Advertisement
 

doctorslounge.com

 
Powered by
Careerbuilder

 

                    Home  |  Forums  |  Humor  |  Advertising  |  Contact
   Ask a Doctor

   News via RSS

   Newsletter

   Infections

   News

 

 Conferences


   CME

   Forum Archives

   Diseases

   Symptoms

   Labs

   Procedures

   Drugs

   Links
   Specialties

   Cardiology

   Dermatology

   Endocrinology

   Fertility

   Gastroenterology

   Gynecology

   Hematology

   Infections

   Nephrology

   Neurology

   Oncology

   Orthopedics

   Pediatrics

   Pharmacy

   Primary Care

   Psychiatry

   Pulmonology

   Rheumatology

   Surgery

   Urology

   Other Sections

   Membership

   Research Tools

   Medical Tutorials

   Medical Software

 

 Headlines:

 
 

Back to Bacteria Index

Staphylococcus

Staphylococcus is a genus of gram-positive bacteria. Under the microscope they appear round (cocci), and form in grape-like clusters (staphyl is Greek for bunch of grapes).

There are many species of staphylococci, most are completely harmless, and reside normally on the skin.

Staphylococcus aureus

One harmful species is Staphylococcus aureus, which can infect wounds.

Morphology

Staphylococcus aureus is a bacterium that causes illnesses ranging from minor skin infections and abscesses, to life-threatening diseases such as pneumonia, meningitis and septicemia.

Cultural characters

More characteristic is its appearance when grown out on agar plates. It appears as large, round golden-yellow (which is where the name aureus comes from) colonies, with beta-haemolysis of blood agar. They are facultative anaerobes.

Antigenic composition

Antigens are one of the mechanisms by which staphylococci can cause disease (pathogenesis). Determination of antigenic composition also helps in the classification of staphylococcus strains.

Important cell wall components and antigens include:

  1. Peptidoglycan
  2. Teichoic acid
  3. Protein A

Pathogenesis

Staphylococci can produce disease (pathogenesis) by their ability to multiply and invade tissues and also through the production of extracellular enzymes and toxins which include:

Coagulase: An enzyme which produces coagulation of plasma around the surface of the staphylococcus and fibrin deposition around the lesions of infection. This protects the staph bacteria from body defense mechanisms such as phagocyctosis (a process by which the body's immune cells 'eat up' the bacterium).

Haemolysins: They cause lysis of red blood cells in can be demonstrated in blood agar.

Exfoliative toxin: The toxin responsible for scalded skin syndrome. The toxin causes desquamation especially in children.

Toxic shock syndrome toxin: A superantigen that causes toxic shock syndrome by release of large amounts of cytokines from immun T cells and macrophages.

Enterotoxins: They are responsible for causing staphylococcal food poisoning.

Others: Catalase, leucocidine, hyaluronidase, staphylokinase, proteinase and lipase.

advertisement.gif (61x7 -- 0 bytes)
 

Are you a doctor or a nurse?

Do you want to join the Doctors Lounge online medical community?

Participate in editorial activities (publish, peer review, edit) and give a helping hand to the largest online community of patients.

Click on the link below to see the requirements:

Doctors Lounge Membership Application


Diseases caused by staphylococcus

Each year some 500,000 patients in American hospitals contract a staphylococcal infection. By changing its chemical makeup slightly to evade attack, S. aureus has become resistant to many commonly used antibiotics. In 1997, physicians were alarmed to encounter staph strains that resist even vancomycin, which used to work when all else failed.

Focal suppuration

  • Superficial infections (folliculitis, carbuncles, boils, abscess formation).
  • Deep seated infections (osteomyelitis, bronchopneumonia, empyema, endocarditis, meningitis).
  • Bacteremia
  • Hospital acquired infections

Toxigenic disease

  • Food poisoning
  • Toxic shock syndrome
  • Scalded skin syndrome

previous.gif (72x17 -- 347 bytes) next.gif (72x17 -- 277 bytes)
 

 advertisement.gif (61x7 -- 0 bytes)

 

 



We subscribe to the HONcode principles of the HON Foundation. Click to verify.
We subscribe to the HONcode principles. Verify here

Privacy Statement | Terms & Conditions | Editorial Board | About us
Copyright 2001-2012 DoctorsLounge. All rights reserved.