Comparative analysis of phenotypic and genotypic antibiotic susceptibility patterns in Mycobacterium avium complex

Abstract

Phenotypic (Sensititre Myco, pDST) and genotypic drug susceptibility testing (GenoType NTM DR, gDST) in M. avium complex (MAC) have become available as standardized assays, but comparable data is needed. This study aimed to investigate the phenotypic and genotypic drug susceptibility patterns in MAC clinical isolates. Methods: Overall, 98 isolates from 85 patients were included. pDST and gDST were performed on all isolates and results compared regarding specificity and sensitivity using pDST as a reference method. The impact of drug instability on pDST results was studied using a biological assay over 14 days. In addition, the evolution of antimicrobial resistance was investigated in sequential isolates of 13 patients. Results: Macrolide resistance was rare, 1.2% (95% CI 0.7-7.3) of isolates in the base cohort. No aminoglycoside resistances were found, but 14.1% of the studied isolates (95% CI 7.8-23.8) showed intermediate susceptibility. The GenoType NTM DR identified two out of four macrolide-resistant isolates. Antibiotic stability was demonstrated to be poor in rifampicin, rifabutin, and doxycycylin. Conclusions: pDST results in NTM for unstable antibiotics must be interpreted with care. A combination of pDST and gDST will be useful for the guidance of antimicrobial therapy in MAC-disease.

In Vitro Assessment of 17 Antimicrobial Agents Against Clinical Mycobacterium Avium Complex Isolates

“…Our antibiotic susceptibility testing results supported the current recommendation of using macrolides, rifamycins, and aminoglycosides to treat MAC infections. In our study, clarithromycin showed good inhibitory activity against all MAC isolates, consistent with previous studies [19,20]. The resistance rate of MAC isolates against rifampin was 82.9% (92/111), which was in agreement (78.9%; 216/274) with a previous study [21].…”

Clinical and Microbiological Characteristics of Mycobacterium kansasii Pulmonary Infections in China

“…These differences could be related to the prevailing susceptibility pattern of M. kansasii isolates found in a particular geographical area. In addition, RIF has been shown to be unstable in current media used in phenotypic drug susceptibility testing of SGM ( 27 , 28 ). RIF concentration in Middlebrook 7H9 medium had decreased by 92% after 7 days, and the microbiological assay revealed decreases in RIF concentration of ≥75% after 14 days ( 27 ).…”

Whole Genome Sequencing in the Management of Non-Tuberculous Mycobacterial Infections

“…Wetzstein et al studied the efficacy of WGS in predicting M. abscessus resistance to macrolides and aminoglycosides. The results obtained by WGS were shown to be in full agreement with the Genotype NTM-DR line probe assay and phenotypic drug susceptibility testing [75]. Lipworth et al used sequencing data obtained from M. abscessus species for the identification of new mutations in erm and rrs genes potentially associated with macrolide antibiotic resistance.…”