Rasheed Salaudeen, Gambia

Medical Research Council Unit The Gambia at LSHTM Research Microbiology Basse

Author Of 3 Presentations

NASOPHARYNGEAL PNEUMOCOCCAL SEROTYPE DETECTION COMBINING LATEX AGGLUTINATION SWEEP SEROTYPING WITH QUELLUNG IN THE GAMBIA. (ID 714)

Abstract

Background

Detection of multiple pneumococcal serotypes in nasopharyngeal swabs (NPS) by latex agglutination, either by the WHO protocol or sweep serotyping may yield incomplete serum factor reactions. We investigated the impact of combining latex sweep serotyping with Quellung to improve the specificity of reactions while detecting multiple pneumococcal serotypes.

Methods

We randomly selected 103 STGG-NPS samples cultured and serotyped by latex agglutination of different morphological colonies (WHO protocol) in two cross-sectional carriage studies. We performed Quellung capsular serotyping on 1, 2 or 3 morphologically distinct pneumococcal colonies from the culture plates and then swept the same plates.

Results

Sweep serotyping was more likely to detect multiple serotypes (Table 1) than the WHO protocol (p=0.004). A common serotype was identified in 95/103 (92.2%) NPS samples by the WHO, latex sweep and Quellung. Quellung gave more conclusive antisera reactions (Table 2) than the WHO protocol (p=0.007). No significant difference in conclusiveness of antisera reaction between Quellung and latex sweep (p=0.119).real.png

Conclusions

Combining sweep serotyping and Quellung is a cost-effective way of detecting multiple pneumococcal serotype co-colonization and resolving issues related to antisera reactivity in latex agglutination. Inconclusive Quellung results occurred because we detected more serotypes by latex sweep than were selected according to different morphological colonies.

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