Increased in vitro fitness of multi- and extensively drug-resistant F15/LAM4/KZN strains of Mycobacterium tuberculosis
Clinical Microbiology and Infection·
- DOI
- 10.1111/1469-0691.12415
- PMID
- 24118525
- PMCID
- —
- OpenAlex
- W1922810686
- Study type
- Journal article
- Publisher
- Elsevier BV
- Article type
- journal-article
- Integrity
- current
Why this research matters now
The findings suggest that successful transmission of F15/LAM4/KZN strains during the Tugela Ferry outbreak may be explained by drug-resistance mutations that impose little or no fitness cost. The persistence of viable drug-resistant strains at low concentrations in mixed populations could support acquisition of additional resistance mutations or evolution of compensatory mechanisms, with implications for MDR and XDR-TB control strategies.
Structured evidence summary
Research question
The study examined the in vitro biological fitness of F15/LAM4/KZN strains of Mycobacterium tuberculosis, which caused an extensively drug-resistant tuberculosis outbreak in Tugela Ferry, South Africa, to understand their transmission success.
Study design
Laboratory-based fitness assessment of 15 clinical M. tuberculosis strains representing F15/LAM4/KZN, Beijing, F11, and F28 families using growth assays, viability assays, and competition experiments. DNA sequencing of eight genes associated with drug resistance and compensatory mechanisms was performed to correlate genetic features with fitness profiles.
Population and setting
Clinical strains isolated from patients in South Africa, including strains from the Tugela Ferry XDR-TB outbreak. The study was conducted in vitro using laboratory culture systems.
Main findings
F15/LAM4/KZN and F28 drug-resistant strains showed similar growth rates to susceptible strains, while Beijing and F11 MDR strains demonstrated significantly reduced fitness. All 14 drug-resistant strains retained viability at low concentrations when paired with susceptible strains in co-culture. KZN and F28 resistant strains carried frequently occurring mutations, whereas Beijing MDR strains had a less common katG mutation and F11 MDR strains lacked katG mutations entirely.
Public-health relevance
The findings suggest that successful transmission of F15/LAM4/KZN strains during the Tugela Ferry outbreak may be explained by drug-resistance mutations that impose little or no fitness cost. The persistence of viable drug-resistant strains at low concentrations in mixed populations could support acquisition of additional resistance mutations or evolution of compensatory mechanisms, with implications for MDR and XDR-TB control strategies.
Important limitations
This summary is based solely on the supplied single-article abstract and metadata. Full interpretation of methods, statistical analyses, strain selection criteria, and generalizability requires the complete published article.
GIDS interpretation
This article was classified under Tuberculosis, South Africa, Antimicrobial resistance, Outbreak investigation, and Transmission dynamics. The paper provides mechanistic insight into fitness characteristics of outbreak-associated XDR-TB strains but does not constitute real-time surveillance data or represent current disease activity.
Related GIDS surveillance
Literature context does not validate, explain, or change a surveillance signal. Exact and contextual relationships are shown separately.
Evidence relationships
This article has 8 auditable classifier relationships to diseases, places, topics, and study design.