Comparison of the efficacy of different treatment doses of intrastromal vancomycin in A model of methicillin-resistant staphylococcus aureus keratitis in rabbit eyes

In this study it has been aimed to compare the efficiencies of different treatment doses of corneal intrastromal vancomycin on keratitis treatment which is caused by Methicillin-resistant Staphylococcus aureus (MRSA) For this purpose, rabbits have been divided into four groups, there are six rabbits in each group, after 0,1 mL MRSA strains which consist of 103 CFU are administered into left 24 eye santral corneas via 30 gauge enjector. It had been waited for emerging of keratitis model for 24 hours. After it is seen that the keratitis model are emerged in all the four groups. It has been passed the second stage. It has been accepted six eyes in first group as control group and balanced salt solution administered into these eyes. Single dose of 0,5 mg/0,1 mL intrastromal vancomysin is administered into the left eye corneas in the second group. Single dose of 1 mg/0,1 mL intrastromal vancomysin is administered into the left eye corneas in the third group. Single dose of 2 mg /0,1 mL intrastromal vancomysin is administered into the left eye corneas in the fourth group. After these injecitons, it has been waited for twenty four hours and than none of these eyes are seen any possible complications. After following euthanasia that is last stage, the corneas have been sent to microbiology laboratuary by removing rabbit corneas with the help of vacuum trephine punch. The bacterial load is listed as follows from most to least; control group (7,13±1,27 log10 CFU/g), 2 mg/0,1 mL intrastromal vancomycin group (4,49±0.85 log10 CFU/g), 0,5mg/0,1 mL intrastromal vancomycin group (4,54±0.57 log10 CFU/g), 1 mg/0,1 mL intrastromal vancomycin group (4,21±0.83 log10 CFU/g). Every cornea has been evaluated also according to morphological in this study. While doing that, eight parameters (chemosis, conjunctival injection, iritis, fibrin, hypopyon, epithelial erosion, corneal infiltrate, corneal oedema) have been scored with the help of the clinical score system (0:absent 1:trace 2:mild 3:modarate 4:severe) by two different clinical observer (A.B. and Y.A.). While scoring these parameters, both morphological observation and biomicroscope have been used. For this purpose, the results of both twenty fourth (before treatment) and fourty eighth (after treatment) hours after keratitis modellings had been emerged have been evaluated and recorded These scores have been evaluated by comparing both three different treatment doses in each other and with the control group. vi The results of the morphlogical assessments of the corneas are as follows; as the total clinical scores of both before and after treatment are evaluated separately for the four groups; the total clinical score of the fourty eighth hour of the control group (without any treatment group) have increased significantly in contrast to the twenty fourth hour of the control group As the total clinical score which is after treatment is evaluated in the three different treatment groups by comparing with the total score which is before treatment, the results are as follows; 1) There were not found any significant result between 0,5 mg/0,1 mL intrastromal vancomycin treatment group with 1 mg/0,1 mL intrastromal vancomycin treatment group 2) The 48th hour total clinical score has increased in the 2 mg/0,1 mL intrastromal vancomycin treatment group significantly in contrast to the 24th hour total clinical score. However, it should not be forgotten that these results which are the 24th hour and 48th hour are early period results In addition to these, in order to examine safety of the three different treatment doses which are on the conjunctiva, cornea, iris and anterior chamber, we have evaluated separately the different eight parameters which are mentioned above among the three different treatment doses. The significant result is so that; the different two treatment doses such as 0,5 mg/0,1 mL, 1 mg/0,1 mL intrastromal vancomycin have not caused significantly 'iritis', 'fibrin in anterior chamber', 'corneal oedema', but on the other hand, 2 mg/0,1 mL intrastromal vancomycin has caused significantly 'iritis', 'fibrin in anterior chamber', 'corneal oedema' in contrast to the different two doses. At this point, we want to emphasize that it is already known about the side effects of the vancomycin active ingredient such as damage to corneal epithelial, endothelial cells and iritis, fibrin in the anterior chamber so on. Hence, it has been shown that 2 mg/0,1 mL intrastromal vancomycin has caused corneal side effects, althought the reducing of the bacterial load of 2 mg/0,1 mL intrastromal vancomycin is statistically significant. As a result, it has been proved that the three different treatment doses which are single dose of 0,5 mg/0,1 mL intrastromal vancomycin, single dose of 1 mg/0,1 mL intrastromal vancomycin and single dose of 2 mg/0,1 mL intrastromal vankomycin have been reduced the bacterial load significantly and have been had the therapeutic effect comparing to control vii keratitis group. However, as it is evaluated according to the possible side effects on the cornea, the two different treatment single doses such as 0,5 mg/0,1 mL intrastromal vancomycin and 1 mg/0,1 mL intrastromal vancomycin have been proved that these two treament doses are significantly much more safer than 2 mg/0,1 mL vancomycin. With the help of this study, we assume that the use of 0,5 mg/0,1 mL intrastromal vancomycin can be more appropriate for the following treatment models by providing be significantly same level of safety and efficiency with the much lower chemical drug ingredient in contrast to 1 mg/0,1 mL vancomycin. This study of the comparing of the efficiency of the different treatment doses of the corneal intrastromal vancomycin on the MRSA strains related with bacteriel keratitis treatment is the first experimentel study in the literatüre. The efficiency and the safety of the corneal intrastromal administering method with its current limitations are needed to be supported by further human studies.