Background:
Different antiseptic drugs are available for ocular surface use but are rarely used in clinical practice, except for preparing the ocular surface prior to surgical procedures. However, these antiseptics may also be suitable to be used in prophylaxis and treatment of infections of the ocular surface. Relevant agents include N-acetylcysteine (NAC), polyhexanide (PHMB), hypochlorous acid(HOCI) and povidione-iodine (PVP-I).

Objective:
Given that topical administration to the ocular surface means that active agents are quickly diluted and removed with the tear film, it is essential to view their anti-microbial activity in relation to the actual contact time.
This study aims to investigate the minimal necessary exposure time (i.e. killing-time) required for NAC, PHMB, HOCI and PVP-I to achieve their respective antimicrobial effect. Investigations are necessary before a clinical trial can be designed to test their efficacy in prophylaxis and treatment.

Methods and procedures:
Isolates of Staphylococcus pseudintermedius, Pseudomonas aeruginosa and Streptococcus canis - some of the most common corneal pathogens of infectious keratitis in dogs and cats - will be added to different concentrations of the testing agents. The suspension will be
removed after varying time points of exposure and added to agar plates, which will then be incubated at 37°. After 24 hours, the plates will be evaluated for microbial growth.

Expected outcome / results:
The results will provide minimal necessary exposure times at certain concentrations and give insight into the required contact time when using these agents in clinical patients.

Siqnificance:
Antibiotic resistance poses a global medical emergency, also affecting ophthalmic patients suffering from infectious keratitis with up to 38% of multi-resistant organisms reported, to enhance the existing treatment protocols and offer alternative options to traditional antibiotic therapy, there is a strong demand for alternative approaches in both human and veterinary medicine.