Evaluation of Pneumococcal Serotyping of Nasopharyngeal-Carriage Isolates by Latex Agglutination, Whole-Genome Sequencing (PneumoCaT), and DNA Microarray in a High-Pneumococcal-Carriage-Prevalence Population in Malawi

Swarthout, TD; Gori, A; Bar-Zeev, N; Kamng'ona, AW; Mwalukomo, TS; Bonomali, F; Nyirenda, R; Brown, C; Msefula, J; Everett, D; Mwansambo, C; Gould, K; Hinds, J; Heyderman, RS; French, N

Abstract

Accurate assessment of the serotype distribution associated with pneumococcal colonization and disease is essential for evaluating and formulating pneumococcal vaccines and for informing vaccine policy. For this reason, we evaluated the concordance between pneumococcal serotyping results by latex agglutination, whole-genome sequencing (WGS) with PneumoCaT, and DNA microarray for samples from community carriage surveillance in Blantyre, Malawi. Nasopharyngeal swabs were collected according to WHO recommendations between 2015 and 2017 by using stratified random sampling among study populations. Participants included healthy children 3 to 6 years old (vaccinated with the 13-valent pneumococcal conjugate vaccine [PCV13] as part of the Expanded Program on Immunization [EPI]), healthy children 5 to 10 years old (age-ineligible for PCV13), and HIV-infected adults (18 to 40 years old) on antiretroviral therapy (ART). For phenotypic serotyping, we used a 13-valent latex kit (Statens Serum Institut [SSI], Denmark). For genomic serotyping, we applied the PneumoCaT pipeline to whole-genome sequence libraries. For molecular serotyping by microarray, we used the BUGS Bioscience Senti-SP microarray. A total of 1,347 samples were analyzed. Concordance was 90.7% (95% confidence interval [Cl], 89.0 to 92.2%) between latex agglutination and PneumoCaT, 95.2% (95% CI, 93.9 to 96.3%) between latex agglutination and the microarray, and 96.6% (95% CI, 95.5 to 97.5%) between the microarray and PneumoCaT. By detecting additional vaccine serotype (VT) pneumococci carried at low relative abundances (median, 8%), the microarray increased VT detection by 31.5% over that by latex serotyping. To conclude, all three serotyping methods were highly concordant in identifying dominant serotypes. Latex serotyping is accurate in identifying vaccine serotypes and requires the least expertise and resources for field implementation and anal ysis. However, WGS, which adds population structure, and microarray, which adds multiple-serotype carriage, should be considered at regional reference laboratories for investigating the importance of vaccine serotypes at low relative abundances in transmission and disease.

Citation

Swarthout, T., Gori, A., Bar-Zeev, N., Kamng'ona, A., Mwalukomo, T., Bonomali, F., …French, N. (2021). Evaluation of Pneumococcal Serotyping of Nasopharyngeal-Carriage Isolates by Latex Agglutination, Whole-Genome Sequencing (PneumoCaT), and DNA Microarray in a High-Pneumococcal-Carriage-Prevalence Population in Malawi. Journal of Clinical Microbiology, 59(1), https://doi.org/10.1128/JCM.02103-20

• Journal Article Type: Article
• Acceptance Date: Dec 16, 2020
• Online Publication Date: Dec 17, 2020
• Publication Date: 2021
• Deposit Date: Jan 11, 2022
• Publicly Available Date: Jan 11, 2022
• Print ISSN: 0095-1137
• Publisher: American Society for Microbiology
• Peer Reviewed: Peer Reviewed
• Volume: 59
• Issue: 1
• DOI: https://doi.org/10.1128/JCM.02103-20
• Keywords: Streptococcus pneumoniae; serotyping; latex agglutination; microarray; whole-genome sequencing; methodology; Africa; UPPER RESPIRATORY CARRIAGE; STREPTOCOCCUS-PNEUMONIAE; STANDARD METHOD; DISEASE; CHILDREN; ERA
• Public URL: https://rvc-repository.worktribe.com/output/1554902