HTHSCI 2HH3 Chapter Notes - Chapter 3: Catalase, Bacteremia, Infective Endocarditis
26 May 2018
School
Department
Course
Professor
Cardiovascular Infections Infection
Bacteremia: persistent bacteremia is suggestive of intravascular infections such as endocarditis
or catheter- related infections
Staphylococcus Aureus
• Gram-positive clusters
• Beta- hemolysins
• Catalase and coagulase positive
• Some strains produce exfoliate EXOtoxins
• Staphylococci are ubiquitous (found everywhere)
• Can survive extreme conditions (pH extremes, oxygen, lack of oxygen), which is why it
can colonize the skin
• Surface proteins that allow the organisms to bind to tissues and foreign bodies coated
with fibronectin, fibrinogen, and collagen
o Allows the bacteria to adhere to inanimate objects and tools
Staphylococcus Aureus Colonization
• Colonizes the skin and mucous membranes (30-50%) of healthy individuals
• Carriage rate is about 50% individuals with frequent needle use (diabetics, recreational
drug use)
o Increased risk of vascular- access bacteremia
Methicillin- Resistant Staphylococcus Aureus (MRSA)
• Strain of s. aureus that is resistant to beta- lactam antibiotics
• Alteration in the penicillin binding protein that is carried on the mecA gene
• Organism is resistant to ampicillin, piperacillin, floxacillin, all cephalosporins,
meropenem, and all beta- lactam/ beta- lactamase inhibitor combinations
• MRSA strain contains a Panton-valentine-leucocidin gene that allows the pathogen to
penetrate intact skin and cause a more severe infection
Treatment
• Because of its resistance, it can only be treated with few antibiotics
o Vancomycin, trimethoprim-sulfamethoxazole, linezolid, etc.
MRSA: Infection Control
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