ID Board Review/Bacterial Diseases/Gram-positive cocci (GPC)/Staphylococcus aureus
Staphylococcus aureus | |
---|---|
S. aureus | |
Microlab Descriptions | |
Preferred Media/Setting | Readily grows well on animal blood agar (aerobic or anaerobic conditions). Isolates on 7.5-10% NaCl with mannitol.[1] |
Histology | GPC, "cluster of grapes" |
Species Identification | β-hemolytic Catalase (+) Coagulase (+) Oxidase (-) PYR (-) |
Normal Environment | Skin flora |
Associated topics | |
MRSA |
Clinical Presentations
edit- Skin Infections (most common presentations of S. aureus)
- Cellulitis
- Impetigo
- Folliculitis
- Mastitis
- Infection Surgical Wounds
- Infective Endocarditis, especially patients with left-sided valvular heart disease and patients with IV drug use
- S. aureus is often a cause of Osteomyelitis, and is the most common cause of Septic Arthritis
- S. aureus is the most common cause of Spinal Epidural Abscesses and Suppurative Intracranial Phlebitis
- Rarely causes meningitis, but when it does, it's usually after trauma, or Neurosurgery
- S. aureus rarely causes community pneumonia, but is often the cause of Nosocomial (Hospital Acquired) Pneumonia
- Septic Shock
- Prosthetic Joint Infection
- Skin/mucosal breaks or tears
- Foreign body/implant presence
- Prior viral illness (especially superimposed bacterial pneumonia)
- Defects in cellular or humoral immunity
Diagnosis
edit- Bacteremia: Blood culture; low threshold for getting infective endocarditis blood cultures
- Sensitivities to differentiate between MSSA and MRSA
- MRSA Nares Swab PCR (to r/o MRSA pneumonias)
Differential Diagnoses
edit- For skin infections without pus, consider Streptococcus
Resistance Mechanism(s)
edit- Mec A gene → MRSA
Management
edit- ↑ Becker K, Skov RL, von Eiff C: Staphylococcus, Micrococcus, and other catalase positive cocci. In Carroll KC, Pfaller MA, Landry ML, et al.: Manual of clinical microbiology, ed 12, Washington, DC, 2019, American Society for Microbiology, pp 367–398
- ↑ https://www.clinicalkey.com/#!/content/book/3-s2.0-B9780323673204000572?indexOverride=GLOBAL