Pneumococcal carriage among children in low and lower-middle-income countries: A systematic review

Upper respiratory Streptococcus pneumoniae colonization among working-age adults with prevalent exposure to overcrowding

Most pneumococcal disease occurs among infants and older adults and is thought to be driven by the transmission of Streptococcus pneumoniae from young children to these vulnerable age groups. However, pneumococcal disease outbreaks also affect non-elderly adults living or working in congregate, close-contact settings. Little is known about pneumococcal carriage in such populations. From July to November 2020, we collected saliva from low-income adult farmworkers in Monterey County, California, and tested for pneumococcal carriage following culture enrichment via quantitative PCR assays targeting the pneumococcal lytA and piaB genes. Participants were considered to carry pneumococci if lytA and piaB cycle threshold values were both below 40. Among 1,283 participants enrolled in our study, 117 (9.1%) carried pneumococci. Carriers tended more often than non-carriers to be exposed to children aged <5 years [odds ratio (OR) = 1.45 (0.95-2.20)] and overcrowding [OR = 1.48 (0.96-2.30) and 2.84 (1.20-6.73), respectively, for participants in households with >2-4 and >4 persons per bedroom vs ≤2 persons per bedroom]. Household overcrowding remained associated with increased risk of carriage among participants not exposed to children aged <5 years [OR = 2.05 (1.18-3.59) for participants living in households with >2 vs ≤2 persons per bedroom]. Exposure to children aged <5 years and overcrowding were each associated with increased pneumococcal density among carriers [piaB cT difference of 2.04 (0.36-3.73) and 2.44 (0.80-4.11), respectively]. While exposure to young children was a predictor of pneumococcal carriage, associations of overcrowding with increased prevalence and density of carriage in households without young children suggest that transmission also occurs among adults in close-contact settings.IMPORTANCEAlthough infants and older adults are the groups most commonly affected by pneumococcal disease, outbreaks are known to occur among healthy, working-age populations exposed to overcrowding, including miners, shipyard workers, military recruits, and prisoners. Carriage of Streptococcus pneumoniae is the precursor to pneumococcal disease, and its relation to overcrowding in adult populations is poorly understood. We used molecular methods to characterize pneumococcal carriage in culture-enriched saliva samples from low-income adult farmworkers in Monterey County, CA. While exposure to children in the household was an important risk factor for pneumococcal carriage, living in an overcrowded household without young children was an independent predictor of carriage as well. Moreover, participants exposed to children or overcrowding carried pneumococci at higher density than those without such exposures, suggesting recent transmission. Our findings suggest that, in addition to transmission from young children, pneumococcal transmission may occur independently among adults in overcrowded settings.

Interactions between respiratory syncytial virus and Streptococcus pneumoniae in the pathogenesis of childhood respiratory infections: a systematic review

Lower respiratory tract infections, commonly caused by respiratory syncytial virus (RSV) or Streptococcus pneumoniae (pneumococcus), pose a substantial global health burden, especially in children younger than 5 years of age. A deeper understanding of the relationship between RSV and pneumococcus would aid the development of health-care approaches to disease prevention and management. We completed a systematic review to identify and assess evidence pertaining to the relationship between RSV and pneumococcus in the pathogenesis of childhood respiratory infections. We found mechanistic evidence for direct pathogen-pathogen interactions and for indirect interactions involving host modulation. We found a strong seasonal epidemiological association between these two pathogens, which was recently confirmed by a parallel decrease and a subsequent resurgence of both RSV and pneumococcus-associated disease during the COVID-19 pandemic. Importantly, we found that pneumococcal vaccination was associated with reduced RSV hospitalisations in infants, further supporting the relevance of their interaction in modulating severe disease. Overall evidence supports a broad biological and clinical interaction between pneumococcus and RSV in the pathogenesis of childhood respiratory infections. We hypothesise that the implementation of next-generation pneumococcal and RSV vaccines and monoclonal antibodies targeting RSV will act synergistically to reduce global morbidity and mortality related to childhood respiratory infections.

Vaccines for the Elderly and Vaccination Programs in Europe and the United States

The share of the elderly population is growing worldwide as life expectancy increases. Immunosenescence and comorbidities increase infectious diseases' morbidity and mortality in older adults. Here, we aimed to summarize the latest findings on vaccines for the elderly against herpes zoster, influenza, respiratory syncytial virus (RSV), COVID-19, and pneumococcal disease and to examine vaccine recommendation differences for this age group in Europe and the United States. PubMed was searched using the keywords "elders" and "vaccine" alongside the disease/pathogen in question and paraphrased or synonymous terms. Vaccine recommendations were also sought in the European and US Centers for Disease Control and Prevention databases. Improved vaccines, tailored for the elderly, mainly by using novel adjuvants or by increasing antigen concentration, are now available. Significant differences exist between immunization policies, especially between European countries, in terms of the recipient's age, number of doses, vaccination schedule, and implementation (mandatory or recommended). Understanding the factors that influence the immune response to vaccination in the elderly may help to design vaccines that offer long-term protection for this vulnerable age group. A consensus-based strategy in Europe could help to fill the gaps in immunization policy in the elderly, particularly regarding vaccination against RSV and pneumococcus.

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.

RNA cis-regulators are important for Streptococcus pneumoniae in vivo success

Bacteria have evolved complex transcriptional regulatory networks, as well as many diverse regulatory strategies at the RNA level, to enable more efficient use of metabolic resources and a rapid response to changing conditions. However, most RNA-based regulatory mechanisms are not well conserved across different bacterial species despite controlling genes important for virulence or essential biosynthetic processes. Here, we characterize the activity of, and assess the fitness benefit conferred by, twelve cis-acting regulatory RNAs (including several riboswitches and a T-box), in the opportunistic pathogen Streptococcus pneumoniae TIGR4. By evaluating native locus mutants of each regulator that result in constitutively active or repressed expression, we establish that growth defects in planktonic culture are associated with constitutive repression of gene expression, while constitutive activation of gene expression is rarely deleterious. In contrast, in mouse nasal carriage and pneumonia models, strains with either constitutively active and repressed gene expression are significantly less fit than matched control strains. Furthermore, two RNA-regulated pathways, FMN synthesis/transport and pyrimidine synthesis/transport display exceptional sensitivity to mis-regulation or constitutive gene repression in both planktonic culture and in vivo environments. Thus, despite lack of obvious phenotypes associated with constitutive gene expression in vitro, the fitness benefit conferred on bacteria via fine-tuned metabolic regulation through cis-acting regulatory RNAs is substantial in vivo, and therefore easily sufficient to drive the evolution and maintenance of diverse RNA regulatory mechanisms.

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.

Nasopharyngeal carriage of Streptococcus pneumoniae among children <5 years of age in Indonesia prior to pneumococcal conjugate vaccine introduction

Pneumococcal conjugate vaccines (PCVs) prevent nasopharyngeal colonization with vaccine serotypes of Streptococcus pneumoniae, leading to reduced transmission of pneumococci and stronger population-level impact of PCVs. In 2017 we conducted a cross-sectional pneumococcal carriage study in Indonesia among children aged <5 years before 13-valent PCV (PCV13) introduction. Nasopharyngeal swabs were collected during visits to community integrated health service posts at one peri-urban and one rural study site. Specimens were analyzed by culture, and isolates were serotyped using sequential multiplex polymerase chain and Quellung reaction. Antibiotic susceptibility was performed by broth microdilution method. We enrolled 1,007 children in Gunungkidul District, Yogyakarta (peri-urban) and 815 in Southwest Sumba, East Nusa Tenggara (rural). Pneumococcal carriage prevalence was 30.9% in Gunungkidul and 87.6% in Southwest Sumba (combined: 56.3%). PCV13 serotypes (VT) carriage was 15.0% in Gunungkidul and 52.6% in Southwest Sumba (combined: 31.8%). Among pneumococcal isolates identified, the most common VT were 6B (16.4%), 19F (15.8%), and 3 (4.6%) in Gunungkidul (N = 323) and 6B (17.6%), 19F (11.0%), and 23F (9.3%) in Southwest Sumba (N = 784). Factors associated with pneumococcal carriage were age (1-2 years adjusted odds ratio (aOR) 1.9, 95% CI 1.4-2.5; 3-4 years aOR 1.5, 95% CI 1.1-2.1; reference <1 year), other children <5 years old in the household (aOR 1.5, 95% CI 1.1-2.0), and presence of ≥1 respiratory illness symptom (aOR 1.8, 95% CI 1.4-2.2). Overall, 61.5% of the pneumococcal isolates were non-susceptible to ≥1 antibiotic class and 13.2% were multi-drug non-susceptible (MDNS) (non-susceptible to ≥3 classes of antibiotics). Among 602 VT isolates, 73.9% were non-susceptible and 19.9% were MDNS. These findings are critical to establish a pre-PCV13 carriage prevalence and demonstrate the complexity in evaluating the impact of PCV13 introduction in Indonesia given the wide variability in the carriage prevalence as shown by the two study sites.

Pneumococcal carriage, serotype distribution, and antimicrobial susceptibility in Papua New Guinean children vaccinated with PCV10 or PCV13 in a head-to-head trial

BACKGROUND

Children in Papua New Guinea (PNG) are at high risk of pneumococcal infections. We investigated pneumococcal carriage rates, serotype distribution, and antimicrobial susceptibility in PNG children after vaccination with 10-valent or 13-valent pneumococcal conjugate vaccines (PCV10; PCV13).

METHODS

Infants (N = 262) were randomized to receive 3 doses of PCV10 or PCV13 at 1-2-3 months of age, followed by pneumococcal polysaccharide vaccination (PPV) or no PPV at 9 months of age. Nasopharyngeal swabs (NPS) collected at ages 1, 4, 9, 10, 23 and 24 months were cultured using standard bacteriological procedures. Morphologically distinct Streptococcus pneumoniae colonies were serotyped by the Quellung reaction. Antimicrobial susceptibility was determined by Kirby-Bauer disc diffusion and minimum inhibitory concentration (MIC).

RESULTS

S. pneumoniae was isolated from 883/1063 NPS collected at 1-23 months of age, including 820 serotypeable (64 different serotypes) and 144 non-serotypeable isolates. At age 23 months, 93.6% (95%CI 86.6-97.6%) of PCV10 recipients and 88.6% (95%CI 80.1-94.4%) of PCV13 recipients were pneumococcal carriers, with higher carriage of PCV10 serotypes by PCV10 recipients (19.8%, 95%CI 12.2-29.5) than PCV13 recipients (9.3%, 95%CI 4.1-17.3) (p = 0.049). There were no other statistically significant differences between PCV10 and PCV13 recipients and children receiving PPV or no PPV. Nearly half (45.6%) of carried pneumococci were non-susceptible to penicillin based on the meningitis breakpoint (MIC ≥ 0.12 µg/mL), but resistance was rare (1.1%) using the non-meningitis cut-off (MIC ≥ 8 µg/mL). Non-susceptibility to trimethoprim-sulfamethoxazole (SXT) was common: 23.2% of isolates showed intermediate resistance (MIC 1/19-2/38 µg/mL) and 16.9% full resistance (MIC ≥ 4/76 µg/mL). PCV serotypes 14 and 19A were commonly non-susceptible to both penicillin (14, 97%; 19A, 70%) and SXT (14, 97%; 19A, 87%).

CONCLUSION

Even after PCV10 or PCV13 vaccination, children living in a high-risk setting such as PNG continue to experience high levels of pneumococcal colonization, including carriage of highly antimicrobial-resistant PCV serotypes. The study is registered with ClinicalTrials.gov (CTN NCT01619462).

A randomized, open-label, phase 3 study evaluating safety and immunogenicity of 13-valent pneumococcal conjugate vaccine in Chinese infants and children under 6 years of age

Streptococcus pneumoniae causes a considerable disease burden among children in China. Many isolates exhibit antimicrobial resistance but are often serotypes covered by the 13-valent pneumococcal conjugate vaccine (PCV13). Because the approved infant immunization schedule in China allows PCV13 vaccination only for those 6 weeks to 15 months of age, this phase 3 study was conducted to evaluate PCV13 immunogenicity and safety in unvaccinated older infants and children. Eligible participants were stratified by age into four cohorts: Cohort 1 (n = 125), 6 weeks-2 months; Cohort 2 (n = 354), 7-<12 months; Cohort 3 (n = 250), 1 -<2 years; Cohort 4 (n = 207), 2-<6 years. Cohort 1 received PCV13 at ages 2, 4, and 6 months; older cohorts were randomized 2:1 to PCV13 or Haemophilus influenzae type b (Hib) vaccine using age-appropriate schedules. Within-group immune responses were assessed by immunoglobulin G (IgG) concentrations and opsonophagocytic activity (OPA) titers. Safety evaluations included solicited reactogenicity events and adverse events (AEs). IgG geometric mean concentrations and OPA geometric mean titers for all 13 PCV13 serotypes increased for all participants vaccinated with PCV13, but not those vaccinated with Hib. Immune responses in Cohorts 2-4 were generally comparable with those in Cohort 1 (the infant series) for most serotypes. PCV13 was well tolerated across cohorts, with reported AEs consistent with expectations in these age groups; no new safety signals were identified. These results suggest that PCV13 administered as a catch-up regimen to infants and children 7 months-<6 years of age in China will effectively reduce vaccine-type pneumococcal disease in this population. NCT03574389.

Pneumococcal carriage among high-risk adults in a country with nonmandatory pneumococcal vaccination during the coronavirus disease 2019 pandemic

BACKGROUND

Streptococcus pneumoniae carriage is a prerequisite for clinical infections and is used to make public health decisions on vaccine licensure. Pneumococcal carriage data among high-risk Thai adults are needed before national vaccine program introduction. The association between coronavirus disease 2019 (COVID-19) and pneumococcal carriage were also investigated.

METHODS

During the COVID-19 pandemic, a multi-center cross-sectional study was conducted among high-risk Thai adults from September 2021 to November 2022. Pneumococcal carriage and serotypes were investigated using both conventional and molecular methods. Demographics and co-morbidities were determined for carriage while accounting for case clustering from various study sites.

RESULTS

A total of 370 individuals were enrolled. The prevalence of pneumococcal carriage, as determined by the molecular method, was 30.8 % (95 % confidence interval (CI): 26.1-35.8), while after excluding non-typeable pneumococci from the oropharyngeal sample, the carriage prevalence was 20.8 % (95 % CI: 16.79-25.31). The serotype coverage rates by pneumococcal vaccine were 12.3 %, 13.1 %, and 16.4 % for PCV13, PCV15 or PCV20, and PPSV23, respectively, while the non-vaccine type was the majority (45.1 %). The most common serotype was 19B/C (35.5 %), followed by 6 A/B/C/D (10.7 %). The age group under 65 years was associated with a higher pneumococcal carriage rate than the age group 85 and older (odds ratio (OR): 5.01, 95 % CI: 1.75-14.36). There was no significant difference between SARS-CoV-2 and carriage status.

CONCLUSIONS

The prevalence of pneumococcal carriage in Thais was high. The majority of serotypes were not covered by the vaccine. Further studies on the link between carriage serotypes and disease are required. The magnitude and serotype distribution of carriage were comparable in the SARS-CoV-2 positive and negative groups.