Tuesday, April 21, 2009

Staphylococcus aureus: An Emerging Super Bug

Staphylococcus aureus, a catalase-positive, gram-positive cocci-shapted bacteria, has been implicated in hospital acquired infections since the 1950s when the organisms developed a resistant to penicillin. Even during the golden age of antibiotics, about 50% ofS. aureus strains were found to be resistant to penicillin and later penicillian derivative drugs. The organism quickly became resistnat to newer and more powerful antibiotics, such as tertracycline and the aminoglycosides. S. aureus is a member of the family Micrococcaceae which comprises four genera: Micrococcus, Staphylococcus, Planococcus, and Stomatococcus. Staphyolococcus are natural habitants of skin and mucouse membranes of humans. The bacterial can be found throughout the environment from dust to door knobes. It is common even in the most cleanest healthcare facilities. Most species of Staphycococcus are oppertunistic pathogens, S. aureus , however, has been considered a serious bacterial pathogen since the organism developed a resistance to penicillin in the 1950s.

Staphyococcus aureus : Extracellular Enzymes and Toxins
  • Coagulase
  • Deoxyribonuclease (DNase)
  • Beta lactamase (penicillinase)
  • Exfoliatins
  • Staphylokinase
  • Lipase
  • Hemolysins
  • Leukocidins
  • Enterotoxins
  • A, B, C, C2, D, E and F
  • TSST-1: toxic shock syndrome toxin

Characteristics of the Cell Wall and Surface of S. aureus
  • Protein A: binds to antibody molecules which makes the organism resistant to phagocyctosis and fixation of complement
  • Capsular polysaccharide: enables the organism to resist phagocytosis
  • Peptidoglycan: cell wall consituent which allows the organism to attach to host's cell membranes and resist unfavorable environmental conditions
  • Teichoic acid

Web Site Resources on S. aureus
Four Pediatric Deaths from Community-Aquired Methicillin-Resistant Staphylococcus aureus - Minnisota and North Dakota 1997 - 1999. : MMWR 1999 August 20, 1999/48 (32) ; 707 - 710
HA-MRSA : Methicillin Resistant S. aureus - - Infection Control Fact Scheet from the CDC, Atlanta, GA,

VISA : Vancomycin Resistant - Publication from the CDC on this resistant strain of Staphylococcus aureus.

WHO Emerging Pathogens Report - - 1997 report of vancomycin intermediate resistant S. aureus

Fact Sheet on S. aureus The Doc Shop Mall, Arizona Healthcare Network Web Site

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