RESTRICTION-ENDONUCLEASE ANALYSIS AND RIBOTYPING DIFFERENTIATE PASTEURELLA-HAEMOLYTICA SEROTYPE-A1 ISOLATES FROM CATTLE WITHIN A FEEDLOT

Pasteurella haemolytica serotype A1 isolates were collected from cattl e within a feedlot during an outbreak of bovine respiratory disease. G enetic heterogeneity among the isolates was examined by restriction en donuclease analysis (REA), ribotyping, and analysis of plasmid content . The susceptibilities of isolates to several antibiotics were also ex amined. Five different REA patterns and three different ribotypes were observed among the isolates. Fifty percent of the isolates had an ide ntical REA type, ribotype, and plasmid profile. Examination of the pla smid content of the isolates revealed that most (73%) carry a single p lasmid which encodes beta-lactamase, 13.5% carry two plasmids, and 13. 5% carry no plasmid. The data reveal the presence of genetic differenc es among isolates of P. haemolytica Al, associated with shipping fever pneumonia within a closed feedlot, and suggest that a combination of REA, ribotyping, plasmid analysis, and antibiotic susceptibility deter mination will be useful in analyzing the molecular epidemiology of thi s disease.