1. Staphylococcus
Gram + cocci
In clumps

2. 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)

3. All three species appear similar by Gram stain.
S. aureus
S. saprophyticus
S. epidermidis

4. Media Used to Distinguish Staphylococcal Species
MSA
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 ferments manitol causing the media to turn yellow
S. epidermidis and S. saprophyticus do not
Therefore, the media remains red

5. S. aureus
Gram+ cocci in clumps
Manitol fermentation (MSA media)
DNAse+
S. saprophyticus
S. epidermidis
Gram+ cocci in clumps
No Manitol fermentation (MSA media)
DNAse-

6. 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

7. MSA and DNAse Plates
S. saprophyticus
S. epidermidis
S. aureus

8. 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. epidermidis
S. saprophyticus
S. epidermidis

9. 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

10. 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 H2O H2O + O2

11. Catalase Test Results
Upon addition of H2O2 , Catalase positive organisms release oxygen gas (seen as bubbles)
Present in Staphylococcus

12. 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.

13. S. aureus
Gram+ cocci in clumps
Manitol fermentation (MSA media)
DNAse+
Novobiocin sensitive
Coagulase+
Catalase+
S. saprophyticus
Gram+ cocci in clumps
No Manitol fermentation (MSA media)
DNAse-
Novobiocin resistant
Coagulase-
Catalase+
S. epidermidis
Gram+ cocci in clumps
No Manitol fermentation (MSA)
DNAse-
Novobiocin sensitive (Zone of inhibition)
Coagulase-
Catalase+

14. Catalase
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