Sequence analysis of a RAPD band differentiating highandlowvirulence Staphylococcus aureus strains from rabbits K.Hermans * ,P.DeHerdt,M.Baele,L.A.Devriese,F.Haesebrouck Department of Pathology, Bacteriology and Poultry diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium Received17October2000;receivedinrevisedform27February2001;accepted20March2001 Abstract RAPD typing revealed the presence of a nucleotide band in typical high virulence rabbit Staphylococcus aureus strains which was absent in low virulence strains and in an atypical high virulence strain. The nucleotide sequence of this band was determined. Primers within this sequence were developed and PCR products of eight typical high virulence, one atypical high virulenceandninelowvirulencerabbit S. aureus strainsweresequenced.Alllowvirulencestrains andtheatypicalhighvirulencestrainrevealedaconstantdifferencewiththetypicalhighvirulence strains for nucleotide 377 of the 1055bp sequence. The eight typical high virulence strains possessedaguaninebaseonthissite,whiletheotherstrainstestedshowedanadeninebase.These ®ndings support the hypothesis on the clonal origin of typical high virulence rabbit S. aureus strains.Aftercomparisonwithdatabases,twoopenreadingframesORF)wereidenti®edwithinthe sequence, which appeared to encode two structural ribosomal proteins. The single nucleotide mutation does not affect the amino acid sequence of the protein it encodes for. # 2001 Elsevier ScienceB.V.Allrightsreserved. Keywords: Staphylococcus aureus;Rabbit;RAPD;Virulence;Mutation 1. Introduction In rabbits, problems arise when Staphylococcus aureus infects small dermal lesions andinvadesubcutaneoustissueOkermanetal.,1984).All S. aureus infectionsofrabbits have a similar clinical appearance, with lesions of pododermatitis, subcutaneous VeterinaryMicrobiology822001)61±67 * Correspondingauthor.Tel.: 32-9-264-74-31; fax: 32-9-264-74-94. E-mail address: katleen.hermans@rug.ac.be K. Hermans). 0378-1135/01/$ ± see front matter # 2001ElsevierScienceB.V.Allrightsreserved. PII:S0378-113501)00369-8