- M. tuberculosis EM photo
Editorial Group:
Dr John Thompson Canberra
Prof Adrian Sleigh Australian National University, Canberra
A/Prof Paul Kelly Australian National University, Canberra
Address for correspondence
Email: jtjnj@actewagl.net.au
Forthcoming Conferences
40th Union World Conference on Lung Health; 3-7 December 2009
Cancun, Mexico,
Contact: cancun2009@theunion.org
2nd Conference of the Union Asia Pacific Region 9-12 September 2009 Beijing
Contact: mail@iiuatld-apr.com
International Tuberculosis Course
31 August-18 September 2009-04-19 Hanoi, Vietnam
Contact: tb-lunghealth-courses@theunion.org
In this Edition
Editorial P 1 – 2
Microbiology P 2 – 3
Prevention and Control P 3 – 5
Infection P 5 – 6
TB and HIV P 6 – 7
Cell Biology P 7
Pharmacology P 7
Extra-Pulmonary TB P 8
Risk Factors P 9
Diagnosis P 10
Treatment P 10 – 11
Drug Resistance P 11
Population Studies P 11 – 12
Editorial
It is remarkable that 127 years have passed since Ziehl and in the following year Neelsen provided us with their test to identify M. tuberculosis, yet despite advances in other microbiological techniques, it still remains basic to finding acid fast bacilli. In most countries it remains the one criterion whereby TB is diagnosed or not. In those countries that can afford them, radiometric broth techniques have greatly advanced the isolation of M. tuberculosis on culture, while nuclear amplification has revolutionised the detection and differentiation of all mycobacteria.
But studies are still being published which seek to modify the ZN technique, particularly for poor countries. This is not just for the purpose of reducing cost also to reduce the persisting high error rate in interpretation, from which small laboratories in low incidence countries are not immune. We know that the fluorescent detection of AFB using an auramine stain is significantly superior, yet it is far from standard even in high income countries. In resource limited countries as we now call them, the cost of fluorescent microscopes severely limits their use even though there is now evidence that an increased detection rate leading to cure of more cases of TB and less transmission can more than compensate in cost for this equipment.
The prevention of contamination of TB cultures by non-mycobacteria still exists and bedevils the interpretation of drug trials where sputum culture conversion is seen as an endpoint. The study from Brazil on page 7 exemplifies this. We have not yet perfected the perfect decontamination method whereby all non-mycobacteria are destroyed but not a single Mycobacterium tuberculosis.
Thirdly we have not yet eradicated cross-contamination by another patient’s tubercle bacilli from our laboratories as the study from Marseilles tells us on page 2. Indeed the increasing use of nuclear amplication techniques across a wider range of laboratories will almost certainly see more cross contamination and more false positives. Only strong regulatory processes from a central authority together with inter-laboratory quality control measures can limit these problems. Australia is fortunate that such regulations are in place, but every clinician should be aware of whether the laboratory to which they send specimens, has the capacity for as little error as possible in processing and identifying M. tuberculosis. Once again good clinical practice dictates that no diagnosis should be made on the laboratory result alone.
Microbiology:
Fluorescent microscopy is less expensive than Ziehl-Neelsen microscopy in Thailand.
Sohn et al Nonthaburi, Thailand
Int J Tuberc Lung Dis 2009; 13: 266
Summary: Ziehl-Neelsen (ZN) microscopy is the primary method for acid-fast bacilli examination in resource–limited settings, including Thailand. Despite its considerably improved diagnostic performance, conventional fluorescent microscopy (FM) is rarely used due to its perceived high cost. An evaluation in Thailand found that the total cost of FM operated in thew National Tuberculosis Reference Laboratory (NTRL) in Bangkok, Thailand, is similar to that of ZN performed in the NTRL, and in four regional Thai laboratories. FM is therefore a cost effective alternative to ZN in resource –limited settings,
Comment: If these findings could be replicated at district level, case detection would be significantly enhanced.
JT
Evaluating the performance of basic fuchsin for the Ziehl-Neelsen stain.
Gordon et al Adelaide, South Australia, Paris, France
Int J Tuberc Lung Dis 2009; 13: 130
Setting: An investigation of commercially available basic fuchsin (BF) dye powders used for the detection of acid-fast bacilli (AFB).
Objective: to determine whether single or multiple assays may predict the performance of BF in the Ziehl-Neelsen (ZN) method.
Design: The composition and staining properties of six BF dye samples were assessed using continuous recording spectrophotometry, reverse phase thin-layer chromatography (RPTLC) and a standardised ZN biological staining test.
Results: Variable proportions of BF homologues could be demonstrated in the sample, but neither spectroscopy nor RPTLC was fully predictive of their staining quality. ZN staining of standard smears was needed to identify five powders that yielded satisfactory results and one powder with unsatisfactory performance. Increasing the BF concentration did not always result in improved staining.
Conclusions: Simple analytical methods, such as spectrophotometry and RPTLC , should be complemented by biological staining of control smears to assess the quality of BF dye powders. This allows tuberculosis control programmes to avoid procurement of BF dyes that would fail to detect AFB even when strictly adhering to current international guidelines for ZN staining.
Comment: Quite!
JT
Rapid detection of laboratory cross-contamination with Mycobacterium tuberculosis using multispacer sequence typing
Djelouadji et al Marseilles France
BMC Microbiol 2009; 9: 47
Background: The ability to culture Mycobacterium tuberculosis from clinical specimens serves as the gold standard for the diagnosis of tuberculosis. However, a number of false-positive diagnoses may be due to cross-contamination of such specimens. We herein investigate such episodes of cross-contamination by using a technique known as multispacer sequence typing (MST). This technique was applied to six M. tuberculosis isolates prepared within the same laboratory over a two-week period of time.
Results: MST analysis indicated a unique and common sequence profile between a strain isolated from a patient with proven pulmonary tuberculosis and a strain isolated from a patient diagnosed with lung carcinoma. Using this approach, we were able to provide a clear demonstration of laboratory cross-contamination within just four working days. Further epidemiological investigations revealed that the two isolates were processed for culture on the same day.
Conclusion: The application of MST has been demonstrated to serve as a rapid and efficient method to investigate cases of possible cross-contamination with M.tuberculosis.
Comment: We need all the tools we can get to identify cross-contamination.
JT
Fluoromycobacteriophages for rapid, specific and sensitive antibiotic testing of Mycobacterium tuberculosis.
Piuri et al Pittsburgh Pn USA
PLoS ONE 2009; 4: e4870
Summary: Rapid antibiotic susceptibility testing of Mycobacterium tuberculosis is of paramount importance as multiple and extensively –drug resistant strains of M tuberculosis emerge and spread. We describe here a virus-based assay in which fluoromycobacteriophages are used to deliver a GFP or Zs Yellow fluorescent marker gene to M. tuberculosis, which can then be monitored by fluorescent detection approaches including fluorescent microscopy and flow cytometry. Pre-clinical evaluations show that the addition of either Rifampicin or Streptomycin at the time of the phage addition obliterates fluorescence in susceptible cells but not in isogenic resistant bacteria enabling drug sensitivity in less than 24 hours. Detection requires no substrate addition, fewer than 100 cells can be identified, and resistant bacteria can be detected within mixed populations. Fluorescence withstands fixation by paraformaldehyde providing enhanced biosafety for testing MDR-TB and XDR-TB infections.
Comment: Will the need for a fluorescent microscope or more so a flow cytometer limit the use of this technique.
JT
Nontuberculous mycobacteria among patients who are suspected for multidrug-resistant tuberculosis-need for earlier identification of nontuber-culosis mycobacteria.
Tabarsi et al Teheran Iran
Am J Med Sci 2009; 337: 182
Background: In this study, we intended to find the prevalence of nontuberculosis mycobacteria (NTM) among patients who are referred as suspected multidrug-resistant tuberculosis (MDR-TB) cases to the only referral centre in Iran.
Methods: All patients referred to our center in 2002-2006 as MDR-TB with histories of treatment with standard and CATll World Health Organisation regimens were included in the study. Sputum smear and culture for acid-fast bacilli were performed for all patients 3 times. Sputum polymerase chain reaction was also performed for all patients. Mycobacterial identification was performed via polymerase chain reaction and routine identification tests for all culture-positive cases
Results: of the 105 patients in the study, 12 (11.4%) were identified to have NTM infection. The identified mycobacteria were classified in order of prevalence as Chelonae (8 cases), Simiae (2 cases), Aloei (1 case), and Farcinogen (1 case). Based on radiologic findings most of the cases demonstrated bilateral nodularity (83.3%) and also multifocal bronchiectasis (75%). Notably, cavitary lesions were present in 41.7% of the cases.
Conclusion: Based on the findings of this study, it is essential that such cases be identified before commencing MDR-TB treatment.
Comment: Are we to believe that in regional Iran, treatment decisions are made on sputum smear positivity alone? If so those with NTM disease caused by drug sensitive organisms eg M. kansasii would pass unnoticed.
JT
Prevention and Control
Preventive chemotherapy. Where has it got us? Where to go next?
Landry et al Montreal Canada
Int J Tuberc Lung Dis 2008; 12: 1352
Summary: The World Health organization estimates that a third of the world’s population is infected with Mycobacterium tuberculosis. Every second, one person becomes newly infected with tuberculosis (LTBI). In the past two decades, the spread of human immunodeficiency virus infection, worsening poverty and deteriorating health services have resulted in a steady increase in the overall incidence
Of TB globally. With treatment of LTBI, the number of infected persons who develop activeTB can be significantly reduced. Prevention through treatment of LTBI should therefore be an integral part of the control of TB.
Although only a minority of those with LTBI will develop active disease, the risk varies substantially according to the time since infection and medical risk factors. If persons at low risk for TB are selected for preventive chemotherapy, the individual and public health benefits are low, and a large number will have to be treated to prevent a single active case. It is therefore important to identify and treat patients who are high risk of disease.
Tools for rapid and reliable identification of persons with LTBI who are most likely to progress to active disease are urgently needed, as this will permit rational use of preventive treatment by restricting treatment to those patients with the most favourable risk/benefit ratio. The major challenges are efficient identification of those at highest risk of developing disease and ensuring treatment completion with a non-toxic regimen. If these can be overcome, preventive treatment holds the promise to substantially assist in the achievement of global control of TB.
Comment Recommended reading, although more emphasis should be given to realising that the larger the Mantoux reaction or the greater the release of IFN y, the greater the risk.
JT
Isoniazid completion rates for latent tuberculosis infection among college students managed by a community pharmacist.
Hess et al Pomona CA USA
J Am Coll Health 2009; 57: 553
Objective: The authors’ objective was to document 9-month and previously recommended 6-month treatment completion rates for latent tuberculosis infection (LTBI) in a pharmacist –managed LTBI clinic in a community pharmacy on a college campus, and to describe patient characteristics.
Participants: Participants were university students diagnosed with LTBI.
Methods: The authors conducted a retrospective review of pharmacy records from 2000 to 2006. Main outcome measures included 6-month and 9-month LTBI treatment completion rates, total isoniazid (INH) tablets taken, characteristics of completers versus noncompleters, average time to treatment completion and reported adverse drug events.
Results: The 9-month completion rate was 59 %, and the 6-month completion rate was 67 %. Among those not completing treatment, 15.2% experienced fatigue and 2.2 % experienced a rash (p=0.04 and p= 0.03, respectively).
Conclusion: LTBI clinics are a unique niche for community pharmacies and can provide individualised patient care to ensure LTBI treatment adherence, monitoring for disease progress and safety of isoniazid.
Comment: These completion rates might exceed the usual 50% but they are not all that encouraging.
JT
Inadequate ventilation for nosocomial tuberculosis prevention in public hospitals in central Thailand
Jiamjarasrangsi et al Bangkok Thailand
Int J Tuberc Lung Dis 2009; 13:454
Setting: Forty-two community and general hospitals in central Thailand.
Objective: To examine the adequacy of indoor ventilation for nosocomial tuberculosis (TB) prevention in public hospitals in central Thailand.
Design: A cross-sectional survey was conducted among 323 patient care and ancillary areas in the target hospitals. Data on indoor ventilation rate were collected by the tracer gas method and reported as air changes per hour (ACH). The adequacy of the measured ventilation rates were then determined by comparison with the international recommended standard values.
Results: Indoor ventilation rates were inadequate in almost half the studied areas ( 144/323, 44.6%). The inadequacy was particularly serious in the emergency rooms (ERs) and radiological areas, where 73.8 % (31/42 each) of the rooms had ACH below the recommended standards. Detailed analysis showed that most of the rooms with natural ventilation had air exchange rates that exceeded the recommended standards, while the opposite was the case for rooms with air-conditioning, particularly the window or wall-mount type.
Conclusion: Indoor ventilation in high risk nosocomial TB areas in public hospitals in Thailand was inadequate due to the installation of airconditioning systems in modern buildings.
Comment: Yet another study where the message is loud and clear. If the climate allows it, design hospitals with high ceilings and lots of open window space; otherwise spend large amounts on the best exhaust ventilation airconditioning money can buy.
JT
Impact of tuberculosis preventive therapy on tuberculosis in HIV-infected children
Gray et al Cape Town South Africa
Cochrane Database Syst Rev 2009; Jan 21; (1): CD006418
Background: Children with HIV are at increased risk of acquiring tuberculosis (TB), a common cause of acute and chronic respiratory disease and death in HIV-infected children living in areas where prevalence of the disease is high. Children infected with HIV and TB have worse outcomes than HIV-uninfected children who have TB; thus preventing the infection and disease in HIV-infected children is potentially an important public health intervention. Isoniazid, an anti-tuberculosis medication, has been used effectively to prevent TB in HIV-uninfected children, but currently there are no guidelines on the use of TB preventive therapy in HIV-infected children.
Objectives: To determine the impact of TB preventive therapy on TB-related incidence and death in HIV-infected children.
Search Strategy: We searched the Cochrane Controlled Trials Register (CENTRAL/CCTR), Cochrane HIV/AIDS Group Specialized Register, Medline/PubMed, EMBASE and AIDSearch. In addition, we scanned reference lists, manually searched conference abstracts, and contacted content experts.
Selection Criteria: We included studies of HIV-infected children randomised to receive TB preventive therapy or placebo, or an alternative TB preventive regimen. Participants could have a tuberculin test that was positive or negative..
Data Collection and Analysis: Two authors independently used the study selection criteria, assessed methodological quality and extracted data. Effects were assessed using hazard ratios.
Main results: One trial met the selection criteria for the review. The trial participants were HIV-infected children, most of whom were not taking antiretroviral therapy. Subjects were randomised to isoniazid and cotrimoxazole or placebo and tricomoxazole given daily or three times a week. The trial showed a marked reduction in TB incidence and death in the isoniazid group. As yet, however, there were no long term follow-up data on the durability of the protective effect or on possible long-term adverse events. This trial was unable to assess the impact of isoniazid prophylaxis on children receiving antiretroviral therapy.
Authors’ Conclusions: Isoniazid prophylaxis in HIV-infected children has the potential to play a major public health role by reducing TB incidence and death. As yet, however, data are insufficient to guide the duration of prophylaxis and to support its use in children using highly active antiretroviral therapy (HAART) and in those living in areas of low TB prevalence. Further studies are needed to assess whether TB preventive therapy is of benefit in all HIV-infected children, irrespective of use of antiretroviral treatment, the optimal duration of preventive therapy, or long term adverse events.
Comment: Nor do we know if the tuberculin status determines the outcome, particularly in regions of low TB prevalence.
JT
Infection
Comparison of QuantiFERON Gild In-Tube test and tuberculin skin test for identification of latent Mycobacterium tuberculosis infection in healthcare staff and association between positive test results and known risk factors for infection.
Vinton et al Melbourne Australia
Infect Control Hosp Epidemiol 2009; 30: 215
Objective: We compared a whole-blood interferon gamma release assay (QuantiFERON-TB Gold In-Tube test, hereafter “ QFT –in-tube test”) with a tuberculin skin test (TST) to determine which test more accurately identified latent Mycobacterium tuberculosis infection in healthcare staff.
Methods: A total of 481 hospital staff members were recruited from 5 hospitals in Melbourne ,Australia. They provided information about demographic variables and tuberculosis (TB) risk factors )i.e. birth or travel to a country with a high prevalence of TB, working in an occupation likely to involve contact with M.tuberculosis, or individuals with TB, or being a household contact of an individual with proven pulmonary TB.) The QFT-in tube test and the TST were administered in accordance with standardised protocols. Concordance between the test results was analysed using the kappa statistic, the McNemar test and logistic regression.
Results: A total of 358 participants had both a TST result and a QFT-in tube test result available for comparison. There were fewer positive QFT-in tube test results than positive TST results (6.7 % vs. 33.0%; P< .001). Agreement between the tests was poor (71%; kappa=0.16). A positive QFT-in tube test result was associated with birth in a country with a high prevalence of TB, the number of years an individual had lived in a country with a high prevalence of TB (i.e., the effect of each additional year, treated as a continuous variable), and high-risk occupational contact. A contact TST result was associated with older age, receipt of bacille Calmette-Guerin (BCG) vaccination, and working in an occupation that involved patient contact. Receipt of BCG vaccination was most strongly associated with discordant results in instances in which the TST result was positive and the QFT-in tube test result was negative.
Conclusion: In a population of healthcare staff with a low prevalence of TB and a significant rate of BCG vaccination, a positive QFT-in tube test result was associated with the presence of known risk factors for TB exposure, whereas a positive TST result was more strongly associated with a prior history of BCG vaccination.
Comment: There is no doubt QFT tests are more specific for detection of TB infection if the subject has received BCG. However their conclusion does not match their findings that those staff in contact with a tuberculous patient are more likely to have a positive TST result. It looks as if a negative QFT test will have to be followed by a TST and that 15 mm or more of induration will confirm infection.
JT
TB and HIV
HIV/AIDS: Immune reconstitution inflammatory syndrome: a reappraisal.
French M Perth Western Australia
Clin Infect Dis 2009; 1: 101
Summary: Individuals with human immunodeficiency virus infection who commence antiretroviral therapy when they are very immunodeficient are susceptible to immune reconstitution disorders. The most common disorders are the various forms of immune restoration disease (IRD) that appear to result from the restoration of a dysregulated immune response against pathogen specific antigens. Essentially, any pathogen that can cause an opportunistic infection as a result of cellular immunodeficiency can provoke IRD when pathogen-specific immune responses recover during antiretroviral therapy. In resource-poor countries, Mycobacterium tuberculosis and Cryptococcus neoformans are the most significant pathogens, because the former causes substantial morbidity and the latter substantial mortality. IRD associated with these pathogens is characterized by severe inflammatory responses and is often referred to as immune reconstitution inflammatory syndrome. Prevention and treatment strategies for IRD are being developed, but preliminary data have demonstrated the efficacy of corticosteroid therapy in sever cases. Immune reconstitution after antiretroviral therapy may also be associated with autoimmune disease or sarcoidosis, both of which appear to have an immunopathogenesis that is different from that of IRD.
Comment: A little more emphasis on delaying the introduction of antiretroviral therapy in cases with TB, would be helpful
JT
Timing of antiretroviral therapy initiation in tuberculosis patients with AIDS: a decision analysis.
Schiffer et al Seattle USA
J Acquir Immune Def Synd 2009; 44: 229
Summary: In HIV-infected tuberculosis patients with < 200 CD4 lymphocytes /cmm, highly active antiretroviral therapy (HAART) improves survival but can be complicated by immune reconstitution inflammatory syndrome (IRIS) and drug toxicity. We conducted a decision analysis in hypothetic cohorts of 1000 patients in which HAART was initiated during the first 2 months of antituberculosis therapy (early) or during months 2 through 6 of tuberculosis therapy (deferred) or was withheld until after tuberculosis therapy (no HAART). Out comes assessed were 1-year mortality and the combined outcome of 1-year mortality, new AIDS-defining illness, severe IRIS and severe drug toxicity. There 33, 48 and 147 deaths and 497, 501 and 501 combined outcome events in the early HAART, deferred HAART and no-HAART groups, respectively ; most events were drug toxicity in the early and deferred groups and HIV –related mortality or AIDS defining illness in the no-HAART group. In a 2-way sensitivity analysis of mortality , early HAART was favoured , even with the highest reported rates of IRIS (70%) and severe drug toxicity (56%). Deferred HAART as favoured over early HAART only if the IRIS-related mortality in the early group exceeded 4.6 %. These results support early initiation of HAART in patients with AIDS, except where IRIS-related mortality rates are high.
Comment: Should we compromise by delaying antiretroviral treatment for a month?
JT
Approaches to tuberculosis screening and diagnosis in people with HIV in resource-limited settings.
Reid et al New York USA
Lancet Infect Dis 2009; 9: 173
Summary: Tuberculosis is the main cause of morbidity and mortality in people living HIV/AIDS worldwide. Early diagnosis and treatment is essential in addressing the dual epidemic of tuberculosis and HIV. Increasing recognition of the importance of integrating tuberculosis services-including screening-into HIV care has led to global policies and the beginnings of implementation of activities at national level. However, debate remains about the best methods of screening for pulmonary tuberculosis among people living with HIV/AIDS in resource-limited settings. Mycobacterial culture, the gold standard for tuberculosis diagnosis, is too slow and complex to be a useful screening test in such settings. More widely available methods, such as symptom screening, sputum smear microscopy, chest radiography and tuberculin skin testing have important shortcomings, especially in people living with HIV/AIDS. However, until cheaper, simpler and more sensitive diagnostics for tuberculosis are available in peripheral healthcare settings., a strategy must be developed that uses current evidence to combine available screening tools.
Comment: In Australia our services are not integrated to the extent that we don’t know how many notified cases of TB are HIV positive.
JT
Cell Biology
How B cells shape the immune response against Mycobacterium tuberculosis
Maglione et al New York USA
Eur J Immunol 2009; 39: 676
Summary: Extensive work illustrating the importance of cellular immune mechanisms for protection against Mycobacterium tuberculosis has largely relegated B-cell biology to an afterthought within the tuberculosis (TB) field. However, recent studies have illustrated that B lymphocytes , through a variety of interactions with the cellular immune response, play previously underappreciated roles in sharing host defence against non-viral intracellular pathogens, including M.tuberculosis. Work in our laboratory has recently shown that, by considering these lymphocytes more broadly within their variety of interactions with cellular immunity, B cells have a significant impact on the outcome of airborne challenge with M. tuberculosis as well as the resultant inflammatory response. In this review we advocate for a revised view of TB immunology in which roles of cellular and humoral immunity are not mutually exclusive. In the context of our current understanding of host defence against non-viral intracellular infections, we review recent data supporting a more significant role of B cells during M. tuberculosis infection than previously thought.
Comment: Yet we have been singularly unsuccessful in finding specific immunoglobulins either for the diagnosis of TB or for protection against it.
JT
Cutinase -like proteins of Mycobacterium tuberculosis: characterization of their variable enzymatic functions and active site identification.
West et al Sydney, Australia, Wuxi, China, Bethesda, USA
FASEB J 2009; Feb 18
Summary: Discovery and characterization of novel secreted enzymes of Mycobacterium tuberculosis are important for understanding the pathogenesis one of the most important human bacterial pathogens. The proteome of M. tuberculosis contains over 400 potentially secreted proteins , the majority of which are uncharacterised. A family of seven cutinase-like proteins (CULPs) was identified by bioinformatic analysis, expressed and purified from Escherichia coli, and characterized in terms of their enzymatic activities. These studies revealed a functional diversity of enzyme classes based on differential preferences for substrate chain length. One member, CULP1, exhibited strong esterase activity, 40-fold higher than that of CULP6, which had strong activity as a lipase. Another, CULP4, performed moderately as an esterase and weakly as a lipase. CULP6 lipase activity was optimal above ph7, and fully maintained to ph5. None of the CULP members exhibited cutinase activity. Site-directed mutagenesis of each residue of the putative catalytic triad in CULP6 confirmed that each was essential for activity toward all fatty acid chain length of nitrophenol esters and lipolytic function. CULP1 and CULP2 were present only in culture supernatants of M tuberculosis., while CULP6, which is putatively essential for mycobacterial growth, was retained in the cell wall, suggesting the proteins play distinct roles in Mycobacterial biology.
Comment: But will any of them prove to be the weak links in attempts to destroy the organism and cure the person?
JT
Pharmacology
Meropenem-clavulanate is effective against extensively drug-resistant Mycobacterium tuberculosis.
Hugonnet et al New York USA
Science 2009; 323: 1215
Summary: Beta-lactam antibiotics are ineffective against Mycobacterium tuberculosis, being rapidly hydrolysed by the chromosomally encoded blaC gene product. The carbapenem class of beta-lactams are very poor substrates for blaC, allowing us to determine the three-dimensional structure of the co-valent blaC-meropenem covalent complex at 1.8 angstrom resolution. When meropenem was combined with the beta-lactamase inhibitor clavulanate, potent activity against laboratory strains of M. tuberculosis was observed [MIC {meropenem) less than 1 mcg /ml], and sterilization of aerobically cultures was observed within 14 days. In addition, this combination exhibited inhibitory activity against anaerobically grown cultures that mimic the “persistent” state and inhibited the growth of 13 extensively drug-resistant strains of M. tuberculosis at the same levels seen for drug-susceptible strains. Meropenem and clavulanate are Food and Drug Administration-approved drugs and could be potentially used to treat patients with currently untreatable disease.
Comment: In combination, of course.
JT
Extra-Pulmonary Tuberculosis
Differentiating intestinal tuberculosis from Crohn’s disease: a diagnostic challenge.
Almadi et al Montreal Canada
Am J Gastroenterol 2009; 104: 1003
Summary: With the changing epidemiology of Crohn’s disease (CD) and intestinal tuberculosis (ITB), we are in an era where the difficulty facing physicians in discriminating between the two diseases has increased, and the morbidity and mortality resulting from a delayed diagnosis or misdiagnosis is considerably high. In this article we examine the changing trends in the epidemiology of CD and ITB, in addition to clinical features that aid in the differentiation of both diseases. The value of various laboratory, serological and tuberculin skin tests are reviewed as well. The use of an interferon-gamma-release assay, QuantiFERON-TB-Gold, in the work up of these patients and its value in populations where the bacillus Calmette-Guerin vaccine is still administered is discussed. Different radiological, endoscopic, and pathological similarities and features that can aid the clinician in reaching a rapid diagnosis are reviewed as well. The association between mycobacteria and CD, the concerns with the practice of antituberculosis medication trials in areas where tuberculosis (TB) is endemic, as well as the extrapulmonary TB induced by the use of antitumour necrosis factor-alpha agents are delineated in this article. Furthermore, we propose an algorithm for the investigation of patients in whom the differential diagnosis encompasses CD and ITB.
Comment: A timely review: as migrants and refugees continue to enter wealthy countries, so there will be more patients with intestinal tuberculosis.
JT
Pancreatic tuberculosis: a clinical and imaging review of 32 cases.
Nagar et al Mumbai India
J Comput Assist Tomogr 2009; 33: 136
Background: Tuberculosis of the pancreas is a rare entity, and anecdotal reports describing imaging features of pancreatic tuberculosis have been described in medical literature. The imaging features include computed tomography (CT) and ultrasonography in diagnosed cases of tubercular involvement of the pancreas are described, with an overview of clinical features and laboratory investigations.
Materials and Methods: We analysed records of 384 patients of diagnosed cases of abdominal tuberculosis for involvement of pancreas and detected 32 patients (8.33%) who had pancreatic involvement. This included 22 men and 10 women with an age range of 19 to 64 years ( mean age of 42,5 years) who were detected to have pancreatic from 1999 to 2004 in our institute. We reviewed the clinical, radiologic (ultrasonographic and CT features) and laboratory findings of all patients. The criteria for diagnosis of tuberculosis was based on ascitic fluid adenosine deaminase level in 14 patients, fine needle aspiration cytology of lymph nodes in 9 patients and the presence of pulmonary tuberculosis in 9 patients.
Results: The duration of symptoms spanned between 2 and 11 months, with a mean of 6 months. The most common symptom was abdominal pain localized to the epigastrium. Sixteen patients were HIV positive. Fourteen patients had a history of tuberculosis of the lungs, whereas 18 patients had pancreatic and peripancreatic involvement as the primary manifestation. Ultrasonography showed bulky inhomogeneous pancreas in 5 patients; solitary or multiple hypoechoic collections were observed in 7 and 20 patients respectively. CT findings demonstrated hypodense collections within the pancreas associated with peripancreatic lymphadenopathy in 29 patients. Three patients had a complex pancreatic mass lesion.
Conclusions: Pancreatic tuberculosis can present with a variable spectrum of imaging findings. Tuberculosis of the pancreas should be considered as a diagnostic possibility in patients who present with a pancreatic space occupying lesion associated with peripancreatic lymphadenopathy.
Comment: It seems that if you can’t diagnose tuberculosis elsewhere in the abdomen, there is no point looking for pancreatic involvement. This article seems to tell us that finding pancreatic TB won’t influence treatment anyway.
JT
Risk Factors
Tuberculosis and substance abuse in the United States, 1997-2006.
Oeltmann et al CDC Atlanta USA
Arch Intern Med 2009; 169: 189
Background: Tuberculosis (TB) control efforts are often ineffective in controlling TB among patients who use illicit drugs or abuse alcohol (substance abuse). This study examined the prevalence of substance abuse among TB cases reported in the United States and assessed the relationship between substance abuse and indicators of TB transmission.
Methods: A cross-sectional analysis was performed of data on US TB cases in patients 15 years or older reported from 1997 through 2006. Analyses included number and proportion of patients with TB characterized by substance abuse and associations between substance abuse, sputum smear status, treatment failure and inclusion in a county-level genotype cluster.
Results: Of 153,268 patients with TB, 28650 (18.7%) reported substance abuse, including 22,293 of 76,816 US born patients (29%). Multivariate analysis showed that, among patients negative for human immunodeficiency virus, odds of sputum smear-positive disease were 1.8 ( 99% CI, 1.7-1.9) times greater among those who reported substance abuse; this association was weaker among patients with human immunodeficiency virus infection (OR, 1.2; 99%CI, 1.1-1.4). Among female patients, odds of treatment failure were 2.4 (99% CI, 1.9-3.0) times greater among those who reported substance abuse. The association was weaker among male patients ( OR, 1.5; 99% CI, 1.3-1.7). Patients who abused substances were more likely to be involved in a county-level genotype cluster (US-born: OR, 2.3; 99% CI, 2.0-2.7; foreign-born: 1.5; 1.2-2,0).
Conclusions: Substance abuse is the most commonly reported behavioural risk factor among patients with TB in the United States. Patients who abuse substances are more contagious (smear positive) and remain contagious longer because treatment failure presumably extends periods of infectiousness. Increased transmission is consistent with our finding that patients who abuse substances were more likely to be involved in a localized genotype cluster, which can represent recent transmission.
Comment: This risk factor is going to be with us for a long time both in the US and Australia.
JT
Human genetic influence on susceptibility of tuberculosis: from infection to disease.
Cheepsattayakorn et al Bangkok Thailand
J Med Assoc Thai 2009;92: 136
Summary: There is substantial evidence from studies on racial variation in susceptibility to tuberculosis (TB) that human genetic variation is an important determinant of the outcome of infection with Mycobacterium tuberculosis (Mtb). In only a minority of cases is there an obvious identifiable risk factor such as human immunodeficiency virus (HIV) infection, advanced age, diabetes, corticosteroid usage or alcohol abuse. In the remainder, a complex interaction of genetic and environmental factors causes the development of clinical TB. Assessment of the contribution of genetics of host resistance to human TB is a long standing challenge of human genetic research. Several studies demonstrated the association of various human leukocyte antigens (HLA) with disease susceptibility in different ethnic populations. There are likely to be many more TB-susceptibility genes to be identified.
Comment: Very true, but let us not forget poverty as a major risk factor.
JT
Impact of diabetes mellitus on treatment outcomes of patients with active tuberculosis.
Dooley et al Baltimore Md USA
Am J Trop Med Hyg 2009; 80: 634
Summary: Diabetes mellitus (DM) is an emerging chronic health condition of developed and developing countries. We conducted a retrospective cohort study of patients with active , culture-confirmed tuberculosis (TB) in Maryland to determine the impact of DM on TB treatment outcomes. Of 297 TB patients, 42 (14%) had DM. Patients with DM has 2.0 times higher odds of death than patients without DM (95% CI,0.74-5.2, P=0.18). Adjusting for human immunodeficiency virus (HIV), age, weight, and foreign birth, the odds of death were 6,5 times higher in patients with DM than patients without DM. (median 49 vs 39 days, P=0.039). In pulmonary TB patients, time to sputum culture conversion was longer in patients with DM than in patients without DM (Median 39 vs 29 days, P=0.09). Two month culture conversion proportions were similar (70% and 69%). Treatment failure occurred in 4.1% of patients without DM and 6.7% of patients with DM (P=0.51). In conclusion, DM was a risk factor for death in Maryland TB patients. There was a trend toward increased time to sputum conversion; two month culture conversion proportions were, however, similar.
Comment: Greater numbers are needed before it is possible to have confidence in these findings.
JT
Diagnosis
Pleural fluid adenosine deaminase and interferon gamma as diagnostic tools in tuberculous pleurisy.
Krenke et al Warsaw Poland
J Physiol Pharmacol 2008; 59: 349
Summary: Several biological markers have been proposed to improve the efficacy of diagnosing tuberculous pleurisy. The study was undertaken to evaluate the accuracy of pleural fluid adenosine deaminase (ADA) activity and interferon-gamma (IFN-gamma) in differentiating tuberculous pleural effusion (TPE) and non-tuberculous pleural effusion (non-TPE). Ninety four patients (50M and 44 F, mean age 60+/-18, range 18-95 years) with pleural effusion(PE) were studied. TPE was diagnosed in patients with : (i) positive pleural fluid or pleural biopsy culture or (ii) granulomas in the pleural biopsy specimen, after exclusion of other granulomatous diseases. Pleural fluid ADA activity was measured with the colorimetric method of giusti, while IFN-gamma was measured by ELISA. TPE was diagnosed in 28 patients. The non-TPE group consisted of 35 patients with malignant PE, 20 patients with parapneumonic effusion/pleural empyema, 5 with pleural transudate, and 6 with miscellaneous PE. The ADA activity and IFN-gamma concentrations were significantly higher in TPE than in non-TPE (614+/- 324 vs 15+/-36 pg/ml, P< 0.0001 and 75+/- 39 vs 11+/- 16 U/l respectively, P< 0.0001). The diagnostic sensitivity and specificity of IFN-gamma measurement ( cut-off value of 75 pg/ml) were 100% and 98.5% respectively and were similar to those of ADA (100% and 93.9% at the cut-off value of 40.3 U/L). We conclude that pleural fluid ADA activity and IFN-gamma concentration are highly sensitive and specific markers of tuberculous pleurisy.
Comment: These tests are now an important part of of our diagnostic armamentarium, even though few other studies have reached this degree of sensitivity.
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Pulmonary tuberculosis and disease-related pulmonary apical fibrosis in ankylosing spondylitis.
Ho et al Taoyuan Taiwan
J Rheumatol 2009; 36: 355
Objective: We investigated the etiological association and clinical characteristics of apical pulmonary fibrosis in ankylosing spondylitis (AS).
Methods: We reviewed medical records of 2136 consecutive patients diagnosed with AS at a tertiary medical center. Clinical and radiographic characteristics were analysed for evidence of apical lung fibrosis on chest radiographs.
Results: Of 2136 patients with AS, 63 (2.9%) developed apical lung fibrosis, of which chronic infections were the cause in 41 and AS inflammation in 22 patients. Tuberculosis (TB) was considered to be the cause of apical lung fibrosis in 40 patients (63.5%), including 19 with bacteriologically–proven TB and 21 with chest radiographs suggestive of TB. Two were identified as having non-TB mycobacterial infection and one as aspergillus infection. Lung cavities appeared to be crucial differentiators (P=0.009, odds ratio 7.4, 95% CI 1.5-365) between TB and AS inflammation induced apical fibrosis.
Conclusion: Our study suggests that TB, instead of aspergillus, is the most common pulmonary infection in patients with AS presenting with apical pulmonary fibrosis. AS-associated apical lung fibrosis may mimic pulmonary TB infection . Thus, bacteriological survey and serial radiological follow-up of lung fibrocavitary lesions are critical for accurate diagnosis and treatment.
Comment: It does not do to assume that upper lobe or apical segment shrinkage on a plain chest film is due to ankylosing spondylitis in a patient with that disease, even in a country with little TB.
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Treatment
Treatment outcomes among patients with multidrug-resistant tuberculosis: systematic review and meta-analysis.
Orenstein et al Tugela KwaZulu-Natal South Africa
Lancet Infect Dis 2009; 9: 153
Summary: Multi-drug-resistant (MDR) tuberculosis is a growing clinical and public-health concern. To evaluate existing evidence regarding treatment regimens for MDR tuberculosis, we used a Bayesian random-effects meta-analysis to assess how the reported proportion of patients treated successfully is influenced by differences in treatment regimen, study methodology, and patient population. Successful treatment outcome was defined as cure or treatment completion. 34 clinical reports with a mean of 250 patients per report met the inclusion criteria. Our analysis shows that the proportion of patients treated successfully improved when treatment duration was at least 18 months, and if patients received directly observed therapy throughout treatment. Studies that combined both factors had significantly higher pooled success proportions (69%, 95% CI, 64-73%) than other studies of treatment outcomes (58%, 95%CI, 52-64%). Indivualised treatment regimens had higher treatment success (64%, 95% CI 59-68%) than standardised regimens( 54%, 95% CI, 43-68%), although the difference was not significant. Treatment approaches and study methodologies were heterogeneous across studies. Many important variables, including patients’ HIV status, were inconsistently reported between studies. These results underscore the importance of strong patient support and treatment follow-up systems to develop successful MDR tuberculosis treatment programmes.
Comment: We don’t know yet if treatment completion means cure, but these results seem more credible than those reported by the group in Lima, Peru.
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Moxifloxacin versus ethambutol in the initial treatment of tuberculosis: a double-blind, randomised, controlled phase ll trial.
Conde et al Rio de Janeiro Brazil
Lancet 2009; 373: 1183
Background: New treatments are needed to shorten the time required to cure tuberculosis and to treat drug-resistant strains. The fluoroquinolone, moxifloxacin is a promising new agent that might have additive activity to existing antituberculosis agents. We assessed the activity and safety of moxifloxacin in the initial stage of tuberculosis treatment.
Methods: We undertook a phase ll, double-blind ,randomised, controlled trial of a regimen that included moxifloxacin adults with sputum smear-positive tuberculosis at one hospital in Rio de Janeiro, Brazil. 170 participants received isoniazid, rifampicin and pyrazinamide at standard doses and were assigned by permuted block randomisation to receive either moxifloxacin (400 mg) with an ethambutol placebo (n=85) or ethambutol (15-20 mg/kg) plus moxifloxacin placebo (N=85) 5 days a week for 8 weeks. The primary endpoint was the proportion of patients whose sputum culture had converted to negative by week 8. Analysis was modified by intention to treat(ITT); patients whose baseline cultures were negative, contaminated, or contained drug-resistant Mycobacterium tuberculosis were excluded from the analysis. Additionally, all missing 8-week results were deemed treatment failures. This study is registered with Clinical Trials.gov, number NCT00082173.
Findings: 74 patients assigned to the moxifloxacin group and 72 in the ethambutol group were included in the modified ITT population . 125 patients had 8-week data )(moxifloxacin n=64, ethambutol n=61); the main reason for absence of data was culture contamination. At 8 weeks, culture conversion to negative had occurred in 59(80%) of 74 patients in the moxifloxacin group compared with 45 (63%) of 72 in the ethambutol group (difference 17.2% , 95% CI 2.8-31.7; p=0.03). There were 16 adverse events (eight in each group) in 12 patients. Only one event was judged related to the study drug (grade 3 cutaneous reaction in the ethambutol group).
Interpretation: Moxifloxacin improved culture conversion in the initial phase of tuberculosis treatment. Trials to assess whether moxifloxacin can be used to shorten the duration of tuberculosis treatment are justified.
Comment: Not on these results, I think. The differences are barely significant and the confident intervals far too wide. It seems the researchers underestimated the numbers of subjects they needed to enrol.
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Drug Resistant TB
Fitness cost of drug resistance in Mycobacterium tuberculosis.
Gagneux S London UK
Clin Microbiol Infect 2009; 15; Suppl1: 66
Summary: Multidrug-resistant (MDR)— and extensively drug-resistant (XDR)— forms of tuberculosis are growing public health problems. Mathematical models predict that the future of the MDR and XDR tuberculosis epidemics depends in part on the competitive fitness of drug-resistant strains. Here, recent experimental and molecular epidemiological data that illustrate how heterogeneity among drug-resistant strains of Mycobacterium tuberculosis can influence the relative fitness and transmission of this pathogen are reviewed.
Comment: It should be recalled that the very first strains of resistant M tuberculosis sacrificed fitness for resistance, but this state of affairs did not last.
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Population Studies
Major Mycobacterium tuberculosis lineages associate with patient country of origin.
Reed et al Montreal Canada
J Clin Microbiol 2009; 47: 1119
Summary: Over recent years , there has been an increasing acknowledgment of the diversity that exists among Mycobacterium tuberculosis clinical isolates. To facilitate comparative studies aimed at deciphering the relevance of this diversity to human disease, an unambiguous and easily interpretable method of strain classification is required. Presently, the most effective means of assigning isolates into a series of unambiguous lineages is the method of Gagneux et al, that involves the PCR-based detections of large sequence polymorphisms (LSPs). In this manner, isolates are classified into six major lineages, the majority of which display a high degree of geographic restriction. Here we describe an independent replicate of the Gagneux study carried out on 798 isolates collected over a 6-year period from mostly foreign-born patients resident on the island of Montreal, Canada. The original trends in terms of bacterial genotype and patient ethnicity are remarkably conserved within this Montreal cohort, even though the patient distributions between the two populations are quite distinct. In parallel with the LSP analysis, we also demonstrated that “clustered” tuberculosis (TB) cases defined through restriction fragment length polymorphism (RFLP) analysis ( for isolates with > or= 6 IS6110 copies) cor RFLP in combination with spoligotyping ( for isolates with <6 IS6110 copies) do not stray across the LSP-defined lineage boundaries. However, our data also demonstrate the poor discriminatory power of either RFLP or spoligotyping alone for these low-IS6110-copy-number isolates. We believe that this independent validation of the LSP method should encourage researchers to adopt this system in investigations aimed at elucidating the role of strain variation in TB.
Comment: Would these findings also hold up for Australia’s various imported strains?
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Human-to–human transmission of tuberculosis caused by Mycobacterium tuberculosis bovis in immunocompetent patients.
Sunder et al Tours France
J Clin Microbiol 2009; 47: 1249
Summary: Human-to-human transmission of Mycobacterium bovis in two immunocompetent patients from the same family was confirmed by spoligotyping (pattern F35, which was only observed in cattle from the same area in France). A single allelic difference between animal and human isolates
was observed with mycobacterial interspersed repetitive units containing variable-number tandem repeats, suggesting a jump across the species barrier.
Comment: Such a jump is rarely seen between humans and cattle and less often between us and other animals.
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Contact tracing by RFLP
