Location: Warmwater Aquaculture Research UnitTitle: Preparation of ormetoprim-sulfadimethoxine-medicated discs for disc diffusion assay Author
Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2010
Publication Date: 2/2/2011
Publication URL: http://handle.nal.usda.gov/10113/55538
Citation: Gaunt, P.S., Gao, D.X., Wills, R. 2011. Preparation of ormetoprim-sulfadimethoxine-medicated discs for disc diffusion assay. North American Journal of Aquaculture. 73:17-20. Interpretive Summary: The manuscript described the methodology of preparing Romet ( a potentiated sulfa drug – ormetoprim-sulfadimethoxine) antibiotic discs for use in disc diffusion assays. This was necessitated by the discontinued production of commercial discs. The laboratory-prepared discs were found to be comparable based on testing with 23 field isolates of Edwardsiella ictaluri, the bacteria that is the etiological agent of enteric septicemia of catfish. Thus the laboratory-prepared discs were deemed to be acceptable replacements for the commercially produced discs no longer in production.
Technical Abstract: Romet ( a blend of ormetoprim and sulfadimethoxine) is a type A medicated article for the manufacture of medicated feed in the catfish industry. Recently, the commercial manufacture of ormetoprim-sulfadimethoxine susceptibility discs was discontinued. Ormetoprim-sulfadimethoxine discs were prepared at the Mississippi State University College of Veterinary Medicine Aquatic Diagnostic Laboratory according to Clinical and Laboratory Standards Institute guidelines. The performance of the laboratory-prepared discs was compared with that of commercially prepared discs in disc diffusion assays with 23 field isolates of Edwardsiella ictaluri. The a priori limits of agreement for the laboratory-prepared ormetoprim-sulfadimethoxine discs were + 5mm of the zones for the commercial discs. The resulting zones of inhibition ranged from 33 to 50 mm and from 35 to 52 mm for the laboratory-prepared and commercially prepared discs respectively. The data comparing the two sets of discs were analyzed to determine the level of agreement. The analysis demonstrated that the laboratory-prepared discs produced slightly smaller zone of inhibition than the commercially prepared ones. The observed limits of agreement were within the a priori established limits of agreement, indicating that the laboratory-prepared ormetoprim-sulfadimethoxine discs were acceptable replacements for the commercially prepared discs.