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

Invasiveness potential of pneumococcal serotypes in children after introduction of PCV13 in Blantyre, Malawi

INTRODUCTION

The introduction of PCV13 to the Malawi infant immunization schedule in 2011 has been associated with reduced disease from Streptococcus pneumoniae. Improved understanding of serotypes with high invasive potential can guide future vaccination interventions. We aimed to estimate pneumococcal serotypes associated with acute respiratory infection (ARI) and invasive pneumococcal disease (IPD) in hospitalized children in Blantyre, Malawi.

METHODS

We analysed data from healthy children under 5 years in the community in Blantyre and children admitted to Queen Elizabeth Central Hospital with ARI between 2015 and 2018. Nasopharyngeal swabs from children were tested for S. pneumoniae and serotyped by latex agglutination if positive. We analysed culture-positive blood and cerebrospinal fluid samples from admitted children between 2012 and 2018 to identify cases of IPD after the introduction of PCV13. We calculated the age-adjusted odds ratio (OR) of carriage for S. pneumoniae vaccine serotypes (VT) comparing those with ARI to healthy children. We also calculated age-adjusted ORs comparing serotypes causing IPD to carriage in the community with OR > 1 indicating high invasive potential.

RESULTS

Serotypes 5 (OR 24.73 [95% CI 7.90-78.56] p < 0.001), 1 (OR 23.38 [95% CI 9.75-56.06] p < 0.001), and 6B (OR 4.73 [95% CI 1.66-11.64] p = 0.001) had high invasive potential. Serotype 6B was no longer significant (OR 1.34 [95% CI 0.07-6.87] p = 0.777) in a sensitivity analysis accounting for year of recruitment. The prevalence of S. pneumoniae carriage in the community was 72.6% [95% CI 71.3-74.0] (3078/4238) and 23.4% (719/3078) of positive community samples were VT. The carriage prevalence in those hospitalised with ARI was 45.5% [95% CI 42.1-48.9] (389/855) and 43.8% of hospital attendees reported antibiotic use prior to admission. We did not identify significant associations with carriage of any serotypes in those with ARI.

CONCLUSIONS

Pneumococcal serotypes 5 and 1 are associated with high invasive potential. Despite high community pneumococcal carriage, pre-hospital antibiotic usage likely reduces pneumococcal detection among children admitted in this setting and further research is needed to investigate serotypes associated with ARI. Data from this study can guide future preventative vaccination strategies in Malawi.

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.

Nasopharyngeal Carriage in Children After the Introduction of Generalized Infant Pneumococcal Conjugate Vaccine Immunization in Germany

Epidemiological data on nasopharyngeal (NP) bacterial carriage in children in Germany are scarce. We prospectively characterized NP colonization to evaluate the impact of pneumococcal immunization. We longitudinally collected NP swabs from 2-month-old infants (visit 1; V1) at eight representative pediatric offices 10/2008-06/2009. The second swabs were taken at age 9–12 months (V2); the third swab was taken 3–6 months after the booster vaccination at age 17–19 months (V3), and the fourth swab (V4) at age 59–61 months. Samples were broth enriched, cultured for bacteria, and isolates were serotyped. Demographic risk factors for colonization were evaluated. Among 242 vaccinees, bacterial NP carriage increased with age [from 27.2% (V1) to 70.1% (V4)]; leading isolates were S. pneumoniae, H. influenzae, M. catarrhalis, and S. pyogenes. Overall pneumococcal carriage increased [14.7% (V1), 31.5% (V2), 34.8% (V3), 42.2% (V4)], being even greater among day-care attendees. Serotype distribution changed during the study period, with vaccine serotypes declining. At visit 4, 10-valent pneumococcal conjugate vaccine (PCV10) serotypes were no longer among the NP flora, while some serotypes unique to 13-valent pneumococcal conjugate vaccine (PCV13; 3 and 19A) were found. In Germany, universal infant PCV immunization was associated with an almost complete eradication of PCV-serotypes and concomitant increase of non-PCV-serotypes, mainly 11A, 22F, and 23A.

Nasopharyngeal pneumococcal carriage in healthy Turkish children after 13-valent conjugated pneumococcal vaccine implementation in the national immunization program

BACKGROUND

In Turkey, pneumococcal conjugated vaccine (PCV) was introduced to the national immunization program as PCV7 in 2008, and was replaced with PCV13 in 2011. The aims of this study were to investigate the effects of PCV13 on nasopharyngeal pneumococcal carriage (NPC) by determining the serotype distribution, and to identify risk factors for carriage, in healthy Turkish children.

METHODS

This prospective study was conducted on 500 healthy children aged 0-13 years between April and November 2014. Nasopharyngeal swab samples were taken, and molecular method for capsular serotyping was performed by multiplex PCR.

RESULTS

Of 500 children, 43.4% were unvaccinated with a PCV (7- or 13-valent), 56.6% were vaccinated and The NPC rate was found to be 9.8%. Of 49 positive Streptococcus pneumoniae isolates, 26 (53%) were PCV13 vaccine strains (VSs), and 17 (34.7%) were non-VS. Six isolates (12.2%) were not typeable by the method applied. The most common serotypes detected were serotype 3 (18.3%), serotype 19F (14.2%), serotype 6A/B (8.1%), serotype 11A (8.1%), and serotype 15B (8.1%). The total coverage rate of the PCV13 serotypes was 60.4%.

CONCLUSION

A significant decrease in carriage rate was detected within three years after the introduction of PCV13 in Turkey. However, the nasopharyngeal carriage of PCV13 strains was found to be interestingly high.

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.

Changes in the Serotype Distribution among Antibiotic Resistant Carriage Streptococcus pneumoniae Isolates in Children after the Introduction of the Extended-Valency Pneumococcal Conjugate Vaccine

This study investigated the serotype distribution and antimicrobial resistance of 3,820 nasopharyngeal Streptococcus pneumoniae isolates from infants and children who presented with respiratory symptoms at Seoul National University Children's Hospital from July 2010 to June 2015 after the introduction of the extended-valency pneumococcal conjugate vaccines (PCVs). Serotypes and antimicrobial susceptibility were determined using the Quellung reaction and E-test, respectively. S. pneumoniae was isolated from 397 (10.4%) specimens. The most common serotypes were 19A (14.0%), 23A (12.8%), 15B/C (10.7%), 11A (10.1%), 6C (7.8%), and 6A (6.3%) among the typeable pneumococci (n = 335). The PCV serotype proportions significantly decreased (59.1% in 2010/11 to 17.0% in 2014/15, P < 0.001), whereas the non-PCV serotype proportions significantly increased (40.9% in 2010/11 to 83.0% in 2014/15, P < 0.001). The non-susceptibility rates for penicillin (oral), penicillin (parenteral, non-meningitis), cefotaxime, and erythromycin were 97.8%, 22.8%, 27.7%, and 95.5%, respectively. The proportions of PCV serotypes responsible for non-susceptibility to penicillin (parenteral, non-meningitis) and multidrug resistance significantly decreased (80.8% to 21.1%, P < 0.001 and 64.3% to 12.3%, P < 0.001, respectively), whereas the non-PCV serotype proportions significantly increased (19.2% to 78.9%, P < 0.001 and 35.7% to 87.7%, P < 0.001, respectively). Serotypes 23A and 15B/C demonstrated significant proportional increase among the antibiotics resistant strains. Thus, the PCV serotype proportions decreased and the non-PCV serotype proportions increased among nasopharyngeal carriage pneumococci after the introduction of extended-valency PCVs in Korea. Antimicrobial non-susceptibility rates for penicillin and erythromycin remain high despite the decrease in the proportion of PCV serotypes responsible for antimicrobial resistance over time.

Pneumococcal serotype distribution: A snapshot of recent data in pediatric and adult populations around the world

S. pneumoniae infection remains a serious public health concern despite the availability of vaccines covering up to 23 of more than 94 known serotypes. The purpose of the present study was to monitor recent serotype distribution data. PubMed, EMBASE, Cochrane Reviews and Ingenta databases were searched. Serotype data covering invasive pneumococcal disease (IPD) and non-IPD were extracted from articles published from March 2014 to March 2015. Fifty-nine studies presented pneumococcal serotype prevalence by specific age categories. Most prevalent serotypes not covered by pneumococcal conjugate vaccines (PCV) were as follows: 15B, 22F, 15A, 23A among children under the age of 7 y with IPD; among adults with IPD: 22F, 11A, 10A, 38 in the 65 y and older age group; 12F, 9N, 8 in the 50-64 year-old age group and 12F, 8, 6C, 16F in the 15-59 age group. Geographic variations in serotype distribution highlight the importance of monitoring evolving pneumococcal serotype prevalence after pneumococcal vaccine implementation.

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.

Rise of multidrug-resistant non-vaccine serotype 15A Streptococcus pneumoniae in the United Kingdom, 2001 to 2014

Conjugate vaccines have reduced pneumococcal disease in vaccinated children and unvaccinated adults, but non-vaccine serotypes are of concern, particularly if antibiotic resistant. We reviewed Streptococcus pneumoniae collected via: (i) the British Society for Antimicrobial Chemotherapy (BSAC) surveillances from 2001-2014; (ii) Public Health England's (PHE) invasive isolate surveillance from 2005-2014 and (iii) referral to PHE for resistance investigation from 2005-2014. Serotype 15A increased in all series, with many representatives showing triple resistance to macrolides, tetracyclines and penicillin. 15A was consistently among the 10 most prevalent serotypes from 2011 in PHE and BSAC invasive isolate/bacteraemia surveillance but never previously; 26-33% of these invasive 15A isolates had triple resistance. BSAC respiratory isolates were only serotyped in 2013/14 and 2014/15 (October to September); 15A was most prevalent serotype in both periods, comprising 9-11% of isolates, 38-48% of them with triple resistance. Serotype 15A represented 0-4% of S. pneumoniae referred to PHE for reference investigation annually until 2008 but rose to 29% (2013) and 32% (2014). Almost all multidrug-resistant 15A isolates were sequence type (ST) 63 variants, whereas susceptible 15A isolates were clonally diverse. The rise of serotype 15A suggests that pneumococcal conjugate vaccines will need ongoing adaptation.

Nasopharyngeal pneumococcal carriage rates among HIV-infected adults following widespread pediatric use of conjugate pneumococcal vaccine-13

BACKGROUND

Nasopharyngeal pneumococcal carriage rates among HIV-infected adults has not been described since conjugate pneumococcal vaccine-13 (PCV13) was added to the universal infant and childhood vaccination schedule in 2010.

METHODS

HIV-infected adults presenting for routine health care visits to the Designated AIDS Center in Syracuse, NY between December 2013 and June 2015 were eligible for enrollment. Demographic, medical, and social history were recorded after obtaining informed consent. Nasopharyngeal samples were collected and cultured for the presence of Streptococcus pneumoniae using standard microbiologic techniques. Antibiotic susceptibility testing was performed using E-test→.

RESULTS

707 nasopharyngeal samples were collected from 414 HIV-infected adults. 18 samples were culture positive for S. pneumoniae; 1 (6%) isolate was of vaccine-type, 9 (50%) were non-vaccine types, and 8 (44%) were non-typeable. The 18 isolates were recovered from 15 different patients (4% of those enrolled). Three patients were culture positive for pneumococcus isolated from 2 consecutive samples, with non-typeable pneumococci identified consecutively from 2 patients and serotype 35B identified consecutively from 1 patient. The most commonly identified non-vaccine serotypes were 35B and 15B/C. Identified pneumococci were penicillin and cefotaxime susceptible.

CONCLUSION

Four percent of HIV-infected adults in our study population were colonized with S. pneumoniae. The non-vaccine serotypes 35B and 15B/C predominated.