In vitro antimicrobial activity of diacerein on 76 gram-positive cocci isolates from bacterial keratitis patients and an in vivo study of diacerein eye drops on Staphylococcus aureus keratitis in mice

Bacterial keratitis is an aggressive infectious corneal disease. With the continuing rise in antibiotic resistance and a decline in the discovery of new antibiotics, new antimicrobial drugs are now required. In the present study, we determined the antibacterial activity of diacerein, an anti-inflammatory drug, against 76 Gram-positive cocci isolated from bacterial keratitis patients in vitro and anti- Staphylococcus aureus activity in mouse bacterial keratitis model in vivo. The minimum inhibitory concentrations (MICs) of diacerein were tested using the broth microdilution method in vitro. A BALB/c Staphylococcus aureus keratitis animal model was selected and the corneal clinical observation, viable bacteria and Hematoxylin-eosin and Gram staining of infected corneas were measured to evaluate antibacterial efficacy of diacerein eye drops in vivo. An in vivo eye irritation study was carried out by a modified Draize test in rabbits. Our in vitro results showed that diacerein possesses satisfactory antibacterial activity against the majority of Gram-positive cocci (60/76), including all 57 tested Staphylococcus and 3 Enterococcus . The in vivo experiment showed that diacerein eye drops reduced bacterial load and improved ocular clinical scores after topical administration of diacerein drops on infected corneas. The ocular irritation test revealed that diacerein eye drop had excellent ocular tolerance. These results indicated that diacerein possesses in vivo anti- Staphylococcus aureus activity. We suggest that diacerein is a possible topically administered drug for Staphylococcus aureus -infected patients, especially those with ocular surface inflammatory disorders.