Chapter 14: Staphylococci Flashcards
What are the Gram stain and morphology characteristics of Staphylococcus?
Catalase-positive, Gram-positive cocci
Often seen in clusters resembling grape bunches.
List three common species of Staphylococcus.
- Staphylococcus aureus (most pathogenic)
- Staphylococcus epidermidis (CoNS)
- Staphylococcus saprophyticus (UTIs)
What is the main virulence factor associated with S. aureus?
Protein A: Binds Fc region of antibodies to prevent phagocytosis.
Name two toxins produced by S. aureus and their effects.
- Enterotoxins: Cause food poisoning
- Toxic Shock Syndrome Toxin-1 (TSST-1): Causes toxic shock
What are the common clinical infections caused by S. aureus?
- Skin infections (boils, impetigo)
- Scalded skin syndrome
- Toxic shock syndrome
- Food poisoning
- Osteomyelitis
- Pneumonia
What type of infections are associated with S. epidermidis (CoNS)?
Nosocomial infections associated with foreign bodies like catheters and implants.
What is the significance of S. saprophyticus in clinical settings?
Common in UTIs, especially in young females; significant even in low numbers if predominant in a urine culture.
What test differentiates S. aureus from CoNS?
Coagulase test (positive in S. aureus).
What is the novobiocin sensitivity result for S. saprophyticus?
Resistant.
What does MRSA stand for?
Methicillin-Resistant Staphylococcus aureus.
Differentiate between HA-MRSA and CA-MRSA.
- HA-MRSA: Hospital-acquired
- CA-MRSA: Community-acquired
What is a critical testing method for detecting MRSA?
PCR for mecA gene (confers methicillin resistance).
What does the D-zone test detect?
Inducible clindamycin resistance.
True or False: S. epidermidis is primarily responsible for skin infections.
False.
Fill in the blank: S. saprophyticus is commonly associated with _______.
UTIs.
What are the primary reservoirs for S. aureus?
- Nares
- Axillae
- Pharynx
- Vagina
- Skin surfaces
What infection control measures are used for MRSA?
- Contact isolation
- Handwashing
- Barrier protection
