title: Septic pleuritis and abdominal abscess formation caused by Rhodococcus equi in a foal.
abstract: A 3-month-old female Arabian horse was evaluated because of fever, respiratory distress, lethargy, and decreased appetite of 5 days' duration. Pleural effusion was diagnosed on the basis of ultrasonographic and radiographic examinations. Cytologic examination of pleural fluid collected via thoracocentesis revealed septic inflammation; bacteriologic culture of a sample of that fluid yielded Rhodococcus equi. A large intra-abdominal mass adjacent to the body wall was identified ultrasonographically. A specimen of the mass was collected via aspiration; the specimen was identified cytologically as purulent exudate that contained large numbers of rod-shaped bacteria, which confirmed abdominal abscess formation. Bacteriologic culture of a sample of the exudate also yielded R. equi. The foal was treated with azithromycin (10 mg/kg [4.5 mg/lb], PO, q 24 h for 5 days then q 48 h) and rifampin (5 mg/kg [2.3 mg/lb], PO, q 12 h) for 8 weeks and metronidazole (15 mg/kg [6.8 mg/lb], PO, q 8 h) for 3 weeks. Clinically, the foal responded to antimicrobial treatment within 2 weeks. At 8 weeks after the initial evaluation, ultrasonographic examination of the foal revealed resolution of the pleural effusion and abdominal abscess. In foals, R. equi infection typically results in pyogranulomatous pneumonia, and pleural effusion is an uncommon clinical sign. The combination of azithromycin and rifampin appears to be an effective treatment for R. equi infection in foals.
authors.affiliation: Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Valdes
authors.forename: Jill R
authors.initials: JR
authors.lastname: Johnson
mesh_terms: D018784:Abdominal Abscess / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000662:veterinary*; D000193:Actinomycetales Infections / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000662:veterinary*; D000818:Animals; D000831:Animals, Newborn; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D017963:Azithromycin / Q000627:therapeutic use; D024881:Drug Resistance, Bacterial; D005260:Female; D006734:Horse Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000382:microbiology; D006736:Horses; D018410:Pneumonia, Bacterial / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000662:veterinary*; D016929:Rhodococcus equi / Q000187:drug effects / Q000302:isolation & purification; D012293:Rifampin / Q000627:therapeutic use; D016896:Treatment Outcome; D014463:Ultrasonography
chemical_list: D000900:Anti-Bacterial Agents; D017963:Azithromycin; D012293:Rifampin