Quantitative analysis of Mycobacterium avium subsp. hominissuis proteome in response to antibiotics and during exposure to different environmental conditions

Rajoana Rojony,Pankaj Jaiswal,Luiz E Bermudez,Jacob M Wozniak,L Danelishvili,Matthew Martin,David J Gonzalez,Anaamika Campeau

doi:10.1186/s12014-019-9260-2

Rajoana Rojony, Pankaj Jaiswal + Show 6 more

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https://doi.org/10.1186/s12014-019-9260-2

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Abstract

Mycobacterium avium subsp. hominissuis (MAH) belongs to the clinically important non-tuberculous mycobacterial group that infects immunocompromised patients and individuals with underling lung conditions. The need for prolonged therapy is a major challenge of MAH treatment, influencing the development of persistent and drug-resistant infections. The reason why bactericidal drugs take several months to eliminate MAH is unknown. To investigate MAH proteome remodeling under aerobic, anaerobic and biofilm conditions (as it is encountered in patient lungs) and identify metabolic changes potentially associated with bacterial persistent state, we performed the relative protein quantitative analysis using Tandem Mass Tag Mass Spectrometry sequencing. MAH was exposed to amikacin (4 μg/ml) and clarithromycin (16 μg/ml) under aerobic, anaerobic or biofilm condition for 24 h and the response was compared with bacterial proteomics of the corresponding conditions. Overall, 4000 proteins were identified out of 5313 MAH proteome of across all experimental groups. Numerous sets of de novo synthesized proteins belonging to metabolic pathways not evidenced in aerobic condition were found commonly enriched in both anaerobic and biofilm conditions, including pantothenate and CoA biosynthesis, glycerolipid metabolism, nitrogen metabolism and chloroalkene degradation, known to be associated with bacterial tolerance in M. tuberculosis. The common pathways observed in anaerobic and biofilm conditions following drug treatments were peptidoglycan biosynthesis, glycerophospholipid metabolism and protein export. The LprB lipoprotein, highly synthesized in MAH biofilms during drug treatments and shown to be essential for M. tuberculosis virulence and survival in vivo, was selected and overexpressed in MAH. Results demonstrate that LprB is secreted in MAH biofilms and the overexpression clone is more tolerant to antimicrobials than the wild-type strain. Our study identified promising metabolic pathways that can be targeted to prevent the bacterial tolerance mechanism and, subsequently, reduce the length of MAH therapy.

Highlights

Mycobacterium avium subsp. hominissuis (MAH), ubiquitously found in the environment, is an opportunistic pathogen associated with infections in human and other mammals [1]
While significant reduction in bacterial viability was observed in the aerobic condition following AMK and CLA exposure over time (p < 0.01 at day 4), only a slight decline in MAH colony forming unit (CFU)/ml was seen for each treatment group of the anaerobic and biofilm conditions when compared to no antibiotic control
MAH grown under aerobic conditions had significant killing kinetics in macrophages when exposed to antimicrobials (Fig. 1b); even after 7 days of exposure to bactericidal concentrations of antimicrobials, host cells were unable to clear the infection resulting in 2- and 3.5-log decrease of intracellular bacteria during AMK and CLA treatment at day 7, respectively

Summary

Introduction

Mycobacterium avium subsp. hominissuis (MAH), ubiquitously found in the environment, is an opportunistic pathogen associated with infections in human and other mammals [1]. Treatment of MAH cavitary lesions with a macrolide and an aminoglycoside results many times in unsatisfactory outcome [3, 6]. The main challenge of treating MAH patients is the inability to rapidly eliminate the infection; even when bactericidal concentrations of compounds are employed, resulting in use of the prolonged treatment. The required extended period of therapy and multidrug treatment result in more favorable outcome for many patients, usually it eradicates MAH infection in only 40% to 60% of individuals [3, 7]. A low metabolic state during stress conditions is a common response observed in MAH. MAH can survive rapid shifts in and out of low oxygen condition for prolonged periods of time, by altering their metabolism from aerobic to anaerobic [9]. On the other hand, prevents the optimal penetration of antibiotics and interferes with drug killing mechanisms [10, 11]

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