No abstract

The tuberculin skin test for immunologic diagnosis of Mycobacterium tuberculosis infection has many limitations, including being confounded by bacillus Calmette-Guérin (BCG) vaccination or exposure to nontuberculous mycobacteria. M. tuberculosis-specific antigens that are absent from BCG and most nontuberculous mycobacteria have been identified. We examined the use of two of these antigens, CFP-10 and ESAT-6, in a whole blood IFN-gamma assay as a diagnostic test for tuberculosis in BCG-vaccinated individuals. Because of the lack of an accurate standard with which to compare new tests for M. tuberculosis infection, specificity of the whole blood IFN-gamma assay was estimated on the basis of data from people with no identified risk for M. tuberculosis exposure (216 BCG-vaccinated Japanese adults) and sensitivity was estimated on the basis of data from 118 patients with culture-confirmed M. tuberculosis infection who had received less than 1 week of treatment. Using a combination of CFP-10 and ESAT-6 responses, the specificity of the test for the low-risk group was 98.1% and the sensitivity for patients with M. tuberculosis infection was 89.0%. The results demonstrate that the whole blood IFN-gamma assay using CFP-10 and ESAT-6 was highly specific and sensitive for M. tuberculosis infection and was unaffected by BCG vaccination status.

This is the first study reporting global data on AMR in leprosy. Rifampicin resistance emerged, stressing the need for expansion of surveillance. This is also a call for vigilance on the global use of antimicrobial agents, because ofloxacin resistance probably developed in relation to the general intake of antibiotics for other infections as it is not part of the multidrug combination used to treat leprosy.

Tuberculosis ranges among the leading causes of morbidity and mortality worldwide. A diagnostic approach to a patient with possible tuberculosis includes a detailed medical history and clinical examination as well as radiological, microbiological, immunological, molecular-biological and histological investigations, where available. Recently, important advances have been achieved in these fields that have led to substantial improvements in the accuracy and the timing of the diagnosis of tuberculosis. Novel methods allow for a better identification of latently infected individuals who are at risk of developing active tuberculosis, they also offer the possibility for a rapid diagnosis of active tuberculosis in patients with negative sputum smears for acid-fast bacilli and enable prompt identification of drug-resistant strains of Mycobacterium tuberculosis directly from respiratory specimen with a high accuracy. In addition, promising methods that will further optimize the diagnosis of tuberculosis are under development. In the future, therapeutic interventions based on the results of novel diagnostic procedures can be made earlier leading to improvements in patient care.

We developed a DNA sequencing-based method to detect mutations in the genome of drug-resistant Mycobacterium tuberculosis. Drug resistance in M. tuberculosis is caused by mutations in restricted regions of the genome. Eight genome regions associated with drug resistance, including rpoB for rifampin (RIF), katG and the mabA (fabG1)-inhA promoter for isoniazid (INH), embB for ethambutol (EMB), pncA for pyrazinamide (PZA), rpsL and rrs for streptomycin (STR), and gyrA for levofloxacin, were amplified simultaneously by PCR, and the DNA sequences were determined. It took 6.5 h to complete all procedures. Among the 138 clinical isolates tested, 55 were resistant to at least one drug. Thirty-four of 38 INH-resistant isolates (89.5%), 28 of 28 RIF-resistant isolates (100%), 15 of 18 EMB-resistant isolates (83.3%), 18 of 30 STR-resistant isolates (60%), and 17 of 17 PZA-resistant isolates (100%) had mutations related to specific drug resistance. Eighteen of these mutations had not been reported previously. These novel mutations include one in rpoB, eight in katG, one in the mabA-inhA regulatory region, two in embB, five in pncA, and one in rrs. Escherichia coli isolates expressing individually five of the eight katG mutations showed loss of catalase and INH oxidation activities, and isolates carrying any of the five pncA mutations showed no pyrazinamidase activity, indicating that these mutations are associated with INH and PZA resistance, respectively. Our sequencing-based method was also useful for testing sputa from tuberculosis patients and for screening of mutations in Mycobacterium bovis. In conclusion, our new method is useful for rapid detection of multiple-drug-resistant M. tuberculosis and for identifying novel mutations in drug-resistant M. tuberculosis.The emergence and spread of drug-resistant strains of Mycobacterium tuberculosis, especially multidrug-resistant (MDR) strains, are serious threats to the control of tuberculosis and comprise an increasing public health problem (40). Patients infected with MDR strains, which are defined as strains resistant to both rifampin (RIF) and isoniazid (INH), are difficult to cure and are more likely to remain sources of infection for a longer period of time than are patients with drug-susceptible strains (40).It is essential that rapid drug susceptibility tests be developed to prevent the spread of MDR M. tuberculosis. The time necessary for culture of specimens was reduced by the radiometric BACTEC 460TB system (BD Biosciences, Sparks, MD), the nonradiometric ESP II system (Trek Diagnostics, Westlake, OH), and other rapid broth methods, such as BACTEC MGIT 960 SIRE (BD Biosciences) (20). These drug susceptibility tests, however, still require 1 to 2 weeks for final determination and reporting to the clinician (23). Additional reductions in the detection period are needed.Drug resistance in M. tuberculosis is caused by mutations in relatively restricted regions of the genome (17, 39). Mutations associated with drug resistance occur in rpoB for RIF, katG and the promote...