II. Pathophysiology
- Characteristics
- Gram Positive Cocci in clusters (as with all Staphylococcus)
- Structural Defenses
- Microcapsule (outer)
- Peptidoglycan Cell Wall
- Depends on Transpeptidase (Penicillin Binding Protein) for formation
- Transpeptidase is a target of Penicillins, but many Staphylococcus have developed resistance
- See Penicillin Binding Protein 2A below
- Cell Membrane (inner)
-
Immune System Defenses
- Protein A
- Binds IgG Fc, blocking Opsonization (and Phagocytosis)
- Coagulase
- Promotes clotting (via plasmin activation, and in turn, Fibrin formation)
- Hemolysin (a, b, g, d)
- Like alpha and beta hemolytic Streptococcus, lyse Red Blood Cells
- May also lyse PMNs, Macrophages and Platelets
- Staphylococcus Aureus is named for its gold coloration on BAL
- Leukocidin
- Leukocidins kill WBCs
- Penicillinase
- Beta-Lactamase that inactivates Penicillins
- Penicillinase-resistant Antibiotics (e.g. Methicillin, Nafcillin) are effective against MSSA
- Penicillin Binding Protein 2A (MRSA strains)
- Encoded by a segment of acquired chromosomal DNA (mecA)
- Replaces transpeptidase (Penicillin Binding Protein) in Peptidoglycan cell wall assembly
- Transpeptidase is the typical Penicillin target
- MRSA strains express Penicillin Binding Protein 2A, which confers resistance to most Penicillins
- Protein A
- Tissue Invasion Mediators
- Hyaluronidase (spreading factor)
- Lyses connective tissue proteoglycans
- Staphylokinase
- Lyses Fibrin clots (similar to Streptokinase)
- Lipase
- Breaks down skin surface oils
- Protease
- Lyses tissue Proteins
- Hyaluronidase (spreading factor)
- Exotoxins
- Enterotoxin
- See Food Poisoning
- See Staphylococcal Enterotoxin B
- Heat-stable, preformed toxin resulting in Gastroenteritis soon after ingestion (e.g. unrefrigerated cold salads, meats)
- Exfoliatin
- See Staphylococcal Scalded Skin Syndrome
- Strains that carry exfoliative toxins A and B (only 5% of S. aureus strains)
- Breaks down desmoglein-1 resulting in epidermolysis or Acantholysis (breakage of cell to cell adhesions)
- Results in diffuse skin slouging
- Panton Valentine Leukocidin (PVL) Toxin
- Promotes abscess formation
- More common with community acquired MRSA Infections
- Toxic Shock Syndrome Toxin (TSST-1)
- Similar to pyrogenic toxin from Streptococcus Pyogenes
- Superantigens bind Macrophages and trigger severe Cytokine release
- Enterotoxin
III. Infections
-
Skin Infections
- Cellulitis (esp. with abscess)
- Furuncle or Carbuncle
- Surgical Wound Infection (onset within 48 hours)
- Impetigo
- Superficial Folliculitis
- Toxic Shock Syndrome
- Staphylococcal Scalded Skin Syndrome
- Intravenous Catheter associated infection
- Hydradenitis suppurativa
- Mastitis
- Cardiopulmonary infections
- Staphylococcal Pneumonia (Empyema risk)
- Infective Endocarditis
- Musculoskeletal infections
- CNS Infections
- Gastrointestinal
- Staphylococcal Enterotoxin BFood Poisoning
- Unrefrigerated cold salads, meats, cream pastries
- Onset in 1 to 6 hours (duration to 24 to 48 hours)
- Staphylococcal Enterotoxin BFood Poisoning
IV. Management: Methicillin Resistant
V. Management: Methicillin-Sensitive
- First line Antibiotics (non-Penicillin allergic)
- IV: Nafcillin or Oxacillin
- PO: Dicloxacillin
- Alternative agents
- IV: Cefazolin (Ancef)
- PO: Cephalexin (Keflex)
VI. References
- Gladwin, Trattler and Mahan (2014) Clinical Microbiology, Medmaster, Fl, p. 41-5
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Definition (NCI) | A common bacterial species found especially on nasal mucous membrane and skin (hair follicles); bacterial species that produces exotoxins including those that cause toxic shock syndrome, with resulting skin rash, and renal, hepatic, and central nervous system disease, and an enterotoxin associated with food poisoning; it causes furunculosis, cellulitis, pyemia, pneumonia, osteomyelitis, endocarditis, suppuration of wounds, other infections; also a cause of infection in burn patients; humans are the chief reservoir. |
Definition (NCI_CDISC) | Any bacterial organism that can be assigned to the species Staphylococcus aureus. |
Definition (MSH) | Potentially pathogenic bacteria found in nasal membranes, skin, hair follicles, and perineum of warm-blooded animals. They may cause a wide range of infections and intoxications. |
Definition (CSP) | potentially pathogenic bacteria found in nasal membranes, skin, hair follicles, and perineum of warm blooded animals; may cause a wide range of infections and intoxications. |
Concepts | Bacterium (T007) |
MSH | D013211 |
SnomedCT | 3092008 |
LNC | LP16662-6 |
English | Micrococcus pyogenes, STAPH AUREUS, Staphylococcus aureus, S. aureus, Staphylococcus aureus Rosenbach 1884, Staph. aureus, s. aureus, staphylococcus aureus bacteria, staph aureus, STAPHYLOCOCCUS AUREUS, staphylococcus aureus, Micrococcus aureus, Staphlococcus pyogenes citreus, STAPH. AUREUS, S. AUREUS, Staphylococcus pyogenes aureus, Micrococcus pyogenes var. aureus, Staphylococcus pyogenes citreus, Staphylococcus aureus (organism) |
French | Staphylocoque doré, Staphylococcus aureus |
Swedish | Staphylococcus aureus |
Czech | Staphylococcus aureus, zlatý stafylokok |
Finnish | Staphylococcus aureus |
Russian | STAFILOKOKK ZOLOTISTYI, MIKROKOKK PIOGENNYI, МИКРОКОКК ПИОГЕННЫЙ, СТАФИЛОКОКК ЗОЛОТИСТЫЙ |
Croatian | STAPHYLOCOCCUS AUREUS |
Polish | Gronkowce złociste, Staphylococcus aureus |
Norwegian | Staphylococcus aureus |
Spanish | Micrococcus pyogenes, variedad aureus, Staphylococcus aureus (organismo), Staphylococcus aureus |
German | Staphylococcus aureus |
Italian | Staphylococcus aureus |
Dutch | Staphylococcus aureus |
Portuguese | Staphylococcus aureus |
Ontology: Methicillin susceptible Staphylococcus aureus (organism) (C1635274)
Concepts | Bacterium (T007) |
SnomedCT | 417943000 |
Spanish | Staphylococcus aureus meticilinosensible, Staphylococcus aureus sensible a la meticilina (organismo), Staphylococcus aureus sensible a la meticilina, MSSA |
English | Methicillin susceptible Staphylococcus aureus (organism), MSSA, Methicillin susceptible Staphylococcus aureus |