Development of a multilocus sequence typing scheme for Mycobacterium abscessus complex strains and their association with the clinical characteristics and the antibiotic resistance patterns

Abstract

Mycobacterium abscessus (M. abscessus) is a rapid growing mycobacteria which causes a wide spectrum of disease in humans. Recent studies revealed that M. abscessus (hereafter referred to M. abscessus complex) was shown to comprise three closely related species: M. abscessus, Mycobacterium massiliense (M. massiliense), and Mycobacterium bolletii (M. bolletii). It was reported that M. abscessus, M. massiliense and M. bolletii had differences in antibiotic susceptibility, in treatment response and in clinical outcome. However, those clinical characteristics could be various even in the same species when the results of the previous studies were reviewd. These findings suggested that there could be different clinical characteristics and prognosis in different strains within the same species of M. abscessus complex.Multilocus sequence typing (MLST) is a PCR-based technique to identify sequence types (STs) of strains by compounding of allelic types of several housekeeping genes. The method is now available and widely used in many different bacterial species, because it provides reproducible and reliable results in studying infection epidemiology.Therefore, identifying STs of strains of M. abscessus complex through the MLST can be clinically important. However, there was no report about the MLST of M. abscessus complex and the association of M. abscessus complex strains with the clinical characteristics and the antibiotic resistance patterns. The purpose of this study is to develop an MLST scheme for M. abscessus complex for the typing of stains of these species and to determine the association of M. abscessus complex strains with the clinical characteristics and antibiotic resistance patterns.A total of 89 clinical isolates of M. abscessus complex from 71 patients of 2 tertiary care hospitals in South Korea were included. Forty-two isolates were identified as M. abscessus, and 29, as M. massiliense through sequencing of 8 housekeeping genes (argH, cya, glpK, gnd, murC, pgm, pta and purH) and rpoB. We excluded two genes that showed the lowest frequency of polymorphic sites before developing MLST scheme.The MLST scheme identified 26 different sequence types (STs) and 13 different clonal complexes (CCs) in M. abscessus and 12 different STs and 6 different CCs in M. massiliense. The MLST data showed high concordance with the XbaI-macrorestriction patterns of pulsed-field gel electrophoresis in the duplicated isolates.The association of M. abscessus strains/ CCs with disease progression was not distinct, but CC5 and CC8 had tendency to stable disease. And, the isolates which were not included in the clusters within CCs showed the trends of stable disease (strain number 2, 3 and 21) in terms of correlation of M. massiliense strains/ CCs with disease progression.The correlation of M. abscessus strains/ CCs with the antibiotics resistance patterns was not clear, nevertheless, susceptibility to many antibiotics was observed in CC2. And the correlation of M. massiliense strains/ CCs and antibiotic resistance patterns was not remarkable.In summary, MLST scheme developed in this study could identify different strains, and similar strains can be classified as CCs. The MLST also showed adequate reproducibility compared with the studies of PFGE using duplicated isolates. Although the strains/ CCs determined by MLST scheme were not clearly associated with clinical characteristics and antibiotic resistance patterns, some trends were observed. Therefore, this MLST scheme may be useful for studying the epidemiology of M. abscessus complex infections and for managing the patients with M. abscessus complex.