615 are representative of the two major serotype 1 lineages A and C, respectively. Here we investigated the virulence properties and haemolytic activities of these 2 clonal types using in vivo mouse models and in vitro assays. A lethal dose of ST615 administered intranasally to mice led to the rapid onset of disease symptoms and resulted in 90% mortality. In contrast, mice exposed to the same infection dose of ST306 or a pneumolysin (Ply)-deficient ST615 failed to develop any disease symptoms. Interestingly, the 2 strains did not differ in their ability to bind the immune complement or to undergo neutrophil-mediated phagocytosis. Upon comparative genomic analysis, we found higher within-ST sequence diversity in ST615 compared with ST306 and determined that ZmpA, ZmpD proteins, and IgA protease, were uniquely found in ST615. Using cell fractionation and cell contact-dependent assay, we made the unexpected finding that ST615 harbours the expression of two haemolytic variants of Ply: a cell-wall restricted fully haemolytic Ply, and a cytosolic pool of Ply void of any detectable haemolytic activity. This is the first time such a phenomenon has been described. We discuss the biological significance of our observation in relation to the aptitude of the pneumococcus for sustaining its human reservoir.

Bacterial genome-wide association study of hyper-virulent pneumococcal serotype 1 identifies genetic variation associated with neurotropism

Hyper-virulent Streptococcus pneumoniae serotype 1 strains are endemic in Sub-Saharan Africa and frequently cause lethal meningitis outbreaks. It remains unknown whether genetic variation in serotype 1 strains modulates tropism into cerebrospinal fluid to cause central nervous system (CNS) infections, particularly meningitis. Here, we address this question through a large-scale linear mixed model genome-wide association study of 909 African pneumococcal serotype 1 isolates collected from CNS and non-CNS human samples. By controlling for host age, geography, and strain population structure, we identify genome-wide statistically significant genotype-phenotype associations in surface-exposed choline-binding (P = 5.00 × 10-08) and helicase proteins (P = 1.32 × 10-06) important for invasion, immune evasion and pneumococcal tropism to CNS. The small effect sizes and negligible heritability indicated that causation of CNS infection requires multiple genetic and other factors reflecting a complex and polygenic aetiology. Our findings suggest that certain pathogen genetic variation modulate pneumococcal survival and tropism to CNS tissue, and therefore, virulence for meningitis.

Genomic Characteristics of Invasive Streptococcus pneumoniae Serotype 1 in New Caledonia Prior to the Introduction of PCV13

Streptococcus pneumoniae serotype 1 is a common cause of global invasive pneumococcal disease. In New Caledonia, serotype 1 is the most prevalent serotype and led to two major outbreaks reported in the 2000s. The pneumococcal conjugate vaccine 13 (PCV13) was introduced into the vaccination routine, intending to prevent the expansion of serotype 1 in New Caledonia. Aiming to provide a baseline for monitoring the post-PCV13 changes, we performed a whole-genome sequence analysis on 67 serotype 1 isolates collected prior to the PCV13 introduction. To highlight the S. pneumoniae serotype 1 population structure, we performed a multilocus sequence typing (MLST) analysis revealing that NC serotype 1 consisted of 2 sequence types: ST3717 and the highly dominant ST306. Both sequence types harbored the same resistance genes to beta-lactams, macrolide, streptogramin B, fluoroquinolone, and lincosamide antibiotics. We have also identified 36 virulence genes that were ubiquitous to all the isolates. Among these virulence genes, the pneumolysin sequence presented an allelic profile associated with disease outbreaks and reduced hemolytic activity. Moreover, recombination hotspots were identified in 4 virulence genes and more notably in the cps locus (cps2L), potentially leading to capsular switching, a major mechanism of the emergence of nonvaccine types. In summary, this study represents the first overview of the genomic characteristics of S. pneumoniae serotype 1 in New Caledonia prior to the introduction of PCV13. This preliminary description represents a baseline to assess the impact of PCV13 on serotype 1 population structure and genomic diversity.

Gastrointestinal symptoms in invasive pneumococcal disease: a cohort study

Background

The study aimed to assess whether gastrointestinal (GI) symptoms at admission are associated with increased short-term mortality in patients with invasive pneumococcal disease (IPD).

Methods

We included all patients with IPD at Aker University Hospital in Oslo, Norway, from 1993 to 2008. Clinical data were registered. Survival data were retrieved from official registries. We used Cox regression and Kaplan-Meier curve to compare mortality within 28 days of admission in patients with and without GI symptoms.

Results

Four hundred sixteen patients were included. Of these, 108 patients (26%) presented with GI symptoms, and 47 patients (11%) with GI symptoms only. Patients with GI symptoms were younger (p < 0.001) and had less cardiovascular disease (p < 0.001), pulmonary disease (p = 0.048), and cancer (p = 0.035) and received appropriate antibiotic treatment later. After adjusting for risk factors, we found an increased hazard ratio of 2.28 (95% CI 1.31–3.97) in patients presenting with GI symptoms. In patients with GI symptoms only there was an increased hazard ratio of 2.24 (95% CI 1.20–4.19) in univariate analysis, which increased to 4.20 (95% CI 2.11–8.39) after multivariate adjustment. Fewer patients with GI symptoms only received antibiotics upon admission.

Conclusions

A large proportion of IPD patients present with GI symptoms only or in combination with other symptoms. GI symptoms in IPD are associated with increased short-term mortality.

Characterization of pneumococcal meningitis before and after introduction of 13-valent pneumococcal conjugate vaccine in Niger, 2010-2018

Pneumococcal meningitis in the African meningitis belt is primarily caused by Streptococcus pneumoniae serotype 1, a serotype contained in the 13-valent pneumococcal conjugate vaccine (PCV13). In 2014, Niger introduced PCV13 with doses given at 6, 10, and 14 weeks of age. We leveraged existing meningitis surveillance data to describe pneumococcal meningitis trends in Niger. As a national reference laboratory for meningitis, Centre de Recherche Médicale et Sanitaire (CERMES) receives cerebrospinal fluid specimens from suspected bacterial meningitis cases and performs confirmatory testing for an etiology by culture or polymerase chain reaction (PCR). Specimens with S. pneumoniae detection during 2010-2018 were sent to the Centers for Disease Control and Prevention for serotyping by sequential triplex real-time PCR. Specimens that were non-typeable by real-time PCR underwent serotyping by conventional multiplex PCR. We tested differences in the distribution of pneumococcal serotypes before (2010-2012) and after (2016-2018) PCV13 introduction. During January 2010 to December 2018, CERMES received 16,155 specimens; 5,651 (35%) had bacterial etiology confirmed. S. pneumoniae accounted for 13.2% (744/5,651); 53.1% (395/744) were serotyped. During 2010-12, PCV13-associated serotypes (VT) constituted three-fourths of serotyped pneumococcus-positive specimens; this proportion declined in all age groups in 2016-18, most substantially in children aged < 5 years (74.0% to 28.1%; P < 0.05). Among persons aged ≥ 5 years, VT constituted > 50% of pneumococcal meningitis after PCV13 introduction; serotype 1 remained the most common VT among persons aged ≥ 5 years, but not among those < 5 years. VT as a group caused a smaller proportion of reported pneumococcal meningitis cases after PCV13 introduction in Niger. Serotype 1, however, remains the major cause of pneumococcal meningitis in older children and adults. Different vaccination strategies, such as changing the infant vaccination schedule or extending vaccine coverage to older children and adults, are needed, in addition to stronger surveillance.

Increased pathogenicity of pneumococcal serotype 1 is driven by rapid autolysis and release of pneumolysin

Streptococcus pneumoniae serotype 1 is the predominant cause of invasive pneumococcal disease in sub-Saharan Africa, but the mechanism behind its increased invasiveness is not well understood. Here, we use mouse models of lung infection to identify virulence factors associated with severe bacteraemic pneumonia during serotype-1 (ST217) infection. We use BALB/c mice, which are highly resistant to pneumococcal pneumonia when infected with other serotypes. However, we observe 100% mortality and high levels of bacteraemia within 24 hours when BALB/c mice are intranasally infected with ST217. Serotype 1 produces large quantities of pneumolysin, which is rapidly released due to high levels of bacterial autolysis. This leads to substantial levels of cellular cytotoxicity and breakdown of tight junctions between cells, allowing a route for rapid bacterial dissemination from the respiratory tract into the blood. Thus, our results offer an explanation for the increased invasiveness of serotype 1.

The mechanisms behind the high invasiveness of Streptococcus pneumoniae serotype 1 are unclear. Here, Jacques et al. show that this feature is due to overproduction and rapid release of pneumolysin, which induces cytotoxicity and breakdown of tight junctions, allowing rapid bacterial dissemination from the respiratory tract into the blood.

Development of Next Generation Streptococcus pneumoniae Vaccines Conferring Broad Protection

Streptococcus pneumoniae is a major pathogen causing pneumonia with over 2 million deaths annually, especially in young children and the elderly. To date, at least 98 different pneumococcal capsular serotypes have been identified. Currently, the vaccines for prevention of S. pneumoniae infections are the 23-valent pneumococcal polysaccharide-based vaccine (PPV23) and the pneumococcal conjugate vaccines (PCV10 and PCV13). These vaccines only cover some pneumococcal serotypes and are unable to protect against non-vaccine serotypes and unencapsulated S. pneumoniae. This has led to a rapid increase in antibiotic-resistant non-vaccine serotypes. Hence, there is an urgent need to develop new, effective, and affordable pneumococcal vaccines, which could cover a wide range of serotypes. This review discusses the new approaches to develop effective vaccines with broad serotype coverage as well as recent development of promising pneumococcal vaccines in clinical trials. New vaccine candidates are the inactivated whole-cell vaccine strain (Δpep27ΔcomD mutant) constructed by mutations of specific genes and several protein-based S. pneumoniae vaccines using conserved pneumococcal antigens, such as lipoprotein and surface-exposed protein (PspA). Among the vaccines in Phase 3 clinical trials are the pneumococcal conjugate vaccines, PCV-15 (V114) and 20vPnC. The inactivated whole-cell and several protein-based vaccines are either in Phase 1 or 2 trials. Furthermore, the recent progress of nanoparticles that play important roles as delivery systems and adjuvants to improve the performance, as well as the immunogenicity of the nanovaccines, are reviewed.

Construction of a pneumolysin deficient mutant in streptococcus pneumoniae serotype 1 strain 519/43 and phenotypic characterisation

Streptococcus pneumoniae capsular serotype 1 continues to pose a huge infectious disease burden in low- and middle-income countries, particularly in West Africa. However, studies on this important serotype have been hampered by the inability to genetically modify these strains. In this study we have genetically modified a serotype 1 strain (519/43), the first time that this has been achieved for this serotype, providing the methodology for a deeper understanding of its biology and pathogenicity. As proof of principle we constructed a defined pneumolysin mutant and showed that it lost its ability to lyse red blood cells. We also showed that when mice were infected intranasally with the mutant 519/43Δply there was no significant difference between the load of bacteria in lungs and blood when compared to the wild type 519/43. When mice were infected intraperitoneally there were significantly fewer bacteria recovered from blood for the mutant 519/43Δply strain, although all mice still displayed signs of disease. Our study demonstrates S. pneumoniae serotype 1 strains can be genetically manipulated using our methodology and demonstrate that the ability to cause pneumonia in mice is independent of active pneumolysin for the 519/43 serotype 1 strain.

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Mutagenesis in Serotype 1 S. pneumoniae is possible in strain 519/43.

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519/43 possess pneumolysin D380 N, however it is not more haemolytic than the pneumolysin present in D39.

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519/43 strain is capable of causing disease independently of pneumolysin.

Pneumococcal carriage and serotype distribution among children with and without pneumonia in Mozambique, 2014-2016

Background

Pneumococcal colonization is a precursor to pneumonia, and pneumococcal conjugate vaccines (PCV) can decrease vaccine-type (VT) colonization. Pneumococcal colonization studies are traditionally done among healthy children in the community; however, VT colonization prevalence may differ between these children and those with pneumonia. We assessed overall and VT pneumococcal colonization and factors associated with colonization among children with and without pneumonia after Mozambique introduced 10-valent PCV (PCV10) in 2013.

Methods

We used data from ongoing pneumonia surveillance in children aged <5 years and from cross-sectional nasopharyngeal colonization surveys conducted in October 2014 –April 2015 and October 2015 –May 2016. Pneumonia was defined using WHO standard criteria for radiologically confirmed pneumonia. Children with pneumonia enrolled from January 2014 –April 2016 were compared to children without pneumonia enrolled from the cross-sectional surveys. Clinical data and nasopharyngeal (NP) swabs were collected from each child. NP specimens were cultured for pneumococci, and culture-negative specimens from children with pneumonia underwent polymerase chain reaction (PCR).

Results

Of 778 and 927 children with and without pneumonia, 97.4% and 27.0% were exposed to antibiotics before swab collection, respectively. Based on culture, pneumococcal colonization was 45.1% for children with and 84.5% for children without pneumonia (P<0.001); VT pneumococcal colonization was 18.6% for children with and 23.4% for children without pneumonia (P = 0.02). The addition of PCR in children with pneumonia increased overall and VT-pneumococcal colonization to 79.2% and 31.1%, respectively. In multivariable analysis including PCR results, pneumonia was associated with VT pneumococcal colonization (adjusted OR: 1.4, 95%CI: 1.10–1.78).

Conclusion

Vaccine-type pneumococcal colonization remains common among children with and without pneumonia post-PCV10 introduction in Mozambique. In a population of children with high antibiotic exposure, the use of PCR for culture-negative NP swabs can improve assessment of pneumococcal colonization and circulating serotypes.

A model for predicting bacteremia in patients with community-acquired pneumococcal pneumonia: a retrospective observational study

Background

Pneumococcal pneumonia causes high morbidity and mortality among adults. This study aimed to identify risk factors for bacteremic pneumococcal pneumonia, and to construct a prediction model for the development of bacteremia in patients with community-acquired pneumococcal pneumonia.

Methods

We retrospectively analyzed data from patients hospitalized with community-acquired pneumococcal pneumonia between April 2007 and August 2015. Logistic regression models were applied to detect risk factors for pneumococcal bacteremia, and a receiver operating characteristic curve was used to devise a prediction model.

Results

Based on the results of sputum cultures, urine antigen tests, and/or blood cultures, 389 patients were diagnosed with pneumococcal pneumonia, 46 of whom had bacteremia. In the multivariate analysis, age < 65 years, serum albumin level < 3.0 g/dL, need for intensive respiratory or vasopressor support (IRVS), and C-reactive protein level > 20 mg/dL were identified as independent risk factors for the development of pneumococcal bacteremia. The bacteremia prediction score based on receiver operating characteristic curve analysis had a sensitivity of 0.74 and a specificity of 0.78 in patients with two risk factors. The area under the receiver operating characteristic curve was 0.77 (95% confidence interval (CI), 0.70–0.85).

Conclusions

Age < 65 years, hypoalbuminemia, IRVS, and high C-reactive protein level on admission are independent risk factors for the development of bacteremia in patients with community-acquired pneumococcal pneumonia. A prediction model based on these four risk factors could help to identify patients with community-acquired pneumococcal pneumonia at high risk of developing bacteremia; this can be used to guide antibiotic choices.

Trial registration

UMIN-CTR UMIN 000004353. Registered 7 October 2010. Retrospectively registered.

Population genetic structure, antibiotic resistance, capsule switching and evolution of invasive pneumococci before conjugate vaccination in Malawi

INTRODUCTION

Pneumococcal infections cause a high death toll in Sub Saharan Africa (SSA) but the recently rolled out pneumococcal conjugate vaccines (PCV) will reduce the disease burden. To better understand the population impact of these vaccines, comprehensive analysis of large collections of pneumococcal isolates sampled prior to vaccination is required. Here we present a population genomic study of the invasive pneumococcal isolates sampled before the implementation of PCV13 in Malawi.

MATERIALS AND METHODS

We retrospectively sampled and whole genome sequenced 585 invasive isolates from 2004 to 2010. We determine the pneumococcal population genetic structure and assessed serotype prevalence, antibiotic resistance rates, and the occurrence of serotype switching.

RESULTS

Population structure analysis revealed 22 genetically distinct sequence clusters (SCs), which consisted of closely related isolates. Serotype 1 (ST217), a vaccine-associated serotype in clade SC2, showed highest prevalence (19.3%), and was associated with the highest MDR rate (81.9%) followed by serotype 12F, a non-vaccine serotype in clade SC10 with an MDR rate of 57.9%. Prevalence of serotypes was stable prior to vaccination although there was an increase in the PMEN19 clone, serotype 5 ST289, in clade SC1 in 2010 suggesting a potential undetected local outbreak. Coalescent analysis revealed recent emergence of the SCs and there was evidence of natural capsule switching in the absence of vaccine induced selection pressure. Furthermore, majority of the highly prevalent capsule-switched isolates were associated with acquisition of vaccine-targeted capsules.

CONCLUSIONS

This study provides descriptions of capsule-switched serotypes and serotypes with potential to cause serotype replacement post-vaccination such as 12F. Continued surveillance is critical to monitor these serotypes and antibiotic resistance in order to design better infection prevention and control measures such as inclusion of emerging replacement serotypes in future conjugate vaccines.

Pneumolysin as a potential therapeutic target in severe pneumococcal disease

Acute pulmonary and cardiac injury remain significant causes of morbidity and mortality in those afflicted with severe pneumococcal disease, with the risk for early mortality often persisting several years beyond clinical recovery. Although remaining to be firmly established in the clinical setting, a considerable body of evidence, mostly derived from murine models of experimental infection, has implicated the pneumococcal, cholesterol-binding, pore-forming toxin, pneumolysin (Ply), in the pathogenesis of lung and myocardial dysfunction. Topics covered in this review include the burden of pneumococcal disease, risk factors, virulence determinants of the pneumococcus, complications of severe disease, antibiotic and adjuvant therapies, as well as the structure of Ply and the role of the toxin in disease pathogenesis. Given the increasing recognition of the clinical potential of Ply-neutralisation strategies, the remaining sections of the review are focused on updates of the types, benefits and limitations of currently available therapies which may attenuate, directly and/or indirectly, the injurious actions of Ply. These include recently described experimental therapies such as various phytochemicals and lipids, and a second group of more conventional agents the members of which remain the subject of ongoing clinical evaluation. This latter group, which is covered more extensively, encompasses macrolides, statins, corticosteroids, and platelet-targeted therapies, particularly aspirin.

Pneumococcal nasopharyngeal carriage among children in Brazil prior to the introduction of the 10-valent conjugate vaccine: a culture- and PCR-based survey

We performed two different approaches (broth enrichment step prior to culture (BEC) and PCR (BEPCR)) for detecting Streptococcus pneumoniae from nasopharyngeal specimens collected from 242 children aged <6 years attending one hospital (n = 140) and one childcare centre (n = 102) in a major urban area in Brazil. These specimens were collected immediately before the introduction of the 10-valent pneumococcal conjugate vaccine (PCV10) and the 13-valent vaccine (PCV13) for routine use in Brazil. Results were compared with previous findings obtained with direct culture (DC) on a selective medium. Colonisation prevalence was 58·3% (n = 141), being higher among children attending the childcare centre (62·7% vs. 55%). The culture-based methods (DC and BEC) enabled the detection of S. pneumoniae in 119 (49·2%) and 115 (47·5%) children, respectively. The PCR-based method (BEPCR) was more sensitive and 137 (56·6%) carriers were identified. Twenty-six serogroups/serotypes were identified, predominantly 6B, 19F, 14, 6A, 15C and 23F. Multiple colonisation was observed in 13 (5·4%) children. The estimated serotypes coverage of available PCVs was 40·4% for the 10-valent (included in the Brazilian immunisation programme) and 55·8% for the 13-valent (only available in private clinics). The use of robust approaches to obtain a more realistic insight about the asymptomatic carrier status is of paramount importance to estimate and assess the impact of vaccine implementation. The combination between culture-based and molecular methods constitutes a suitable strategy.

Nationwide Trends in Bacterial Meningitis before the Introduction of 13-Valent Pneumococcal Conjugate Vaccine-Burkina Faso, 2011-2013

BACKGROUND

Following introduction of Haemophilus influenzae type b vaccine in 2006 and serogroup A meningococcal conjugate vaccine in 2010, Streptococcus pneumoniae (Sp) became the leading cause of bacterial meningitis in Burkina Faso. We describe bacterial meningitis epidemiology, focusing on pneumococcal meningitis, before 13-valent pneumococcal conjugate vaccine (PCV13) introduction in the pediatric routine immunization program in October 2013.

METHODS

Nationwide population-based meningitis surveillance collects case-level demographic and clinical information and cerebrospinal fluid (CSF) laboratory results. Sp infections are confirmed by culture, real-time polymerase chain reaction (rt-PCR), or latex agglutination, and CSF serotyped using real-time and conventional PCR. We calculated incidence rates in cases per 100,000 persons, adjusting for age and proportion of cases with CSF tested at national reference laboratories, and case fatality ratios (CFR).

RESULTS

During 2011-2013, 1,528 pneumococcal meningitis cases were reported. Average annual adjusted incidence rates were 26.9 (<1 year), 5.4 (1-4 years), 7.2 (5-14 years), and 3.0 (≥15 years). Overall CFR was 23% and highest among children aged <1 year (32%) and adults ≥30 years (30%). Of 1,528 cases, 1,036 (68%) were serotyped: 71% were PCV13-associated serotypes, 14% were non-PCV13-associated serotypes, and 15% were non-typeable by PCR. Serotypes 1 (45%) and 12F/12A/12B/44/46 (8%) were most common. Among children aged <1 year, serotypes 5 (15%), 6A/6B (13%) and 1 (12%) predominated.

CONCLUSIONS

In Burkina Faso, the highest morbidity and mortality due to pneumococcal meningitis occurred among children aged <1 year. The majority of cases were due to PCV13-associated serotypes; introduction of PCV13 should substantially decrease this burden.

Understanding pneumococcal serotype 1 biology through population genomic analysis

BACKGROUND

Pneumococcus kills over one million children annually and over 90 % of these deaths occur in low-income countries especially in Sub-Saharan Africa (SSA) where HIV exacerbates the disease burden. In SSA, serotype 1 pneumococci particularly the endemic ST217 clone, causes majority of the pneumococcal disease burden. To understand the evolution of the virulent ST217 clone, we analysed ST217 whole genomes from isolates sampled from African and Asian countries.

METHODS

We analysed 226 whole genome sequences from the ST217 lineage sampled from 9 African and 4 Asian countries. We constructed a whole genome alignment and used it for phylogenetic and coalescent analyses. We also screened the genomes to determine presence of antibiotic resistance conferring genes.

RESULTS

Population structure analysis grouped the ST217 isolates into five sequence clusters (SCs), which were highly associated with different geographical regions and showed limited intracontinental and intercontinental spread. The SCs showed lower than expected genomic sequence, which suggested strong purifying selection and small population sizes caused by bottlenecks. Recombination rates varied between the SCs but were lower than in other successful clones such as PMEN1. African isolates showed higher prevalence of antibiotic resistance genes than Asian isolates. Interestingly, certain West African isolates harbored a defective chloramphenicol and tetracycline resistance-conferring element (Tn5253) with a deletion in the loci encoding the chloramphenicol resistance gene (cat pC194), which caused lower chloramphenicol than tetracycline resistance. Furthermore, certain genes that promote colonisation were absent in the isolates, which may contribute to serotype 1's rarity in carriage and consequently its lower recombination rates.

CONCLUSIONS

The high phylogeographic diversity of the ST217 clone shows that this clone has been in circulation globally for a long time, which allowed its diversification and adaptation in different geographical regions. Such geographic adaptation reflects local variations in selection pressures in different locales. Further studies will be required to fully understand the biological mechanisms which makes the ST217 clone highly invasive but unable to successfully colonise the human nasopharynx for long durations which results in lower recombination rates.

Recombination in Streptococcus pneumoniae Lineages Increase with Carriage Duration and Size of the Polysaccharide Capsule

Streptococcus pneumoniae causes a high burden of invasive pneumococcal disease (IPD) globally, especially in children from resource-poor settings. Like many bacteria, the pneumococcus can import DNA from other strains or even species by transformation and homologous recombination, which has allowed the pneumococcus to evade clinical interventions such as antibiotics and pneumococcal conjugate vaccines (PCVs). Pneumococci are enclosed in a complex polysaccharide capsule that determines the serotype; the capsule varies in size and is associated with properties including carriage prevalence and virulence. We determined and quantified the association between capsule and recombination events using genomic data from a diverse collection of serotypes sampled in Malawi. We determined both the amount of variation introduced by recombination relative to mutation (the relative rate) and how many individual recombination events occur per isolate (the frequency). Using univariate analyses, we found an association between both recombination measures and multiple factors associated with the capsule, including duration and prevalence of carriage. Because many capsular factors are correlated, we used multivariate analysis to correct for collinearity. Capsule size and carriage duration remained positively associated with recombination, although with a reduced P value, and this effect may be mediated through some unassayed additional property associated with larger capsules. This work describes an important impact of serotype on recombination that has been previously overlooked. While the details of how this effect is achieved remain to be determined, it may have important consequences for the serotype-specific response to vaccines and other interventions.

IMPORTANCE

The capsule determines >90 different pneumococcal serotypes, which vary in capsule size, virulence, duration, and prevalence of carriage. Current serotype-specific vaccines elicit anticapsule antibodies. Pneumococcus can take up exogenous DNA by transformation and insert it into its chromosome by homologous recombination. This mechanism has disseminated drug resistance and generated vaccine escape variants. It is hence crucial to pneumococcal evolutionary response to interventions, but there has been no systematic study quantifying whether serotypes vary in recombination and whether this is associated with serotype-specific properties such as capsule size or carriage duration. Larger capsules could physically inhibit DNA uptake, or given the longer carriage duration for larger capsules, this may promote recombination. We find that recombination varies among capsules and is associated with capsule size, carriage duration, and carriage prevalence and negatively associated with invasiveness. The consequence of this work is that serotypes with different capsules may respond differently to selective pressures like vaccines.

Anatomical site-specific contributions of pneumococcal virulence determinants

Streptococcus pneumoniae is an opportunistic pathogen globally associated with significant morbidity and mortality. It is capable of causing a wide range of diseases including sinusitis, conjunctivitis, otitis media, pneumonia, bacteraemia, sepsis, and meningitis. While its capsular polysaccharide is indispensible for invasive disease, and opsonising antibodies against the capsule are the basis for the current vaccines, a long history of biomedical research indicates that other components of this Gram-positive bacterium are also critical for virulence. Herein we review the contribution of pneumococcal virulence determinants to survival and persistence in the context of distinct anatomical sites. We discuss how these determinants allow the pneumococcus to evade mucociliary clearance during colonisation, establish lower respiratory tract infection, resist complement deposition and opsonophagocytosis in the bloodstream, and invade secondary tissues such as the central nervous system leading to meningitis. We do so in a manner that highlights both the critical role of the capsular polysaccharide and the accompanying and necessary protein determinants. Understanding the complex interplay between host and pathogen is necessary to find new ways to prevent pneumococcal infection. This review is an attempt to do so with consideration for the latest research findings.

Phylogenetic Analysis of Invasive Serotype 1 Pneumococcus in South Africa, 1989 to 2013

Serotype 1 is an important cause of invasive pneumococcal disease in South Africa and has declined following the introduction of the 13-valent pneumococcal conjugate vaccine in 2011. We genetically characterized 912 invasive serotype 1 isolates from 1989 to 2013. Simpson's diversity index (D) and recombination ratios were calculated. Factors associated with sequence types (STs) were assessed. Clonal complex 217 represented 96% (872/912) of the sampled isolates. Following the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13), ST diversity increased in children <5 years (D, 0.39 to 0.63, P = 0.002) and individuals >14 years (D, 0.35 to 0.54, P < 0.001): ST-217 declined proportionately in children <5 years (153/203 [75%] versus 21/37 [57%], P = 0.027) and individuals >14 years (242/305 [79%] versus 96/148 [65%], P = 0.001), whereas ST-9067 increased (4/684 [0.6%] versus 24/228 [11%], P < 0.001). Three subclades were identified within ST-217: ST-217_C1 (353/382 [92%]), ST-217_C2 (15/382 [4%]), and ST-217_C3 (14/382 [4%]). ST-217_C2, ST-217_C3, and single-locus variant (SLV) ST-8314 (20/912 [2%]) were associated with nonsusceptibility to chloramphenicol, tetracycline, and co-trimoxazole. ST-8314 (20/912 [2%]) was also associated with increased nonsusceptibility to penicillin (P < 0.001). ST-217_C3 and newly reported ST-9067 had higher recombination ratios than those of ST-217_C1 (4.344 versus 0.091, P < 0.001; and 0.086 versus 0.013, P < 0.001, respectively). Increases in genetic diversity were noted post-PCV13, and lineages associated with antimicrobial nonsusceptibility were identified.

Epidemiology of Serotype 1 Invasive Pneumococcal Disease, South Africa, 2003-2013

In South Africa, 7-valent pneumococcal conjugate vaccine (PCV) was introduced in April 2009 and replaced with 13-valent PCV in April 2011. We describe the epidemiology of serotype 1 Streptococcus pneumoniae disease during the pre- and post-PCV eras (2003-2013). Using laboratory-based invasive pneumococcal disease (IPD) surveillance, we calculated annual incidences, identified IPD clusters, and determined serotype 1-associated factors. Of 46,483 IPD cases, 4,544 (10%) were caused by serotype 1. Two clusters of serotype 1 infection were detected during 2003-2004 and 2008-2012, but incidence decreased after 2011. Among children <5 years of age, those who had non-serotype 1 IPD had shorter hospital stays, fewer cases of penicillin-nonsusceptible disease, and lower HIV prevalence and in-hospital death rates than did those with serotype 1 IPD; similar factors were noted for older patients. Serotype 1 IPD had distinctive clinical features in South Africa, and annual incidences fluctuated, with decreases noted after the introduction of PCV13.

Pneumococcal population in the era of vaccination: changes in composition and the relation to clinical outcomes

BACKGROUND

Vaccination of infants with pneumococcal conjugate vaccines (PCV) has resulted in major shifts in circulating serotypes.

AIM

To investigate the impact of PCV7 on the clonal composition of the pneumococcal population, and the relation of clonal lineages and clinical outcome.

MATERIALS & METHODS

By using multiple-locus variable number of tandem repeat analysis, we assessed the pneumococcal populations before (n = 1154), 2-3 years after (n = 1190) and 4-6 years after (n = 1244) the introduction of PCV7 in The Netherlands.

RESULTS

We found statistically significant shifts in clonal lineages within serotypes 1 and 12F based on multiple-locus variable number of tandem repeat analysis results after the implementation of PCV7. Within serotype 12F, the increasing clonal lineage was significantly more associated with pneumonia.

CONCLUSION

Shifts in clonal lineages within serotypes could impact the outcomes of pneumococcal disease and fill the niche of the vaccine serotypes.

Pneumococcal Capsules and Their Types: Past, Present, and Future

Streptococcus pneumoniae (the pneumococcus) is an important human pathogen. Its virulence is largely due to its polysaccharide capsule, which shields it from the host immune system, and because of this, the capsule has been extensively studied. Studies of the capsule led to the identification of DNA as the genetic material, identification of many different capsular serotypes, and identification of the serotype-specific nature of protection by adaptive immunity. Recent studies have led to the determination of capsular polysaccharide structures for many serotypes using advanced analytical technologies, complete elucidation of genetic basis for the capsular types, and the development of highly effective pneumococcal conjugate vaccines. Conjugate vaccine use has altered the serotype distribution by either serotype replacement or switching, and this has increased the need to serotype pneumococci. Due to great advances in molecular technologies and our understanding of the pneumococcal genome, molecular approaches have become powerful tools to predict pneumococcal serotypes. In addition, more-precise and -efficient serotyping methods that directly detect polysaccharide structures are emerging. These improvements in our capabilities will greatly enhance future investigations of pneumococcal epidemiology and diseases and the biology of colonization and innate immunity to pneumococcal capsules.

Risk and outcomes of invasive pneumococcal disease in adults with underlying conditions in the post-PCV7 era, The Netherlands

BACKGROUND

Immunocompromising conditions and advanced age (≥65 years) are associated with a high risk for invasive pneumococcal disease (IPD). We investigated the risk and outcomes of IPD in adults with underlying conditions in the post-PCV7 era in The Netherlands.

METHODS

IPD data from 2008 to 2012 was obtained from the national pneumococcal surveillance system, covering 25% of the Dutch population. Population estimates of underlying conditions were derived from the primary care data (2012). IPD incidence in adults with immunocompromising conditions (high risk group) and non-immunocompromising comorbidities (medium risk group) were compared to the "normal risk group" without diagnosed comorbidities. Case-fatality and ICU admission in the different risk groups was analyzed by logistic regression. Serotype specific propensities to affect high risk group IPD patients were calculated.

RESULTS

Adults with a high risk condition have a 18-fold (95% CI 15.6-21.2) and 3-fold (95% CI 2.6-3.9) higher risk compared to the normal risk group for IPD at age 18-64 years and 65 years and older, respectively. In case of a medium risk condition, the risk is 5-fold (95% CI 4.3-5.7) and 2-fold (95% CI 1.9-2.6) higher in age groups 18-64 and ≥65 years old. Likewise, IPD patients with a high or medium risk condition have a higher case-fatality (after adjustment for age, odds ratio: 2-fold (95% CI 1.5-3.5) and 1.4-fold (95% CI 1.0-2.1), respectively). Several serotypes (e.g. 6A, 6B, 23A and 23B) are associated with a significantly higher propensity to cause disease in high risk patients.

CONCLUSIONS

The risk for IPD and death in the post-PCV7 era has remained considerably high in adults and elderly with underlying conditions. The identification of serotypes with a high propensity to affect risk groups can be important for selecting (future) vaccine serotypes.

Region-specific diversification of the highly virulent serotype 1 Streptococcus pneumoniae

Serotype 1 Streptococcus pneumoniae is a leading cause of invasive pneumococcal disease (IPD) worldwide, with the highest burden in developing countries. We report the whole-genome sequencing analysis of 448 serotype 1 isolates from 27 countries worldwide (including 11 in Africa). The global serotype 1 population shows a strong phylogeographic structure at the continental level, and within Africa there is further region-specific structure. Our results demonstrate that region-specific diversification within Africa has been driven by limited cross-region transfer events, genetic recombination and antimicrobial selective pressure. Clonal replacement of the dominant serotype 1 clones circulating within regions is uncommon; however, here we report on the accessory gene content that has contributed to a rare clonal replacement event of ST3081 with ST618 as the dominant cause of IPD in the Gambia.

Streptococcus pneumoniae nasopharyngeal colonisation in children aged under six years with acute respiratory tract infection in Lithuania, February 2012 to March 2013

serotypes among children in Lithuania are limited. A prospective study was carried out from February 2012 to March 2013 to evaluate the circulation of SPn serotypes among young children in five cities of Lithuania before the introduction of universal vaccination with pneumococcal conjugate vaccine (PCV). A total of 900 children under six years of age who presented to primary care centres or a hospital emergency department with acute respiratory tract infection (RTI) were enrolled in the study. The SPn colonisation rate was40.8% (367/900), with a peak at two and three years old(48.8% and 45.4%, respectively). Of the 367 SPn isolates, the most common serotypes were 6B (15.8%,n = 58), 19F (13.9%, n = 51), 23F (13.9%, n = 51), 15(10.1%, n = 37), 14 (9.5%, n = 35), 6A (9.3%, n= 34),11 (4.6%, n = 17), 3 (3.0%, n = 11) and 18C (3.0%, n =11); less frequent were 23 (non-23F) (2.7%, n = 10), 19A(2.2%, n = 8) and 9V (1.6%, n = 6). Serotypes 6A and 11 were more common in children under two years-old;18C was found only in children aged two to five years.The serotypes found might be an important predictor of the likely effectiveness of the PCVs currently available in Lithuania

Estimation of the invasive disease potential of Streptococcus pneumoniae in children by the use of direct capsular typing in clinical specimens

Traditionally, invasiveness indexes have been based on culture methods. We aimed to establish a new classification of the invasive disease potential of pneumococcal serotypes causing invasive pediatric disease in the era of conjugate vaccines in Catalonia, Spain, by adding capsular typing of Streptococcus pneumoniae in direct sample. Two samples of children attended at the University Hospital Sant Joan de Déu (Barcelona, Spain) between 2007 and 2011 were compared: a first sample of 358 children with invasive pneumococcal disease and a second sample of 402 pneumococcal nasopharyngeal carriers selected from 714 healthy children admitted for minor surgical procedures. The most common invasive serotypes were 1 (20.1 %, n = 72), 19A (13.9 %, n = 50), 3 (12.3 %, n = 44), and 7FA (7.5 %, n = 27), whereas the most common serotypes in carriage were 19A (8.7 %, n = 38), 10FC33C (7.8 %, n = 34), 6C (6.9 %, n = 30), and 19FBC (5.5 %, n = 24). We detected a rate of cocolonization of 26.4 % (n = 89) among the 336 samples serotyped in the carriers population. Serotypes 1, 3, and 7FA were significantly associated with high invasiveness. Serotypes 6C, 10FC33C, 23A, 35B, 19FBC, 21, 11AD, 15BC, 23B, 34, and 6A were significantly associated with low invasiveness. Our results proved that the use of molecular techniques in direct sample for both the detection and the capsular identification of Streptococcus pneumoniae is very useful to obtain a more accurate calculation of the invasiveness of the different pneumococcal serotypes.

Impact of the Hajj on pneumococcal transmission

Over two million Muslim pilgrims assemble annually in Mecca and Medina, Saudi Arabia, to complete the Hajj. The large number of people in a crowded environment increases the potential for pneumococcal carriage amplification. We evaluated pneumococcal carriage prevalence with four cross-sectional studies conducted at beginning-Hajj (Mecca) and end-Hajj (Mina) during 2011 and 2012. A questionnaire was administered and a nasopharyngeal swab was collected. The swab was tested for pneumococcus, serotype and antibiotic resistance. A total of 3203 subjects (1590 at beginning-Hajj and 1613 at end-Hajj) originating from 18 countries in Africa or Asia were enrolled. The overall pneumococcal carriage prevalence was 6.0%. There was an increase in carriage between beginning-Hajj and end-Hajj cohorts for: overall carriage (4.4% versus 7.5%, prevalence ratio (PR) 1.7, 95% CI 1.3-2.3), and carriage of 23-valent pneumococcal polysaccharide vaccine serotypes (2.3% versus 4.1%, PR 1.8, 95% CI 1.2-2.7), 13-valent pneumococcal conjugate vaccine (PCV) serotypes (1.1% versus 3.6%, PR 3.2, 95% CI 1.9-5.6), 10-valent PCV serotypes (0.6% versus 1.6%, PR 2.6, 95% CI 1.2-5.3), antibiotic non-susceptible isolates (2.5% versus 6.1%, PR 2.5, 95% CI 1.7-3.6) and multiple non-susceptible isolates (0.6% versus 2.2%, PR 3.8, 95% CI 1.8-7.9). Fifty-two different serotypes were identified, most commonly serotypes 3 (17%), 19F (5%) and 34 (5%). These results suggest that the Hajj may increase pneumococcal carriage-particularly conjugate vaccine serotypes and antibiotic non-susceptible strains, although the exact mechanism remains unknown. The Hajj may therefore provide a mechanism for the global distribution of pneumococci.

TLR2 signaling decreases transmission of Streptococcus pneumoniae by limiting bacterial shedding in an infant mouse Influenza A co-infection model

While the importance of transmission of pathogens is widely accepted, there is currently little mechanistic understanding of this process. Nasal carriage of Streptococcus pneumoniae (the pneumococcus) is common in humans, especially in early childhood, and is a prerequisite for the development of disease and transmission among hosts. In this study, we adapted an infant mouse model to elucidate host determinants of transmission of S. pneumoniae from inoculated index mice to uninfected contact mice. In the context of co-infection with influenza A virus, the pneumococcus was transmitted among wildtype littermates, with approximately half of the contact mice acquiring colonization. Mice deficient for TLR2 were colonized to a similar density but transmitted S. pneumoniae more efficiently (100% transmission) than wildtype animals and showed decreased expression of interferon α and higher viral titers. The greater viral burden in tlr2-/- mice correlated with heightened inflammation, and was responsible for an increase in bacterial shedding from the mouse nose. The role of TLR2 signaling was confirmed by intranasal treatment of wildtype mice with the agonist Pam3Cys, which decreased inflammation and reduced bacterial shedding and transmission. Taken together, these results suggest that the innate immune response to influenza virus promotes bacterial shedding, allowing the bacteria to transit from host to host. These findings provide insight into the role of host factors in the increased pneumococcal carriage rates seen during flu season and contribute to our overall understanding of pathogen transmission.

An ahemolytic pneumolysin of Streptococcus pneumoniae manipulates human innate and CD4⁺ T-cell responses and reduces resistance to colonization in mice in a serotype-independent manner

BACKGROUND

Some Streptococcus pneumoniae serotypes express an ahemolytic pneumolysin (PLYa). Serotypes that commonly express PLYa, including serotype 8 (ST8) and ST1, are often associated with a low prevalence during colonization but a higher propensity to cause invasive disease. We sought to study the host response to ST8 PLYa in a homologous and heterologous capsular background.

METHODS

We genetically exchanged the PLYa of ST8 strain 6308 with the hemolytic PLY (PLYh) of ST3 A66.1 and vice versa and determined the impact of the exchange on nasopharyngeal colonization in mice. Then, to compare the response of human cells to PLYa-expressing and PLYh-expressing strains, we infected human peripheral blood mononuclear cells (PBMCs) with PLY-switched strains and assessed dendritic cell and CD4(+) T-cell responses by intracellular cytokine staining.

RESULT

Mice colonized with PLYa-expressing strains had significantly higher colonization densities than those colonized with PLYh-expressing strains, irrespective of capsular background. Compared with infection of PBMCs with PLYh-expressing strains, infection with PLYa-expressing strains induced diminished innate (dendritic cell cytokines, costimulatory receptor, and apoptotic) and adaptive (CD4(+) T-cell proliferative and memory interleukin 17A) responses.

CONCLUSION

Our findings demonstrate that PLYa has the potential to manipulate host immunity irrespective of capsule type. PLY exchange between STs expressing PLYa and PLYh could lead to unexpected colonization or invasion phenotypes.

Recurrent pneumococcal invasive disease in the region of Madrid during a five-year period

PURPOSE

The aim of this study was to describe the clinical and microbiological characteristics of recurrent invasive pneumococcal disease (RIPD) cases identified in the Region of Madrid between January 2007 and December 2011.

METHODS

Streptococcus pneumoniae serotyping was performed by Pneumotest-Latex and Quellung reaction. Molecular typing was carried out by pulsed-field gel electrophoresis (PFGE). A relapse was defined as any case of RIPD caused by strains with similar PFGE profile. Re-infections were defined by detection of recurrent episodes caused by strains with different PFGE patterns.

RESULTS

During the study period, 2,929 S. pneumoniae strains isolated from 2,858 patients with invasive pneumococcal disease (IPD) were studied. In 61 patients (2.1 %), 132 episodes of RIPD were detected (two episodes in 52 patients, three in 8 and four in 1). Twelve patients had relapses, 47 had re-infections and two had re-infections followed by relapses. Common risk factors to developing RIPD were HIV (42.6 %) and haematological malignancies (16.4 %). The most frequent serotypes were 8 (16 episodes) and 19A (15 episodes). Fourteen strains that were resistant to levofloxacin were also resistant to erythromycin. The proportion of strains co-resistant to erythromycin and levofloxacin was significantly higher in relapses (11/29) than in re-infections (3/103).

CONCLUSIONS

The occurrence of repeated episodes of IPD in the same patient over the time is not an exceptional issue. Some underlying conditions that may favour these recurrences, mainly immunosuppression, need to be considered in patients having an episode of IPD.

Current concepts in host-microbe interaction leading to pneumococcal pneumonia

PURPOSE OF REVIEW

Infection with Streptococcus pneumoniae (pneumococcus) results in colonization, which can lead to local or invasive disease, of which pneumonia is the most common manifestation. Despite the availability of pneumococcal vaccines, pneumococcal pneumonia is the leading cause of community and inhospital pneumonia in the United States and globally. This article discusses new insights into the pathogenesis of pneumococcal disease.

RECENT FINDINGS

The host-microbe interactions that determine whether pneumococcal colonization will result in clearance or invasive disease are highly complex. This article focuses on new information in three areas that bear on the pathogenesis of pneumococcal disease: factors that govern colonization, the prelude to invasive disease, including effects on colonization and invasion of capsular serotype, pneumolysin, surface proteins that regulate complement deposition, biofilm formation and agglutination; the effect of coinfection with other bacteria and viruses on pneumococcal growth and virulence, including the synergistic effect of influenza virus; and the contribution of the host inflammatory response to the pathogenesis of pneumococcal pneumonia, including the effects of pattern recognition molecules, cells that enhance and modulate inflammation, and therapies that modulate inflammation, such as statins.

SUMMARY

Recent research on pneumococcal pathogenesis reveals new mechanisms by which microbial factors govern the ability of pneumococcus to progress from the state of colonization to disease and host inflammatory responses contribute to the development of pneumonia. These mechanisms suggest that therapies which modulate the inflammatory response could hold promise for ameliorating damage stemming from the host inflammatory response in pneumococcal disease.

Surveillance of pneumococcal serotype 1 carriage during an outbreak of serotype 1 invasive pneumococcal disease in central Australia 2010-2012

BACKGROUND

An outbreak of serotype 1 invasive pneumococcal disease (IPD) occurred in Central Australia from October 2010 to the latter part of 2012. Surveillance of serotype 1 carriage was conducted to determine epidemiological features of asymptomatic carriage that could potentially be driving the outbreak.

METHODS

130 patients and accompanying persons presenting at Alice Springs Hospital Emergency Department consented to nasopharyngeal swab (NPS) collection. NPS were processed by standard methods, including culture, pneumococcal lytA quantitative real-time PCR, serotype 1-specific real-time PCR and multi-locus sequence typing (MLST).

RESULTS

Pneumococcal carriage was detected in 16% of participants. Carriage was highest in the under 10 year olds from remote communities surrounding Alice Springs (75%). Four NPS were positive for serotype 1 DNA by PCR; 3 were also culture-positive for serotype 1 pneumococci. Serotype 1 isolates had atypical colony morphology on primary culture. All serotype 1 carriers were healthy children 5 to 8 years of age from remote communities. By MLST, serotype 1 isolates were ST306, as were IPD isolates associated with this outbreak.

CONCLUSIONS

During an outbreak of serotype 1 ST306 IPD, carriage of the outbreak strain was detected in 3% NPS collected. All carriers were healthy children 5 to 8 years of age.

Clinical and economic burden of invasive pneumococcal disease in adults: a multicenter hospital-based study

BACKGROUND

Streptococcus pneumoniae causes a broad spectrum of illnesses ranging from mild upper respiratory tract infections to invasive pneumococcal disease (IPD). Quantitative data on the burden of pneumococcal disease, important for the establishment of appropriate vaccination strategies, is currently lacking in adults.

METHODS

This multicenter, retrospective cohort study was designed to estimate the clinical and economic burden of IPD in adults over the last decade. Data were collected from patients with IPD at 10 university hospitals in South Korea. We estimated the proportion of IPD among all hospitalized patients, the case fatality rate, and the direct medical costs of IPD. Data were further analyzed according to age and risk groups.

RESULTS

During the study period, 970 patients with IPD were identified. The mean age for all patients was 60.9 years; patients aged 50-64 years (33.0%) were most numerous, followed by those aged 65-74 years (27.4%). Overall, the proportion of IPD was 0.36 cases/1000 hospitalized patients and the case fatality rate was 30.9%, which increased significantly with age (p < 0.01). The mean direct medical costs were estimated to be US $7,452 without a difference between age and risk groups. On multivariate analysis, old age, advanced ECOG performance status, bacteremic pneumonia, and nosocomial infection were independent risk factors of 30-day case fatality.

CONCLUSIONS

The clinical disease burden of IPD increased significantly with age and direct medical costs from IPD were substantial, regardless of age and co-morbid conditions. The current age-based vaccination strategy appears to be appropriate.

Determination of pneumococcal serotypes in meningitis cases in Niger, 2003-2011

Background

The epidemiology of pneumococcal meningitis in the African ‘meningitis belt’ is poorly studied. In order to ensure an effective vaccination strategy and post-vaccination surveillance, we examined the serotype distribution patterns of pneumococcal meningitis in Niger over the period 2003–2011.

Methods

Cerebrospinal fluid (CSF) samples were collected from different health facilities throughout Niger in the frame of the national microbiological surveillance of meningitis. Determination of the serotype of CSF positive for pneumococci was performed using a sequential multiplex PCR method (SM-PCR) adapted with a national algorithm in which 32 different serotypes were covered and grouped into eight consecutive PCR.

Results

The SM-PCR assay could predict the Sp serotype for 779 CSF (88.7%), 98 CSF (11.3%) were not-typeable in our national-adapted algorithm. In total, 26 different serotypes were identified. Serotype 1 (n = 393) was the most prevalent and accounted for 45.3% of infections, followed by serogroups/serotypes 12F/(12A)/(44)/(46) (7.3%), 6/(6A/6B/6C/6D) (5.4%), 14 (5.2%), 5 (4.6%), 23F (4.2%), 45 (3.6%), 2 (3.1%), 18/(18A/18B/18C/18F) (2.9%) and 17 others serotypes with a prevalence of less than 2%. The proportion of serotype 1 in infants(<2 years old) represented only 4.3% of the cases affected by this serotype. In contrast, serotypes 5, 6, 14, 19A and 23F were only detected in very young children.

Conclusions

The proportion of serotype 1 in the pneumococcal meningitis cases and the theoretical vaccine coverage across all age groups advocates for the introduction of a conjugate vaccine (PCV10 or 13) into the Expanded Programme on Immunization (EPI) in Niger. Post-vaccine introduction surveillance supported by molecular approaches will be essential to provide a comprehensive picture of the impact of the vaccine on the burden reduction of pneumococcal meningitis and on pneumococcal serotype distribution.

DNA bacterial load in children with bacteremic pneumococcal community-acquired pneumonia

This study was conducted to evaluate the association between pneumococcal DNA load and parapneumonic pleural effusion (PPE) in children with community-acquired pneumonia. Bacterial load was quantified and related to the presence of PPE with or without empyema in 72 otherwise healthy children aged ≤5 years who were hospitalised because of radiographically confirmed CAP and showed a real-time polymerase chain reaction that was positive for Streptococcus pneumoniae. The proportion of children with a high bacterial load (i.e. ≥265 DNA copies/mL) was larger among the subjects with PPE than those without it. Multivariate analysis showed that a high bacterial load was significantly associated with PPE (OR 8.65; 95% CI 1.10-67.8 vs a bacterial load of <125 copies/mL). Children with infection due to pneumococcal serotype 19A were at highest risk of developing PPE (OR 7.44; 95% CI 1.10-50.4 vs all other typeable serotypes). The patients with CAP due to pneumococcal serotypes that are not included in the 13-valent conjugate vaccine (PCV13) were more frequently affected by PPE than those with infections associated with serotypes included in the vaccine, except for serotype 19A. Bacterial loads of ≥265 DNA copies/mL are significantly associated with PPE, and serotype 19A is significantly associated with a high bacterial load and the development of PPE. The mean bacterial load of the patients with empyema was higher than that of patients with simple PPE. Although further studies are required, it seems that serotypes not included in PCV13 can play a major role in causing a higher bacterial load and PPE.

Clinical implications of pneumococcal serotypes: invasive disease potential, clinical presentations, and antibiotic resistance

Streptococcus pneumoniae can asymptomatically colonize the nasopharynx and cause a diverse range of illnesses. This clinical spectrum from colonization to invasive pneumococcal disease (IPD) appears to depend on the pneumococcal capsular serotype rather than the genetic background. According to a literature review, serotypes 1, 4, 5, 7F, 8, 12F, 14, 18C, and 19A are more likely to cause IPD. Although serotypes 1 and 19A are the predominant causes of invasive pneumococcal pneumonia, serotype 14 remains one of the most common etiologic agents of non-bacteremic pneumonia in adults, even after 7-valent pneumococcal conjugate vaccine (PCV7) introduction. Serotypes 1, 3, and 19A pneumococci are likely to cause empyema and hemolytic uremic syndrome. Serotype 1 pneumococcal meningitis is prevalent in the African meningitis belt, with a high fatality rate. In contrast to the capsule type, genotype is more closely associated with antibiotic resistance. CC320/271 strains expressing serotype 19A are multidrug-resistant (MDR) and prevalent worldwide in the era of PCV7. Several clones of MDR serotype 6C pneumococci emerged, and a MDR 6D clone (ST282) has been identified in Korea. Since the pneumococcal epidemiology of capsule types varies geographically and temporally, a nationwide serosurveillance system is vital to establishing appropriate vaccination strategies for each country.

The fundamental link between pneumococcal carriage and disease

Streptococcus pneumoniae (pneumococcus) is a major cause of worldwide mortality and morbidity, and to a large extent is vaccine-preventable. Nasopharyngeal carriage of pneumococcus precedes disease and is the source of pneumococcal spread between people. The use of vaccine effect on carriage as part of the vaccine licensure and post-vaccine introduction evaluation could facilitate and expand the licensure of new, life-saving pneumococcal vaccines and enable a comprehensive estimate of population effects after vaccine introduction. The authors provide a review of the evidence supporting pneumococcal carriage at the individual level as an immediate and necessary precursor to pneumococcal disease. Based on such a causal link between carriage and disease, the authors emphasize the role of information on pneumococcal carriage in vaccine trials and in public health decision-making.

Invasive pneumococcal disease in healthy adults: increase of empyema associated with the clonal-type Sweden(1)-ST306

Background

Adult invasive pneumococcal disease (IPD) occurs mainly in the elderly and patients with co-morbidities. Little is known about the clinical characteristics, serotypes and genotypes causing IPD in healthy adults.

Methods

We studied 745 culture-proven cases of IPD in adult patients aged 18–64 years (1996–2010). Patients were included in two groups: 1.) adults with co-morbidities, and 2.) healthy adults, who had no prior or coincident diagnosis of a chronic or immunosuppressive underlying disease. Microbiological studies included pneumococcal serotyping and genotyping.

Results

Of 745 IPD episodes, 525 (70%) occurred in patients with co-morbidities and 220 (30%) in healthy adults. The healthy adults with IPD were often smokers (56%) or alcohol abusers (18%). As compared to patients with co-morbidities, the healthy adults had (P<0.05): younger age (43.5+/−13.1 vs. 48.7+/−11.3 years); higher proportions of women (45% vs. 24%), pneumonia with empyema (15% vs. 7%) and infection with non-PCV7 serotypes including serotypes 1 (25% vs. 5%), 7F (13% vs. 4%), and 5 (7% vs. 2%); and lower mortality (5% vs. 20%). Empyema was more frequently caused by serotype 1. No death occurred among 79 patients with serotype 1 IPD. There was an emergence of virulent clonal-types Sweden¹-ST306 and Netherlands^7F-ST191. The vaccine serotype coverage with the PCV13 was higher in healthy adults than in patients with co-morbidities: 82% and 56%, respectively, P<0.001.

Conclusion

In this clinical study, one-third of adults with IPD had no underlying chronic or immunosuppressive diseases (healthy adults). They were often smokers and alcohol abusers, and frequently presents with pneumonia and empyema caused by virulent clones of non-PCV7 serotypes such as the Sweden¹-ST306. Thus, implementing tobacco and alcohol abuse-cessation measures and a proper pneumococcal vaccination, such as PCV13 policy, in active smokers and alcohol abusers may diminish the burden of IPD in adults.