Evaluation of BACTEC MGIT 960 System for Testing Susceptibility of Mycobacterium tuberculosis to First-Line Drugs in China

Background

The purpose of this study was to evaluate the performance of the BACTEC MGIT 960 (M960) system compared with the proportion method (PM) on Löwenstein-Jensen (L-J) medium in a peripheral laboratory in China for the testing of Mycobacterium tuberculosis (MTB) susceptibility to streptomycin (SM), isoniazid (INH) rifampicin (RIF) and ethambutol (EMB) a combination known as SIRE.

Methods

The susceptibility of 205 clinical isolates of MTB to SM, INH, RIF and EMB was performed with the M960 system. The drugs were tested at the following concentrations: 1.0 µg/ml for SM, 0.1 µg/ml for INH, 1.0 µg/ml for RIF, and 5.0 µg/ml for EMB. The results were compared with those obtained by the L-J PM. The L-J PM at an arbiter site was used to resolve any discordant results.

Results

The overall consistency was 96.6% and concordance values were 95.6% for SM, 97.6% for INH, 98.0% for RIF and 95.1% for EMB. The overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the M960 system for PM (the standard method) was 95.6%, 97.3%, 96.2% and 96.9% respectively, and the sensitivity were 93.3% for SM, 96.9% for INH, 97.4% for RIF and 94.6% for EMB, the specificity were 96.9% for SM, 98.2% for INH, 98.4% for RIF and 95.5% for EMB, the PPV were 94.6% for SM, 97.9% for INH, 97.4% for RIF and 94.6% for EMB, the NPV were 96.2% for SM, 97.3% for INH, 98.4% for RIF and 95.5% for EMB. The turnaround time with the M960 system (median 8.0 days, ranged from 5 to 14 days) was significantly shorter than that with the PM (28 days or 42 days).

Conclusion

There was a substantial degree of agreement between the two methods. The M960 system was a reliable and rapid method for SIRE susceptibility testing of tuberculosis in China.     

Intracellular growth of pathogenic mycobacteria in the continuous murine macrophage cell line J-774: Ultrastructure and drug-susceptibility studies

The comparative action of seven drugs, namely, rifampicin (RIF), ansamycin-LM 427 (ANS), streptomycin (SM), isoniazid (INH), pyrizinamide (PZA), clofazimine (CLF), and pristinamycin (PST), was studied both on extracellularly and intracellularly growing mycobacterial speciesMycobacterium bovis, M. tuberculosis, andM. avium. All the drugs were used at their minimal inhibitory concentrations (MICs) and their obtainable serum levels in man; 10×MICs, when less than the obtainable serum levels, were also tested. The action of drugs on extracellularly growing bacilli was tested with the Middlebrook 7H9-Tween medium, whereas for intracellular growth, an experimental model using a continuous murine macrophage cell line J-774 was developed, and macrophage-mycobacteria interactions by use of cytochemistry, scanning and transmission electron microscopy were investigated. Extracellularly growingM. avium was resistant to all the drugs tested; however, when tested on intracellularly growing bacilli, both RIF and CLF were found to be bactericidal, whereas other drugs only delayed the bacterial growth. In the case of extracellularly growingM. bovis andM. tuberculosis, INH, RIF, and SM were active, whereas PZA was active only onM. tuberculosis. However, on intracellularly growing bacilli, only INH and RIF were found to be bactericidal for both species, CLF to a lesser extent in the case ofM. tuberculosis; ANS and SM were bacteriostatic, whereas both PZA and PST were without any antibacterial effect. This investigation underlined the discrepancies concerning the action of drugs on extra- and intracellularly multiplying mycobacteria and the advantage of using a continuous cell line model while studying drug susceptibility of mycobacteria in relation to their intracellular growth.     

Drug action against intracellularly growingMycobacterium xenopi

The intracellular growth kinetics ofMycobacterium xenopi was studied in the murine J-774 macrophage cell line model. During the initial 4 days of infection, the bacilli divided about every 33 h. Electron microscopy of infected macrophages showed that bacteria inside phagosomes were surrounded by a protective electron-transparent zone (ETZ). This model was used for comparing the extracellular and intracellular activities of the following drugs: pristinamycin (PRISTINA), isoniazid (INH), clofazimine (CLOFA), rifabutin (=ansamycin; ANSA), rifampicine (RIFA), streptomycin (SM), ethambutol (EMB), and five fluoroquinolones, namely, ciprofloxacin (CIPRO), ofloxacin (OFLO), pefloxacin (PEFLO), enoxacin (ENOX) and norfloxacin (NORFLO). All the drugs were tested within their obtainable serum level concentrations in man. Under these conditions, CLOFA, SM, CIPRO, and OFLO were highly active against intracellularly growingM. xenopi, INH and RIFA were moderately active, whereas ANSA, PRISTINA, EMB, PEFLO, ENOX, and NORFLO were only growth inhibiting. The comparison of these data with extracellular activities of the same drugs underlined the discrepancies observed in test-tube drug activity evaluation and its correlation with results of chemotherapy in patients in whom the drug has essentially an intracellular bacterial killing role.     

Antimicrobial susceptibility determined by the E test, Löwenstein-Jensen proportion, and DNA sequencing methods among Mycobacterium tuberculosis isolates discrepancies, preliminary results

Mycobacterium tuberculosis strains resistant to streptomycin (SM), isoniazid (INH), and/or rifampin (RIF) as determined by the conventional L?wenstein-Jensen proportion method (LJPM) were compared with the E test, a minimum inhibitory concentration susceptibility method. Discrepant isolates were further evaluated by BACTEC and by DNA sequence analyses for mutations in genes most often associated with resistance to these drugs (rpsL, katG, inhA, and rpoB). Preliminary discordant E test results were seen in 75% of isolates resistant to SM and in 11% to INH. Discordance improved for these two drugs (63%) for SM and none for INH when isolates were re-tested but worsened for RIF (30%). Despite good agreement between phenotypic results and sequencing analyses, wild type profiles were detected on resistant strains mainly for SM and INH. It should be aware that susceptible isolates according to molecular methods might contain other mechanisms of resistance. Although reproducibility of the LJPM susceptibility method has been established, variable E test results for some M. tuberculosis isolates poses questions regarding its reproducibility particularly the impact of E test performance which may vary among laboratories despite adherence to recommended protocols. Further studies must be done to enlarge the evaluated samples and looked possible mutations outside of the hot spot sequenced gene among discrepant strains.     

Cost Resulting from Anti-Tuberculosis Drug Shortages in the United States: A Hypothetical Cohort Study

BackgroundFrom 2012 through 2014, the United States experienced acute shortages and price escalations of several first-line anti-tuberculosis (TB) medications. Because secondary TB drug regimens are longer and adverse events occur more frequently with them, we sought to conservatively estimate the cost, to patients and the health care system, of TB treatment and medication adverse events from alternative regimens during drug shortages.MethodsWe assessed the cost of treatment for TB disease in the absence of isoniazid (INH), rifampin (RIF), or pyrazinamide (PZA), or both INH and RIF. We simulated adverse events based on published probabilities using a monthly discrete-time stochastic model. For total costs, we summed costs of medications, routine testing, and treatment of adverse events using procedural terminology codes. We report average cost ratios of TB treatment during drug shortages to standard TB treatment.ResultsThe cost ratio of TB treatment without INH, RIF, or PZA to standard treatment was 1.7 (Range: 1.2, 2.3), 4.9 (Range: 3.2, 7.3), and 1.1 (Range: 0.7, 1.7) times higher, respectively. Without both INH and RIF, the cost ratio was 18.6 (Range: 10.0, 39.0) times higher. When the prices for INH, RIF and PZA were increased, the cost for standard treatment increased by a factor of 2.7 (Range: 1.9, 3.0). The percentage of patients experiencing at least one adverse event while taking standard therapy was 3.9% (Range: 1.3%, 11.8%). This percentage increased to 51.5% (Range: 20.1%, 83.8%) when RIF was unavailable, and increased to 82.5% (Range: 41.2%, 98.5%) when both INH and RIF were unavailable.ConclusionsOur conservative model illustrates that an interruption in first-line anti-TB medications leads to appreciable additional costs and adverse events for patients. The availability of these drugs in the United States should be ensured. Models that incorporate the effectiveness of alternative regimens, delays in treatment initiation, and TB transmission can provide broader perspectives on the impact of drug shortages.     

In house reverse membrane hybridisation assay versus GenoType MTBDRplus and their performance to detect mutations in the genes rpoB,katG and inhA

Drug-resistant tuberculosis (TB) threatens global TB control and is a major public health concern in several countries. We therefore developed a multiplex assay (LINE-TB/MDR) that is able to identify the most frequent mutations related to rifampicin (RMP) and isoniazid (INH) resistance. The assay is based on multiplex polymerase chain reaction, membrane hybridisation and colorimetric detection targeting of rpoB and katG genes, as well as the inhA promoter, which are all known to carry specific mutations associated with multidrug-resistant TB (MDR-TB). The assay was validated on a reference panel of 108 M. tuberculosis isolates that were characterised by the proportion method and by DNA sequencing of the targets. When comparing the performance of LINE-TB/MDR with DNA sequencing, the sensitivity, specificity and agreement were 100%, 100% and 100%, respectively, for RMP and 77.6%, 90.6% and 88.9%, respectively, for INH. Using drug sensibility testing as a reference standard, the performance of LINE-TB/MDR regarding sensitivity, specificity and agreement was 100%, 100% and 100% (95%), respectively, for RMP and 77%, 100% and 88.7% (82.2-95.1), respectively, for INH. LINE-TB/MDR was compared with GenoType MTBDRplus for 65 isolates, resulting in an agreement of 93.6% (86.7-97.5) for RIF and 87.4% (84.3-96.2) for INH. LINE-TB/MDR warrants further clinical validation and may be an affordable alternative for MDR-TB diagnosis.     

Comprehensive assay for pyrazinamide, rifampicin and isoniazid with its hydrazine metabolites in human plasma by column liquid chromatography

A comprehensive assay for determination of pyrazinamide (PZA), rifampicin (RIF), isoniazid (INH) and hydrazine metabolites is described. The method involves organic solvent extraction of PZA and RIF, followed by derivatization of INH, monoacetylhydrazine (mHYD) and hydrazine (HYD) with salicylaldehyde and extraction with diethyl ether. Acetylisoniazid (acINH) and diacetylhydrazine (dHYD) were hydrolyzed to INH and mHYD, respectively, and processed as above. Using a gradient solvent programmer, PZA and RIF were analyzed on a C₈ (5 μm) column at 248 nm, while INH and metabolites were analyzed on a C₁₈ (5 μm) ODS2 column at 280 nm.     

儿童结核病耐药状况及危险因素分析

目的了解最新儿童耐药结核病流行现状,为耐药儿童结核病的预防、控制提供依据。方法于2006年6月至2009年6月间收集了重庆医科大学附属儿童医院161例结核病患儿样本,采用比例法对链霉素(Streptomycin,SM)、异烟肼(Isoniazide,INH)、利福平(Rifampicin,RFP)、乙胺丁醇(Ethambutol,EMB)和吡嗪酰胺(Pyrazinamide,PZA)共5种药物进行耐药性测定。结果 161株菌株中鉴定出139例为结核分枝杆菌,对这139例培养阳性儿童结核病例中,总耐药率和总耐多药率分别为20.86%、6.47%,平均耐药率顺位由高到低是SM(12.2%)、INH(10.79%)、RFP(8.63%)、EMB(2.88%)、PZA(2.88%)。结论重庆地区儿童结核病总体耐药及耐多药水平低于全国平均水平,城镇地区及复治患儿可能是儿童结核病病例发生多耐药的相关因素。     

Tween-Embedded Microemulsions—Physicochemical and Spectroscopic Analysis for Antitubercular Drugs

The microemulsion composed of oleic acid, phosphate buffer, ethanol, and Tween (20, 40, 60, and 80) has been investigated in the presence of antitubercular drugs of extremely different solubilities, viz. isoniazid (INH), pyrazinamide (PZA), and rifampicin (RIF). The phase behavior showing the realm of existence of microemulsion has been delineated at constant surfactant/co-surfactant ratio (K _m?=?0.55) with maximum isotropic region resulting in the case of Tween 80. The changes in the microstructure of Tween 80-based microemulsion in the presence of anti-TB drugs have been established using conductivty (σ) and viscosity (η) behavior. The optical microscopic images of the system help in understanding the effect of dilution and presence of drug on the structure of microemulsion. Partition coefficient, particle size analysis, and spectroscopic studies (UV–visible, Fourier transform infrared, and ¹H NMR) have been performed to evaluate the location of a drug in the colloidal formulation. To compare the release of RIF, PZA, and INH from Tween 80 formulation, the dissolution studies have been carried out. It shows that the release of drugs follow the order INH>PZA>RIF. The kinetics of the release of drug has been analyzed using the Korsmeyer and Peppas equation. The results have given a fair success to predict that the release of PZA and INH from Tween 80 microemulsion is non-Fickian, whereas RIF is found to follow a Fickian mechanism.     

Drug susceptibility testing of Mycobacterium tuberculosis by the broth microdilution method with 7H9 broth

In this study, we have evaluated the broth microdilution method (BMM) for susceptibility testing of Mycobacterium tuberculosis. A total of 43 clinical isolates of M. tuberculosis and H37Rv as a control strain were studied. All isolates were tested by the proportion method and the BMM for isoniazid (INH), rifampicin (RIF), streptomycin (STR), and ethambutol (ETM). The proportion method was carried out according to the National Committee for Clinical Laboratory Standards (NCCLS) on L?wenstein-Jensen (LJ) medium. The BMM was carried out using 7H9 broth with 96 well-plates. All strains were tested at 3.2-0.05 micro g/ml, 16-0.25 micro g/ml, 32-0.5 micro g/ml, and 32-0.5 micro g/ml concentrations for INH, RIF, STR, and ETM, respectively. When the BMM was compared with the proportion method, sensitivity was 100, 100, 96.9, and 90.2%, while specificity was 100, 85.7, 90.9, and 100% for INH, RIF, STR, and ETM, respectively. The plates were examined 7, 10, 14, and 21 days after incubation. The majority of the result were obtained at 14th days after incubation, while the proportion method result were ended in 21-28 days. According to our results, it may be suggested that the BMM is suitable for early determining of multidrug-resistance-M. tuberculosis strains in developed or developing countries.     

Synthesis and in vitro evaluation of antimycobacterial and cytotoxic activity of new α,β-unsaturated amide,oxazoline and oxazole derivatives from l-serine

The synthesis of 19 compounds derived from l-serine and analogs of p-substituted cinnamic acid is reported. Oxazolines 9 and oxazoles 10 have high antitubercular activity with Minimum Inhibitory Concentration (MIC) of 0.7812–25.0 µg/mL (3.21–100.3 µM), against two strains of Mycobacterium tuberculosis sensitive to first-line drugs Isoniazid (INH), Rifampicin (RIF), Ethambutol (EMB), Pyrazinamide (PZE) (H37Rv) and a clinical isolate resistant to INH, RIF and EMB (G122). The cytotoxic evaluation shows that oxazoles have low activity, finding viability>96% against the VERO cell line. The results show these compounds could be considered as future alternatives for antitubercular treatment.     

In vitro synergistic activity between 8-methoxypsoralen and ethambutol, isoniazid, and rifampin when used in combination against Mycobacterium tuberculosis

8-Methoxypsoralen (8-MOP), a naturally occurring furocoumarin found in many plant species, has been reported to have antimycobacterial activity against Mycobacterium tuberculosis strain H37Rv (ATCC 27294). In the present study, we further test the in vitro synergistic activity of 8-MOP and ethambutol (EMB), isoniazid (INH), or rifampin (RMP) against M. tuberculosis. This study showed that 8-MOP has antimycobacterial activity against two drug-sensitive and six drug-resistant clinical isolates of M. tuberculosis, with the minimum inhibitory concentrations of 100–200 and 200–400 μg/mL, respectively. A synergistic antimycobacterial effect between 8-MOP and EMB, INH, or RMP against six drug-resistant strains was observed, with the fractional inhibitory concentration indices (FICIs) of 0.093–0.156, 0.138–0.285 and 0.093–0.262, respectively. The combination of 8-MOP/EMB, 8-MOP/INH, and 8-MOP/RMP displayed either synergistic activity or had no interaction when tested against the two clinical drug-sensitive strains and the standard strain. No antagonism was observed for any drug combination against any of the strains tested. To our knowledge, this is first report that 8-MOP has synergistic activity with first-line antimycobacterial agents.     

Direct sensitivity test of the MB/BacT system

In order to evaluate the direct-method test of sensitivity to drugs used in the principal tuberculosis treatment regimes, in the Organon Teknika MB/BacT system, we tested 50 sputum samples positive to microscopy taken from patients with pulmonary tuberculosis and with clinical indications for an antibiogram, admitted sequentially for examination during the routine of the reference laboratory. The material was treated v/v with 23% trisodium phosphate solution, incubated for 24 h at 35 degrees C, and neutralized v/v with 20% monosodium phosphate solution. The material was then centrifuged and the sediment inoculated into flasks containing Rifampin - 2 micro g/ml, Isoniazid - 0.2 micro g/ml, Pyrazinamide - 100 micro g/ml, Ethambutol - 2.5 micro g/ml, Ethionamide - 1.25 micro g/ml, and Streptomycin - 2 micro g/ml. The tests were evaluated using the indirect method in the BACTEC 460 TB (Becton Dickinson) system as the gold standard. The results showed that the Rifampin test performed best, i.e., 100% sensitivity at 95% Confidence Interval (82.2-100) and 100% specificity at 95% Confidence Interval (84.5-100), followed by Isoniazid and Pyrazinamide. In this experiment, 92% of the materials showed a final reading in 30 days; this period represents the time for primary isolation as well as the results of the sensitivity profile, and is within Centers for Disease Control and Prevention recommendations regarding time for performance of the antibiogram. The inoculated flasks showed no contamination during the experiment. The MB/BacT is shown to be a reliable, rapid, fully automated nonradiometric system for the tuberculosis antibiogram.     

Comparison of the mycobacteria growth indicator tube with radiometric and solid culture for isolation of mycobacteria from clinical specimens and susceptibility testing of Mycobacterium tuberculosis

We compared the mycobacteria growth indicator tube (MGIT) system with the BACTEC 460 TB and Loewenstein-Jensen (LJ) systems for the recovery of mycobacteria (acid-fast bacilli [AFB]) from 600 clinical specimens. A total of 50 AFB (32 Mycobacterium tuberculosis complex, 10 M. avium complex, 3 M. gordonae, 3 M. xenopi, 1 M. terrae and 1 M. fortuitum) were detected. MGIT recovered 50 isolates of AFB (100% sensitivity), and BACTEC 460 TB and LJ recovered 49 (98% sensitivity) and 19 (38% sensitivity) AFB isolates, respectively. The mean times to detect mycobacteria were 10, 10 and 25 days for MGIT, BACTEC 460, and LJ slants. All isolates of M. tuberculosis complex were tested for susceptibility to streptomycin, isoniazid, rifampin, and ethambutol with the MGIT and BACTEC 460 TB. Both systems yielded identical susceptibility data with different mean times to report (5.38 days for MGIT versus 7.33 days for BACTEC 460 TB, P<0.05). The results suggest that MGIT is equivalent to BACTEC 460 TB in its ability to support the growth of mycobacteria, but significantly more efficient than LJ. MGIT may also be used for susceptibility testing of primary antituberculosis drugs.     

The Performance of the Four Anaerobic Blood Culture Bottles BacT/ALERT-FN, -FN Plus,BACTEC-Plus and -Lytic in Detection of Anaerobic Bacteria and Identification by Direct MALDI-TOF MS

Detection and identification of anaerobic bacteria in blood cultures (BC) is a well-recognized challenge in clinical microbiology. We studied 100 clinical anaerobic BC isolates to evaluate the performance of BacT/ALERT-FN, -FN Plus (BioMérieux), BACTEC-Plus and -Lytic (Becton Dickinson BioSciences) BC bottles in detection and time to detection (TTD) of anaerobic bacteria. BACTEC Lytic had higher detection rate (94/100, 94%) than BacT/ALERT FN Plus (80/100, 80%) (p<0.01) in the studied material. There was no significant difference in detection of anaerobic bacteria among the remaining bottle types. The 67 anaerobic bacteria that signalled positive in all four bottle types were analyzed to compare the time to detection (TTD) and isolates were directly identified by MALDI-TOF MS. There was a significant difference in TTD among the four bottle types (p<0.0001). The shortest median TTD was 18 h in BACTEC Lytic followed by BacT/ALERT FN (23.5 h), BACTEC Plus (27 h) and finally BacT/ALERT FN Plus (38 h) bottles. In contrast, MALDI-TOF MS performed similarly in all bottle types with accurate identification in 51/67 (76%) BacT/ALERT FN, 51/67 (76%) BacT/ALERT FN Plus, 53/67 (79%) BACTEC Plus and 50/67 (75%) BACTEC Lytic bottles. In conclusion, BACTEC Lytic bottles have significantly better detection rates and shorter TTD compared to the three other bottle types. The anaerobic BC bottles are equally suitable for direct MALDI-TOF MS for rapid and reliable identification of common anaerobic bacteria. Further clinical studies are warranted to investigate the performance of anaerobic BC bottles in detection of anaerobic bacteria and identification by direct MALDI-TOF MS.     

Performance Comparison of Three Rapid Tests for the Diagnosis of Drug-Resistant Tuberculosis

Background

The aim of this study was to compare the performance of several recently developed assays for the detection of multi- and extensively drug-resistant tuberculosis (M/XDR-TB) in a large, multinational field trial.

Methods

Samples from 1,128 M/XDR-TB suspects were examined by Line Probe Assay (LPA), Pyrosequencing (PSQ), and Microscopic Observation of Drug Susceptibility (MODS) and compared to the BACTEC MGIT960 reference standard to detect M/XDR-TB directly from patient sputum samples collected at TB clinics in India, Moldova, and South Africa.

Results

Specificity for all three assays was excellent: 97–100% for isoniazid (INH), rifampin (RIF), moxifloxacin (MOX) and ofloxacin (OFX) and 99–100% for amikacin (AMK), capreomycin (CAP) and kanamycin (KAN) resistance. Sensitivities were lower, but still very good: 94–100% for INH, RIF, MOX and OFX, and 84–90% for AMK and CAP, but only 48–62% for KAN. In terms of agreement, statistically significant differences were only found for detection of RIF (MODS outperformed PSQ) and KAN (MODS outperformed LPA and PSQ) resistance. Mean time-to-result was 1.1 days for LPA and PSQ, 14.3 days for MODS, and 24.7 days for MGIT.

Conclusions

All three rapid assays evaluated provide clinicians with timely detection of resistance to the drugs tested; with molecular results available one day following laboratory receipt of samples. In particular, the very high specificity seen for detection of drug resistance means that clinicians can use the results of these rapid tests to avoid the use of toxic drugs to which the infecting organism is resistant and develop treatment regiments that have a higher likelihood of yielding a successful outcome.     

Evaluation of four colourimetric susceptibility tests for the rapid detection of multidrug-resistant Mycobacterium tuberculosis isolates

The purpose of this study is to evaluate four rapid colourimetric methods, including the resazurin microtitre assay (REMA), malachite green decolourisation assay (MGDA), microplate nitrate reductase assay (MNRA) and crystal violet decolourisation assay (CVDA), for the rapid detection of multidrug-resistant (MDR) tuberculosis. Fifty Mycobacterium tuberculosis isolates were used in this study. Eighteen isolates were MDR, two isolates were only resistant to isoniazid (INH) and the remaining isolates were susceptible to both INH and rifampicin (RIF). INH and RIF were tested in 0.25 µg/mL and 0.5 µg/mL, respectively. The agar proportion method was used as a reference method. MNRA and REMA were performed with some modifications. MGDA and CVDA were performed as defined in the literature. The agreements of the MNRA for INH and RIF were 96% and 94%, respectively, while the agreement of the other assays for INH and RIF were 98%. In this study, while the specificities of the REMA, MGDA and CVDA were 100%, the specificity of the MNRA was lower than the others (93.3% for INH and 90.9% for RIF). In addition, while the sensitivity of the MNRA was 100%, the sensitivities of the others were lower than that of the MNRA (from 94.1-95%). The results were reported on the seventh-10th day of the incubation. All methods are reliable, easy to perform, inexpensive and easy to evaluate and do not require special equipment.     

Drug resistance of strains of Mycobacterium tuberculosis isolated in Brazil.

Tuberculosis remains a serious public health problem, worsened by an increased frequency of multidrug-resistant Mycobacterium tuberculosis. We report here a retrospective study of resistance to antituberculosis drugs of 170 strains of M. tuberculosis isolated from the state of Rio Grande do Sul, Brazil. The frequency of resistance to at least one drug was 34%, while 22% were resistant to more than one drug. Among the strains isolated from patients without a history of previous treatment for tuberculosis, patients with positive serology for HIV and patients with previous treatment for tuberculosis, the resistance to at least one drug was 14, 27 and 73%, respectively. Multidrug-resistant tuberculosis, defined as resistant to at least rifampicin (RMP) and isoniazid (INH), was found in the groups of patients without previous treatment, HIV co-infected and with previous treatment for tuberculosis at 10, 17 and 44%, respectively. With the purpose of evaluating whether the sensitivity test to INH and RMP would be a good marker to indicate resistance to other antituberculosis drugs, sensitivity tests were performed with four more drugs in 32 strains, initially classified as resistant to INH, RMP or both. Of 18 strains resistant to INH and RMP simultaneously, 89% showed resistance to four more drugs.     

Drug resistance among Mycobacterium tuberculosis strains isolated in Taiwan during 1975.

455 strains of Mycobacterium tuberculosis were isolated from patients with history of treatment in Taiwan Provincial Tuberculosis Control Bureau and tested for resistance against various antituberculosis agents including streptomycin (SM), paraaminosalicylic acid (PAS), isoniazid (INH), cycloserine (CS), prothionamide (1321TH), kanamycin (KM), ethambutol (EMB), and rifampicin (RFP). In vitro resistance to SM and INH was more frequently found than others and the resistance to a single drug was more common than multiple resistance.