Comparison of in vitro susceptibilities of Gram-positive cocci isolated from ocular infections against the second and fourth generation quinolones at a tertiary eye care centre in South India

Abstract

To compare the in vitro antimicrobial susceptibilities of Gram-positive cocci isolated from the ocular infections to the second and fourth generation fluoroquinolones at a tertiary eye care centre in south India. A retrospective review of microbiology records at LV Prasad eye institute, Hyderabad, India, identified 787 Gram-positive cocci isolated from different ocular infections between January 2005 to May 2008.The isolates were identified using culture characteristics and biochemical tests. In vitro antibiotic susceptibility of the isolates was determined by using Kirby-Bauer disc diffusion method. We analysed the susceptibility data of ciprofloxacin, ofloxacin, gatifloxacin, and moxifloxacin. Out of 787 isolates, 147 (18.7%) were Staphylococcus aureus, 279 (35.2%) were coagulase-negative Staphylococci, 357 (45.4%) were Streptococcus pneumoniae,and 4 (0.4%) were other Streptococcus species. Of the four quinolones, susceptibility to gatifloxacin was highest (85.6%) followed by ofloxacin (65.6%), moxifloxacin (63.9%), and ciprofloxacin (60.5%). In all, 33 (4.2%) of 787 isolates were resistant to all the four fluoroquinoles. S. aureus and coagulase-negative Staphylococcus isolates that were resistant to ciprofloxacin and ofloxacin were most susceptible to gatifloxacin. S. pneumoniae were more susceptible to gatifloxacin, ofloxacin, and ciprofloxacin than moxifloxacin. In our institute, we observed that gatifloxacin is more potent than moxifloxacin against Gram-positive cocci isolated from ocular infections.