bacteriology Flashcards
General characteristics of S. aureus are
- Gram-positive cocci
- Catalase positive
- Nonmotile
- Aerobic or facultatively anaerobic
- Medium, circular and entire, smooth, convex, and usually white-to-yellow colonies
Transmission of Staphylococcus
- Person-to-person
Persistent carriers
Intermittent carriers
Noncarriers
Capsule
- Slime laver
- Biofilm
Cell wall
- Peptidoglycan
- Protein A
Disrupts smooth muscle and toxic to many cell types
Alpha toxins
Heat labile sphingomyelinase
Beta toxins
Cytotoxic to erythrocytes
Delta toxins
Mav function in association with Panton-Valentine Leuckocidin (PVL)
Gamma toxins
Heat stable enterotoxins in up to
50% of S. aureus strains
Localized skin infections
- Folliculitis
- Furuncles
- Carbuncles
- Impetigo
Infections in those who are immunocompromised
microcccus
- Skin and soft-tissue infections
- Toxic shock syndrome (TSS)
- Food poisoning
- Scalded skin syndrome
S. aureus
*Associated with UTIs in sexually active young women
S. saprophyticus
Panton- Valentine leukocidin (PVL) toxin
S. aureus
community -associated infections
MRSA or CA-MRSA
- Usually infects neonates
- Cause extensive sloughing of epidermis to produce a burn like effect on the patient
Scalded skin syndrome
Systemic effects on the patients; including fever, desquamation, hypotension leading to shock and death
Toxic Shock syndrome
Virulence Factors of Staphylococcus aureus
- Produce and secretes toxins and enzymes
- Leucocidin mediates destructio of phagocytes
- Clumping factor
- Coagulase
- Hyaluronidase
- Potent exotoxins (TSST-1) and enterotoxin
Spectrum of Diseases and infections in Staphylococcus aureus
- Necrosis
- Localized skin infections
- Folliculiis
- Furuncles (Boils)
- Carbuncles
- Impetigo
- Coagulase negative staphylococci
- Less virulent
- Their prevalence as nosocomial infection is ,if not more related to medical procedures and practices
Staphylococcus epidermidis
virulence of epidermidis
- Certain factors facilitate attachment to implanted medical devices
- Production of exopolysaccharide “slime” or biofilm