Transfer of the virulence-associated protein a-bearing plasmid between field strains of virulent and avirulent Rhodococcus equi.

BACKGROUND: Virulent and avirulent isolates of Rhodococcus equi coexist in equine feces and the environment and are a source of infection for foals. The extent to which plasmid transfer occurs among field strains is ill-defined and this information is important for understanding the epidemiology of R. equi infections of foals. OBJECTIVES: To estimate the frequency of transfer of the virulence plasmid between virulent and avirulent strains of R. equi derived from foals and their environment. ANIMALS: None. METHODS: In vitro study; 5 rifampin-susceptible, virulent R. equi isolates obtained from clinically affected foals or air samples from a farm with a history of recurrent R. equi foal pneumonia were each mixed with 5 rifampin-resistant, avirulent isolates derived from soil samples, using solid medium, at a ratio of 10 donor cells (virulent) per recipient cell. Presumed transconjugates were detected by plating on media with rifampin and colony immunoblotting to detect the presence of the virulence-associated protein A. RESULTS: Three presumed transconjugates were detected among 2,037 recipient colonies, indicating an overall estimated transfer frequency of 0.15% (95% CI, 0.03­0.43%). All 3 transconjugates were associated with a single donor and 2 recipient strains. Genotyping and multiplex PCR of presumed transconjugates demonstrated transfer of the virulence-associated protein A-bearing plasmid between virulent and avirulent R. equi. CONCLUSIONS AND CLINICAL IMPORTANCE: Transfer of the virulence plasmid occurs with relatively high frequency. These findings could impact strategies to control or prevent R. equi through environmental management.

Concurrent ivermectin and Solanum spp. toxicosis in a herd of horses.

BACKGROUND: Representatives from a herd of horses with acute onset of neurologic signs after administration of ivermectin presented for evaluation and treatment. OBJECTIVES: Describe clinical signs of horses intoxicated by ingestion of Solanum sp. and administered ivermectin. ANIMALS: Six of 11 affected unrelated horses presented for evaluation and treatment. The remaining 5 affected horses were treated at the farm. Four additional horses, housed separately, were unaffected. METHODS: Case series is presented. Serum ivermectin concentrations were evaluated in the 6 hospitalized horses. The remnants of the tubes of ivermectin paste were analyzed for ivermectin concentration. The hay fed to the affected horses was analyzed for the presence of toxic plants. RESULTS: Serum ivermectin concentrations were higher than expected, given the dosage of ivermectin administered. The ivermectin concentration remaining in the administration tubes did not exceed specifications. The hay was heavily contaminated by 2 Solanum species. All horses returned to normal neurologic function with supportive care. CONCLUSIONS AND CLINICAL IMPORTANCE: Horses might exhibit signs of ivermectin toxicity after appropriate dosing of the drug if they concurrently consume toxic plants of the Solanum family.

Hospitals' response to the buckle-up baby legislation in Ontario.

Drivers in Ontario are legally responsible to ensure that infants and toddlers are restrained in a child safety seat or by a lap belt. In 1982 the minister of health sent a memorandum to all medical officers of health and the administrators and medical directors of all public hospitals in Ontario, urging them to encourage and assist parents in protecting their newborn children with safety seats. In 1983 the Toronto General Hospital established the Cooperative Hospital Infant Restraint Program (CHIRP) to study the feasibility of a "loaner" program for hospitals in metropolitan Toronto. The authors describe CHIRP and its objectives. They also report the results of a questionnaire they sent in 1984 to all Ontario hospitals that had a newborn or pediatric service to assess their response to the minister's memorandum.