Mycobacteria Clumping Increase Their Capacity to Damage Macrophages

Brambilla, Cecilia; Llorens-Fons, Marta; Julián, Esther; Noguera-Ortega, Estela; Tomàs-Martínez, Cristina; Pérez‐Trujillo, Míriam; Byrd, Thomas F.; Alcaide, Fernando; Luquin, Marina

doi:10.3389/fmicb.2016.01562

Cited by 46 publications

(67 citation statements)

References 49 publications

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“…A major hallmark of Mabs R is its high propensity to aggregate, leading to the formation of phagocytic cups and the presence of social phagosomes containing usually more than one bacillus. These phagocytic cups and bacterial laden phagosomes are associated with increased cell mortality, evoking a typical trait of RGM (Brambilla et al, 2016; Roux et al, 2016). In contrast, loner phagosomes containing one bacilli are usually found within macrophages infected with the S form (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

The Diverse Cellular and Animal Models to Decipher the Physiopathological Traits of Mycobacterium abscessus Infection

Bernut

Herrmann

Ordway

et al. 2017

Front. Cell. Infect. Microbiol.

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Mycobacterium abscessus represents an important respiratory pathogen among the rapidly-growing non-tuberculous mycobacteria. Infections caused by M. abscessus are increasingly found in cystic fibrosis (CF) patients and are often refractory to antibiotic therapy. The underlying immunopathological mechanisms of pathogenesis remain largely unknown. A major reason for the poor advances in M. abscessus research has been a lack of adequate models to study the acute and chronic stages of the disease leading to delayed progress of evaluation of therapeutic efficacy of potentially active antibiotics. However, the recent development of cellular models led to new insights in the interplay between M. abscessus with host macrophages as well as with amoebae, proposed to represent the environmental host and reservoir for non-tuberculous mycobacteria. The zebrafish embryo has also appeared as a useful alternative to more traditional models as it recapitulates the vertebrate immune system and, due to its optical transparency, allows a spatio-temporal visualization of the infection process in a living animal. More sophisticated immunocompromised mice have also been exploited recently to dissect the immune and inflammatory responses to M. abscessus. Herein, we will discuss the limitations, advantages and potential offered by these various models to study the pathophysiology of M. abscessus infection and to assess the preclinical efficacy of compounds active against this emerging human pathogen.

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Section: Introductionmentioning

confidence: 99%

The Diverse Cellular and Animal Models to Decipher the Physiopathological Traits of Mycobacterium abscessus Infection

Bernut

Herrmann

Ordway

et al. 2017

Front. Cell. Infect. Microbiol.

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“…S and R morphotypes of M. abscessus 390 and DSMZ 44196 T were obtained in previous studies (Byrd and Lyons, 1999; Brambilla et al, 2016). For the clinical isolate M. abscessus BE48, the strain was initially R, but we obtained the S morphotype after several passages on agar medium.…”

Section: Methodsmentioning

confidence: 91%

“…The analysis described three types of aggregates, depending on their area: fewer than 3 μm 2 , between 3 and 6 μm 2 , and more than 6 μm 2 (Brambilla et al, 2016). The area covered by each type of aggregate was added, and the statistical analysis was performed to determine the percentages of area that were covered by each type of aggregate.…”

Section: Methodsmentioning

confidence: 99%

“…In contrast, phagosomes of macrophages infected with the S morphotype contain mainly isolated bacilli (Byrd and Lyons, 1999; Brambilla et al, 2016; Roux et al, 2016). This distinct fate has been related to the highly aggregative nature of R morphotype bacilli, which grow close together, leave no spaces among them and form large aggregates (clumps) (Sánchez-Chardi et al, 2011; Brambilla et al, 2016). At 48–72 h.p.i, macrophages infected with the R morphotype are destroyed, thus releasing large clumps of bacilli outside the cells; however, macrophages infected with the S morphotype are unaffected.…”

Section: Introductionmentioning

confidence: 99%

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Trehalose Polyphleates, External Cell Wall Lipids in Mycobacterium abscessus, Are Associated with the Formation of Clumps with Cording Morphology, Which Have Been Associated with Virulence

et al. 2017

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Mycobacterium abscessus is a reemerging pathogen that causes pulmonary diseases similar to tuberculosis, which is caused by Mycobacterium tuberculosis. When grown in agar medium, M. abscessus strains generate rough (R) or smooth colonies (S). R morphotypes are more virulent than S morphotypes. In searching for the virulence factors responsible for this difference, R morphotypes have been found to form large aggregates (clumps) that, after being phagocytozed, result in macrophage death. Furthermore, the aggregates released to the extracellular space by damaged macrophages grow, forming unphagocytosable structures that resemble cords. In contrast, bacilli of the S morphotype, which do not form aggregates, do not damage macrophages after phagocytosis and do not form cords. Cording has also been related to the virulence of M. tuberculosis. In this species, the presence of mycolic acids and surface-exposed cell wall lipids has been correlated with the formation of cords. The objective of this work was to study the roles of the surface-exposed cell wall lipids and mycolic acids in the formation of cords in M. abscessus. A comparative study of the pattern and structure of mycolic acids was performed on R (cording) and S (non-cording) morphotypes derived from the same parent strains, and no differences were observed between morphotypes. Furthermore, cords formed by R morphotypes were disrupted with petroleum ether (PE), and the extracted lipids were analyzed by thin layer chromatography, nuclear magnetic resonance spectroscopy and mass spectrometry. Substantial amounts of trehalose polyphleates (TPP) were recovered as major lipids from PE extracts, and images obtained by transmission electron microscopy suggested that these lipids are localized to the external surfaces of cords and R bacilli. The structure of M. abscessus TPP was revealed to be similar to those previously described in Mycobacterium smegmatis. Although the exact role of TPP is unknown, our results demonstrated that TPP are not toxic by themselves and have a function in the formation of clumps and cords in M. abscessus, thus playing an important role in the pathogenesis of this species.

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“…Infections with NTM can be very difficult to treat; M. abscessus lung infections, in particular, require long courses of antibiotic cocktails that have limited efficacy and extensive adverse side effects (24, 27, 28). The ability of M. abscessus to aggregate into cord-like aggregates correlates with increased pathogenicity in a zebrafish model and an enhanced ability to evade phagocytosis (19–21), indicating that the formation of multicellular structures by NTM is positively related to their sustained infection of hosts.…”

Section: Introductionmentioning

confidence: 99%

Aggregation of nontuberculous mycobacteria is regulated by carbon:nitrogen balance

DePas

Bergkessel

Newman

2019

Preprint

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19Nontuberculous mycobacteria (NTM) are emerging opportunistic pathogens that 20 form biofilms in environmental reservoirs such as household water systems and 21 aggregate into phagocytosis-resistant clusters during infection. NTM constitutively 22 aggregate in vitro, a phenotype typically considered to be a by-product of the mycolic-23 acid-rich cell wall. While culturing a model NTM, Mycobacterium smegmatis, in rich 24 medium, we fortuitously discovered that planktonic cells accumulated in the culture after 25 ~3 days. By providing selective pressure for bacteria that disperse earlier, we isolated a 26 strain with two mutations in the oligopeptide permease operon (opp). A mutant lacking 27 the opp operon (Δopp) dispersed earlier and more completely than wildtype (WT). We 28show that Δopp's aggregation defect was nutrient related; aggregation was restored by 29 non-peptide carbon sources. Experiments with WT M. smegmatis revealed that growth 30 as aggregates is favored when carbon is replete, while dispersal can be induced by 31 carbon starvation. In addition, under conditions of low available carbon relative to 32 available nitrogen, M. smegmatis grows as planktonic cells. By adjusting carbon and 33 nitrogen sources in defined medium, we tuned the cellular C:N ratio such that M. 34 smegmatis grows either as aggregates or planktonic cells. Lastly, we tested the effect of 35 C:N balance on aggregation in clinically relevant NTM. Altogether, we show that NTM 36 aggregation is a controlled process that is regulated by the relative availability of carbon 37 and nitrogen for metabolism. Because NTM aggregation is correlated with increased 38 virulence, these results may contribute to targeted anti-biofilm therapeutics. 39 40 Importance: 41 Free-living bacteria can assemble into multicellular aggregates called biofilms. 42 Biofilms help bacteria tolerate multiple stresses, including antibiotics and the host 43 immune system. Differing environmental pressures have resulted in biofilm architecture 44 and regulation varying among bacterial species and strains. Nontuberculous 45 mycobacteria are a group of emerging opportunistic pathogens that utilize biofilms to 46 adhere to household plumbing and showerheads and to avoid phagocytosis by host 47 immune cells. Mycobacteria harbor a unique cell wall built chiefly of long chain mycolic 48 acids that confers hydrophobicity and has been thought to cause constitutive 49 aggregation in liquid media. Here we show that aggregation is instead a regulated 50 process dictated by the balance of available carbon and nitrogen. Understanding that 51 mycobacteria utilize metabolic cues to regulate the transition between planktonic and 52 aggregated cells reveals an inroad to controlling aggregation through targeted 53 therapeutics. 54 55 56 57 58 59 60 61 4Introduction: 62 The adhesive biofilm matrix can serve as a physical barrier against external 63 stresses such as desiccation and predation, can interact with and sequester 64 antimicrobial agents, and can short-circuit phagocyte...

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Mycobacteria Clumping Increase Their Capacity to Damage Macrophages

Cited by 46 publications

References 49 publications

The Diverse Cellular and Animal Models to Decipher the Physiopathological Traits of Mycobacterium abscessus Infection

The Diverse Cellular and Animal Models to Decipher the Physiopathological Traits of Mycobacterium abscessus Infection

Trehalose Polyphleates, External Cell Wall Lipids in Mycobacterium abscessus, Are Associated with the Formation of Clumps with Cording Morphology, Which Have Been Associated with Virulence

Aggregation of nontuberculous mycobacteria is regulated by carbon:nitrogen balance

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