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Staphylococci Clinical Microbiology Review 158


ORGANISM PATHOGENICITY GRAM STAIN COLONIES ON SBA KEY CHARACTERISTICS OTHER

Staphylococcusspp

S. aureus

Coagulase-negative
staphylococci (CNS)

Normal flora of skin,
mouth, pharynx,
vagina, urethra, GI
tract. Facultative
anaerobe. Grows on
most nonselective
media. Salt tolerant.

10%–60% are carriers.
Spread by direct
contact. 85%–90%
resistant to penicillin.

Normal on skin &
mucous membranes.
Often contaminant.
Usually only speciated
if from normally sterile
site. 50%–80% are
S. epidermidis.

GPC, usually in
clusters

GPC, usually in
clusters

GPC, usually in
clusters

1–3 mm, round,
smooth, convex,
glistening, opaque,
entire edge, buty-
rous (butter-like).

Most are beta
hemolytic (small
zone). May be
golden.

White, usually
nonhemolytic.

See specific organ-
isms below

Causes suppurative
cutaneous infec-
tions, toxic shock
syndrome, food
poisoning

Opportunistic
pathogen. Common
cause of hospital-
acquired UTI

Catalase pos.
Fermentative.
Microdase (modified
oxidase) neg. Resistant
to bacitracin. Suscepti-
ble to furazolidone &
lysostaphin.

Coagulase pos.
Ferments mannitol
(yellow colonies on
mannitol salt agar).
Usually DNase & ther-
monuclease pos.

Coagulase neg. Grow
on mannitol salt agar
but don’t ferment
mannitol. Sensitive to
novobiocin.

continued...
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