Pneumococcal carriage in young children one year after introduction of the 13-valent conjugate vaccine in Italy

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.

Serotypes and Antibiotic Resistance of Streptococcus pneumoniae before and after the Introduction of the 13-Valent Pneumococcal Conjugate Vaccine for Adults and Children in a Rural Area in Japan

The increase in non-vaccine serotypes of Streptococcus pneumoniae and their multidrug resistance have become an issue following the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13). In this study, we investigated the serotypes and drug resistance of S. pneumoniae detected in adult and pediatric outpatients at a hospital in a rural area of Japan between April 2012 and December 2016. Serotypes of the bacterium were identified using the capsular swelling test and multiplex polymerase chain reaction testing of DNA extracted from the specimens. Antimicrobial susceptibility was determined using the broth microdilution method. The serotype 15A was classified using multilocus sequence typing. The results showed that the prevalence of non-vaccine serotypes increased significantly in children from 50.0% in 2012-2013 to 74.1% in 2016 (p ≤ 0.006) and in adults from 15.8% in 2012-2013 to 61.5% in 2016 (p ≤ 0.026), but no increase in drug-resistant isolates was evident. However, an increase in the drug-resistant serotypes 15A and 35B was observed in children. Although isolates of these two serotypes showed cefotaxime susceptibility, cefotaxime resistance was confirmed for the serotype 15A isolates. Future trends in the spread of these isolates should be monitored with caution.

Asymptomatic nasopharyngeal bacterial carriage, multi-drug resistance pattern and associated factors among primary school children at Debre Berhan town, North Shewa, Ethiopia

BACKGROUND

Nasopharyngeal carriage of bacteria is the main source for transmission of pathogens across individuals and horizontal spread of organisms in the community. It is an important risk factor for the acquisition of community-acquired respiratory tract infection. It is the major public health problem among children. The asymptomatic carriage of nasopharyngeal bacteria is different globally, particularly in Africa, carriage is higher in children and decreases with increasing age, 63.2% in children less than 5 years, 42.6% in children 5-15 years, and 28.0% in adults older than 15 years.

OBJECTIVE

The aims of this study was to determine asymptomatic nasopharyngeal bacterial carriage, multi-drug resistance pattern and associated factors among primary school children at Debre Berhan town, North Shewa, Ethiopia.

METHODS

Institutional based cross-sectional study was conducted at Debre Berhan town primary schools from February 1 to April 30, 2021. Primarily, the schools were stratified into two strata, public and private primary schools. From a total of sixteen government and fourteen private primary schools, five government and five private schools were selected by using a simple random sampling technique. Socio-demographic variables and potential risk factors were assessed using a structured questionnaire. A total of 384 nasopharyngeal swab samples were collected using sterile swabs aseptically; and inoculated on Blood agar, Chocolate agar, MacConkey agar, and Mannitol salt agar. The colony was characterized to isolate bacteria, and bacterial identification was performed by Gram reaction, hemolysis patterns, colonial characteristics and pigmentation, catalase test, coagulase test, mannitol fermentation test, oxidase test, fermentation of carbohydrates, H₂S production, motility, formation of indole, triple sugar iron agar (TSI), citrate utilization, lysine decarboxylase or methyl red vogues proskur utilization, urea hydrolysis and satellitism tests. Antimicrobial sensitivity tests were performed by using modified Kirby-Bauer disk diffusion method. Data were entered into statistical package Epi data 4.0.0.6 and transferred to and analyzed using SPSS software version-23. P value of < 0.05 with Odds ratio (OR) and 95% confidence interval (CIs) was considered as statistically significant.

RESULTS

The overall prevalence of nasopharyngeal carriage of bacterial isolate was 35.7% (95% CI 30.7-40.7%). The predominant isolates were Staphylococcus aureus 54.5% followed by coagulase-negative Staphylococcus 35.8%, and Streptococcus pyogens 4.5%. Most bacterial isolates were susceptible to chloramphenicol, ciprofloxacin, gentamycin, nitrofurantoin, azithromycin, ciprofloxacin; and the overall multidrug resistance pattern of isolated bacteria was 62.03% out of 137 bacterial isolates. Numbers of rooms ≤ 2 per house [AOR = 5.88, 95%CI 1.26-27.57], having history of hospitalization [AOR = 4.08, 95%CI 1.45-11.53], passive smoking [AOR = 4.87, 95%CI 1.49-15.97], family size of > 5 members [AOR = 2.17, 95%CI 1.24-3.81], and number of students in the classroom [AOR = 2.35,95%CI 1.37-4.02] were statistically significant associated risk factors for nasopharyngeal bacteria carriage.

CONCLUSION

Asymptomatic nasopharyngeal bacteria carriage in children is alarming for community-acquired infection. The overall multidrug resistance was very high. The risk of the carriage was increased with having a history of passive smoking, being in large family size and number of students per class. Longitudinal follow-up studies would be helpful for better understanding the infection risk in bacterial pathogen carriers.

High Prevalence of Asymptomatic Nasopharyngeal Carriage Rate and Multidrug Resistance Pattern of Streptococcus pneumoniae Among Pre-School Children in North Showa Ethiopia

Background

Streptococcus pneumoniae infection is still the world’s most serious public health problem among children under the age of five. Nasopharyngeal carriage rate of Streptococcus pneumoniae has been identified as an important risk factor for the acquisition of community acquired respiratory tract infection. To date, little is known about the nasopharyngeal infection and antimicrobial susceptibility pattern of Streptococcus pneumoniae among preschool children in Ethiopia.

Objective

The aim of this study was to assess the prevalence of nasopharyngeal carriage and antimicrobial susceptibility pattern of Streptococcus pneumoniae among preschool children.

Methods

A cross-sectional study was conducted from September 2021 to April 2022. A total of 418 preschool children were enrolled using a multistage sampling technique. Nasopharyngeal swab was collected and transported to Medical Microbiology Laboratory at Debre Berhan comprehensive specialized hospital using skim-milk tryptone glucose glycerol transport media. The swab was inoculated on blood agar plates supplemented with 5µg/mL gentamycin and incubated at 37°C for 24–48 hours under 5% CO2 using a candle jar. Identification of Streptococcus pneumoniae was performed using Gram stain, catalase test, optochin test and bile solubility test. Antimicrobial sensitivity tests were done using a modified Kirby-Bauer disk diffusion method. Data were entered into the statistical package Epi data 4.0.0.6 and transferred to and analyzed using SPSS software version-23. A P-value ≤0.05 with 95% CI was considered to be statistically significant.

Results

The prevalence of Streptococcus pneumoniae nasopharyngeal carriage was 29.9% (125/418). The overall rate of multidrug resistance was 86 (68.8%), with tetracycline (68.8%) and TMP-SMX (68%). Among risk factors, young age and passive smoking were associated with pneumococcal carriage.

Conclusion

The present study revealed a substantially lower prevalence of Streptococcus pneumoniae nasopharyngeal carriage. High antimicrobial resistance was observed for most antimicrobial drugs tested. Younger age groups and passive smokers were at risk of Streptococcus pneumoniae nasopharyngeal carriage.

Factors associated with pneumococcal nasopharyngeal carriage: A systematic review

Pneumococcal disease is a major contributor to global childhood morbidity and mortality and is more common in low- and middle-income countries (LMICs) than in high-income countries. Pneumococcal carriage is a prerequisite for pneumococcal disease. Pneumococcal conjugate vaccine reduces vaccine-type carriage and disease. However, pneumococcal carriage and disease persist, and it is important to identify other potentially modifiable factors associated with pneumococcal carriage and determine if risk factors differ between low, middle, and high-income countries. This information may help inform pneumococcal disease prevention programs. This systematic literature review describes factors associated with pneumococcal carriage stratified by country income status and summarises pneumococcal carriage rates for included studies. We undertook a systematic search of English-language pneumococcal nasopharyngeal carriage studies up to 30th June 2021. Peer-reviewed studies reporting factors associated with overall pneumococcal nasopharyngeal carriage in healthy, community-based study populations were eligible for inclusion. Two researchers independently reviewed studies to determine eligibility. Results are presented as narrative summaries. This review is registered with PROSPERO, CRD42020186914. Eighty-two studies were included, and 46 (56%) were conducted in LMICs. There was heterogeneity in the factors assessed in each study. Factors positively associated with pneumococcal carriage in all income classification were young age, ethnicity, symptoms of respiratory tract infection, childcare attendance, living with young children, poverty, exposure to smoke, season, and co-colonisation with other pathogens. Breastfeeding and antibiotic use were protective against carriage in all income classifications. Median (interquartile range) pneumococcal carriage rates differed by income classification, ranging from 51% (19.3-70.2%), 38.5% (19.3-51.6%), 31.5% (19.0-51.0%), 28.5% (16.8-35.4%), (P = 0.005) in low-, lower-middle, upper-middle, and high-income classifications, respectively. Our findings suggest that where measured, factors associated with pneumococcal nasopharyngeal carriage are similar across income classifications, despite the highest pneumococcal carriage rates being in low-income classifications. Reducing viral transmission through vaccination and public health interventions to address social determinants of health would play an important role.

Structural, Genetic, and Serological Elucidation of Streptococcus pneumoniae Serogroup 24 Serotypes: Discovery of a New Serotype, 24C, with a Variable Capsule Structure

Pneumococcal capsules are important in pneumococcal pathogenesis and vaccine development. Although conjugate vaccines have brought about a significant reduction in invasive pneumococcal disease (IPD) caused by vaccine serotypes, the relative serotype prevalence has shifted with the dramatic emergence of serotype 24F in some countries. Here, we describe 14 isolates (13 IPD and 1 non-IPD) expressing a new capsule type, 24C, which resembles 24F but has a novel serological profile. We also describe the antigenic, biochemical, and genetic basis of 24F and 24C and the related serotypes 24A and 24B. Structural studies show that 24B, 24C, and 24F have identical polysaccharide backbones [β-Ribf-(1→4)-α-Rhap-(1→3)-β-GlcpNAc-(1→4)-β-Rhap-(1→4)-β-Glcp] but with different side chains, as follows: 24F has arabinitol-phosphate and 24B has ribitol-phosphate. 24C has a mixture of 24F and 24B repeating units, with the ratio of ribitol to arabinitol being strain dependent. In contrast, the 24A capsule has a backbone without β-Ribf but with arabinitol-phosphate and phosphocholine side chains. These structures indicate that factor-sera 24d and 24e recognize arabinitol and ribitol, respectively, which explains the serology of serogroup 24, including those of 24C. The structures can be genetically described by the bispecificity of wcxG, which is capable of transferring arabinitol or ribitol when arabinitol is limiting. Arabinitol is likely not produced in 24B but is produced in reduced amounts in 24C due to various mutations in abpA or abpB genes. Our findings demonstrate how pneumococci modulate their capsule structure and immunologic properties with small genetic changes, thereby evading host immune responses. Our findings also suggest a potential for new capsule types within serogroup 24.

Pneumococcal Choline-Binding Proteins Involved in Virulence as Vaccine Candidates

Streptococcus pneumoniae is a pathogen responsible for millions of deaths worldwide. Currently, the available vaccines for the prevention of S. pneumoniae infections are the 23-valent pneumococcal polysaccharide-based vaccine (PPV-23) and the pneumococcal conjugate vaccines (PCV10 and PCV13). These vaccines only cover some pneumococcal serotypes (up to 100 different serotypes have been identified) and are unable to protect against non-vaccine serotypes and non-encapsulated pneumococci. The emergence of antibiotic-resistant non-vaccine serotypes after these vaccines is an increasing threat. Therefore, there is an urgent need to develop new pneumococcal vaccines which could cover a wide range of serotypes. One of the vaccines most characterized as a prophylactic alternative to current PPV-23 or PCVs is a vaccine based on pneumococcal protein antigens. The choline-binding proteins (CBP) are found in all pneumococcal strains, giving them the characteristic to be potential vaccine candidates as they may protect against different serotypes. In this review, we have focused the attention on different CBPs as vaccine candidates because they are involved in the pathogenesis process, confirming their immunogenicity and protection against pneumococcal infection. The review summarizes the major contribution of these proteins to virulence and reinforces the fact that antibodies elicited against many of them may block or interfere with their role in the infection process.

Determinants of high residual post-PCV13 pneumococcal vaccine-type carriage in Blantyre, Malawi: a modelling study

BACKGROUND

In November 2011, Malawi introduced the 13-valent pneumococcal conjugate vaccine (PCV13) into the routine infant schedule. Four to 7 years after introduction (2015-2018), rolling prospective nasopharyngeal carriage surveys were performed in the city of Blantyre. Carriage of Streptococcus pneumoniae vaccine serotypes (VT) remained higher than reported in high-income countries, and impact was asymmetric across age groups.

METHODS

A dynamic transmission model was fit to survey data using a Bayesian Markov-chain Monte Carlo approach, to obtain insights into the determinants of post-PCV13 age-specific VT carriage.

RESULTS

Accumulation of naturally acquired immunity with age and age-specific transmission potential were both key to reproducing the observed data. VT carriage reduction peaked sequentially over time, earlier in younger and later in older age groups. Estimated vaccine efficacy (protection against carriage) was 66.87% (95% CI 50.49-82.26%), similar to previous estimates. Ten-year projected vaccine impact (VT carriage reduction) among 0-9 years old was lower than observed in other settings, at 76.23% (CI 95% 68.02-81.96%), with sensitivity analyses demonstrating this to be mainly driven by a high local force of infection.

CONCLUSIONS

There are both vaccine-related and host-related determinants of post-PCV13 pneumococcal VT transmission in Blantyre with vaccine impact determined by an age-specific, local force of infection. These findings are likely to be generalisable to other Sub-Saharan African countries in which PCV impact on carriage (and therefore herd protection) has been lower than desired, and have implications for the interpretation of post-PCV carriage studies and future vaccination programs.

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.

Emergence of an extensively drug-resistant (XDR) Streptococcus pneumoniae serotype 15A by capsular switching

Recently, we have identified an extensively drug-resistant (XDR) Streptococcus pneumoniae serotype 15A isolate from a patient with bacterial meningitis. It belonged to sequence type 8279 (ST8279), a clone identified as XDR serotype 11A isolated in South Korea. We obtained and compared the genome sequences of an XDR 15A and an XDR 11A isolate. The genomes of two XDR isolates were highly identical, except for the capsular polysaccharide (cps) locus and another small region. Capsular switching from 11A to 15A may have occurred via recombination of the cps locus. The emergence of a new XDR clone via capsular switching would be a great concern for public health and in clinical settings.

Rise of multidrug-resistant Streptococcus pneumoniae clones expressing non-vaccine serotypes among children following introduction of the 10-valent pneumococcal conjugate vaccine in Bulgaria

OBJECTIVES

Pneumococcal conjugate vaccines (PCVs) have reduced the incidence of pneumococcal disease, but non-vaccine serotypes are of concern, particularly if antimicrobial-resistant. This study retrospectively evaluated the serotype-specific clonality of paediatric multidrug-resistant (MDR) invasive and non-invasive Streptococcus pneumoniae isolates collected following PCV10 introduction (2011-2017) in Bulgaria.

METHODS

Capsular types, drug resistance patterns and multilocus sequence typing (MLST) of the most common MDR S. pneumoniae serotypes sampled from children were determined.

RESULTS

Overall, the rate of MDR pneumococci was 44.6% (107/240). The most common serotypes among MDR strains were 19F (25.2%), 19A (19.6%), 6C (13.1%), 6A and 23A (6.5% each) and 15A (4.7%), contributing 75.7% of all MDR strains. With the exception of serotype 19F, the remaining serotypes were non-PCV10 types. Among MDR pneumococci, the most frequently found sequence types were ST320 (30.4%; 19A and 19F), ST386 (12.7%; 6C and 6A) and ST8029 (5.1%; 23A). The majority of MDR STs (74.7%) belonged to PMEN clonal complexes, of which the most common were CC320 (Taiwan^19F-14), CC315 (Poland^6B-20) and CC180 (Netherlands³-31), accounting for 43.0%, 13.9% and 5.1%, respectively. In the post-vaccine period, a shift in the genetic structure of serotype 19A was found, with a significant increase of PMEN-14 (CC320) and a concurrent decrease of the major clone Denmark¹⁴-32 (CC230) observed prior to PCV10 introduction in Bulgaria.

CONCLUSIONS

Clonality was found behind the wide distribution of MDR capsular types 19A, 6C, 23A and 3 following vaccine introduction, and a highly multiresistant and virulent clone Taiwan^19F-14/ST320 has emerged as a common pathogen in children.

Prevention of Invasive Pneumococcal Disease: Problems Emerged After Some Years of the 13-Valent Pneumococcal Conjugate Vaccine Use

Starting from 2010, the 13-valent pneumococcal conjugate vaccine (PCV13) was introduced in several countries. This paper discusses some of the problems recently emerged after PCV13 use and their clinical impact. The impact of PCV13 has been relevant and has saved millions of children and adults by severe infectious diseases. However, it seems likely that in the future, effectiveness of the vaccine might be even higher than that presently evidenced. This is because long-term administration of PCV13 to the pediatric population can favor a more extensive reduction of nasopharyngeal colonization with vaccine serotypes of both vaccinated and unvaccinated subjects and further reduce invasive pneumococcal disease in all the individuals (herd immunity). While waiting for new vaccines to be able to overcome the problem of a limited number of pneumococcal strains included in PCV13, it is recommended to increase pneumococcal vaccination coverage in the entire pediatric population.

A Novel Function for the Streptococcus pneumoniae Aminopeptidase N: Inhibition of T Cell Effector Function through Regulation of TCR Signaling

Streptococcus pneumoniae (Spn) causes a variety of disease states including fatal bacterial pneumonia. Our previous finding that introduction of Spn into an animal with ongoing influenza virus infection resulted in a CD8⁺ T cell population with reduced effector function gave rise to the possibility of direct regulation by pneumococcal components. Here, we show that treatment of effector T cells with lysate derived from Spn resulted in inhibition of IFNγ and tumor necrosis factor α production as well as of cytolytic granule release. Spn aminopeptidase N (PepN) was identified as the inhibitory bacterial component and surprisingly, this property was independent of the peptidase activity found in this family of proteins. Inhibitory activity was associated with reduced activation of ZAP-70, ERK1/2, c-Jun N-terminal kinase, and p38, demonstrating the ability of PepN to negatively regulate TCR signaling at multiple points in the cascade. These results reveal a novel immune regulatory function for a bacterial aminopeptidase.

Immunization, Antibiotic Use, and Pneumococcal Colonization Over a 15-Year Period

BACKGROUND

Rates of invasive pneumococcal disease have declined since widespread introduction of pneumococcal conjugate vaccines (PCVs) in the United States. We evaluated the impact of immunization status and recent antibiotic use on an individual child's risk of colonization.

METHODS

This study extends previously reported data from children <7 years of age seen for well child or acute care visits in Massachusetts communities. Nasopharyngeal swabs were collected during 6 surveillance seasons from 2000 to 2014. Parent surveys and medical record reviews confirmed immunization status and recent antibiotic use. We estimated the proportions of children colonized with PCV7-included, additional PCV13-included, and non-PCV13 serotypes. Risk factors for colonization with additional PCV13-included and non-PCV13 serotypes were assessed by using generalized linear mixed models adjusted for clustering by community.

RESULTS

Among 6537 children, 19A emerged as the predominant serotype in 2004, with substantial reductions in 2014. Among non-PCV serotypes, 15B/C, 35B, 23B, 11A, and 23A were most common in 2014. We observed greater odds for both additional PCV13 and non-PCV13 colonization in younger children, those with more child care exposure, and those with a concomitant respiratory tract infection. Adjusted odds for additional PCV13 colonization was lower (odds ratio 0.48 [95% confidence interval 0.31-0.75]) among children up-to-date for PCV13 vaccines. Recent antibiotic use was associated with higher odds of additional PCV13 colonization but substantially lower odds of non-PCV13 colonization.

CONCLUSIONS

Despite the success of pneumococcal vaccines in reducing colonization and disease due to targeted serotypes, ongoing community-based surveillance will be critical to evaluate the impact of interventions on pneumococcal colonization and disease.

Impact of pneumococcal conjugate vaccine (PCV7 and PCV13) on pneumococcal invasive diseases in Italian children and insight into evolution of pneumococcal population structure

BACKGROUND

The use of PCV7 for children immunization was gradually implemented in the Italian regions starting from 2006 and was replaced by PCV13 in 2010-2011. In this study we aimed to assess the PCV impact on invasive pneumococcal diseases (IPD) incidence, serotype distribution and antibiotic resistance in Italian children under 5years old.

METHODS

All IPD cases in children from 5 Italian regions (Emilia-Romagna, Lombardia, A. P. Bolzano, A. P. Trento, and Piemonte) reported through the nationwide surveillance system during 2008-2014 were included in this study. Pneumococcal isolates were subjected to serotyping, antibiotic susceptibility testing, and clonal analysis according to standard methods.

RESULTS

During the study period overall IPD incidence decreased from 7.8 cases/100,000 inhabitants in 2008 to 3.0 cases/100,000 in 2014 (61% decrease, P<0.001). In particular, from 2008 to 2014, PCV7-type IPD decreased from 2.92 to 0.13 cases/100,000 inhabitants (95% decrease, P<0.001) while PCV13-non-PCV7 type IPD decreased from 3.2 to 0.89 cases/100,000 inhabitants (72% decrease, P=0.008). Conversely, non-vaccine serotype (NVS) IPD increased overtime, becoming more common than PCV13 serotype IPD in 2013-2014. Emergent NVS 24F and 12F were the most prevalent in 2014. Antibiotic resistance testing revealed an overall increasing trend in penicillin resistance, from 14% in 2008 to 23% in 2014. Erythromycin resistance showed a downward trend, from 38% in 2008 to 27% in 2014. While in 2008 PCV13 serotypes were the major responsible for antibiotic resistance, during the following years antimicrobial resistance due to NVS increased, mainly as a result of expansion of pre-existing clones.

CONCLUSIONS

Both PCVs led to a substantial decrease in vaccine-related IPD incidence in the children population. However NVS-related IPD increased, becoming the most prevalent in the last two-years period. Continuous surveillance is an essential tool to monitor evolution of pneumococcal population causing IPD in children.

Serotype distribution of Streptococcus pneumoniae causing invasive disease in children in the post-PCV era: A systematic review and meta-analysis

BACKGROUND

Routine immunisation with pneumococcal conjugate vaccines (PCV7/10/13) has reduced invasive pneumococcal disease (IPD) due to vaccine serotypes significantly. However, an increase in disease due to non-vaccine types, or serotype replacement, has been observed. Serotypes' individual contributions to IPD play a critical role in determining the overall effects of PCVs. This study examines the distribution of pneumococcal serotypes in children to identify leading serotypes associated with IPD post-PCV introduction.

METHODS

A systematic search was performed to identify studies and surveillance reports (published between 2000 and December 2015) of pneumococcal serotypes causing childhood IPD post-PCV introduction. Serotype data were differentiated based on the PCV administered during the study period: PCV7 or higher valent PCVs (PCV10 or PCV13). Meta-analysis was conducted to estimate the proportional contributions of the most frequent serotypes in childhood IPD in each period.

RESULTS

We identified 68 studies reporting serotype data among IPD cases in children. We analysed data from 38 studies (14 countries) where PCV7 was administered and 20 (24 countries) where PCV10 or PCV13 have been introduced. Studies reported early and late periods of PCV7 administration (range: 2001∓13). In these settings, serotype 19A was the most predominant cause of childhood IPD, accounting for 21.8% (95%CI 18.6∓25.6) of cases. In countries that have introduced higher valent PCVs, study periods were largely representative of the transition and early years of PCV10 or PCV13. In these studies, the overall serotype-specific contribution of 19A was lower (14.2% 95%CI 11.1∓18.3). Overall, non-PCV13 serotypes contributed to 42.2% (95%CI 36.1∓49.5%) of childhood IPD cases. However, regional differences were noted (57.8% in North America, 71.9% in Europe, 45.9% in Western Pacific, 28.5% in Latin America, 42.7% in one African country, and 9.2% in one Eastern Mediterranean country). Predominant non-PCV13 serotypes overall were 22F, 12F, 33F, 24F, 15C, 15B, 23B, 10A, and 38 (descending order), but their rank order varied by region.

CONCLUSION

Childhood IPD is associated with a wide number of serotypes. In the early years after introduction of higher valent PCVs, non-PCV13 types caused a considerable proportion of childhood IPD. Serotype data, particularly from resource-limited countries with high burden of IPD, are needed to assess the importance of serotypes in different settings. The geographic diversity of pneumococcal serotypes highlights the importance of continued surveillance to guide vaccine design and recommendations.

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.

Nasopharyngeal Pneumococcal Carriage among Healthy Children in Cyprus Post Widespread Simultaneous Implementation of PCV10 and PCV13 Vaccines

The objective of the study was to describe the incidence of pneumococcal nasopharyngeal carriage, serotype distribution and antibiotic resistance profile of pneumococcal nasopharyngeal isolates in healthy children aged 6 to 36 months following the implementation of conjugate vaccines. A nasopharyngeal swab was collected from 1105 healthy children following a stratified random sampling between September 2013 and April 2014. Demographics, vaccination status and data on possible risk factors were recorded. Isolates were serotyped and tested for antibiotic susceptibility. The nasopharyngeal carriage rate was 25.3%. Among 1105 children enrolled, 393 had received PCV13 and 685 PCV10. The prevailing isolated serotypes were: 23A (14.3%), 15A (8.9%), 6C (8.6%), 23B (7.5%), 19A (5.4%) and 15B (5%). The proportion of non-vaccine serotypes, PCV10 serotypes, PCV13 additional serotypes (3, 6A, 19A) was 76.8%, 2.1% and 10.4% respectively. Although children, who were fully or partially vaccinated with PCV13, were 63% less likely to be colonized with additional PCV13 serotypes compared to those vaccinated with PCV10, the difference is not significant (95%Cl = 0.14–1.02, p = 0.053). The highest antibiotic non-susceptible rates were found for erythromycin (28.2%) and penicillin (27.9%). The overall multidrug resistance rate was 13.2%, with serotypes 24F (4/6), 15A (14/25) and 19A (6/15) being the main contributors. Carriage rate was similar between children vaccinated with PCV10 or PCV13. The high incidence of 15A serotype which is also multidrug resistant should be underlined. Ongoing surveillance is needed to monitor the dynamics on nasopharyngeal carriage.

Effectiveness of Pneumococcal Conjugate Vaccines (PCV7 and PCV13) against Invasive Pneumococcal Disease among Children under Two Years of Age in Germany

Background

In this study we calculate the effectiveness of pneumococcal conjugate vaccines (PCV) against invasive pneumococcal disease (IPD) among children under the age of two years using the indirect cohort method. We also discuss the timeliness of vaccination and the residual cases of vaccine type IPD.

Methods and Findings

From July 2006 until June 2015, 921 IPD cases were reported and for 618 children (67.1%), the vaccination status at the time of infection could be accurately determined. Of these, 379 (61.3%) were vaccinated and 239 (38.7%) were not vaccinated. The adjusted vaccine effectiveness (VE) of PCV7 for all included serotypes + 6A was 80% (95% CI: 63–89) for at least one dose, 97% (89–100) after three primary doses (post primary) and 95% (57–100) post booster. The adjusted overall VE of PCV13 was 86% (74–93) for at least one dose, 85% (62–94) post primary and 91% (61–99) post booster. For the additional serotypes included in PCV13, the adjusted VE was 82% (66–91), 80% (46–93) and 90% (54–98) respectively. The serotype specific VE for at least one dose was high for serotypes 1 (83%; 15–97), 3 (74%; 2–93), 7F (84%; 18–98) and 19A (77%; 47–90). Only 39.5% of children with IPD obtained their first dose of PCV7 according to schedule (2^nd dose: 32.9%, 3^rd dose: 22.0%, booster dose: 63.6%). For children vaccinated with PCV13 values were slightly better: 43.8%, 33.5%, 26.3% and 74.3% respectively. Among 90 residual cases with PCV7 serotypes, 73 (81.1%) were in unvaccinated children, and 15 (16.7%) in children who had not obtained the number of doses recommended for their age, and only two (2.2%) in children vaccinated according to age. Of 82 cases with PCV13 serotypes occurring after the switch from PCV7 to PCV13, 56 (68.3%) were not vaccinated, 22 (26.8%) were incompletely vaccinated, and four (4.9%) were vaccinated according to age.

Conclusions

Our data show a high effectiveness of pneumococcal conjugate vaccination in Germany. However, the administration of vaccine doses among children with IPD is often delayed, resulting in many vaccine type cases in non- or incompletely-vaccinated children. Whether the recently-implemented change to a 2+1 schedule will improve the timeliness of vaccination should be subject to careful monitoring.

Unaltered pneumococcal carriage prevalence due to expansion of non-vaccine types of low invasive potential 8years after vaccine introduction in Stockholm, Sweden

OBJECTIVE

To evaluate the carriage prevalence, serotype distribution, and antibiotic resistance for pneumococcal carriage isolates collected 4-8years after introduction of pneumococcal conjugate vaccines (PCVs) in Stockholm, Sweden, and to identify risk factors for carriage and calculate the invasive disease potential for emerging serotypes.

METHODS

Nasopharyngeal aspirates were collected from 3024 children aged 0-<5years at regular visits at 23 Child Health Centers in Stockholm County in 2011-2015, and from 787 parents in 2014-2015. The invasive disease potential was calculated for serotypes using invasive disease isolates from 824 patients of all ages identified in the Stockholm County during the same time period as the carriage isolates.

RESULTS

A total carriage prevalence of 30% did not change during the study period. Non-vaccine types (NVT) dominated (94% by 2015) and the most common serotypes in descending order were 11A, 23B, 35F and 21. Risk factors for carriage were: age ⩾3months-<3years, having siblings, attending day-care and having travelled abroad the last 3months. Antibiotic resistance remained low. The invasive disease potential was high for NVT 8, 9N, 12F, and 22F, while low for a majority of emerging NVTs in carriage.

CONCLUSION

The carriage prevalence remained the same 4-8years after vaccine introduction, but serotype replacement became almost complete. A majority of emerging NVTs in carriage showed a low invasive disease potential. Carriage studies are an important complement to invasive disease surveillance to understand the full effect of PCV vaccine programs.

Macrolide resistance in pneumococci-is it relevant?

Macrolide antibiotics are widely used for a range of indications, including pneumonia. Both high-level and low-level resistance to macrolides is increasing in pneumococci globally. Macrolide resistance in pneumococci is of limited clinical relevance where ß-lactams remain the mainstay of treatment, such as for moderate/severe pneumonia; however, data suggest that macrolides may not be able to be relied on as monotherapy for serious pneumococcal infections.

Nonencapsulated Streptococcus pneumoniae: Emergence and Pathogenesis

While significant protection from pneumococcal disease has been achieved by the use of polysaccharide and polysaccharide-protein conjugate vaccines, capsule-independent protection has been limited by serotype replacement along with disease caused by nonencapsulated Streptococcus pneumoniae (NESp). NESp strains compose approximately 3% to 19% of asymptomatic carriage isolates and harbor multiple antibiotic resistance genes. Surface proteins unique to NESp enhance colonization and virulence despite the lack of a capsule even though the capsule has been thought to be required for pneumococcal pathogenesis. Genes for pneumococcal surface proteins replace the capsular polysaccharide (cps) locus in some NESp isolates, and these proteins aid in pneumococcal colonization and otitis media (OM). NESp strains have been isolated from patients with invasive and noninvasive pneumococcal disease, but noninvasive diseases, specifically, conjunctivitis (85%) and OM (8%), are of higher prevalence. Conjunctival strains are commonly of the so-called classical NESp lineages defined by multilocus sequence types (STs) ST344 and ST448, while sporadic NESp lineages such as ST1106 are more commonly isolated from patients with other diseases. Interestingly, sporadic lineages have significantly higher rates of recombination than classical lineages. Higher rates of recombination can lead to increased acquisition of antibiotic resistance and virulence factors, increasing the risk of disease and hindering treatment. NESp strains are a significant proportion of the pneumococcal population, can cause disease, and may be increasing in prevalence in the population due to effects on the pneumococcal niche caused by pneumococcal vaccines. Current vaccines are ineffective against NESp, and further research is necessary to develop vaccines effective against both encapsulated and nonencapsulated pneumococci.

Prevalence of antimicrobial resistant Streptococcus pneumoniae serotype 11A isolates in Korea, during 2004-2013, due to the increase of multidrug-resistant clone, CC166

Since the introduction of the pneumococcal conjugate vaccine (PCV7) in Korea in 2003, the proportion of non-vaccine serotypes has increased. Among non-vaccine serotypes, serotype 11A is highly prevalent in Korea. We investigated the prevalence and characteristics of Streptococcus pneumoniae serotype 11A isolates in a Korean tertiary-care hospital, during 2004-2013. A total of 1579 non-duplicate clinical S. pneumoniae isolates, collected from 2004 to 2013, were included in this study. Serotype was determined by the capsular Quellung method, and in vitro susceptibility testing was performed by broth microdilution method. Multilocus sequence typing was performed to determine the genotypes of the S. pneumoniae isolates. We identified 90 serotype 11A isolates (5.7%). During this period, the proportion of serotype 11A has increased from 3.2% up to 13.2% (in 2012). Among the serotype 11A isolates, two main clonal complexes (CCs), CC166 and CC99, were identified. The increase of serotype 11A was mainly due to the increase of CC166 isolates, which have high antimicrobial resistance rates. In addition, we identified that 14 isolates, belonging to ST8279, ST9875, and ST3598 of CC166, were non-susceptible to all antimicrobial agents tested in this study. We identified the increase of S. pneumoniae serotype 11A in Korea, which mainly due to the expansion of a resistant clonal group, CC166.

Carriage of Haemophilus influenzae is associated with pneumococcal vaccination in Italian children

BACKGROUND

The pneumococcal population changes observed after the implementation of children immunization with pneumococcal conjugative vaccines (PCV) might have affected the composition of the microbial flora inhabiting the same ecological niche of Streptococcus pneumoniae. The aim of this study was to investigate the effect of PCV immunization, (PCV7 or PCV13), on S. pneumoniae and Haemophilus influenzae colonization in young children in Italy.

METHODS

Nasopharyngeal swabs were obtained from 301 children under 6 years of age (vaccinated or unvaccinated with PCV) during the period January-April 2012. Presence of S. pneumoniae and H. influenzae was investigated using conventional cultural methods. S. pneumoniae isolates were serotyped by the Quellung reaction; capsular type of H. influenzae isolates was determined by PCR. The pattern of associations between the two species and potential risk factors were investigated by a Structural Equation Modelling (SEM) analysis.

RESULTS

The prevalence of carriage was 31.56% and 43.18% for S. pneumoniae and H. influenzae, respectively. The majority of S. pneumoniae isolates belonged to non vaccine serotypes (non PCV13-types 81.1%) while H. influenzae isolates were all non-typeable. SEM analysis revealed a synergistic association between S. pneumoniae and H. influenzae colonization (rho: 0.27; 95%CI: 0.09-0.46; p=0.004). In addition, children vaccinated with PCV, either with PCV7 (coef 0.43; 95%CI: 0.07-0.79; p=0.021) or with PCV13 (coef: 0.45; 95%CI: 0.08-0.82; p=0.018), were more likely to be colonized by H. influenzae.

CONCLUSIONS

Pneumococcal vaccination increased H. influenzae nasopharyngeal carriage in children. This result highlights that an indirect effect of PCV vaccination can be perturbation of the nasopharyngeal flora. In the era of higher-valent pneumococcal vaccines, surveillance of carriage is crucial to monitor alterations in the bacterial ecosystem, thus preventing possible clinical problems.

Antimicrobial Susceptibility/Resistance of Streptococcus Pneumoniae

INTRODUCTION

Pneumococcal infections are a major cause of morbidity and mortality worldwide, whose treatment is threatened with an increase in the number of strains resistant to antibiotic therapy.

GOAL

The main goal of this research was to investigate the presence of antimicrobial susceptibility/resistance of S. pneumoniae.

MATERIAL AND METHODS

Taken are swabs of the nose and nasopharynx, eye and ear. In vitro tests that were made in order to study the antimicrobial resistance of pneumococci are: disk diffusion method and E-test.

RESULTS

The resistance to inhibitors of cell wall synthesis was recorded at 39.17%, protein synthesis inhibitors 19.67%, folate antagonists 47.78% and quinolone in 1.11%. S. pneumoniae has shown drug resistance to erythromycin in 45%, clindamycin in 45%, chloramphenicol-0.56%, rifampicin-6.11%, tetracycline-4.67%, penicillin-G in 4.44%, oxacillin in 73.89%, ciprofloxacin in 1.11% and trimethoprim-sulfamethoxazole in 5.34% of cases.

CONCLUSION

The highest resistance pneumococcus showed to erythromycin, clindamycin and trimethoprim-sulfamethoxazole and these should be avoided in the treatment. The least resistance pneumococcus showed to tetracycline, rifampicin, chloramphenicol, penicillin-G and ciprofloxacin.

Emerging, Non-PCV13 Serotypes 11A and 35B of Streptococcus pneumoniae Show High Potential for Biofilm Formation In Vitro

Background

Since the use of pneumococcal conjugate vaccines PCV7 and PCV13 in children became widespread, invasive pneumococcal disease (IPD) has dramatically decreased. Nevertheless, there has been a rise in incidence of Streptococcus pneumoniae non-vaccine serotypes (NVT) colonising the human nasopharynx. Nasopharyngeal colonisation, an essential step in the development of S. pneumoniae-induced IPD, is associated with biofilm formation. Although the capsule is the main pneumococcal virulence factor, the formation of pneumococcal biofilms might, in fact, be limited by the presence of capsular polysaccharide (CPS).

Methodology/Principal Findings

We used clinical isolates of 16 emerging, non-PCV13 serotypes as well as isogenic transformants of the same serotypes. The biofilm formation capacity of isogenic transformants expressing CPSs from NVT was evaluated in vitro to ascertain whether this trait can be used to predict the emergence of NVT. Fourteen out of 16 NVT analysed were not good biofilm formers, presumably because of the presence of CPS. In contrast, serotypes 11A and 35B formed ≥45% of the biofilm produced by the non-encapsulated M11 strain.

Conclusions/Significance

This study suggest that emerging, NVT serotypes 11A and 35B deserve a close surveillance.

A longitudinal study of streptococcus pneumoniae carriage in healthy children in the 13-valent pneumococcal conjugate vaccine era

Few epidemiological data are available after the introduction of the 13-valent pneumococcal vaccine (PCV13) in 2010. We performed repeat nasopharyngeal swabs and evaluated the serotype distribution of Streptococcus pneumoniae (SP) and its association with PCV13 vaccine status in healthy Italian children aged 3-59 months. SP serotypes were assessed by the Quellung reaction. 618 children appropriately (28%) or incompletely (72%) vaccinated for age with PCV13 were available at baseline (T0). 515 were re-evaluated at 6 months from baseline (T6) and 436 at 12 months from baseline (T12). The percentage of appropriately vaccinated subjects at T0, T6 and T12 was 28%, 67% and 92%, respectively. Random effects logistic regression models with robust 95% confidence intervals was used to estimate the time-related changes in SP and PCV13 carriage and marginal probabilities were obtained from such models. The age-corrected probability of SP carriage was 0.31 (95% CI 0.22 - 0.41) at T0, 0.32 (0.24 - 0.40) at T6 and 0.28 (0.20 - 0.35) at T12. The probability of PCV13 serotypes carriage was 0.025 (0.001 - 0.050) at T0, 0.018 (0.001 - 0.039) at T6 and 0.010 (0.001 - 0.023) at T12. A decrease in PCV13 serotypes and a shift in non-PCV13 serotypes colonization was observed. In particular, the 15A serotype accounted for 4%, 8% and 23% of SP isolates at T0, T6 and T12, respectively. In conclusion, the benefits of the PCV13 vaccination on SP carriage increase with increasing coverage rates. The shift of SP isolates toward non-PCV13 serotypes needs to be studied further.

Characterization of Streptococcus pneumoniae clones from paediatric patients with cystic fibrosis

The role of Streptococcus pneumoniae in cystic fibrosis (CF) is poorly understood. The pneumococcal population has changed over time after the introduction of the heptavalent conjugate vaccine (PCV7) and, more recently, the 13-valent conjugate vaccine (PCV13). Although serotypes and clones causing invasive pneumococcal disease or colonizing healthy children have been extensively analysed, little is known so far on the serotypes and clones of pneumococci in CF patients. The aim of this work was to investigate serotypes, antibiotic susceptibilities, genotypes and biofilm production of CF pneumococcal isolates. Overall, 44 S. pneumoniae strains collected from 32 paediatric CF patients from January 2010 to May 2012 in a large Italian CF Centre were tested for antimicrobial susceptibility testing by Etest, serotyped by the Quellung reaction and genotyped by a combination of different molecular typing methods, including pbp gene restriction profiling, pspA restriction profiling and sequencing, PFGE and multilocus sequence typing. Biofilm production by pneumococcal strains was also assessed. Penicillin non-susceptibility was 16 %. High resistance rates (>56 %) were observed for erythromycin, clindamycin and tetracycline. The most frequent serotype recovered was serotype 3 (31.8 %). The coverage of PCV7 and PCV13 was 6.8 and 47.7 %, respectively. More than 80 % of CF strains belonged to Pneumococcal Molecular Epidemiology Network (PMEN) reference clones, the most common being Netherlands(3)-ST180 (28.2 %), and Greece(21)-30/ST193 (15.4 %). All strains produced biofilm in vitro, although with large variability in biofilm formation efficiency. No correlation was found between biofilm levels and serotype, clone or antibiotic resistance. The high isolation rate of antibiotic-resistant serotype 3 pneumococci from CF patients suggests that PCV13 could increase protection from pneumococcal colonization and infection.

Dynamics of pneumococcal carriage among day-care center attendees during the transition from the 7-valent to the higher-valent pneumococcal conjugate vaccines in Greece

BACKGROUND

In Greece recently, higher-valent pneumococcal conjugate vaccines (PCVs) replaced the 7-valent (PCV7); the 10-valent (PCV10) became available in May 2009 and the 13-valent (PCV13) in June 2010.

METHODS

We investigated the nasopharyngeal colonization with Streptococcus pneumoniae in day-care center attendees in Athens and the prefecture of Viotia. Between December 2010 and June 2011, nasopharyngeal cultures were obtained 4 times, at enrollment and then every 6 to 8 weeks.

RESULTS

Among the 233 children, 225 (96.6%) had been vaccinated with ≥1 dose of PCV7. One tenth of the PCV7 vaccinated attendees had also received ≥1 dose of PCV13 or PCV10. During the 4 samplings, 358 isolates were recovered from a total of 874 samples. Of the 233 children, 183 (78.5%) were found to carry S. pneumoniae at least once. The overall serotype distribution among carriers was similar regardless of the time lapsed since the last PCV7 dose. A high frequency of 19A (17.1%) coincided with a low frequency of 19F (1.4%). Non-PCV13 serotypes accounted for 73.1% of the isolates; 23B, 15B/C, 16F, 21, 11A, 15A, 6C, 10A, 22F and 23A were the most common. Among attendees aged 24-59 months (median age 42 months), prolonged carriage of a non-PCV13 serotype was relatively common, mainly for 21 and 16F. One out of 4 cases of colonization with the prevalent non-PCV13 serotypes was followed by persistent carriage for 5 to 14 weeks.

CONCLUSIONS

During this period of transition to the higher-valent PCVs in the day-care center setting, non-PCV13 serotypes dominated and exhibited prolonged colonization. The frequency and the duration of prolonged carriage tends to be increased, if sampling frequency increases and the carriage time before and after positive cultures is taken into consideration. Further studies regarding the fitness of the colonizing non-PCV13 serotypes will likely to be seen in the future.

Evolving role of 13-valent pneumococcal conjugate vaccine in clinical practice

Since the introduction of 7-valent pneumococcal conjugate vaccine (PCV7), PCVs with extended coverage have become available, and there is emerging global evidence that these vaccines, in particular PCV13, have further reduced rates of invasive pneumococcal disease compared with PCV7. The present article aims to address emerging topics related to PCV13 use in routine clinical practice; specifically: (1) the potential role of high-valent PCVs in reducing pneumococcal disease burden; (2) the impact of PCVs on nasopharyngeal carriage and how this may contribute to reductions in otitis media and pneumonia, as well as the prevalence of resistant pneumococcal strains; (3) new PCV13 indications and (4) importance of schedule adherence for PCV in the prevention of cases of vaccine serotype-specific invasive pneumococcal disease. The beneficial effects of PCVs in protecting individuals from a wide spectrum of pneumococcal diseases can be increased by improving the vaccine coverage and adhering to the recommended vaccination schedules. There is increasing evidence that PCV13 has reduced much of the post-PCV7 burden of pneumococcal diseases in the pediatric community, including reducing pneumococcal colonization and the incidence of invasive pneumococcal disease and mucosal diseases. This has also led to a reduction in antibiotic-resistant pneumococcal diseases. The role of PCV13 in clinical practice is evolving, with PCV13 now available for children and adolescents between the ages of 6 weeks and 17 years, thus ensuring that children in all age groups can be protected against vaccine-serotype pneumococcal diseases. Continued surveillance is warranted to monitor the impact of PCV13 on disease burden.

Identification of Streptococcus pneumoniae serotype 11E, serovariant 11Av and mixed populations by high-resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy and flow cytometric serotyping assay (FCSA)

Background

Recent studies have identified Streptococcus pneumoniae serotype 11E and serovariant 11Av among isolates previously typed as 11A by classical serotyping methods. Serotype 11E and serovariant 11Av differ from serotype 11A by having totally or partially inactive wcjE, a gene in cps locus coding for an O-acetyl transferase. Serotype 11E is rare among carriage isolates but common among invasive isolates suggesting that it survives better during invasion. Aim of this work was to investigate the epidemiology of serotype 11A in a pneumococcal collection using a new serotyping approach based on High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HR-MAS NMR) spectroscopy to distinguish serotypes 11A and 11E.

Methods

A collection of 48 (34 invasive and 14 carriage) S. pneumoniae isolates from Italy, previously identified as serotype 11A by the Quellung reaction, were investigated by wcjE sequencing, HR-MAS NMR spectroscopy and the reference flow cytometric serotyping assay (FCSA) based on monoclonal antibodies.

Results

HR-MAS NMR spectra from serotypes 11A and 11E showed different NMR peaks indicating that HR-MAS NMR could be used to distinguish these serotypes, although HR-MAS NMR could not distinguish serotype 11Av from serotype 11E unambiguously. Thirty-eight isolates were confirmed to be serotype 11A, 8 isolates with a mutated wcjE were serotype 11E, 1 isolate belonged to serovariant 11Av, and 1 isolate was a mixed population 11A/11Av. All 11E isolates were identified among invasive isolates.

Conclusions

We proved that HR-MAS NMR can be of potential use for pneumococcal serotyping. The detection of serotype 11E among invasive isolates in our collection, supports previous epidemiological studies suggesting that mutations in wcjE can represent a mechanism promoting pneumococcal survival during invasion. The discovery of a spectrum of immunochemical diversity within established serotypes should stimulate efforts to develop new serotyping approaches.