title: Clinical efficacy of trimethoprim/sulfadiazine and procaine penicillin G in a Streptococcus equi subsp. zooepidemicus infection model in ponies.
abstract: Tissue chambers, implanted subcutaneously on both sides of the neck in eight ponies, were inoculated with Streptococcus equi subsp. zooepidemicus in order to compare the clinical efficacy of trimethoprim/sulfadiazine (TMP/SDZ) and penicillin G treatment in a purulent infection. The TMP/SDZ treatment consisted of one intravenous (i.v.) injection of 5 mg/kg TMP and 25 mg/kg SDZ and the same dose of TMP/SDZ per os (p.o.), both given 20 h after inoculation. The oral dose was then repeated every 12 h for 21 days. The penicillin treatment consisted of one i.v. injection of 20 000 IU/kg sodium penicillin G and intramuscular (i.m.) injection of 20 000 IU/kg procaine penicillin G, both given 20 h after infection. The i.m. dose was then repeated every 24 h for 21 days. Eight ponies, each with two tissue chambers, were used in a cross over design; in the first experiment the left tissue chamber (TC) was infected and in the second experiment the right. TMP/SDZ treatment resulted in a limited reduction of viable bacteria in the TC but did not eliminate the infection, resulting in abscessation in 10-42 days in all eight ponies. However, penicillin treatment eliminated the streptococci in seven of eight ponies, and only one pony suffered abscessation on day 10. This constitutes a significantly better efficacy of the penicillin treatment in this model. The most probable cause of the failure of TMP/SDZ to eliminate the streptococci is inhibition of the action of TMP/SDZ in the purulent TCF. Therefore, TMP/SDZ should not be used to treat purulent infections in secluded sites in horses.
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands. j.m.ensink@vet.uu.nl
authors.forename: J M
authors.initials: JM
authors.lastname: Ensink
authors.forename: J A H
authors.initials: JA
authors.lastname: Smit
authors.forename: E
authors.initials: E
authors.lastname: van Duijkeren
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D004338:Drug Combinations; D004359:Drug Therapy, Combination; D005493:Folic Acid Antagonists / Q000008:administration & dosage*; D006734:Horse Diseases / Q000188:drug therapy* / Q000382:microbiology; D006736:Horses; D007273:Injections, Intramuscular; D007275:Injections, Intravenous; D008297:Male; D010402:Penicillin G Procaine / Q000008:administration & dosage*; D010406:Penicillins / Q000008:administration & dosage*; D013290:Streptococcal Infections / Q000188:drug therapy / Q000662:veterinary*; D018502:Streptococcus equi / Q000187:drug effects / Q000472:pathogenicity*; D013419:Sulfamethizole / Q000008:administration & dosage*; D016896:Treatment Outcome; D014295:Trimethoprim / Q000008:administration & dosage*; D000096926:Benzenesulfonamides
chemical_list: D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D005493:Folic Acid Antagonists; D010402:Penicillin G Procaine; D010406:Penicillins; D013419:Sulfamethizole; D014295:Trimethoprim; C029078:trimethoprim sulfamethizole; D000096926:Benzenesulfonamides