Polymyxin-coagulase-mannitol-agar. I. A selective isolation medium for coagulase-positive Staphylococci.
A selective, differential plating medium was developed for the isolation and identification of coagulase-positive and mannitol-fermenting staphylococci. Coagulase produced by growing Staphylococcus aureus caused an opaque zone of fibrin to form around each colony. Several strains of S. aureus produced a visible coagulase reaction by 8 hr, and all strains gave a positive reaction before 12 hr. Mannitol fermentation was usually observed between 12 and 36 hr. Rabbit serum was filtered through Sephadex G-100 to obtain plasmin- and plasminogen-free coagulase-reacting factor (CRF). False-negative reactions, caused by staphylokinase and staphylococcal Müller factor action on plasminogen, were eliminated when this CRF was used. False-positive reactions by lipolytic, coagulase-negative staphylococci were reduced, since gel filtration removed the serum lipoprotein which served as a primary source of opacity. The addition of 75 mug of polymyxin B per ml selectively retarded the growth of S. epidermidis and minimized false-positive reactions caused by citrate-utilizing gram-negative rods. The preparation, characteristics, and use of the medium are presented.
D000362:Agar; D000818:Animals; D001431:Bacteriological Techniques; D003030:Coagulase / Q000096:biosynthesis; D003470:Culture Media; D005189:False Positive Reactions; D005341:Fibrinolysin / Q000032:analysis; D008353:Mannitol; D010958:Plasminogen / Q000032:analysis; D011113:Polymyxins; D011817:Rabbits; D013210:Staphylococcus / Q000302:isolation & purification* / Q000378:metabolism
D003030:Coagulase; D003470:Culture Media; D011113:Polymyxins; D008353:Mannitol; D010958:Plasminogen; D000362:Agar; D005341:Fibrinolysin