Marc Rubio Bueno. Curs 2013-14


Resumen del proyecto
Background: Mycobacterium abscessus subspecies are the most resistant organisms among rapid growing mycobacteria (RGM). They are responsible for chronic pulmonary and cutaneous infections, but their correct identification and treatment remains a challenge.
Objetives: The aims of this study were to analyze subspecies distribution among the clinical isolates in our setting, to characterize clarithromycin molecular resistance and to describe the relationship between antibiograms and molecular mechanisms.
Methods: Clinical isolates of M. abscessus complex (n=22) from 16 patients were identified using four housekeeping genes (rpoB, secA1, sodA and hsp65) and characterized for molecular resistance studying erm(41) and rrl genes. From the clinical isolates, 9 strains were recovered and subjected to E-test and microdilution clarithromycin susceptibility tests, with readings at 3, 7 and 14 days.
Results: We classified 11/16 (68.75%) M. abscessus subsp. abscessus, 4/16 (25.00%) M. abscessussubsp. bolletii and 1/16 (6.25%) M. abscessus subsp. massiliense. No mutations were observed in therrl. T28 erm(41) strains (11/16) showed inducible resistance. One strain of M. abscessus subsp. bolletiiwas susceptible to clarithromycin. Patient follow-up with initial rrl wild-type isolate showed acquired resistance associated with inducible and non-inducible erm(41) resistance; one acquired resistance mutation was in position 2057 in rrl gene.

ConclusionsMost clinical isolates of M. abscessus complex in Barcelona have inducible resistance to clarithromycin and total absence of constitutive resistance. Our findings also show that acquired resistance mutations in the rrl gene are associated with inducible and non-inducible erm(41) resistance. Caution is needed when using erm(41) sequencing alone to identify M. abscessus subspecies.

Back to top