Phthisiology at the dawn of the new century

The Mycobacterium tuberculosis Uganda II family and resistance to first-line anti-tuberculosis drugs in Uganda

Background

The global increase in the burden of multidrug-resistant tuberculosis (MDR-TB) underscores an urgent need for data on factors involved in generation and spread of TB drug resistance. We performed molecular analyses on a representative sample of Mycobacterium tuberculosis (MTB) isolates. Basing on findings of the molecular epidemiological study in Kampala, we hypothesized that the predominant MTB strain lineage in Uganda is negatively associated with anti-TB drug resistance and we set out to test this hypothesis.

Methods

We extracted DNA from mycobacterial isolates collected from smear-positive TB patients in the national TB drug resistance survey and carried out IS6110-PCR. To identify MTB lineages/sub lineages RT-PCR SNP was performed using specific primers and hybridization probes and the ‘melting curve’ analysis was done to distinguish the Uganda II family from other MTB families. The primary outcome was the distribution of the Uganda II family and its associations with anti-TB drug resistance and HIV infection.

Results

Out of the 1537 patients enrolled, MTB isolates for 1001 patients were available for SNP analysis for identification of Uganda II family, of which 973 (97%) had conclusive RT-PCR results. Of these 422 (43.4%) were of the Uganda II family, mostly distributed in the south west zone (55.0%; OR = 4.6 for comparison with other zones; 95% CI 2.83-7.57; p < 0.001) but occurred in each of the other seven geographic zones at varying levels. Compared to the Uganda II family, other genotypes as a group were more likely to be resistant to any anti-TB drug (OR^adj =2.9; 95% CI 1.63-5.06; p = 0.001) or MDR (OR^adj 4.9; 95% CI, 1.15-20.60; p = 0.032), even after adjusting for geographic zone, patient category, sex, residence and HIV status. It was commonest in the 25–34 year age group 159/330 (48.2%). No association was observed between Uganda II family and HIV infection.

Conclusion

The Uganda II family is a major cause of morbidity due to TB in all NTLP zones in Uganda. It is less likely to be resistant to anti-TB drugs than other MTB strain lineages.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0703-0) contains supplementary material, which is available to authorized users.

Causes and predictive factors associated with "diagnosis changed" outcomes in patients notified as tuberculosis cases in a private tertiary hospital

Background

The aim of our study was to evaluate the "diagnosis changed" rate in patients notified as tuberculosis (TB) on the Korean TB surveillance system (KTBS).

Methods

A total of 1,273 patients notified as TB cases on the KTBS in one private tertiary hospital in 2011 were enrolled in the present study. Patients were classified into three groups: "diagnosis maintained", "diagnosis changed" (initially notified as TB, but ultimately diagnosed as non-TB), and "administrative error" (notified as TB due to administrative errors).

Results

Excluding 17 patients in the "administrative error" group, the "diagnosis maintained" and "diagnosis changed" groups included 1,097 (87.3%) and 159 patients (12.7%), respectively. Common causes of "diagnosis changed" were nontuberculous mycobacterial (NTM) disease (51.7%, 61/118), and pneumonia (17.8%) in cases notified as pulmonary TB, and meningitis (19.5%, 8/41) and Crohn's disease (12.2%) in cases notified as extrapulmonary TB. Being older than 35 years of age (odds ratio [OR], 2.18) and a positive acid-fast bacilli stain (OR, 1.58) were positive predictors and a TB-related radiological finding (OR, 0.42) was a negative predictor for a "diagnosis changed" result via multivariate logistic regression analysis in pulmonary TB cases.

Conclusion

Because of a high "diagnosis changed" rate in TB notifications to the KTBS, the TB incidence rate measured by the KTBS may be overestimated. Considering the worldwide trend toward increased NTM disease, the "diagnosis changed" rate may increase over time. Thus, when reporting the annual TB notification rate in Korea, the exclusion of "diagnosis changed" cases is desirable.

Predictors of pulmonary involvement in patients with extra-pulmonary tuberculosis

Objectives:

The aim of this study is to assess the value of chest radiographs (CXRs) and sputum examinations in detecting pulmonary involvement of tuberculosis (TB) in patients with extra-pulmonary tuberculosis (EPTB).

Materials and Methods:

A retrospective analysis was performed among 248 EPTB patients with culture-proven diagnosis of tuberculosis seen between January 2001 and December 2007 at a tertiary teaching hospital, Riyadh, Saudi Arabia. Demographics, clinical, laboratory and radiological findings were reviewed and assessed. This study was approved by the hospital ethics and research committee.

Results:

One hundred twenty five of 233 EPTB patients (53.6%) had abnormal CXR findings. There was a significant difference in the occurrence of positive sputum culture results between patients with abnormal CXR findings (30/57) and those with normal CXR findings (4/17) (P = 0.04). Of 17 HIV-negative/unknown HIV-status EPTB patients with normal CXR results, 4 patients (23.5%) had positive sputum culture results. Intrathoracic lymphadenopathy (P < 0.001), pleural TB (P < 0. 001) and disseminated TB (P = 0.004) were associated with an increased risk of abnormal CXR findings. Patients with cough (52.9%), weight loss (41.2%) and night sweats (26.5%) are more likely to have positive sputum culture results.

Conclusion:

CXR findings are predictive of positive sputum culture results. However, the rate of normal CXR among EPTB patients with positive sputum culture results was relatively high. Therefore, respiratory specimen cultures should be obtained in TB suspects with a normal CXR to identify potentially infectious cases of TB.

First-line antituberculosis drug resistance prevalence and its pattern among HIV-infected patients in the national referral tuberculosis centre, Iran

The objective of this study was to determine the drug resistance prevalence and its pattern among tuberculosis (TB)–HIV patients in Iran. In this retrospective study, all admitted TB/HIV patients presenting to our tertiary centre during 2005–2007 were considered. After confirmation for TB–HIV, first-line DST was performed for culture-positive patients. The drug resistance patterns and the treatment outcomes were analysed. Of the total 92 TB/HIV patients, 27 were culture negative, and DST were available in 65. Intravenous drug abuse was seen in 59 (90.8%). Thirty-seven (57%) were ‘sensitive’ cases and 28 (43%) were ‘any drug resistance’ cases. Twenty-one (32.3%) were mono-drug, three (4.6%) poly-drug and four (6.1%) were multidrug-resistant TB patients. Previous anti-TB medication was significantly associated with any drug resistance ( P = 0.041; 95% confidence interval =0.086–0.984); however, having any drug resistance did not affect the treatment outcome ( P = 0.56). Streptomycin showed the highest resistance rate (27%) followed by isoniazid (20%), pyrazinamide (9.8%), rifampin (9.2%) and ethambutol (3%). Drug resistance to antitubercular agents in TB–HIV co-infected patients in Iran is high compared with other reports. Drug resistance is higher among those who have had prior anti-TB medication.

Predictors for identifying the most infectious pulmonary tuberculosis patient

BACKGROUND/PURPOSE

Clinicians need to decide whether to begin isolation and empiric therapy for patients suspected of having infectious tuberculosis (TB). This study aimed to identify the demographic, clinical and radiographic characteristics of acid-fast bacilli (AFB) smear-positive patients and to create a smear-positive TB prediction rule, which clinicians may use to predict risk.

METHODS

This was a retrospective study involving 105 patients with AFB smear-positive TB and 52 patients with AFB smear-negative TB at Kaohsiung Municipal Hsiao-Kang Hospital in southern Taiwan from August 1, 2003 to July 31, 2006. All of the patients had at least one sputum culture that was positive for Mycobacterium tuberculosis. Demographic, clinical and radiographic data of patients with AFB smear-positive TB were compared to those of patients with AFB smear-negative TB.

RESULTS

On univariate analysis, young age (p = 0.033), alcoholism (p = 0.036), weight loss (p = 0.003), fever (p = 0.018), consolidation (p = 0.001), infiltration (p = 0.012), cavitary pattern (p = 0.005), right upper lung field (p < 0.001) and left upper lung field (p = 0.001) lesions on chest radiographs were found to be predictive of smear-positive TB patients. In contrast, end-stage renal disease (p = 0.035) and normal chest radiograph (p = 0.006) were predictive of smear-negative TB patients. On multivariate analysis, age less than 65 years (p = 0.004), fever (p = 0.004), right upper lung field (p = 0.044), left upper lung field (p = 0.041), consolidation (p = 0.018) and cavitary (p = 0.049) lesions on chest radiograph were independently associated with an increased risk of an AFB positive smear finding. The smear-positive TB prediction model was created based on the results of the multivariate analysis that had an area of 0.788 under the receiver operating characteristic curve.

CONCLUSION

The smear-positive TB prediction model may help clinicians decide if a patient with pending sputum smear results should first be placed in isolation and empiric anti-tuberculous therapy started.

Could clinical audit improve the diagnosis of pulmonary tuberculosis in Cuba, Peru and Bolivia?

OBJECTIVES

To assess the effectiveness of clinical audit in improving the quality of diagnostic care provided to patients suspected of tuberculosis; and to understand the contextual factors which impede or facilitate its success.

METHODS

Twenty-six health centres in Cuba, Peru and Bolivia were recruited. Clinical audit was introduced to improve the diagnostic care for patients attending with suspected TB. Standards were based on the WHO and TB programme guidelines relating to the appropriate use of microscopy, culture and radiological investigations. At least two audit cycles were completed over 2 years. Improvement was determined by comparing the performance between two six-month periods pre- and post-intervention. Qualitative methods were used to ascertain facilitating and limiting contextual factors influencing change among healthcare professionals' clinical behaviour after the introduction of clinical audit.

RESULTS

We found a significant improvement in 11 of 13 criteria in Cuba, in 2 of 6 criteria in Bolivia and in 2 of 5 criteria in Peru. Twelve out of 24 of the audit criteria in all three countries reached the agreed standards. Barriers to quality improvement included conflicting objectives for clinicians and TB programmes, poor coordination within the health system and patients' attitudes towards illness.

CONCLUSIONS

Clinical audit may drive improvements in the quality of clinical care in resource-poor settings. It is likely to be more effective if integrated within and supported by the local TB programmes. We recommend developing and evaluating an integrated model of quality improvement including clinical audit.

Diagnosis of tuberculosis in an Indian population by an indirect ELISA protocol based on detection of Antigen 85 complex: a prospective cohort study

BACKGROUND

Diagnosis of tuberculosis (TB) remains problematic despite many new advanced diagnostic methods. A reliable and rapid diagnostic test, which could be performed in any standard pathology laboratory, would help to obtain definitive early diagnoses of TB. In the present study we describe a prospective evaluation for demonstrating Antigen (Ag) 85 complex in the sera from TB patients.

METHODS

Indirect ELISA, employing monoclonal antibodies (mAb) against the purified Ag 85 complex, was used to demonstrate Ag 85 complex in sera from TB patients. Serum samples were obtained from 197 different groups of patients: confirmed TB {n = 24}, clinically diagnosed TB {n = 104}, disease controls {n = 49} and healthy controls {n = 20}. Receiver operating curve (ROC) was used to calculate the cut off value and comparison between TB and non-TB groups were done by the chi-square test.

RESULTS

The indirect ELISA method, using an mAb against Ag 85 complex, yielded 82% sensitivity (95% confidence interval [CI] 67 to 93%) and 86% specificity (95% CI, 57 to 98%) for the diagnosis of TB. The serum positivities for Ag 85 complex in cases of confirmed and clinically diagnosed TB patients were 96% (23/24) and 79% (82/104) respectively, while the positivity for patients in the non-tuberculosis group was 14% (10/69).

CONCLUSION

The detection of Ag 85 complex in sera from TB patients by indirect ELISA using mAb against purified Ag 85 complex gives a reliable diagnosis and can be used to develop an immunodiagnostic assay with increased sensitivity and specificity.

M. tuberculosis genotypic diversity and drug susceptibility pattern in HIV-infected and non-HIV-infected patients in northern Tanzania

Background

Tuberculosis (TB) is a major health problem and HIV is the major cause of the increase in TB. Sub-Saharan Africa is endemic for both TB and HIV infection. Determination of the prevalence of M. tuberculosis strains and their drug susceptibility is important for TB control.

TB positive culture, BAL fluid or sputum samples from 130 patients were collected and genotyped. The spoligotypes were correlated with anti-tuberculous drug susceptibility in HIV-infected and non-HIV patients from Tanzania.

Results

One-third of patients were TB/HIV co-infected. Forty-seven spoligotypes were identified.

Fourteen isolates (10.8%) had new and unique spoligotypes while 116 isolates (89.2%) belonged to 33 known spoligotypes. The major spoligotypes contained nine clusters: CAS1-Kili 30.0%, LAM11- ZWE 14.6%, ND 9.2%, EAI 6.2%, Beijing 5.4%, T-undefined 4.6%, CAS1-Delhi 3.8%, T1 3.8% and LAM9 3.8%. Twelve (10.8%) of the 111 phenotypically tested strains were resistant to anti-TB drugs. Eight (7.2%) were monoresistant strains: 7 to isoniazid (INH) and one to streptomycin. Four strains (3.5%) were resistant to multiple drugs: one (0.9%) was resistant to INH and streptomycin and the other three (2.7%) were MDR strains: one was resistant to INH, rifampicin and ethambutol and two were resistant to all four anti-TB drugs. Mutation in the katG gene codon 315 and the rpoB hotspot region showed a low and high sensitivity, respectively, as predictor of phenotypic drug resistance.

Conclusion

CAS1-Kili and LAM11-ZWE were the most common families. Strains of the Beijing family and CAS1-Kili were not or least often associated with resistance, respectively. HIV status was not associated with spoligotypes, resistance or previous TB treatment.

Effect of pharmacist-led patient education on adherence to tuberculosis treatment

PURPOSE

The purpose of this study was to assess the effect of a clinical pharmacist-directed patient education program on the therapy adherence of first-time tuberculosis (TB) patients and to identify the major pharmaceutical care needs and issues of first-time TB and multidrug-resistant (MDR)-TB patients.

METHODS

In the first part of the study, first-time TB patients were randomized either to the No EDU group (n = 58) where patients received routine medical and nursing care or to the EDU group (n = 56) where patients were also provided with clinical pharmacist-directed patient education. The patient's adherence to treatment was evaluated by attendance at scheduled visits, medication counting, and urine analysis for the presence of isoniazid metabolites. In the second part of the study, the pharmaceutical care needs and issues were determined for first-time TB patients and for MDR-TB patients (n = 40).

RESULTS

The adherence of patients who received pharmacist-directed patient education was greater than that of patients who did not. The attendance at scheduled visits and urine analysis for the presence of isoniazid metabolites yielded better results in respect to adherence for the EDU group (p < 0.05), while medication counting did not differ between the two groups. The major pharmaceutical care needs of first-time TB patients were for pain control, nutrient replacement, appropriate prescribing, respiratory control, and diabetic control. Similar findings were recorded for MDR-TB patients.

CONCLUSION

Patients' adherence to TB treatment improved when a pharmacist provided patient education on medication use and addressed patients' pharmaceutical care issues.

Is alcohol use associated with cavitary disease in tuberculosis?

BACKGROUND

Alcohol mediates detrimental alterations in the immune response to Mycobacterium tuberculosis. The association between quantity and frequency of alcohol use and the prevalence of cavitary disease in tuberculosis (TB) has not been analyzed. To investigate the relationship of alcohol use and the prevalence of cavitary disease in a 6-year population-based data set of individuals with TB.

METHODS

We assessed quantity and frequency of alcohol use (daily alcohol use, years of alcohol use, and lifetime alcohol use) with a standardized questionnaire. The study group consisted of 1,250 patients analyzed for cavitary disease (HIV sero-negative subjects that were 18 years or older). Significant covariates for cavitary disease were entered into multiple logistic regression models.

RESULTS

Although daily alcohol use, years of alcohol use, and alcohol use 30 days or 6 months before symptom onset were significant predictors of cavitary disease in univariate analysis, no independent associations were found between alcohol use and cavitary disease in the multivariate analysis. Only diabetes mellitus was independently associated with cavitary disease at any level or frequency of alcohol use.

CONCLUSION

Alcohol use is not independently associated with increased prevalence of cavitary disease in adult patients with TB.

Clinical suspicion as a primary guidance to use commercial amplification tests for rapid diagnosis of pulmonary tuberculosis

The Abbott LCx (Abbott Park, IL) Mycobacterium tuberculosis complex is a commercial amplification assay discontinued from the European market in 2002. A prospective clinical study was carried out to evaluate the clinical utility of the above test as applied by specialists for the rapid diagnosis of active pulmonary tuberculosis (PTB). According to the physician's clinical judgment, patients were classified into 3 groups (low, intermediate, and high) aiming to estimate the probability of active disease. The gold standard for final diagnosis was based on microbiologic and clinical information including data from a 6-month follow-up period. Sensitivities and specificities of rapid microbiologic tests were compared with those based on an integrated approach including clinical evaluation plus the above tests. The incidence of PTB in 214 patients was 13.1%. The basis for initial treatment of PTB was smear-positive results in 46%, positive LCx results in 29%, and clinical suspicion in 18%. For the remaining 7%, therapy was started upon receipt of culture results. The sensitivity, specificity, and positive and negative predictive values of the LCx assay were 68%, 99%, 95%, and 95%, respectively. In comparison, they were 93%, 99%, 96%, and 99%, respectively, for the combination of clinical evaluation plus the LCx test. It is concluded that in patients with high-to-moderate pretest probabilities, the combination of clinical judgment and amplification results strongly enhances a rapid and correct diagnosis of PTB.

Tuberculosis of the chest

The relationship between tuberculosis and mankind has been known for many centuries, with the disease being one of the major causes of illness and death. During the early 1980s, there was a widespread belief that the disease was being controlled, but by the mid-1980s, the number of cases increased. This change in the epidemiological picture has several causes, of which the AIDS epidemic, the progression of poverty in developing countries, the increase in the number of elderly people with an altered immune status and the emergence of multidrug-resistant tuberculosis are the most important. Mainly due to this epidemiological change, the radiological patterns of the disease are also being altered, with the classical distinction between primary and postprimary disease fading and atypical presentations in groups with an altered immune response being increasingly reported. Therefore, the radiologist must be able not only to recognize the classical features of primary and postprimary tuberculosis but also to be familiar with the atypical patterns found in immuno-compromised and elderly patients, since an early diagnosis is generally associated with a greater therapeutic efficacy. Radiologists are, in this way, presented with a new challenge at the beginning of this millennium.

Levels of tumour necrosis factor-alpha and IL-1alpha in newly diagnosed and multidrug resistant tuberculosis

BACKGROUND

The pro-inflammatory cytokines tumour necrosis factor (TNF)-alpha and IL-1alpha play key roles in host defence against tuberculosis (TB) but there is little knowledge of their levels in multidrug resistant TB (MDR-TB). The aim of the present study was to investigate the levels of TNF-alpha and IL-1alpha and their relationship with the levels of T helper (CD4+), T suppressor (CD8+) and total lymphocytes (CD45+) in newly diagnosed TB (N-TB) and MDR-TB.

METHODOLOGY

This study assessed 19 N-TB patients (M/F : 17/2) and 11 MDR-TB patients (M/F : 10/1). Serum TNF-alpha and IL-1alpha were assessed by ELISA. Lymphocyte expression of CD45, CD4, CD8, CD3, CD23, CD19 and CD95 were determined by flow cytometry.

RESULTS

The levels of TNF-alpha, IL-1alpha, and CD4, CD4/CD8, CD45, CD19, CD23 and CD95 positive lymphocytes were lower in MDR-TB than in N-TB patients (P < 0.05). Statistically, there was a positive correlation between TNF-alpha and IL-1alpha (r = 0.92) for both MDR-TB and N-TB. For both groups, both TNF-alpha and IL-1alpha correlated with CD4+ lymphocytes (r = 0.48). TNF-alpha and IL-1alpha showed negative correlations with CD8+ lymphocytes (r = -0.81, r = -0.73) (P < 0.01) in MDR-TB patients.

CONCLUSION

The lower levels of cytokines and numbers of T helper lymphocytes in MDR-TB compared with N-TB implies that the immune profiles of the two groups are different, and may be important in the natural history of the disease.

Rapid mycobacteria drug susceptibility testing using Gel Microdrop (GMD) Growth Assay and flow cytometry

Control of multi-drug-resistant tuberculosis has been hampered by the lack of simple, rapid and sensitive methods for assessing bacterial growth and antimicrobial susceptibility. Due to the increasing incidence and high frequency of mutations, it is unlikely that culture methods will disappear in the foreseeable future. Therefore, the need to modernize methods for rapid detection of viable clinical isolates, at a minimum as a gold standard, will persist. Previously, we confirmed the feasibility of using the Gel Microdrop (GMD) Growth Assay for identifying sub-populations of resistant Mycobacteria by testing different laboratory strains. Briefly, this assay format relies on encapsulating single bacterium in agarose microspheres and identifying clonogenic growth using flow cytometry and fluorescent staining. In this study, we modified the GMD Growth Assay to make it suitable for clinical applications. We demonstrated the effectiveness and safety of this novel approach for detecting drug susceptibility in clinically relevant laboratory strains as well as clinical isolates of Mycobacterium tuberculosis. Correlation between results using the GMD Growth Assay format and results using two well characterized methods (Broth Microdilution MIC and BACTEC 460TB) was 87.5% and 90%, respectively. However, due to the inherent sensitivity of flow cytometry and the ability to detect small (<1%) sub-populations of resistant mycobacteria, the GMD Growth Assay identified more cases of drug resistance. Using 4 clinically relevant mycobacterial strains, we assessed susceptibility to primary anti-tuberculosis drugs using both the Broth Microdilution MIC method and the GMD Growth Assay. We performed 24 tests on isoniazid-resistant BCG, Mycobacterium tuberculosis H37Ra and Mycobacterium avium strains. The Broth Microdilution MIC method identified 7 cases (29.1%) of resistance to INH and EMB compared to the GMD Growth Assay which identified resistance in 10 cases (41.6%); in 3 cases (12.5%), resistance to INH and EMB was detected only with the GMD Growth Assay. In addition, using 20 Mycobacterium tuberculosis clinical isolates, we compared results using BACTEC 460TB method performed by collaborators and the GMD Growth Assay. Eight of 20 (40%) clinical isolates, which were not identified as drug-resistant using the conventional BACTEC 460TB method, were resistant to 1, 2, or 3 different concentrations of drugs using the GMD Growth Assay (13 cases of 140 experiments). In one case (isolate 1879), resistance to 10.0 microg/ml of STR detected using BACTEC 460TB method was not confirmed by the GMD Growth Assay. Thus, the overall agreement between these methods was 90% (14 discrepant results of 140 experiments). These data demonstrate that the GMD Growth Assay is an accurate and sensitive method for rapid susceptibility testing of Mycobacterium tuberculosis for use in clinical reference laboratory settings.

Revised Guidelines for the Diagnosis and Control of Tuberculosis

Despite major progress in the development of new strategies for diagnosing and treating tuberculosis, the disease still remains a major challenge for healthcare workers throughout the world. A number of causes are responsible for this threat but, unfortunately, many of these cannot be resolved easily because of cultural and social factors. Furthermore, not all countries throughout the world have enough financial resources to support educational and therapeutic programmes. The major challenges with tuberculosis are 2-fold: (i) to deal with the growing epidemic around the world (and especially in 'low-income' [developing] countries), and; (ii) to ensure correct use of antituberculosis medications in order to protect these drugs for future use. In 'high-income' countries, a major decline in the incidence of tuberculosis has been observed. Nevertheless, tuberculosis remains an important challenge in some risk groups, particularly the elderly patient, in these countries. The clinical and radiological presentations are often nonspecific, leading to delayed diagnosis and appropriate treatment, which often results in a large proportion of cases being discovered at autopsy only. Considering tuberculosis in the differential diagnosis remains the cornerstone of a fast and accurate diagnosis of this condition. Management of active tuberculosis in the elderly does not differ fundamentally from that in younger patients with respect to outcomes or adverse effects of treatment. However, empirical treatment perhaps may be considered more readily in the elderly patient. Elderly persons infected with tuberculosis at the beginning of the 20th century constitute a large reservoir of latent tuberculosis infection. Furthermore, these individuals are at increased risk of reactivation of this remote infection as their immunological status declines with aging. Compared with the past, modern guidelines are less reluctant to recommend use of tuberculin skin testing, treatment of latent tuberculosis infection in elderly persons, and prevention of transmission of tuberculosis in nursing homes.

Mycobacterium tuberculosis diverts alpha interferon-induced monocyte differentiation from dendritic cells into immunoprivileged macrophage-like host cells

Dendritic cells (DCs) are critical for initiating a pathogen-specific T-cell response. During chronic infections the pool of tissue DCs must be renewed by recruitment of both circulating DC progenitors and in loco differentiating monocytes. However, the interaction of monocytes with pathogens could affect their differentiation. Mycobacterium tuberculosis has been shown to variably interfere with the generation and function of antigen-presenting cells (APCs). In this study we found that when alpha interferon (IFN-alpha) is used as an inductor of monocyte differentiation, M. tuberculosis inhibits the generation of DCs, forcing the generation of immunoprivileged macrophage-like cells instead. Cells derived from M. tuberculosis-infected monocyte-derived macrophages (M. tuberculosis-infected MoMphi) retained CD14 without acquiring CD1 molecules and partially expressed B7.2 but did not up-regulate B7.1 and major histocompatibility complex (MHC) class I and II molecules. They synthesized tumor necrosis factor alpha and interleukin-10 (IL-10) but not IL-12. They also showed a reduced ability to induce proliferation and functional polarization of allogeneic T lymphocytes. Thus, in the presence of IFN-alpha, M. tuberculosis may hamper the renewal of potent APCs, such as DCs, generating a safe habitat for intracellular growth. M. tuberculosis-infected MoMphi, in fact, showed reduced expression of both signal 1 (CD1, MHC classes I and II) and signal 2 (B7.1 and B7.2), which are essential for mycobacterium-specific T-lymphocyte priming and/or activation. These data further suggest that M. tuberculosis has the ability to specifically interfere with monocyte differentiation. This ability may represent an effective M. tuberculosis strategy for eluding immune surveillance and persisting in the host.

Approaches towards the development of a vaccine against tuberculosis: recombinant BCG and DNA vaccine

The last few years have witnessed intense research on vaccine development against tuberculosis. This has been driven by the upsurge of tuberculosis cases globally, especially those caused by multi-drug-resistant Mycobacterium tuberculosis strains. Various vaccine strategies are currently being developed which can be broadly divided into the so-called living and non-living vaccines. Examples are attenuated members of the M. tuberculosis complex, recombinant mycobacteria, subunit proteins and DNA vaccines. Given current developments, we anticipate that recombinant BCG and DNA vaccines are the most promising. Multiple epitopes of M. tuberculosis may need to be cloned in a vaccine construct for the desired efficacy to be achieved. The technique of assembly polymerase chain reaction could facilitate such a cloning procedure.

Clinical diagnosis of smear-negative pulmonary tuberculosis in low-income countries: the current evidence

Sputum smear examination for acid-fast bacilli (AFB) can diagnose up to 50-60% of cases of pulmonary tuberculosis in well-equipped laboratories. In low-income countries, poor access to high-quality microscopy services contributes to even lower rates of AFB detection. Furthermore, in countries with high prevalence of both pulmonary tuberculosis and HIV infection, the detection rate is even lower owing to the paucibacillary nature of pulmonary tuberculosis in patients with HIV infection. In the absence of positive sputum smears for AFB, at primary care level, most cases of pulmonary tuberculosis are diagnosed on the basis of clinical and radiological indicators. This review aims to evaluate various criteria, algorithms, scoring systems, and clinical indicators used in low-income countries in the diagnosis of pulmonary tuberculosis in people with suspected tuberculosis but repeated negative sputum smears. Several algorithms and clinical scoring systems based on local epidemiology have been developed to predict smear-negative tuberculosis. Few of these have been validated within the local context. However, in areas where smear-negative tuberculosis poses a major public-health problem, these algorithms may be useful to national tuberculosis programmes by providing a starting point for development their own context-specific diagnostic guidelines.

[Assessment of nurses' understanding of tuberculin testing at a general hospital]

BACKGROUND

The last ten years have seen a resurgence of tuberculosis, yet little information is available about the implementation of tuberculin testing and consistency in its use and interpretation.

OBJECTIVE

To evaluate knowledge of tuberculin testing among hospital nurses.

MATERIAL AND METHOD

A questionnaire on various aspects of the tuberculin test was administered to registered nurses assigned to various services of our university hospital. The questions were grouped by sections (techniques for administering the test, reading the results and interpreting them).

RESULTS

One hundred thirty-five nurses were surveyed; 127 (94%) answered all the questions. Overall, only 42% responded to 10 or more of the 14 items on the questionnaire. By sections, questions related to technique of administration, reading the tuberculin test result and interpreting it were answered correctly by 46%, 11% and 7% of the subjects, respectively. Only two variables were independently related to the number of correct responses: 1) working on a medical ward at the time of the survey or 2) administering the test more than once a week.

CONCLUSIONS

This study confirms that hospital nurses' understanding of tuberculin testing is unacceptable. A team of professionals skilled in tuberculin testing should be designated at every level of the health care system to assure the reliability of tests performed for clinical or research purposes.

Ocular tuberculosis

Despite the use of highly sensitive molecular tools, such as polymerase chain reaction, for the detection of Mycobacterium tuberculosis, ocular tuberculosis remains a subject of controversy. The diagnosis is often presumptive in the absence of ocular biopsies. Choroiditis is the most common ocular manifestation in patients with pulmonary and systemic tuberculosis. Indocyanine green angiography seems to be an interesting method to determine choroidal involvement. PCR technology is proposed to evaluate the presence of the tubercule bacillus DNA in ocular fluids and tissues when conventional microbiologic methods fail to confirm a bacterial etiology. Most of the presumed cases of ocular tuberculosis should be treated with associations of antituberculous drug, especially when a systemic steroid regimen is required.