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Diagnostics that more accurately detect and quantify viable Mycobacterium tuberculosis (Mtb) in the sputum of patients undergoing therapy are needed. Current culture- and molecular-based tests have shown limited efficacy for monitoring treatment response in TB patients, either due to the presence of viable sub-populations of Mtb which fail to grow under standard culture conditions (termed differentially detectable/culturable Mtb, DD Mtb) or the prolonged half-life of Mtb DNA in sputum. Here, we report an optimized RNA-based method for detecting and quantifying viable Mtb from patient sputum during the course of therapy. We first empirically derived a novel RNA extraction protocol from sputum that improves recovery of Mtb RNA while almost completely eliminating contamination from Mtb DNA and host nucleic acids. Next, we identified five Mtb 16S rRNA primer sets with varying limits of detection that were capable of distinguishing between live versus dead H37Rv Mtb. This combined protocol was then tested on sputa from a longitudinal cohort of patients receiving therapy for drug sensitive (DS) or drug resistant (DR) TB with first-line or second-line regimens, respectively. Results were compared with that of culture, including CFU, BACTEC MGIT, and a limiting dilution assay capable of detecting DD Mtb. The five 16S rRNA primer sets positively identified nearly all (range 94-100%) culture positive sputa, and a portion (19-37%) of culture negative sputa. In comparison, ten highly expressed Mtb mRNAs showed positivity in 72-86% of culture positive sputa, and in 0-13% of culture negative sputa. Two of the five 16S rRNA primer sets were able to positively identify 100% of culture positive sputa, and when tested on culture negative sputa from the DS cohort at 2 months post-initiation of therapy, identified 40% of samples as positive; a percentage that is in line with expected treatment failure rates when first-line therapy is discontinued early. These two primer sets also detected 16S rRNA in 13-20% of sputa at 6 months post-initiation of therapy in the DR cohort. Cycle threshold values for 16S rRNA showed a strong correlation with Mtb numbers as determined by culture (R > 0.87), including as Mtb numbers declined during the course of treatment with first-line and second-line regimens. The optimized molecular assay outlined here may have utility for monitoring treatment response in TB patients., (© 2022. The Author(s).)

Standard methods for enumerating Mycobacterium tuberculosis in patient sputum can miss large populations of viable M. tuberculosis cells that are unable to grow either on solid medium or in liquid medium unless the medium has been extensively diluted. Because these bacteria can be detected in liquid medium after limiting dilution, they have been termed differentially culturable or differentially detectable M. tuberculosis (DD- Mtb ). Treatment with isoniazid (H), rifampin (R), pyrazinamide (Z), and ethambutol (E) (HRZE) for 1 to 2 weeks has been shown to increase the representation of DD- Mtb in the sputum of drug-sensitive (DS) tuberculosis (TB) patients. However, little is known about DD- Mtb after longer periods of treatment with HRZE or in patients with drug-resistant (DR) TB who receive second-line therapies. Here, we measured the proportion of DD- Mtb cells in the sputum of 47 subjects, 29 with DS TB and 18 with DR TB, before initiation of treatment and at 2 weeks and 2 months thereafter. Prior to treatment, DD- Mtb cells represented the majority of M. tuberculosis cells in the sputum of 21% of subjects with DS TB, and this proportion rose to 65% after 2 weeks of treatment with first-line drugs. In subjects with DR TB, DD- Mtb cells were found in the sputum of 29% of subjects prior to treatment initiation, and this proportion remained steady at 31% after 2 weeks of treatment with second-line drugs. By 2 months, DD- Mtb cells were detected in the sputum of only 2/15 (13.3%) subjects with DS TB and in 0/15 of subjects with DR TB. One of the DS subjects whose sputum was positive for DD- Mtb at month 2 later experienced treatment failure.

Background: We aimed to determine whether the Xpert MTB/RIF (Xpert) assay is a useful adjunct to culture for the rapid diagnosis of tuberculosis (TB) using gastric lavage aspirates (GLAs) in children aged < 5 years., Methods: We reviewed the yield from diagnostic modalities in children suspected of having TB followed at an infectious disease research and treatment center in Port-au-Prince, Haiti, from 2011 to 2016., Results: In 187 children clinically diagnosed with TB, a microbiologic diagnosis could be established in 40 (21%). Cultures, Xpert, and smears were positive in 30 (19%), 28 (17%), and 3 (1.6%) children, respectively. Ten cases that would not have been diagnosed by culture alone were found by the use of the Xpert assay. Collecting 2 GLA samples optimized microbiologic yield., Conclusions: In GLAs, Xpert increased the yield of microbiologically documented cases by 33%. Additionally, the rapidity of diagnosis potentially makes Xpert a valuable adjunct in initiating treatment for TB in children. Smear microscopy has low sensitivity in GLA and did not add to the documented cases. Our findings also highlight the low rate of microbiologic confirmation of clinically diagnosed TB., (© The Author(s) 2020. Published by Oxford University Press on behalf of The Journal of the Pediatric Infectious Diseases Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

BACKGROUNDControl of the tuberculosis (TB) pandemic remains hindered in part by a lack of simple and accurate measures of treatment efficacy, as current gold standard markers rely on sputum-based assays that are slow and challenging to implement. However, previous work identified urinary N1, N12-diacetylspermine (DiAcSpm), neopterin, hydroxykynurenine, N-acetylhexosamine, ureidopropionic acid, sialic acid, and mass-to-charge ratio (m/z) 241.0903 as potential biomarkers of active pulmonary TB (ATB). Here, we evaluated their ability to serve as biomarkers of TB treatment response and mycobacterial load.METHODSWe analyzed urine samples prospectively collected from 2 cohorts with ATB. A total of 34 study participants from African countries treated with first-line TB therapy rifampin, isoniazid, pyrazinamide, and ethambutol (HRZE) were followed for 1 year, and 35 participants from Haiti treated with either HRZE or an experimental drug were followed for 14 days. Blinded samples were analyzed by untargeted HPLC-coupled high-resolution TOF-mass spectrometry.RESULTSUrinary levels of all 7 molecules significantly decreased by week 26 of successful treatment (P = 0.01 to P < 0.0001) and positively correlated with sputum mycobacterial load (P < 0.0001). Urinary DiAcSpm levels decreased significantly in participants treated with HRZE as early as 14 days (P < 0.0001) but remained unchanged in cases of ineffective therapy (P = 0.14).CONCLUSIONUrinary DiAcSpm, neopterin, hydroxykynurenine, N-acetylhexosamine, ureidopropionic acid, sialic acid, and m/z 241.0903 reductions correlated with successful anti-TB treatment and sputum mycobacterial load. Urinary DiAcSpm levels exhibited reductions capable of differentiating treatment success from failure as early as 2 weeks after the initiation of chemotherapy, advocating its further development as a potentially simple, noninvasive biomarker for assessing treatment response and bacterial load.FUNDINGThis work was supported by the Clinical and Translational Science Center at Weill Cornell College of Medicine (NIH/NCATS 1 UL1 TR002384-02 and KL2TR000458), the Department of Defense (PR170782), the National Institute of Allergy and Infectious Disease grants (NIAID T32AI007613-16, K24 AI098627, and K23 AI131913), the NIH Fogarty International Center grants (R24 TW007988 and TW010062), NIH grant (R01 GM135926), the Abby and Howard P. Milstein Program in Chemical Biology and Translational Medicine, and the Tuberculosis Research Units Networks (TBRU-N, AI111143).

This study was conducted in treatment-naive adults with drug-susceptible pulmonary tuberculosis in Port-au-Prince, Haiti, to assess the safety, bactericidal activity, and pharmacokinetics of nitazoxanide (NTZ). This was a prospective phase II clinical trial in 30 adults with pulmonary tuberculosis. Twenty participants received 1 g of NTZ orally twice daily for 14 days. A control group of 10 participants received standard therapy over 14 days. The primary outcome was the change in time to culture positivity (TTP) in an automated liquid culture system. The most common adverse events seen in the NTZ group were gastrointestinal complaints and headache. The mean change in TTP in sputum over 14 days in the NTZ group was 3.2 h ± 22.6 h and was not statistically significant ( P  = 0.56). The mean change in TTP in the standard therapy group was significantly increased, at 134 h ± 45.2 h ( P  < 0.0001). The mean NTZ MIC for Mycobacterium tuberculosis isolates was 12.3 μg/ml; the mean NTZ maximum concentration ( C max ) in plasma was 10.2 μg/ml. Negligible NTZ levels were measured in sputum. At the doses used, NTZ did not show bactericidal activity against M. tuberculosis Plasma concentrations of NTZ were below the MIC, and its negligible accumulation in pulmonary sites may explain the lack of bactericidal activity. (This study has been registered at ClinicalTrials.gov under identifier NCT02684240.)., (Copyright © 2020 American Society for Microbiology.)

Background: Treatment outcomes for multidrug-resistant tuberculosis remain poor. We aimed to estimate the association of treatment success and death with the use of individual drugs, and the optimal number and duration of treatment with those drugs in patients with multidrug-resistant tuberculosis., Methods: In this individual patient data meta-analysis, we searched MEDLINE, Embase, and the Cochrane Library to identify potentially eligible observational and experimental studies published between Jan 1, 2009, and April 30, 2016. We also searched reference lists from all systematic reviews of treatment of multidrug-resistant tuberculosis published since 2009. To be eligible, studies had to report original results, with end of treatment outcomes (treatment completion [success], failure, or relapse) in cohorts of at least 25 adults (aged >18 years). We used anonymised individual patient data from eligible studies, provided by study investigators, regarding clinical characteristics, treatment, and outcomes. Using propensity score-matched generalised mixed effects logistic, or linear regression, we calculated adjusted odds ratios and adjusted risk differences for success or death during treatment, for specific drugs currently used to treat multidrug-resistant tuberculosis, as well as the number of drugs used and treatment duration., Findings: Of 12 030 patients from 25 countries in 50 studies, 7346 (61%) had treatment success, 1017 (8%) had failure or relapse, and 1729 (14%) died. Compared with failure or relapse, treatment success was positively associated with the use of linezolid (adjusted risk difference 0·15, 95% CI 0·11 to 0·18), levofloxacin (0·15, 0·13 to 0·18), carbapenems (0·14, 0·06 to 0·21), moxifloxacin (0·11, 0·08 to 0·14), bedaquiline (0·10, 0·05 to 0·14), and clofazimine (0·06, 0·01 to 0·10). There was a significant association between reduced mortality and use of linezolid (-0·20, -0·23 to -0·16), levofloxacin (-0·06, -0·09 to -0·04), moxifloxacin (-0·07, -0·10 to -0·04), or bedaquiline (-0·14, -0·19 to -0·10). Compared with regimens without any injectable drug, amikacin provided modest benefits, but kanamycin and capreomycin were associated with worse outcomes. The remaining drugs were associated with slight or no improvements in outcomes. Treatment outcomes were significantly worse for most drugs if they were used despite in-vitro resistance. The optimal number of effective drugs seemed to be five in the initial phase, and four in the continuation phase. In these adjusted analyses, heterogeneity, based on a simulated I 2 method, was high for approximately half the estimates for specific drugs, although relatively low for number of drugs and durations analyses., Interpretation: Although inferences are limited by the observational nature of these data, treatment outcomes were significantly better with use of linezolid, later generation fluoroquinolones, bedaquiline, clofazimine, and carbapenems for treatment of multidrug-resistant tuberculosis. These findings emphasise the need for trials to ascertain the optimal combination and duration of these drugs for treatment of this condition., Funding: American Thoracic Society, Canadian Institutes of Health Research, US Centers for Disease Control and Prevention, European Respiratory Society, Infectious Diseases Society of America., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Peripheral blood transcriptome signatures that distinguish active pulmonary tuberculosis (TB) from control groups have been reported, but correlations of these signatures with sputum mycobacterial load are incompletely defined., Methods: We assessed the performance of published TB transcriptomic signatures in Haiti, and identified transcriptomic biomarkers of TB bacterial load in sputum as measured by Xpert® MTB/RIF molecular testing. People in Port au Prince, Haiti, with untreated pulmonary TB (n = 51) formed the study cohort: 19 people with low and 32 with high sputum Mycobacterium tuberculosis load. Peripheral whole blood transcriptomes were generated using RNA sequencing., Results: Twenty of the differentially expressed transcripts in TB vs. no TB were differentially expressed in people with low vs. high sputum mycobacterial loads. The difference between low and high bacterial load groups was independent of radiographic severity. In a published data set of transcriptomic response to anti-tuberculosis treatment, this 20-gene subset was more treatment-responsive at 6 months than the full active TB signature., Conclusion: We identified genes whose transcript levels in the blood distinguish active TB with high vs. low M. tuberculosis loads in the sputum. These transcripts may reveal mechanisms of mycobacterial control of M. tuberculosis during active infection, as well as identifying potential biomarkers for bacterial response to anti-tuberculosis treatment.

Background: Tuberculosis (TB) is the leading infectious cause of death worldwide. A major barrier to control of the pandemic is a lack of clinical biomarkers with the ability to distinguish active TB from healthy and sick controls and potential for development into point-of-care diagnostics., Methods: We conducted a prospective case control study to identify candidate urine-based diagnostic biomarkers of active pulmonary TB (discovery cohort) and obtained a separate blinded "validation" cohort of confirmed cases of active pulmonary TB and controls with non-tuberculous pulmonary disease for validation. Clean-catch urine samples were collected and analyzed using high performance liquid chromatography-coupled time-of-flight mass spectrometry., Results: We discovered ten molecules from the discovery cohort with receiver-operator characteristic (ROC) area-under-the-curve (AUC) values >85%. These 10 molecules also significantly decreased after 60 days of treatment in a subset of 20 participants followed over time. Of these, a specific combination of diacetylspermine, neopterin, sialic acid, and N-acetylhexosamine exhibited ROC AUCs >80% in a blinded validation cohort of participants with active TB and non-tuberculous pulmonary disease., Conclusion: Urinary levels of diacetylspermine, neopterin, sialic acid, and N-acetylhexosamine distinguished patients with tuberculosis from healthy controls and patients with non-tuberculous pulmonary diseases, providing a potential noninvasive biosignature of active TB., Funding: This study was funded by Weill Cornell Medicine, the National Institute of Allergy and Infectious Diseases, the Clinical and Translational Science Center at Weill Cornell, the NIH Fogarty International Center grants, and the NIH Tuberculosis Research Unit (Tri-I TBRU)., (Copyright © 2018 The Author(s). Published by Elsevier B.V. All rights reserved.)

The World Health Organization recommends diagnosing Multidrug-Resistant Tuberculosis (MDR-TB) in high burden countries by detection of mutations in Rifampin (RIF) Resistance Determining Region of Mycobacterium tuberculosis rpoB gene with rapid molecular tests GeneXpert MTB/RIF and Hain MTBDRplus. Such mutations are found in >95% of Mycobacterium tuberculosis strains resistant to RIF by conventional culture-based drug susceptibility testing (DST). However routine diagnostic screening with molecular tests uncovered specific "low level" rpoB mutations conferring resistance to RIF below the critical concentration of 1 μg/ml in some phenotypically susceptible strains. Cases with discrepant phenotypic (susceptible) and genotypic (resistant) results for resistance to RIF account for at least 10% of resistant diagnoses by molecular tests and urgently require new guidelines to inform therapeutic decision making. Eight strains with a "low level" rpoB mutation L511P were isolated by GHESKIO laboratory between 2008 and 2012 from 6 HIV-negative and 2 HIV-positive patients during routine molecular testing. Five isolates with a single L511P mutation and two isolates with double mutation L511P&M515T had MICs for RIF between 0.125 and 0.5 μg/ml and tested susceptible in culture-based DST. The eighth isolate carried a double mutation L511P&D516C and was phenotypically resistant to RIF. All eight strains shared the same spoligotype SIT 53 commonly found in Haiti but classic epidemiological investigation failed to uncover direct contacts between the patients. Whole Genome Sequencing (WGS) revealed that L511P cluster isolates resulted from a clonal expansion of an ancestral strain resistant to Isoniazid and to a very low level of RIF. Under the selective pressure of RIF-based therapy the strain acquired mutation in the M306 codon of embB followed by secondary mutations in rpoB and escalation of resistance level. This scenario highlights the importance of subcritical resistance to RIF for both clinical management of patients and public health and provides support for introducing rpoB mutations as proxy for MICs into laboratory diagnosis of RIF resistance. This study illustrates that WGS is a promising multi-purpose genotyping tool for high-burden settings as it provides both "gold standard" sequencing results for prediction of drug susceptibility and a high-resolution data for epidemiological investigation in a single assay.

The World Health Organization has recommended use of molecular-based tests MTBDRplus and GeneXpert MTB/RIF to diagnose multidrug-resistant tuberculosis in developing and high-burden countries. Both tests are based on detection of mutations in the Rifampin (RIF) Resistance-Determining Region of DNA-dependent RNA Polymerase gene (rpoB). Such mutations are found in 95-98% of Mycobacterium tuberculosis strains determined to be RIF-resistant by the "gold standard" culture-based drug susceptibility testing (DST). We report the phenotypic and genotypic characterization of 153 consecutive clinical Mycobacterium tuberculosis strains diagnosed as RIF-resistant by molecular tests in our laboratory in Port-au-Prince, Haiti. 133 isolates (86.9%) were resistant to both RIF and Isoniazid and 4 isolates (2.6%) were RIF mono-resistant in MGIT SIRE liquid culture-based DST. However the remaining 16 isolates (10.5%) tested RIF-sensitive by the assay. Five strains with discordant genotypic and phenotypic susceptibility results had RIF minimal inhibitory concentration (MIC) close to the cut-off value of 1 µg/ml used in phenotypic susceptibility assays and were confirmed as resistant by DST on solid media. Nine strains had sub-critical RIF MICs ranging from 0.063 to 0.5 µg/ml. Finally two strains were pan-susceptible and harbored a silent rpoB mutation. Our data indicate that not only detection of the presence but also identification of the nature of rpoB mutation is needed to accurately diagnose resistance to RIF in Mycobacterium tuberculosis. Observed clinical significance of low-level resistance to RIF supports the re-evaluation of the present critical concentration of the drug used in culture-based DST assays.

Setting: The uptake of tests endorsed by the World Health Organization to detect and appropriately confirm multidrug-resistant tuberculosis (MDR-TB) in low-income countries remains insufficient., Objective: To validate the implementation of line-probe assays (LPA) and liquid culture to develop an algorithm to detect MDR-TB in the challenging setting of Haiti., Methods: Through an EXPAND-TB (Expanding Access to New Diagnostics for TB) partnership, proficiency testing and validation of 221 acid-fast bacilli positive specimens were performed. Sensitivity, cost and processing time were analysed., Results: Using liquid vs. solid culture shortened the turnaround time from 54 to 19 days, with a sensitivity of 100% vs. 98.6% and a total cost reduction of 13%. LPA detected all TB and MDR-TB cases at a lower cost than culture, in a mean time of 7.5 days., Conclusion: The combined use of molecular and liquid culture techniques accelerates the accurate diagnosis of TB and susceptibility testing against first-line drugs in a significantly shorter time, and is less expensive. The implementation of this new algorithm could significantly and accurately improve the screening and treatment follow-up of patients affected with TB and MDR-TB.

Setting: The Groupe Haitien d'Etude du Sarcome de Kaposi et des Infections Opportunistes (the GHESKIO AIDS and TB Center) in Port-au-Prince, Haiti., Objective: To measure the effectiveness of the standard TB retreatment regimen (2HRZES/1HRZE/5HRE) in human immunodeficiency virus (HIV) infected adults., Design: Cohort study., Results: Of 1318 HIV-infected patients with access to antiretroviral therapy following World Health Organization guidelines, 56 were diagnosed with recurrent pulmonary TB and retreated with the standard retreatment regimen: 10 patients (18%) died during retreatment, 3 (5%) defaulted, and 2 (4%) failed treatment. Forty-one patients (73%) achieved retreatment 'success' (cure, treatment completed). Of these, 8 (20%) died during follow-up, 5 (12%) were lost, and 5 (12%) had a second recurrence of TB. Only 26 (46%) of the 56 patients remained alive, in care, and TB-free after a median of 36 months of follow-up., Conclusion: HIV-infected patients treated for recurrent TB with the standard retreatment regimen have high mortality and poor long-term outcomes.

Objective: Tuberculosis is the major opportunistic infection of HIV/AIDS in developing countries. We investigated the prevalence rate of multidrug-resistant (MDR) tuberculosis at an HIV voluntary counseling and testing (VCT) center in Port-au-Prince, Haiti., Design and Methods: A cross-sectional prevalence study of MDR-tuberculosis was conducted at a VCT Center. All patients reporting at least 5 days of cough were screened for tuberculosis, including sputum culture. All Mycobacteria tuberculosis isolates underwent drug susceptibility testing., Results: Between January 2000 and December 2002, isolates from 330 patients underwent drug susceptibility testing. MDR-tuberculosis was documented in 16 (6%) of 281 patients with primary tuberculosis and 10 (20%) of 49 patients with recurrent tuberculosis. In patients with primary disease, 11 (10%) of 115 HIV-infected patients had MDR-tuberculosis compared with five (3%) of 166 HIV-negative patients, (risk ratio 3.2; 95% confidence interval 1.1-8.9; P = 0.0331)., Conclusion: Multidrug resistance was prevalent among patients found to have pulmonary tuberculosis at an HIV testing center in Port-au-Prince. Patients with primary pulmonary tuberculosis who were HIV-co-infected were more likely to have multidrug resistance than HIV-negative patients. Assiduous attention to tuberculosis infection control measures at HIV testing centers in developing countries is critical to prevent nosocomial MDR-tuberculosis transmission. Measures may include appropriate ventilation, outdoor seating, ultra-violet lights, and rapid on-site screening for tuberculosis.

In the Caribbean region, the lifetime risk of active tuberculosis (TB) in purified protein derivative (PPD)-positive HIV-infected patients is 50%. Screening of individuals with cough who came to an HIV voluntary counseling and testing center in Haiti revealed active TB in 33% of patients. TB prophylaxis is effective in preventing active disease in HIV-infected individuals, and secondary prophylaxis has been shown to reduce recurrence in patients diagnosed with TB at more advanced stages of immunosuppression. Recommendations for anti-TB therapy differ according to whether antiretroviral therapy is available or not and according to whether the TB diagnosis is made while the patient is receiving antiretroviral therapy or not. This article summarizes a presentation by Jean William Pape, MD, at the first CHART Caribbean Conference on the Clinical Management of HIV/AIDS in Montego Bay, Jamaica in June 2004.

Objective: To describe the integration of tuberculosis screening into the activities of an HIV voluntary counselling and testing (VCT) centre in a country with endemic tuberculosis., Setting: An HIV VCT centre in Port au Prince, Haiti., Design: All patients presenting for HIV VCT who reported cough received same-day evaluation for active tuberculosis. Of the 1327 adults presenting to the centre for the first time between January and April 1997, 263 (20%) reported cough and of these 241 (92%) were evaluated., Results: Of the 241 patients evaluated for cough, 76 (32%) were diagnosed with pulmonary tuberculosis. Of the 76 patients diagnosed with pulmonary tuberculosis, 28 (37%) had a positive smear for acid-fast bacilli (AFB), 14 (18%) had a negative AFB smear but a positive sputum culture for Mycobacterium tuberculosis, and 34 (45%) had culture-negative tuberculosis. Also, 31 out of 241 (13%) VCT clients evaluated for cough were diagnosed with bacterial pneumonia., Conclusion: This report confirms that in areas with a high HIV and tuberculosis prevalence, a high proportion of VCT clients have active pulmonary tuberculosis. The integration of tuberculosis screening offers several benefits, including the diagnosis and treatment of large numbers of individuals with tuberculosis, a decreased risk of nosocomial tuberculosis transmission, and the opportunity to provide tuberculosis prophylaxis to HIV-positive patients in whom tuberculosis has been excluded. Future studies are needed to determine the cost-effectiveness of integrated tuberculosis and HIV VCT services, and whether integration should be recommended in all countries with high HIV and tuberculosis rates.

Objectives: This study evaluated a novel approach to the delivery of directly observed therapy (DOT) for tuberculosis in Haiti., Methods: A total of 194 patients (152 HIV seropositive, 42 HIV seronegative) received daily unsupervised triple-drug therapy for 4 to 8 weeks, followed by twice-weekly 2-drug therapy for the remainder of the 6-month period. DOT was deferred until initiation of the twice-weekly phase., Results: A total of 169 of 194 patients (87.1%) completed the 6-month course. The program of deferred DOT had an effectiveness of 85%. Overall cost was reduced by approximately 40%., Conclusions: Flexible approaches to DOT, integrating behavioral knowledge, cost considerations, and practicality may improve completion rates and program effectiveness.

A review was conducted in Haiti to determine the timing and outcome of active tuberculosis (TB) in human immunodeficiency virus (HIV)-positive patients who had previously received isoniazid (INH) prophylaxis. Of 1005 HIV-seropositive patients who completed INH prophylaxis, 14 (1.4%) subsequently had active TB diagnosed. The median interval between discontinuation of INH prophylaxis and TB diagnosis was 8 months for 6 patients receiving 6 months of INH, 22 months for 5 patients receiving 12-24 months of INH, and 40 months for 3 patients receiving 24-36 months of INH (P = .026). There is a postprophylaxis effect on INH that is dependent upon the duration of therapy.

Tuberculosis occurring with human immunodeficiency virus (HIV) infection is a serious and growing public health problem. We have carried out a randomised clinical trial of a 12-month course of isoniazid plus vitamin B6 versus vitamin B6 alone in Port-au-Prince, Haiti, to assess the efficacy of isoniazid in preventing active tuberculosis in symptom-free HIV-infected individuals. The effect of prophylaxis on the development of HIV disease, AIDS, and death was also investigated. 118 subjects were assigned treatment with isoniazid plus B6 (n = 58) or B6 alone (n = 60) between 1986 and 1989. The treatment groups were similar at study entry in demographic, clinical, and immunological characteristics. Interim analysis in 1990 revealed no significant difference in tuberculosis outcome measures. Follow-up was continued until 1992, at which time significant protection by isoniazid against the development of tuberculosis was apparent, both for the whole study population and for subjects positive for purified protein derivative of tuberculin (PPD). The incidence of tuberculosis was lower in isoniazid recipients than in patients who received B6 alone (2.2 vs 7.5 per 100 person-years). The relative risk of tuberculosis was 3.4 (95% CI 1.1-10.6) for B6 alone versus isoniazid plus B6 (p < 0.05). Isoniazid also delayed progression to HIV disease and AIDS and death. Thus isoniazid effectively decreases the incidence of tuberculosis and delays the onset of HIV-related disease in symptom-free HIV-seropositive individuals. Isoniazid prophylaxis should be considered for HIV-seropositive, PPD-positive subjects, and may also be appropriate for PPD-negative patients in areas where tuberculosis is highly endemic.