Stability of antimycobacterial drugs in susceptibility testing

Griffith, M E; Bodily, Howard L.

doi:10.1128/aac.36.11.2398

Cited by 26 publications

(18 citation statements)

References 5 publications

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“…For the RIF stock solution, our data indicate that RIF stock solution kept either at 4°C or at Ϫ20°C is eligible for reuse at least within 3 months. Those outcomes are consistent with those reported previously by Griffith and Bodily (5). Even though the RIF stock solution is relatively stable, long-term storage is not recommended, since an evaporation of organic solvent will occur even for solutions kept at Ϫ20°C.…”

Section: Discussionsupporting

confidence: 81%

Rifampin Stability in 7H9 Broth and Löwenstein-Jensen Medium

Jiang

et al. 2011

J Clin Microbiol

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The objectives of this study were to monitor the stability of rifampin (RIF) in Löwenstein-Jensen medium (L-J medium) and 7H9 broth, which are the media commonly used for drug susceptibility testing (DST) of Mycobacterium tuberculosis. Rifampin degradation in stock solution, 7H9 broth, and L-J medium and during the inspissation process for L-J medium preparation was serially monitored by high-performance liquid chromatography (HPLC). L-J medium-based DST was conducted to examine the effect of L-J medium storage on the DST outcome. The RIF stock solution was stable for at least 3 months when kept at either 4°C or ؊20°C; RIF in 7H9 broth and L-J medium was almost 50% decayed after 1 week of storage at 37°C, and rifampin could not be detected in 7H9 or L-J medium after 3 weeks or 6 weeks of storage at 37°C. Approximately half of the drug was decomposed after 4 months of storage at 4°C for both media, and after 6 months of storage at 4°C, RIF in L-J medium was undetectable, while 38% of RIF remained in 7H9 medium. Approximately 21, 24, 29, and 35% RIF degradations were detected when the L-J medium was coagulated at 75°C, 80°C, 85°C, and 90°C, respectively. The DST outcomes when using L-J medium stored for different periods of time were consistent with the RIF concentration monitoring data. Rifampin in stock solution is stable for at least 3 months at a reduced storage temperature. Media containing RIF should be prepared strictly according to validated standard operating procedures. RIF degradation is a possible reason for false resistance categorizations of M. tuberculosis isolates in the clinical laboratory.Although the global incidence of tuberculosis (TB) is declining, drug resistance is rapidly emerging and spreading (1, 13). Insufficient control measures have led to an increase in the prevalence of drug-resistant strains and, more importantly, the extent of drug resistance (10). In certain high-burden countries, the nature of multidrug-resistant (MDR) tuberculosis has evolved from incidental to epidemic.Drug susceptibility testing (DST) for mycobacteria based on drug-containing Löwenstein-Jensen (L-J) medium is a method used ubiquitously around the world, especially in resourcelimited settings, where it is usually the only laboratory technique for the diagnosis of drug-resistant TB. The proportion method and the absolute concentration method are widely used DST methods based on L-J medium. However, discordance between laboratory diagnosis and clinical treatment outcomes of drug-resistant tuberculosis is not uncommon (3, 9). Clinically, some patients with MDR TB diagnosed on the basis of DST achieve cure with first-line antituberculosis drug regimens. The cause for this inconsistency is worthy of investigation.Rifampin (RIF) is one of the most commonly used anti-TB drugs and is the backbone of most successful TB treatment regimens. In addition, more than 90% of RIF-resistant Mycobacterium tuberculosis strains are also resistant to isoniazid (INH); hence, RIF resistance is a marker for MDR TB (12).Clearly, an acc...

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Section: Discussionsupporting

confidence: 81%

Rifampin Stability in 7H9 Broth and Löwenstein-Jensen Medium

Jiang

et al. 2011

J Clin Microbiol

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“…Indeed, due to the small difference between the critical concentration used for EMB drug susceptibility testing and the MIC, conventional drug susceptibility testing for EMB is less reliable, yields less reproducible results, and has a lower sensitivity when compared with other drugs. 1 Another reason for the difficulties in conventional EMB resistance testing might probably a lower stability of this drug during incubation at 37 C. 22 This might be further complicated by the presence of heteroresistant populations that, based on the amount of susceptible and resistant cells, might lead to false susceptible test results. In addition, sub culturing of heteroresistant strains is likely to cause non reproducible test results e.g.…”

Section: Resultsmentioning

confidence: 99%

Tuberculosis ethambutol resistance: Concordance between phenotypic and genotypic test results

Plinke

Cox

Kalon³

et al. 2009

Tuberculosis

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s u m m a r y embB306 mutations are potential markers for detecting ethambutol resistance in clinical Mycobacterium tuberculosis isolates. However, more recently, embB306 mutations have been found in ethambutol susceptible isolates and an association with broad drug resistance rather than ethambutol resistance has been reported.To further investigate this question, we analyzed the association between embB306 mutations and phenotypic ethambutol resistance among 197 isolates from a drug resistance survey performed in Karakalpakstan, Uzbekistan.39 strains had an embB306 mutation, out of which seven were ethambutol susceptible, thus, displaying discrepant test results. After re-analysis, the seven isolates were tested ethambutol resistant. All of these strains had an increased ethambutol MIC, however, three strains showed no or weak growth on the critical concentration of 2 mg/ml on Lö wenstein-Jensen. In three strains we confirmed the presence of heteroresistant mixed populations which might influence conventional ethambutol testing. Final concordance between molecular and phenotypic EMB testing was high with a sensitivity of 78% and a specificity of 100%.Our results confirm that embB306 mutations are useful markers for predicting ethambutol resistance. Discrepancies between molecular and phenotypic ethambutol resistance test results are most likely caused by problems with conventional susceptibility testing.

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“…The sensitivity (61.2%) and specificity (84.8%) of detection of EMB resistance were indeed lower than were seen with the other drugs; however, this does not necessarily mean that the assay has a low predictive value for clinically relevant EMB resistance. Conventional phenotypic EMB DST for M. tuberculosis is notoriously problematic (12,27). Several studies, including allelic exchange experiments, have demonstrated a strong association between embB mutations, specifically at codon 306, and EMB resistance (35-37, 44, 51, 52).…”

Section: Discussionmentioning

confidence: 99%

Detection of First- and Second-Line Drug Resistance in Mycobacterium tuberculosis Clinical Isolates by Pyrosequencing

Engström

Morcillo²,

Imperiale³

et al. 2012

J Clin Microbiol

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Conventional phenotypic drug susceptibility testing (DST) methods for Mycobacterium tuberculosis are laborious and very time-consuming. Early detection of drug-resistant tuberculosis (TB) is essential for prevention and control of TB transmission. We have developed a pyrosequencing method for simultaneous detection of mutations associated with resistance to rifampin, isoniazid, ethambutol, amikacin, kanamycin, capreomycin, and ofloxacin. Seven pyrosequencing assays were optimized for following loci: rpoB , katG , embB , rrs , gyrA , and the promoter regions of inhA and eis . The molecular method was evaluated on a panel of 290 clinical isolates of M. tuberculosis . In comparison to phenotypic DST, the pyrosequencing method demonstrated high specificity (100%) and sensitivity (94.6%) for detection of multidrug-resistant M. tuberculosis as well as high specificity (99.3%) and sensitivity (86.9%) for detection of extensively drug-resistant M. tuberculosis . The short turnaround time combined with multilocus sequencing of several isolates in parallel makes pyrosequencing an attractive method for drug resistance screening in M. tuberculosis .

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Stability of antimycobacterial drugs in susceptibility testing

Cited by 26 publications

References 5 publications

Rifampin Stability in 7H9 Broth and Löwenstein-Jensen Medium

Rifampin Stability in 7H9 Broth and Löwenstein-Jensen Medium

Tuberculosis ethambutol resistance: Concordance between phenotypic and genotypic test results

Detection of First- and Second-Line Drug Resistance in Mycobacterium tuberculosis Clinical Isolates by Pyrosequencing

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