Abstract
Mycobacterium abscessus subsp. abscessus (MAB) is a clinically important nontuberculous mycobacterium (NTM) causing pulmonary infection in patients such as cystic fibrosis and bronchiectasis. MAB is naturally resistant to the majority of available antibiotics. In attempts to identify the fundamental response of MAB to aerobic, anaerobic, and biofilm conditions (as it is encountered in patients) and during exposure to antibiotics, we studied bacterial proteome using tandem mass tag mass spectrometry sequencing. Numerous de novo synthesized proteins belonging to diverse metabolic pathways were found in anaerobic and biofilm conditions, including glycolysis/gluconeogenesis, tricarboxylic acid (TCA) cycle, oxidative phosphorylation, nitrogen metabolism, and glyoxylate and dicarboxylate metabolism. Upon exposure to amikacin and linezolid under stress environments, MAB displayed metabolic enrichment for glycerophospholipid metabolism and oxidative phosphorylation. By comparing proteomes of two significant NTMs, MAB and M. avium subsp. hominissuis, we found highly synthesized shared enzymes of oxidative phosphorylation, TCA cycle, glycolysis/gluconeogenesis, glyoxylate/dicarboxylate, nitrogen metabolism, peptidoglycan biosynthesis, and glycerophospholipid/glycerolipid metabolism. The activation of peptidoglycan and fatty acid biosynthesis pathways indicates the attempt of bacteria to modify the cell wall, influencing the susceptibility to antibiotics. This study establishes global changes in the synthesis of enzymes promoting the metabolic shift and enhancing the pathogen resistance to antibiotics within different environments.
Highlights
The incidence and prevalence of patients with nontuberculous mycobacterial (NTM) infections has risen in recent years [1,2]
NTM strains of Mycobacterium abscessus complex (M. abscessus subsp. abscessus (MAB), M. abscessus subsp. bolletii and M. abscessus subsp. massiliense) are rapidly growing opportunistic human pathogens ubiquitously found in the environment, and are capable of causing a wide range of clinical diseases in both immunocompetent and immunocompromised hosts [3]
In order to fill an important gap in fundamental knowledge on how Mycobacterium abscessus subsp. abscessus (MAB) survive under nonreplicating and biofilm conditions, and how this phenotypic remodeling promotes antibiotic tolerance and increases bacterial survival, we investigated MAB proteome response under aerobic, anaerobic, and biofilm conditions, and compared these changes to bacterial responses under exposure to bactericidal concentrations of active antimicrobials under the same conditions
Summary
The incidence and prevalence of patients with nontuberculous mycobacterial (NTM) infections has risen in recent years [1,2]. Massiliense) are rapidly growing opportunistic human pathogens ubiquitously found in the environment, and are capable of causing a wide range of clinical diseases in both immunocompetent and immunocompromised hosts [3]. While MAB is a commonly isolated species from respiratory specimens, it can cause wide spectrum skin, ocular, and central nervous system infections, bacteremia, and diseases in almost every human organ [1]. MAB is characterized by extremely high intrinsic resistance to anti-tuberculosis and most antimicrobial agents [3,4], and is responsible for significantly higher fatality rates than any other rapidly growing mycobacteria [5,6]. Despite multi-drug regimens designed for MAB patients, it is common in clinics to observe individuals who either do not respond to therapy, or respond only partially with a success rate of 25% to 42% [12]. The natural resistance to the majority of available antimicrobials and inability of drugs to rapidly kill MAB, even at bactericidal concentrations, are major clinical challenges for MAB treatment
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