Severe acute respiratory syndrome (SARS): breathtaking progress

Reports of a new severe respiratory disease, now defined as severe acute respiratory syndrome (SARS), began to emerge from Guangdong, in southern China, in late 2002. The condition came to international attention through an explosive outbreak in Hong Kong in March 2003. Cases appeared throughout South-East Asia and in Toronto, the spread of SARS being accelerated by international air travel. A global emergency was declared by the World Health Organization, bringing together an international team of epidemiologists, public health physicians and microbiologists to study and contain the disease. This response has enabled the nature of the infectious agent to be identified, its mode of transmission to be established and diagnostic tests to be created rapidly.</p

Prospective evaluation of BDProbeTec strand displacement amplification (SDA) system for diagnosis of tuberculosis in non-respiratory and respiratory samples.

Nucleic acid amplification techniques (NAATs) have been demonstrated to make significant improvements in the diagnosis of tuberculosis (TB), particularly in the time to diagnosis and the diagnosis of smear-negative TB. The BD ProbeTec strand displacement amplification (SDA) system for the diagnosis of pulmonary and non-pulmonary tuberculosis was evaluated. A total of 689 samples were analysed from patients with clinically suspected TB. Compared with culture, the sensitivity and specificity for pulmonary samples were 98 and 89 %, and against final clinical diagnosis 93 and 92 %, respectively. This assay has undergone limited evaluation for non-respiratory samples and so 331 non-respiratory samples were tested, identifying those specimens that were likely to yield a useful result. These were CSF (n = 104), fine needle aspirates (n = 64) and pus (n = 41). Pleural fluid (n = 47) was identified as a poor specimen. A concern in using the SDA assay was that low-positive samples were difficult to interpret; 7.8 % of specimens fell into this category. Indeed, 64 % of the discrepant results, when compared to final clinical diagnosis, could be assigned as low-positive samples. Specimen type did not predict likelihood of a sample being in the low-positive zone. Although the manufacturers do not describe the concept of a low-positive zone, we have found that it aids clinical diagnosis

The bactericidal activity of moxifloxacin in patients with pulmonary tuberculosis

Patients in whom acid-fast bacilli smear-positive pulmonary tuberculosis was newly diagnosed were randomized to receive 400 mg moxifloxacin, 300 mg isonaizid, or 600 mg rifampin daily for 5 days. Sixteen-hour overnight sputa collections were made for the 2 days before and for 5 days of monotherapy. Bactericidal activity was estimated by the time taken to kill 50% of viable bacilli (vt(50)) and the fall in sputum viable count during the first 2 days designated as the early bactericidal activity (EBA). The mean vt(50) of moxifloxacin was 0.88 days (95% confidence interval [Cl], 0.43-1.33 days) and the mean EBA was 0.53 (95% CI 0.28-0.79). For the isoniazid group, the mean vt(50) was 0.46 days (95% Cl, 0.31-0.61 days) and the mean EBA was 0.77 (95% Cl, 0.54-1.00). For rifampin, the mean vt(50) was 0.71 days (95% Cl, 0.48-0.95 days) and the mean EBA was 0.28 (95% Cl, 0.15-0.41). Using the EBA method, isoniazid was significantly more active than rifampin (p < 0.01) but not moxifloxacin. Using the vt(50) method, isoniazid was more active than both rifampin and moxifloxacin (p = 0.03). Moxifloxacin has an activity similar to rifampin in human subjects with pulmonary tuberculosis, suggesting that it should undergo further assessment as part of a short course regimen for the treatment of drug-susceptible tuberculosis

Aetiological role of viral and bacterial infections in acute adult lower respiratory tract infection (LRTI) in primary care.

BACKGROUND: Lower respiratory tract infections (LRTI) are a common reason for consulting general practitioners (GPs). In most cases the aetiology is unknown, yet most result in an antibiotic prescription. The aetiology of LRTI was investigated in a prospective controlled study. METHODS: Eighty adults presenting to GPs with acute LRTI were recruited together with 49 controls over 12 months. Throat swabs, nasal aspirates (patients and controls), and sputum (patients) were obtained and polymerase chain reaction (PCR) and reverse transcriptase polymerase chain reaction (RT-PCR) assays were used to detect Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella pneumophila, influenza viruses (AH1, AH3 and B), parainfluenza viruses 1-3, coronaviruses, respiratory syncytial virus, adenoviruses, rhinoviruses, and enteroviruses. Standard sputum bacteriology was also performed. Outcome was recorded at a follow up visit. RESULTS: Potential pathogens were identified in 55 patients with LRTI (69%) and seven controls (14%; p<0.0001). The identification rate was 63% (viruses) and 26% (bacteria) for patients and 12% (p<0.0001) and 6% (p = 0.013), respectively, for controls. The most common organisms identified in the patients were rhinoviruses (33%), influenza viruses (24%), and Streptococcus pneumoniae (19%) compared with 2% (p<0.001), 6% (p = 0.013), and 4% (p = 0.034), respectively, in controls. Multiple pathogens were identified in 18 of the 80 LRTI patients (22.5%) and in two of the 49 controls (4%; p = 0.011). Atypical organisms were rarely identified. Cases with bacterial aetiology were clinically indistinguishable from those with viral aetiology. CONCLUSION: Patients presenting to GPs with acute adult LRTI predominantly have a viral illness which is most commonly caused by rhinoviruses and influenza viruses

The implications of model-informed drug discovery and development for tuberculosis

Despite promising advances in the field and highly effective first-line treatment, an estimated 9.6 million people are still infected with tuberculosis (TB). Innovative methods are required to effectively transition the growing number of compounds into novel combination regimens. However, progression of compounds into patients occurs despite the lack of clear understanding of the pharmacokinetic–pharmacodynamic (PK/PD) relations. The PreDiCT-TB consortium was established in response to the existing gaps in TB drug development. The aim of the consortium is to develop new preclinical tools in concert with an in silico model-based approach, grounded in PKPD principles. Here, we highlight the potential impact of such an integrated framework on various stages in TB drug development and on the dose rationale for drug combinations

Moxifloxacin Replacement in Contemporary Tuberculosis Drug Regimens Is Ineffective against Persistent Mycobacterium tuberculosis in the Cornell Mouse Model

Tuberculosis (TB) caused by Mycobacterium tuberculosis remains a leading killer worldwide, and disease control is hampered by ineffective control of persistent infections. Substitution of moxifloxacin for isoniazid or ethambutol in standard TB regimens reduces treatment duration and relapse rates in animal studies and four-month regimens were not non-inferior in clinical trials. Resuscitation promoting factor (RPF) dependent bacilli have recently been implicated in M. tuberculosis persistence. We aimed to investigate the therapeutic effects of moxifloxacin substitution in the standard drug regimen for eradicating colony forming count (CFU) positive and RPF-dependent persistent M. tuberculosis using the Cornell murine model. M. tuberculosis infected mice were treated with regimens in which either isoniazid or ethambutol were replaced by moxifloxacin to the standard regimen. The efficacy of the regimens was compared to the standard regimen for bacterial CFU count elimination and removal of persistent tubercle bacilli evaluated using culture filtrate (CF) derived from M. tuberculosis strain H37Rv. We also measured disease relapse rates. Moxifloxacin-isoniazid substituted regimen achieved total organ CFU count clearance at 11 weeks post-treatment, faster than standard regimen (14 weeks), and with a 34% lower relapse rate. Moxifloxacin-ethambutol substituted regimen was similar to standard regimens in these regards. Importantly, neither moxifloxacin-substituted regimens nor the standard regimen could remove CF-dependent persistent bacilli. Evaluation of CF-dependent persistent M. tuberculosis requires confirmation in human studies, and has implications in future drug design, testing and clinical applications

Defining dormancy in mycobacterial disease.

Tuberculosis remains a threat to global health and recent attempts to shorten therapy have not succeeded mainly due to cases of clinical relapse. This has focussed attention on the importance of "dormancy" in tuberculosis. There are a number of different definitions of the term and a similar multiplicity of different in vitro and in vivo models. The danger with this is the implicit assumption of equivalence between the terms and models, which will make even more difficult to unravel this complex conundrum. In this review we summarise the main models and definitions and their impact on susceptibility of Mycobacterium tuberculosis. We also suggest a potential nomenclature for debate. Dormancy researchers agree that factors underpinning this phenomenon are complex and nuanced. If we are to make progress we must agree the terms to be used and be consistent in using them

Identification of 2-Aminothiazole-4-Carboxylate Derivatives Active against Mycobacterium tuberculosis H37Rv and the β-Ketoacyl-ACP Synthase mtFabH

Background Tuberculosis (TB) is a disease which kills two million people every year and infects approximately over one-third of the world's population. The difficulty in managing tuberculosis is the prolonged treatment duration, the emergence of drug resistance and co-infection with HIV/AIDS. Tuberculosis control requires new drugs that act at novel drug targets to help combat resistant forms of Mycobacterium tuberculosis and reduce treatment duration. Methodology/Principal Findings Our approach was to modify the naturally occurring and synthetically challenging antibiotic thiolactomycin (TLM) to the more tractable 2-aminothiazole-4-carboxylate scaffold to generate compounds that mimic TLM's novel mode of action. We report here the identification of a series of compounds possessing excellent activity against M. tuberculosis H37Rv and, dissociatively, against the β-ketoacyl synthase enzyme mtFabH which is targeted by TLM. Specifically, methyl 2-amino-5-benzylthiazole-4-carboxylate was found to inhibit M. tuberculosis H37Rv with an MIC of 0.06 µg/ml (240 nM), but showed no activity against mtFabH, whereas methyl 2-(2-bromoacetamido)-5-(3-chlorophenyl)t​hiazole-4-carboxylateinhibited mtFabH with an IC50 of 0.95±0.05 µg/ml (2.43±0.13 µM) but was not active against the whole cell organism. Conclusions/Significance These findings clearly identify the 2-aminothiazole-4-carboxylate scaffold as a promising new template towards the discovery of a new class of anti-tubercular agents

A comparison of liquid and solid culture for determining relapse and durable cure in phase III TB trials for new regimens

BACKGROUND: Tuberculosis kills more people than any other infectious disease, and new regimens are essential. The primary endpoint for confirmatory phase III trials for new regimens is a composite outcome that includes bacteriological treatment failure and relapse. Culture methodology is critical to the primary trial outcome. Patients in clinical trials can have positive cultures after treatment ends that may not necessarily indicate relapse, which was ascribed previously to laboratory cross-contamination or breakdown of old lesions. Löwenstein-Jensen (LJ) medium was the previous standard in clinical trials, but almost all current and future trials will use the Mycobacteria Growth Indicator Tube (MGIT) system due to its simplicity and consistency of use, which will affect phase III trial results. LJ was used for the definition of the primary endpoint in the REMoxTB trial, but every culture was also inoculated in parallel into the MGIT system. The data from this trial, therefore, provide a unique opportunity to investigate and compare the incidence of false 'isolated positives' in liquid and solid media and their potential impact on the primary efficacy results. METHODS: All post-treatment positive cultures were reviewed in the REMoxTB clinical trial. Logistic regression models were used to model the incidence of isolated positive cultures on MGIT and LJ. RESULTS: A total of 12,209 sputum samples were available from 1652 patients; cultures were more often positive on MGIT than LJ. In 1322 patients with a favourable trial outcome, 126 (9.5%) had cultures that were positive in MGIT compared to 34 (2.6%) patients with positive cultures on LJ. Among patients with a favourable outcome, the incidence of isolated positives on MGIT differed by study laboratory (p < 0.0001) with 21.9% of these coming from one laboratory investigating only 4.9% of patients. No other baseline factors predicted isolated positives on MGIT after adjusting for laboratory. There was evidence of clustering of isolated positive cultures in some patients even after adjusting for laboratory, p < 0.0001. The incidence of isolated positives on MGIT did not differ by treatment arm (p = 0.845, unadjusted). Compared to negative MGIT cultures, positive MGIT cultures were more likely to be associated with higher grade TB symptoms reported within 7 days either side of sputum collection in patients with an unfavourable primary outcome (p < 0.0001) but not in patients with a favourable outcome (p = 0.481). CONCLUSIONS: Laboratory cross-contamination was a likely cause of isolated positive MGIT cultures which were clustered in some laboratories. Certain patients had repeated positive MGIT cultures that did not meet the definition of a relapse. This pattern was too common to be explained by cross-contamination only, suggesting that host factors were also responsible. We conclude that MGIT can replace LJ in phase III TB trials, but there are implications for the definition of the primary outcome and patient management in trials in such settings. Most importantly, the methodologies differ in the incidence of isolated positives and in their capacity for capturing non-tuberculosis mycobacteria. It emphasises the importance of effective medical monitoring after treatment ends and consideration of clinical signs and symptoms for determining treatment failure and relapse