Staphylococcus aureus: Difference between revisions
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Staphylococcus aureus
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| − | = Microbiology = |
+ | == Microbiology == |
* Facultative anaerobic, Gram-positive coccus |
* Facultative anaerobic, Gram-positive coccus |
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* Colony morphology: large, round, golden yellow colonies, often hemolytic on blood agar |
* Colony morphology: large, round, golden yellow colonies, often hemolytic on blood agar |
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| − | = Pathophysiology = |
+ | == Pathophysiology == |
| − | == Virulence factors == |
+ | === Virulence factors === |
* Surface proteins for fibrinogen and other substances (used for binding to host endothelial cells) |
* Surface proteins for fibrinogen and other substances (used for binding to host endothelial cells) |
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* Superantigens that bind to MHC molecules and T-cell receptors, leading to release of huge amounts of cytokines |
* Superantigens that bind to MHC molecules and T-cell receptors, leading to release of huge amounts of cytokines |
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| − | = Clinical Presentation = |
+ | == Clinical Presentation == |
| − | == Skin and soft tissue infections == |
+ | === Skin and soft tissue infections === |
* Boils and carbuncles |
* Boils and carbuncles |
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| − | == Scalded-skin syndrome == |
+ | === Scalded-skin syndrome === |
* Aka Ritter disease |
* Aka Ritter disease |
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* Sunburn-like, bullous rash that can lead to skin loss (most common in kids with Staph infections of the nasopharynx or skin) |
* Sunburn-like, bullous rash that can lead to skin loss (most common in kids with Staph infections of the nasopharynx or skin) |
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| − | == Bacteremia == |
+ | === Bacteremia === |
* See [''Staphylococcus aureus'' bacteremia](Staphylococcus aureus bacteremia.md) |
* See [''Staphylococcus aureus'' bacteremia](Staphylococcus aureus bacteremia.md) |
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| − | == Infective endocarditis == |
+ | === Infective endocarditis === |
* Usually more acute presentation |
* Usually more acute presentation |
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* High mortality |
* High mortality |
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| − | == Myriad other infections == |
+ | === Myriad other infections === |
* Osteomyelitis |
* Osteomyelitis |
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* Pneumonia, especially ventilator-associated or influenza-related |
* Pneumonia, especially ventilator-associated or influenza-related |
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| − | == Superantigen-related syndromes == |
+ | === Superantigen-related syndromes === |
* Food poisoning |
* Food poisoning |
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* Staphylococcal toxic-shock syndrome |
* Staphylococcal toxic-shock syndrome |
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| − | = Management = |
+ | == Management == |
| − | == Methicillin-susceptible ''Staphylococcus aureus'' (MSSA) == |
+ | === Methicillin-susceptible ''Staphylococcus aureus'' (MSSA) === |
* First-line: cloxacillin, then cefazolin or cephalexin |
* First-line: cloxacillin, then cefazolin or cephalexin |
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* Others: clindamycin, fluoroquinolones, Septra, doxyxycline, erythromycin |
* Others: clindamycin, fluoroquinolones, Septra, doxyxycline, erythromycin |
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| − | == Methicillin-resistant ''Staphylococcus aureus'' (MRSA) == |
+ | === Methicillin-resistant ''Staphylococcus aureus'' (MRSA) === |
* First-line: vancomycin |
* First-line: vancomycin |
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Revision as of 16:09, 15 August 2019
Microbiology
- Facultative anaerobic, Gram-positive coccus
- Microscopy: groups or clusters ("cluster of grapes")
- Colony morphology: large, round, golden yellow colonies, often hemolytic on blood agar
Pathophysiology
Virulence factors
- Surface proteins for fibrinogen and other substances (used for binding to host endothelial cells)
- Membrane-damaging (hemolytic) toxins
- Exfoliative toxins (A and B) which disrupt the junction between epidermal cells
- Superantigens that bind to MHC molecules and T-cell receptors, leading to release of huge amounts of cytokines
Clinical Presentation
Skin and soft tissue infections
- Boils and carbuncles
Scalded-skin syndrome
- Aka Ritter disease
- Sunburn-like, bullous rash that can lead to skin loss (most common in kids with Staph infections of the nasopharynx or skin)
Bacteremia
- See [Staphylococcus aureus bacteremia](Staphylococcus aureus bacteremia.md)
Infective endocarditis
- Usually more acute presentation
- High mortality
Myriad other infections
- Osteomyelitis
- Native and prosthetic joint infections
- Pyomyositis
- Deep organ abscesses
- Surgical site infections
- Pneumonia, especially ventilator-associated or influenza-related
- Food poisoning
- Staphylococcal toxic-shock syndrome
Management
Methicillin-susceptible Staphylococcus aureus (MSSA)
- First-line: cloxacillin, then cefazolin or cephalexin
- Others: clindamycin, fluoroquinolones, Septra, doxyxycline, erythromycin
Methicillin-resistant Staphylococcus aureus (MRSA)
- First-line: vancomycin
- Others: linezolid (if lungs) and daptomycin (if blood), but also consider Septra, ciprofloxacin, doxycycline, and clindamycin
