The BACTEC MGIT 960 system, a fully automated, nonradiometric, noninvasive system for detection and drug susceptibility testing of mycobacteria, was evaluated for the ability to test susceptibilities to second-line drugs. In this study, which was carried out in three phases (phase I, mostly susceptible strains; phase II, mostly resistant strains; phase III, final testing of the optimal drug concentrations found in phases I and II), we established the critical concentrations for seven drugs to be tested in the BACTEC MGIT 960 system compared to the BACTEC 460TB system. The critical concentrations for the seven drugs used in the MGIT 960 system are as follows: amikacin, 1.0 g/ml; capreomycin, 2.5 g/ml; ethionamide, 5.0 g/ml; protionamide, 2.5 g/ml; ofloxacin, 2.0 g/ml; rifabutin, 0.5 g/ml; linezolid, 1.0 g/ml. Our results demonstrate that the BACTEC MGIT 960 system is an accurate method for rapid testing of the susceptibilities of Mycobacterium tuberculosis to second-line drugs.Drug susceptibility testing (DST) for both primary and secondary antituberculosis drugs with the broth-based radiometric BACTEC 460 TB system (Becton Dickinson Diagnostic Systems, Sparks, MD) is well established and is considered the "gold standard" (15). However, due to increasing concern about the use and disposal of radioactive material, there is a rapid trend toward using commercially available nonradiometric broth-based culture and susceptibility testing methods. BACTEC MGIT 960 (Becton Dickinson Diagnostic Systems) is a new nonradiometric system which is considered equivalent to the BACTEC 460 in performance. Recovery of mycobacteria from clinical specimens as well as DST for first-line drugs has been thoroughly studied for the MGIT 960 system (3,4,5,7,8,10,11,12). However, no thorough multicenter study has been carried out establishing DST for second-line and newer drugs currently being used in the treatment of tuberculosis. According to the WHO reports, global drug resistance is an increasing concern (18). Some countries are reporting high resistance even against second-line drugs (1, 17). Therefore, it is important that nonradiometric broth-based systems should also offer DST procedures for drugs other than those considered first-line.The primary aim of this multicenter study was to develop a basic protocol, establish critical test concentrations for seven second-line and newer drugs, including a few that have been introduced recently, and then test a large number of clinical isolates. For comparison, BACTEC 460 was used as the gold standard, since critical test concentrations of most of the drugs have already been established for this system (9). It is anticipated that this study will provide a guideline for rapid brothbased susceptibility testing not only of the drugs that have been included here but also of other drugs that are used in the treatment of tuberculosis or will be introduced in the near future. MATERIALS AND METHODSStudy sites. This study was carried out at three sites: (i) the National Reference Center for Mycobacte...

Background: Non-tuberculous mycobacteria (NTM) are ubiquitous environmental organisms. Patients with pre-existing lung damage are susceptible to NTM, but their prevalence in bronchiectasis is unknown. Distinguishing between lung colonisation and disease can be difficult. Methods: A prospective study of 100 patients with bronchiectasis was undertaken to evaluate the prevalence of NTM in sputum, and a retrospective analysis of clinical, microbiological, lung function and radiology data of our clinic patients with NTM sputum isolates over 11 years was performed. Results: The prevalence of NTM in this population of patients with bronchiectasis was 2%. Patients in the retrospective study were divided into three groups: bronchiectasis + multiple NTM isolates (n = 25), bronchiectasis + single isolates (n = 23), and non-bronchiectasis + multiple isolates (n = 22). Mycobacterium avium complex (MAC) species predominated in patients with bronchiectasis compared with non-bronchiectasis lung disease (72% v 9%, p,0.0001). Single isolates were also frequently MAC (45.5%). Multiple isolates in bronchiectasis were more often smear positive on first sample than single isolates (p,0.0001). NTM were identified on routine screening samples or because of suggestive radiology. No particular bronchiectasis aetiology was associated with an NTM. Pseudomonas aeruginosa and Staphylococcus aureus were frequently co-cultured. Six (25%) of multiple NTM patients had cavities of which five were due to MAC. Half the patients with multiple isolates were treated, mostly due to progressive radiology. Conclusions: NTM are uncommon in non-cystic fibrosis bronchiectasis. Routine screening identifies otherwise unsuspected patients. MAC is the most frequent NTM isolated.

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SummaryMycobacterium avium complex (MAC) are opportunistic respiratory pathogens that infect non-immunocompromised patients with established lung disease, although they can also cause primary infections. The ability to bind fibronectin is conserved among many mycobacterial species. We have investigated the adherence of a sputum isolate of MAC to the mucosa of organ cultures constructed with human tissue and the contribution of M. avium fibronectin attachment protein (FAP) to the process. MAC adhered to fibrous, but not globular mucus, and to extracellular matrix (ECM) in areas of epithelial damage, but not to intact extruded cells and collagen fibres. Bacteria occasionally adhered to healthy unciliated epithelium and to cells that had degenerated exposing their contents, but never to ciliated cells. The results obtained with different respiratory tissues were similar. Two ATCC strains of MAC gave similar results. There was a significant reduction (P , 0.05) in the number of bacteria adhering to ECM after preincubation of bacteria with fibronectin and after preincubation of the tissue with M. avium FAP in a concentration-dependant manner. The number of bacteria adhering to fibrous mucus was unchanged. Immunogold labelling demonstrated fibronectin in ECM as well as in other areas of epithelial damage, but only ECM bound FAP. A Mycobacterium smegmatis strain had the same pattern of adherence to the mucosa as MAC. When the FAP gene was deleted, the strain demonstrated reduced adherence to ECM, and adherence was restored when the strain was transfected with an M. avium FAP expression construct. We conclude that MAC adheres to ECM in areas of epithelial damage via FAP and to mucus with a fibrous appearance via another adhesin. Epithelial damage exposing ECM and poor mucus clearance will predispose to MAC airway infection.