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J Clin Microbiol. 2015 Nov;53(11):3438-47. doi: 10.1128/JCM.02015-15. Epub 2015 Aug 19.

Clonal Diversification and Changes in Lipid Traits and Colony Morphology in Mycobacterium abscessus Clinical Isolates.

Author information

1
Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
2
Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland, USA.
3
Microbiology Service, Department of Laboratory Medicine, Clinical Center, National Institutes of Health, Bethesda, Maryland, USA.
4
Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, Maryland, USA.
5
Pulmonary Clinical Medicine Section, Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA.
6
Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA Leprosy Laboratory, Oswaldo Cruz Institute, FIOCRUZ, Rio de Janeiro, Brazil.
7
Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA Microbiology Service, Department of Laboratory Medicine, Clinical Center, National Institutes of Health, Bethesda, Maryland, USA azelazny@mail.nih.gov.

Abstract

The smooth-to-rough colony morphology shift in Mycobacterium abscessus has been implicated in loss of glycopeptidolipid (GPL), increased pathogenicity, and clinical decline in cystic fibrosis (CF) patients. However, the evolutionary phenotypic and genetic changes remain obscure. Serial isolates from nine non-CF patients with persistent M. abscessus infection were characterized by colony morphology, lipid profile via thin-layer chromatography and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), sequencing of eight genes in the GPL locus, and expression level of fadD23, a key gene involved in the biosynthesis of complex lipids. All 50 isolates were typed as M. abscessus subspecies abscessus and were clonally related within each patient. Rough isolates, all lacking GPL, predominated at later disease stages, some showing variation within rough morphology. While most (77%) rough isolates harbored detrimental mutations in mps1 and mps2, 13% displayed previously unreported mutations in mmpL4a and mmpS4, the latter yielding a putative GPL precursor. Two isolates showed no deleterious mutations in any of the eight genes sequenced. Mixed populations harboring different GPL locus mutations were detected in 5 patients, demonstrating clonal diversification, which was likely overlooked by conventional acid-fast bacillus (AFB) culture methods. Our work highlights applications of MALDI-TOF MS beyond identification, focusing on mycobacterial lipids relevant in virulence and adaptation. Later isolates displayed accumulation of triacylglycerol and reduced expression of fadD23, sometimes preceding rough colony onset. Our results indicate that clonal diversification and a shift in lipid metabolism, including the loss of GPL, occur during chronic lung infection with M. abscessus. GPL loss alone may not account for all traits associated with rough morphology.

PMID:
26292297
PMCID:
PMC4609687
DOI:
10.1128/JCM.02015-15
[Indexed for MEDLINE]
Free PMC Article

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