The Efficacy of Polyhexamethylene Biguanide on Experimental Staphylococcus Aureus Keratitis

ABSTRACT

To evaluate the efficacy of oplyhexamethylene biguanide(PHMB) in Staphylococcus aureus (S. aureus) keratitis model, 10microliter of S. sureus bacterial suspension(1x10(5) colony-forming unit(cfu)/ml) were infected intrastromally into rabbit corneas. 18 rabbits were divided into three treatment groups balanced salt solution (BSS) group(n=18 eyes), PHMB(0.02%, 200microgram/ml) group(n=9), cefazolin(40 microgram/ml) group(n=9). Topical antibiotic drops were given hourly starting at 24 hours after inoculation. A subconjunctival injection was given every 24 hours for the study duration(96 hours). The severity of keratitis was scored in masked fashion every 12 hours. Corneal buttons were excised and homogenized at the end of the study to determine viable bacterial counts. In the S. aureus keratitis model, there was no difference of clinical scores between BSS, cefazolin, PHMB group at 72 hours, and the number of viable bacteria recovered from the corneal button in log(10) cfu was 2.65+/-1.85, 3.30+/-0.85, 2.86+/-1.36, in BSS, cefazolin, PHMB group respectively. No differences in either clinical scores or bacterial counts were found between the PHMB and BSS groups. PHMB appears to be ineffective against S. aureus in this model of experimental keratitis.