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Analysis of drug treatment outcome in clarithromycin-resistant Mycobacterium avium complex lung disease.

ABSTRACT: Although the isolation of clarithromycin (CAM)-resistant Mycobacterium avium complex (MAC) indicates a poor treatment outcome and increased mortality, there have been only a few reports on drug treatment for CAM-resistant MAC lung disease. We aimed to reveal the effectiveness of the continuation of a macrolide and the use of a multidrug regimen in the treatment of CAM-resistant MAC lung disease.Among patients with MAC pulmonary disease as defined by the 2007 criteria of the American Thoracic Society and the Infectious Diseases Society of America statement, those with CAM-resistant MAC (minimum inhibitory concentration ≥32 μg/ml) isolated, newly diagnosed and treated from January 2009 to June 2013 were analysed in this study. Effectiveness was measured based on culture conversion rate and improvement of radiological findings.Thirty-three HIV-negative patients were analysed in this study. Twenty-six were treated with a regimen containing CAM or azithromycin (AZM), and 21 patients were treated with three or more drugs except macrolide. The median duration to be evaluated was 10.4 months after beginning the treatment regimen. Sputum conversion (including cases of inability to expectorate sputum) was achieved in 12 (36%) patients. Radiological effectiveness improved in 4 (12%) patients, was unchanged in 11 (33%) patients and worsened in 18 (55%) patients. In the multivariate analysis, CRP <1.0 mg/dl (p = 0.017, odds ratio 12, 95% confidence interval (CI) 1.6-95) was found to be the only significant risk factor for radiological non-deterioration, and no significant risk factors for microbiological improvement were found.Our results suggested that continuation of macrolides or the addition of a new quinolone or injectable aminoglycoside to therapy with rifampicin and ethambutol would not improve clinical outcome after the emergence of CAM-resistant MAC. However, further prospective study is required to evaluate the precise clinical efficacy and effectiveness of these drugs.

SUBMITTER: Kadota T

PROVIDER: S-EPMC4730784 | biostudies-other | 2016

REPOSITORIES: biostudies-other

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Project description:Mycobacterium avium complex (MAC) thrives in various environments and mainly causes lung disease in humans. Because macrolide antibiotics such as clarithromycin or azithromycin are key drugs for MAC lung disease, the emergence of macrolide-resistant strains prevents the treatment of MAC. More than 95% of macrolide-resistant MAC strains are reported to have a point mutation in 23S rRNA domain V. This study successfully developed a melting curve assay using nonfluorescent labeled probes to detect the MAC mutation at positions 2058 to 2059 of the 23S rRNA gene (AA genotype, clarithromycin susceptible; TA, GA, AG, CA, AC, and AT genotypes, clarithromycin resistant). In the AA-specific probe assay, the melting peak of the DNA fragment of the AA genotype was higher than that of DNA fragments of other genotypes. Melting temperature (Tm) values of the AA genotype and the other genotypes were about 80°C and 77°C, respectively. DNA fragments of each genotype were identified correctly in six other genotype-specific probes (TA, GA, AG, CA, AC, and AT) assays. Using genomic DNA from six genotype strains of M. avium and four genotype strains of M. intracellulare, we confirmed that all genomic DNAs could be correctly identified as individual genotypes according to the highest Tm values among the same probe assays. These results indicate that this melting curve-based assay is able to determine MAC genotypes at positions 2058 to 2059 of the 23S rRNA gene. This simple method could contribute to the rapid detection of clarithromycin-resistant MAC strains and help to provide accurate drug therapy for MAC lung disease. IMPORTANCE Since macrolide antibiotics such as clarithromycin or azithromycin are key drugs in multidrug therapy for Mycobacterium avium complex (MAC) lung diseases, the rapid detection of macrolide-resistant MAC strains has important implications for the treatment of MAC. Previous studies have reported a correlation between drug susceptibility testing and the mutation of macrolide resistance genes. In this study, we developed a novel melting curve-based assay using nonfluorescent labeled probes to identify both clarithromycin-resistant M. avium and M. intracellulare with mutations in the 23S rRNA gene, which is the clarithromycin or azithromycin resistance gene. This assay contributed to not only the detection of MAC mutations but also the determination of all genotypes at positions 2058 to 2059 of the 23S rRNA gene. Furthermore, because nonfluorescent labeled probes are used, this assay is more easily and more immediately available than other methods.

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Analysis of drug treatment outcome in clarithromycin-resistant Mycobacterium avium complex lung disease.

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