Disseminated bacille Calmette-Guérin disease in HIV-infected South African infants

OBJECTIVE

To determine the population-based incidence of disseminated bacille Calmette-Guérin (BCG) disease in HIV-infected infants (aged <or= 1 year) in a setting with a high burden of tuberculosis and HIV infection coupled with a well-functioning programme for the prevention of HIV infection in infants.

METHODS

The numerator, or number of new cases of disseminated BCG disease, was derived from multicentre surveillance data collected prospectively on infants with a confirmed HIV infection during 2004-2006. The denominator, or total number of HIV-infected infants who were BCG-vaccinated, was derived from population-based estimates of the number of live infants and from reported maternal HIV infection prevalence, vertical HIV transmission rates and BCG vaccination rates.

FINDINGS

The estimated incidences of disseminated BCG disease per 100 000 BCG-vaccinated, HIV-infected infants were as follows: 778 (95% confidence interval, CI: 361-1319) in 2004 (vertical HIV transmission rate: 10.4%); 1300 (95% CI: 587-2290) in 2005 (transmission rate: 6.1%); and 1013 (95% CI: 377-1895) in 2006 (transmission rate: 5.4%). The pooled incidence over the study period was 992 (95% CI: 567-1495) per 100 000.

CONCLUSION

Multicentre surveillance data showed that the risk of disseminated BCG disease in HIV-infected infants is considerably higher than previously estimated, although likely to be under-estimated. There is an urgent need for data on the risk-benefit ratio of BCG vaccination in HIV-infected infants to inform decision-making in settings where HIV infection and tuberculosis burdens are high. Safe and effective tuberculosis prevention strategies are needed for HIV-infected infants.

A multidisciplinary method to map potential tuberculosis transmission 'hot spots' in high-burden communities

BACKGROUND

Global control of the tuberculosis (TB) epidemic remains poor, especially in high-burden settings where ongoing transmission sustains the epidemic. In such settings, a significant amount of transmission takes place outside the household, and practical approaches to understanding transmission at community level are needed.

OBJECTIVE

To identify and map potential TB transmission 'hot spots' across high-burden communities.

SETTING AND DESIGN

Our method draws on data that qualitatively describe a high-burden community in Cape Town, South Africa. Established transmission principles are applied to grade the potential TB transmission risk posed by congregate settings in the community. Geographic information systems (GIS) technology then creates a visual map, locating potential transmission 'hot spots' in the community.

RESULTS

Drinking places (shebeens), clinics and churches (often gatherings in confined homes) emerge as gathering places that potentially pose a high transmission risk, particularly if located in overcrowded and impoverished areas of the community.

CONCLUSION

This proof-of-concept study demonstrates that combining qualitative techniques with GIS mapping may improve our understanding of potential TB transmission within a community and guide public health interventions to enhance TB control efforts.

Comparison of four culture systems for Mycobacterium tuberculosis in the Zambian National Reference Laboratory

SETTING

National TB Reference Laboratory, Zambia.

OBJECTIVE

To compare four TB culture systems when used in a resource-limited setting.

DESIGN

Comparison of four culture systems: automated Mycobacterium Growth Indicator Tube (AMGIT) 960, manual MGIT (MMGIT) and two Löwenstein-Jensen (LJ) culture media-commercial (CLJ) and homemade (HLJ).

RESULTS

A total of 1916 sputum specimens were received, of which 261 (13.6%) were positive on microscopy. Mycobacterium tuberculosis complex (MTC) was isolated on at least one of the media in 410 (21.4%) specimens: MMGIT recovered 336 (17.5%) MTC, AMGIT 329 (17.2%), CLJ 192 (10.0%) and HLJ 184 (9.6%). The median time to detection for smear-negative specimens was 14 days for AMGIT, 16 days for MMGIT and 34 days for both LJ. Isolation of non-tuberculous mycobacteria (NTM) was more frequent in both MGIT systems (3.5%) than in CLJ (0.9%) and HLJ (0.8%). Contamination rates were high: 29.6% on AMGIT, 23.8% on MMGIT, 14.9% on CLJ and 12.5% on HLJ.

CONCLUSION

Despite high contamination rates, either MGIT system considerably improved both the yield and the time to detection of MTC compared to LJ media. Investments in infrastructure and training are needed if culture is to be scaled up in low-income settings such as this.

High incidence of tuberculosis among HIV-infected infants: evidence from a South African population-based study highlights the need for improved tuberculosis control strategies

BACKGROUND

There are limited population-based estimates of tuberculosis incidence among human immunodeficiency virus (HIV)-infected and HIV-uninfected infants aged < or =12 months. We aimed to estimate the population-based incidence of culture-confirmed tuberculosis among HIV-infected and HIV-uninfected infants in the Western Cape Province, South Africa.

METHODS

The incidences of pulmonary, extrapulmonary, and disseminated tuberculosis were estimated over a 3-year period (2004-2006) with use of prospective representative hospital surveillance data of the annual number of culture-confirmed tuberculosis cases among infants. The total number of HIV-infected and HIV-uninfected infants was calculated using population-based estimates of the total number of live infants and the annual maternal HIV prevalence and vertical HIV transmission rates.

RESULTS

There were 245 infants with culture-confirmed tuberculosis. The overall incidences of tuberculosis were 1596 cases per 100,000 population among HIV-infected infants (95% confidence interval [CI], 1151-2132 cases per 100,000 population) and 65.9 cases per 100,000 population among HIV-uninfected infants (95% CI, 56-75 cases per 100,000 population). The relative risk of culture-confirmed tuberculosis among HIV-infected infants was 24.2 (95% CI, 17-34). The incidences of disseminated tuberculosis were 240.9 cases per 100,000 population (95% CI, 89-433 cases per 100,000 population) among HIV-infected infants and 14.1 cases per 100,000 population (95% CI, 10-18 cases per 100,000 population) among HIV-uninfected infants (relative risk, 17.1; 95% CI, 6-34).

CONCLUSIONS

This study indicates the magnitude of the tuberculosis disease burden among HIV-infected infants and provides population-based comparative incidence rates of tuberculosis among HIV-infected infants. This high risk of tuberculosis among HIV-infected infants is of great concern and may be attributable to an increased risk of tuberculosis exposure, increased immune-mediated tuberculosis susceptibility, and/or possible limited protective effect of bacille Calmette-Guérin vaccination. Improved tuberculosis control strategies, including maternal tuberculosis screening, contact tracing of tuberculosis-exposed infants coupled with preventive chemotherapy, and effective vaccine strategies, are needed for infants in settings where HIV infection and tuberculosis are highly endemic.

Costs and cost-effectiveness of tuberculosis cultures using solid and liquid media in a developing country

SETTING

The expansion of culture has been proposed to aid tuberculosis (TB) control in developing countries.

OBJECTIVES

To examine the cost and cost-effectiveness at the Zambian National TB Reference Laboratory of homemade and commercially produced Löwenstein-Jensen culture (HLJ and CLJ) as well as automated and manually read liquid culture (AMGIT and MMGIT).

DESIGN

Costs were estimated from the provider's perspective and based on the average monthly throughput. Cost-effectiveness estimates were based on yield during the study period.

RESULTS

All techniques show comparable costs per culture (between US$28 and $32). Costs per Mycobacterium tuberculosis specimen detected were respectively US$197, $202, $312 and $340 for MMGIT, AMGIT, CLJ and HLJ. When modelled for the maximum throughput, costs were above US$95 per M. tuberculosis specimen detected for all techniques. When only performed among smear-negative specimens, costs per additionally identified M. tuberculosis would be US$487 for MMGIT and higher for other methods.

CONCLUSION

Based on cost-effectiveness grounds, liquid media compare well with conventional solid media, especially where yield of MGIT is substantially higher than that of LJ media. The results indicate high overall costs per culture; the expansion of culture to decentralised levels with lower throughputs may result in even higher costs.

Cost of tuberculosis diagnosis and treatment from the patient perspective in Lusaka, Zambia

SETTING

Urban primary health centres in Lusaka, Zambia.

OBJECTIVES

1) To estimate patient costs for tuberculosis (TB) diagnosis and treatment and 2) to identify determinants of patient costs.

METHODS

A cross-sectional survey of 103 adult TB patients who had been on treatment for 1-3 months was conducted using a standardised questionnaire. Direct and indirect costs were estimated, converted into US$ and categorised into two time periods: 'pre-diagnosis/care-seeking' and 'post-diagnosis/treatment'. Determinants of patient costs were analysed using multiple linear regression.

RESULTS

The median total patient costs for diagnosis and 2 months of treatment was $24.78 (interquartile range 13.56-40.30) per patient--equivalent to 47.8% of patients' median monthly income. Sex, patient delays in seeking care and method of treatment supervision were significant predictors of total patient costs. The total direct costs as a proportion of income were higher for women than men (P < 0.001). Treatment costs incurred by patients on the clinic-based directly observed treatment strategy were more than three times greater than those incurred by patients on the self-administered treatment strategy (P < 0.001).

CONCLUSION

Clinic-based treatment supervision posed a significant economic burden on patients. The creation or strengthening of community-based treatment supervision programmes would have the greatest potential impact on reducing patients' TB-related costs.

'Kuyendela odwala TB'--visiting TB patients: the widening role of home-based care organisations in the management of tuberculosis patients in Lusaka, Zambia

OBJECTIVE

To explore the widening role of home-based care (HBC) organisations in the management of TB patients in Lusaka, Zambia, in 1999.

DESIGN

In a purposeful sample of eight HBC organisations and 1 hospice in Lusaka, 142 TB patients under HBC, 54 care givers, 42 TB patients not under HBC and 9 managers were interviewed.

RESULTS

At least 50% of TB patients in Lusaka are cared for by HBC. The role of HBC in management of TB patients included food aid, practical and emotional support through the visits of voluntary care givers and, often, medical advice and treatment. TB diagnosis is carried out within the government health facilities. Five HBC organisations supplied anti-tuberculosis drugs, and three tried to carry out direct observation of treatment. The majority of the TB patients said their situation improved under HBC. Management was undermined by poor record keeping, sporadic anti-tuberculosis drug supplies, stigmatising preventive messages, limited supervision of care givers and poor coordination with the District Health Services.

CONCLUSION

HBC organisations have become a key partner in TB control, looking after half the TB patients in Lusaka from diagnosis onwards, and complementing the public system. However, the quality of their management of TB and their partnership with government need to improve.

Comparison of two bacteriophage tests and nucleic acid amplification for the diagnosis of pulmonary tuberculosis in sub-Saharan Africa

SETTING

National reference laboratory in Zambia, a high-incidence setting with a high prevalence of HIV infection.

OBJECTIVE

To compare the performance of a commercial bacteriophage kit with a nucleic acid amplification kit and an 'in-house' bacteriophage method for rapid diagnosis of pulmonary tuberculosis (TB).

METHODS

Sputum specimens from suspected pulmonary TB cases were examined by direct fluorescence microscopy and culture on Löwenstein Jensen (LJ). In a blinded study, remaining samples were tested by AMTD and FASTPlaqueTB or an in-house bacteriophage assay. Two specimen decontamination protocols were investigated.

RESULTS

Microbial contamination of 40.4% was observed when using the FASTPlaqueTB kit specimen preparation protocol. When compared to culture on LJ, the sensitivity of the FASTPlaqueTB test was 20.7%. Implementation of a modified Petroff's decontamination protocol reduced contamination to 5.8% and the FASTPlaqueTB test detected 8/25 (32%) of culture-positive specimens. The sensitivity of AMTD and smear microscopy for these specimens were 64% and 48%, respectively. In a separate experiment the sensitivity of an in-house bacteriophage assay was 45.3% compared to 64.2% for AMTD and 45.3% for direct smear microscopy.

CONCLUSIONS

Additional analysis of sputum specimens by bacteriophage assay provided no advantage in this setting. For the rapid diagnosis of TB, AMTD offered improved sensitivity over direct smear microscopy.

Auditing the new decentralised oral treatment regimens in Malawi

SETTING

All 44 non-private hospitals in Malawi treating tuberculosis (TB) cases in which oral regimens were used allowing patients during the initial phase to receive directly observed treatment (DOT) from health centres or guardians at home.

OBJECTIVES

A country-wide audit of the oral regimens to determine: 1) TB ward bed occupancy rates, 2) patient DOT options, 3) patients' knowledge of treatment and 4) treatment outcomes compared to those obtained with previous treatment regimens.

DESIGN

Retrospective data collection using registers and treatment cards. Prospective interviews with patients. Inspections of TB wards.

RESULTS

There were 1513 TB beds occupied by 807 (53%) TB patients. Over 50% of 4793 patients registered with different types of TB chose guardian-based DOT. For 266 patients with pulmonary TB the correct knowledge about total duration of treatment (45%), all three DOT options (62%) and the months for giving follow-up sputum (16%), was poor. There were differences in treatment outcomes between TB patients on oral compared with previous regimens. With oral regimens, rates of unknown outcome were high.

CONCLUSION

Oral treatment regimens are associated with reduced bed occupancy rates on TB wards. However, rates of unknown outcome are increased, and TB control is therefore weakened.

Using a bus service for transporting sputum specimens to the Central Reference Laboratory: effect on the routine TB culture service in Malawi

SETTING

All non-private hospitals in Malawi that registered TB cases in 2001, during which there was a bus service for transporting sputum specimens to the Central Reference Laboratory (CRL) for mycobacterial culture and drug sensitivity testing (CDST).

OBJECTIVES

To determine the performance of the system of collecting and processing sputum specimens from patients with recurrent smear-positive pulmonary TB through to CDST.

DESIGN

Structured interviews with TB Officers, and retrospective data collection using TB and laboratory registers.

RESULTS

There were 964 patients with recurrent smear-positive PTB. TB Officers took responsibility for collecting and transporting sputum to the CRL, and 73% reported using the bus service. Sputum specimens from 384 (40%) patients arrived at the CRL. Of these, 40% were found to have negative concentrated smears at the CRL, and 36% of specimen sets arriving at CRL were successfully cultured for DST. Most specimens had been collected after the start of anti-tuberculosis treatment. Although delays in collection adversely affected culture, only 43% of specimen sets collected on or before the first day of treatment yielded Mycobacterium tuberculosis.

CONCLUSION

Problems were identified at all stages of the system and strategies to remedy these are being put in place.

Management and outcome of tuberculosis patients who fail treatment under routine programme conditions in Malawi

SETTING

All 43 non-private hospitals (three central, 22 district and 18 mission) in Malawi that registered and treated TB cases between 1 July 1999 and 30 June 2000.

OBJECTIVES

To determine 1) the number of new smear-positive PTB patients who failed treatment, 2) the management of patients who failed, 3) their treatment outcome and 4) culture and drug sensitivity results.

DESIGN

Retrospective data collection using TB registers and laboratory culture and drug sensitivity registers.

RESULTS

Ninety patients failed treatment, 60 (67%) at 5 months and 30 (33%) at the end of treatment. Sixty-four (71%) failure patients were registered and commenced on anti-tuberculosis treatment. Of these, 95% were registered in the same hospital as before, 89% were given a different TB registration number, 67% were correctly registered as 'failures' and 61% were treated within one month of failing the previous regimen. Forty-eight (75%) re-treated patients were cured. Only 31 (34%) of the 90 patients had sputum sent for culture and drug sensitivity testing. In 11 patients with cultures of M. tuberculosis, eight were fully sensitive and three had mono-resistance to isoniazid.

CONCLUSION

While the outcome of failure patients who start retreatment is good, there are several programmatic deficiencies that need to be corrected.

Characteristics, management and outcome of patients with recurrent tuberculosis under routine programme conditions in Malawi

SETTING

All 43 non-private hospitals in Malawi, which registered TB cases between 1 July 1999 and 30 June 2000.

OBJECTIVES

To determine 1) the characteristics, management and treatment outcome, 2) timing of the previous episode of TB, and 3) pattern of drug resistance in patients registered with recurrent smear-positive pulmonary TB.

DESIGN

Retrospective data collection using TB registers and laboratory culture and drug sensitivity registers.

RESULTS

There were 748 recurrent patients; data were available for 747. Of these, 487 (65%) successfully completed a re-treatment regimen, 185 (25%) died and the remainder had another outcome. Information about previous TB was recorded for 491 (66%) patients. In 286 (58%) there were 2 years or less between completing and re-starting treatment. Only 307 (41%) patients had sputum sent for culture and drug sensitivity tests. In 164 patients with cultures of Mycobacterium tuberculosis, 122 (81%) were fully sensitive, 25 (15%) had resistance to isoniazid and/or streptomycin, and 6 (4%) had resistance to isoniazid and rifampicin (MDR-TB).

CONCLUSION

Patients with recurrent TB had acceptable treatment outcomes, and most had fully sensitive organisms. Over half had recurrent TB 2 years or less after completing treatment. Ways to prevent recurrence need to be investigated and implemented in the field.

Defining and assessing the maximum number of visits patients should make to a health facility to obtain a diagnosis of pulmonary tuberculosis

SETTING

All non-private hospitals in Malawi.

OBJECTIVES

To determine 1) how many patients with pulmonary tuberculosis (PTB) exceed the maximum number of visits needed for registration as defined by the National Tuberculosis Control Programme, and 2) the factors associated with this delay.

DESIGN

Cross-sectional study interviewing hospitalised patients with new smear-positive and smear-negative PTB.

RESULTS

Of 380 patients with PTB admitted to the 44 hospitals visited between April and June 2002, 329 (212 smear-positive and 117 smear-negative PTB) were interviewed: 64 (30%) smear-positive PTB patients needed more than five visits, and 44 (37%) smear-negative PTB patients needed more than six visits before being registered and started on treatment. Factors associated with exceeding the maximum number of visits were the first visit being to a health centre, submission of > 1 set of sputum specimens, and > 1 course of antibiotics. The main consequence of exceeding the maximum number of visits was increased duration of cough and increased time spent at health facilities.

CONCLUSION

One third of patients exceed the maximum number of visits for registration of PTB. The main consequence of this is an increased duration of cough and an increased time spent at health facilities. Ways to reduce this delay need to be found.

Why do patients with a cough delay seeking care at Lusaka urban health centres? A health systems research approach

SETTING

Primary health centres in urban Lusaka, Zambia.

OBJECTIVES

To describe the distribution and risk factors for delay among patients presenting with a cough to the urban health centres.

DESIGN

A health systems research methodology was used. A participatory workshop analysed the problem and designed a cross-sectional survey of patients attending two urban health centres. Initial data analyses were performed in a second workshop, with results discussed with a broad range of policy-makers, health care staff and community members interested in tuberculosis.

RESULTS

A total of 427 patients were interviewed; 35% had delayed for more than one month. Delay was associated with older age, severe underlying illness, poor perception of the health services, distance from the clinic and prior attendance at a private clinic. There was no relationship between delay and knowledge about tuberculosis, nor with education, socio-economic level or gender. Tuberculosis and HIV were felt to be closely linked and highly stigmatised, but stigmatising attitudes were not associated with longer delays.

CONCLUSIONS

The health systems research methodology was an effective way to engage the staff of the district health services in action-oriented research. Investing in improvements in the health system and ensuring accessibility for older and more disabled patients is likely to reduce delays in diagnosis and help to improve tuberculosis control in Lusaka.

HIV-1 and recurrence, relapse, and reinfection of tuberculosis after cure: a cohort study in South African mineworkers

BACKGROUND

The proportion of recurrent tuberculosis cases attributable to relapse or reinfection and the risk factors associated with these different mechanisms are poorly understood. We followed up a cohort of 326 South African mineworkers, who had successfully completed treatment for pulmonary tuberculosis in 1995, to determine the rate and mechanisms of recurrence.

METHODS

Patients were examined 3 and 6 months after cure, and then were monitored by the routine tuberculosis surveillance system until December, 1998. IS6110 DNA fingerprints from initial and subsequent episodes of tuberculosis were compared to determine whether recurrence was due to relapse or reinfection All patients gave consent for HIV-1 testing.

FINDINGS

During follow-up (median 25.1 months, IQR 13.2-33.4), 65 patients (20%) had a recurrent episode of tuberculosis, a recurrence rate of 10.3 episodes per 100 person-years at risk (PYAR)-16.0 per 100 pyar in HIV-1-positive patients and 6.4 per 100 pyar in HIV-1-negative patients. Paired DNA fingerprints were available in 39 of 65 recurrences: 25 pairs were identical (relapse) and 14 were different (reinfection). 93% (13/14) of recurrences within the first 6 months were attributable to relapse compared with 48% (12/25) of later recurrences. HIV-1 infection was a risk factor for recurrence (hazard ratio 2.4, 95% CI 1.5-4.0), due to its strong association with disease caused by reinfection (18.7 2.4-143), but not relapse (0.58; 0.24-1.4). Residual cavitation and increasing years of employment at the mine were risk factors for relapse.

INTERPRETATION

In a setting with a high risk of tuberculous infection, HIV-1 increases the risk of recurrent tuberculosis because of an increased risk of reinfection. Interventions to prevent recurrent disease, such as lifelong chemoprophylaxis in HIV-1-positive tuberculosis patients, should be further assessed.

Socio-economic, gender and health services factors affecting diagnostic delay for tuberculosis patients in urban Zambia

In-depth interviews regarding health seeking behaviour were conducted with 202 adults registered with pulmonary tuberculosis at the centralized Chest Clinic in Lusaka, Zambia. The median (mean) diagnostic delay was 8.6 (9) weeks, and was significantly associated with the following factors: female sex, lower education, more than six instances of health-seeking encounters, outpatient diagnosis of tuberculosis, and visiting a private doctor or traditional healer. More effective tuberculosis control interventions require novel methods of accessing women and less educated people. Decentralization of public tuberculosis care and improved integration with private sector health providers may also reduce diagnostic delay.

Utility of nucleic acid amplification techniques for the diagnosis of pulmonary tuberculosis in sub-Saharan Africa

SETTING

Lusaka, Zambia.

OBJECTIVES

To investigate the utility of nucleic amplification tests for the diagnosis of pulmonary tuberculosis in a resource-poor setting with a high incidence of human immunodeficiency virus (HIV).

DESIGN

Sputum specimens from suspects attending a referral chest clinic were examined by low-cost 'in-house' one-tube nested polymerase chain reaction (PCR), the enhanced Gen-Probe Amplified Mycobacterium Direct Test (AMTD), auramine smear and Lowenstein-Jensen culture.

RESULTS

PCR and AMTD detected respectively 80% and 92% of smear-positive specimens and 40% and 60% of smear-negative, culture-positive specimens. AMTD was positive for 18 culture-negative suspects; subsequent investigation indicated these to be six confirmed tuberculosis patients, nine judged from radiological data and clinical follow-up studies to have pulmonary tuberculosis, and three non-tuberculosis patients. Sensitivity for smear, culture, PCR and AMTD, when compared to a gold standard incorporating both microbiological and clinical data, was respectively 29%, 69%, 55% and 81%.

CONCLUSION

In this setting, the sensitivity of the low-cost PCR proved insufficient for its effective use as a tool for diagnosing pulmonary tuberculosis, while AMTD performed considerably better than the current laboratory methods for diagnosis of pulmonary tuberculosis. However, the high cost of this technology may limit its application in the public sector of low-income countries.

Long-term effect of preventive therapy for tuberculosis in a cohort of HIV-infected Zambian adults

OBJECTIVE

To determine the long-term effect of preventive therapy (PT) for tuberculosis on the rates of tuberculosis, mortality and HIV progression.

METHODS

In a randomized controlled trial, 1053 HIV-positive Zambian adults received isoniazid (H) for 6 months, rifampicin plus pyrazinamide (RZ) for 3 months, or a placebo. CD4 percentage, neopterin, absolute lymphocyte count and haemoglobin were measured from enrolment (absolute CD4 cell counts from 12 months after enrolment). Because PT reduced the incidence of tuberculosis, eligible placebo subjects were offered H. Here, tuberculosis and mortality rates are compared in the three original arms (intention to treat) using data beyond the end of the trial (average follow-up 3 years; maximum 7 years).

RESULTS

There were 102 cases of tuberculosis and 281 deaths (rates 3.6 and 9.0/100 person-years, respectively). There was no significant difference between the tuberculosis rates in the H and RZ groups at any time. The effect of H/RZ on tuberculosis diminished over time (P = 0.011) but the cumulative risk of tuberculosis in the first 2.5 years was significantly lower in the H/RZ group than the placebo group (rate ratio 0.55; 95% confidence interval 0.32-0.93; P = 0.028). There was no significant effect of PT on mortality or progression markers. Tuberculosis was associated with an increased mortality (adjusted rate ratio 1.96; 95% confidence interval 1.21-3.18; P = 0.006).

CONCLUSIONS

Both PT regimens protect against tuberculosis for at least 2.5 years but appear to have no effect on HIV progression or mortality. These results may be used in cost-effectiveness models of PT.

Tuberculosis treatment failure and drug resistance--same strain or reinfection?

Tuberculosis patients may have Mycobacterium tuberculosis in their sputum at the end of treatment, and may show new drug resistance, due to either inadequate treatment of the original episode or reinfection with a new strain during therapy. In a cohort study of mineworkers with tuberculosis in South Africa, 57 of 438 patients had positive sputum cultures 6 months after recruitment in 1995. Of the 31 patients who initially had fully sensitive strains, 3 developed multidrug resistance (MDR) and 3 single-drug resistance (SDR). Of the 6 who started with SDR, 3 became MDR. HIV infection was not associated with drug resistance at enrollment or 6 months later. We compared pairs of DNA fingerprints from isolates of M. tuberculosis at recruitment and 6 months later in the 48 patients for whom we had both available. In 45, the pairs were identical. In 1 patient, although both isolates were fully sensitive, the later fingerprint had 1 less band (transposition). In 2 pairs, the fingerprint patterns were completely different: one seemed to be the result of laboratory error and the other was a true reinfection with an MDR strain. Despite a high risk of infection, with a moderate proportion of background drug-resistant strains (11% SDR, 6% MDR), reinfection is not a common cause of treatment failure or drug resistance at 6 months.

Surveillance of drug-resistant tuberculosis and molecular evaluation of transmission of resistant strains in refugee and non-refugee populations in North-Eastern Kenya

SETTING

Three refugee camp complex clinics and an adjacent non-refugee treatment centre in North-Eastern Kenya.

OBJECTIVES

To use conventional and molecular epidemiology tools to determine: 1) the prevalence of drug resistance in newly diagnosed patients with smear-positive pulmonary tuberculosis in refugee and non-refugee populations; 2) risk factors for resistance in the two populations; and 3) whether IS6110 restriction fragment length polymorphism (RFLP) and spoligotyping showed similarities in DNA fingerprinting patterns of drug-resistant isolates that could infer transmission within and between the two populations.

RESULTS

Of 241 isolates from the camps, 44 (18.3%) were resistant to one or more drugs, seven of which (2.9%) were multidrug-resistant TB (MDR-TB). Of 88 isolates from the non-refugees, five (5.7%) were resistant to one or more drugs without MDR-TB. Drug resistance was higher in the camps than in the non-refugee population (OR = 3.7; 95%CI 1.42-9.68; P < 0.007). Resistance was significantly higher in one camp compared with the other two, despite a comparable ethnic distribution. Unusually, females were more associated with drug resistance than their male counterparts in both populations (OR = 2.3; 95%CI 1.2-4.8; P = 0.008). There was evidence of transmission of streptomycin-resistant strains in the refugee population. DNA fingerprints of resistant strains from the non-refugee population were unique and different from those in the refugee camps.

CONCLUSION

The observed high levels of drug resistance and MDR-TB, combined with evidence of transmission of strains resistant to streptomycin in the refugee population, suggest a need for strengthened TB control programmes in settings with a high risk of developing drug-resistant strains.

Tuberculosis control and molecular epidemiology in a South African gold-mining community

BACKGROUND

Gold miners have very high rates of tuberculosis. The contribution of infections imported into mining communities versus transmission within them is not known and has implications for control strategies.

METHODS

We did a prospective, population-based molecular and conventional epidemiological study of pulmonary tuberculosis in a group of goldminers. Clusters were defined as groups of patients with Mycobacterium tuberculosis isolates with identical IS6110 DNA fingerprints. We compared the frequency of possible risk factors in the clustered and non-clustered patients whose isolates had fingerprints with more than four bands, and re-interviewed members of 45 clusters.

FINDINGS

Of 448 patients, ten were excluded because they had false-positive cultures. Fingerprints were made in 419 of 438, of which 371 had more than four bands. 248 of 371 were categorised into 62 clusters. At least 50% of tuberculosis cases were due to transmission within the community. Patients who had failed treatment at entry to the study were more likely to be in clusters (adjusted odds ratio 3.41 [95% CI 1.25-9.27]). Patients with multidrug-resistant isolates were more likely to have failed treatment but were less likely to be clustered than those with a sensitive strain (0.27 [0.09-0.83]). HIV infection was common (177 of 370 tested) but not associated with clustering.

INTERPRETATION

Despite a control programme that cures 86% of new cases, most tuberculosis in this mining community is due to ongoing transmission. Persistently infectious individuals who have previously failed treatment may be responsible for one third of tuberculosis cases. WHO targets for cure rates are not sufficient to interrupt transmission of tuberculosis in this setting. Indicators that are more closely linked to the rate of ongoing transmission are needed.

Drug-resistant pulmonary tuberculosis in a cohort of southern African goldminers with a high prevalence of HIV infection

OBJECTIVES

To determine rates of drug resistance to Mycobacterium tuberculosis and associated risk factors, including HIV infection.

DESIGN

Prospective cohort study of patients with pulmonary tuberculosis.

SETTING

The study population comprised 28,522 men working on four goldmines in Westonaria, Gauteng. Health care is provided at a 240-bed mine hospital, Gold Fields West Hospital, and its primary health care facilities.

SUBJECTS

All 425 patients with culture-positive pulmonary tuberculosis identified in 1995.

OUTCOME MEASURES

Tuberculosis drug resistance on enrollment and after 6 months' treatment.

RESULTS

There were 292 cases of new tuberculosis, 77 of recurrent disease and 56 prevalent cases in treatment failure. Two hundred and seven patients (48.7%) were HIV infected. Primary resistance to one or more drugs (9%) was similar to the 11% found in a previous study done on goldminers in 1989. Primary multidrug resistance (0.3%) was also similar (0.8%). Acquired multidrug resistance was 18.1%: 6.5% for recurrent disease and 33.9% in treatment failure cases. Neither HIV infection nor the degree of immunosuppression as assessed by CD4+ lymphocyte counts was associated with drug resistance at the start or end of treatment. New patterns of drug resistance were present in 9 of 52 patients in treatment failure at 6 months, 1 of whom was HIV-infected.

CONCLUSION

Primary and acquired drug resistance rates are stable in this population and are not affected by the high prevalence of HIV infection.