Staphylococcus aureus is a gram-positive, spherical bacterium that can cause several diseases in humans. It is a normal member of the skin and nasal flora but can become pathogenic. S. aureus produces several toxins and enzymes that allow it to infect the skin, blood, lungs, heart, bones and joints. Diseases include impetigo, cellulitis, abscesses, pneumonia, osteomyelitis, endocarditis and toxic shock syndrome. Laboratory diagnosis involves culturing and identifying its characteristic gram-positive cocci in clusters and positive tests for catalase, coagulase and DNase. Treatment involves antibiotics like oxacillin or vancomycin depending on antibiotic resistance.

1. Staphylococcus aureus
Presented By
R.Jayapriya(BP211513),
1st M.Sc Microbiology,
Sacred Heart College(Autonomous),
Tirupattur ,Tamil Nadu ,India.

2. GENERAL CHARACTERISTICS
• Gram’s classification – Gram positive bacteria
• Shape – Spherical (Cocci)
• Arrangement – Bunched or Grape like clusters
• Motility – Non-Motile
• Capsule - Absent
• Endospores – Absent
• Respiration – Aerobic/Facultative anaerobic
• Optimum Temperature - 37 °C
• Optimum pH – 7.0 to 7.5
• Normal human flora on skin and mucosal surfaces.
• The organisms are ubiquitous, so there are no Geographic or seasonal limitations.
• Discovered by Anton J. Rosenbach (German Surgeon) in 1884 .

3. PATHOGENICITY OF Staphylococcus
aureus:
Staphylococcus aureus Infections are mainly transmitted by
a) Direct contact with an infected person
b) By using a contaminated object
c) By inhaling infected droplets dispersed by sneezing or
coughing.
1 to 6 Hours

4. (i) Structural components:
A)Capsule
b) Slime layer
c) Peptidoglycan
d) Teichoic acid
e) Protein A
(ii) Toxins:
a) Cytotoxins
b) Exfoliative toxins (ETA & ETB)
c) Enterotoxins (A to R)
d) Toxic Shock Syndrome Toxin 1

5. (iii) Enzymes:
a) Coagulase
b) Hyaluronic acid
c) Fibrinolysin
d) Lipases
e) Nucleases
f) Beta Lactamase
g) Staphylokinase

6. PATHOGENESIS OF Staphylococcus aureus:
 Staphylococcus aureus enters into the surface of the
Skin, grows into Hair follicles and invadesSebaceous
glands.
 After that, it triggers Fever and Inflammation, which
are natural responses against infection, and causes the
follicle to enlarge and fill with pus composed of
leukocytes, dead cells, and bacteria.
 The infection may spread into the Hypodermis to form
a Furuncle or into neighboring hair follicles to form a
Carbuncle.

7.  Staphylococcus aureus may also spread into the
blood - a condition called Bacteremia and is carried to
the lining of the heart, lungs, and bones, causing
Endocarditis, Pneumonia and Osteomyelitis,
respectively.

8. CLINICAL DISEASES CAUSED BY
Staphylococcus aureus:
I) TOXIN – MEDIATED DISEASES :
 Also known as Ritter von Ritterschein disease ,
Ritter disease, and Staphylococcal epidermal
necrolysis.
 Superficial blistering skin disorders caused by the
Exfoliative toxins of some strains of Staphylococcus
aureus.
 Exfoliative toxin that causes the outer layers of Skin to
Blister within the upper layers of the skin) and Peel.

9.  Staphylococcal Food Poisoning results after
consumption of food contaminated with heat-stable
Enterotoxin.
 Symptoms include Nausea,Vomiting, Abdominal
cramping and Diarrhea.
 In more severe cases - Dehydration, Headache, Muscle
cramping, and changes in Blood pressure and Pulse
rate may occur.
 The condition is typically over in 2 days. But it is not
unusual for complete recovery to take 3 days and
sometimes longer in severe cases.

10.  Toxic Shock Syndrome (TSS) is a rare but serious
medical condition caused by a bacterial infection. The
bacterium Staphylococcus aureus gets into the blood
stream and produces Toxins.

Sudden high fever; Low blood pressure ;Vomiting;
Diarrhea; Rash resembling a Sunburn; Confusion;
Muscle aches; Redness of eyes, mouth & throat;
Seizures; Headaches; Shock; Renal failure and
sometimes Death.

11. (II) SUPPURATIVE INFECTIONS:
 The most common cause of impetigo is bacteria called
Staphylococcus aureus. Another bacteria source is group A
Streptococcus.
 Impetigo is a common and highly contagious skin infection
that mainly affects infants and children.
 Impetigo usually appears as red sores on the face,
especially around a child's nose and mouth, and on hands
and feet.
- Impetigo involving hair follicles

12. - Large, painful, pus-filled
cutaneous nodules.
– Coalescence of Furuncles with
extension into the subcutaneous tissues and evidence of
systemic disease
- Spread of bacteria into the blood from a
focus of infection.
– Endocarditis characterized by damage
to the endothelial lining of the heart.

13. - Consolidation and
abscess formation in the lungs; seen in the very young
and elderly and in patients with underlying or recent
pulmonary disease; a severe form of necrotizing
pneumonia with septic shock and high mortality is
recognized.
- Destruction of bones,
particularly the metaphyseal area of long bones.
Painful erythematous joint with
collection of purulent material in the joint space.

14. LABORATORY DIAGNOSIS OF Staphylococcus aureus:
 Gram stating – Violet coloured Gram positive cocci
arranged in form of clusters.
 Motility test – Non-Motile.
 Nutrient agar - Smooth, golden yellow colonies
 Blood agar – Beta Hemolysis.
 MacConkey agar – Pink coloured Lactose fermenting
colonies.
 Selective medium - Mannitol Salt Agar (MSA) –

15. BIOCHEMICAL TESTS:
a) Catalase test - Positive
b) Oxidase test - Negative
c) Urease test – Negative
d) Indole test - Negative
e) Methyl Red (MR) test – Negative
f) Voges Proskauer (VP) test - Positive
g) Citrate utilization test – Positive
h) Starch Hydrolysis – Negative
i) Casein Hydrolysis - Negative
k) Tellurite Reduction Test – Positive
l) DNase Test - Positive

16. ANTIBIOTIC THERAPY AND TREATMENT:
 Oxacillin (or other Penicillinase - resistant Penicillin)
 Vancomycin for Oxacillin-resistant strains.
 Removal of the foreign body is often required for
successful treatment.

17. THANK YOU