Atlas of Medical Bacteriology

1-GRAM POSITIVE BACTERIA
1-1-Staphyllococcus spp.
The staphylococci are gram-positive spherical cells, non-sporing, non-motile, usually non-capsulate, true facultatively anaerobic organisms. (1micrometer in diameter) usually arranged in grapelike irregular clusters. They grow readily on many types of media and are active metabolically, fermenting carbohydrates and producing pigments that vary from white to deep yellow. Colonies on solid media are round, smooth, raised, and glistening S. aureus usually forms gray to deep golden yellow colonies. S. epidermidis colonies usually are gray to white on primary isolation; many colonies develop pigment only upon prolonged incubation. No pigment is produced anaerobically or in broth. Various degrees of hemolysis are produced by S aureus and occasionally by other species. Staphylococcus saprophyticus
is a frequent cause of cystitis in women, probably related to its occurrence as part of normal vaginal flora. S. saprophyticus can be distinguished from S. epidermidis and most other coagulase-negative staphylococci by its natural resistance to novobiocin . [Note: Urinary coagulase-negative staphylococcus is often presumed to be S. saprophyticus; novobiocin resistance can be used for confirmation.].