Abstract
Abstract: :
Purpose: 0.02% Chlorhexidine has been evaluated clinically in the treatment of acanthamoebic keratitis. Chlorhexidine has also proven efficacious in previous in vitro studies against Staphylococcus aureus (MIC <0.004%) and Pseudomonas aeruginosa (MIC <0.004%) (ARVO 1573–B583, 2002 ). The purpose of this study was to evaluate the in vitro efficacy of chlorhexidine, as compared to vancomycin, against a broad spectrum of other infectious agents known to cause bacterial keratitis. Methods: The minimal inhibitory concentration (MIC) of chlorhexidine was determined using the macrodilution tube method for various organisms. The MIC for vancomycin was determined using the E–test. The organisms studied were methicillin resistant Staphylococus aureus, Streptococcus orales ( a viridans streptococcus), Streptococcus Pneumonia, Bacillus cereus, Serratia marcescens, and Klebsiella pneumonia. Results: The MIC’s for chlorhexidine are as follows: Streptococcus pneumonia: 0.05%, Staphylococcus aureus: 0.025%, Streptococcus orales: 0.0125%, Bacillus cereus: 0.0004%, Klebsiella pneumonia: >0.1%, Serratia marcescens: 0.1%. The MIC's for vancomycin are as follows: Streptococcus pneumonia: 0.5ug/ml, Staphylococcus aureus: 1.5ug/ml, Streptococcus orales: 1.0ug/ml, Bacillus cereus: 1.5ug/ml, Klebsiella pneumonia: >256ug/ml, Serratia marcescens: >256ug/ml. Conclusions: Chlorhexidine has previously been shown to be effective against Acanthomoeba, Pseudomonas, and Staphylococcus aureus. In this study we determined the MIC for Streptococcus viridans , and to our knowledge first time MIC’s for methicillin–resistant Staphlycoccus aureus, Streptococcus pneumoniae, Bacillus cereus, Klebsiella pneumonia, and Serratia marcescens. We conclude that the 0.02% solution of chlorhexidine used clinically today would be effective only for Streptococcus orales and Bacillus cereus, according to our vitro studies. This can be compared to vancomycin which was extremely efficacious against all gram positive organsisms tested.
Keywords: antibiotics/antifungals/antiparasitics • bacterial disease • keratitis