Analysis of the risk factors predisposing to fungal, bacterial & Acanthamoeba keratitis in south India

Abstract

Background & objective: Infective keratitis is rare in the absence of predisposing factors. The pattern of risk factors predisposing to infective keratitis varies with geographical regions and also influences the type of infection that occurs. The present study was aimed to identify the specific risk factors that predispose the infective keratitis (non viral) and to determine the association between the risk factors identified and the microbial aetiology of infective keratitis in a geographic region (south India).

Methods: A retrospective analysis of all patients clinically diagnosed infective keratitis (non viral) presenting between September 1999 and September 2002 was performed to identify risk factors. After diagnosing infective keratitis clinically, corneal scrapes were performed and subjected to microscopy and culture.

Results: A total of 3295 patients with infective keratitis were evaluated, of whom, 1138 (34.5%) patients had fungal growth alone, 1066 (32.4%) had bacterial growth alone, 33 (1%) had Acanthamoeba growth alone, 83 (2.5%) had mixed microbial growth and the remaining 975 (29.6%) had no growth. Corneal injury was identified in 2356 (71.5%) patients and it accounted for 91.9 per cent in fungal keratitis (P<0.0001) (OR: 73.5; 95%CI: 61.3-98.5), 28.1 per cent in bacterial keratitis and 100 per cent in Acanthamoeba keratitis (P<0.0001). Injuries due to vegetative matter (61.2%) was identified as significant risk for fungal keratitis (P<0.0001) (OR: 15.73; 95%CI: 12.7-19.49) and mud (84.85%) for Acanthamoeba keratitis (P<0.0001) (OR: 16.52; 95%CI: 6.35-42.99). Co-existing ocular diseases predisposing to bacterial keratitis accounted for 724 (69%) patients (P<0.0001) (OR: 33.31; 95%CI: 26.98-41.12). Bacterial pathogens alone were recovered from all 35 patients with contact lens associated keratitis (100%). Co-existing ocular diseases (78.3%) were frequently documented among patients older than 50 yr (P<0.0001) (OR: 27.0; 95%CI: 25.0-28.0) and corneal injury (89.7%) was frequently recorded among patients younger than 51 yr (P<0.0001) (OR: 72.0; 95%CI: 70.0-73.0).

Interpretation & conclusion: Corneal injury was found to be the principal risk factor for fungal and Acanthamoeba keratitis, while co-existing ocular diseases for bacterial keratitis. Corneal injury with vegetative matter was more often associated with fungal keratitis and injury with mud with Acanthamoeba keratitis.