Drug malabsorption and resistant tuberculosis in HIV-infected patients

Evaluation of treatment regimens and long-term clinical outcomes in patients with isoniazid-resistant pulmonary tuberculosis: a 5-year follow-up

BACKGROUND

Considering its early bactericidal activity, isoniazid (H) is an important first-line agent in tuberculosis (TB) treatment.The aim of this study was to evaluate the treatment regimens and results of H-resistant pulmonary TB patients.

METHODS

We retrospectively evaluated treatment regimens and results of 188 H-resistant pulmonary TB patients who were treated in our center between January 2015 and December 2017. Treatment regimens applied were noted and treatment outcomes were recorded. The long-term results were evaluated.

RESULTS

Totally 174 (92.6%) of 188 patients with H-resistant pulmonary TB achieved treatment success. Ninety-seven patients (51.6%)were cured and 77 patients (41.0%) completed treatment. Five patients (2.7%) had treatment failure. Four patients (2.1%) having treatment success relapsed during one-year follow-up. Eighteen patients (9.6%) had unfavorable outcomes, including treatment failure in five (2.7%), death in nine (4.8%), and relapse in four patients (2.1%). The treatment success rate was found to be statistically higher in group 1 (9-month regimen 2HREZ/7HRE) compared with those in group 2 (9HREZ) (97.4% vs. 85.9%; p = 0.010). Group 3 (HREZFQ) and group 1 had statistically significant favorable outcomes, compared to group 2 (group 2 vs. group 3, p = 0.048; group 1 vs. group 2, p = 0.022). Interestingly, no relapse and acquired rifampicin resistance in patients occurred who received an FQ-containing regimen.

DISCUSSION

Our study results show higher treatment success and positive results with the treatment regimen containing FQ and that treatment with HREZ for nine months is associated with a lower treatment success rate.

Towards Improved Management of Tuberculous Bloodstream Infections: Pharmacokinetic Considerations with Suggestions for Better Treatment Outcomes

Mycobacterium tuberculosis is the leading cause of sepsis among HIV-infected adults, yet effective treatment remains a challenge. Efficacy of antituberculous drugs is optimized by high Area Under Curve to Minimum Inhibitory Concentration (AUC/MIC) ratios, suggesting that both the drug concentration at the disease site and time above MIC are critical to treatment outcomes. We elaborate on sepsis pathophysiology and show how it adversely affects antituberculous drug kinetics. Expanding distribution volumes secondary to an increased vascular permeability prevents the attainment of target Cmax concentrations for nearly all drugs. Furthermore, sepsis-induced metabolic acidosis promotes protonation, which increases renal clearance of basic drugs such as isoniazid and ethambutol, and hence AUCs are substantially reduced. Compared with the treatment of non-sepsis TB disease, these distorted kinetics underlie the poor treatment outcomes observed with bloodstream infections. In addition to aggressive hemodynamic management, an increase in both the dose and frequency of drug administration are warranted, at least in the early phase of treatment.

Population pharmacokinetics of ethambutol in African children: a pooled analysis

OBJECTIVES

Ethambutol protects against the development of resistance to co-administered drugs in the intensive phase of first-line anti-TB treatment in children. It is especially relevant in settings with a high prevalence of HIV or isoniazid resistance. We describe the population pharmacokinetics of ethambutol in children with TB to guide dosing in this population.

METHODS

We pooled data from 188 intensively sampled children from the DATiC, DNDi and SHINE studies, who received 15-25 mg/kg ethambutol daily according to WHO guidelines. The median (range) age and weight of the cohort were 1.9 (0.3-12.6) years and 9.6 (3.9-34.5) kg, respectively. Children with HIV (HIV+; n = 103) received ART (lopinavir/ritonavir in 92%).

RESULTS

Ethambutol pharmacokinetics were best described by a two-compartment model with first-order elimination and absorption transit compartments. Clearance was estimated to reach 50% of its mature value by 2 months after birth and 99% by 3 years. Typical steady-state apparent clearance in a 10 kg child was 15.9 L/h. In HIV+ children on lopinavir/ritonavir, bioavailability was reduced by 32% [median (IQR) steady-state Cmax = 0.882 (0.669-1.28) versus 1.66 (1.21-2.15) mg/L). In young children, bioavailability correlated with age. At birth, bioavailability was 73.1% of that in children 3.16 years or older.

CONCLUSIONS

To obtain exposure within the 2-6 mg/L recommended range for Cmax, the current doses must be doubled (or tripled with HIV+ children on lopinavir/ritonavir) for paediatric patients. This raises concerns regarding the potential for ocular toxicity, which would require evaluation.

Diagnostic Accuracy of Therapeutic Drug Monitoring During Tuberculosis Treatment

Tuberculosis (TB) patients co-infected with human immunodeficiency virus (HIV) are more likely to have low blood concentrations of the first-line anti-TB drugs (associated with poor outcomes). Therapeutic drug monitoring (TDM) is recommended for certain TB patient populations at increased risk for a poor outcome. Our objective was to estimate the diagnostic accuracy of a 2-hour TDM serum sample for the first-line anti-TB drugs among HIV/TB patients, and evaluate the information gained by an additional 6-hour sample. We created a virtual (n = 1,000) HIV/TB patient population and performed pharmacokinetic (PK) simulations using published population models for isoniazid, rifampin, pyrazinamide, and ethambutol. We performed receiver-operating-characteristic (ROC) analysis to compare the diagnostic performance of a single 2-hour serum sample with samples obtained at 2- and 6-hours post-dosing. The sensitivity of a single 2-hour serum concentration to identify HIV/TB patients with adequate serum exposures was lowest for rifampin (54.9%, 95% CI 50.79-59.41%) and highest for ethambutol (70.8%, 95% CI 66.06-72.61%) for C_max targets. Diagnostic accuracy of a single 2-hour serum sample for the AUC_0-24 target was highest for isoniazid (93%, 95% CI 90.9-94.1%) and lowest for pyrazinamide (66.3%, 95% CI 62.6-70.0%). In summary, the diagnostic performance of TDM for C_max and AUC_0-24 targets demonstrated variability across the first-line anti-TB drugs. The addition of a 6-hour serum sample lead to the highest statistically significant improvement (p < 0.001) and highest increase in diagnostic accuracy (area under the ROC curve) for rifampin for C_max and AUC. The other first-line drugs had modest/negligible increases in diagnostic accuracy. This article is protected by copyright. All rights reserved.

Status of drug resistant tuberculosis among patients attending a tuberculosis unit of West Bengal: A record based cross-sectional study

Context

Tuberculosis (TB) is one of the main causes of death due to infectious diseases worldwide. Multidrug resistance/rifampicin resistance (MDR/RR) TB remains a public health crisis. India has the highest burden of tuberculosis and multidrug resistant TB (MDR TB) in the world. There is wide geographical variation in the epidemic and its trends that can be updated by regular reporting and sound surveillance systems. The current study tries to fill this gap by analyzing the data of TB patients from a Tuberculosis Unit, studying socio-demographic and clinical profile from December 2017 to November 2019 in Nadia district of West Bengal.

Aims

The aims of this work were to study socio-demographic and clinical profile of TB patients attending Tuberculosis Unit of West Bengal, and to find out factors associated with drug-resistant TB.

Settings and Design

Record-based study from Tuberculosis Unit.

Methods

Records of all patients who undergo CBNAAT in TU are stored as monthly unit. We randomly selected 10 months from a period of December 2017 to November 2019 by using lot method. Data of all patients undergoing CBNAAT at Kalyani - Gayeshpur Tuberculosis Unit during randomly selected 10 months were accessed.

Statistical Analysis Used

Monthly data was entered in Microsoft Excel and descriptive tests of significance, proportions and Chi-square were applied.

Results

There was male preponderance for testing of tuberculosis. Seven percent of the TB suspects were HIV positive. The positivity rate of MTB by CBNAAT was 23%. Four percent of the samples were Rifampicin resistance. Tobacco consumption, contact with TB case and Diabetes were common risk factors of TB. Most of the information was missing in the records.

Conclusions

Most of Rifampicin Resistant cases showed very low Ct value in CBNAAT. Previous history of TB treatment and positive HIV status was significantly associated with RR TB. There is a need to capture complete information on the records of presumptive TB cases.

Cathepsins and Their Endogenous Inhibitors in Host Defense During Mycobacterium tuberculosis and HIV Infection

The moment a very old bacterial pathogen met a young virus from the 80's defined the beginning of a tragic syndemic for humanity. Such is the case for the causative agent of tuberculosis and the human immunodeficiency virus (HIV). Syndemic is by definition a convergence of more than one disease resulting in magnification of their burden. Both pathogens work synergistically contributing to speed up the replication of each other. Mycobacterium tuberculosis (Mtb) and HIV infections are in the 21st century among the leaders of morbidity and mortality of humankind. There is an urgent need for development of new approaches for prevention, better diagnosis, and new therapies for both infections. Moreover, these approaches should consider Mtb and HIV as a co-infection, rather than just as separate problems, to prevent further aggravation of the HIV-TB syndemic. Both pathogens manipulate the host immune responses to establish chronic infections in intracellular niches of their host cells. This includes manipulation of host relevant antimicrobial proteases such as cathepsins or their endogenous inhibitors. Here we discuss recent understanding on how Mtb and HIV interact with cathepsins and their inhibitors in their multifactorial functions during the pathogenesis of both infections. Particularly we will address the role on pathogen transmission, during establishment of intracellular chronic niches and in granuloma clinical outcome and tuberculosis diagnosis. This area of research will open new avenues for the design of innovative therapies and diagnostic interventions so urgently needed to fight this threat to humanity.

Population Pharmacokinetics and Significant Under-Dosing of Anti-Tuberculosis Medications in People with HIV and Critical Illness

Critical illness from tuberculosis (TB) bloodstream infection results in a high case fatality rate for people living with human immunodeficiency virus (HIV). Critical illness can lead to altered pharmacokinetics and suboptimal drug exposures. We enrolled adults living with HIV and hospitalized with sepsis, with and without meningitis, in Mbarara, Uganda that were starting first-line anti-TB therapy. Serum was collected two weeks after enrollment at 1-, 2-, 4-, and 6-h post-dose and drug concentrations quantified by validated LC-MS/MS methods. Non-compartmental analyses were used to determine total drug exposure, and population pharmacokinetic modeling and simulations were performed to determine optimal dosages. Eighty-one participants were enrolled. Forty-nine completed pharmacokinetic testing: 18 (22%) died prior to testing, 13 (16%) were lost to follow-up and one had incomplete testing. Isoniazid had the lowest serum attainment, with only 4.1% achieving a target exposure over 24 h (AUC_0–24) of 52 mg·h/L despite appropriate weight-based dosing. Simulations to reach target AUC_0–24 found necessary doses of rifampin of 1800 mg, pyrazinamide of 2500–3000 mg, and for isoniazid 900 mg or higher. Given the high case fatality ratio of TB-related critical illness in this population, an early higher dose anti-TB therapy should be trialed.

Epidemiological profile of patients with rifampicin-resistant tuberculosis: an analysis of the Uganda National Tuberculosis Reference Laboratory Surveillance Data, 2014-2018

BACKGROUND

Drug-resistant tuberculosis (DR-TB), including rifampicin-resistant tuberculosis (RR-TB) and multidrug-resistant tuberculosis (MDR-TB, or RR-TB with additional isoniazid resistance), presents challenges to TB control. In Uganda, the GeneXpert test provides point-of-care testing for TB and rifampicin resistance. Patients identified with RR-TB receive culture-based drug susceptibility testing (DST) to identify additional resistance, if any. There are few data on the epidemiological profiles of current DR-TB patients in Uganda. We described patients with RR-TB in Uganda and assessed the trends of RR-TB to inform TB control interventions.

METHODS

We identified patients with RR-TB whose samples were referred for culture and DST during 2014-2018 from routinely-generated laboratory surveillance data at the Uganda National Tuberculosis Reference Laboratory. Data on patient demographics and drug sensitivity profile of Mycobacterium tuberculosis isolates were abstracted. Population data were obtained from the Uganda Bureau of Statistics to calculate incidence. Descriptive epidemiology was performed, and logistic regression used to assess trends.

RESULTS

We identified 1474 patients whose mean age was 36 ± 17 years. Overall incidence was 3.8/100,000 population. Males were more affected by RR-TB than females (4.9 vs. 2.7/100,000, p ≤ 0.01). Geographically, Northern Uganda was the most affected region (IR = 6.9/100,000) followed by the Central region (IR = 5.01/100,000). The overall population incidence of RR-TB increased by 20% over the evaluation period (OR = 1.2; 95% CI 1.15-1.23); RR-TB in new TB cases increased by 35% (OR = 1.35; 95% CI 1.3-1.4) and by 7% in previously-treated cases (OR = 1.07; 95% CI 1.0-1.1). Of the 1474 patients with RR-TB, 923 (63%) were culture-positive of whom 670 (72%) had full DST available. Based on the DST results, 522/670 (78%) had MDR-TB.

CONCLUSION

Between 2014 and 2018, the incidence of RR-TB increased especially among newly-diagnosed TB patients. We recommend intensified efforts and screening for early diagnosis especially among previously treated patients. Mechanisms should be in put to ensure that all patients with RR-TB obtain DST.

Characterization of Mycobacterium tuberculosis genotypes and their correlation to multidrug resistance in Lusaka, Zambia

OBJECTIVES

The burden of multidrug-resistant tuberculosis (MDR-TB) has been reported to be increasing in Zambia. The reasons for the increase are still unclear. This study determined the diversity of Mycobacterium tuberculosis genotypes among isolates in Lusaka, the capital city, and investigated their association with MDR-TB.

METHODS

Spoligotyping, large sequence polymorphism (LSP) analysis, and sequencing of MDR associated genes were performed on a total of 274 M. tuberculosis clinical isolates stored at the University Teaching Hospital from 2013 to 2017. Of these, 134 were MDR-TB while 126 were pan-susceptible.

RESULTS

Spoligotyping showed the LAM family as the most predominant genotype (149/274, 54.4%) followed by the CAS family (44/274, 16.1%), T family (39/274, 14.2%), and minor proportions of X, S, Harleem, EAI and Beijing spoligofamilies were identified. Three M. bovis isolates were also observed. Among those, CAS1-Kili (SIT 21) and LAM1 (SIT 20) subfamilies showed a propensity for MDR-TB with p = 0.0001 and p = 0.001, respectively.

CONCLUSIONS

This phenomenon might explain the future increase in the MDR-TB burden caused by specific lineages in Zambia. Therefore, it is recommended that the National TB control program in the country complements conventional control strategies with molecular analysis for monitoring and surveillance of MDR-TB epidemiology.

Clinical Pharmacokinetics and Pharmacodynamics of Rifampicin in Human Tuberculosis

The introduction of rifampicin (rifampin) into tuberculosis (TB) treatment five decades ago was critical for shortening the treatment duration for patients with pulmonary TB to 6 months when combined with pyrazinamide in the first 2 months. Resistance or hypersensitivity to rifampicin effectively condemns a patient to prolonged, less effective, more toxic, and expensive regimens. Because of cost and fears of toxicity, rifampicin was introduced at an oral daily dose of 600 mg (8-12 mg/kg body weight). At this dose, clinical trials in 1970s found cure rates of ≥ 95% and relapse rates of < 5%. However, recent papers report lower cure rates that might be the consequence of increased emergence of resistance. Several lines of evidence suggest that higher rifampicin doses, if tolerated and safe, could shorten treatment duration even further. We conducted a narrative review of rifampicin pharmacokinetics and pharmacodynamics in adults across a range of doses and highlight variables that influence its pharmacokinetics/pharmacodynamics. Rifampicin exposure has considerable inter- and intra-individual variability that could be reduced by administration during fasting. Several factors including malnutrition, HIV infection, diabetes mellitus, dose size, pharmacogenetic polymorphisms, hepatic cirrhosis, and substandard medicinal products alter rifampicin exposure and/or efficacy. Renal impairment has no influence on rifampicin pharmacokinetics when dosed at 600 mg. Rifampicin maximum (peak) concentration (C_max) > 8.2 μg/mL is an independent predictor of sterilizing activity and therapeutic drug monitoring at 2, 4, and 6 h post-dose may aid in optimizing dosing to achieve the recommended rifampicin concentration of ≥ 8 µg/mL. A higher rifampicin C_max is required for severe forms TB such as TB meningitis, with C_max ≥ 22 μg/mL and area under the concentration-time curve (AUC) from time zero to 6 h (AUC₆) ≥ 70 μg·h/mL associated with reduced mortality. More studies are needed to confirm whether doses achieving exposures higher than the current standard dosage could translate into faster sputum conversion, higher cure rates, lower relapse rates, and less mortality. It is encouraging that daily rifampicin doses up to 35 mg/kg were found to be safe and well-tolerated over a period of 12 weeks. High-dose rifampicin should thus be considered in future studies when constructing potentially shorter regimens. The studies should be adequately powered to determine treatment outcomes and should include surrogate markers of efficacy such as C_max/MIC (minimum inhibitory concentration) and AUC/MIC.

Treatment of Isoniazid-Resistant Pulmonary Tuberculosis

Tuberculosis (TB) remains a threat to public health and is the leading cause of death globally. Isoniazid (INH) is an important first-line agent for the treatment of TB considering its early bactericidal activity. Resistance to INH is now the most common type of resistance. Resistance to INH reduces the probability of treatment success and increases the risk of acquiring resistance to other first-line drugs such as rifampicin (RIF), thereby increasing the risk of multidrug-resistant-TB. Studies in the 1970s and 1980s showed high success rates for INH-resistant TB cases receiving regimens comprised of first-line drugs. However, recent data have indicated that INH-resistant TB patients treated with only first-line drugs have poor outcomes. Fortunately, based on recent systematic meta-analyses, the World Health Organization published consolidated guidelines on drug-resistant TB in 2019. Their key recommendations are treatment with RIF-ethambutol (EMB)-pyrazinamide (PZA)-levofloxacin (LFX) for 6 months and no addition of injectable agents to the treatment regimen. The guidelines also emphasize the importance of excluding resistance to RIF before starting RIF-EMB-PZA-LFX regimen. Additionally, when the diagnosis of INH-resistant TB is confirmed long after starting the first-line TB treatment, the clinician must decide whether to start a 6-month course of RIF-EMB-PZA-LFX based on the patient's condition. However, these recommendations are based on observational studies, not randomized controlled trials, and are thus conditional and based on low certainty of the effect estimates. Therefore, further work is needed to optimize the treatment of INH-resistant TB.

Transmission of drug-resistant tuberculosis in HIV-endemic settings

The emergence and expansion of the multidrug-resistant tuberculosis epidemic is a threat to the global control of tuberculosis. Multidrug-resistant tuberculosis is the result of the selection of resistance-conferring mutations during inadequate antituberculosis treatment. However, HIV has a profound effect on the natural history of tuberculosis, manifesting in an increased rate of disease progression, leading to increased transmission and amplification of multidrug-resistant tuberculosis. Interventions specific to HIV-endemic areas are urgently needed to block tuberculosis transmission. These interventions should include a combination of rapid molecular diagnostics and improved chemotherapy to shorten the duration of infectiousness, implementation of infection control measures, and active screening of multidrug-resistant tuberculosis contacts, with prophylactic regimens for individuals without evidence of disease. Development and improvement of the efficacy of interventions will require a greater understanding of the factors affecting the transmission of multidrug-resistant tuberculosis in HIV-endemic settings, including population-based molecular epidemiology studies. In this Series article, we review what we know about the transmission of multidrug-resistant tuberculosis in settings with high burdens of HIV and define the research priorities required to develop more effective interventions, to diminish ongoing transmission and the amplification of drug resistance.

Tuberculosis and HIV Coinfection–the Challenge in the Prevention, Detection and Treatment of Tuberculosis

Background:

Tuberculosis (TB) is still a major public health concern world-wide. The increasing global burden of TB is linked to HIV infection. HIV-TB coinfection has also conditioned clinical aspects of the TB. Since the HIV is beginning in the 1980s, the HIV infection poses a significant challenge in global TB control.

Objective:

In this review we focused on the challenges of epidemiological and clinical feature of tuberculosis presented by the HIV coinfection.

Method:

The article consists of a summary of the most important effects presented by the HIV coinfection on epidemiological and clinical feature of tuberculosis. The article analyzes and summary the causes for these challenges.

Results:

The major challenges to strategy of TB control and clinical feature of TB-HIV coinfection are presented in this paper.

Conclusion:

HIV/TB co-infection is synergic, interactive and reciprocal with significant impact. The infection of HIV and Mtb affect each other and the breakdown the immune function in TB/HIV coinfected individual. HIV infection has changed the strategy of TB control, however HIV increases global burden of TB, the reduction in the TB incidence rate is far from sufficient. Atypically clinical manifestations in TB/HIV co-infected patients and increased MDR-TB and XDR-TB contribute to the challenges in the diagnosis and treatment. Increased complexity of managing patients requires expertise in the clinical m knowledge. The focused efforts to control HIV-related TB are of great urgency. These findings will provide insight into the prevention, detection and treatment of tuberculosis and will guide advances towards tuberculosis control.

Tuberculosis treatment failure in AIDS: vengeance with renal and ocular manifestations

Tuberculosis treatment failure is not uncommon in patients with AIDS. Treatment failure is defined as a positive sputum smear or culture at month 5 or later in the course of the treatment. The clinical presentations in these patients show remarkable heterogeneity. In this report, we chronicle the case of a patient with treatment failure presenting as the disseminated disease, specifically ocular and renal tuberculosis. Additionally, we undertake here a brief literature review highlighting the increased resistance to tuberculosis treatment in patients with AIDS, the rarity of ocular tuberculosis and the importance of tailoring drug regimens on an individual basis in these coinfected patients.

High dose oral and intravenous rifampicin for improved survival from adult tuberculous meningitis: a phase II open-label randomised controlled trial (the RifT study)

Background: Tuberculous meningitis (TBM) has 44% (95%CI 35-52%) in-hospital mortality with standard therapy in Uganda. Rifampicin, the cornerstone of TB therapy, has 70% oral bioavailability and ~10-20% cerebrospinal fluid (CSF) penetration.  With current WHO-recommended TB treatment containing 8-12mg/kg rifampicin, CSF rifampicin exposures frequently fall below the minimal inhibitory concentration for M. tuberculosis. Two Indonesian phase II studies, the first investigating intravenous rifampicin 600mg and the second oral rifampicin ~30mg/kg, found the interventions were safe and resulted in significantly increased CSF rifampicin exposures and a reduction in 6-month mortality in the investigational arms. Whether such improvements can be replicated in an HIV-positive population remains to be determined. Protocol: We will perform a phase II, open-label randomised controlled trial, comparing higher-dose oral and intravenous rifampicin with current standard of care in a predominantly HIV-positive population. Participants will be allocated to one of three parallel arms (I:I:I): (i) intravenous rifampicin 20mg/kg for 2-weeks followed by oral rifampicin 35mg/kg for 6-weeks; (ii) oral rifampicin 35mg/kg for 8-weeks; (iii) standard of care, oral rifampicin 10mg/kg/day for 8-weeks. Primary endpoints will be: (i) pharmacokinetic parameters in plasma and CSF; (ii) safety. We will also examine the effect of higher-dose rifampicin on survival time, neurological outcomes and incidence of immune reconstitution inflammatory syndrome. We will enrol 60 adults with suspected TBM, from two hospitals in Uganda, with follow-up to 6 months post-enrolment. Discussion: HIV co-infection affects the bioavailability of rifampicin in the initial days of therapy, risk of drug toxicity and drug interactions, and ultimately mortality from TBM. Our study aims to demonstrate, in a predominantly HIV-positive population, the safety and pharmacokinetic superiority of one or both investigational arms compared to current standard of care. The most favourable dose may ultimately be taken forward into an adequately powered phase III trial. Trial registration: ISRCTN42218549 (24 ^th April 2018).

Suboptimal Exposure to Anti-TB Drugs in a TBM/HIV+ Population Is Not Related to Antiretroviral Therapy

A placebo-controlled trial that compares the outcomes of immediate vs. deferred initiation of antiretroviral therapy in HIV +ve tuberculous meningitis (TBM) patients was conducted in Vietnam in 2011. Here, the pharmacokinetics of rifampicin, isoniazid, pyrazinamide, and ethambutol were investigated in the presence and absence of anti-HIV treatment in 85 patients. Pharmacokinetic analyses show that HIV therapy has no significant impact on the pharmacokinetics of TB drugs in this cohort. The same population, however, displayed generally low cerebrospinal fluid (CSF) and systemic exposures to rifampicin compared to previously reported HIV -ve cohorts. Elevated CSF concentrations of pyrazinamide, on the other hand, were strongly and independently correlated with increased mortality and neurological toxicity. The findings suggest that the current standard dosing regimens may put the patient at risk of treatment failure from suboptimal rifampicin exposure, and potentially increasing the risk of adverse central nervous system events that are independently correlated with pyrazinamide CSF exposure.

Pharmacokinetics of the First-Line Antituberculosis Drugs in Ghanaian Children with Tuberculosis with or without HIV Coinfection

Although human immunodeficiency virus (HIV) coinfection is the most important risk factor for a poor antituberculosis (anti-TB) treatment response, its effect on the pharmacokinetics of the first-line drugs in children is understudied. This study examined the pharmacokinetics of the four first-line anti-TB drugs in children with TB with and without HIV coinfection. Ghanaian children with TB on isoniazid, rifampin, pyrazinamide, and ethambutol for at least 4 weeks had blood samples collected predose and at 1, 2, 4, and 8 hours postdose. Drug concentrations were determined by validated liquid chromatography-mass spectrometry methods and pharmacokinetic parameters calculated using noncompartmental analysis. The area under the concentration-time curve from 0 to 8 h (AUC0-8), maximum concentration (Cmax), and apparent oral clearance divided by bioavailability (CL/F) for each drug were compared between children with and without HIV coinfection. Of 113 participants, 59 (52.2%) had HIV coinfection. The baseline characteristics were similar except that the coinfected patients were more likely to have lower weight-for-age and height-for-age Z scores (P < 0.05). Rifampin, pyrazinamide, and ethambutol median body weight-normalized CL/F values were significantly higher, whereas the plasma AUC0-8 values were lower, in the coinfected children than in those with TB alone. In the multivariate analysis, drug dose and HIV coinfection jointly influenced the apparent oral clearance and AUC0-8 for rifampin, pyrazinamide, and ethambutol. Isoniazid pharmacokinetics were not different by HIV coinfection status. HIV coinfection was associated with lower plasma exposure of three of the four first-line anti-TB drugs in children. Whether TB/HIV-coinfected children need higher dosages of rifampin, pyrazinamide, and ethambutol requires further investigation. (This study has been registered at ClinicalTrials.gov under identifier NCT01687504.).

Impact of HIV co-infection on the evolution and transmission of multidrug-resistant tuberculosis

The tuberculosis (TB) epidemic is fueled by a parallel Human Immunodeficiency Virus (HIV) epidemic, but it remains unclear to what extent the HIV epidemic has been a driver for drug resistance in Mycobacterium tuberculosis (Mtb). Here we assess the impact of HIV co-infection on the emergence of resistance and transmission of Mtb in the largest outbreak of multidrug-resistant TB in South America to date. By combining Bayesian evolutionary analyses and the reconstruction of transmission networks utilizing a new model optimized for TB, we find that HIV co-infection does not significantly affect the transmissibility or the mutation rate of Mtb within patients and was not associated with increased emergence of resistance within patients. Our results indicate that the HIV epidemic serves as an amplifier of TB outbreaks by providing a reservoir of susceptible hosts, but that HIV co-infection is not a direct driver for the emergence and transmission of resistant strains.

Review of evidence for measuring drug concentrations of first-line antitubercular agents in adults

Measurement of drug concentrations and performing therapeutic drug monitoring (TDM) are widely used to optimize efficacy and safety of many commonly used drugs today. Although TDM of first-line antitubercular drugs is used during the treatment of tuberculosis, the extent of any benefit achieved is currently unknown. This review summarizes the available literature describing TDM of first-line treatment agents in patients with tuberculosis and describes clinical associations with achievement of target drug concentrations, including data from special populations. A literature review was conducted for articles describing drug concentration and TDM outcomes for first-line tuberculosis agents in adults. A total of 40 studies were included in the review. Studies were a mixture of controlled trials, observational studies, cross-sectional studies, and case reports. The majority of the studies showed standard dosing does not consistently achieve target concentrations for the first-line antitubercular drugs; however, the clinical implications of this finding are still unclear. Presence of HIV and diabetes mellitus appeared to indicate achievement of lower than target concentrations and this warrants further study in prospective studies. Current published data neither prove nor disprove the utility of TDM for general tuberculosis populations but evidence does not currently support routine measurement of drug concentrations.

Molecular detection and characterization of resistant genes in Mycobacterium tuberculosis complex from DNA isolated from tuberculosis patients in the Eastern Cape province South Africa

Background

Tuberculosis (TB) in both animals and humans is caused by Mycobacterium tuberculosis complex (MTBC) primarily transmitted by inhalation of aerosolized droplets containing the organism. Multi-drug resistance (MDR) and extensive drug resistance (XDR) are evolutionary features of Mycobacterium tuberculosis to subvert the antibiotic regimes in place. The heavy burden of TB worsened by HIV endemic in South Africa motivated for the investigation of MTBC prevalence among TB patients in Port Elizabeth and the amplification and sequencing of the DNA amplicons known to confer resistance to TB drugs.

Methods

Three thousand eight hundred and ten (3810) sputum specimens were processed and DNA was isolated from sputum specimens collected from different hospitals and health care places in the Eastern Cape Province, South Africa. DNA was amplified using the Seeplex^® MTB Nested ACE detection assay. The agar-dilution proportion method was used to perform drug-sensitivity testing using 7H10 Middlebrook medium. Target genes known to confer resistance to first and second-line drugs were amplified and the amplicons sequenced.

Results

One hundred and ninety (5%) DNA samples tested positive for MTBC and from the resistant profiles of the 190 positive samples, we noted that multidrug-resistant TB was identified in 189 (99.5%) with 190 (100%) patients infected with MTB resistant to isoniazid and 189 (99.5%) having MTB resistant to rifampicin. Other percentages of drug resistance observed including 40% pre-XDR and 60% of XDR.

Conclusion

This study provides valuable data on the different kinds of mutations occurring at various target loci in resistant MTBC strains isolated from samples obtained from the Eastern Cape Province. The results obtained reveal a high incidence of MDR amongst the positive samples from Eastern Cape Province, South Africa.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2334-14-479) contains supplementary material, which is available to authorized users.

HIV-Mycobacterium tuberculosis co-infection: a 'danger-couple model' of disease pathogenesis

Tuberculosis (TB) and human immunodeficiency virus (HIV) infection interfere and impact the pathogenesis phenomena of each other. Owing to atypical clinical presentations and diagnostic complications, HIV/TB co-infection continues to be a menace for healthcare providers. Although the increased access to highly active antiretroviral therapy (HAART) has led to a reduction in HIV-associated opportunistic infections and mortality, the concurrent management of HIV/TB co-infection remains a challenge owing to adverse effects, complex drug interactions, overlapping toxicities and tuberculosis -associated immune reconstitution inflammatory syndrome. Several hypotheses have been put forward for the exacerbation of tuberculosis by HIV and vice versa supported by immunological studies. Discussion on the mechanisms produced by infectious cofactors with impact on disease pathology could shed light on how to design potential interventions that could decelerate disease progression. With no vaccine for HIV and lack of an effective vaccine for tuberculosis, it is essential to design strategies against HIV-TB co-infection.

Drug Resistance among Pulmonary Tuberculosis Patients in Calabar, Nigeria

Background. This study aimed to determine the pattern of drug susceptibility to first-line drugs among pulmonary TB patients in two hospitals in Calabar, Nigeria. Methods. This was a descriptive cross-sectional study carried out between February 2011 and April 2012. Sputum samples from consecutive TB patients in Calabar were subjected to culture on Lowenstein-Jensen (LJ) slopes followed by drug susceptibility testing (DST). The DST was performed on LJ medium by the proportion method. Results. Forty-two of the 100 Mycobacterium tuberculosis strains were found to be resistant to at least one drug. Resistance to only one drug (monoresistance) was found in 17 patients. No strains with monoresistance to rifampicin were found. Resistance to two drugs was found in 22 patients, while one patient was resistant to both three and four drugs. MDR TB was seen in 4% (4/100). The independent variables of HIV serology and sex were not significantly associated with resistance (P > 0.05). Conclusion. There was a high prevalence of anti-TB drug resistance in Calabar.

Anti-tuberculosis drug resistance among new and previously treated sputum smear-positive tuberculosis patients in Uganda: results of the first national survey

BACKGROUND

Multidrug resistant and extensively drug resistant tuberculosis (TB) have become major threats to control of tuberculosis globally. The rates of anti-TB drug resistance in Uganda are not known. We conducted a national drug resistance survey to investigate the levels and patterns of resistance to first and second line anti-TB drugs among new and previously treated sputum smear-positive TB cases.

METHODS

Sputum samples were collected from a nationally representative sample of new and previously treated sputum smear-positive TB patients registered at TB diagnostic centers during December 2009 to February 2011 using a weighted cluster sampling method. Culture and drug susceptibility testing was performed at the national TB reference laboratory.

RESULTS

A total of 1537 patients (1397 new and 140 previously treated) were enrolled in the survey from 44 health facilities. HIV test result and complete drug susceptibility testing (DST) results were available for 1524 (96.8%) and 1325 (85.9%) patients, respectively. Of the 1209 isolates from new cases, resistance to any anti-TB drug was 10.3%, 5% were resistant to isoniazid, 1.9% to rifampicin, and 1.4% were multi drug resistant. Among the 116 isolates from previously treated cases, the prevalence of resistance was 25.9%, 23.3%, 12.1% and 12.1% respectively. Of the 1524 patients who had HIV testing 469 (30.7%) tested positive. There was no association between anti-TB drug resistance (including MDR) and HIV infection.

CONCLUSION

The prevalence of anti-TB drug resistance among new patients in Uganda is low relative to WHO estimates. The higher levels of MDR-TB (12.1%) and resistance to any drug (25.3%) among previously treated patients raises concerns about the quality of directly observed therapy (DOT) and adherence to treatment. This calls for strengthening existing TB control measures, especially DOT, routine DST among the previously treated TB patients or periodic drug resistance surveys, to prevent and monitor development and transmission of drug resistant TB.

Characteristics of multidrug-resistant tuberculosis in Namibia

Background

To describe the epidemiology and possible risk factors for the development of multidrug-resistant tuberculosis (MDR-TB) in Namibia.

Methods

Using medical records and patient questionnaires, we conducted a case-control study among patients diagnosed with TB between January 2007 and March 2009. Cases were defined as patients with laboratory-confirmed MDR-TB; controls had laboratory-confirmed drug-susceptible TB or were being treated with WHO Category I or Category II treatment regimens.

Results

We enrolled 117 MDR-TB cases and 251 TB controls, of which 100% and 2% were laboratory-confirmed, respectively. Among cases, 97% (113/117) had been treated for TB before the current episode compared with 46% (115/251) of controls (odds ratio [OR] 28.7, 95% confidence interval [CI] 10.3–80.5). Cases were significantly more likely to have been previously hospitalized (OR 1.9, 95% CI 1.1–3.5) and to have had a household member with MDR-TB (OR 5.1, 95% CI 2.1–12.5). These associations remained significant when separately controlled for being currently hospitalized or HIV-infection.

Conclusions

MDR-TB was associated with previous treatment for TB, previous hospitalization, and having had a household member with MDR-TB, suggesting that TB control practices have been inadequate. Strengthening basic TB control practices, including expanding laboratory confirmation, directly observed therapy, and infection control, are critical to the prevention of MDR-TB.

High prevalence of multidrug-resistant tuberculosis, Swaziland, 2009-2010

One third of previously treated patients had MDR TB.

In Africa, although emergence of multidrug-resistant (MDR) tuberculosis (TB) represents a serious threat in countries severely affected by the HIV epidemic, most countries lack drug-resistant TB data. This finding was particularly true in the Kingdom of Swaziland, which has the world’s highest HIV and TB prevalences. Therefore, we conducted a national survey in 2009–2010 to measure prevalence of drug-resistant TB. Of 988 patients screened, 420 new case-patients and 420 previously treated case-patients met the study criteria. Among culture-positive patients, 15.3% new case-patients and 49.5% previously treated case-patients harbored drug-resistant strains. MDR TB prevalence was 7.7% and 33.8% among new case-patients and previously treated case-patients, respectively. HIV infection and past TB treatment were independently associated with MDR TB. The findings assert the need for wide-scale intervention in resource-limited contexts such as Swaziland, where diagnostic and treatment facilities and health personnel are lacking.

Reduced antituberculosis drug concentrations in HIV-infected patients who are men or have low weight: implications for international dosing guidelines

Reduced antituberculosis drug concentrations may contribute to unfavorable treatment outcomes among HIV-infected patients with more advanced immune suppression, and few studies have evaluated pharmacokinetics of the first-line antituberculosis drugs in such patients given fixed-dose combination tablets according to international guidelines using weight bands. In this study, pharmacokinetics were evaluated in 60 patients on 4 occasions during the first month of antituberculosis therapy. Multilevel linear mixed-effects regression analysis was used to examine the effects of age, sex, weight, drug dose/kilogram, CD4(+) lymphocyte count, treatment schedule (5 versus 7 days/week), and concurrent antiretrovirals (efavirenz plus lamivudine plus zidovudine) on the area under the concentration-time curve from 0 to 12 h (AUC(0-12)) of the respective antituberculosis drugs and to compare AUC(0-12)s at day 8, day 15, and day 29 with the day 1 AUC(0-12). Median (range) age, weight, and CD4(+) lymphocyte count were 32 (18 to 47) years, 55.2 (34.4 to 98.7) kg, and 252 (12 to 500)/μl. For every 10-kg increase in body weight, the predicted day 29 AUC(0-12) increased by 14.1% (95% confidence interval [CI], 7.5, 20.8), 14.1% (95% CI, -0.7, 31.1), 6.1% (95% CI, 2.7, 9.6) and 6.0% (95% CI, 0.8, 11.3) for rifampin, isoniazid, pyrazinamide, and ethambutol, respectively. Males had day 29 AUC(0-12)s 19.3% (95% CI, 3.6, 35.1) and 14.0% (95% CI, 5.6, 22.4) lower than females for rifampin and pyrazinamide, respectively. Level of immune suppression and concomitant antiretrovirals had little effect on the concentrations of the antituberculosis agents. As they had reduced drug concentrations, it is important to review treatment responses in patients in the lower weight bands and males to inform future treatment guidelines, and revision of doses in these patients should be considered.

Pharmacokinetics of rifampin in Peruvian tuberculosis patients with and without comorbid diabetes or HIV

For drug-compliant patients, poor responses to tuberculosis (TB) treatment might be attributable to subtherapeutic drug concentrations. An impaired absorption of rifampin was previously reported for patients with diabetes mellitus (DM) or HIV. The objectives of this study were to determine whether TB drug pharmacokinetics differed in Peruvian TB patients with DM or HIV. In this cross-sectional study, TB patients, recruited from health centers in Lima, Peru, had blood samples taken at 2 and 6 h after directly observed TB drug ingestion, to determine plasma concentrations of rifampin. Of 105 patients, 50 had TB without a comorbidity, 26 had coexistent DM, and 29 had coexistent HIV. Unexpectedly, the overall median 2- and 6-h levels of rifampin were 1.6 and 3.2 mg/liter, respectively, and the time to the peak concentration was 6 h (slow absorber) instead of 2 h (fast absorber) for 61 patients (62.2%). The geometric mean peak concentration of drug in serum (C(max)) was significantly higher in fast absorbers than in slow absorbers (5.0 versus 3.8 mg/liter; P = 0.05). The rifampin C(max) was significantly lower in male patients than in female patients (3.3 versus 6.3 mg/liter; P < 0.001). Neither slow nor fast absorbers with comorbidities (DM or HIV) had significantly different C(max) results compared to those of TB patients without comorbidities. An analysis of variance regression analysis showed that female gender (P < 0.001) and the time to maximum concentration of drug in serum (T(max)) at 2 h (P = 0.012) were independently correlated with increased exposure to rifampin. Most of this Peruvian study population exhibited rifampin pharmacokinetics different from those conventionally reported, with delayed absorption and low plasma concentrations, independent of the presence of an HIV or DM comorbidity.

Systemic exposure to rifampicin in patients with tuberculosis and advanced HIV disease during highly active antiretroviral therapy in Burkina Faso

OBJECTIVES

Low plasma concentrations of rifampicin, an essential antituberculosis drug, have been reported particularly among HIV co-infected persons. In a prospective, longitudinal study we measured rifampicin systemic exposure at different timepoints during highly active antiretroviral therapy (HAART).

PATIENTS AND METHODS

From May 2006 to April 2007, 16 tuberculosis (TB)/HIV co-infected patients were enrolled in Ouagadougou, Burkina Faso. All patients received fixed dose combinations of rifampicin, isoniazid, pyrazinamide and ethambutol under direct observation and HAART, consisting of a fixed dose combination of stavudine, lamivudine and nevirapine. Rifampicin concentrations during the dosing interval were determined by HPLC at three different timepoints: (i) after 2 weeks of TB therapy and before starting HIV therapy (T0); (ii) after 4 weeks of combined therapy (T1); and (iii) after 10 weeks of combined therapy (T2).

RESULTS

The median values of the area under the curve (AUC(0-24)) of rifampicin increased by 39% at T1 (15.69 μg · h/mL; P = 0.01) and by 83% at T2 (20.65 μg · h/mL; P = 0.001) compared with T0 (11.28 μg · h/mL). Similar variations were observed for the median C(max) at T0 (2.24 μg/mL) compared with T2 (2.83 μg/mL; P = 0.003). However, none of the subjects had C(max) levels >8 μg/mL at either T0 or T2.

CONCLUSIONS

Rifampicin systemic exposure increased during combined TB and HIV therapy, possibly due to increased drug absorption or decreased oral clearance, but remained invariably low in this population. Studies to define the C(max) rifampicin concentrations, which are associated with a significantly increased risk of treatment failure, are urgently warranted.

Therapeutic drug monitoring for slow response to tuberculosis treatment in a state control program, Virginia, USA

TOC summary: Diabetes was associated with increased risk for slow response and low rifampin levels.

Therapeutic drug monitoring may be useful in tuberculosis management, but programmatic implementation is understudied. We performed a retrospective cohort study to determine prevalence of lower than expected levels of isoniazid, rifampin, ethambutol, and pyrazinamide measured at time of estimated peak serum concentration. Patients were tested for serum concentration at 2 hours after medication administration. When patients were tested, 22 had concentrations lower than expected range for rifampin, 23 of 39 patients had low levels of isoniazid, and 8 of 26 patients had low levels of ethambutol; all 20 patients tested for pyrazinamide were within expected range. Over 26 months, 42 patients met criteria for slow response. Diabetes was associated with slow response (p<0.001), and persons with diabetes were more likely than persons without diabetes to have low rifampin levels (p = 0.03). Dosage adjustment of rifampin was more likely to elevate serum concentration to the target range than adjustment of isoniazid given in daily doses (p = 0.01).

Predictors of multidrug- and extensively drug-resistant tuberculosis in a high HIV prevalence community

Background

Multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) have emerged in high-HIV-prevalence settings, which generally lack laboratory infrastructure for diagnosing TB drug resistance. Even where available, inherent delays with current drug-susceptibility testing (DST) methods result in clinical deterioration and ongoing transmission of MDR and XDR-TB. Identifying clinical predictors of drug resistance may aid in risk stratification for earlier treatment and infection control.

Methods

We performed a retrospective case-control study of patients with MDR (cases), XDR (cases) and drug-susceptible (controls) TB in a high-HIV-prevalence setting in South Africa to identify clinical and demographic risk factors for drug-resistant TB. Controls were selected in a 1∶1∶1 ratio and were not matched. We calculated odds ratios (OR) and performed multivariate logistic regression to identify independent predictors.

Results

We enrolled 116, 123 and 139 patients with drug-susceptible, MDR, and XDR-TB. More than 85% in all three patient groups were HIV-infected. In multivariate analysis, MDR and XDR-TB were each strongly associated with history of TB treatment failure (adjusted OR 51.7 [CI 6.6-403.7] and 51.5 [CI 6.4–414.0], respectively) and hospitalization more than 14 days (aOR 3.8 [CI 1.1–13.3] and 6.1 [CI 1.8–21.0], respectively). Prior default from TB treatment was not a risk factor for MDR or XDR-TB. HIV was a risk factor for XDR (aOR 8.2, CI 1.3–52.6), but not MDR-TB. Comparing XDR with MDR-TB patients, the only significant risk factor for XDR-TB was HIV infection (aOR 5.3, CI 1.0–27.6).

Discussion

In this high-HIV-prevalence and drug-resistant TB setting, a history of prolonged hospitalization and previous TB treatment failure were strong risk factors for both MDR and XDR-TB. Given high mortality observed among patients with HIV and drug-resistant TB co-infection, previously treated and hospitalized patients should be considered for empiric second-line TB therapy while awaiting confirmatory DST results in settings with a high-burden of MDR/XDR-TB.

Malabsorption of antimycobacterial drugs as a cause of treatment failure in tuberculosis

Malabsorption of oral antimycobacterial drugs is a rare cause of treatment failure in tuberculosis (TB). Several predisposing comorbidities have been recognised. HIV infection is the most important risk factor referred in the literature. There are few reports about antimycobacterial drugs malabsorption, particularly in the absence of predisposing comorbidities. The authors present a clinical case of oral treatment failure in TB due to malabsorption; however, what caused the failure remained unclear. Possible causes of malabsorption are discussed under various sections. Purpose of this case report is to point to this rare situation that can easily go unnoticed unless a very high level of suspicion is present.

Mortality among patients with tuberculosis requiring intensive care: a retrospective cohort study

Background

To describe the characteristics of patients with tuberculosis (TB) requiring intensive care and to identify the factors that predicts in-hospital mortality in a city of a developing country with intermediate-to-high TB endemicity.

Methods

We conducted a retrospective, cohort study, between November 2005 and November 2007. The patients with TB requiring intensive care were included. Predictors of mortality were assessed. The primary outcome was the in-hospital mortality.

Results

During the study period, 67 patients with TB required intensive care. Of them, 62 (92.5%) had acute respiratory failure and required mechanical ventilation. Forty-four (65.7%) patients died. Coinfection with human immunodeficiency virus was present in 46 (68.7%) patients. Early intensive care unit admission and ventilator-associated pneumonia were independently associated with the in-hospital mortality.

Conclusions

In this study we found a high mortality rate in TB patients requiring intensive care, especially in those with an early ICU admission.

The potential to transmit Mycobacterium tuberculosis at a South African tertiary teaching hospital

OBJECTIVES

To assess the risk of nosocomial transmission by confirmed pulmonary tuberculosis (PTB) patients in a high TB/HIV incidence environment.

METHODS

Between November 2006 and April 2007, we carried out a cross-sectional survey of PTB patients with positive smears or cultures at an academic tertiary hospital in the Western Cape, South Africa.

RESULTS

Of 394 confirmed PTB patients, only 199 (50.5%) had a known HIV status, of whom 107 (53.8%) were HIV-co-infected. Sensitivity testing for Mycobacterium tuberculosis (TB) was done in 49.3% of patients with available cultures (140/284). Of these patients, 9.3% (13/140) had multidrug-resistant (MDR) TB strains. The turnaround times (TAT) for culture and susceptibility testing were delayed: mean TAT for cultures was 27 days (range 63 days) and for susceptibility testing was 42 days (range 63 days). One fifth of PTB patients (82/394) were diagnosed from wards that do not deal with TB on a daily basis. PTB inpatients were hospitalized for an average of 13 days and were on average transferred twice. Only 14.2% of all PTB patients were notified to the South Africa Provincial Department of Health. Throughout their hospitalization, PTB patients were potentially infectious.

CONCLUSIONS

The potential for nosocomial TB transmission in a setting of high TB and HIV co-infection with a high MDR prevalence, inconsistent infection prevention and control measures, and delayed diagnosis cannot be ignored. Barriers to TB infection control must urgently be addressed.

Isoniazid, rifampin, ethambutol, and pyrazinamide pharmacokinetics and treatment outcomes among a predominantly HIV-infected cohort of adults with tuberculosis from Botswana

BACKGROUND

We explored the association between antituberculosis drug pharmacokinetics and treatment outcomes among patients with pulmonary tuberculosis in Botswana.

METHODS

Consenting outpatients with tuberculosis had blood samples collected 1, 2, and 6 h after simultaneous isoniazid, rifampin, ethambutol, and pyrazinamide ingestion. Maximum serum concentrations (C(max)) and areas under the serum concentration time curve were determined. Clinical status was monitored throughout treatment.

RESULTS

Of the 225 participants, 36 (16%) experienced poor treatment outcome (treatment failure or death); 155 (69%) were infected with human immunodeficiency virus (HIV). Compared with published standards, low isoniazid C(max) occurred in 84 patients (37%), low rifampin C(max) in 188 (84%), low ethambutol C(max) in 87 (39%), and low pyrazinamide C(max) in 11 (5%). Median rifampin and pyrazinamide levels differed significantly by HIV status and CD4 cell count category. Only pyrazinamide pharmacokinetics were significantly associated with treatment outcome; low pyrazinamide C(max) was associated with a higher risk of documented poor treatment outcome, compared with normal C(max) (50% vs. 16%; P < .01). HIV-infected patients with a CD4 cell count <200 cells/microL had a higher risk of poor treatment outcome (27%) than did HIV-uninfected patients (11%) or HIV-infected patients with a CD4 cell count 200 cells/microL (12%; P = .01). After adjustment for HIV infection and CD4 cell count, patients with low pyrazinamide C(max) were 3 times more likely than patients with normal pyrazinamide C(max) to have poor outcomes (adjusted risk ratio, 3.38; 95% confidence interval, 1.84-6.22).

CONCLUSIONS

Lower than expected antituberculosis drug C(max) occurred frequently, and low pyrazinamide C(max) was associated with poor treatment outcome. Exploring the global prevalence and significance of these findings may suggest modifications in treatment regimens that could improve tuberculosis cure rates.

Therapeutic drug monitoring of antimycobacterial drugs in patients with both tuberculosis and advanced human immunodeficiency virus infection

STUDY OBJECTIVE

To determine the feasibility of therapeutic drug monitoring for adjusting low serum antimycobacterial concentrations in patients with both tuberculosis and advanced human immunodeficiency virus (HIV).

DESIGN

Retrospective cohort study.

DATA SOURCE

De-identified dataset from a tuberculosis clinic.

PATIENTS

Twenty-one patients (median age 38 yrs, range 25-68 yrs) with advanced HIV infection (CD4(+) cell count < 100 cells/mm(3)) who received treatment for active tuberculosis between March 2002 and September 2007.

MEASUREMENTS AND MAIN RESULTS

We evaluated data based on the practices performed at the tuberculosis clinic. After the daily doses of isoniazid and rifamycins (rifampin or rifabutin) were ingested, serum concentrations were obtained at 2 hours for isoniazid and rifampin, at 3 hours for rifabutin, and, when possible, at 6 hours for all three drugs to detect delayed absorption. Antimycobacterial drug concentrations were compared with published reference levels, and dosages were adjusted to achieve desired concentrations. Costs of monitoring were recorded for all patients. Of the 21 patients, 18 (86%) had low serum concentrations of at least one drug 2 hours after ingestion: 2 (10%) had low isoniazid concentrations, 5 (24%) had low rifamycin concentrations, and 11 (52%) had low serum concentrations of both drugs. The median number of dosage adjustments to attain normal concentrations was 1 (range 0-4 adjustments). The median cost/patient for therapeutic drug monitoring was $619 (range $230-1948). The median final doses to achieve normal concentrations were isoniazid 600 mg/day (range 300-1500 mg/day), rifampin 1050 mg/day (range 600-1200 mg/day), and rifabutin 300 mg (range 150-450 mg) 3 times/week. No patient demonstrated any adverse effects attributed to these higher doses.

CONCLUSION

Low serum concentrations of antituberculous drugs, which suggest malabsorption, are common among patients with advanced HIV who also have tuberculosis but can be overcome with higher doses. Therapeutic drug monitoring may be an effective tool to optimize therapy, but needs further study.

Is HIV infection a risk factor for multi-drug resistant tuberculosis? A systematic review

Background

Tuberculosis (TB) is an important cause of human suffering and death. Human immunodeficiency virus (HIV), multi-drug resistant TB (MDR-TB), and extensive drug resistant tuberculosis (XDR-TB) have emerged as threats to TB control. The association between MDR-TB and HIV infection has not yet been fully investigated. We conducted a systematic review and meta-analysis to summarize the evidence on the association between HIV infection and MDR-TB.

Methods and Results

Original studies providing Mycobacterium tuberculosis resistance data stratified by HIV status were identified using MEDLINE and ISI Web of Science. Crude MDR-TB prevalence ratios were calculated and analyzed by type of TB (primary or acquired), region and study period. Heterogeneity across studies was assessed, and pooled prevalence ratios were generated if appropriate. No clear association was found between MDR-TB and HIV infection across time and geographic locations. MDR-TB prevalence ratios in the 32 eligible studies, comparing MDR-TB prevalence by HIV status, ranged from 0.21 to 41.45. Assessment by geographical region or study period did not reveal noticeable patterns. The summary prevalence ratios for acquired and primary MDR-TB were 1.17 (95% CI 0.86, 1.6) and 2.72 (95% CI 2.03, 3.66), respectively. Studies eligible for review were few considering the size of the epidemics. Most studies were not adjusted for confounders and the heterogeneity across studies precluded the calculation of a meaningful overall summary measure.

Conclusions

We could not demonstrate an overall association between MDR-TB and HIV or acquired MDR-TB and HIV, but our results suggest that HIV infection is associated with primary MDR-TB. Future well-designed studies and surveillance in all regions of the world are needed to better clarify the relationship between HIV infection and MDR-TB.

Population pharmacokinetics of rifampin in pulmonary tuberculosis patients, including a semimechanistic model to describe variable absorption

This article describes the population pharmacokinetics of rifampin in South African pulmonary tuberculosis patients. Three datasets containing 2,913 rifampin plasma concentration-time data points, collected from 261 South African pulmonary tuberculosis patients aged 18 to 72 years and weighing 28.5 to 85.5 kg and receiving regular daily treatment that included administration of rifampin (450 to 600 mg) for at least 10 days, were pooled. A compartmental pharmacokinetic model was developed using nonlinear mixed-effects modeling. Variability in the shape of the absorption curve was described using a flexible transit compartment model, in which a delay in the onset of absorption and a gradually changing absorption rate were modeled as the passage of drug through a chain of hypothetical compartments, ultimately reaching the absorption compartment. A previously described implementation was extended to allow its application to multiple-dosing data. The typical population estimate of oral clearance was 19.2 liters x h(-1), while the volume of distribution was estimated to be 53.2 liters. Interindividual variability was estimated to be 52.8% for clearance and 43.4% for volume of distribution. Interoccasional variability was estimated for CL/F (22.5%) and mean transit time during absorption (67.9%). The use of single-drug formulations was found to increase both the mean transit time (by 104%) and clearance (by 23.6%) relative to fixed-dose-combination use. A strong correlation between clearance and volume of distribution suggested substantial variability in bioavailability, which could have clinical implications, given the dependence of treatment effectiveness on exposure. The final model successfully described rifampin pharmacokinetics in the population studied and is suitable for simulation in this context.

Correlates for disease progression and prognosis during concurrent HIV/TB infection

Mycobacterium tuberculosis (Mtb) and the human immunodeficiency virus (HIV) are both life-threatening pathogens in their own right, but their synergic effects on the immune system during co-infection markedly enhance their effect on the host. This review focuses on the bidirectional interaction between HIV and Mtb and discusses the relevance of sputum smear examination, CD4+ counts, viral load at baseline and after initiation of anti-retroviral therapy, as well as additional existing and new potential immune correlates of disease progression and prognosis. These markers include beta2-microglobulin, neopterin, tumor necrosis factor receptor II (TNFRII), CD8+/CD38+, soluble urokinase plasminogen activator receptor (suPAR) and CXCL10 (or IP-10).

Determinants of rifampin, isoniazid, pyrazinamide, and ethambutol pharmacokinetics in a cohort of tuberculosis patients

Evaluation of sources of pharmacokinetic variation can facilitate optimization of tuberculosis treatment regimens by identification of avoidable sources of variation and of risk factors for low or high drug concentrations in patients. Our objective was to describe the pharmacokinetics of rifampin, isoniazid, pyrazinamide, and ethambutol in a cohort of tuberculosis patients established on first-line treatment regimens and to evaluate the determinants of pharmacokinetic variation. Plasma concentration-time profiles were determined for each of the drugs in 142 patients with drug-sensitive pulmonary tuberculosis after 2 months of daily treatment in hospital. Pharmacokinetic measures were described by noncompartmental analysis. Multiple linear regression was used to evaluate the patient and the treatment factors associated with variation of the area under the concentration-time curve from 0 to 8 h. Several factors independently associated with variations in antituberculosis drug concentrations were identified: human immunodeficiency virus infection was associated with 39% and 27% reductions for rifampin and ethambutol, respectively; formulation factors were determinants of rifampin and isoniazid bioavailability; female patients had increased rifampin and isoniazid concentrations but reduced ethambutol concentrations; older patients had higher levels of isoniazid and ethambutol; patients with a history of previous antituberculosis treatment had lower ethambutol concentrations; and the dose per kilogram of body weight was associated with the concentrations of all four agents. Further studies are required to assess the implications of variations in antituberculosis drug concentrations for efficacy and safety before decisions are made to change the dosing strategy in patients at risk.

The clinical pharmacokinetics of rifampin and ethambutol in HIV-infected persons with tuberculosis

BACKGROUND

The pharmacokinetics of rifampin and ethambutol in HIV-infected patients with tuberculosis (TB) are incompletely characterized. We examined the pharmacokinetics of rifampin and ethambutol in a cohort of patients with HIV-related TB who were treated in the United States.

METHODS

Serum drug concentrations were determined 2, 6, and 10 h after dosing in 36 HIV-infected patients with TB who were taking rifampin and in 49 who were taking ethambutol. Observed serum concentrations were compared with published normal ranges and published data.

RESULTS

With daily dosing of rifampin (600 mg), 26 (77%) of 34 patients (95% confidence interval [CI], 59%-89%]) had a low maximum concentration of rifampin (<8 microg/mL), and 12 (35%; 95% CI, 20%-54%) had a very low maximum concentration (<4 microg/mL). With intermittent rifampin dosing (600 mg), 13 (68%) of 19 patients (95% CI, 44%-85%) had a low maximum concentration of rifampin, and 5 (26%; 95% CI, 11%-50%) had a very low maximum concentration. With daily ethambutol dosing (20 mg/kg), 33 (69%) of 48 patients (95% CI, 55%-81%) had a low maximum concentration of ethambutol (<2 microg/mL), and 18 (38%; 95% CI, 24%-53%) had a very low maximum concentration (<1 microg/mL). With intermittent ethambutol dosing (50 mg/kg twice weekly or 30 mg/kg thrice weekly), 13 (72%) of 18 patients (95% CI, 47%-88%) had a low maximum concentration of ethambutol (<4 microg/mL), and 5 (28%; 95% CI, 12%-54%]) had a very low maximum concentration (<2 microg/mL).

CONCLUSIONS

In HIV-infected patients with TB who are receiving rifampin and ethambutol, low maximum concentrations of rifampin and ethambutol were common. For patients with HIV-related TB, therapeutic monitoring of rifampin and ethambutol levels may help clinicians achieve target serum concentrations.

Serum concentrations of antimycobacterial drugs in patients with pulmonary tuberculosis in Botswana

BACKGROUND

We conducted a pharmacokinetic study of antimycobacterial drugs involving a cohort of patients with pulmonary tuberculosis (TB) in Gaborone, Botswana, to assess the prevalence of and risk factors for low drug concentrations in serum.

METHODS

Adults participated if they had a history of cough > or =2 weeks, had abnormal chest radiograph findings, consented to testing for human immunodeficiency virus (HIV), had sputum cultures positive for Mycobacterium tuberculosis, and were receiving antituberculous therapy for >7 days. Observed maximum serum concentrations were compared with published normal ranges. RESULTS. Of 91 patients enrolled, 89 (98%) were outpatients, and 59 (68%) of 87 patients tested had HIV infection. The following numbers of patients had low serum concentrations of the following drugs: isoniazid, 27 (30%) of 90; rifampin, 71 (78%) of 91; ethambutol, 37 (41%) of 91; and pyrazinamide, 1 (1%) of 91. Low serum concentrations of both isoniazid and rifampin occurred in 23 (26%) of 90 patients. Low serum concentrations of rifampin were found in both HIV-infected and non-HIV-infected patients, and such patients were less likely to have >4 weeks of symptoms, more likely to have lymphadenopathy, and more likely to have low serum albumin levels (P<.05 for all). The associations with noncavitary pulmonary disease (P=.12) and HIV infection (P=.07) did not reach statistical significance. Delayed absorption was most common with ethambutol, followed by rifampin.

CONCLUSIONS

These data, predominantly from HIV-infected patients with TB, suggest that low isoniazid, rifampin, and ethambutol concentrations are common in Botswana. In contrast, pyrazinamide usually is well absorbed.

Decreased bioavailability of rifampin and other antituberculosis drugs in patients with advanced human immunodeficiency virus disease

We evaluated the effects of human immunodeficiency virus (HIV) disease on pharmacokinetics of antituberculosis medications by measuring concentrations of isoniazid and rifampin in blood and of pyrazinamide and ethambutol in urine. Peak concentration and exposure were reduced for rifampin, and rapid acetylators of isoniazid had lower drug levels. HIV and HIV-tuberculosis patients who have diarrhea and cryptosporidial infection exhibit decreased bioavailability of antituberculosis drugs.

Tuberculosis in HIV-infected patients: a comprehensive review

The incidence of tuberculosis (TB) is currently increasing in HIV-infected patients living in Africa and Asia, where TB endemicity is high, reflecting the susceptibility of this group of patients to mycobacteria belonging to the TB group. In this population, extension of multiple resistance to anti-tuberculous drugs is also a matter of anxiety. HIV-induced immunosuppression modifies the clinical presentation of TB, resulting in atypical signs and symptoms, and more frequent extrapulmonary dissemination. The treatment of TB is also more difficult to manage in HIV-infected patients, particularly with regard to pharmacological interactions secondary to inhibition or induction of cytochrome P450 enzymes by protease inhibitors with rifampicin or rifabutin, respectively. Finally, immune restoration induced by highly active anti-retroviral therapy (HAART) in developed countries may be responsible for a paradoxical worsening of TB manifestations.

The Clinical Pharmacokinetics of Pyrazinamide in HIV‐Infected Persons with Tuberculosis

The pharmacokinetics of pyrazinamide (PZA) in patients with human immunodeficiency virus (HIV)-related tuberculosis are incompletely characterized. Serum PZA concentrations were determined at 2, 6, and 10 h after dosing in 48 subjects with HIV-related tuberculosis. Estimates of drug exposure using 2-h concentrations and 2- and 3-time point estimates of area under time-concentration curves (AUCs) were compared. For daily dosing, 2-h concentrations less than low and very low literature-defined cut points (i.e., 20 and 10 mg/L) were noted for 2 subjects (4%) and 1 subject (2%), respectively. For intermittent PZA dosing, 1 subject (4%) had a 2-h concentration that was less than the low cut point (25 mg/L). Correlations between 2-h concentration and AUC estimates based on 2- or 3-time point concentration determinations were strong. In HIV-infected persons receiving antituberculosis regimens containing PZA, lower-than-expected 2-h concentrations are uncommon. For therapeutic monitoring of PZA drug exposure, determination of a 2-h postdose concentration appears as reliable as 2- or 3-time point estimates of the AUC for PZA.

Malabsorption of rifampin and isoniazid in HIV-infected patients with and without tuberculosis

The absorption of rifampin, isoniazid, and D-xylose in patients with human immunodeficiency virus (HIV) infection and diarrhea, in patients with HIV infection and tuberculosis (TB), in patients with pulmonary TB alone, and in healthy subjects was studied. Percentage of dose of the drugs, their metabolites, and D-xylose excreted in urine were calculated. A significant reduction in the absorption of drugs and D-xylose in both the HIV infection/diarrhea and HIV infection/TB groups was observed (P<.05), and the correlation between them was significant. Our results indicate that patients with HIV infection and diarrhea and those with HIV infection and TB have malabsorption of rifampin and isoniazid.