Inducible and Acquired Clarithromycin Resistance in the Mycobacterium abscessus Complex

Abstract

PurposeClarithromycin was considered the cornerstone for the treatment of Mycobacterium abscessus complex infections. Genetic resistance mechanisms have been described and many experts propose amikacin as an alternative. Nevertheless, clarithromycin has several advantages; therefore, it is necessary to identify the non-functional erm(41) allele to determine the most suitable treatment. The aims of this study were to characterize the molecular mechanisms of clarithromycin resistance in a collection of Mycobacterium abscessus complex isolates and to verify the relationship between these mechanisms and the antibiogram.Materials and MethodsClinical isolates of M. abscessus complex (n = 22) from 16 patients were identified using four housekeeping genes (rpoB, secA1, sodA and hsp65), and their genetic resistance was characterized by studying erm(41) and rrl genes. Nine strains were recovered from the clinical isolates and subjected to E-test and microdilution clarithromycin susceptibility tests, with readings at 3, 7 and 14 days.ResultsWe classified 11/16 (68.8%) M. abscessus subsp. abscessus, 4/16 (25.0%) M. abscessus subsp. bolletii, and 1/16 (6.3%) M. abscessus subsp. massiliense. T28 erm(41) allele was observed in 8 Mycobacterium abscessus subps. abscessus and 3 Mycobacterium abscessus subsp. bolletii. One strain of M. abscessus subsp. bolletii had an erm(41) gene truncated and was susceptible to clarithromycin. No mutations were observed in rrl gene first isolates. In three patients, follow-up of initial rrl wild-type strains showed acquired resistance.ConclusionsMost clinical isolates of M. abscessus complex had inducible resistance to clarithromycin and total absence of constitutive resistance. Our findings showed that the acquisition of resistance mutations in rrl gene was associated with functional and non-functional erm(41) gene. Caution is needed when using erm(41) sequencing alone to identify M. abscessus subspecies. This study reports an acquired mutation at position 2057 of rrl gene, conferring medium-low clarithromycin constitutive resistance.

Selection of Resistance to Clarithromycin in Mycobacterium abscessus Subspecies

“…massiliense were susceptible to clarithromycin and harbored an erm (41) (41) sequevars with regard to a T/C polymorphism at nucleotide 28: erm(41) sequevar T28 (Trp 10 codon) associated with inducible resistance and erm(41) sequevar C28 (Arg 10 codon) associated with clarithromycin susceptibility. These results were confirmed using isolates from other countries (19)(20)(21)(22).…”

Cross-transmission is not the source of newMycobacterium abscessusinfections in a multi-centre cohort of cystic fibrosis patients

“…M. abscessus is an important pathogen that has emerged in the CF patient population that has been associated with poor clinical outcomes, especially following lung transplantation [3–5]. This is due, at least in part, to the extensive antibiotic resistance that makes infections with this organism difficult to treat [2,6]. CF patients infected with M. abscessus are frequently not listed for transplant, therefore the acquisition of this pathogen is considered to be a serious complication in this group.…”

Evaluation of the GenoType® NTM DR for Subspecies Identification and Determination of Drug Resistance in Clinical M. abscessus Isolates

“…As rrl positions 2058 and 2059 were wildtype and pDST for Clarithromycin did not show resistance on days 3-5, genotypic and phenotypic test results were considered concordant. However, this rarely occurring mutation has previously been described as conferring medium to low level resistance to Clarithromycin in M. abscessus (MIC 8 μg/ml) [13,23]. Further studies are needed to reveal the significance of this point mutation in clinical M. abscessus isolates.…”

“…Acquired high-level resistance to aminoglycosides is conferred by point mutations at position 1408 of the 16S rRNA (rrs) gene and can occur in all three subspecies [12]. Today, subspecies identification and detection of genetic resistance markers for M. abscessus are based on sequencing of these specific target genes [13]. Recently a commercial line probe assay, the GenoType® NTM DR (HAIN Lifescience, Nehren, Germany) has been developed.…”