Comparative characterization and biotyping of Staphylococcus aureus isolates from human and bovine sources.

One Hundred and ten alpha and/or delta-haemolytic isolates (collection 1), 50 beta haemolytic isolates (collection 2) from bovine mastitis, and 100 previously phage-typed alpha- and delta-haemolytic isolates (human collection) og () were tested and biotyped according to the scheme of (1971). Among collection 1 isolates, 85 (77.3 %) belonged to the human biotype A (human source). Twenty two (20 %) designated as non-allotted strains, possessed characteristics of both animal and human sources. The remaining 3 isolates (2.7 %) in this collection belonged to biotype C (animal source). All collection 2 isolates which were used as control strains for animal sources, belonged to biotype C. The human collection that contained 100 phage-typed haemolytic isolates (representing all human phage groups) were used as a control for the human source. Irrespective of their phage group, these strains predominantly produced alpha and/or delta haemolysins and belonged to the human biotype A. This study also recommended the use of a combined plasma crystal violet agar medium for the presumptive identification of biotypes.