Antibacterial effectiveness of commercial eyedrop preservatives

K. B. Kirn*, I. Barequet, T. K. Chan, G. J. Osterhout, T. P. O'Brien

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Purpose: To test the sustained and immediate antibacterial effectiveness of several preservative systems in commonly used multiple-dose eyedrops. Methods: Standardized suspensions of each of 4 test organisms (P. aeruginosa, S. marcesens, S. aureus, S. epidermidis) were added daily to commercial solutions containing thimerosal (Fluoracaine), benzalkonium chloride (Tropicamide 1% and Alcaine) and polyaminopropyl biguanide (ReNu Multipurpose CL solution). Serial samples were obtained and quantitative bacteriology was performed weekly. Preservative systems were also acutely challenged with high bacterial concentration ( 1 x 108 or Ix 1018 cfu/ml ) and sampled for immediate plating. Results; Serial cultures failed to recover any growth of test organisms for up to 8 weeks of testing. Benzalkonium chloride was observed to have a stronger immediate antibacterial effect with higher inoculum concentrations as compared with the other two preservatives. Conclusion: Current commercial preservative systems maintain antimicrobial effectiveness for up to 8 weeks, suggesting guidelines for safe, planned replacement in clinical settings.

Original languageEnglish
Pages (from-to)S520
JournalInvestigative Ophthalmology and Visual Science
Issue number4
StatePublished - 1997
Externally publishedYes


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