Diagnostic Accuracy and Optimal Use of Three Tests for Tuberculosis in Live Badgers

Background

Accurate diagnosis of tuberculosis (TB) due to infection with Mycobacterium bovis is notoriously difficult in live animals, yet important if we are to understand the epidemiology of TB and devise effective strategies to limit its spread. Currently available tests for diagnosing TB in live Eurasian badgers (Meles meles) remain unvalidated against a reliable gold standard. The aim of the present study was to evaluate the diagnostic accuracy and optimal use of three tests for TB in badgers in the absence of a gold standard.

Methodology/Principal Findings

A Bayesian approach was used to evaluate the diagnostic accuracy and optimal use of mycobacterial culture, gamma-interferon assay and a commercially available serological test using multiple samples collected from 305 live wild badgers. Although no single test was judged to be sufficiently sensitive and specific to be used as a sole diagnostic method, selective combined use of the three tests allowed guidelines to be formulated that allow a diagnosis to be made for individual animals with an estimated overall accuracy of 93% (range: 75% to 97%). Employing this approach in the study population of badgers resulted in approximately 13 out of 14 animals having their true infection status correctly classified from samples collected on a single capture.

Conclusions/Significance

This method of interpretation represents a marked improvement on the current procedure for diagnosing M. bovis infection in live badgers. The results should be of use to inform future test and intervention strategies with the aim of reducing the incidence of TB in free-living wild badger populations.     

Effectiveness of biosecurity measures in preventing badger visits to farm buildings

Background

Bovine tuberculosis caused by Mycobacterium bovis is a serious and economically important disease of cattle. Badgers have been implicated in the transmission and maintenance of the disease in the UK since the 1970s. Recent studies have provided substantial evidence of widespread and frequent visits by badgers to farm buildings during which there is the potential for close direct contact with cattle and contamination of cattle feed.

Methodology

Here we evaluated the effectiveness of simple exclusion measures in improving farm biosecurity and preventing badger visits to farm buildings. In the first phase of the study, 32 farms were surveyed using motion-triggered infrared cameras on potential entrances to farm buildings to determine the background level of badger visits experienced by each farm. In the second phase, they were divided into four treatment groups; “Control”, “Feed Storage”, “Cattle Housing” and “Both”, whereby no exclusion measures were installed, exclusion measures were installed on feed storage areas only, cattle housing only or both feed storage and cattle housing, respectively. Badger exclusion measures included sheet metal gates, adjustable metal panels for gates, sheet metal fencing, feed bins and electric fencing. Cameras were deployed for at least 365 nights in each phase on each farm.

Results

Badger visits to farm buildings occurred on 19 of the 32 farms in phase one. In phase two, the simple exclusion measures were 100% effective in preventing badger entry into farm buildings, as long as they were appropriately deployed. Furthermore, the installation of exclusion measures also reduced the level of badger visits to the rest of the farmyard. The findings of the present study clearly demonstrate how relatively simple practical measures can substantially reduce the likelihood of badger visits to buildings and reduce some of the potential for contact and disease transmission between badgers and cattle.     

Local cattle and badger populations affect the risk of confirmed tuberculosis in British cattle herds

Background

The control of bovine tuberculosis (bTB) remains a priority on the public health agenda in Great Britain, after launching in 1998 the Randomised Badger Culling Trial (RBCT) to evaluate the effectiveness of badger (Meles meles) culling as a control strategy. Our study complements previous analyses of the RBCT data (focusing on treatment effects) by presenting analyses of herd-level risks factors associated with the probability of a confirmed bTB breakdown in herds within each treatment: repeated widespread proactive culling, localized reactive culling and no culling (survey-only).

Methodology/Principal Findings

New cases of bTB breakdowns were monitored inside the RBCT areas from the end of the first proactive badger cull to one year after the last proactive cull. The risk of a herd bTB breakdown was modeled using logistic regression and proportional hazard models adjusting for local farm-level risk factors. Inside survey-only and reactive areas, increased numbers of active badger setts and cattle herds within 1500 m of a farm were associated with an increased bTB risk. Inside proactive areas, the number of M. bovis positive badgers initially culled within 1500 m of a farm was the strongest predictor of the risk of a confirmed bTB breakdown.

Conclusions/Significance

The use of herd-based models provide insights into how local cattle and badger populations affect the bTB breakdown risks of individual cattle herds in the absence of and in the presence of badger culling. These measures of local bTB risks could be integrated into a risk-based herd testing programme to improve the targeting of interventions aimed at reducing the risks of bTB transmission.     

Transmission of Mycobacterium tuberculosis between Farmers and Cattle in Central Ethiopia

Background

Transmission of Mycobacterium tuberculosis (M. tuberculosis) complex could be possible between farmers and their cattle in Ethiopia.

Methodology/Principal Findings

A study was conducted in mixed type multi-purposes cattle raising region of Ethiopia on 287 households (146 households with case of pulmonary tuberculosis (TB) and 141 free of TB) and 287 herds consisting of 2,033 cattle belonging to these households to evaluate transmission of TB between cattle and farmers. Interview, bacteriological examinations and molecular typing were used for human subjects while comparative intradermal tuberculin (CIDT) test, post mortem and bacteriological examinations, and molecular typing were used for animal studies. Herd prevalence of CIDT reactors was 9.4% and was higher (p<0.01) in herds owned by households with TB than in herds owned by TB free households. Animal prevalence was 1.8% and also higher (p<0.01) in cattle owned by households with TB case than in those owned by TB free households. All mycobacteria (141) isolated from farmers were M. tuberculosis, while only five of the 16 isolates from cattle were members of the M. tuberculosis complex (MTC) while the remaining 11 were members of non-tuberculosis mycobacteria (NTM). Further speciation of the five MTC isolates showed that three of the isolates were M. bovis (strain SB1176), while the remaining two were M. tuberculosis strains (SIT149 and SIT53). Pathology scoring method described by “Vordermeier et al. (2002)” was applied and the average severity of pathology in two cattle infected with M. bovis, in 11 infected with NTM and two infected with M. tuberculosis were 5.5, 2.1 and 0.5, respectively.

Conclusions/Significance

The results showed that transmission of TB from farmers to cattle by the airborne route sensitizes the cows but rarely leads to TB. Similarly, low transmission of M. bovis between farmers and their cattle was found, suggesting requirement of ingestion of contaminated milk from cows with tuberculous mastitis.     

The Duration of the Effects of Repeated Widespread Badger Culling on Cattle Tuberculosis Following the Cessation of Culling

Background

In the British Isles, control of cattle tuberculosis (TB) is hindered by persistent infection of wild badger (Meles meles) populations. A large-scale field trial—the Randomised Badger Culling Trial (RBCT)—previously showed that widespread badger culling produced modest reductions in cattle TB incidence during culling, which were offset by elevated TB risks for cattle on adjoining lands. Once culling was halted, beneficial effects inside culling areas increased, while detrimental effects on adjoining lands disappeared. However, a full assessment of the utility of badger culling requires information on the duration of culling effects.

Methodology/Principal Findings

We monitored cattle TB incidence in and around RBCT areas after culling ended. We found that benefits inside culled areas declined over time, and were no longer detectable by three years post-culling. On adjoining lands, a trend suggesting beneficial effects immediately after the end of culling was insignificant, and disappeared after 18 months post-culling. From completion of the first cull to the loss of detectable effects (an average five-year culling period plus 2.5 years post-culling), cattle TB incidence was 28.7% lower (95% confidence interval [CI] 20.7 to 35.8% lower) inside ten 100 km² culled areas than inside ten matched no-culling areas, and comparable (11.7% higher, 95% CI: 13.0% lower to 43.4% higher, p  =  0.39) on lands ≤2 km outside culled and no-culling areas. The financial costs of culling an idealized 150 km² area would exceed the savings achieved through reduced cattle TB, by factors of 2 to 3.5.

Conclusions/Significance

Our findings show that the reductions in cattle TB incidence achieved by repeated badger culling were not sustained in the long term after culling ended and did not offset the financial costs of culling. These results, combined with evaluation of alternative culling methods, suggest that badger culling is unlikely to contribute effectively to the control of cattle TB in Britain.     

Construction of eukaryotic expression vectors encoding CFP-10 and ESAT-6 genes and their potential in lymphocyte proliferation

Background:

Mycobacterium (M.) bovis is the agent of bovine tuberculosis (TB) in a range of animal species, including humans. Recent advances in immunology and the molecular biology of Mycobacterium have allowed identification of a large number of antigens with the potential for the development of a new TB vaccine. The ESAT-6 and CFP-10 proteins of M. bovis are important structural and functional proteins known to be important immunogens.

Methods:

In the current study, the DNAs encoding these genes were utilized in the construction of pcDNA 3.1+/ESAT-6 and pcDNA3.1+/CFP-10 plasmids. After intramuscular injection of BALB/c mice with these plasmids, ESAT-6 and CFP-10 mRNA expression was assessed by RT-PCR. Mice were inoculated and boosted with the plasmids to evaluate their effects on lymphocyte proliferation.

Results:

Our results indicate the plasmids are expressed at the RNA level and can induce lymphocyte proliferation.

Conclusion:

Further study is needed to characterize the effect of these antigens on the immune system and determine whether they are effective vaccine candidates against M. bovis. Key Words: Mycobacterium bovis, DNA vaccine, ESAT-6, CFP-10, PPD, Proliferation assay, BALB/c mice     

Patients Are Paying Too Much for Tuberculosis: A Direct Cost-Burden Evaluation in Burkina Faso

Background

Paying for health care may exclude poor people. Burkina Faso adopted the DOTS strategy implementing “free care” for Tuberculosis (TB) diagnosis and treatment. This should increase universal health coverage and help to overcome social and economic barriers to health access.

Methods

Straddling 2007 and 2008, in-depth interviews were conducted over a year among smear-positive pulmonary tuberculosis patients in six rural districts of Burkina Faso. Out-of-pocket expenses (direct costs) associated with TB were collected according to the different stages of their healthcare pathway.

Results

Median direct cost associated with TB was US$101 (n = 229) (i.e. 2.8 months of household income). Respectively 72% of patients incurred direct costs during the pre-diagnosis stage (i.e. self-medication, travel, traditional healers'' services), 95% during the diagnosis process (i.e. user fees, travel costs to various providers, extra sputum smears microscopy and chest radiology), 68% during the intensive treatment (i.e. medical and travel costs) and 50% during the continuation treatment (i.e. medical and travel costs). For the diagnosis stage, median direct costs already amounted to 35% of overall direct costs.

Conclusions

The patient care pathway analysis in rural Burkina Faso showed substantial direct costs and healthcare system delay within a “free care” policy for TB diagnosis and treatment. Whether in terms of redefining the free TB package or rationalizing the care pathway, serious efforts must be undertaken to make “free” health care more affordable for the patients. Locally relevant for TB, this case-study in Burkina Faso has a real potential to document how health programs'' weaknesses can be identified and solved.     

Beneficial Effect of Isoniazid Preventive Therapy and Antiretroviral Therapy on the Incidence of Tuberculosis in People Living with HIV in Ethiopia

Background

IPT with or without concomitant administration of ART is a proven intervention to prevent tuberculosis among PLHIV. However, there are few data on the routine implementation of this intervention and its effectiveness in settings with limited resources.

Objectives

To measure the level of uptake and effectiveness of IPT in reducing tuberculosis incidence in a cohort of PLHIV enrolled into HIV care between 2007 and 2010 in five hospitals in southern Ethiopia.

Methods

A retrospective cohort analysis of electronic patient database was done. The independent effects of no intervention, “IPT-only,” “IPT-before-ART,” “IPT-and-ART started simultaneously,” “ART-only,” and “IPT-after-ART” on TB incidence were measured. Cox-proportional hazards regression was used to assess association of treatment categories with TB incidence.

Results

Of 7,097 patients, 867 were excluded because they were transferred-in; a further 823 (12%) were excluded from the study because they were either identified to have TB through screening (292 patients) or were on TB treatment (531). Among the remaining 5,407 patients observed, IPT had been initiated for 39% of eligible patients. Children, male sex, advanced disease, and those in Pre-ART were less likely to be initiated on IPT. The overall TB incidence was 2.6 per 100 person-years. As compared to those with no intervention, use of “IPT-only” (aHR = 0.36, 95% CI = 0.19–0.66) and “ART-only” (aHR = 0.32, 95% CI = 0.24–0.43) were associated with significant reduction in TB incidence rate. Combining ART and IPT had a more profound effect. Starting IPT-before-ART (aHR = 0.18, 95% CI = 0.08–0.42) or simultaneously with ART (aHR = 0.20, 95% CI = 0.10–0.42) provided further reduction of TB at ∼80%.

Conclusions

IPT was found to be effective in reducing TB incidence, independently and with concomitant ART, under programme conditions in resource-limited settings. The level of IPT provision and effectiveness in reducing TB was encouraging in the study setting. Scaling up and strengthening IPT service in addition to ART can have beneficial effect in reducing TB burden among PLHIV in settings with high TB/HIV burden.     

Do We Need to Detect Isoniazid Resistance in Addition to Rifampicin Resistance in Diagnostic Tests for Tuberculosis?

Background

Multidrug-resistant tuberculosis (MDR-TB) is resistant to both rifampicin (RIF) and isoniazid (INH). Whereas many TB diagnostics detect RIF-resistance, few detect INH-monoresistance, which is common and may increase risk of acquired MDR-TB. Whether inclusion of INH-resistance in a first-line rapid test for TB would have an important impact on MDR-TB rates remains uncertain.

Methods

We developed a transmission model to evaluate three tests in a population similar to that of India: a rapid molecular test for TB, the same test plus RIF-resistance detection (“TB+RIF”), and detection of RIF and INH-resistance (“TB+RIF/INH”). Our primary outcome was the prevalence of INH-resistant and MDR-TB at ten years.

Results

Compared to the TB test alone and assuming treatment of all diagnosed MDR cases, the TB+RIF test reduced the prevalence of MDR-TB among all TB cases from 5.5% to 3.8% (30.6% reduction, 95% uncertainty range, UR: 17–54%). Despite using liberal assumptions about the impact of INH-monoresistance on treatment outcomes and MDR-TB acquisition, expansion from TB+RIF to TB+RIF/INH lowered this prevalence only from 3.8% to 3.6% further (4% reduction, 95% UR: 3–7%) and INH-monoresistant TB from 15.8% to 15.1% (4% reduction, 95% UR: (-8)-19%).

Conclusion

When added to a rapid test for TB plus RIF-resistance, detection of INH-resistance has minimal impact on transmission of TB, MDR-TB, and INH-monoresistant TB.     

First-Time Detection of Mycobacterium bovis in Livestock Tissues and Milk in the West Bank,Palestinian Territories

Background

Bovine tuberculosis, bTB, is classified by the WHO as one of the seven neglected zoonontic diseases that cause animal health problems and has high potential to infect humans. In the West Bank, bTB was not studied among animals and the prevalence of human tuberculosis caused by M. bovis is unknown. Therefore, the aim of this study was to estimate the prevalence of bTB among cattle and goats and identify the molecular characteristics of bTB in our area.

Methodology/principal findings

A total of 208 tissue samples, representing 104 animals, and 150 raw milk samples, obtained from cows and goats were examined for the presence of mycobacteria. The tissue samples were collected during routine meat inspection from the Jericho abattoir. DNA was extracted from all samples, milk and tissue biopsies (n = 358), and screened for presence of TB DNA by amplifying a 123-bp segment of the insertion sequence IS6110. Eight out of 254 animals (3.1%) were found to be TB positive based on the IS6110-PCR. Identification of M. bovis among the positive TB samples was carried out via real time PCR followed by high resolution melt curve analysis, targeting the A/G transition along the oxyR gene. Spoligotyping analysis revealed a new genotype of M. bovis that was revealed from one tissue sample.

Significance

Detection of M. bovis in tissue and milk of livestock suggests that apparently healthy cattle and goats are a potential source of infection of bTB and may pose a risk to public health. Hence, appropriate measures including meat inspection at abattoirs in the region are required together with promotion of a health campaign emphasizing the importance of drinking pasteurized milk. In addition, further studies are essential at the farm level to determine the exact prevalence of bTB in goats and cattle herds in the West Bank and Israel.     

Recombinant ESAT-6-CFP10 Fusion Protein Induction of Th1/Th2 Cytokines and FoxP3 Expressing Treg Cells in Pulmonary TB

Background

Early secretory antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10) are Mycobacterium tuberculosis (Mtb)–specific antigens that are secreted by actively metabolising bacteria and contribute to the virulence of the bacteria. Their ability to induce Treg and Th2 responses, particularly during the first two weeks of treatment, has not been comprehensively examined to date. The purpose of this work was to characterise Th1, Th2 and Treg responses to rESAT-6-CFP10 fusion protein in TB patients before and during the intensive phase of treatment and in healthy M.bovis BCG vaccinated donors.

Methods

Forty-six newly diagnosed, HIV-negative, smear-positive pulmonary TB patients and 20 healthy donors were recruited in the UK and Ghana. Their peripheral blood mononuclear cells (PBMC) were used in ex vivo ELISPOT and in vitro cultures to identify immunological parameters of interest.

Results

The study confirmed that protective immune responses to rESAT-6-CFP10 are impaired in active TB but improved during treatment: circulating antigen-specific IL-4-producing T-cells were increased in untreated TB but declined by two weeks of treatment while the circulating antigen-specific IFN-γ producing T cells which showed a transient rise at one week of treatment, persisted at baseline levels at two months of treatment. In vitro T cell proliferation and IFN-γ production were reduced, while IL-4 and CD4⁺FoxP3⁺CD25^hi cell expression were increased in response to rESAT-6-CFP10 fusion protein in untreated TB. These responses were reversed during early treatment of TB.

Conclusions

These observations support further investigations into the possible utility of these parameters as markers of active disease and favourable treatment outcomes.     

High Utility of Contact Investigation for Latent and Active Tuberculosis Case Detection among the Contacts: A Retrospective Cohort Study in Tbilisi,Georgia, 2010–2011

Setting

The study was conducted at the National Center for Tuberculosis and Lung Diseases (NCTBLD) in Tbilisi, Georgia.

Objective

To assess the utility of contact investigation for tuberculosis (TB) case detection. We also assessed the prevalence and risk factors for active TB disease and latent TB infection (LTBI) among contacts of active pulmonary TB cases.

Design

A retrospective cohort study was conducted among the contacts of active pulmonary TB cases registered in 2010–2011 at the NCTBLD in Tbilisi, Georgia. Contacts of active TB patients were investigated according to an “invitation model”: they were referred to the NCTBLD by the index case; were queried about clinical symptoms suggestive of active TB disease; tuberculin skin testing and chest radiographs were performed. Demographic, laboratory, and clinical data of TB patients and their contacts were abstracted from existing records up to February 2013.

Results

869 contacts of 396 index cases were enrolled in the study; a median of 2 contacts were referred per index case. Among the 869 contacts, 47 (5.4%) were found to have or developed active TB disease: 30 (63.8%) were diagnosed with TB during the baseline period (co-prevalent cases) and 17 (36.2%) developed active TB disease during the follow-up period (mean follow up of 21 months) (incident TB cases). The incidence rate of active TB disease among contacts was 1126.0 per 100 000 person years (95% CI 655.7–1802.0 per 100,000 person-years). Among the 402 contacts who had a tuberculin skin test (TST) performed, 52.7% (95% CI 47.7–57.7%) had LTBI.

Conclusions

A high prevalence of LTBI and active TB disease was found among the contacts of TB cases in Tbilisi, Georgia. Our findings demonstrated that an “invitation” model of contact investigation was an effective method of case detection. Therefore, contact investigation should be scaled up in Georgia.     

Peripheral T cell cytokine responses for diagnosis of active tuberculosis

Background

A test for diagnosis of active Tuberculosis (TB) from peripheral blood could tremendously improve clinical management of patients.

Methods

Of 178 prospectively enrolled patients with possible TB, 60 patients were diagnosed with pulmonary and 27 patients with extrapulmonary TB. The frequencies of Mycobacterium tuberculosis (MTB) specific CD4⁺ T cells and CD8⁺ T cells producing cytokines were assessed using overnight stimulation with purified protein derivate (PPD) or early secretory antigenic target (ESAT)-6, respectively.

Results

Among patients with active TB, an increased type 1 cytokine profile consisting of mainly CD4⁺ T cell derived interferon (IFN)-γ was detectable. Despite contributing to the cytokine profile as a whole, the independent diagnostic performance of one cytokine producing T cells as well as polyfunctional T cells was poor. IFN-γ/Interleukin(IL)-2 cytokine ratios discriminated best between active TB and other diseases.

Conclusion

T cells producing one cytokine and polyfunctional T cells have a limited role in diagnosis of active TB. The significant shift from a “memory type” to an “effector type” cytokine profile may be useful for further development of a rapid immune-diagnostic tool for active TB.     

Weather influences trapping success for tuberculosis management in European badgers (<Emphasis Type="Italic">Meles meles</Emphasis>)

European badgers (Meles meles) in Ireland and the UK are a reservoir for Mycobacterium bovis, the causative agent of bovine tuberculosis (TB). A number of interventions have been evaluated in attempts to control bovine TB within badger populations, and many of which rely on the capture of badgers. One strategy being implemented within Ireland is intramuscular vaccination using Bacillus Calmette-Guérin (BCG), as an alternative to badger culling. The success of vaccination as a disease control strategy depends on the ability to capture badgers and administer vaccines; thus, trapping success is crucial to effectively vaccinate the population (maximize vaccine coverage). A field vaccine trial was conducted in County Kilkenny, Ireland, from 2010–2013. We used data from this trial to evaluate the association between weather (precipitation and temperature data), badger sett characteristics, and badger trapping success. Approximately 10% of capture efforts resulted in a badger capture. Our results indicate that badger captures were the highest in drizzle, rain, and heavy rain weather conditions, and when minimum temperatures ranged from 3–8 °C. Badger captures were the highest at main setts (large burrow systems), and when sett activity scores were high (qualitative classes 4 or 5). Using local precipitation and temperature data in conjunction with observed sett characteristics provides wildlife managers with guidelines to optimize trapping success. Implementing capture operations under optimal conditions should increase the trapping success of badgers and allow for increased delivery of vaccines to manage bovine TB.     

Prevalence of Latent and Active Tuberculosis among Dairy Farm Workers Exposed to Cattle Infected by Mycobacterium bovis

Background

Human tuberculosis caused by M. bovis is a zoonosis presently considered sporadic in developed countries, but remains a poorly studied problem in low and middle resource countries. The disease in humans is mainly attributed to unpasteurized dairy products consumption. However, transmission due to exposure of humans to infected animals has been also recognized. The prevalence of tuberculosis infection and associated risk factors have been insufficiently characterized among dairy farm workers (DFW) exposed in settings with poor control of bovine tuberculosis.

Methodology/Principal Findings

Tuberculin skin test (TST) and Interferon-gamma release assay (IGRA) were administered to 311 dairy farm and abattoir workers and their household contacts linked to a dairy production and livestock facility in Mexico. Sputa of individuals with respiratory symptoms and samples from routine cattle necropsies were cultured for M. bovis and resulting spoligotypes were compared. The overall prevalence of latent tuberculosis infection (LTBI) was 76.2% (95% CI, 71.4–80.9%) by TST and 58.5% (95% CI, 53.0–64.0%) by IGRA. Occupational exposure was associated to TST (OR 2.72; 95% CI, 1.31–5.64) and IGRA (OR 2.38; 95% CI, 1.31–4.30) adjusting for relevant variables. Two subjects were diagnosed with pulmonary tuberculosis, both caused by M. bovis. In one case, the spoligotype was identical to a strain isolated from bovines.

Conclusions

We documented a high prevalence of latent and pulmonary TB among workers exposed to cattle infected with M. bovis, and increased risk among those occupationally exposed in non-ventilated spaces. Interspecies transmission is frequent and represents an occupational hazard in this setting.     

Incidence of TB and HIV in Prospectively Followed Household Contacts of TB Index Patients in South Africa

Objective

To report the incidence rates of TB and HIV in household contacts of index patients diagnosed with TB.

Design

A prospective cohort study in the Matlosana sub-district of North West Province, South Africa.

Methods

Contacts of index TB patients received TB and HIV testing after counseling at their first household visit and were then followed up a year later, in 2010. TB or HIV diagnoses that occurred during the period were determined.

Results

For 2,377 household contacts, the overall observed TB incidence rate was 1.3 per 100 person years (95% CI 0.9–1.9/100py) and TB incidence for individuals who were HIV-infected and HIV seronegative at baseline was 5.4/100py (95% CI 2.9–9.0/100py) and 0.7/100py (95% CI 0.3–1.4/100py), respectively. The overall HIV incidence rate was 2.2/100py (95% CI 1.3–8.4/100py).

Conclusions

In the year following a household case finding visit when household contacts were tested for TB and HIV, the incidence rate of both active TB and HIV infection was found to be extremely high. Clearly, implementing proven strategies to prevent HIV acquisition and preventing TB transmission and progression to disease remains a priority in settings such as South Africa.     

A novel multiplex real-time PCR for the identification of mycobacteria associated with zoonotic tuberculosis

Background

Tuberculosis (TB) is the leading cause of death worldwide from a single infectious agent. An ability to detect the Mycobacterium tuberculosis complex (MTC) in clinical material while simultaneously differentiating its members is considered important. This allows for the gathering of epidemiological information pertaining to the prevalence, transmission and geographical distribution of the MTC, including those MTC members associated with zoonotic TB infection in humans. Also differentiating between members of the MTC provides the clinician with inherent MTC specific drug susceptibility profiles to guide appropriate chemotherapy.

Methodology/Principal Findings

The aim of this study was to develop a multiplex real-time PCR assay using novel molecular targets to identify and differentiate between the phylogenetically closely related M. bovis, M. bovis BCG and M. caprae. The lpqT gene was explored for the collective identification of M. bovis, M. bovis BCG and M. caprae, the lepA gene was targeted for the specific identification of M. caprae and a Region of Difference 1 (RD1) assay was incorporated in the test to differentiate M. bovis BCG. The multiplex real-time PCR assay was evaluated on 133 bacterial strains and was determined to be 100% specific for the members of the MTC targeted.

Conclusions/Significance

The multiplex real-time PCR assay developed in this study is the first assay described for the identification and simultaneous differentiation of M. bovis, M. bovis BCG and M. caprae in one internally controlled reaction. Future validation of this multiplex assay should demonstrate its potential in the rapid and accurate diagnosis of TB caused by these three mycobacteria. Furthermore, the developed assay may be used in conjunction with a recently described multiplex real-time PCR assay for identification of the MTC and simultaneous differentiation of M. tuberculosis, M. canettii resulting in an ability to differentiate five of the eight members of the MTC.     

Outcomes among HIV-1 Infected Individuals First Starting Antiretroviral Therapy with Concurrent Active TB or Other AIDS-Defining Disease

Background

Tuberculosis (TB) is common among HIV-infected individuals in many resource-limited countries and has been associated with poor survival. We evaluated morbidity and mortality among individuals first starting antiretroviral therapy (ART) with concurrent active TB or other AIDS-defining disease using data from the “Prospective Evaluation of Antiretrovirals in Resource-Limited Settings” (PEARLS) study.

Methods

Participants were categorized retrospectively into three groups according to presence of active confirmed or presumptive disease at ART initiation: those with pulmonary and/or extrapulmonary TB (“TB” group), those with other non-TB AIDS-defining disease (“other disease”), or those without concurrent TB or other AIDS-defining disease (“no disease”). Primary outcome was time to the first of virologic failure, HIV disease progression or death. Since the groups differed in characteristics, proportional hazard models were used to compare the hazard of the primary outcome among study groups, adjusting for age, sex, country, screening CD4 count, baseline viral load and ART regimen.

Results

31 of 102 participants (30%) in the “TB” group, 11 of 56 (20%) in the “other disease” group, and 287 of 1413 (20%) in the “no disease” group experienced a primary outcome event (p = 0.042). This difference reflected higher mortality in the TB group: 15 (15%), 0 (0%) and 41 (3%) participants died, respectively (p<0.001). The adjusted hazard ratio comparing the “TB” and “no disease” groups was 1.39 (95% confidence interval: 0.93–2.10; p = 0.11) for the primary outcome and 3.41 (1.72–6.75; p<0.001) for death.

Conclusions

Active TB at ART initiation was associated with increased risk of mortality in HIV-1 infected patients.     

Heparin-Binding Haemagglutinin,a New Tool for the Detection of Latent Mycobacterium tuberculosis Infection in Hemodialysis Patients

Background

Patients with end-stage renal disease (ESRD) and latently infected with Mycobacterium tuberculosis (LTBI) are at higher risk to develop tuberculosis (TB) than healthy subjects. Interferon-gamma release assays (IGRAs) were reported to be more sensitive than tuberculin skin tests for the detection of infected individuals in dialysis patients.

Methods

On 143 dialysis patients prospectively enrolled, we compared the results from the QuantiFERON®-TB Gold assay (QFT), to those of an IGRA in response to in vitro stimulation of circulating mononuclear cells with the mycobacterial latency antigen Heparin-Binding Haemagglutinin purified from Mycobacterium bovis BCG (native HBHA, nHBHA).

Results

Seven patients had a past history of active TB and 1 had an undetermined result with both IGRAs. Among the other 135 patients, 94 had concordant results with the QFT and nHBHA-IGRA, 40.0% being negative and therefore not latently infected, and 29.6% being positive and thus LTBI. Discrepant results between these tests were found for 36 patients positive only with the nHBHA-IGRA and 5 only with the QFT.

Conclusions

The nHBHA-IGRA is more sensitive than the QFT for the detection of LTBI dialysis patients, and follow-up of the patients will allow us to define the clinical significance of discrepant results between the nHBHA-IGRA and the QFT.     

Cost-Effectiveness of a Community Pharmacist-Led Sleep Apnea Screening Program – A Markov Model

Background

Despite the high prevalence and major public health ramifications, obstructive sleep apnea syndrome (OSAS) remains underdiagnosed. In many developed countries, because community pharmacists (CP) are easily accessible, they have been developing additional clinical services that integrate the services of and collaborate with other healthcare providers (general practitioners (GPs), nurses, etc.). Alternative strategies for primary care screening programs for OSAS involving the CP are discussed.

Objective

To estimate the quality of life, costs, and cost-effectiveness of three screening strategies among patients who are at risk of having moderate to severe OSAS in primary care.

Design

Markov decision model.

Data Sources

Published data.

Target Population

Hypothetical cohort of 50-year-old male patients with symptoms highly evocative of OSAS.

Time Horizon

The 5 years after initial evaluation for OSAS.

Perspective

Societal.

Interventions

Screening strategy with CP (CP-GP collaboration), screening strategy without CP (GP alone) and no screening.

Outcomes measures

Quality of life, survival and costs for each screening strategy.

Results of base-case analysis

Under almost all modeled conditions, the involvement of CPs in OSAS screening was cost effective. The maximal incremental cost for “screening strategy with CP” was about 455€ per QALY gained.

Results of sensitivity analysis

Our results were robust but primarily sensitive to the treatment costs by continuous positive airway pressure, and the costs of untreated OSAS. The probabilistic sensitivity analysis showed that the “screening strategy with CP” was dominant in 80% of cases. It was more effective and less costly in 47% of cases, and within the cost-effective range (maximum incremental cost effectiveness ratio at €6186.67/QALY) in 33% of cases.

Conclusions

CP involvement in OSAS screening is a cost-effective strategy. This proposal is consistent with the trend in Europe and the United States to extend the practices and responsibilities of the pharmacist in primary care.