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...
Application of real-time PCR for the detection of Mycobacterium tuberculosis enables results to be obtained in about 2 h. A total of 340 nonrespiratory samples were processed using two real-time PCR assay kits: Xpert MTB/RIF and Cobas TaqMan MTB. The sensitivity and specificity of the Xpert assay were 95% and 100%, respectively, compared to 78% and 98% for the Cobas assay.
In a multicenter study involving three reference centers for mycobacteria, the rate of recovery of acid-fast bacilli (AFB) and the mean time to their detection from clinical specimens was determined by using the Mycobacteria Growth Indicator Tube (MGIT). These parameters were compared to those assessed by the radiometric BACTEC 460 TB system and by cultivation on solid media. Clinical specimens (n ؍ 1,500) were pretreated with N-acetyl-L-cysteine (NALC)-NaOH. The contamination rates for MGITs were 2.0% (center 1), 13.8% (center 2), and 6.1% (center 3). A total of 180 mycobacterial isolates were detected (M. tuberculosis complex, n ؍ 113; nontuberculous mycobacteria [NTM], n ؍ 67). When using a combination of liquid and solid media (the current "gold standard" for culture), MGIT plus solid media detected 156 (86.7%) of the isolates, whereas BACTEC plus solid media recovered 168 (93.3%) of all AFB. Between these two gold standards there was no statistically significant difference (P > 0.05). The combination of MGIT plus BACTEC detected 171 (95.0%) of all isolates (compared with MGIT plus solid media, P < 0.01; compared with BACTEC plus solid media, P > 0.05). Considering the efficacies of the different media separately, MGIT was superior to solid media (although not significantly; P > 0.05) in detecting AFB but was inferior to the BACTEC system (P < 0.01). The mean time to the detection of M. tuberculosis complex was 9.9 days with MGIT, 9.7 days with BACTEC, and 20.2 days with solid media. NTM needed, on average, 11.9, 13.0, and 22.2 days to appear by the three methods, respectively. In conclusion, MGIT proved to be a valuable alternative to the radiometric cultivation system.
The aim of this study was to detect risk factors for multidrug resistance in patients with pulmonary tuberculosis in four European Union countries: France, Germany, Italy, and Spain. A prospective epidemiological case control study was conducted, made up of patients with clinically diagnosed and microbiologically confirmed pulmonary tuberculosis in the four countries between 1997 and 2000. A total of 138 cases and 276 controls were studied. Considering the four countries as a whole, the most statistically significant risk factors were as follows: intravenous drug use (OR 4.68); asylum-seeker support (OR 2.55) as income factor; living in a nursing home (OR 2.05); previous tuberculosis (OR 2.03) with pulmonary location; prison (OR 2.02); known tuberculosis contacts (OR 2.01); immunosuppression other than human immunodeficiency virus (HIV) (OR 1.96); acquired immunodeficiency syndrome (AIDS) (OR 1.96); current tuberculosis with pulmonary location (OR 1.77); and health-care worker (OR 1.69). These risk factors will have to be taken into account in the European Union as a whole, as well as in each individual country, to establish a health policy of monitoring and control for these cases of multidrug resistance. Although rare, their seriousness makes them particularly important.
The growing number of fungal infections, coupled with emerging resistance to classical antifungal agents, has led to the development of new agents, among them voriconazole. Susceptibility to voriconazole was tested by two microdilution techniques: the National Committee for Clinical Laboratory Standards reference method M38-A and a colorimetric method, Sensititre YeastOne. The study tested a total of 244 isolates: 223 Aspergillus (136 Aspergillus fumigatus, 37 A. niger, 26 A. terreus, 16 A. flavus, 7 A. nidulans, and 1 A. ustus), 14 Fusarium (8 Fusarium moniliformis, and 6 F. oxysporum), 6 Scedosporium apiospermum, and 1 Rhizomucor pusillus strain and four control strains (Candida parapsilosis ATCC 22019, C. krusei ATCC 6258, A. fumigatus ATCC 204305, and A. flavus ATCC 204304). For all tested species except one F. moniliforme strain and R. pusillus, the MIC, the MIC at which 50% of the isolates are inhibited (MIC 50 ), and MIC 90 ranges of <1 g/ml were obtained for voriconazole, indicating excellent activity against these species. The high rate of agreement between the two methods used (97 to 99%) suggests that the Sensititre YeastOne colorimetric method may be a valuable tool for determining the susceptibility of filamentous fungi to voriconazole.
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