Upper respiratory tract colonization with Streptococcus pneumoniae in adults

ABSTRACT

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.

KEYWORDS:

• Adults
• carriage
• colonization
• pneumococcal
• Streptococcus pneumoniae
• upper respiratory tract

Article highlights

• Most of the evidence on pneumococcal upper respiratory tract carriage, associated implications, transmission, and dynamics following vaccination with pneumococcal vaccines have been obtained from studies performed in children.

• In spite of the bimodal incidence of pneumococcal infections with peaks in children under 5 years and adults 65 years and older, conventional nasopharyngeal carriage studies in ≥65-year- old adults have found low pneumococcal respiratory carriage (0%–6%).

• Most carriage studies performed in adults have followed the pediatric approach in which a single swab from the nasopharynx, sometimes obtained together with an oropharyngeal sample, was collected and processed following standard culture recommendations.

• Contemporary studies suggest that pneumococcal detection in the respiratory tract of adults has been underestimated and that pneumococcal detection in this age group is enhanced in longitudinal studies that obtain samples from various respiratory sites, such as nasal washes, oropharynx, and saliva and by the use of culture enrichment and quantitative PCR targeting two pneumococcal DNA sequences.

• Given the importance of understanding the dynamics of pneumococcal carriage in adults and the effect of pneumococcal conjugate vaccines on respiratory carriage, future studies in adults should implement additional molecular techniques to measure pneumococcal carriage in adults and the potential of adult-to-adult or adult-to-children pneumococcal transmission.

Author contributions

All authors were involved in the preparation, creation, and/or editing of the manuscript, including critical review, commentary, or revision.

Declaration of interest

A Arguedas, B D Gessner, R Isturiz, L Jodar, and J Suaya are employees of Pfizer Inc and may hold stock or stock options. M-C C Brandileone has received lecture fees from Pfizer, GlaxoSmithKline, and Merck Sharp & Dohme, and travel grants from Pfizer and GlaxoSmithKline. L L Hammitt and K L O’Brien report research grants to their respective institutions from Pfizer, GlaxoSmithKline, and Merck. K L O’Brien has served as an external expert to GlaxoSmithKline and Sanofi Pasteur on pneumococcal vaccine development. D M Ferreira has received consulting fees and grant support for studies on pneumococcal carriage from Pfizer. K Trzciński has received consultation and speaking fees and funds for unrestricted research grants from Pfizer, funds for unrestricted research grants from GlaxoSmithKline, and consultation fees from Merck Sharp & Dohme, all paid directly to his home institution. R Sá-Leão has received consulting and speaking fees from Pfizer and consulting fees from Merck Sharp & Dohme, and received funds for unrestricted research grants from Pfizer, paid directly to her institution. D Weinberger has received consulting fees from Pfizer, GlaxoSmithKline, and Affinivax for work outside the current manuscript. L Danon has received consulting fees and funds for investigator-led research from Pfizer for work outside of the current manuscript. S I Pelton has research grants through Boston Medical Center for investigator-initiated research from Pfizer Inc and Merck Vaccines; he has also received support from Pfizer Inc, Merck Vaccines, and Sanofi Pasteur for participation in advisory boards on vaccines and for participation in symposiums. C Azzari has received research grants, payment for consultancy and for speaking at meetings by Pfizer. A L Wyllie is Principal Investigator on a research grant from Pfizer to Yale University and has received consulting fees for participation in advisory boards for Pfizer. S Saha has received funding from Pfizer, GlaxoSmithKline, and Sanofi Pasteur for pneumococcal diseases and carriage. Editorial support was utilized in the production of this manuscript, provided by Tricia Newell, PhD, and Anna Stern, PhD, of Complete Healthcare Communications, LLC (North Wales, PA), and was funded by Pfizer Inc. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

A reviewer on the manuscript has declared that they are a Principle Investigator of the Vice study, an investigator initiated study on the effects of PCV10 on children in Iceland, which was supported by GlaxoSmithKline. No other reviewers have relevant financial or other relationships to disclose.

Additional information

Funding

This study was funded by Pfizer Inc.