Increased sensitivity of the BACTEC 460 mycobacterial radiometric broth culture system does not decrease the number of respiratory specimens required for a definitive diagnosis of pulmonary tuberculosis

Clinically encountered growth phenotypes of tuberculosis-causing bacilli and their in vitro study: A review

The clinical manifestations of tuberculosis (TB) vary widely in severity, site of infection, and outcomes of treatment-leading to simultaneous efforts to individualize therapy safely and to search for shorter regimens that can be successfully used across the clinical spectrum. In these endeavors, clinicians and researchers alike employ mycobacterial culture in rich media. However, even within the same patient, individual bacilli among the population can exhibit substantial variability in their culturability. Bacilli in vitro also demonstrate substantial heterogeneity in replication rate and cultivation requirements, as well as susceptibility to killing by antimicrobials. Understanding parallels in clinical, ex vivo and in vitro growth phenotype diversity may be key to identifying those phenotypes responsible for treatment failure, relapse, and the reactivation of bacilli that progresses TB infection to disease. This review briefly summarizes the current role of mycobacterial culture in the care of patients with TB and the ex vivo evidence of variability in TB culturability. We then discuss current advances in in vitro models that study heterogenous subpopulations within a genetically identical bulk culture, with an emphasis on the effect of oxidative stress on bacillary cultivation requirements. The review highlights the complexity that heterogeneity in mycobacterial growth brings to the interpretation of culture in clinical settings and research. It also underscores the intricacies present in the interplay between growth phenotypes and antimicrobial susceptibility. Better understanding of population dynamics and growth requirements over time and space promises to aid both the attempts to individualize TB treatment and to find uniformly effective therapies.

Genitourinary tuberculosis in Australia and New Zealand

Genitourinary tuberculosis is not commonly encountered in general urological practice in Australia and New Zealand. However, this infection is easily overlooked unless clinicians maintain a strong awareness of its possibility. This brief overview is directed to reflect the present state of knowledge and management in our two countries.

Approaches to tuberculosis screening and diagnosis in people with HIV in resource-limited settings

Tuberculosis is the main cause of morbidity and mortality in people living with HIV/AIDS worldwide. Early diagnosis and treatment is essential to 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 joint activities at the 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 simpler, cheaper, 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.

Reduction in turnaround time for laboratory diagnosis of pulmonary tuberculosis by routine use of a nucleic acid amplification test

Every first diagnostic specimen from suspected patients with pulmonary TB was tested by a nucleic acid amplification test (NAAT) to determine the reduction in turnaround time (TAT) for detecting Mycobacterium tuberculosis (MTB) that was possible under normal laboratory operating conditions. NAAT (Gen-Probe Mycobacterium tuberculosis Direct Testtrade mark) was performed on the first specimen and liquid culture (BACTEC 460), solid culture (Lowenstein-Jensen [LJ] agar and selective 7H11 [7H11S] agar), and fluorescent acid-fast bacilli (AFB) smear were performed on all 3 specimens from each patient. Eighty-one (10.2%) of 797 patients tested were diagnosed with pulmonary TB. The sensitivity of NAAT, BACTEC, LJ, 7H11S, and smear for the first specimen was 90%, 85%, 67%, 53%, and 58%, respectively, whereas the sensitivity for the series of 3 specimens was 90%, 95%, 74%, 74%, and 70%, respectively. Positive predictive value was 100% for all tests except AFB smear, which was 79%. The time to detect 75% of all TB cases was 4 days for NAAT and 21 days for liquid culture; other tests had a sensitivity of less than 75%. Identification and testing every first diagnostic specimen by NAAT has the potential to reduce the overall TAT for laboratory TB diagnosis by approximately 2 weeks.

Diagnostic techniques in paediatric tuberculosis

Accurate diagnosis of tuberculosis (TB) in children is crucial to provide effective treatment and to identify the undiagnosed adult who probably infected the child. The diagnosis of tuberculosis in children is often based only on epidemiologic, clinical, and radiographic findings. Fibre-optic bronchoscopy may also be helpful but the recovery of tuberculous bacilli, which establishes the diagnosis, is difficult in children. Rapid diagnostic tests such as direct amplification and serological tests have been developed to improve early diagnosis. Their sensitivity is higher than that of conventional mycobacterial culture in most paediatric studies.