[Experimental study of non-tuberculous mycobacterial keratitis in rabbits].

Objective: To study clinical manifestation and pathology change of different time points of rabbit keratitis caused by non-tuberculous mycobacteria (NTM).

Methods: Forty-eight eyes from 48 rabbits were randomly divided into three groups:under-flap infection group (UFI group), under-flap infection group with corticosteroid (UFIC group) and surface infection group (SI group). The cornea infiltration area of all rabbits was observed. Bacterial quantitative culture and histopathological examination were performed.

Results: In the earliest stage (5 days), the cornea was cloudy and edematous. In the middle stage (7 - 14 days), cornea stromal infiltration became its major clinical sign. In the last stage (21 days), corneal neovascularization and fibrosis were developed. The mean stromal infiltration area in UFIC group was greater than those of UFI group and SI group (F = 9.362, 8.341, P < 0.05). The number of NTM in UFIC group was higher than those of UFI group and SI group (F = 411.272, P < 0.05). In histopathological examination, there were infiltrates with polymorphonuclear leukocytes (PMN) in the corneal stroma in the early stage and acid-fast bacilli was found. A plenty of lymphocytes in the cornea was found in the middle stage of NTM keratitis. In the latter stage, the fibroblast cells proliferation and corneal ulcer were cured. During the course of this infection, the number of CD4+, CD8+ T lymphocyte increased significantly, and then decreased gradually following the regress of the infection. In the stage (5 - 21 days), CD4+ T lymphocyte decreased significantly in UFIC group compared with other two groups (F = 21.907, 196.521, 12.552, 11.100, P < 0.01).

Conclusions: The clinical characteristic of rabbit keratitis is the multifocal dense superficial stromal infiltrates. CD4+ T lymphocyte may play an important role in NTM keratitis.