Natural carriage of Streptococcus pneumoniae is associated with increased experimental pneumococcal carriage but reduced conjugate vaccine efficacy in a human challenge model.

BACKGROUND: In Malawi, the national pneumococcal conjugate vaccine (PCV13) demonstrated less herd immunity than the USA, likely due to higher natural pneumococcal carriage rates. We assessed PCV13 efficacy against experimental pneumococcal carriage in healthy Malawian adults. We explored how natural carriage (pneumococcal carriage of any other serotype apart from 6B) influenced experimental carriage rates and vaccine efficacy. METHODS: Healthy adults aged 18-40 were randomly assigned PCV13 (n=98) or saline (n=106), followed by intranasal SPN 6B inoculation at 20,000 (n=40), 80,000 (n=74), or 160,000 (n=90) CFU/100µl, 28 days post-vaccination. We evaluated natural and experimental pneumococcal carriage before and after vaccination on days 2, 7, and 14 post-inoculation using culture and multiplex qPCR targeting lytA/cpsA genes and compared carriage rates by vaccination status. RESULTS: Of 204 participants, 19.6% (40) exhibited experimental carriage, detected by culture and 25.5% (52) by qPCR. Vaccinated individuals had lower experimental carriage rates (10.2%, n=10/98) compared to the placebo group (28.3%, n=30/106). This difference in vaccine efficacy was more pronounced in participants without natural carriage (PCV13=8% n=6/75 vs. placebo=25.9%, n=21/81) compared to those with natural carriage (PCV13=14.8%, n=4/27 vs. placebo=26.5%, n=9/34). Using a log-binomial model, vaccine effectiveness (VE) was 62%, whether assessed by culture or qPCR. Natural carriers had a lower VE of 52% compared to participants with no natural carriage (VE=69%). CONCLUSION: We have shown that PCV13 VE estimate (62%) is robust whether carriage is assessed by culture or qPCR. PCV13 had lower VE in natural carriers compared to those without natural carriage at the inoculation visit.

Serological profiling of pneumococcal proteins reveals unique patterns of acquisition, maintenance and waning of antibodies throughout life.

Streptococcus pneumoniae is a leading cause of morbidity and mortality in children and older adults. Yet knowledge on the development of pneumococcal protein-specific antibody responses throughout life is limited. To investigate this, we measured serum IgG levels to 55 pneumococcal proteins in 11-month old infants (n=73), 24-month old children (n=101), parents (n=99), adults without children <6 years of age (n= 99) and older adults aged >60 years (n=100). Our findings revealed low IgG levels in infancy, with distinct development patterns peaking in adults. A decrease in levels was observed for 27 antigens towards older age. Adults and older adults had increased IgG levels during pneumococcal carriage and at increased exposure risk to S. pneumoniae. Carriage was a stronger predictor than exposure or age for antibody responses. These findings highlight the dynamic nature of naturally acquired humoral immunity to pneumococcal proteins throughout life, offering insights for age-targeted interventions.

Streptococcus pneumoniae colonization in health care professionals at a tertiary university pediatric hospital.

Streptococcus pneumoniae is a commensal of the human upper respiratory tract. In certain cases, it can lead to serious invasive infections peaking in very young children and the elderly. Especially young children are frequent carriers and are thus regarded as the reservoir for horizontal transmission of pneumococci. This is the first study evaluating pneumococcal colonization patterns in healthcare professionals working in a tertiary care pediatric hospital, including carriage prevalence, serotype distribution, and risk factors for carriage. One oropharyngeal and one nasal swab per individual were directly plated onto appropriate agar plates and conventional culture was used for bacterial identification. Pneumococcal isolates underwent serotyping using Neufeld's Quellung reaction with type-specific antisera. Additional nasal and oropharyngeal swabs were taken for qPCR analysis targeting lytA. In total, 437 individuals were enrolled. S. pneumoniae was isolated in 4.8% (21/437) of the study cohort using conventional culture and in 20.1% (88/437) of subjects using qPCR. Independent risk factors for pneumococcal carriage were living in the same household with children under 8 years of age and being aged 36-45 years with a carriage prevalence reaching 11.6% (vs. 2.9%, p = 0.002) and 6.7% (vs. 4.3%, p = 0.029), respectively. The most common serotypes were 6C and 3. A total of 71.4% (15/21) of the detected serotypes are not included in any currently available pneumococcal vaccine; 28.6% (6/21) of the carried serotypes are included in the PCV13 vaccine. We found a relevant amount of pneumococcal carriage bearing the potential risk of horizontal in-hospital transmission.

Effect of maternal vitamin D supplementation on nasal pneumococcal acquisition, carriage dynamics and carriage density in infants in Dhaka, Bangladesh.

BACKGROUND: Invasive pneumococcal disease is a major cause of infant morbidity and death worldwide. Vitamin D promotes anti-pneumococcal immune responses in vitro, but whether improvements in infant vitamin D status modify risks of nasal pneumococcal acquisition in early life is not known. METHODS: This is a secondary analysis of data collected in a trial cohort in Dhaka, Bangladesh. Acute respiratory infection (ARI) surveillance was conducted from 0 to 6 months of age among 1060 infants of women randomized to one of four pre/post-partum vitamin D dose combinations or placebo. Nasal swab samples were collected based on standardized ARI criteria, and pneumococcal DNA quantified by qPCR. Hazards ratios of pneumococcal acquisition and carriage dynamics were estimated using interval-censored survival and multi-state modelling. RESULTS: Pneumococcal carriage was detected at least once in 90% of infants by 6 months of age; overall, 69% of swabs were positive (2616/3792). There were no differences between any vitamin D group and placebo in the hazards of pneumococcal acquisition, carriage dynamics, or carriage density (p > 0.05 for all comparisons). CONCLUSION: Despite in vitro data suggesting that vitamin D promoted immune responses against pneumococcus, improvements in postnatal vitamin D status did not reduce the rate, alter age of onset, or change dynamics of nasal pneumococcal colonization in early infancy. Trial registration Registered in ClinicalTrials.gov with the registration number of NCT02388516 and first posted on March 17, 2015.

Persistent and Emerging Pneumococcal Carriage Serotypes in a Rural Gambian Community After 10 Years of Pneumococcal Conjugate Vaccine Pressure.

BACKGROUND: The continuing impact of pneumococcal conjugate vaccines (PCVs) in regions with high pneumococcal transmission is threatened by the persistence of vaccine serotypes (VTs) and the emergence of nonvaccine serotypes (NVTs). METHODS: In 2016, we conducted a cross-sectional carriage survey (CSS5) in a community where PCV7 was first introduced in 2006 during a cluster-randomized trial conducted before nationwide introduction of PCV7 (2009) and PCV13 (2011). We estimated prevalence of PCV13 VT and NVT by age and compared these with earlier surveys before (CSS0), during (CSS1-3), and after the trial but before PCV13 (CSS4). Genomic analysis was conducted for the nontypeable pneumococci. RESULTS: Prevalence of PCV13 VT carriage decreased during the 10 years between CSS0 and CSS5 across all age groups (67.6% to 13.5%, P < .001; 59.8% to 14.4%, P < .001; 43.1% to 17.9%, P < .001; and 24.0% to 5.1%, P < .001, in <2, 2-4, 5-14, and ≥15 years, respectively). However, there was no difference between CSS4 and CSS5 in children ≥2 years and adults (children <2 years, no data). The prevalence of PCV13 NVT increased between CSS0 and CSS5 for children <2 years but decreased in older children and adults. In CSS5, serotypes 3, 6A, and 19F were the most common VT and nontypeable isolates were the most common NVT. Among nontypeable isolates, 73.0% lost the ability to express a capsule. Of these, 70.8% were from a VT background. CONCLUSIONS: The decrease in PCV13 VT that has occurred since the introduction of PCV13 appears to have plateaued. Significant carriage of these serotypes remains in all age groups.

Tissue microbiota in nasopharyngeal adenoid and its association with pneumococcal carriage.

The microbial colonization in the nasopharynx is a prerequisite for the onset of infectious diseases. For successful infection, pathogens should overcome host defenses as well as compete effectively with the resident microbiota. Hence, elucidating the richness and diversity of the microbiome at the site of pathogen colonization is pivotal. Here, we investigated the adenoidal tissue microbiota collected through adenoidectomy to evaluate the impact of Streptococcus pneumoniae. Prospectively, children with sleep-disordered breathing (SDB) and otitis media with effusion (OME) were enrolled. During adenoidectomy, the nasopharyngeal swab and adenoid tissues were collected to determine the pneumococcal carriage and tissue microbiota, using multiplex PCR and 16S ribosomal RNA (16S rRNA) pyrosequencing. A total of 66 pediatric patients comprising 38 children with SDB and 28 children with OME were enrolled. There was no difference between the bacterial cultures from the surface of the nasopharyngeal adenoid in the SDB and OME groups. Thirty-four samples (17 SDB and 17 OME) underwent 16S rRNA pyrosequencing and fulfilled the criteria for further analysis. The Shannon diversity index for the samples from the SDB patients was found to be higher than that observed for the samples from OME patients, although the difference was not significant (p = 0.095). The Shannon diversity index for the samples negative for the pneumococcal carriage was significantly higher than that for the samples positive for pneumococcal carriage (p = 0.038). Alloprevotella, Staphylococcus, Moraxella, and Neisseriaceae were significantly dominant in the samples positive for the pneumococcal carriage. Dialister was significantly less present in the adenoid tissue positive for the pneumococcal carriage. Streptococcus pneumoniae, one of the most common pathogens of the airway, significantly influences the composition and diversity of the microbiota in the nasopharyngeal adenoid. Thus, bacterial community analysis based on 16S rRNA pyrosequencing allows for better understanding of the relationship between the adenoidal microbial communities.

Impact of 10-Valent Pneumococcal Conjugate Vaccine Introduction on Pneumococcal Carriage and Antibiotic Susceptibility Patterns Among Children Aged <5 Years and Adults With Human Immunodeficiency Virus Infection: Kenya, 2009-2013.

BACKGROUND: Kenya introduced 10-valent pneumococcal conjugate vaccine (PCV10) among children <1 year in 2011 with catch-up vaccination among children 1-4 years in some areas. We assessed changes in pneumococcal carriage and antibiotic susceptibility patterns in children <5 years and adults. METHODS: During 2009-2013, we performed annual cross-sectional pneumococcal carriage surveys in 2 sites: Kibera (children <5 years) and Lwak (children <5 years, adults). Only Lwak had catch-up vaccination. Nasopharyngeal and oropharyngeal (adults only) swabs underwent culture for pneumococci; isolates were serotyped. Antibiotic susceptibility testing was performed on isolates from 2009 and 2013; penicillin nonsusceptible pneumococci (PNSP) was defined as penicillin-intermediate or -resistant. Changes in pneumococcal carriage by age (<1 year, 1-4 years, adults), site, and human immunodeficiency virus (HIV) status (adults only) were calculated using modified Poisson regression, with 2009-2010 as baseline. RESULTS: We enrolled 2962 children (2073 in Kibera, 889 in Lwak) and 2590 adults (2028 HIV+, 562 HIV-). In 2013, PCV10-type carriage was 10.3% (Lwak) to 14.6% (Kibera) in children <1 year and 13.8% (Lwak) to 18.7% (Kibera) in children 1-4 years. This represents reductions of 60% and 63% among children <1 year and 52% and 60% among children 1-4 years in Kibera and Lwak, respectively. In adults, PCV10-type carriage decreased from 12.9% to 2.8% (HIV+) and from 11.8% to 0.7% (HIV-). Approximately 80% of isolates were PNSP, both in 2009 and 2013. CONCLUSIONS: PCV10-type carriage declined in children <5 years and adults post-PCV10 introduction. However, PCV10-type and PNSP carriage persisted in children regardless of catch-up vaccination.

Persistence of Nasopharyngeal Pneumococcal Vaccine Serotypes and Increase of Nonvaccine Serotypes Among Vaccinated Infants and Their Mothers 5 Years After Introduction of Pneumococcal Conjugate Vaccine 13 in The Gambia.

BACKGROUND: The widespread use of pneumococcal conjugate vaccine (PCV) has brought about a dramatic decrease in pneumococci of vaccine serotypes (VTs) but nonvaccine serotypes (NVTs) have emerged. METHODS: We conducted a cross-sectional survey (CSS) among infants who received 3 doses of 13-valent PCV (PCV13) and their mothers 5 years (CSS3) after PCV13 introduction. Nasopharyngeal swab samples were collected and cultured for isolation of Streptococcus pneumoniae. Whole-genome sequencing of the nontypeable strains was performed. Data were compared with those from 2 previous surveys conducted before PCV13 introduction (CSS1) and 1 year later (CSS2). RESULTS: Among infants, VT carriage decreased from 33.3% (113/339) in CSS1 to 11.4% (40/351) in CSS3 (P = .001) while NVTs increased from 53.1% (180/339) in CSS1 to 74.4% (261/351) in CSS3 (P < .001). Among mothers, there was a significant decrease in VTs between CSS2 8.4% (29/347) and CSS3 5.6% (19/342) (P = .006). NVTs increased from 16.6% (55/331) in CSS1 to 32.2% (110/342) in CSS3 (P < .001). In CSS3, the most prevalent VTs were 7F in infants and 3 in mothers, and the most prevalent NVTs were serogroup 16 and nontypeables, respectively. Genomic analysis showed that VTs were more likely than NVTs to lose their ability to express the capsule. CONCLUSIONS: Five years after PCV13 introduction, we show both direct (infants) and indirect effects (mothers) of the vaccine, while NVT replacement has occurred in both groups. Ongoing circulation of VTs warrants further study of their relevance in any consideration of a reduced dose schedule.

Impact of the addition of azithromycin to antimalarials used for seasonal malaria chemoprevention on antimicrobial resistance of Streptococcus pneumoniae.

OBJECTIVE: A trial was conducted in Burkina Faso and Mali to investigate whether addition of azithromycin to the antimalarials used for seasonal malaria chemoprevention reduces mortality and hospital admissions of children. We tested the sensitivity of nasal isolates of Streptococcus pneumoniae obtained during this trial to azithromycin and other antibiotics. METHODS: Azithromycin or placebo was administered monthly, in combination with the antimalarials used for seasonal malaria chemoprevention, for four months, over the annual malaria transmission seasons of 2014, 2015, and 2016. Nasopharyngeal swabs were collected from 2773 Burkinabe and 2709 Malian children on seven occasions: in July and December each year prior to and after drug administration, and at a final survey in early 2018. Pneumococci were isolated from nasopharyngeal swabs and tested for sensitivity to azithromycin and other antibiotics. RESULTS: A total of 5482 samples were collected. In Burkina Faso, the percentage of pneumococcal isolates resistant to azithromycin among children who had received it increased from 4.9% (95% CI: 2.4%, 9.9%) before the intervention to 25.6% (95% CI: 17.6%, 35.7%) afterward. In Mali, the increase was from 7.6% (95% CI: 3.8%, 14.4%) to 68.5% (95% CI: 55.1%, 79.4%). The percentage of resistant isolates remained elevated (17.7% (95% CI: 11.1%, 27.1%) in Burkina Faso and 19.1% (95% CI: 13.5%, 26.3%) in Mali) among children who had received azithromycin 1 year after stopping the intervention. An increase in resistance to azithromycin was also observed in children who had received a placebo but it was less marked. CONCLUSION: Addition of azithromycin to the antimalarial combination used for seasonal malaria chemoprevention was associated with an increase in resistance of pneumococci to azithromycin and erythromycin, which persisted 1 year after the last administration of azithromycin.

OBJECTIF: Un essai a été mené au Burkina Faso et au Mali pour investiguer si l'addition d'azithromycine aux antipaludéens utilisés dans le cadre de la chimioprévention du paludisme saisonnier réduisait la mortalité et les hospitalisations d'enfants. Nous avons testé la sensibilité à l'azithromycine et à d'autres antibiotiques pour les isolats nasaux de Streptococcus pneumoniae obtenus lors de cet essai. MÉTHODES: L'azithromycine ou un placebo a été administré mensuellement, en association avec les antipaludéens utilisés pour la chimioprévention du paludisme saisonnier, pendant 4 mois, durant les saisons de transmission annuelle du paludisme de 2014, 2015 et 2016. Des échantillons nasopharyngés ont été prélevés sur écouvillons chez 2.773 enfants burkinabés et 2.709 enfants maliens lors de 7 occasions: en juillet et en décembre chaque année avant et après l'administration du médicament, ainsi que lors d'une surveillance finale au début de 2018. Les pneumocoques ont été isolés à partir d'écouvillons nasopharyngés et soumis à des tests de sensibilité à l'azithromycine et à d'autres antibiotiques. RÉSULTATS: 5.482 échantillons ont été collectés. Au Burkina Faso, le pourcentage d'isolats de pneumocoque résistants à l'azithromycine chez les enfants qui l'avaient reçu était passé de 4,9% (IC95%: 2,4%, 9,9%) avant l'intervention à 25,6% (IC95%: 17,6-35,7%) après. Au Mali, l'augmentation est passée de 7,6% (IC95%: 3,8-14,4%) à 68,5% (IC95%: 55,1-79,4%). Le pourcentage d'isolats résistants est resté élevé (17,7% (IC95%: 11,1-27,1%) au Burkina Faso et 19,1% (IC95%: 13,5-26,3%) au Mali) chez les enfants ayant reçu l'azithromycine un an après arrêter l'intervention. Une augmentation de la résistance à l'azithromycine a également été observée chez les enfants ayant reçu un placebo, mais elle était moins marquée. CONCLUSION: L'ajout d'azithromycine à la combinaison antipaludique utilisée pour la chimioprévention du paludisme saisonnier était associé à une augmentation de la résistance du pneumocoque à l'azithromycine et à l'érythromycine, qui persistait un an après la dernière administration d'azithromycine.

Why are people with asthma susceptible to pneumonia? A review of factors related to upper airway bacteria.

Asthma and pneumonia are common respiratory conditions globally, affecting individuals of all ages. Streptococcus pneumoniae is the predominant bacterial cause of pneumonia, with nasopharyngeal carriage an important step towards invasive and pulmonary disease. Vaccines provide individual protection, and also prevent nasopharyngeal carriage, providing herd immunity. Asthma is associated with an increased risk of pneumonia, but there is limited information on the underlying mechanism of this predisposition. Both asthma and its treatment may conceivably alter propensity to, and density of, carriage through an altered epithelial microenvironment driven by disease-related inflammation or treatment-related immunomodulation, for example with inhaled corticosteroids. The relative importance of these factors could impact the efficacy of vaccines in this vulnerable patient population. In this review, we summarize the evidence for an increased risk of pneumonia in asthma, and discuss factors affecting nasopharyngeal carriage in the context of current guidelines for pneumococcal vaccination.

Nasopharyngeal carriage of Streptococcus pneumoniae in children under 5 years of age before introduction of pneumococcal vaccine (PCV10) in urban and rural districts in Pakistan.

BACKGROUND: Benefits of pneumococcal conjugate vaccine programs have been linked to the vaccine's ability to disrupt nasopharyngeal carriage and transmission. The 10-valent pneumococcal vaccine (PCV10) was included in the Expanded Program on Immunization (EPI) in Sindh, Pakistan in February 2013. This study was carried out immediately before PCV10 introduction to establish baseline pneumococcal carriage and prevalent serotypes in young children and to determine if carriage differed in urban and rural communities. METHODS: Nasopharyngeal specimens were collected from a random sample of children 3-11 and 12-59 months of age in an urban community (Karachi) and children 3-11 months of age in a rural community (Matiari). Samples were processed in a research laboratory in Karachi. Samples were transported in STGG media, enriched in Todd Hewitt broth, rabbit serum and yeast extract, cultured on 5% sheep blood agar, and serotyped using the CDC standardized sequential multiplex PCR assay. Serotypes were categorized into PCV10-type and non-vaccine types. RESULTS: We enrolled 670 children. Pneumococci were detected in 73.6% and 79.5 % of children in the infant group in Karachi and Matiari, respectively, and 78.2% of children 12 to 59 months of age in Karachi. In infants, 38.9% and 33.5% of those carrying pneumococci in Karachi and Matiari, respectively, had PCV10 types. In the older age group in Karachi, the proportion was 30.7%, not significantly different from infants. The most common serotypes were 6A, 23F, 19A, 6B and 19F. CONCLUSION: We found that about 3 of 4 children carried pneumococci, and this figure did not vary with age group or urban or rural residence. Planned annual surveys in the same communities will inform change in carriage of PCV10 serotype pneumococci after the introduction and uptake of PCV10 in these communities.

Imputing the Direct and Indirect Effectiveness of Childhood Pneumococcal Conjugate Vaccine Against Invasive Pneumococcal Disease by Surveying Temporal Changes in Nasopharyngeal Pneumococcal Colonization.

The limited capability in most low- to middle-income countries to study the benefit of pneumococcal conjugate vaccine (PCV) in protecting against invasive pneumococcal disease (IPD) calls for alternate strategies to assess this. We used a mathematical model to predict the direct and indirect effectiveness of PCV by analyzing serotype-specific colonization prevalence and IPD incidence prior to and following childhood PCV immunization in South Africa. We analyzed IPD incidence from 2005 to 2012 and colonization studies undertaken in human immunodeficiency virus (HIV)-uninfected and HIV-infected child-mother dyads from 2007 to 2009 (pre-PCV era), in 2010 (7-valent PCV era), and in 2012 (13-valent PCV era). We compared the model-predicted changes in IPD incidence with observed changes in IPD incidence, according to HIV status, in children aged 3 months-5 years and in women aged 18-45 years. We observed reductions in vaccine-serotype colonization and IPD due to vaccine serotypes among children and women after PCV introduction. Using the changes in vaccine-serotype colonization data, the model-predicted changes in vaccine-serotype IPD incidence rates were similar to the observed changes in PCV-unvaccinated children and adults, but not among children under age 24 months. Surveillance of colonization prior to and following PCV use can be used to impute the indirect protection afforded by PCV in unvaccinated age groups, including those in high-HIV-prevalence settings.

Polysaccharide-Specific Memory B Cells Predict Protection against Experimental Human Pneumococcal Carriage.

RATIONALE: We have previously demonstrated that experimental pneumococcal carriage enhances immunity and protects healthy adults against carriage reacquisition after rechallenge with a homologous strain. OBJECTIVES: To investigate the role of naturally acquired pneumococcal protein and polysaccharide (PS)-specific immunity in protection against carriage acquisition using a heterologous challenge model. METHODS: We identified healthy volunteers that were naturally colonized with pneumococcus and, after clearance of their natural carriage episode, challenged them with a heterologous 6B strain. In another cohort of volunteers we assessed 6BPS-specific, PspA-specific, and PspC-specific IgG and IgA plasma and memory B-cell populations before and 7, 14, and 35 days after experimental pneumococcal inoculation. MEASUREMENTS AND MAIN RESULTS: Heterologous challenge with 6B resulted in 50% carriage among volunteers with previous natural pneumococcal carriage. Protection from carriage was associated with a high number of circulating 6BPS IgG-secreting memory B cells at baseline. There were no associations between protection from carriage and baseline levels of 6BPS IgG in serum or nasal wash, PspA-specific, or PspC-specific memory B cells or plasma cells. In volunteers who did not develop carriage, the number of circulating 6BPS memory B cells decreased and the number of 6BPS plasma cells increased postinoculation. CONCLUSIONS: Our data indicate that naturally acquired PS-specific memory B cells, but not levels of circulating IgG at time of pneumococcal exposure, are associated with protection against carriage acquisition.

Pneumococcal colonization in older adults.

BACKGROUND: Little is known about pneumococcal carrier states in older adults. The main aim of this study was to evaluate pneumococcal colonization patterns among older adults in two centres in Milan, Italy, before the widespread use of the 13-valent pneumococcal vaccine (PCV13) in this age group, to investigate demographic and clinical features that are associated with pneumococcal colonization and to estimate the potential coverage offered by PCV13. RESULTS: Among 417 adults ≥65 years old (171, 41.1 %, ≥75 years), 41 (9.8 %) were pneumococcal carriers. Univariate and multivariate analyses revealed that pneumococcal colonization was significantly less common among individuals with underlying co-morbidities than among those without (odds ratio [OR] 0.453, 95 % confidence interval [CI] 0.235-0.875, p = 0.018; adjusted OR 0.503, 95 % CI 0.255-0.992, p = 0.047). Moreover, among these patients, those with cardiac disease had a significantly lower risk of colonization (OR 0.308, 95 % CI 0.119-0.795, p = 0.015; adjusted OR 0.341, 95 % CI 0.13-0.894, p = 0.029). Only one vaccinated subject who received 23-valent polysaccharide pneumococcal vaccine (PPV23) was colonized. Twenty-five (89.3 %) of the subjects who were <75 years old and 9 (75.0 %) of those who were ≥75 years old were colonized by at least one of the serotypes that is included in PCV13, with serotype 19 F being the most common. Respiratory allergies as well as overall co-morbidities were more common in subjects who were positive for only non-PCV13 serotypes compared with negative subjects and those who were carriers of only PCV13 serotypes. CONCLUSIONS: Although this study included a relatively small number of subjects and has been performed in a limited geographic setting, results showed that pneumococcal colonization in older people is common, and the monitoring of carriers can offer useful information about the circulation of this pathogen among older people and the potential protective effect of pneumococcal vaccines. Because the colonization in most cases involves the strains that are included in PCV13, this vaccine could be useful in the prevention of pneumococcal infections in the overall population of older people. In subjects with respiratory allergies and in those with co-morbidities, the addition of the PPV23 to PCV13 should be recommended. Due to the low vaccination coverage, urgent educational programmes are required to inform older adults and their medical doctors of the risks of pneumococcal infection and the efficacy and safety of the available pneumococcal vaccines.

Risk factors for nasopharyngeal carriage of Streptococcus pneumoniae and effects of a hygiene intervention: repeated cross-sectional cohort study at day care centres.

BACKGROUND: Day care attendance and antibiotic consumption are major risk factors for carriage of antibiotic-susceptible and non-susceptible pneumococci. We describe the nasopharyngeal carriage of antibiotic-susceptible and non-susceptible pneumococci among children at day care centres (DCCs), analyse the association of potential risk factors with carriage, and examine the effects of a hygiene intervention on carriage. METHODS: Thirty DCCs in 2 communities were included in a cohort intervention trial. Nasopharyngeal cultures and information on the children were obtained every 6 months. The study lasted 2.5 y and the hygiene intervention was introduced at half of the DCCs during the last 1.5 y of the study. The results were analysed using a mixed effects logistic regression model. RESULTS: A total of 5663 cultures were obtained from 2399 children, of which 55.6% grew pneumococci. Of the pneumococci, 27.9% were penicillin-non-susceptible (PNSP). The hygiene intervention was associated with a decreased risk of pneumococcal carriage, but this did not reach statistical significance for PNSP carriage. Pneumococcal and PNSP carriage was negatively associated with age, varied significantly between DCCs, and was positively associated with the number of preceding colds. Individual antibiotic use (mainly penicillin/amoxicillin) at the time of sampling and/or during the preceding month was associated with a decreased risk of pneumococcal and PNSP carriage. Individual use of cephalosporins was associated with an increased risk of carriage of penicillin and TMP-SMX-non-susceptible pneumococci. CONCLUSION: The hygiene intervention at the DCCs reduced the risk of pneumococcal carriage and the individual use of antibiotics was found to affect carriage in a complex manner.

Long-term impact of 10-valent pneumococcal conjugate vaccine in Kenya: Nasopharyngeal carriage among children in a rural and an urban site six years after introduction.

BACKGROUND: Kenya introduced Synflorix™ (GlaxoSmithKline, PCV10-GSK), a 10-valent pneumococcal conjugate vaccine, in 2011, using three primary doses and, in select areas, catch-up campaigns. Surveys conducted 1-2 years post-introduction showed a stable prevalence of pneumococcal colonization, with declines in vaccine-type carriage. However, little is known about the long-term impact of PCV10-GSK in Kenya. METHODS: We conducted a cross-sectional survey of pneumococcal carriage among children aged <5 years in November-December 2017 in Kibera (Nairobi informal settlement, no catch-up) and Asembo (rural western Kenya, 2-dose catch-up for children 1-4 years), using the same methods and settings as prior annual surveys from 2009 to 2013. Participants were randomly selected from an ongoing population-based surveillance platform. Nasopharyngeal swabs were frozen in skim milk-tryptone-glucose-glycerin media within 4 h and underwent culture with broth enrichment for pneumococcus. Isolates were serotyped by polymerase chain reaction and Quellung. RESULTS: We enrolled 504 children, including 252 from each site; >90 % of participants had received 3 doses of PCV10-GSK. Pneumococcal colonization was detected in 210 (83.3 %) participants in Kibera and 149 (59.1 %) in Asembo, which was significantly lower than the prevalence observed in 2013 (92.9 % and 85.7 %, respectively). PCV10-GSK serotypes were detected in 35/252 (13.9 %) participants in Kibera and 23/252 (9.1 %) in Asembo, respectively; these prevalences were lower, but not statistically different, from vaccine-type carriage prevalences in 2013 (17.3 % and 13.3 %, respectively). In 2017 in both sites, serotypes 3, 6A, 19A, 19F, and 35B were among the most common serotypes. CONCLUSION: Six years post-PCV10-GSK introduction, the prevalence of pneumococcal carriage among children has decreased, and the impact of PCV10-GSK on vaccine-type carriage has plateaued. Kenya recently changed from PCV10-GSK to Pneumosil™ (Serum Institute of India), a 10-valent PCV that includes serotypes 6A and 19A; these data provide historical context for interpreting changes in vaccine-type carriage following the PCV formulation switch.

Nasopharyngeal Carriage of Streptococcus pneumoniae in Tunisian Healthy under-Five Children during a Three-Year Survey Period (2020 to 2022).

We aimed to assess the prevalence of nasopharyngeal pneumococcal carriage and to determine serotype distribution, antibiotic susceptibility patterns, and evolutionary dynamics of Streptococcus pneumoniae isolates in healthy under-five children. Nasopharyngeal swabs were collected from healthy children over three survey periods between 2020 and 2022. All pneumococcal isolates were serotyped and tested for antimicrobial susceptibility. A total of 309 S. pneumoniae isolates were collected, with an overall prevalence of nasopharyngeal pneumococcal carriage of 24.4% (CI95%: [22-26.8%]). These isolates were classified into 25 different serotypes. The most common serotypes were 14 (14.9%), 19F (12%), 6B (10.4%), and 23F (7.4%), which are covered by the PCV10 vaccine, as well as 19A (8.4%) and 6A (7.8%), which are covered by the PCV13 vaccine. A significant decrease in the proportion of serotype 19F (p = 0.001) and an increase in serotypes 19A (p = 0.034) and 6A (p = 0.029) were observed between the three survey periods. Multidrug resistance (MDR) was noted for 56.6% of the isolates. A significant association with antimicrobial resistance was observed for the most frequent serotypes, mainly serotype 19A. In conclusion, one-quarter of healthy under-five children in Tunisia carried S. pneumoniae in their nasopharynx. A dominance of vaccine serotypes significantly associated with antimicrobial resistance was recorded.

Experimental pneumococcal carriage in people living with HIV in Malawi: the first controlled human infection model in a key at-risk population.

Background: As well as suffering a high burden of pneumococcal disease people living with HIV (PLHIV) may contribute to community transmission in sub-Saharan African (sSA) settings. Pneumococcal vaccination is not currently offered to PLHIV in sSA but may prevent disease and reduce transmission. More evidence of vaccine effectiveness against carriage in PLHIV is needed. An Experimental Human Pneumococcal Carriage model (EHPC) has been safely and acceptably used in healthy adults in Malawi to evaluate pneumococcal vaccines against carriage and to identify immune correlates of protection from carriage. This study will establish the same model in PLHIV and will be the first controlled human infection model (CHIM) in this key population. Methods: Healthy participants with and without HIV will be inoculated intranasally with Streptococcus pneumoniae serotype 6B. Sequential cohorts will be challenged with increasing doses to determine the optimal safe challenge dose to establish experimental carriage. Nasal fluid, nasal mucosal, and blood samples will be taken before inoculation and on days 2, 7, 14, and 21 following inoculation to measure pneumococcal carriage density and identify immune correlates of protection from carriage. The vast majority of natural pneumococcal carriage events in PLHIV do not result in invasive disease and no invasive disease is expected in this study. However, robust participant safety monitoring is designed to identify signs of invasive disease early should they develop, and to implement treatment immediately. Participants will complete a Likert-style questionnaire at study-end to establish acceptability. Interpretations: We expect the EHPC model to be safely and acceptably implemented in PLHIV. The CHIM can then be used to accelerate pneumococcal vaccine evaluations in this population, and an evidence-based pneumococcal vaccination policy for PLHIV in sSA.

Pneumococcal carriage and changes in serotype distribution post- PCV13 introduction in children in Matiari, Pakistan.

BACKGROUND: In early 2021, the 10-valent Pneumococcal conjugate vaccine (PCV10) was replaced with 13-valent (PCV13) by the federal directorate of immunization (FDI), Pakistan. We assessed the impact of a higher valent vaccine, PCV13, on the serotype distribution of nasopharyngeal carriage in rural Pakistan. METHODS: Children <2 years were randomly selected from two rural union councils of Matiari, Sindh in Pakistan between September-October,2022. Clinical, sociodemographic and vaccination histories were recorded. Nasopharyngeal swabs were collected and processed at Infectious Disease Research Laboratory, Aga Khan University, Karachi. Whole genome sequencing was performed on the culture positive isolates. RESULTS: Of the 200 children enrolled, pneumococcus was detected in 140(70 %) isolates. Majority of age-eligible children (60.1 %,110/183) received 3 PCV13 doses. PCV10 carriage declined from 13.2 %(78/590) in 2017/18 to 7.2 % (10/140) in 2022, additional PCV13 serotypes (3, 6A/6C and 19A) decreased from 18.5 %(109/590) to 11.4 %(16/140) while non-PCV13 serotypes increased from 68.3 %(403/590) to 81.4 %(114/140). There were 88.5 %(n = 124), 80.7 %(n = 113), 55.0 %(n = 77), and 46.0 %(n = 65) isolates predicted to be resistant to cotrimoxazole, penicillin(meningitis cut-off), tetracycline, and erythromycin respectively. CONCLUSION: Replacing PCV10 with PCV13 rapidly decreased prevalence of PCV13 carriage among vaccinated children in Matiari, Pakistan. Vaccine-driven selection pressure may have been responsible for the increase of non-PCV13 serotypes.

RSV and rhinovirus increase pneumococcal carriage acquisition and density, whereas nasal inflammation is associated with bacterial shedding.

Epidemiological studies report the impact of co-infection with pneumococcus and respiratory viruses upon disease rates and outcomes, but their effect on pneumococcal carriage acquisition and bacterial load is scarcely described. Here, we assess this by combining natural viral infection with controlled human pneumococcal infection in 581 healthy adults screened for upper respiratory tract viral infection before intranasal pneumococcal challenge. Across all adults, respiratory syncytial virus (RSV) and rhinovirus asymptomatic infection confer a substantial increase in secondary infection with pneumococcus. RSV also has a major impact on pneumococcal density up to 9 days post challenge. We also study rates and kinetics of bacterial shedding through the nose and oral route in a subset. High levels of pneumococcal colonization density and nasal inflammation are strongly correlated with increased odds of nasal shedding as opposed to cough shedding. Protection against respiratory viral infections and control of pneumococcal density may contribute to preventing pneumococcal disease and reducing bacterial spread.