title: Mycobacteria Clumping Increase Their Capacity to Damage Macrophages.
abstract: The rough morphotypes of non-tuberculous mycobacteria have been associated with the most severe illnesses in humans. This idea is consistent with the fact thatMycobacterium tuberculosispresents a stable rough morphotype. Unlike smooth morphotypes, the bacilli of rough morphotypes grow close together, leaving no spaces among them and forming large aggregates (clumps). Currently, the initial interaction of macrophages with clumps remains unclear. Thus, we infected J774 macrophages with bacterial suspensions of rough morphotypes ofM. abscessuscontaining clumps and suspensions of smooth morphotypes, primarily containing isolated bacilli. Using confocal laser scanning microscopy and electron microscopy, we observed clumps of at least five rough-morphotype bacilli inside the phagocytic vesicles of macrophages at 3 h post-infection. These clumps grew within the phagocytic vesicles, killing 100% of the macrophages at 72 h post-infection, whereas the proliferation of macrophages infected with smooth morphotypes remained unaltered at 96 h post-infection. Thus, macrophages phagocytose large clumps, exceeding the bactericidal capacities of these cells. Furthermore, proinflammatory cytokines and granuloma-like structures were only produced by macrophages infected with rough morphotypes. Thus, the present study provides a foundation for further studies that consider mycobacterial clumps as virulence factors.
authors.affiliation: Departament de Genètica i de Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona Bellaterra, Spain.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Brambilla
authors.affiliation: Departament de Genètica i de Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona Bellaterra, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Llorens-Fons
authors.affiliation: Departament de Genètica i de Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona Bellaterra, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Julián
authors.affiliation: Departament de Genètica i de Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona Bellaterra, Spain.
authors.forename: Estela
authors.initials: E
authors.lastname: Noguera-Ortega
authors.affiliation: Departament de Genètica i de Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona Bellaterra, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Tomàs-Martínez
authors.affiliation: Servei de Ressonància Magnètica Nuclear and Departament de Química, Universitat Autònoma de Barcelona Bellaterra, Spain.
authors.forename: Miriam
authors.initials: M
authors.lastname: Pérez-Trujillo
authors.affiliation: Division of Infection Diseases, Depatment of Medicine, The University of New Mexico School of Medicine, Albuquerque NM, USA.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Byrd
authors.affiliation: Servei de Microbiologia, Hospital Universitari de Bellvitge-Institut d'Investigació Biomèdica de Bellvitge, Universitat de Barcelona Barcelona, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Alcaide
authors.affiliation: Departament de Genètica i de Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona Bellaterra, Spain.
authors.forename: Marina
authors.initials: M
authors.lastname: Luquin
keywords: Mycobacterium abscessus; clumps; cords; infection of macrophages; rough morphotypes; smooth morphotypes; virulence factors