These guidelines are not intended to impose a standard of care. They provide the basis for rational decisions in the diagnosis of tuberculosis in the context of the existing evidence. No guidelines can take into account all of the often compelling unique individual clinical circumstances.

Background Individuals infected with Mycobacterium tuberculosis (Mtb) may develop symptoms and signs of disease (tuberculosis disease) or may have no clinical evidence of disease (latent tuberculosis infection [LTBI]). Tuberculosis disease is a leading cause of infectious disease morbidity and mortality worldwide, yet many questions related to its diagnosis remain. Methods A task force supported by the American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America searched, selected, and synthesized relevant evidence. The evidence was then used as the basis for recommendations about the diagnosis of tuberculosis disease and LTBI in adults and children. The recommendations were formulated, written, and graded using the Grading, Recommendations, Assessment, Development and Evaluation (GRADE) approach. Results Twenty-three evidence-based recommendations about diagnostic testing for latent tuberculosis infection, pulmonary tuberculosis, and extrapulmonary tuberculosis are provided. Six of the recommendations are strong, whereas the remaining 17 are conditional. Conclusions These guidelines are not intended to impose a standard of care. They provide the basis for rational decisions in the diagnosis of tuberculosis in the context of the existing evidence. No guidelines can take into account all of the often compelling unique individual clinical circumstances.

A moxifloxacin dose of 800 mg/day is likely to achieve excellent M. tuberculosis microbial kill and to suppress drug resistance. However, tolerability of this higher dose is still unknown.

Rifampin is a cornerstone of modern antituberculosis therapy. However, rifampin's half-life of 3 h is believed to limit its utility for intermittent therapy, so new congeners with long half-lives are being developed. Using an in vitro pharmacokinetic-pharmacodynamic model of tuberculosis, we examined the relationships between rifampin exposure, microbial killing of log-phase-growth Mycobacterium tuberculosis, and suppression of resistance. Rifampin's microbial killing was linked to the area under the concentration-time curve-to-MIC ratio. The suppression of resistance was associated with the free peak concentration (C max )-to-MIC ratio and not the duration that the rifampin concentration was above MIC. Rifampin prevented resistance to itself at a free C max /MIC ratio of >175. The postantibiotic effect duration was >5.2 days and was most closely related to the C max /MIC ratio (r 2 ‫؍‬ 0.96). To explain rifampin's concentration-dependent effect, we examined the kinetics of rifampin entry into M. tuberculosis. Rifampin achieved concentration-dependent intracellular steady-state concentrations within 15 min. Our results suggest that doses of rifampin higher than those currently employed would optimize the effect of rifampin, if patients could tolerate them. Another major implication is that in the design of new rifampin congeners for intermittent therapy, the important properties may include (i) the efficient entry of the rifamycin into M. tuberculosis, (ii) the achievement of a free C max /MIC of >175 that can be tolerated by patients, and (iii) a long postantibiotic effect duration.Tuberculosis (TB) is arguably the most important infectious disease to have confronted humankind. Currently, Mycobacterium tuberculosis infects 2 billion of the 6 billion people worldwide (50). The discovery of rifampin 40 years ago (31) was revolutionary in allowing the creation of potent combination drug regimens against this ancient nemesis. Rifampin is the backbone of modern anti-TB chemotherapy by virtue of being active against M. tuberculosis in exponential growth phase as well as possessing activity against nonreplicating persistent bacilli. Major limitations to rifampin use are believed to include its short half-life (t 1/2 ), which allows cycles of M. tuberculosis regrowth and resistance emergence.It has been the belief for almost half a century that if a drug such as rifampin was given once a week in the initial phase of therapy, its short serum t 1/2 of 3 h would allow short periods of microbial killing followed by regrowth between doses (33, 37). The inference is that the length of time that rifampin is above a certain threshold concentration is the most important index associated with M. tuberculosis killing and the prevention of resistance. Thus, one of the strategic goals of the World Health Organization, the pharmaceutical industry, and research scientists has been to develop rifampin congeners with long t 1/2 s, such as rifapentine, which would make intermittent dosing more effective (3,9,24,26).It is widely believed...

The emergence of rifampin-resistant strains of pathogenic mycobacteria has threatened the usefulness of this drug in treating mycobacterial diseases. Critical to the treatment of individuals infected with resistant strains is the rapid identification of these strains directly from clinical specimens. It Rifampin is an important component of effective multidrug therapies for tuberculosis and leprosy; however, widespread use has led to the emergence of rifampin-resistant (Rif) strains, threatening its usefulness in treating mycobacterial diseases (4-6, 8, 26, 27). Rapid information about drug susceptibility patterns is critical to the treatment of individuals with mycobacterial disease for which rifampin is indicated. Since conventional drug susceptibility testing can require 2 to 4 weeks after growth detection (Mycobacterium tuberculosis) or up to a year (Mycobacterium leprae) in mouse footpads, improvements are needed to yield accurate analysis in a shorter time. DNA diagnostic assays have the potential to provide rapid analysis of rifampin resistance in mycobacteria because of their high degree of sensitivity and specificity and the fact that they do not rely on in vitro growth for results. Shortening the time between diagnosis and the onset of effective therapy should improve patients' survival (tuberculosis) or decrease physical deformities and ocular manifestations resulting in disabilities and blindness (leprosy).Developing such assays requires knowledge of the molecular basis of Rif' in pathogenic mycobacteria. Mutations resulting in the Rif' phenotype in prokaryotes have been mapped to the gene encoding the 1-subunit of the DNA-dependent RNA polymerase (rpoB gene) (10, 11). Recently, the entire rpoB genes of M. leprae (7) resistance have been identified in both species (8,12,28,29). To further characterize mutations associated with the Rif phenotype in M. tuberculosis, M. leprae, and other pathogenic mycobacteria, we developed a rapid PCR-based, DNA sequencing protocol targeted to a 305-bp region of rpoB. By direct DNA sequencing of PCR products, the nucleic acid sequence within this region was determined in 4 rifampinsusceptible (Rifs) and 4 Rif' strains of M. leprae and in 12 Rif' and 110 Rif' strains of M. tuberculosis. In addition, mutations were identified in this region of Rif' strains of Mycobacterium africanum and Mycobacterium avium, the latter causing frequent opportunistic infections in immunocompromised hosts. On the basis of these results we have established conditions for a PCR-heteroduplex formation assay (PCR-HDF) for the rapid detection of the Rif' phenotype in pathogenic mycobacteria. MATERUILS AND METHODSMycobacterial strains. Rifampin-susceptible and -resistant strains of M. leprae were isolated initially from homogenates of skin biopsy samples from lepromatous leprosy patients not responding to antileprosy therapy, which included rifampin, and were subsequently defined as resistant to rifampin by the standard mouse footpad drug susceptibility assay (23). These strains were amplifie...

Mycobacteria are the causative organisms for diseases such as tuberculosis (TB), leprosy, Buruli ulcer, and pulmonary nontuberculous mycobacterial disease, to name the most important ones. In 2015, globally, almost 10 million people developed TB, and almost half a million patients suffered from its multidrug-resistant form. In 2016, a total of 9,287 new TB cases were reported in the United States. In 2015, there were 174,608 new case of leprosy worldwide. India, Brazil, and Indonesia reported the most leprosy cases. In 2015, the World Health Organization reported 2,037 new cases of Buruli ulcer, with most cases being reported in Africa. Pulmonary nontuberculous mycobacterial disease is an emerging public health challenge. The U.S. National Institutes of Health reported an increase from 20 to 47 cases/100,000 persons (or 8.2% per year) of pulmonary nontuberculous mycobacterial disease among adults aged 65 years or older throughout the United States, with 181,037 national annual cases estimated in 2014. This review describes contemporary methods for the laboratory diagnosis of mycobacterial diseases. Furthermore, the review considers the ever-changing health care delivery system and stresses the laboratory's need to adjust and embrace molecular technologies to provide shorter turnaround times and a higher quality of care for the patients who we serve.

Although the virulences and host ranges differ among members of theafricanum, but further characterization resulted in profiles specific for all members. Although six RD regions were used in the analyses with the original 88 isolates, it was found that the use of RD 1, RD 9, and RD 10 was sufficient for initial screenings, followed by the use of RD 3, RD 5, and RD 11 if the results for any of the first three regions were negative. When 605 sequential clinical isolates were screened, 578 (96%) were identified as M. tuberculosis, 6 (1%) were identified as M. africanum, 8 (1%) were identified as M. bovis, and 13 (2%) were identified as M. bovis BCG. Since PCR-based assays can be implemented in most clinical mycobacteriology laboratories, this approach provides a rapid and simple means for the differentiation of members of TBC, especially M. bovis and M. tuberculosis, when it is important to distinguish between zoonotic sources (i.e., cattle and unpasteurized dairy products) and human sources of tuberculosis disease.The Mycobacterium tuberculosis complex (TBC) (4, 34) comprises the closely related organisms M. tuberculosis, M. africanum, M. bovis, the M. bovis BCG vaccine strain, and two rarely seen members, M. microti and M. canettii (35). Differentiation of the members of the TBC is necessary for the treatment of individual patients and for epidemiological purposes, especially in areas of the world where tuberculosis has reached epidemic proportions or wherever the transmission of M. bovis between animals or animal products and humans is a problem. In addition, it can be important to rapidly identify isolates of M. bovis BCG recovered from immunocompromised patients.Although no clear-cut means of differentiation of the members of the TBC was found in the past by using numerical classification (34), a few conventional methods have been useful. Those methods include assays for the ability to metabolize glycerol or pyruvate in Loewenstein-Jensen medium, oxygen preference (aerophilic versus microaerophilic), niacin accumulation, nitrate reductase activity, colony morphology, and resistance to two compounds, thiophen-2-carboxylic acid hydrazide (TCH) and pyrazinamide (PZA) (12,19,38). Partially due to the slow growth of the TBC, interpretation of the results of these assays can be highly subjective, especially interpretation of differences in colony morphology (19), which can be due to the loss of virulence or to mutations associated with drug resistance. An alternative approach is the use of high-performance liquid chromatography; however, only the profile for M. bovis BCG differs from those for the other members of the complex (10).Testing for resistance to TCH has been reported to be the only single test that assigned isolates to any specific member of the TBC; classical M. tuberculosis isolates are resistant to TCH, irrespective of their resistance to isoniazid (8). Alternatively, the Asian strain of M. tuberculosis and all other members of the TBC are TCH susceptible (39, 40). However, cross-resistance to TCH has ...

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