Carriage of Streptoccoccus pneumoniae in healthy adults aged 60 years or over in a population with very high and long-lasting pneumococcal conjugate vaccine coverage in children: rationale and perspectives for PCV13 implementation

Saliva as an alternative sample type for detection of pneumococcal carriage in young children

For children, the gold standard for the detection of pneumococcal carriage is conventional culture of a nasopharyngeal swab. Saliva, however, has a history as one of the most sensitive methods for surveillance of pneumococcal colonization and has recently been shown to improve carriage detection in older age groups. Here, we compared the sensitivity of paired nasopharyngeal and saliva samples from PCV7-vaccinated 24-month-old children for pneumococcal carriage detection using conventional and molecular detection methods. Nasopharyngeal and saliva samples were collected from 288 24-month-old children during the autumn/winter, 2012/2013. All samples were first processed by conventional diagnostic culture. Next, DNA extracted from all plate growth was tested by qPCR for the presence of the pneumococcal genes piaB and lytA and a subset of serotypes. By culture, 161/288 (60 %) nasopharyngeal swabs tested positive for pneumococcus, but detection was not possible from saliva due to abundant polymicrobial growth on culture plates. By qPCR, 155/288 (54 %) culture-enriched saliva samples and 187/288 (65 %) nasopharyngeal swabs tested positive. Altogether, 219/288 (76 %) infants tested positive for pneumococcus, with qPCR-based carriage detection of culture-enriched nasopharyngeal swabs detecting significantly more carriers compared to either conventional culture (P<0.001) or qPCR detection of saliva (P=0.002). However, 32/219 (15 %) carriers were only positive in saliva, contributing significantly to the overall number of carriers detected (P=0.002). While testing nasopharyngeal swabs by qPCR proved most sensitive for pneumococcal detection in infants, saliva sampling could be considered as complementary to provide additional information on carriage and serotypes that may not be detected in the nasopharynx and may be particularly useful in longitudinal studies, requiring repeated sampling of study participants.

Decreased Pneumococcal Carriage Among Older Adults in Denmark During the COVID-19 Lockdown

Background

COVID-19 containment measures reduced the burden of invasive pneumococcal disease. Data on pneumococcal carriage rates among adults during the pandemic are scarce.

Methods

Naso- and oropharyngeal swabs and questionnaires were collected during January 2019 to December 2021 from adults ≥64 years of age. Carriage was determined by lytA/piaB PCR.

Results

A total of 1556 participants provided paired naso- and oropharyngeal swabs. Their median age was 74 years (IQR, 70-79). Streptococcus pneumoniae DNA was detected in 146 (9.4%) oropharyngeal swabs and 34 (2.2%) nasopharyngeal. The carriage rate decreased from 12.9% (95% CI, 10.1%-16.1%, n = 66/511) prelockdown (January 2019-February 2020) to 4.2% (95% CI, 2.0%-7.5%, n = 10/240) during lockdown (March 2020-February 2021) and increased to 12.1% (95% CI, 9.8%-14.7%, n = 87/719) with the reopening of society (March 2021-December 2021; P = .0009).

Conclusions

Pneumococcal carriage prevalence declined significantly during pandemic mitigation measures and rebounded to prepandemic levels as measures were lifted.

Epidemiology and molecular characteristics of respiratory syncytial virus (RSV) among italian community-dwelling adults, 2021/22 season

BACKGROUND

Respiratory syncytial virus (RSV) is a leading cause of acute respiratory infections worldwide. While historically RSV research has been focused on children, data on RSV infection in adults are limited. The goal of this study was to establish the prevalence of RSV in community-dwelling Italian adults and analyze its genetic variability during the 2021/22 winter season.

METHODS

In this cross-sectional study, a random sample of naso-/oropharyngeal specimens from symptomatic adults seeking for SARS-CoV-2 molecular testing between December 2021 and March 2022 were tested for RSV and other respiratory pathogens by means of reverse-transcription polymerase chain reaction. RSV-positive samples were further molecularly characterized by sequence analysis.

RESULTS

Of 1,213 samples tested, 1.6% (95% CI: 0.9-2.4%) were positive for RSV and subgroups A (44.4%) and B (55.6%) were identified in similar proportions. The epidemic peak occurred in December 2021, when the RSV prevalence was as high as 4.6% (95% CI: 2.2-8.3%). The prevalence of RSV detection was similar (p = 0.64) to that of influenza virus (1.9%). All RSV A and B strains belonged to the ON1 and BA genotypes, respectively. Most (72.2%) RSV-positive samples were also positive for other pathogens being SARS-CoV-2, Streptococcus pneumoniae and rhinovirus the most frequent. RSV load was significantly higher among mono-detections than co-detections.

CONCLUSION

During the 2021/22 winter season, characterized by the predominant circulation of SARS-CoV-2 and some non-pharmaceutical containment measures still in place, a substantial proportion of Italian adults tested positive for genetically diversified strains of both RSV subtypes. In view of the upcoming registration of vaccines, establishment of the National RSV surveillance system is urgently needed.

Nasopharyngeal Carriage Rate of Streptococcus pneumoniae, Related Risk Factors, and Antibiotic Susceptibility Among Inmates in Hawassa Central Prison Institute: Hawassa, Sidama National Region, Ethiopia

Background

The bacterium Streptococcus pneumoniae commonly causes severe bacterial illnesses in both children and adults. S. pneumoniae is the most fatal bacterial pathogen, causing 50% of the deaths from lower respiratory infections in people of all ages.

Objectives

This study was aimed to determine a nasopharyngeal carriage rate of S. pneumoniae, related risk factors, and antibiotic susceptibility among prisoners in Hawassa Central Prison Institute Hawassa, Ethiopia.

Methods

From July to August 2021, a cross-sectional investigation was carried out in Hawassa prison. All randomly chosen adult volunteers were a part of the study. In this study, about 330 different people were included. Within 3 h of collection, the swab specimen was inoculated onto 5% sheep blood agar; the inoculated medium was then incubated for 18-24 h at 35-37 °C in a CO2-enriched environment. Following incubation, the S. pneumoniae colonies were suspected, but the usual colony shape, alpha-hemolysis, Gram staining, optochin susceptibility, and bile solubility test allowed for confirmation. Antimicrobial susceptibility testing was carried out in accordance with the Clinical and Laboratory Standards Institute's guidelines.

Results

Overall carriage rate of S. pneumoniae among adult individuals were 41 (12.7%). The carriage rate of S. pneumoniae was affected by age classes that 39-48 years (OR = 4.82, 95%CI = 1.49-15.56, p = .009), 49-58 years (OR = 5.27, 95%CI = 1.27-21.89, p = .022), and greater than 58 years (OR = 4.36, 95%CI = 1.13-16.90, p = .033); cigarette smoking (OR = 3.41, 95%CI = 1.16-10.01, p = .026); and sharing beds (OR = 3.91, 95%CI = 1.27-12.07, p = .018). The majority of the isolates are susceptible for clindamycin (87.8%) and resistant for chloramphenicol (56%). Multidrug resistance was observed in 36.7%.

Conclusions

The overall carriage rate of S. pneumoniae was 12.7%. Age, cigarette smoking, and sharing beds in the same prison room had a substantial impact on this nasopharyngeal carriage rate. Chloramphenicol (56%), erythromycin (41.5%), tetracycline (39%), and co-trimoxazole (34.1%) resistance were seen in the majority of S. pneumoniae isolates. Early detection, hygiene maintenance, and appropriate treatment are necessary.

Nasopharyngeal Carriage and Serotype Distribution of Streptococcus pneumoniae in Elderly: A Cross-sectional Study in Turkey

Objective

The incidence and mortality of invasive pneumococcal disease are much higher in people over 65 years compared to the general population. The incidence of the disease and the distribution of serotypes changed with the spread of childhood conjugate pneumococcal vaccines and the use of vaccines in the adult age group. Nasopharyngeal carriage is an important stage in the disease pathogenesis. In this study, we aimed to determine the pneumococcal carriage prevalence and serotype distribution in adults aged ≥ 65 years living in a nursing home.

Materials and Methods

The nasopharyngeal swabs were taken from ≥ 65 years old people living in Narlıdere Nursing Home. The specimens were cultured and pneumococci were isolated according to colony appearance, optochin sensitivity and solubility in bile salts. Pneumococcal serotypes were identified using the capsule swelling reaction.

Results

Pneumococcus was isolated in 10 of 341 subjects and the pneumococcal carriage prevalence was 2.9%. Advanced age, immunocompromised status and chronic renal failure were associated with pneumococcal carriage. In multivariate model, having immunocompromised status was significantly associated with carriage. Serotypes/serogroups of pneumococci were 7F, 23F, 10, 11, 15. 17, 20 and 33. The 13 valent conjugated pneumococcal vaccine serotype carriage prevalence was 0.6%.

Conclusion

Although pneumococcal colonization in older people is uncommon, most of the isolated serotypes are not PCV13 serotypes. The monitoring of pneumococcal serotypes can offer useful information about the circulation of this pathogen among older people and the potential protective effect of pneumococcal vaccines.

Oral streptococci expressing pneumococci-like cross-reactive capsule types can affect WHO recommended pneumococcal carriage procedure

BACKGROUND

Carriage studies are fundamental to assess the effects of pneumococcal vaccines. Since a large proportion of oral streptococci carry homologs of pneumococcal genes, nonculture-based detection and serotyping of upper respiratory tract (URT) samples can be problematic. Herein, we investigated if culture-free molecular methods could differentiate pneumococci from oral streptococci carried by adults in URT.

METHODS

Paired nasopharyngeal (NP) and oropharyngeal (OP) samples were collected from 100 older adults twice a month for one year. Extracts from the combined NP+OP samples (n=2400) were subjected to lytA real-time PCR. Positive samples were subjected to pure culture isolation followed by species confirmation using multiple approaches. Multibead assay and whole-genome sequencing were used for serotyping.

RESULTS

lytA-PCR was positive in 301 combined NP+OP extracts, 20 of which grew probable pneumococcal-like colonies based on colony morphology and biochemical tests. Multiple approaches confirmed that four isolates were S. pneumoniae, three were S. psuedopneumoniae, and thirteen were S. mitis. Eight nonpneumococcal strains carried pneumococcus-like cps loci (size: ~18 to 25 kb) that showed >70% of nucleotide identity with their pneumococcal counterparts. While investigating the antigenic profile, we found some S. mitis strains (P066 and P107) reacted with both serotype-specific polyclonal (Type 39 and FS17b) and monoclonal (Hyp10AG1 and Hyp17FM1) antisera, whereas some strains (P063 and P074) reacted only with polyclonal antisera (Type 5 and FS35a).

CONCLUSION

The extensive capsular overlap suggests that pneumococcal vaccines could reduce carriage of oral streptococci expressing cross-reactive capsules. Further, direct use of culture-free PCR-based methods in URT samples has limited usefulness for carriage studies.

Upper airways colonisation of Streptococcus pneumoniae in adults aged 60 years and older: A systematic review of prevalence and individual participant data meta-analysis of risk factors

•

Systematic review and meta-analysis of 18 studies and more than 6000 participants.

•

Adults over the age of 60 had a pooled prevalence of pneumococcal carriage of 9%.

•

Risk factors: contact with children, smoking and residing in a nursing home.

Background

Colonisation with Streptococcus pneumoniae can lead to invasive pneumococcal disease and pneumonia. Pneumococcal acquisition and prevalence of colonisation are high in children. In older adults, a population susceptible to pneumococcal disease, colonisation prevalence is reported to be lower, but studies are heterogeneous.

Methods

This is a systematic review and meta-analysis of prevalence of, and risk factors for, pneumococcal colonisation in adults ≥ 60 years of age (PROSPERO #42016036891). We identified peer-reviewed studies reporting the prevalence of S. pneumoniae colonisation using MEDLINE and EMBASE (until April 2016), excluding studies of acute disease. Participant-level data on risk factors were sought from each study.

Findings

Of 2202 studies screened, 29 were analysable: 18 provided participant-level data (representing 6290 participants). Prevalence of detected pneumococcal colonisation was 0–39% by conventional culture methods and 3–23% by molecular methods. In a multivariate analysis, colonisation was higher in persons from nursing facilities compared with the community (odds ratio (OR) 2•30, 95% CI 1•26–4•21 and OR 7•72, 95% CI 1•15–51•85, respectively), in those who were currently smoking (OR 1•69, 95% CI 1•12–2•53) or those who had regular contact with children (OR 1•93, 95%CI 1•27–2•93). Persons living in urban areas had significantly lower carriage prevalence (OR 0•43, 95%CI 0•27–0•70).

Interpretation

Overall prevalence of pneumococcal colonisation in older adults was higher than expected but varied by risk factors. Future studies should further explore risk factors for colonisation, to highlight targets for focussed intervention such as pneumococcal vaccination of high-risk groups.

Funding

No funding was required.

Re-evaluation of Streptococcus pneumoniae carriage in Portuguese elderly by qPCR increases carriage estimates and unveils an expanded pool of serotypes

Streptococcus pneumoniae (pneumococcus) is a leading cause of infections worldwide. Disease is preceded by asymptomatic colonization of the upper respiratory tract. Classical culture-based methods (CCBM) suggest that colonization in the elderly is <5%. Recently, use of qPCR has challenged these observations. We estimated pneumococcal carriage prevalence and serotypes among Portuguese elderly using qPCR and compared results with those obtained by CCBM. Nasopharyngeal and oropharyngeal paired samples (599 each) of individuals over 60 years living in nursing (n = 299) or family (n = 300) homes were screened for the presence of pneumococci by qPCR targeting lytA and piaB. Positive samples were molecular serotyped. Use of qPCR improved detection of pneumococci in oropharyngeal samples compared to CCBM: from 0.7% to 10.4% (p < 0.001) in the nursing home collection, and from 0.3% to 5.0% (p < 0.001) in the family home collection. No significant differences were observed between both methods in nasopharyngeal samples (5.4% vs. 5.4% in the nursing homes; and 4.3% vs. 4.7% in the family homes). Twenty-one serotypes/serogroups were detected by qPCR compared to 14 by CCBM. In conclusion, use of qPCR suggests that pneumococcal carriage in Portuguese elderly is approximately 10%, and unveiled a large pool of serotypes. These results are important to understand progression to disease and impact of pneumococcal vaccines in the elderly.

Upper respiratory tract colonization with Streptococcus pneumoniae in adults

INTRODUCTION

Most of the current evidence regarding pneumococcal upper respiratory colonization in adults suggests that despite high disease burden, carriage prevalence is low. Contemporary studies on adult pneumococcal colonization have largely followed the pediatric approach by which samples are obtained mostly from the nasopharynx and bacterial detection is evaluated by routine culture alone. Recent evidence suggests that the 'pediatric approach' may be insufficient in adults and pneumococcal detection in this population may be improved by longitudinal studies that include samples from additional respiratory sites combined with more extensive laboratory testing.

AREAS COVERED

In this article, relevant literature published in peer review journals on adult pneumococcal colonization, epidemiology, detection methods, and recommendations were reviewed.

EXPERT OPINION

Respiratory carriage of Streptococcus pneumoniae has been underestimated in adults. Contemporary pneumococcal carriage studies in adults that collect samples from alternative respiratory sites such as the oropharynx, saliva, or nasal wash; are culture-enriched for pneumococcus; and use molecular diagnostic methods designed to target two pneumococcal DNA sequences should enhance pneumococcal detection in the adult respiratory tract. This finding may have implications for the interpretation of dynamics of pneumococcal transmission and vaccination.

Estimating the Clinical and Economic Impact of Switching from the 13-Valent Pneumococcal Conjugate Vaccine (PCV13) to the 10-Valent Pneumococcal Conjugate Vaccine (PCV10) in Italy

Background: Invasive and non-invasive pneumococcal diseases are significant health and economic burdens, especially in children and the elderly. Italy included the 7-valent (PCV7) and 13-valent pneumococcal conjugate vaccine (PCV13) in the National Immunization Program in 2007 and 2010, respectively, allowing a dramatic reduction in the burden of pneumococcal disease. In the era of budget constraints, decision-makers may consider switching from the higher-valent, more costly PCV13, to the lower-cost PCV10. This study estimated the potential public health and economic impact of changing vaccine programs from PCV13 to PCV10 in Italy. Methods: A decision-analytic forecasting model estimated the impact of PCV programs. Real-world surveillance data were used to forecast serotype distribution and disease incidence among children and the elderly over a specified 5-year time horizon. Costs and outcomes included estimates of cases and deaths avoided, quality-adjusted life years (QALYs) gained, and total costs from a payer perspective, discounted at an assumed rate of 3.0%, and robustness validated through several scenarios and sensitivity analyses. Results: A switch from PCV13 to PCV10 would increase invasive pneumococcal disease (IPD) cases by 59.3% (4317 cases) over a 5-year horizon, primarily due to serotypes 3 and 19A. Pneumonia increased by 8.3% and acute otitis media (AOM) by 96.1%. Maintaining a PCV13 program would prevent a total incremental 531,435 disease cases (1.02M over a 10-year time horizon) and 641 deaths due to invasive pneumococcal disease (IPD), with €23,642 per QALY gained over 5 years versus PCV10. One-way and probabilistic sensitivity analyses showed that a PCV13-based program remained cost-effective in 99.7% of the simulations in Italy as parameters varied within their plausible range; percent vaccinated had the most impact. Conclusions: Maintaining the PCV13 strategy would provide substantial public health and economic benefits in Italy and is cost-effective. Switching from PCV13 to PCV10 would increase the incidence of pneumococcal disease primarily linked to re-emergence of serotypes 3 and 19A.

Pneumococcal carriage among adults aged 50 years and older with co-morbidities attending medical practices in Rome, Italy

BACKGROUND

Data on Streptococcus pneumoniae carriage in adults with co-morbidities are limited. In this study we estimated the pneumococcal carriage among adults with co-morbidities and evaluated socio-demographic and clinical risk factors. The potential coverage of the current pneumococcal vaccines recommended for adults (PCV13 and PPV23) was also investigated.

METHODS

A cross-sectional study on S. pneumoniae carriage among unvaccinated adults ≥50 years with co-morbidities, presenting with or without acute respiratory symptoms at general practitioners in Rome, Italy, between October 2015 and July 2016 was conducted. Pneumococcal carriage was investigated by both cultural and molecular methods. Socio-demographic variables and co-morbidities were evaluated by logistic models as possible risk factors for pneumococcal carriage.

RESULTS

Out of 248 patients (median age: 73 yrs; IQR: 65-79), 12 (4.8%) and 83 (33.5%) individuals were found colonized using cultural or molecular methods, respectively. Potential risk factors for pneumococcal colonization as ascertained by molecular methods were: low level of education (adjusted OR = 3.71, 95% CI: 1.62-9.40), winter months (December-March vs other months, adjusted OR = 2.56, 95% CI: 1.29-5.14), and presence of chronic lung diseases (adjusted OR = 2.18, 95% CI: 1.15-4.16). The combination of serotype-specific multiplex RT-PCR and conventional PCR allowed to identify 22 serotypes/group of serotypes, of which the most common were: 24F/24A/24B, 12F/12A/12B/44/46, 6A/6B, 14, 15B/15C, and 22F/22A. Prevalence of pneumococcal carriage due to PCV13 serotypes and non-PCV13 serotypes was 23.6% and 67.3%, respectively. Prevalence of colonization due to PPV23 serotypes was estimated to be 54.6%.

CONCLUSIONS

A high prevalence of S. pneumoniae carriage was observed among adults with co-morbidities, especially among individuals affected by chronic lung diseases. These results support vaccine strategies based on the sequential administration of PCV13 and PPV23 to control potentially invasive pneumococcal strains in adults, especially in subjects with co-morbidities.

Changes in the Pneumococcal Vaccine Serotypes in Adult Noninvasive Pneumonia after the Introduction of Pneumococcal Conjugate Vaccination for Children

Context

Although the incidence of invasive pneumococcal infections in children has decreased since the introduction of pneumococcal conjugate vaccines (PCVs), the appearance of serotype replacements has continued to increase.

Aims

We examined the frequency of serotype replacements in adult cases of pneumococcal pneumonia. Furthermore, the transition in the coverage of vaccine serotypes (VTs) to non-VTs (NVTs) was also examined.

Settings and Design

We investigated all confirmed cases of pneumococcal pneumonia in 303 adult patients admitted to Yamagata Saisei Hospital between April 2006 and March 2015.

Materials and Methods

Pneumococcal serotypes were determined by testing for a specific type of antiserum using the capsular swelling method.

Statistical Analysis Used

Chi-square tests were used to compare patient characteristics.

Results

Annually, the number of admitted patients ranged from 24 to 43, with most of them being men (64.7% of the total patient cohort). Although many cases involved some underlying conditions, the rate of pneumococcal vaccination remained low. The average rate of multigeneration housing was high (37.6%). The rates of pneumococcal vaccine coverage declined since 2013 (7-valent PCV (PCV7), 18.5%; PCV13, 59.3%; and 23-pneumococcal polysaccharide vaccine (PPSV23), 66.7%) and were <50% for each vaccine (PCV7, 4.7%; PCV13, 32.6%; and PPSV23, 48.8%) in 2015. In addition, the VTs were replaced with NVTs in 2015 (48.8% vs. 51.2%).

Conclusions

The frequency of NVTs in adult pneumococcal pneumonia increased in 2013, with the frequency exceeding that of the vaccine forms in 2015. Regular PCV vaccination of children and multigeneration housing seem to be associated with this reversed trend.

Pneumococcal Capsular Polysaccharide Immunity in the Elderly

Immunity to pneumococcal infections is impaired in older people, and current vaccines are poorly protective against pneumococcal disease in this population. Naturally acquired immunity to pneumococcal capsular polysaccharides develops during childhood and is robust in young adults but deteriorates with advanced age. In particular, antibody levels and function are reduced in older people. Pneumococcal vaccines are recommended for people >65 years old. However, the benefits of polysaccharide and protein-conjugated vaccines in this population are small, because of both serotype replacement and incomplete protection against vaccine serotype pneumococcal disease. In this review, we overview the immune mechanisms by which naturally acquired and vaccine-induced pneumococcal capsular polysaccharide immunity declines with age, including altered colonization dynamics, reduced opsonic activity of antibodies (particularly IgM), and impaired mucosal immunity.

Pneumococcal Colonization in the Familial Context and Implications for Anti-Pneumococcal Immunization in Adults: Results from the BINOCOLO Project in Sicily

The spread of Streptococcus pneumoniae within families has been scarcely investigated so far. This feasibility study aimed to estimate the prevalence of pneumococcal carriage in school-aged children and co-habiting relatives and to explore the potential link between the family environment and the sharing of pneumococcal serotypes covered by the vaccine. Oropharyngeal samples of 146 subjects belonging to 36 different family groups were molecularly tested for pneumococcal detection and serotyping. The overall prevalence of pneumococcal carriage was 65.8% (n = 96/146), whereas it was higher among schoolchildren (77.8%, n = 28/36); subjects of seven years of age had the highest odds of being colonized (odds ratio, OR = 5.176; p = 0.145). Pneumococcal serotypes included in the 13-valent conjugate vaccine formulation were largely detected in the study population and multiple serotypes colonization was considerable. Factors relating to a close proximity among people at the family level were statistically associated with pneumococcal carriage (OR = 2.121; p = 0.049), as well as active smoking habit with a clear dose-response effect (ORs = 1.017–3.326). About half of family clusters evidenced similar patterns of carried pneumococcal serotypes and the odds of sustaining a high level of intrafamilial sharing increased with household size (ORs = 1.083–5.000). This study highlighted the potential role played by the family environment in sustaining both the circulation and horizontal transmission of pneumococcus.

Pneumococcal vaccination

PURPOSE OF REVIEW

Pneumococcal diseases (invasive diseases, pneumonia, otitis media, and sinusitis) are among the most frequent preventable infectious diseases carrying a very high morbidity and case fatality rate worldwide. Pneumococcal vaccination is a key element to reduce the global burden of the disease in children and adult population. Our aim is to discuss current knowledge of the epidemiology of pneumococcal disease and pneumococcal vaccines.

RECENT FINDINGS

After the introduction of conjugate vaccines (PCV7 and PCV13), rates of pneumococcal diseases because of vaccine serotypes have decreased considerably among children in the vaccine target and among nonvaccinated children and adults. Results of the Community-Acquired Pneumonia Immunization Trial in Adults demonstrated 45.6% efficacy of PCV13 against the first episode of pneumonia, 45% against first-episode nonbacteremic pneumococcal pneumonia, and 75% against the first episode of invasive pneumococcal diseases in adults older than 65 years. Recommendations for pneumococcal vaccination have changed recently in both the United States and Europe.

SUMMARY

The changing epidemiology of pneumococcal diseases should be closely investigated to assess the effectiveness and the usefulness of the current vaccination policies, and to identify future directions for preventing pneumococcal infections.

Pneumococcus and the Elderly in Italy: A Summary of Available Evidence Regarding Carriage, Clinical Burden of Lower Respiratory Tract Infections and On-Field Effectiveness of PCV13 Vaccination

Streptococcus pneumoniae is currently the leading cause of community-acquired pneumonia (CAP) and lower respiratory tract infections (LRTI) in adults, elderly and high-risk subjects worldwide. The clear benefits of pneumococcal conjugate vaccination in childhood have been accompanied by a decrease of vaccine-serotype invasive diseases among adults in several countries, mainly due to the herd effect mediated by the reduction of vaccine-serotype nasopharyngeal colonization in both age groups, but this reduction in the incidence of pneumonia has not been observed. The "Community Acquired Pneumonia Immunization Trial in Adults" (CAPITA) study provided conclusive evidence about 13-valent pneumococcal conjugate vaccine (PCV13) efficacy in preventing CAP in adults and led Western countries to issue new recommendations for pneumococcal immunization targeting subjects >50 years and high-risk groups, with marked differences with respect to age and/or risk groups immunized, eligibility for reimbursement and national, regional or local implementation. Several Italian regions implemented PCV13 immunization programs in adults and interesting data have been come available in the last years, especially from Liguria, a Northern region with a high and long-lasting pneumococcal vaccine immunological pressure in infants. In this review, currently available evidence from Italy and Liguria regarding pneumococcal carriage, burden of CAP and LRTI, and on-field effectiveness of PCV13 immunization in adults and elderly will be summarized.

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.

Carriage of Streptococcus pneumoniae in aged adults with influenza-like-illness

Incidence of pneumococcal disease is disproportionally high in infants and elderly. Nasopharyngeal colonisation by Streptococcus pneumoniae is considered a prerequisite for disease but unlike in children, carriage in elderly is rarely detected. Here, we tested for S. pneumoniae in nasopharyngeal and saliva samples collected from community-dwelling elderly with influenza-like-illness (ILI). Trans-nasal nasopharyngeal, trans-oral nasopharyngeal and saliva samples (n = 270 per sample type) were collected during winter/spring 2011/2012 from 135 persons aged 60–89 at onset of ILI and 7–9 weeks later following recovery. After samples were tested for pneumococci by conventional culture, all plate growth was collected. DNA extracted from plate harvests was tested by quantitative-PCRs (qPCR) specific for S. pneumoniae and serotypes included in the 13-valent pneumococcal conjugated vaccine (PCV13). Pneumococci were cultured from 14 of 135 (10%) elderly with none of the sampled niches showing superiority in carriage detection. With 76/270 (28%) saliva, 31/270 (11%) trans-oral and 13/270 (5%) trans-nasal samples positive by qPCR, saliva was superior to nasopharyngeal swabs (p<0.001) in qPCR-based carriage detection. Overall, from all methods used in the study, 65 of 135 (48%) elderly carried pneumococci at least once and 26 (19%) at both study time points. The difference between carriage prevalence at ILI (n = 49 or 36%) versus recovery (n = 42 or 31%) was not significant (p = 0.38). At least 23 of 91 (25%) carriage events in 19 of 65 (29%) carriers were associated with PCV13-serotypes. We detected a large reservoir of pneumococci in saliva of elderly, with PCV13-serotype distribution closely resembling the contemporary carriage of serotypes reported in the Netherlands for PCV-vaccinated infants.

[Prevalence of nasal carriage of Staphylococcus aureus and Streptococcus pneumoniae in Primary Care and factors associated with colonization]

OBJECTIVE

To determine (i) the prevalence of Staphylococcus aureus (S.aureus) and Streptococcus pneumoniae (S.pneumoniae) nasal carriage in Primary Health Care patients in area of Barcelona, and (ii) the factors associated with S.aureus and S.pneumoniae colonization.

METHODS

Multi-center cross-sectional study conducted in 2010-2011 with the participation of 27 Primary Health Care professionals. Nasopharyngeal swabs were obtained from 3,969 patients over 4 years of age who did not present with any sign of infection.

DEPENDENT VARIABLES

S.aureus and/or S.pneumoniae carrier state.

INDEPENDENT VARIABLES

socio-demographic characteristics, health status, vaccination status, occupation, and living with children. A descriptive analysis was performed. The prevalence of carriers of S.aureus and/or S.pneumoniae was calculated and logistic regression models were adjusted by age.

RESULTS

In children from 4 to 14 years old, the prevalence of S.aureus carriers was 35.7%, of S.pneumoniae 27.1%, and 5.8% were co-colonized. In adults older than 14 years old, the prevalence was 17.8%, 3.5%, and 0.5%, respectively. In children, S.aureus carrier state was inversely associated with S.pneumoniae carrier state; S.pneumoniae was associated with younger age, and inversely associated with S.aureus carrier state. In adults, being a carrier of S.aureus was associated with male gender, younger age, and a health-related occupation, whereas S.pneumoniae carrier state was associated with living with children under 6 years of age. The proportion of co-colonized carriers was low (1.0%).

CONCLUSIONS

The proportion of S.aureus and S.pneumoniae carriers was higher in children than in adults. Age was the only factor associated with healthy carrier status for S.aureus and for S.pneumoniae.

Safety and tolerability of 13-valent pneumococcal conjugate vaccine in the elderly

BACKGROUND

In September 2011 the European Medical Agency authorized the use of 13-valent pneumococcal conjugate vaccine (PCV13) in adults aged ≥50 years. The same occurred in the US in December 2011 when the Food and Drug Administration approved the use of PCV13 in the same target age-group with indication for the prevention of invasive pneumococcal diseases and community acquired pneumonia sustained by the serotypes contained in the vaccine. The Liguria Region, in Italy, implemented in 2013 an active and free of charge immunization strategy with PCV13 among adults affected by specific risk conditions and the elderly aged ≥70 years.

METHODS

An observational study was performed in order to assess the safety and tolerability of PCV13 among elderly dwelling in the metropolitan area of Genoa, the capital city of Liguria Region. Eligible subjects, who received PCV13 following the public health immunization campaign at the Local Health Unit 3 of Genoa, provided a written informed consent to take part in the study. Eight-hundred-seventy-one subjects were enrolled between October 2013 and May 2014: all were monitored by qualified healthcare personnel for at least 30 min after vaccination at the outpatient clinics, in order to assess any possible sudden reaction. The occurrence of a series of local and systemic solicited reactions and of any unsolicited Adverse Events (AEs) was monitored using a self-administered clinical diary and by regular phone contacts up to 14 and 21 d following immunization, respectively. Moreover, a 6-months follow-up following vaccination was planned in order to monitor Severe Adverse Events (SAEs).

RESULTS

No sudden reaction occurred in vaccinees at the outpatient clinics. Pain (27.4%) was the most frequent reaction reported by subjects at the injection site, while new muscle pain (13.6%), fatigue (10.7%), and headache (9.9%) resulted the most common systemic reactions. Rates of the main reactions reported in this on-field study resulted generally lower than those registered in clinical trials performed in the elderly. The incidence of fever (2.2%) following vaccination was low at values superimposable to that reported in previous studies.

CONCLUSION

This observational study showed a good safety and tolerability of PCV13 among the elderly in routine clinical practice further confirming the evidence coming from clinical trials in the same age-group.

Community-acquired pneumonia caused by carbapenem-resistant Streptococcus pneumoniae: re-examining its prevention and treatment

A 73-year-old man with no significant past medical history or any history of health care visits was hospitalized for pneumonia. Sputum culture revealed multidrug-resistant Streptococcus pneumoniae, even to carbapenems. The patient was later treated successfully with levofloxacin. Throat cultures from his two grandchildren revealed S. pneumoniae with the same susceptibility pattern. Analysis for resistant genes revealed gPRSP (pbp1a + pbp2x + pbp2b gene variants) in both the patient and his grandchildren, none of whom had received pneumococcal vaccines of any kind. This case illustrates the importance of the emergence of carbapenem-resistant S. pneumoniae. Non-rational use of carbapenems for community-acquired infections may be counterproductive. This case also highlights the importance of pneumococcal vaccinations in children and the elderly.

The adult nasopharyngeal microbiome as a determinant of pneumococcal acquisition

BACKGROUND

Several cohort studies have indicated associations between S. pneumoniae and other microbes in the nasopharynx. To study causal relationships between the nasopharyngeal microbiome and pneumococcal carriage, we employed an experimental human pneumococcal carriage model. Healthy adult volunteers were assessed for pneumococcal carriage by culture of nasal wash samples (NWS). Those without natural pneumococcal carriage received an intranasal pneumococcal inoculation with serotype 6B or 23F. The composition of the nasopharyngeal microbiome was longitudinally studied by 16S rDNA pyrosequencing on NWS collected before and after challenge.

RESULTS

Among 40 selected volunteers, 10 were natural carriers and 30 were experimentally challenged. At baseline, five distinct nasopharyngeal microbiome profiles were identified. The phylogenetic distance between microbiomes of natural pneumococcal carriers was particularly large compared to non-carriers. A more diverse microbiome prior to inoculation was associated with the establishment of pneumococcal carriage. Perturbation of microbiome diversity upon pneumococcal challenge was strain specific. Shifts in microbiome profile occurred after pneumococcal exposure, and those volunteers who acquired carriage more often diverted from their original profile. S. pneumoniae was little prominent in the microbiome of pneumococcal carriers.

CONCLUSION

Pneumococcal acquisition in healthy adults is more likely to occur in a diverse microbiome and appears to promote microbial heterogeneity.

Oropharyngeal and nasopharyngeal sampling for the detection of adolescent Streptococcus pneumoniae carriers

Monitoring the dynamics of pneumococcal carriage makes it possible to evaluate the epidemiological characteristics of Streptococcus pneumoniae disease and the theoretical coverage offered by pneumococcal vaccines. It has been demonstrated that the nasopharyngeal (NP) sampling of respiratory secretions is superior to oropharyngeal (OP) sampling for identifying pneumococci carried by younger children, but adult data are conflicting and there are no published studies of adolescents. In order to compare the efficiency of OP and NP sampling in identifying and quantifying S. pneumoniae carriage in healthy adolescents, 2 swab samples were obtained from 530 adolescents aged 15-19 years, the first taken from the posterior pharyngeal wall through the mouth (OP) and the second through the nose (NP). Bacterial genomic DNA was tested for the autolysin-A-encoding gene (lytA) and wzg (cpsA) gene of S. pneumoniae in order to evaluate pneumococcal carrier status. All of the positive cases were serotyped. S. pneumoniae was identified in 35.8% of the OP swabs and 3.5% of the NP swabs (P<0.0001). The serotypes included in the 13-valent pneumococcal conjugate vaccine (PCV13) were found in all but two OP samples (98.9%) and only 64.7% of the NP samples (P<0.0001). The most frequently identified PCV13 serotype in both groups was 19F, followed by serotypes 5 and 9V. In conclusion, OP sampling appeared significantly more effective than NP sampling in identifying and characterizing pneumococcal carrier status in adolescents. This suggests that OP sampling should be used when evaluating the dynamics of pneumococcal carriage among adolescents and the theoretical coverage offered by PCV13.

Immunosenescence and pneumococcal disease: an imbalance in host-pathogen interactions

Respiratory infections are among the most important causes of morbidity and mortality from infectious diseases worldwide. The most common causative bacterium, Streptococcus pneumoniae, frequently colonises the upper respiratory tract, where it resides mostly asymptomatically. Occasionally, however, S pneumoniae can cause severe disease such as pneumonia. Local host immunity is essential to control colonising pathogens by preventing overgrowth, spread, and invasion. However, age-related immune deficits in elderly people, known as immunosenescence, might contribute to increased disease burden. We review present knowledge about immunosenescence in the respiratory tract against Gram-positive bacteria, particularly S pneumoniae. We discuss the possible underdetection of pneumococcal colonisation in elderly people, and suggest changes to present surveillance methods to improve understanding of the relation between colonisation and disease. We conclude that present knowledge about alteration of host-pathogen interactions by immunosenescence in the respiratory tract is insufficient, and that research is needed to enable improved measures for prevention.