Factors associated with pneumococcal nasopharyngeal carriage: A systematic review

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.

Pneumococcal carriage and serotype distribution in children with nephrotic syndrome

BACKGROUND

Patients with nephrotic syndrome (NS) are at a higher risk of developing invasive pneumococcal disease (IPD). Pneumococcal carriage studies are helpful tools for detecting potentially infectious serotypes and guiding immunization efforts. Pneumococcal nasopharyngeal colonization is common, and IPD can easily occur in an immunosuppressed state. Limited information is available regarding the frequency of pneumococcal carriage in individuals with NS. The aim of this study was to evaluate pneumococcal carriage and serotype distribution in children with NS.

METHODS

Pneumococcal carriage was detected by real-time PCR assays from nasopharyngeal swab samples from 98 children with NS, and 100 healthy controls. Isolates were serotyped by real-time PCR.

RESULTS

The pneumococcal carriage rate was 44.9% in children with NS. Regarding the recommendation about pneumococcal immunization in children with NS, the vaccination rate was low. Also, non-PCV13 serotypes have been detected in at least 25% of PCV13-vaccinated children. There is no statistically significant difference in total pneumococcal carriage rate, PCV13 serotype carriage rate, or non-PCV13 serotype carriage rate between children with NS and healthy controls (p > 0.05 for all).

CONCLUSIONS

The pneumococcal carriage rate was similar between children with NS and healthy controls. However, because children with NS have an increased risk for IPD, the serotype distribution of children with NS can demonstrate the improved protection offered by new pneumococcal vaccines. Regular monitoring for IPD is crucial for assessing the evolving sero-epidemiology of pneumococcal infections and evaluating the effectiveness of vaccines for children with NS.

Carriage of Streptococcus pneumoniae in adults hospitalised with community-acquired pneumonia

OBJECTIVES

We aimed to determine the prevalence of and risk factors for nasopharyngeal and oral pneumococcal carriage in adults with community-acquired pneumonia (CAP), and the relationship between carried and disease-causing serotypes.

METHODS

Between 2016 and 2018, nasopharyngeal swabs, oral-fluid, and urine were collected from hospitalised adults recruited into a prospective cohort study of CAP. Pneumococcal carriage was detected by semi-quantitative real-time PCR of direct and culture-enriched nasopharyngeal swabs and culture-enriched oral-fluid. LytA and piaB positive/indeterminate samples underwent semi-quantitative serotype/serogroup-specific real-time-PCR. Serotypes in urine were identified using a 24-valent serotype-specific urinary-antigen assay.

RESULTS

We included 465 CAP patients. Nasopharyngeal carriage was detected in 34/103 (33.0%) swabbed pneumococcal pneumonia patients and oral carriage in 18/155 (12%) of sampled pneumococcal pneumonia patients. Concordance between nasopharyngeal/urine serotypes and oral/urine serotypes was 70.6% and 50% respectively. Serotypes 3 (26%, 22.2%), 8 (19.7%, 19.4%), non-typeable (11.6%, 13.9%) and 19A/F (7.5%, 8.3%) were most prevalent in urine and nasopharyngeal swabs respectively, with non-typeable (35%) and 15A/F (17%) most prevalent in oral-fluid. Pneumococcal carriage was significantly associated with pneumococcal pneumonia (nasopharyngeal adjusted odds ratio [aOR] 8.1, 95% confidence interval [CI] 3.8-17.2; oral aOR 5.5, 95% CI 2.1-13.3). All-cause CAP patients ≥65 years had lower odds of nasopharyngeal carriage (aOR 0.47, 95% CI 0.24-0.91) and current smokers had higher odds of oral carriage (aOR 2.69, 95% CI 1.10-6.60).

CONCLUSIONS

The association between nasopharyngeal carriage and pneumococcal CAP was strong. Adult carriage and disease from serotypes 8 and 19A may support direct protection of adults with PCV vaccines.

Streptococcus pneumoniae carriage, serotypes, genotypes, and antimicrobial resistance trends among children in Portugal, after introduction of PCV13 in National Immunization Program: A cross-sectional study

Streptococcus pneumoniae carriage studies are crucial to monitor changes induced by use of pneumococcal conjugate vaccines and inform vaccination policies. In this cross-sectional study, we examined changes within the pneumococcal population following introduction of PCV13 in 2015 in the National Immunization Program (NIP), in Portugal. In 2018-2020 (NIP-PCV13), we obtained 1450 nasopharyngeal samples from children ≤6 years attending day-care. We assessed serotypes, antimicrobial resistance, and genotypes (MLST and GPSC) and compared findings with earlier periods: 2009-2010 (pre-PCV13), 2011-2012 (early-PCV13), and 2015-2016 (late-PCV13). Pneumococcal carriage prevalence remained stable at 60.2 %. Carriage of PCV13 serotypes was 10.7 %, markedly reduced compared to pre-PCV13 period (47.6 %). The most prevalent PCV13 serotypes were 19F, 3, and 19A all showing a significant decreasing trend compared to the pre-PCV13 period (from 7.1 % to 4.7 %, 10.1 % to 1.8 %, and 14.1 % to 1.8 %, respectively), a notable observation given the described limited effectiveness of PCV13 against serotype 3. Non-vaccinated children and children aged 4-6 years were more likely to carry PCV13 serotypes (2.5-fold, 95 %CI [1.1-5.6], and 2.9-fold, 95 %CI [1.3-6.8], respectively). The most prevalent non-PCV13 serotypes were 15B/C, 11A, 23B, 23A, and NT, collectively accounting for 51.9 % of all isolates. In total, 30.5 % of all pneumococci were potentially covered by PCV20. Resistance to penicillin (low-level) and macrolides increased significantly, from 9.3 % and 13.4 %, respectively, in the late-PCV13 period, to approximately 20 % each, mostly due to lineages expressing non-PCV13 serotypes, nearing pre-PCV13 levels. An expansion of lineages traditionally associated with PCV13 serotypes, like CC156-GPSC6 (serotype 14) and CC193-GPSC11 (serotype 19F), but now predominantly expressing non-PCV13 serotypes (11A, 15B/C, and 24F for GPSC6; and 15A and 21 for GPSC11) was noted. These findings indicate that the pneumococcal population is adapting to the pressures conferred by PCV13 and antimicrobial use and indicate the need to maintain close surveillance.

Twenty-four Month Outcomes of Extended- Versus Standard-course Antibiotic Therapy in Children Hospitalized With Pneumonia in High-risk Settings: A Randomized Controlled Trial

BACKGROUND

Pediatric community-acquired pneumonia (CAP) can lead to long-term respiratory sequelae, including bronchiectasis. We determined if an extended (13-14 days) versus standard (5-6 days) antibiotic course improves long-term outcomes in children hospitalized with CAP from populations at high risk of chronic respiratory disease.

METHODS

We undertook a multicenter, double-blind, superiority, randomized controlled trial involving 7 Australian, New Zealand, and Malaysian hospitals. Children aged 3 months to ≤5 years hospitalized with radiographic-confirmed CAP who received 1-3 days of intravenous antibiotics, then 3 days of oral amoxicillin-clavulanate, were randomized to either extended-course (8-day oral amoxicillin-clavulanate) or standard-course (8-day oral placebo) arms. Children were reviewed at 12 and 24 months. The primary outcome was children with the composite endpoint of chronic respiratory symptoms/signs (chronic cough at 12 and 24 months; ≥1 subsequent hospitalized acute lower respiratory infection by 24 months; or persistent and/or new chest radiographic signs at 12-months) at 24-months postdischarge, analyzed by intention-to-treat, where children with incomplete follow-up were assumed to have chronic respiratory symptoms/signs ("worst-case" scenario).

RESULTS

A total of 324 children were randomized [extended-course (n = 163), standard-course (n = 161)]. For our primary outcome, chronic respiratory symptoms/signs occurred in 97/163 (60%) and 94/161 (58%) children in the extended-courses and standard-courses, respectively [relative risk (RR) = 1.02, 95% confidence interval (CI): 0.85-1.22]. Among children where all sub-composite outcomes were known, chronic respiratory symptoms/signs between groups, RR = 1.10, 95% CI: 0.69-1.76 [extended-course = 27/93 (29%) and standard-course = 24/91 (26%)]. Additional sensitivity analyses also revealed no between-group differences.

CONCLUSION

Among children from high-risk populations hospitalized with CAP, 13-14 days of antibiotics (versus 5-6 days), did not improve long-term respiratory outcomes.

Quantity and Quality of Naturally Acquired Antibody Immunity to the Pneumococcal Proteome Throughout Life

BACKGROUND

Young children and older adults are susceptible for invasive pneumococcal disease (IPD) caused by Streptococcus pneumoniae. Pneumococcal protein-specific antibodies play a protective role against IPD; however, not much is known about the pace of acquisition, maturation, and maintenance of these antibodies throughout life.

METHODS

Immunoglobulin G (IgG) and IgA levels, avidity, and/or specificity to the pneumococcal proteome in serum and saliva from healthy young children, adults, and older adults, with known carriage status, were measured by enzyme-linked immunosorbent assay (ELISA) and 2-dimensional western blotting against ΔcpsTIGR4.

RESULTS

Eleven-month-old children, the youngest age group tested, had the lowest pneumococcal proteome-specific IgG and IgA levels and avidity in serum and saliva, followed by 24-month-old children and were further elevated in adult groups. Among adult groups, the parents had the highest serum and saliva IgG and IgA antibody levels. In children, antibody levels and avidity correlated with daycare attendance and presence of siblings, posing as proxy for exposure and immunization. Immunodominance patterns slightly varied throughout life.

CONCLUSIONS

Humoral immunity against the pneumococcal proteome is acquired through multiple episodes of pneumococcal exposure. Low-level and low-avidity antiproteome antibody profiles in young children may contribute to their IPD susceptibility, while in overall antiproteome antibody-proficient older adults other factors likely play a role.

Pneumococcal Carriage in Burkina Faso After 13-Valent Pneumococcal Conjugate Vaccine Introduction and Before a Schedule Change

Background

In October 2013, Burkina Faso introduced 13-valent pneumococcal conjugate vaccine (PCV13) into the routine childhood immunization program using 3 primary doses with no booster. Previous pneumococcal carriage studies showed reductions in vaccine-type (VT) carriage in children aged <5 years but not in older age groups.

Methods

We conducted a cross-sectional, age-stratified pneumococcal carriage study among healthy persons aged ≥1 month in Bobo-Dioulasso in March 2020. Pneumococci isolated by culture from nasopharyngeal swabs (all participants) and oropharyngeal swabs (participants aged ≥5 years) were serotyped by polymerase chain reaction; a subset was serotyped by Quellung. Using data from a study with the same design from March 2017, we examined changes in pneumococcal carriage by age group.

Results

Among 1005 (2017) and 1002 (2020) enrolled participants, VT carriage decreased (21.6% to 15.9%; adjusted prevalence ratio [aPR], 0.76 [95% confidence interval {CI}, .63-.92]). By age group, decline in VT carriage was significant among children aged 5-14 years (28.9% to 16.3%; aPR, 0.57 [95% CI, .39-.84]) but not among children aged <5 years (22.4% to 19.1%; aPR, 0.87 [95% CI, .70-1.09]) or adults aged ≥15 years (12.0% to 5.5%; aPR, 0.52 [95% CI, .26-1.05]).

Conclusions

Between 3 and 6 years after PCV13 introduction, significant declines in VT carriage were observed in older children, possibly reflecting indirect effects of PCV13 use. VT carriage in children aged <5 years remained stable with almost 1 in 5 carrying VT pneumococci, suggesting limitations to a PCV schedule without a booster dose.

Limited protection of pneumococcal vaccines against emergent Streptococcus pneumoniae serotype 14/ST876 strains

PURPOSE

Streptococcus pneumoniae (Spn) is a major cause of child death. We investigated the epidemiology of S. pneumoniae in a pediatric fever clinic and explored the genomics basis of the limited vaccine response of serotype 14 strains worldwide.

METHODS

Febrile disease and pneumonia were diagnosed following criteria from the WHO at the end of 2019 at a tertiary children's hospital. Spn was isolated by culture from nasopharyngeal (NP) swabs. The density was determined by lytA-base qPCR. Isolates were serotyped by Quellung and underwent antimicrobial susceptibility testing. Whole-genome sequencing was employed for molecular serotyping, MLST, antibiotic gene determination, SNP calling, recombination prediction, and phylogenetic analysis.

RESULTS

The presence of pneumococcus in the nasopharynx (87.5%, 7/8, p = 0.0227) and a high carriage (100%, 7/7, p = 0.0123) were significantly associated with pneumonia development. Living with siblings (73.7%, 14/19, p = 0.0125) and non-vaccination (56.0%, 28/50, p = 0.0377) contributed significantly to the Spn carriage. Serotype 14 was the most prevalent strain (16.67%, 5/30). The genome analysis of 1497 serotype 14 strains indicated S14/ST876 strains were only prevalent in China, presented limited vaccine responses with higher recombination activities within its cps locus, and unique variation patterns in the genes wzg and lrp.

CONCLUSION

With the lifting of the one-child policy, it will be crucial for families with multiple children to get PCV vaccinations in China. Due to the highly variant cps locus and distinctive variation patterns in capsule shedding and binding proteins genes, the prevalent S14/ST876 strains have shown poor response to current vaccines. It is necessary to continue monitoring the molecular epidemiology of this vaccine escape clone.

Serotype epidemiology and antibiotic resistance of pneumococcal isolates colonizing infants in Botswana (2016-2019)

BACKGROUND

In 2012, Botswana introduced 13-valent pneumococcal conjugate vaccine (PCV-13) to its childhood immunization program in a 3+0 schedule, achieving coverage rates of above 90% by 2014. In other settings, PCV introduction has been followed by an increase in carriage or disease caused by non-vaccine serotypes, including some serotypes with a high prevalence of antibiotic resistance.

METHODS

We characterized the serotype epidemiology and antibiotic resistance of pneumococcal isolates cultured from nasopharyngeal samples collected from infants (≤12 months) in southeastern Botswana between 2016 and 2019. Capsular serotyping was performed using the Quellung reaction. E-tests were used to determine minimum inhibitory concentrations for common antibiotics.

RESULTS

We cultured 264 pneumococcal isolates from samples collected from 150 infants. At the time of sample collection, 81% of infants had received at least one dose of PCV-13 and 53% had completed the three-dose series. PCV-13 serotypes accounted for 27% of isolates, with the most prevalent vaccine serotypes being 19F (n = 20, 8%), 19A (n = 16, 6%), and 6A (n = 10, 4%). The most frequently identified non-vaccine serotypes were 23B (n = 29, 11%), 21 (n = 12, 5%), and 16F (n = 11, 4%). Only three (1%) pneumococcal isolates were resistant to amoxicillin; however, we observed an increasing prevalence of penicillin resistance using the meningitis breakpoint (2016: 41%, 2019: 71%; Cochran-Armitage test for trend, p = 0.0003) and non-susceptibility to trimethoprim-sulfamethoxazole (2016: 55%, 2019: 79%; p = 0.04). Three (1%) isolates were multi-drug resistant.

CONCLUSIONS

PCV-13 serotypes accounted for a substantial proportion of isolates colonizing infants in Botswana during a four-year period starting four years after vaccine introduction. A low prevalence of amoxicillin resistance supports its continued use as the first-line agent for non-meningeal pneumococcal infections. The observed increase in penicillin resistance at the meningitis breakpoint and the low prevalence of resistance to ceftriaxone supports use of third-generation cephalosporins for empirical treatment of suspected bacterial meningitis.

Nasopharyngeal carriage rate, serotype distribution, and antimicrobial profiles of Streptococcus pneumoniae among patients with acute respiratory tract infection in Manado, North Sulawesi, Indonesia

We studied the carriage rate, distribution of serotype, and antimicrobial profile of Streptococcus pneumoniae (S. pneumoniae) among patients with acute respiratory tract infections (ARTI) in two primary health centres and a tertiary referral hospital from 2019 to 2020 in Manado, North Sulawesi, Indonesia before 13-valent pneumococcal conjugate vaccine (PCV13) introduction. A total of 106 nasopharyngeal swab samples were collected from children and adult patients. Serotyping of S. pneumoniae strain was performed by sequential multiplex PCR and Quellung reaction. Antimicrobial profile was performed by the disc diffusion method. We identified thirty-one patients carried S. pneumoniae strains (29 %). The S. pneumoniae carriage rate was found to be higher among children aged 2-5 years (13/32; 40.6 %) than in children under 1 year (8/27; 29.6 %), children and adolescents under 18 years of age (5/20; 25.0 %) and adult patients (5/27; 18.5 %). The distribution of serotypes varied, including 14, 18C, 19A, 23F, 19F and 35B (two strains each) and 1, 3, 6B, 6C, 31, 9V, 15C, 16F, 17F, 23A, 35F (one strain each) and non-typeable (9/31; 29 %). We found S. pneumoniae isolates were susceptible to vancomycin (30/31; 97 %), chloramphenicol (29/31; 94 %), clindamycin (29/31; 94 %), erythromycin (22/31; 71 %), azithromycin (22/31; 71 %), tetracycline (14/31; 45 %), penicillin (11/31; 35 %), and sulfamethoxazole/trimethoprim (10/31; 32 %). This study provides supporting baseline data on distribution of serotype and antimicrobial profile of S. pneumoniae among patients with ARTI before PCV13 introduction in Manado, North Sulawesi, Indonesia.

Changes in pneumococcal serotypes distribution and penicillin resistance in healthy children five years after generalization of PCV10

Objective

Streptococcus pneumoniae (S. pneumoniae) nasopharyngeal carriage has significantly decreased after the generalization of pneumococcal vaccination worldwide. This study sought to investigate changes in S. pneumoniae carriage rates, serotype distribution and penicillin non-susceptibility following the generalization of 10-valent pneumococcal conjugate vaccine.

Methods

A prospective study was conducted in Marrakesh, Morocco, between 2017 and 2018, among healthy children attending vaccination centers. We collected nasopharyngeal swabs and questionnaire data for each child. Using univariate logistic regression, we analyzed the association between S. pneumoniae carriage and various risk factors. Comparisons of serotype diversity and penicillin resistance between 2017 and 2018 and the period before introduction of vaccination (2008-2009, n = 660) were performed using Simpson index and the chi-squared test, respectively.

Results

During 2017-2018, 515 children aged between 6 and 36 months participated. The S. pneumoniae carriage rate was 43.3%. Looking at the distribution serotypes, the rate of PCV10 serotypes rate was only 9.6%. Among non-vaccine serotypes, an increase in serotypes 6C/6D (22; 14%), 19B/19C (17; 10.8%), and 15B/15C (11; 7%) was observed. A particular increase in serotype diversity was also observed after the generalization of PCV10 (p < 0.001). S. pneumoniae non-susceptible to penicillin decreased, reaching a rate of 26.6% in 2017-2018.

Conclusion

The significant change in S. pneumoniae carriage, serotype distribution, and penicillin resistance highlights the effectiveness of the pneumococcal conjugate vaccine among children in Marrakesh, Morocco.

Pneumococcal Vaccine Breakthrough and Failure in Infants and Children: A Narrative Review

Globally, Streptococcus pneumoniae is a leading cause of vaccine-preventable morbidity and mortality in infants and children. In recent decades, large-scale pediatric immunization programs have substantially reduced the incidence of invasive pneumococcal disease. Despite this, residual vaccine-type pneumococcal disease remains in the form of vaccine breakthrough and vaccine failure. This targeted literature review aims to discuss aspects of vaccine breakthrough and failure in infants and children, including disease epidemiology, clinical presentation, risk factors, vaccination schedules, vaccine serotypes, correlates of protection, comorbidities, disease surveillance, and potential implications for future vaccine development.

Evaluating immune responses to pneumococcal vaccines

Streptococcus pneumoniae (pneumococcus) is a significant cause of bacterial infections ranging from mild infections affecting the respiratory tract such as otitis media and sinusitis to severe diseases including bacteremia, pneumonia, and invasive pneumococcal disease (IPD) (eg, meningitis, septic arthritis, and endocarditis). Pneumococcal vaccines were first developed in the 1970s as capsular pneumococcal polysaccharide vaccines, which were T-cell independent and hence lacked immunologic memory. Subsequently in the year 2000, pneumococcal conjugate vaccines (PCV) conjugated to a protein to increase immunogenicity were developed and made commercially available. The increasing number of pneumococcal serotypes identified and the expanding pipeline of PCV vaccines with improved immunogenicity have significantly reduced the morbidity and mortality associated with IPD in high-risk patients. Pneumococcal vaccines also play an important role in the diagnosis and immunophenotyping of children and adults with inborn errors of immunity (IEI) given the increasing diversity/heterogeneity of IEI presenting with primary and/or specific antibody deficiency. Other than the quantitation of serotype levels in routine clinical care, other measurements of immune response including the functional activity of antibodies, antibody avidity, cell-mediated immunity, and immunological memory remain limited to clinical trials during vaccine development.

The Effectiveness of Common Interventions in the Management of Sickle Cell Disease in Primary Care Settings: A Review

Sickle cell disease (SCD), a chronic condition that affects men and women equally, continues to present a public health burden in the United States due to its associated morbidity and complications. Despite advances in medical knowledge and the design of novel therapies for managing the disease, its burden remains compounded because of increasing rates of immigration arising from global displacements and economic unrest in many countries. We thus conducted a comprehensive literature review of publications from 2000 to 2022 to gather guidelines on managing SCD, with a search through four databases, PubMed, Embase, Google Scholar, and Cochrane; 42 articles met the final inclusion criteria after the full-text article screening process. In the United States healthcare system, primary care physicians (PCPs) are generally providers who cater to the lifelong management of chronic medical conditions, SCD not being an exception. While more SCD patients now present to primary care clinics, many PCPs still lack the confidence and adequate experience necessary to manage the condition effectively. The gap created by the shortage of PCPs extensively equipped to provide comprehensive SCD care leads to poor health outcomes for patients. It is imperative now more than ever to continue to raise awareness about this condition at the provider level, to ensure that patients receive well-rounded care to improve their quality of life and clinical outcomes. Providing up-to-date knowledge about existing and novel therapies and/or modalities of SCD treatment would undoubtedly equip the PCPs with self-assurance to manage the condition adeptly. Thus, we explore various public health interventions such as hydroxyurea therapy, pneumococcal vaccination, penicillin therapy, iron chelation therapy, and clinical decision support tools that have been implemented in primary healthcare settings and shown to be effective in improving SCD care. We also discuss recent advancements that can lead to improved outcomes for SCD patients in the future.