Photoinactivation of Mycobacteria In Vitro and in a New Murine Model of LocalizedMycobacterium bovisBCG-Induced Granulomatous Infection

Abstract

Treatment of tuberculosis is currently hindered by prolonged antibiotic regimens and the emergence of significant drug resistance. Alternatives and adjuncts to standard antimycobacterial agents are needed. We propose that a direct attack utilizing photosensitizers and light-based treatments may be effective in curtailing Mycobacterium tuberculosis in discrete anatomical sites in the most infectious phase of pulmonary tuberculosis. To demonstrate experimental proof of principle, we have applied established photodynamic therapy (PDT) technology to in vitro cultures and an in vivo mouse model using Mycobacterium bovis BCG. We report here in vitro and in vivo PDT efficacy studies and the use of a three-dimensional collagen gel as a delivery vehicle for BCG, subcutaneously inserted, to induce specifically localized granuloma-like lesions in mice. When a benzoporphyrin derivative was utilized as the photosensitive agent, exposure to light killed extracellular and intracellular BCG in significant numbers. Collagen scaffolds containing BCG inserted in situ in BALB/c mice for 3 months mimicked granulomatous lesions and demonstrated a marked cellular infiltration upon histological examination, with evidence of caseating necrosis and fibrous capsule formation. When 10 5 BCG were present in the in vivo-induced granulomas, a significant reduction in viable mycobacterial cells was demonstrated in PDT-treated granulomas compared to those of controls. We conclude that PDT has potential in the treatment of localized mycobacterial infections, such as pulmonary granulomas and cavities.

Antibacterial photodynamic therapy: overview of a promising approach to fight antibiotic-resistant bacterial infections

“…Although not with M. tuberlucosis itself, researchers conducted proof-of-concept studies using bacteria from the same family. A mouse model of Mycobacterium bovis-induced granulomatous infection was successfully established using collagen scaffold gel to study Verteporfin-APDT efficacy [157]. A 0.7 log bactericidal effect was found in vivo that was comparable to in vitro result using 60 J/cm 2 light dose [157].…”

Photodynamic therapy as an adjunct to systemic treatment in a case with unilateral presumed vascularized choroidal tuberculous granuloma

“…PDT has been proved to be extremely successful in patients with several vascular fundus lesions such as choroidal hemangioma [10], vasoproliferative tumors [11], and retinal and disc hemangiomas [12,13]. Very recently, O'Riordan et al [14] proposed that a direct attack utilizing photosensitizers and light-based treatments may be effective in curtailing Mycobacterium tuberculosis in discrete anatomical sites in the most infectious phase of pulmonary tuberculosis; they applied established PDT technology to in-vitro and in-vivo mouse models using Mycobacterium bovis BCG. They demonstrated that verteporfin-PDT resulted in significant reduction of the numbers of viable mycobacterial cells of in vivo-induced subcutaneous granulomas and suggested that PDT may be effective not only in cutaneous mycobacterial disease but also in localized pulmonary sites, for example granulomas and cavities.…”

Mycoplasma Removal from Cell Culture Using Antimicrobial Photodynamic Therapy

“…In mycoplasmas, Mycoplasma fermentans, which frequently contaminates cell culture, 18 and Mycoplasma penetrans are known to have invasive properties. 19,20 Recently, O'Riordan et al 21 have reported that 50% of intracellular Mycobacterium bovis were killed using aPDT, compared with extracellular bacteria, when they are cocultured with macrophages, suggesting that aPDT may be applicable to killing intracellular bacteria. However, there are still few reports on the application of aPDT for killing intracellular bacteria, and further studies are needed to develop a method that is able to completely remove the mycoplasmas that have host cell-invasive properties from the contaminated cells.…”