Prevalence of bacterial pathogens causing ocular infections in South India

The eye may be infected from external sources or through intra-ocular invasion of micro-organisms carried by the blood stream. This study was undertaken to isolate and identify the specific bacterial pathogens causing ocular infections and to determine their in-vitro antibacterial susceptibilities to commonly used antibacterial agents.

A retrospective analysis of all patients with clinically diagnosed bacterial ocular infections such as blepharitis, conjunctivitis, internal and external hordeolum, suppurative scleritis, canaliculitis, keratitis, dacryocystitis, preseptal cellulitis, endophthalmitis and panophthalmitis presenting between January 2005 and December 2005 was performed. Extra-ocular and intra-ocular specimens were collected and were subjected to direct microscopy and culture.

A total of 756 patients with bacterial ocular infections were analyzed, of which 462(61%) eyes had adnexal bacterial infection, 217(28.7%) had corneal infection, 6 (0.8%) had scleral involvement and the remaining 71(9.39%) eyes had infection of the intra-ocular tissues. The predominant bacterial species isolated was S. aureus (195 of 776; 25%) followed by S. pneumoniae (169 of 776; 21.78%) and coagulase negative staphylococci (142 of 776; 18.3%). The largest number of gram-positive isolates were susceptible to cefazolin (545 of 624; 87.34%), chloramphenicol (522 of 624; 83.65%) and gatifloxacin (511 of 624; 81.89%) and gram-negative isolates were to amikacin (127 of 136; 93.38%), gatifloxacin (125 of 136; 91.91%) and ofloxacin (119 of 136; 87.5%), while aerobic actinomycetes were to amikacin (100%), gatifloxacin (14 of 16; 87.5%), chloramphenicol (14 of 16; 87.5%) and ofloxacin (13 of 16; 81.25%).

S. aureus frequently causes infections of eyelids and conjunctiva, S. pneumoniae of lacrimal apparatus and cornea and coagulase negative staphylococci causes intra-ocular infections. Of all routinely used antibacterials tested, flouroquinolones, especially gatifloxacin and ofloxacin represented a good choice for treating bacterial ocular infections.