Question

Staphylococcus

o Disease caused

o Mode of transmission

o Virulence factors

o Diagnostic methods

Answer 1

Staphylococci cause disease by

• Direct tissue invasion

• Sometimes exotoxin production

Direct tissue invasion is the most common mechanism for staphylococcal disease, including the following:

• Skin infections

• Pneumonia

• Endocarditis

• Osteomyelitis

• Infectious (septic) arthritis

  Multiple exotoxins are sometimes produced by staphylococci. Some have local effects; others trigger cytokine release from certain T cells, causing serious systemic effects (eg, skin lesions, shock, organ failure, death). Panton-Valentine leukocidin (PVL) is a toxin produced by strains infected with a certain bacteriophage. PVL is typically present in strains of community-associated methicillin-resistant S. aureus (CA-MRSA) and has been thought to mediate the ability to necrotize; however, this effect has not been verified.

  Toxin-mediated staphylococcal diseases include the following:

• Toxic shock syndrome

• Staphylococcal scalded skin syndrome

• Staphylococcal food poisoning

Mode of Transmission

Staphylococci are most often transmitted by direct or indirect contact with a person who has a discharging wound or clinical infection of the respiratory or urinary tract, or who is colonised with the organism.

A.Cell Wall Associated

Peptidoglycan

Techoic Acid

Capsule

B.   Cell Surface Associated

Protein A

Clumping Factor

C.   Extracellular Enzymes

Coagulase

Staphylokinase

Lipase

Thermonuclease

Urease

Hyaluronate Lyase (Hyaluronidase)

Proteases

D.   Hemolysins

α-Hemolysin

β-Hemolysin

γ-Hemolysin

Leukocidin

E.   Toxins

Enterotoxin A through E, H, I (the most common type is A)

Toxic Shock Syndrome Toxin-1 (TSST-1); formerly known as enterotoxin F or pyrogenic exotoxin C

Exfoliative TOXIN (epidermolytic toxin) ET A and ET B

Diagnostic Tests

History

physical examination

culture and sensitivity test by collecting swab with pus from the site.

blood test( if infected WBC count may be elevated)