Rapid Detection of Ofloxacin Resistance in
            <i>Mycobacterium tuberculosis</i>
            by Two Low-Cost Colorimetric Methods: Resazurin and Nitrate Reductase Assays

Martin, Anandi; Palomino, Juan Carlos; Portaels, Françoise

doi:10.1128/jcm.43.4.1612-1616.2005

Cited by 49 publications

(32 citation statements)

References 24 publications

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“…The critical concentration for OFX was the same as that recommended by the other two studies (13,18) using the manual MGIT but also by Rüsch-Gerdes et al (24) using the automated MGIT 960 system. On the contrary, in the study of Krüüner et al (12), the authors recommend the use of a critical concentration of 1 g/ml of OFX for the MGIT 960.…”

Section: Discussionsupporting

confidence: 49%

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Rapid Detection of Mycobacterium tuberculosis Resistance to Second-Line Drugs by Use of the Manual Mycobacterium Growth Indicator Tube System

et al. 2008

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The objective of this study was to evaluate the manual mycobacterium growth indicator tube (MGIT) system for the testing of Mycobacterium tuberculosis susceptibility to second-line drugs compared to the proportion method. One hundred eighty-eight M. tuberculosis isolates were tested for susceptibility to ofloxacin, kanamycin, ethionamide, and capreomycin by the manual MGIT, and results were compared to those obtained with the proportion method on 7H11 agar, considered a reference method. Results for ofloxacin and capreomycin were excellent, with 100% accuracy, and a result of 99.4% accuracy was achieved for kanamycin. For ethionamide, accuracy was lower, with a result of 86.7% compared to that of the proportion method. We proposed the following critical concentrations for the drugs: for ofloxacin, 2.0 g/ml; for kanamycin, 2.5 g/ml; for ethionamide, 5 g/ml; and for capreomycin, 2.5 g/ml. The time required to obtain results was an average of 8 days by the manual MGIT and 3 weeks by the reference method. Our results show that the manual MGIT is an accurate method for the rapid susceptibility testing of M. tuberculosis to second-line drugs. There is no need for a machine when using the manual MGIT, and results can be read with a simple UV lamp or with a semiquantitative reader, which considerably reduces the cost of the method.The emergence of multidrug-resistant tuberculosis (MDR-TB) caused by Mycobacterium tuberculosis and, recently, extensively drug-resistant tuberculosis caused by an MDR strain that is also resistant to any fluoroquinolone and at least one of the three injectable second-line drugs (kanamycin [KAN], amikacin [AK], and/or capreomycin [CM]) is a real threat for TB control programs (28). It is obvious that there is a great necessity for rapid, reliable, and economical methods for testing the susceptibility of M. tuberculosis not only to first-line drugs but also to second-line drugs. Access to drug susceptibility testing (DST) is a priority, and TB culture is an essential component of TB management. Using the standardized conventional DST methods, it takes a minimum of 3 to 8 weeks to identify resistant or susceptible strains on solid media (6, 7). The introduction of liquid culture media such as the manual mycobacterium growth indicator tube (MGIT) reduces the turnaround time compared to that of solid media, taking an average of 15 days to get results (1,5,19,23,25). In June 2007, the World Health Organization issued a recommendation for the use of liquid media for culture and DST in middle-and low-income countries to address challenges due to the epidemic of human immunodeficiency virus-associated TB and drug-resistant TB, especially in resource-limited settings (29). Fully automated commercial systems such as the BACTEC MGIT 960 (Becton Dickinson) have shown their usefulness for the rapid detection of resistance to second-line drugs (12, 24); however, they require heavy equipment and are still constrained by the cost of the machines. The manual MGIT system has been reported to be a sensitive and ...

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Section: Discussionsupporting

confidence: 49%

“…Two multicenter studies using the BACTEC MGIT 960 automated system for validation of DST of M. tuberculosis to second-line drugs have been described in the literature. Also, only three studies have been reported in the literature using the manual MGIT for second-line drugs, and they focused on only two drugs (3,13,18).…”

Section: Discussionmentioning

confidence: 99%

Rapid Detection of Mycobacterium tuberculosis Resistance to Second-Line Drugs by Use of the Manual Mycobacterium Growth Indicator Tube System

et al. 2008

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“…Resistant strains will reduce the nitrate revealed by a pink-red colour in the medium, while susceptible strains will loose this capacity as they are inhibited by the antibiotic, leaving the medium colourless [79]. The test has been recently evaluated for DST to first-and second-line drugs with good results [80,81]. It has the added advantage of using the same format and culture medium as used in the standard proportion method.…”

Section: Phenotypic Methodsmentioning

confidence: 99%

Nonconventional and new methods in the diagnosis of tuberculosis: feasibility and applicability in the field

Palomino¹

2005

Eur Respir J

147

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Tuberculosis (TB) remains one of the major causes of death from a single infectious agent worldwide. Of great concern for TB control is the emergence of drug resistance. Since there is no cure for some multidrug-resistant strains of Mycobacterium tuberculosis, there is concern that they may spread around the world, stressing the need for additional control measures, such as new diagnostics, better drugs for treatment, and a more effective vaccine.Pulmonary TB can be diagnosed by its symptoms, chest radiography, sputum smear microscopy and by cultivation of M. tuberculosis, which is considered as the gold standard. Recent advances in molecular biology and molecular epidemiology, and a better understanding of the molecular basis of drug resistance in TB, have provided new tools for rapid diagnosis; however, the high cost of most of these techniques, and their requirement for sophisticated equipment and skilled personnel have precluded their implementation on a routine basis, especially in low-income countries.Other nonconventional diagnostic approaches proposed include the search for biochemical markers, detection of immunological response and early detection of M. tuberculosis by methods other than colony counting.In the present article, some of these approaches will be reviewed and the feasibility for their implementation in diagnostic laboratories will be discussed.

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“…Recently, alternative rapid methods have been developed (13). Among them, the nitrate reductase assay (NRA) on Löwenstein-Jensen (LJ) medium is simple to perform and has been successfully implemented in low-income countries (7,13,14). This test is based on the ability of Mycobacterium tuberculosis to reduce nitrate to nitrite, which is revealed as a color change in the culture medium, using the Griess method (10).…”

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Evaluation of Direct Detection of Mycobacterium tuberculosis Rifampin Resistance by a Nitrate Reductase Assay Applied to Sputum Samples in Cotonou, Benin

et al. 2007

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The aim of this study was to evaluate a nitrate reductase assay (NRA) performed on smear-positive sputa for the direct detection of rifampin resistance in Mycobacterium tuberculosis. A total of 213 smear-positive sputa with a positivity score of 1؉ or more (>1 acid-fast bacillus per field by fluorescence microscopy) were used in the study. The samples were decontaminated using the modified Petroff method, and portions of the resulting suspension were used to perform the NRA. The NRA results were compared with the reference indirect proportion method for 177 specimens for which comparable results were available. NRA results were obtained at day 10 for 15 specimens (9%), results for 88 specimens (50%) were obtained at day 14, results for 66 specimens (37%) were obtained at day 18, and results for the remaining 8 specimens (4%) were obtained at day 28. Thus, 96% of NRA results were obtained in 18 days. Of the 177 specimens, there was only one discrepancy (susceptible according to the NRA and resistant according to the indirect proportion method). NRA is simple to perform and provides a rapid, accurate, and cost-effective means for the detection of rifampin resistance in M. tuberculosis isolates.Tuberculosis (TB) remains a major public health problem worldwide. In recent years, the incidence of TB has been rising. There is also an emergence of multidrug-resistant (MDR) tuberculosis (defined as resistance to at least rifampin [RMP] and isoniazid) that is worsening the impact of this disease (1,4,21).Previous studies suggest that RMP resistance could be a surrogate marker for multidrug resistance, especially in settings with a high prevalence of drug resistance (8, 18). Therefore, the detection of resistance to this major anti-TB drug is essential for the optimal control of TB.Conventional tests for the detection of drug resistance require several weeks to yield results (5). Recently, alternative rapid methods have been developed (13). Among them, the nitrate reductase assay (NRA) on Löwenstein-Jensen (LJ) medium is simple to perform and has been successfully implemented in low-income countries (7,13,14). This test is based on the ability of Mycobacterium tuberculosis to reduce nitrate to nitrite, which is revealed as a color change in the culture medium, using the Griess method (10). The indirect (using isolates) NRA yields results in less than 14 days but requires an initial 3 to 4 weeks for cultivation of the isolate (7,13,14).So far, only a few studies have evaluated the NRA applied directly to sputum samples. The results of these studies (which were done in high-incidence settings) were concordant with results obtained by the reference method (15, 17). However, to our knowledge, no direct NRA study has been done in a setting with low resistance prevalence or in Africa, where there is potentially a high frequency of nitrate reductase-negative M. tuberculosis complex strains (11,12).The objective of this study was to evaluate NRA applied directly to smear-positive sputa in the West African country of Benin in orde...

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Rapid Detection of Ofloxacin Resistance in Mycobacterium tuberculosis by Two Low-Cost Colorimetric Methods: Resazurin and Nitrate Reductase Assays

Cited by 49 publications

References 24 publications

Rapid Detection of Mycobacterium tuberculosis Resistance to Second-Line Drugs by Use of the Manual Mycobacterium Growth Indicator Tube System

Rapid Detection of Mycobacterium tuberculosis Resistance to Second-Line Drugs by Use of the Manual Mycobacterium Growth Indicator Tube System

Nonconventional and new methods in the diagnosis of tuberculosis: feasibility and applicability in the field

Evaluation of Direct Detection of Mycobacterium tuberculosis Rifampin Resistance by a Nitrate Reductase Assay Applied to Sputum Samples in Cotonou, Benin

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