Staphylococcus sp.

(General Characteristics)

1) Gram positive, clustered, cocci.

2) Aerobes and facultative anaerobes.

3) Catalase: Positive.

4) Modified Oxidase: Negative

5) OF Glucose: Fermenter

6) Lysostaphin: S (200 ug/ml)

7) Produces acid (aerobically) from Glycerol in presence of Erythromycin. (0.4 ug/ml)

S. Aureus 

1) Colony Morphology: Medium, yellow/white, circular, smooth, moist, colonies. Most strains are Beta hemolytic.

2) Gram Stain: G+ cocci in clusters

2) Catalase: +

3) Coagulase: +

4) Ferments mannitol.

5) DNase, TNase, Phosphotase: +

6) Tellurite reduction: +

7) Lysostaphin: S

8) Novobiocin: S

 S. Epidermidis

1) Colony Morphology: Small to medium, grayish, white, circular, smooth, gamma hemolytic, sometimes sticky colonies.

2) Gram stain: G+ cocci in clusters.

3) Catalase: +

4) Coagulase: -

5) PYR broth: -

6) Novobiocin: S

7) Phosphatase: +

8) Mannitol Fermentation: -

S. Saprophyticus

1) Colony morphology: Medium to large, smooth, opaque, butyrous, usually white, occasionally yellow/orange, gamma colonies.

2) Gram stain: G+ cocci in clusters, tend to appear as tetrads.

3) Catalase: +

4) Coagulase: -

5) PYR Broth: -

6) Novobiocin: R

7) Phosphatase: - (Necessary to differentiate from sciuri)

8) Mannitol Fermenter

 S. Xylosus

1) Colony morphology: Large, raised to slightly convex, circular, smooth to rough, opaque, dull to glistening, yellow/orange colonies.

2) Gram stain: G+ cocci in clusters

3) Catalase: +

4) Coagulase: -

5) PYR Broth: +

6) Novobiocin: R

7) Mannitol fermenter

 S. Hominis

1) Colony Morphology: Medium to large, smooth, butyrous, opaque, unpigmented/cream/yellow-orange colonies.

2) Gram stain: G+ cocci in clusters.

3) Catalase: +

4) Coagulase: -

5) PYR Broth: -

6) Novobiocin: S

7) Phosphotase: -

 S. Sciuri

1) Colony morphology: Medium to large, raised, smooth, glistening, circular, opaque, yellow-centered colonies.

2) Gram stain: G+ cocci in clusters.

3) Catalase: +

4) Coagulase: -

5) PYR Broth: -

6) Novobiocin: R

7) Phosphotase: + (Necessary to differentiate from S. Saprophyticus)

8) Mannitol fermenter.

 Micrococcus sp.

(General Characteristics)

1) Colony Morphology: Small to medium, opaque, convex, gamma, white/pink/orange/yellow colonies.

2) Gram stain: G+ coccie in clusters. Tend to form tetrads. Larger than staph.

3) Catalase, Modified Oxidase: +

4) Coagulase: -

5) Lysostaphin (200 ug/ml): R, Furazolidone: R, Bacitracin: S

6) OF Glucose: .

7) Can't produce acid (aerobically) from Glycerol in the presence of Erythromycin (0.4 ug/ml).

Natural Habitat

Skin and mucous membranes of humans and animals.

Sites where Staph is considered to be normal flora?

Skin, nose, throat, gastrointestinal tract, genital tract. (In 25-50% of mammals)

Modes of Transmission?

1) Penetration of skin or mucous membranes, by sharp objects.

2) Direct contact. For example: Inhalation of airborne microbes, handling fomites, or contact with a doctor or nurse.

(After transmission, it may not immediately be pathogenic. It may colonize and become NF. Then later become pathogenic when introduced to a sterile site.)

Common specimens to isolate from?

Pus, wound, abcesses, nasopharyngeal, ear, sputum, stool, blood, CSF, and bone specimens.

Which samples to gram stain from?

Sterile fluids/tissues, tracheal aspirates, wound aspirates.

(Confirm with culture.)

What to cultivate on?

1) BAP, Choc, and MAC

(Most common plates. Used for majority of specimens.)

2) For heavily contaminated samples, selective media should be used. For example: MSA, PEA, and CNA.

Incubation Conditions?

35-37^oC for 18-24 hours. (Possibly 48-72 hours).

Common Biochemical Tests?

(Specifically to differentate between S. Aureus, S. Epidermidis, and S. Saprophyticus)

1) Catalase

2) Coagulase

3) Novobiocin

Extent of Workup for S. Aureus?

1) Slide coagulase test: + (Autoagglutination: -)

2) Depending on the sample, may want to confirm with tube coagulase test.

3) Then do susceptibility panel.

Nutritionally Variant Staph

1) Need various nutrients or increased CO₂ to grow.

2) Two known nutrients: Menadione & Thiamine

3) Healthier growth on Choc in CO₂ or only on Choc. Typically, small,  gamma hemolytic colonies satelliting around other bacteria in mixed culture.

When to suspect NVS?

1) Negative culture after observing staph morphology in gram stain.

2) No staph isolated from patient known to have staph. May have developed due to long term anibiotic therapy.