Molecular detection of mixed infections of Mycobacterium tuberculosis in sputum samples from patients in Karonga District, Malawi.


Mallard, K; McNerney, R; Crampin, AC; Houben, R; Ndlovu, R; Munthali, L; Warren, RM; French, N; Glynn, JR; (2010) Molecular detection of mixed infections of Mycobacterium tuberculosis in sputum samples from patients in Karonga District, Malawi. Journal of clinical microbiology, 48 (12). pp. 4512-8. ISSN 0095-1137 DOI: https://doi.org/10.1128/JCM.01683-10

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Abstract

: The occurrence of mixed infections of Mycobacterium tuberculosis is no longer disputed. However, their frequency, and the impact they may have on our understanding of tuberculosis (TB) pathogenesis and epidemiology, remains undetermined. Most previous studies of frequency applied genotyping techniques to cultured M. tuberculosis isolates and found mixed infections to be rare. PCR-based techniques may be more sensitive for detecting multiple M. tuberculosis strains and can be applied to sputum. To date, one study in South Africa has used a PCR approach and suggested that mixed infection could be common. We investigated mixed infections in northern Malawi using two lineage-specific PCR assays targeting the Latin American-Mediterranean (LAM) and Beijing lineages. Compared with spoligotyping, the specificity and sensitivity of both assays was 100%. From 160 culture-positive sputa, mixed LAM and non-LAM strains were detected in 4 sputa belonging to 2 (2.8%) patients. Both patients were HIV positive, with no history of TB. Cultured isolates from both patients showed only LAM by PCR and spoligotyping. In a set of 377 cultured isolates, 4 were mixed LAM and non-LAM. Only one showed evidence of more than one M. tuberculosis strain using IS6110-based restriction fragment length polymorphism (IS6110-RFLP) and spoligotyping analyses. Corresponding sputa for the 4 isolates were unavailable. Mixed Beijing and non-Beijing strains were not detected in this study. Mixed infections appear to be rare in our setting and are unlikely to affect findings based on DNA fingerprinting data. Molecular methods, which avoid the selective nature of culture and target distinct strains, are well suited to detection of mixed infections.<br/>

Item Type: Article
Faculty and Department: Faculty of Infectious and Tropical Diseases > Dept of Clinical Research
Faculty of Epidemiology and Population Health > Dept of Infectious Disease Epidemiology
Faculty of Infectious and Tropical Diseases > Dept of Pathogen Molecular Biology
Research Centre: TB Centre
MEIRU
PubMed ID: 20962138
Web of Science ID: 284693400026
URI: http://researchonline.lshtm.ac.uk/id/eprint/2494

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