We investigated cefoperazone, a new third generation cephalosporin, for its possible use against bacterial eye infections. One hundred eighty strains of bacterial isolates of ocular significance were subjected to in vitro testing. Excellent results were noted, with only two species, Streptococcus faecalis and Acinetobacter anitratus, showing resistance. Minimum inhibitory concentration determinations were done on a few strains of Streptococcus aureus. All strains of S. pneumoniae and S. viridans were highly sensitive. S. aureus strains were moderately sensitive. Four strains of Pseudomonas aeruginosa were tested in vitro for synergy with a combination of cefoperazone and tobramycin using a two-dimensional checkerboard titration procedure. Two strains showed synergy and two were equivocal. An in vivo treatment study was done on 28 rabbits with a pseudomonas ulcerative keratitis. The animals were treated with cefoperazone alone, tobramycin alone, or a combination of the two drugs. Control rabbits were treated with saline. When the corneas were excised and cultured, the combined therapy resulted in fewer colonies than when cefoperazone or tobramycin were used alone; the differences were not significant for tobramycin, although they were significant for cefoperazone. Clinical evaluation showed that the combined therapy was significantly more effective than either antibiotic used alone.
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