Use of microscopic morphology in smears prepared from radiometric cultures for presumptive identification of Mycobacterium tuberculosis complex, Mycobacterium avium complex, Mycobacterium kansasii, and Mycobacterium xenopi

The aim of this study was to assess the feasibility of a method for presumptive identification of mycobacteria, based on the morphology in smears prepared from radiometric Bactec-positive cultures (Becton Dickinson, USA) and to select the appropriate DNA probe (AccuProbe; Gen Probe, USA). The smear morphology of acid-fast bacilli was evaluated in 468 positive cultures from clinical samples: 313 Mycobacterium tuberculosis complex, 67 Mycobacterium avium complex, 32 Mycobacterium kansasii, 49 Mycobacterium xenopi, and seven Mycobacterium gordonae. The sensitivity and specificity for various morphological patterns were as follows: cord formation for Mycobacterium tuberculosis complex 90% and 100%, respectively; striped bacilli for Mycobacterium kansasii, 66% and 99%; sea urchin for Mycobacterium xenopi, 96% and 99%; short bacilli for Mycobacterium avium complex, 61% and 99%; fine-striped bacilli associated with Mycobacterium avium complex from blood samples, 33% and 98%. This criterion was applied in the selection of a suitable DNA probe for the identification of 178 cultures. The correct probe was selected in 98%, 97%, and 72% of cultures, respectively, for Mycobacterium tuberculosis complex, Mycobacterium avium complex, and Mycobacterium kansasii. The observation of acid-fast bacilli morphology in radiometric cultures is a rapid and cost-efficient method for presumptive identification of common clinical isolates of mycobacteria.     

Routine application of high-performance liquid chromatography for identification of mycobacteria

Mycolic acid analysis by high-performance liquid chromatography (HPLC) was introduced in our laboratory as the routine technique for identifying all clinical isolates of mycobacteria referred to us. HPLC identified 96.1% of the 1,103 strains analyzed, whereas the biochemical procedures and/or the commercial DNA probes identified 98.3% of strains, for an overall agreement of 94.4%. Compared with the probes, there was 100% specificity and 98.9% sensitivity for Mycobacterium tuberculosis identification. HPLC allowed early detection and identification of the rare mycobacterial species M. haemophilum, M. malmoense, M. shimoidei, and M. fallax as well as uncharacteristic strains of M. simiae. After 18 months of routine use, HPLC proved to be reliable, easy to perform, rapid, and less costly than other identification methods.     

Assessment of use of the COBAS AMPLICOR system with BACTEC 12B cultures for rapid detection of frequently identified mycobacteria

The use of the COBAS AMPLICOR System (Roche Molecular Diagnostics, Basel, Switzerland), the only automated system for PCR testing, was evaluated for a rapid identification of mycobacteria with positive BACTEC 12B cultures. Two hundred ninety-six specimens with a growth index of >/=30 were analyzed for the presence of Mycobacterium tuberculosis complex, Mycobacterium avium, and Mycobacterium intracellulare. Compared to traditional methods and provided that samples with PCR inhibition are retested at a 1:10 dilution, the sensitivity and specificity of the COBAS AMPLICOR System with BACTEC 12B cultures were 100 and 98%, respectively. The COBAS AMPLICOR method is rapid and reliable for identifying the most common mycobacteria in cultures.     

Direct genotypic detection of Mycobacterium tuberculosis rifampin resistance in clinical specimens by using single-tube heminested PCR

Recent analysis of the gene encoding the beta subunit of Mycobacterium tuberculosis RNA polymerase (rpoB) has demonstrated a small region that harbors the mutations most frequently associated with rifampin resistance. Earlier reports have described a high degree of sequence conservation of rpoB among mycobacteria other than M. tuberculosis and other GC-rich bacteria that can lead to false-positive amplification when applied directly to clinical specimens. We developed reagents for PCR amplification that are based on signature nucleotides discovered by comparative sequence analysis of the rpoB genes of organisms phylogenetically related to M. tuberculosis. The specificities of the reagents were challenged with 20 isolates of multiple-drug-resistant M. tuberculosis and more than 20 species of mycobacteria other than M. tuberculosis and other GC-rich organisms. A single-tube heminested PCR protocol was devised to obtain sensitivity equal to those of an IS6110-based PCR assay and culture in spiked sputum experiments. The assay correctly identified 21 of 24 (87.5%) culture-positive specimens, 13 of which were acid-fast smear-negative, in a panel of 51 clinical specimens. Three specimens that were false-positive initially were negative upon repeat testing when the assay was modified to eliminate the potential for aerosol carryover of the first-round amplification product during the open-tube addition of the second set of reaction reagents. This assay is the most sensitive and specific test to date for the direct detection of M. tuberculosis rpoB in clinical specimens. This rapid PCR-based assay can be used for the simultaneous identification of M. tuberculosis and its rifampin susceptibility genotype.     

An algorithm for the rational choice of sodium profile during hemodialysis

Two systems, the newly developed Mycobacteria Growth Indicator Tube (MGIT) and biphasic Septi-Chek AFB based on liquid media, proved to be significantly better than the egg-based solid media for the isolation of mycobacteria from clinical specimens. The difference in the rates of isolation of bacteria between the two groups of media was more remarkable with smear-negative specimens. The isolation of the Mycobacterium tuberculosis complex by MGIT occurred 8 days previous to the isolation by the conventional Ogawa method. The mean time for detecting M. tuberculosis complex by Septi-Chek AFB was similar to those of the Ogawa method. A greater difference in isolation time was observed for mycobacteria other than M. tuberculosis (MOTT) isolates. These results indicate that the MGIT and Septi-Chek AFB systems based on liquid media are efficient for the recovery of mycobacteria. PCR and other nucleic acid amplification methods are widely used for the detection of M. tuberculosis in clinical specimens. Although the sensitivities of the Gen-Probe Amplified Mycobacteria Direct Test (MTD) and Amplicor Mycobacteria for the detection of the M. tuberculosis complex appear to be similar to the sensitivity of the culture method using the Septi-Chek AFB, the two methods should be quite useful for rapid detection of M. tuberculosis infections. On the other hand, two cooperative blind studies conducted between 6 to 9 laboratories to estimate the reliability and reproducibility of these two commercially available kits revealed the necessity of good laboratory practice and development of reference reagents to monitor the performance of the whole assay, including pretreatment of clinical specimens. Considerable progress has been made in recent years toward understanding the molecular basis of the resistance to antituberculosis drugs, isoniazid (katG, inhA, ahpC), rifampin (rpoB), pyrazinamide (pncA), streptomycin (rpsL, rrs), ethambutol (embB), and fluoroquinolones (gyrA). Most cases of resistance are related usually to simple nucleotide substitutions rather than to acquisition of new genetic elements. Multidrug-resistant isolates of M. tuberculosis arise as a consequence of sequential accumulation of mutations conferring resistance to single therapeutic agents. The basis of resistance is not able to be explained yet in a substantial percentage of strains (> 90%) for other antituberculosis drugs than rifampin. Further studies are required to fully understand the molecular mechanisms of resistance.     

Evaluation of polymerase chain reaction-restriction enzyme analysis of mycobacteria cultured in BACTEC 12B bottles

Polymerase chain reaction with restriction enzyme analysis (PRA) was first tested on 15 reference strains and 50 subcultured clinical isolates of mycobacteria according to the reference algorithm by Telenti et al [1]. Next, we evaluated the application of this method to 108 isolates from liquid media (BACTEC 12B). Of them, 15 M. tuberculosis complex and 81 mycobacteria other than tuberculosis (MOTT) had comparable results with both PRA and the BACTEC 460 TB systems. However, seven M. tuberculosis complex and three potentially pathogenic MOTT were identified by PRA rather than the BACTEC TB system. PRA seems to be an efficient method for the identification of mycobacteria to the species level and a good aid to detect potentially pathogenic mycobacteria, especially in mixed mycobacterial cultures.     

Clinical evaluation of a new non-radiometric automatic system for the rapid diagnosis of tuberculosis

BACKGROUND: Tuberculosis (TB) is again a public health problem un many countries and is considered a re-emerging disease. The fastest possible diagnosis in our patients is essential for TB control programs. ESP is a non-radioactive, totally automated, continuously monitored system designed to detect mycobacteria. METHODS: Clinical evaluation of this new system for the rapid diagnosis of tuberculosis. During 1997 a total of 1,022 clinical sputum specimens were investigated. Specimens were processed in triplicate for ESP, BACTEC 460 TB and L?wenstein-Jensen systems. The validity, isolates of Mycobacterium tuberculosis and time required for detecting M. tuberculosis by the three systems were determined. RESULTS: The sensitivity, specificity, positive predictive and negative predictive values of the new systems were 98%, 99.8%, 98% and 99.8%, respectively. No significant differences were found between the recovery rates by the three systems. The mean time for detection was 10 days (range: 7-13 days) for specimens with positive bacilloscopy and 14 days (range: 10-28 days) for specimens with negative bacilloscopy. The difference was statistically significant between ESP and L?wenstein-Jensen, but not between ESP and BACTEC. CONCLUSIONS: The new system proved to have an excellent sensitivity and specificity, which along with its total automation renders it a system of great clinical interest for the rapid diagnosis of TB and an alternative method for radiometric systems.     

Clinical efficacy of the amplified Mycobacterium tuberculosis direct test for the diagnosis of pulmonary tuberculosis

The amplified Mycobacterium tuberculosis direct test (MTD) is a rapid diagnostic test based on a nucleic acid amplification technique, which can be used directly on processed clinical specimens. We evaluated the clinical utility of the MTD for diagnosing pulmonary tuberculosis by comparing the sensitivity and specificity of the test with acid-fast smear, mycobacterial culture, and clinical evaluation. The study included 844 respiratory tract specimens from 421 patients, which were submitted to the microbiology laboratory of our urban teaching hospital over a 6-mo period. Compared with culture, MTD had a sensitivity of 93.6% and specificity of 97.8%. MTD was more sensitive in detecting pulmonary tuberculosis in patients with previously undiagnosed disease (74.7%) than in those with established disease receiving chemotherapy (29.2%), and in smear-positive (95.5%) than in smear-negative (70.0%) disease. There were two false positive MTD results in patients with nontuberculous mycobacteria, for a specificity in this population of 97.3%. We conclude that MTD, when used in conjunction with routine smear and culture, is a useful rapid diagnostic test for suspected pulmonary tuberculosis.     

Detection of rpoB gene mutation in Mycobacterium tuberculosis by PCR "cold" SSCP

OBJECTIVE: To evaluate the applicability of detection of rpoB gene mutation in M. tuberculosis susceptibility testing. METHODS: 87 M. tuberculosis isolates and 22 sputum specimens from patients with active pulmonary tuberculosis were detected by PCR-SSCP. RESULTS: The sensitivity of PCR for rpoB gene amplification was 100 pg DNA and 5000 organisms. The rpoB gene could be detected in the all isolates tested. In comparison with conventional susceptibility testing methods, the sensitivity and specificity of PCR-"cold" SSCP analysis for detecting rifampin resistance in 87 M. tuberculosis isolates was 89.6% and 100%, respectively. Among 22 smear- and culture-positive sputum specimens, only 1 (4.5%) was positive by PCR, however, 6 (27.3%) of them were positive by nested-PCR. The "cold" SSCP results of these 6 specimens were corresponding to that of the susceptibility testing. CONCLUSIONS: The PCR-"cold" SSCP described here can easily and rapidly detect rifampin resistance of M. tuberculosis. After increasing the primer specificity and amplification sensitivity, the technique might be used for detection of M. tuberculosis rifampin resistance in clinical specimen directly.     

Cord formation in BACTEC medium is a reliable, rapid method for presumptive identification of Mycobacterium tuberculosis complex

Serpentine cord formation in BACTEC 12B medium was evaluated as a rapid method for the presumptive identification of M. tuberculosis complex. Kinyoun acid-fast stained smears were prepared from 666 positive BACTEC 12B bottles and examined for the presence or absence of serpentine cording. Cord formation had a sensitivity, specificity, positive predictive value, and negative predictive value of 89.2, 99.2, 98.5, and 94.2%, respectively. The evaluation of the presence of cord formation in BACTEC 12B medium is reliable and permits the rapid presumptive reporting of M. tuberculosis.     

SMART: identification and annotation of domains from signalling and extracellular protein sequences

Seven hundred thirty-seven clinical samples from 460 patients were processed for direct detection of Mycobacterium tuberculosis complex by a semiautomated ligase chain reaction commercial assay, the LCx Mycobacterium tuberculosis Assay (LCx assay) from Abbott Laboratories. Results were compared to those of direct microscopy and standard microbiological culture. Of 26 patients (5.7%) with a culture positive for M. tuberculosis, 22 (84.6%) were found positive by the LCx assay. The sensitivity of the LCx assay was 98% for smear-positive samples and 27% for smear-negative samples. With an overall culture positivity rate for M. tuberculosis of 8.3% (61 of 737 samples) and after resolution of discrepant results according to clinical data, the sensitivity, specificity, and positive and negative predictive values of the LCx assay were 78, 100, 95, and 98%, respectively, compared to 85, 100, 100, and 98%, respectively, for culture and 67, 99, 87, and 97%, respectively, for acid-fast staining. In conclusion, the LCx assay proved satisfactory and appears to be an easy-to-use 1-day test which must be used with standard culture methods but can considerably reduce diagnosis time versus culture. However, its clinical interest appears to be limited in our population with low mycobacterial prevalence because of its cost considering the small gain in sensitivity versus direct microscopy.     

Safe determination of susceptibility of Mycobacterium tuberculosis to antimycobacterial agents by flow cytometry

We showed previously that susceptibility testing for Mycobacterium tuberculosis labeled with fluorescein diacetate could be accomplished rapidly by using flow cytometry. However, safety was a major concern because mycobacteria were not killed prior to flow cytometric analysis. In this study, we developed a biologically safe flow cytometric susceptibility test that depends on detection and enumeration of actively growing M. tuberculosis organisms in drug-free and antimycobacterial agent-containing medium. The susceptibilities of 17 clinical isolates of M. tuberculosis to ethambutol, isoniazid, and rifampin were tested by the agar proportion and flow cytometric methods. Subsequently, all flow cytometric susceptibility test samples were inactivated by exposure to paraformaldehyde before analysis with a flow cytometer. Agreement between the results from the two methods was 98%. In addition, the flow cytometric results were available 72 h after the initiation of testing. The flow cytometric susceptibility assay is safe, simple to perform, and more rapid than conventional test methods, such as the BACTEC system and the proportion method.     

Evaluation of detection of M. tuberculosis in clinical specimens of tuberculosis by DNA amplification

The sensitivity of detection of M. tuberculosis genomic DNA were 1pg or 10-100 bacterial cell by PCR. Only M. tuberculosis, M. bovis and BCG were positive with 165 b.p band, but all other 14 mycobacterium and 10 bacteria of non-mycobacterial tested, were negative. Of 75 sputum specimens of pulmonary tuberculosis, the positive rate of PCR were 53.3%, culture method showed only 21.3%, fast-acid staining were 25.3%. 17 non-tuberculosis lung disease were negative in three methods. Of 58 tuberculosis meningitis, the positive rate of PCR, the fast-acid staining and culture in cerebrospinal fluid were 51.7%, 8.6%, 1.7% respectively. 30 non-tuberculosis meningitis were negative in three methods. The results showed that DNA amplification is a superior method with high degree of sensitivity and specificity for rapid diagnosis of pulmonary tuberculosis and tuberculosis meningitis.     

Clinical evaluation of the BDProbeTec strand displacement amplification assay for rapid diagnosis of tuberculosis

The reliability of the BDProbeTec MTB Test (Becton Dickinson, Sparks, Md.) for direct detection of Mycobacterium tuberculosis in respiratory specimens was evaluated by comparing results to those of conventional mycobacterial culture, with the BACTEC TB 460 and Middlebrook 7H11 biplates. Patients known to have tuberculosis were excluded from analysis. Of 523 specimens from 277 patients, 53 grew a mycobacterium: 24 specimens of M. tuberculosis and 29 specimens of nontuberculous mycobacteria. After initial testing, 42 specimens were positive by the BDProbeTec, for overall sensitivity, specificity, and positive and negative predictive values of 95.8, 96. 2, 54.8, and 99.8%, respectively. After resolution of discrepancies, 28 specimens were positive by the BDProbeTec, for overall sensitivity, specificity, and positive and negative predictive values of 100, 99.2, 85.7, and 100%, respectively. These same values were 100, 80.8, 93.4, and 100%, respectively, for smear-positive samples and 100, 99.4, 75.0, and 100%, respectively, for smear-negative specimens.     

Clinical utility of an amplification test based on ligase chain reaction in pulmonary tuberculosis

We evaluated the sensitivity and specificity of a new semiautomated direct amplification test (DAT), the LCx-MTB, for the diagnosis of pulmonary tuberculosis (TB) and assessed its positive predictive value by focusing on patients with high clinical and radiologic suspicion of pulmonary TB. Respiratory tract specimens from 32 consecutive patients with high suspicion of active pulmonary TB (case patients) and from 204 control patients were cultured for Mycobacterium tuberculosis and tested by LCx-MTB. Sensitivity and specificity of LCx-MTB when compared with culture was, respectively, 80 and 98%. Pulmonary TB was confirmed in the 32 case patients without knowledge of the LCx results: 18 patients were smear- and culture-positive for M. tuberculosis, and all gave at least one specimen that was LCx-positive. Eight patients were smear-negative culture-positive, and seven gave at least one LCx-positive specimen. LCx-MTB was negative in all the specimens obtained from six patients with smear- and culture-negative TB. A positive LCx-MTB result in a smear negative specimen was 100% predictive that at least one of the case patients' specimens would yield M. tuberculosis. As a consequence, knowledge of the LCx-MTB results at the time of specimen collection could have hastened the start of the antituberculosis therapy in three (21%) smear-negative case patients and could have avoided unnecessary invasive diagnostic procedures in four (29%). We conclude that the sensitivity of LCx-MTB in detecting M. tuberculosis DNA in respiratory tract specimens is similar to other DATs, that LCx-MTB is a reliable test for confirmation of TB in smear-positive patients and that LCx-MTB could be beneficial as a diagnostic step in smear-negative patients with a high suspicion of pulmonary TB.     

Effects of protein kinase inhibitors on heat-induced hsp72 gene expression in a human glioblastoma cell line

This study aims to evaluate the performance of a new diagnostic method (LCx Tuberculosis Assay, Abbott Laboratories) based on Ligase Chain Reaction (LCR) technology, for the detection of Mycobacterium tuberculosis in respiratory and non-respiratory specimens and compare it with standard microbiological data and the clinical diagnosis of tuberculosis. Nine hundred specimens were collected from patients with a high suspicion of tuberculosis (740 respiratory samples and 160 non-respiratory specimens). The study was divided into two separate groups: samples washed and distilled water (207 samples) and unwashed samples that were directly resuspended in phosphate buffer (693 samples). The overall sensitivity, specificity, positive and negative predictive values of samples washed with distilled water after decontamination with SDS-NaOH were: 54%, 100%, 100%, and 94%, respectively. If these results were divided according to origin of specimens, the sensitivity, specificity, positive and negative predictive values in respiratory and non-respiratory samples were 54.5%, 100%, 100%, 94% and 50 100%, 100%, 93%, respectively. In contrast, for the non-washed samples, values were 85%, 95%, 80% and 98%, respectively. Respiratory and non-respiratory samples gave values of 84%, 96%, 77%, and 97.5% versus 89%, 99%, 94%, and 98%. The LCx M. tuberculosis assay is a novel, semi-automated assay and a rapid and highly specific technique for screening all forms of tuberculosis, including non-respiratory forms.     

PCR assay based on DNA coding for 16S rRNA for detection and identification of mycobacteria in clinical samples

A PCR and a reverse cross blot hybridization assay were developed for the detection and identification of mycobacteria in clinical samples. The PCR amplifies a part of the DNA coding for 16S rRNA with a set of primers that is specific for the genus Mycobacterium and that flanks species-specific sequences within the genes coding for 16S rRNA. The PCR product is analyzed in a reverse cross blot hybridization assay with probes specific for M. tuberculosis complex (pTub1), M. avium (pAvi3), M. intracellulare (pInt5 and pInt7), M. kansasii complex-M. scrofulaceum complex (pKan1), M. xenopi (pXen1), M. fortuitum (pFor1), M. smegmatis (pSme1), and Mycobacterium spp. (pMyc5a). The PCR assay can detect 10 fg of DNA, the equivalent of two mycobacteria. The specificities of the probes were tested with 108 mycobacterial strains (33 species) and 31 nonmycobacterial strains (of 17 genera). The probes pAvi3, pInt5, pInt7, pKan1, pXen1, and pMyc5a were specific. With probes pTub1, pFor1, and pSme1, slight cross hybridization occurred. However, the mycobacterial strains from which the cross-hybridizing PCR products were derived belonged to nonpathogenic or nonopportunistic species which do not occur in clinical samples. The test was used on 31 different clinical specimens obtained from patients suspected of having mycobacterial disease, including a patient with a double mycobacterial infection. The samples included sputum, bronchoalveolar lavage, tissue biopsy samples, cerebrospinal fluid, pus, peritoneal fluid, pleural fluid, and blood. The results of the PCR assay agreed with those of conventional identification methods or with clinical data, showing that the test can be used for the direct and rapid detection and identification of mycobacteria in clinical samples.     

Homeless children

The aim of the study was to evaluate the applicability to urine samples of the Amplified Mycobacterium tuberculosis Direct Detection Test (AMTD), which is currently used to identify this organism in respiratory specimens within a few hours. The study was performed on 95 patients, comprising 35 subjects with a high index of suspicion for active tuberculosis of the urinary tract and 60 subjects with evidence of non-mycobacterial disease. One urine specimen from each subject was examined by microscopy, culture and AMTD. AMTD was positive in 38 specimens and negative in 57. Assuming culture as the reference standard, the sensitivity, specificity, positive predictive value and negative predictive value of AMTD were 100%, 91.93%, 86.84% and 100%, respectively. Reassessing the discrepancies between AMTD and culture by review of patients' charts, the sensitivity, specificity, positive predictive value and negative predictive value of AMTD were 100%, 93.44%, 89.47% and 100%. The results of the study as well as the characteristics of AMTD encourage its use for the rapid recognition of urinary tract tuberculosis, although its findings should be interpreted cautiously when the clinical picture is not consistent with an active tuberculosis.     

Neuropathogenesis induced by rhesus cytomegalovirus in fetal rhesus monkeys (Macaca mulatta)

In a double-blind study, 655 sputum specimens were obtained from individuals suspected of having tuberculosis and were analyzed for the presence of Mycobacterium tuberculosis and rifampin susceptibility with use of a polymerase chain reaction (PCR)-based universal heteroduplex generator assay (PCR/UHG-Rif). Of the specimens containing viable M. tuberculosis, 100% of the smear-positive (n = 41) and 50% of the smear-negative (n = 6) specimens tested positive for the organism by PCR/UHG-Rif. Nineteen of 537 culture-negative specimens tested positive for M. tuberculosis by PCR/UHG-Rif and were from patients with confirmed tuberculosis who were receiving antituberculosis therapy at the time of specimen collection. Thirty-five specimens contained nontuberculous mycobacteria and were negative by PCR/UHG-Rif. Genotypic evidence of rifampin resistance in five of six culture-confirmed, rifampin-resistant isolates was obtained by PCR/UHG-Rif, yielding a sensitivity and specificity for the assay of 83% and 98.2%, respectively. These results demonstrate the feasibility of using a PCR-based assay directly on sputum specimens for simultaneous detection of M. tuberculosis and rifampin susceptibility, and they suggest that patients with smear-positive, untreated tuberculosis and those presenting with suspected drug-resistant tuberculosis are the most appropriate groups for testing by PCR/UHG-Rif.     

Evaluation of mycobacteria growth indicator tube for recovery and drug susceptibility testing of Mycobacterium tuberculosis isolates from respiratory specimens

The new BBL mycobacteria growth indicator tube (MGIT) was evaluated for its ability to detect mycobacteria directly from patient specimens and to determine the drug susceptibility of Mycobacterium tuberculosis isolates. A total of 85 respiratory specimens were tested. Specimens were digested, concentrated, examined microscopically for acid-fast bacilli, and inoculated into MGITs and onto Lowenstein-Jensen slants by standard procedures. The tubes were incubated at 37 degrees C and were examined daily for fluorescence to 365-nm UV light. All 25 specimens smear positive for acid-fast bacilli were tested for drug susceptibility in MGITs containing 1.0 mu g of rifampin per ml, 0.1 mu g of isoniazid per ml, 2.0 mu g of streptomycin per ml, and 2.0 mu g of ofloxacin per ml. These results were compared with those obtained by testing the same M. tuberculosis isolates by the indirect proportion method at drug concentrations of 4.0 mu g of rifampin per ml, 0.2 mu g of isoniazid per ml, 2.0 mu g of ethambutol per ml. 4.0 mu g of streptomycin per ml, and 2.0 mu g of ofloxacin per ml. No significant difference in the sensitivity of detection of M. tuberculosis isolates was found between the two methods. However, the time to detection was significantly shorter in MGITs. Drug susceptibility test results for M. tuberculosis isolates by the two methods demonstrated an excellent correlation. The mean time to reporting of drug susceptibility results was 5 days for MGITs versus 16 days for Lowenstein-Jensen slants. The results of this preliminary study indicate that the MGIT system appears to have potential for routine use in mycobacteriology for both the detection and the drug susceptibility testing of M. tuberculosis isolates. However, it is important to emphasize that simple nonautomated equipment should be developed to improve the accuracy of fluorescence detection.