Staphylococcus
Gram + cocci
In clumps
Staphylococci


3 major species: S.aureus,
S.epidermidis, and S.saprophyticus)
Infections are primarily associated with
pathogenic strains of S.aureus


Many virulence factors
Comparison of the 3 major species
(Table 64.1 p416)
All three species appear similar by Gram stain.
S. aureus
S. saprophyticus
S. epidermidis
Media Used to Distinguish
Staphylococcal Species

MSA
S. aureus ferments manitol causing the media to turn
yellow
S. epidermidis and S. saprophyticus do not
Therefore, the media remains red

DNAse Test:



Confirms S.aureus
DNAse (an enzyme that degrades DNA)
On medium containing DNA and methyl
green, a positive result is a clearing around
the bacterial growth
S. aureus
S. saprophyticus
Gram+ cocci in clumps
Manitol fermentation (MSA media)
DNAse+
S. epidermidis
Gram+ cocci in clumps
No Manitol fermentation (MSA media)
DNAse-
Procedure:


Divide a MSA plate into 3 sectors;
inoculate (single line inoculation) the
plate with S.aureus, S.saprophyticus
and S.epidermidis
Divide a DNAse plate into 3 sectors;
inoculate the plate with the 3 organisms
listed above as described above

MSA and DNAse Plates
S. aureus
S. saprophyticus
S. epidermidis
Novobiocin Sensitivity Test
S. aureus and
S. epidermidis


Used to distinguish S.saprophyticus
from S.epidermidis and S. aureus
Identifies the novobiocin-resistant
S.saprophyticus
S. saprophyticus
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S. saprophyticus
S. saprophyticus
S. epidermidis
S. epidermidis
Procedure:


Divide a Mueller-Hinton Agar Plate into two
sectors
Inoculate (create a small “lawn” of bacteria in
each sector) with S.epidermidis and
S.saprophyticus


Place a novobiocin disk in the center of each
“lawn”
Invert plate; incubate
Catalase Test



Determines the ability of microbes to
degrade hydrogen peroxide (H2O2) by
producing the enzyme catalase
H2O2 is produced during aerobic
respiration; must be degraded
catalase
2 H2O2
2 H2O + O2
Catalase Test Results


Upon addition of H2O2 , Catalase
positive organisms release oxygen gas
(seen as bubbles)
Present in Staphylococcus
Coagulase Test
Coagulase: an enzyme that converts fibrinogen
to fibrin in plasma to form clots.
S. aureus express coagulase.
S. epidermidis and
S. saprophyticus do not.
S. aureus
S. saprophyticus
S. epidermidis
Gram+ cocci in clumps
Manitol fermentation (MSA media)
DNAse+
Novobiocin sensitive
Coagulase+
Catalase+
Gram+ cocci in clumps
No Manitol fermentation (MSA media)
DNAseNovobiocin resistant
CoagulaseCatalase+
Gram+ cocci in clumps
No Manitol fermentation (MSA)
DNAseNovobiocin sensitive (Zone of inhibition)
CoagulaseCatalase+
Catalase
+
+
+
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