Nebcin0 in the treatment of experimental Pseudomonas keratitis

Pseudomonas aeruginosa is one of the most virulent and frequently encountered infectious agents affecting the cornea (Allen and Mangiaracine, 1964). Unhappily, its destructive effect on ocular tissues cannot always be prevented by the antibiotics currently available. The best anti-Pseudmonas drugs are colistin, polymyxin B, and gentamicin (Burns, 1969; Gordon, 1970), but Pseudomonas strain-resistance to gentamicin is increasing (Morel, Freymouth, and Moncrocg, 1972), and all three drugs can produce unfortunate side-effects, such as conjunctival scarring, when injected subconjunctivally. Nebramycin is an aminoglycoside complex that was isolated from a culture of Streptomyces tenebrarius (Higgens and Kastner, 1967). In suitable media, this species produces a group of eight chemically-related antibiotic factors, of which tobramycin (Factor 6) has been found to have the highest specific effect on Ps. aeruginosa (Wick and Welles, 1967). Its level of nephrotoxicity is slightly less than that of gentamicin, but it is just as ototoxic as gentamicin and kanamycin (Wick and Welles, 1967; Eli Lilly & Co., 1974); and there is evidence that it is active in vitro and in vivo against some gentamicin-resistant strains (Smolin, Okumoto, and Wilson, I974). When tobramycin is injected subconjunctivally in concentrations bactericidal to Ps. aeruginosa (Purnell and McPherson, 1974), it rapidly penetrates the eye. And since it is now available as an injectable solution (Nebcin@*), we decided to test both its efficacy and its toxicity when used to treat Pseudomonas-infected rabbit eyes, and to compare these effects with those of gentamicin.