Streptococcus sanguis Survival in K-Sol: Comparison of Gentamicin and the Fluoroquinolone Antibiotics

Viridans streptococci are poorly covered by gentamicin sulfate in corneal storage medium. To evaluate possible antibiotic alternatives among the newer broad-spectrum fluoroquinolone antibiotics, we compared the survival of the viridans representative Streptococcus sanguis in K-Sol with gentamicin sulfate (100 mg/L), norfloxacin (250 mg/L), ciprofloxacin lactate (250 mg/L), ofloxacin (250 mg/L), or no antibiotic. At 23°C, K-Sol with gentamicin produced a 2-log kill by 80 minutes. By comparison, only one of the others (norfloxacin) had achieved a 2-log kill by 4 hours. At 4°C, all antibiotics differed little from the control, and none was superior to gentamicin.