Host-pathogen interaction during Streptococcus pneumoniae colonization and infection

__Abstract__ Streptococcus pneumoniae was discovered by Sternberg and Pasteur in 1880. It took another six years to discover that this microorganism, called the pneumococcus, was the actual cause of bacterial pneumonia . Subsequently, this bacterium has been shown to provoke an impressive number of diseases, which can be roughly classified in respiratory and invasive. Respiratory diseases by S. pneumoniae are sinusitis, otitis media, bronchitis and pneumonia, of which the latter one may be complicated by septicemia . Disseminated invasive infections caused by the pneumococcus include sepsis, meningitis, endocarditis and arthritis. Morbidity and mortality are high both in the developing and the developed world: annually 3 million people die worldwide of pneumococcal infections. Approximately 1 million are children under the age of five years . Risk groups for pneumococcal disease are children younger than 2 years, elderly people and immunocompromised patients . In children, the increased risk for pneumococcal infections is mainly due to a relatively immature immune response to type II T-cell independent (TI-2) antigens such as capsular polysaccharides . In the elderly, the ability of both the innate as well as the adaptive immunity to respond to pneumococcal infection are thought to decline . In addition, higher rates of pneumococcal invasive diseases have been observed among populations such as Alaskan Natives, American Indians and African Americans . Patient groups who are at risk for particular variants of pneumococcal diseases are well defined. For example functional asplenia as in sickle cell disease as well as anatomic asplenia are serious risk factors for pneumococcal sepsis. This is due to the absence or dysfunction of the spleen, which is involved in systemic clearance of S. pneumoniae. In addition, complement deficiency and lower levels of circulating antibodies are thought to contribute to the increased susceptibility to pneumococcal infections in patients with sickle cell disease and other haemoglobinopathies . A relatively new risk group for pneumococcal meningitis are children with a cochlear implantation . Disease in these patients is thought to occur by the presence of a continuum between the outer ear and the inner skull. In general, patients with cerebrospinal fluid leakage, immunodeficiencies, chronic cardiovascular and pulmonary disease, HIV infections and diabetes mellitus are considered at risk for pneumococcal invasive disease

Molecular epidemiology of penicillin-nonsusceptible Streptococcus pneumoniae among children in Greece

A total of 145 penicillin-nonsusceptible Streptococcus pneumoniae strains were isolated from young carriers in Greece and analyzed by antibiotic susceptibility testing, serotyping, restriction fragment end labeling (RFEL), and penicillin-binding protein (PBP) genotyping. The serotypes 23A and 23F (54%), 19A and 19F (25%), 9V (5%), 15A, 15B, and 15C (4%), 6A and 6B (4%), and 21 (4%) were most prevalent in this collection. Fifty-three distinct RFEL types were identified. Sixteen different RFEL clusters, harboring 2 to 32 strains each, accounted for 82% of all strains. Eight of these genetic clusters representing 60% of the strains were previously identified in other countries. A predominant lineage of 66 strains (46%) harboring five RFEL types and the serotypes 19F and 23F was closely related to the pandemic clone Spain(23F)-1 (genetic relatedness of > or =85%). Another lineage, representing 11 strains, showed close genetic relatedness to the pandemic clone France(9V)-3. Another lineage of 8 serotype 21 strains was Greece specific since the RFEL types were not observed in an international collection of 193 genotypes from 16 different countries. Characterization of the PBP genes pbp1a, pbp2b, and pbp2x revealed 20 distinct PBP genotypes of which PBP type 1-1-1, initially observed in the pandemic clones 23F and 9V, was predominantly present in 11 RFEL types in this Greek collection of penicillin-nonsusceptible strains (55%). Sixteen PBP types covering 52 strains (36%) were Greece specific. This study underlines the strong contribution of penicillin-resistant international clones to the prevalence and spread of penicillin-nonsusceptible pneumococci among young children in Greece

Pneumococcal Conjugate Vaccination and Nasopharyngeal Acquisition of Pneumococcal Serotype 19A Strains

Context The rapid increase in multiresistant serotype 19A as a cause of invasive and respiratory pneumococcal disease has been associated in time with the widespread implementation of 7-valent pneumococcal conjugate vaccination (PCV-7) in several countries. Because spontaneous fluctuations in time and antibiotic selective pressure may have induced this serotype 19A increase, controlled studies are needed to assess the role of PCV-7. Objective To examine the association of PCV-7 vaccination and nasopharyngeal acquisition of serotype 19A pneumococci, their clonal distribution, and antibiotic susceptibility. Design, Setting, and Patients Post hoc per-protocol completer's analysis as part of a randomized controlled trial of nasopharyngeal Streptococcus pneumoniae carriage enrolling 1003 healthy newborns with follow-up to the age of 24 months in the Netherlands, which has low antibiotic resistance rates. The study was conducted before widespread PCV-7 implementation in infants, between July 7, 2005, and February 14, 2008. Nasopharyngeal swabs were obtained at the age of 6 weeks and at 6, 12, 18, and 24 months. Intervention Infants were randomly assigned to receive 2 doses of PCV-7 at 2 and 4 months; 2 + 1 doses of PCV-7 at 2, 4, and 11 months; or no dosage (unvaccinated control group). Main Outcome Measure Cumulative proportion of children with nasopharyngeal acquisition of a new serotype 19A strain from 6 through 24 months of age. Results Nine hundred forty-eight children completed the study. Fifty-four nasopharyngeal serotype 19A carriage isolates from 318 in the 2-dose group, 66 isolates from 327 in the 2 + 1-dose group, and 33 isolates from 303 in the unvaccinated were collected from 6 weeks through 24 months. The cumulative proportion who tested positive for new nasopharyngeal serotype 19A acquisition from 6 through 24 months of age was significantly higher in those having received the 2 + 1-dose PCV-7 schedule (16.2%; 95% confidence interval [CI], 12.6%-20.6%) vs those who were unvaccinated (9.2%; 95% CI, 6.5%-13.0%; relative risk [RR], 1.75; 95% CI, 1.14-2.70) but not after a 2-dose schedule (13.2%; 95% CI, 9.9%-17.4%; RR, 1.43; 95% CI, 0.91-2.25). There were 28 different sequence types identified, including 6 new types. The proportion of children with new 19A acquisition who had used antibiotics in the last 6 months (18.7%) did not differ among groups. Five isolates were penicillin-intermediate susceptible and another 3 were nonsusceptible to erythromycin and azithromycin, all in the vaccine groups. Conclusion A 2 + 1-dose PCV-7 schedule was associated with an increase in serotype 19A nasopharyngeal acquisition compared with unvaccinated controls

Nasopharyngeal colonization elicits antibody responses to staphylococcal and pneumococcal proteins that are not associated with a reduced risk of subsequent carriage

Knowledge of the immunological correlates of Staphylococcus aureus and Streptococcus pneumoniae colonization is required for the search for future protein vaccines. We evaluated natural antibody le

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

Variability and Diversity of Nasopharyngeal Microbiota in Children: A Metagenomic Analysis

The nasopharynx is the ecological niche for many commensal bacteria and for potential respiratory or invasive pathogens like Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis. Disturbance of a balanced nasopharyngeal (NP) microbiome might be involved in the onset of symptomatic infections with these pathogens, which occurs primarily in fall and winter. It is unknown whether seasonal infection patterns are associated with concomitant changes in NP microbiota. As young children are generally prone to respiratory and invasive infections, we characterized the NP microbiota of 96 healthy children by barcoded pyrosequencing of the V5–V6 hypervariable region of the 16S-rRNA gene, and compared microbiota composition between children sampled in winter/fall with children sampled in spring. The approximately 1000000 sequences generated represented 13 taxonomic phyla and approximately 250 species-level phyla types (OTUs). The 5 most predominant phyla were Proteobacteria (64%), Firmicutes (21%), Bacteroidetes (11%), Actinobacteria (3%) and Fusobacteria (1,4%) with Moraxella, Haemophilus, Streptococcus, Flavobacteria, Dolosigranulum, Corynebacterium and Neisseria as predominant genera. The inter-individual variability was that high that on OTU level a core microbiome could not be defined. Microbiota profiles varied strongly with season, with in fall/winter a predominance of Proteobacteria (relative abundance (% of all sequences): 75% versus 51% in spring) and Fusobacteria (absolute abundance (% of children): 14% versus 2% in spring), and in spring a predominance of Bacteroidetes (relative abundance: 19% versus 3% in fall/winter, absolute abundance: 91% versus 54% in fall/winter), and Firmicutes. The latter increase is mainly due to (Brevi)bacillus and Lactobacillus species (absolute abundance: 96% versus 10% in fall/winter) which are like Bacteroidetes species generally related to healthy ecosystems. The observed seasonal effects could not be attributed to recent antibiotics or viral co-infection

Two randomized trials of effect of live attenuated influenza vaccine on pneumococcal colonization

The human nasopharynx is frequently colonized by Streptococcus pneumoniae (the pneumococcus), serving as the reservoir for transmission, a state which necessarily precedes invasive pneumococcal infection. Influenza infection increases pneumococcal colonization density and dysregulates host immune responses, increasing the risk of secondary bacterial pneumonia and death

Prior upregulation of interferon pathways in the nasopharynx impacts viral shedding following live attenuated influenza vaccine challenge in children.

In children lacking influenza-specific adaptive immunity, upper respiratory tract innate immune responses may influence viral replication and disease outcome. We use trivalent live attenuated influenza vaccine (LAIV) as a surrogate challenge model in children aged 24-59 months to identify pre-infection mucosal transcriptomic signatures associated with subsequent viral shedding. Upregulation of interferon signaling pathways prior to LAIV is significantly associated with lower strain-specific viral loads (VLs) at days 2 and 7. Several interferon-stimulated genes are differentially expressed in children with pre-LAIV asymptomatic respiratory viral infections and negatively correlated with LAIV VLs. Upregulation of genes enriched in macrophages, neutrophils, and eosinophils is associated with lower VLs and found more commonly in children with asymptomatic viral infections. Variability in pre-infection mucosal interferon gene expression in children may impact the course of subsequent influenza infections. This variability may be due to frequent respiratory viral infections, demonstrating the potential importance of mucosal virus-virus interactions in children

Deep Sequencing Analyses of Low Density Microbial Communities: Working at the Boundary of Accurate Microbiota Detection

Introduction: Accurate analyses of microbiota composition of low-density communities (10 3 –10 4 bacteria/sample) can be challenging. Background DNA from chemicals and consumables, extraction biases as well as differences in PCR efficiency can significantly interfere with microbiota assessment. This study was aiming to establish protocols for accurate microbiota analysis at low microbial density. Methods: To examine possible effects of bacterial density on microbiota analyses we compared microbiota profiles of seria