Willem R. Miellet (Netherlands)
University Medical Centre Utrecht
Department of Paediatric Immunology and Infectious Diseases
I'm a PhD student working in the lab of Krzysztof Trzcinski on bacterial carriage of vaccine-targeted respiratory bacterial pathogens, with a special interest in pneumococcal carriage. I have a background in biomedical sciences, in particular microbiology & immunology. One of the main goals of my PhD project is evaluating and validating molecular diagnostic methods, in particular qPCR, for molecular surveillance of pneumococcal carriage and pneumococcal serotyping. We evaluate these methods across all age groups and on polymicrobial respiratory samples such as saliva and oropharyngeal swab samples (see also: Miellet et al., FiM 2022; 10.3389/fmicb.2022.859736). Other subjects of my PhD project are pneumococcal carriage in older adults, and the interplay between respiratory viruses, the human host and pneumococcal carriage (see also: Miellet et al., CID 2020; 10.1093/cid/ciaa1551).

Presenter of 1 Presentation

 Conference Calendar

O057 - IT TAKES TWO TO TANGO: COMBINING CONVENTIONAL CULTURE WITH MOLECULAR DIAGNOSTICS ENHANCES ACCURACY OF STREPTOCOCCUS PNEUMONIAE DETECTION IN CARRIAGE (ID 588)

Session Name
0550 - Parallel Session 08: Diagnosis of Pneumococcal Disease (ID 48)
Session Type
Parallel Session
Date
Tue, 21.06.2022
Session Time
14:50 - 16:20
Room
Birchwood Ballroom
Presenter
Lecture Time
15:55 - 16:05

Abstract

Background

The accuracy of molecular methods for the detection of Streptococcus pneumoniae carriage in vaccine impact studies is under debate. We propose a procedure for carriage surveillance studies that enhances the specificity of molecular methods and the sensitivity of culture.

Methods

Culture and qPCR methods were applied to nasopharyngeal samples collected in the Netherlands (n=972) and England (n=577) from 946 toddlers and 603 adults, and in paired oropharyngeal samples exclusively from 319 Dutch adults. Detection by qPCR was performed on culture-enriched samples using a dual-target approach with piaB and lytA. Samples with no live pneumococci isolated at primary culture yet generating signal for pneumococcus in qPCRs were re-examined with a qPCR-guided culture. Cq cut-offs for positivity in qPCRs were determined via receiver operating characteristic curve analysis using isolation of live pneumococci as reference.isppd_methodology_figure.png

Results

Implementation of qPCR-guided culturing significantly increased the proportion of nasopharyngeal and oropharyngeal samples from which live pneumococcus was recovered (p<0.0001). Detection of pneumococcus with qPCRs in n=1549 culture-enriched nasopharyngeal samples exhibited near-perfect agreement with conventional culture (κ: 0.95). For paired nasopharyngeal and oropharyngeal samples from n=319 adults, none of the methods applied to a single sample type exhibited good agreement with combined results for primary+qPCR-guided nasopharyngeal and oropharyngeal cultures (κ; 0.13 to 0.55). However, primary+qPCR-guided cultures and qPCRs on culture-enriched samples displayed increased sensitivity of oropharyngeal compared with nasopharyngeal samples (p<0.05).

Conclusions

The accuracy of pneumococcal carriage surveillance can be greatly improved by complementing conventional culture with qPCR and by using results of qPCR-guided cultures to interpret qPCR data.

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