Sociological variety and the transmission efficiency of Mycobacterium tuberculosis: a secondary analysis of qualitative and quantitative data from 15 communities in Zambia.

OBJECTIVES: Selected Zambian communities formed part of a cluster randomised trial: the Zambia and South Africa TB and AIDS Reduction study (ZAMSTAR). There was wide variability in the prevalence of Mycobacterium tuberculosis infection and tuberculosis (TB) disease across these communities. We sought to clarify whether specific communities could have been more/less vulnerable to M. tuberculosis transmission as a result of sociological variety relevant to transmission efficiency. DESIGN: We conducted a mixed methods secondary analysis using existing data sets. First, we analysed qualitative data to categorise and synthesise patterns of socio-spatial engagement across communities. Second, we compared emergent sociological variables with a measure of transmission efficiency: the ratio of the annual risk of infection to TB prevalence. SETTING: ZAMSTAR communities in urban and peri-urban Zambia, spanning five provinces. PARTICIPANTS: Fifteen communities, each served by a health facility offering TB treatment to a population of at least 25 000. TB notification rates were at least 400 per 100 000 per annum and HIV seroprevalence was estimated to be high. RESULTS: Crowding, movement, livelihoods and participation in recreational activity differed across communities. Based on 12 socio-spatial indicators, communities were qualitatively classified as more/less spatially crowded and as more/less socially 'open' to contact with others, with implications for the presumptive risk of M. tuberculosis transmission. For example, watching video shows in poorly ventilated structures posed a presumptive risk in more socially open communities, while outdoor farming and/or fishing were particularly widespread in communities with lower transmission measures. CONCLUSIONS: A dual dynamic of 'social permeability' and crowding appeared relevant to disparities in M. tuberculosis transmission efficiency. To reduce transmission, certain socio-spatial aspects could be adjusted (eg, increasing ventilation on transport), while more structural aspects are less malleable (eg, reliance on public transport). We recommend integrating community level typologies with genome sequencing techniques to further explore the significance of 'social permeability'. TRIAL REGISTRATION NUMBER: ISRCTN36729271.

High levels of vulnerability and anticipated stigma reduce the impetus for tuberculosis diagnosis in Cape Town, South Africa.

Prolonged diagnostic and treatment delays, particularly in settings experiencing concomitant human immunodeficiency virus (HIV) and tuberculosis (TB) epidemics, undermine global TB control efforts. Current TB control policy in South Africa, as organized through the National TB Control Programme (NTP), relies on the voluntary presentation of TB suspects to local clinics for diagnosis, i.e. passive case finding (PCF). In 2005 a participatory study suggested that popular interpretation and perception of TB within eight South African township sites in and around Cape Town, all carrying a high burden of HIV and undiagnosed TB, undermine PCF. Both people's association of TB with dirt and squalor, and the anticipation of HIV-related stigma, combine to impede TB diagnosis. Respondents conveyed TB as unavoidable; this perception is expressed in the context of vulnerability where so much-including dirt-is largely beyond the control of local residents. The lack of control has a disempowering effect, reducing the drive for seeking treatment. In addition, low confidence in patient confidentiality and anticipated HIV-related stigma act as direct deterrents to TB diagnosis and treatment. In conclusion, we wish to draw attention to high levels of disease stigma and vulnerability, and how these undermine PCF. Public health interventions that wish to improve case detection should aim to: (1) emphasize how early treatment improves outcome and can curb ongoing transmission; (2) combat a sense of communal vulnerability to TB; (3) address anticipated HIV-TB stigma; and (4) improve the quality of care provided at local diagnostic services, addressing low levels of patient confidentiality.

Reinfection and mixed infection cause changing Mycobacterium tuberculosis drug-resistance patterns.

RATIONALE: Multiple infections with different strains of Mycobacterium tuberculosis may occur in settings where the infection pressure is high. The relevance of mixed infections for the patient, clinician, and control program remains unclear. OBJECTIVES: This study aimed to describe reinfection and mixed infection as underlying mechanisms of changing drug-susceptibility patterns in serial sputum cultures. METHODS: Serial M. tuberculosis sputum cultures from patients diagnosed with multi-drug-resistant (MDR) tuberculosis were evaluated by phenotypic drug-susceptibility testing and mutation detection methods. Genotypic analysis was done by IS6110 DNA fingerprinting and a novel strain-specific polymerase chain reaction amplification method. MEASUREMENTS AND MAIN RESULTS: DNA fingerprinting analysis of serial sputum cultures from 48 patients with MDR tuberculosis attributed 10 cases to reinfection and 1 case to mixed infection. In contrast, strain-specific polymerase chain reaction amplification analysis in 9 of the 11 cases demonstrated mixed infection in 5 cases, reinfection in 3 cases, and laboratory contamination in 1 case. Analysis of clinical data suggests that first-line therapy can select for a resistant subpopulation, whereas poor adherence or second-line therapy resulted in the reemergence of the drug-susceptible subpopulations. CONCLUSIONS: We have shown that, in some patients with MDR tuberculosis, mixed infection may be responsible for observations attributed to reinfection by DNA fingerprinting. We conclude that treatment and adherence determines which strain is dominant. We hypothesize that treatment with second-line drugs may lead to reemergence of the drug-susceptible strain in patients with mixed infection.