Topical bactrim versus trimethoprim and sulfonamide against nocardia keratitis.
OBJECTIVE
The conventional treatment of Nocardia keratitis is with topical sulfonamides. Recently, topical trimethoprim and sulfamethoxazole (Bactrim) has been suggested as treatment. This study compares the in vitro efficacy against Nocardia asteroides of Bactrim and various ratios of trimethoprim and a sulfonamide.


METHODS
Antibiotic disks were soaked with various ratios of trimethoprim and sulfacetamide sodium. They contained trimethoprim alone, sulfacetamide sodium alone, and both trimethoprim and sulfacetamide sodium at ratios of 1:40, 1:20, and 1:5. Disks containing Bactrim were also prepared. Each disk was placed on blood agar plates streaked with N. asteroides. The plates were incubated at 37 degrees C for 72 hours and then examined.


RESULTS
Trimethoprim alone showed minimal effect. Sulfacetamide sodium alone had a clearance zone of 12 mm. The plates of trimethoprim and sulfacetamide sodium at ratios of 1:40, 1:20, and 1:5 had clearance zones of 14 mm, 17 mm, and 27 mm, respectively. Bactrim had a clearance zone of 70 mm.


CONCLUSIONS
Trimethoprim or sulfacetamide sodium alone is not as effective as both drugs together. As the ratio of the two drugs was changed, potency differed against Nocardia organisms. Bactrim was the most effective antibiotic against Nocardia organisms. It should be the recommended agent for the treatment of Nocardia keratitis.
Department of Ophthalmology, Westchester Medical Center, New York Medical College, Valhalla 10595, USA.
L H
LH
Lee
G W
GW
Zaidman
K
K
Van Horn
D000287:Administration, Topical; D000328:Adult; D000891:Anti-Infective Agents, Local / Q000627:therapeutic use*; D003315:Cornea / Q000382:microbiology; D015818:Eye Infections, Bacterial / Q000188:drug therapy* / Q000382:microbiology; D006801:Humans; D007634:Keratitis / Q000188:drug therapy* / Q000382:microbiology; D008297:Male; D008826:Microbial Sensitivity Tests; D009617:Nocardia Infections / Q000188:drug therapy* / Q000382:microbiology; D009616:Nocardia asteroides / Q000302:isolation & purification*; D009883:Ophthalmic Solutions; D013409:Sulfacetamide / Q000627:therapeutic use*; D014295:Trimethoprim / Q000627:therapeutic use*; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000627:therapeutic use*
D000891:Anti-Infective Agents, Local; D009883:Ophthalmic Solutions; D013409:Sulfacetamide; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D014295:Trimethoprim