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The Genotype and Phenotype of Mycobacterium Xenopi in Ontario, Canada
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A2611 - The Genotype and Phenotype of Mycobacterium Xenopi in Ontario, Canada
Author Block: T. Hirama1, A. Marchand-Austin2, J. Ma2, D. Alexander3, S. Brode1, T. K. Marras1, F. Jamieson2; 1University of Toronto and Toronto Western Hospital, Toronto, ON, Canada, 2Public Health Ontario Laboratory, Toronto, ON, Canada, 3Cadham Provincial Laboratory, Winnipeg, ON, Canada.
RATIONALE Mycobacterium xenopi (M. xenopi) is recognized as a cause of predominantly pulmonary disease (PD) and commonly identified nontuberculous mycobacteria (NTM) in Europe and Canada. Despite its high prevalence and increasing clinical importance, little is known about the genetic diversity and molecular epidemiology of M. xenopi. Multi-locus sequence typing (MLST) is a DNA sequencing-based scheme for molecular typing of many bacterial species. A six-locus MLST strategy (MLST-6) was previously developed and divided M. xenopi isolates into 15 distinct sequence types (STs). Herein, we report on patients with M. xenopi pulmonary disease (Mxe-PD) and whether specific M. xenopi MLST types and pre-existing patient features are responsible for specific disease types.
METHODS This prospective cohort study was conducted in the NTM program at Toronto Western Hospital (where adults with Mxe-PD by ATS/IDSA criteria were invited to consent for the use of their clinical data) and the Public Health Ontario Laboratories (where M. xenopi was isolated genetically analyzed with MLST-6 containing atpD, fusA1, glnA1, pheT, secA1, and topA). STs were grouped and associations between ST and clinical features were studied with t-tests and chi-square tests.
RESULTS Between January 2011 and December 2015, 39 patients entered the study and had isolates available for analysis. The 39 M. xenopi isolates were genetically assigned to one 5 distinct STs. ST5 was the most common (21/39, 53.8%), followed by ST9 (n=9; 23.1%), ST2 (n=4; 10.3%), ST13 (n=4; 10.3%) and ST15 (n=1; 2.6%). We compared the clinical phenotype of patients with ST5 with that of the combined grouping of non-ST5 (ST2, ST9, ST13, ST15). ST5 was identified in patients with or without chronic pulmonary disease, whereas non-ST5 were identified almost exclusively in patients with underlying lung disease (11/21 [52%] vs 17/18 [94%], p=0.04). Based on radiological classification, the nodular-bronchiectasis (NB) pattern was most common (19/39, 48.7%), followed by fibrocavitary (FC) (17/39, 43.6%), and unclassified (3/39, 7.7%), with no statistical difference between ST groups.
CONCLUSION We found that ST5 was dominant, and appeared to cause PD in similar numbers in people with or without chronic lung disease. Disease with non-ST5 was found almost exclusively in patients with underlying pulmonary disease. It appears likely that a large multi-centre study would be required to adequately study associations between M. xenopi strain types and clinical disease features among Mxe-PD patients. We observed a surprisingly large proportion of patients with NB type of Mxe-PD, requiring further investigation.
Author Block: T. Hirama1, A. Marchand-Austin2, J. Ma2, D. Alexander3, S. Brode1, T. K. Marras1, F. Jamieson2; 1University of Toronto and Toronto Western Hospital, Toronto, ON, Canada, 2Public Health Ontario Laboratory, Toronto, ON, Canada, 3Cadham Provincial Laboratory, Winnipeg, ON, Canada.
RATIONALE Mycobacterium xenopi (M. xenopi) is recognized as a cause of predominantly pulmonary disease (PD) and commonly identified nontuberculous mycobacteria (NTM) in Europe and Canada. Despite its high prevalence and increasing clinical importance, little is known about the genetic diversity and molecular epidemiology of M. xenopi. Multi-locus sequence typing (MLST) is a DNA sequencing-based scheme for molecular typing of many bacterial species. A six-locus MLST strategy (MLST-6) was previously developed and divided M. xenopi isolates into 15 distinct sequence types (STs). Herein, we report on patients with M. xenopi pulmonary disease (Mxe-PD) and whether specific M. xenopi MLST types and pre-existing patient features are responsible for specific disease types.
METHODS This prospective cohort study was conducted in the NTM program at Toronto Western Hospital (where adults with Mxe-PD by ATS/IDSA criteria were invited to consent for the use of their clinical data) and the Public Health Ontario Laboratories (where M. xenopi was isolated genetically analyzed with MLST-6 containing atpD, fusA1, glnA1, pheT, secA1, and topA). STs were grouped and associations between ST and clinical features were studied with t-tests and chi-square tests.
RESULTS Between January 2011 and December 2015, 39 patients entered the study and had isolates available for analysis. The 39 M. xenopi isolates were genetically assigned to one 5 distinct STs. ST5 was the most common (21/39, 53.8%), followed by ST9 (n=9; 23.1%), ST2 (n=4; 10.3%), ST13 (n=4; 10.3%) and ST15 (n=1; 2.6%). We compared the clinical phenotype of patients with ST5 with that of the combined grouping of non-ST5 (ST2, ST9, ST13, ST15). ST5 was identified in patients with or without chronic pulmonary disease, whereas non-ST5 were identified almost exclusively in patients with underlying lung disease (11/21 [52%] vs 17/18 [94%], p=0.04). Based on radiological classification, the nodular-bronchiectasis (NB) pattern was most common (19/39, 48.7%), followed by fibrocavitary (FC) (17/39, 43.6%), and unclassified (3/39, 7.7%), with no statistical difference between ST groups.
CONCLUSION We found that ST5 was dominant, and appeared to cause PD in similar numbers in people with or without chronic lung disease. Disease with non-ST5 was found almost exclusively in patients with underlying pulmonary disease. It appears likely that a large multi-centre study would be required to adequately study associations between M. xenopi strain types and clinical disease features among Mxe-PD patients. We observed a surprisingly large proportion of patients with NB type of Mxe-PD, requiring further investigation.
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