Staphylococci Flashcards
S. aureus is the leading cause of what infections?
Skin and soft tissue
Bacteremia
Endocarditis
Bone and joint infections
Pulmonary infections
What are some characteristics of S. aureus?
G+
Nonmotile, nonsporeforming
Ferments mannitol
Catalase +
Coagulase +
What is protein A?
Present on the surface of most S. aureus strains
Belong to a group of adhesins called Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMS)
Unique affinity to bind Fc portion of IgG
Inhibits complement activation, opsonization and ADCC
What is clumping factor (coagulase)?
Cell wall-bound coagulase belongs to MSCRAMM that adheres to fibrinogen and fibrin
Initiates fibrin polymerization
Protects bacteria under fibrin mash
What types of toxins do stapylococcal strains have?
Cytolytic toxins (hemolysins)
Exofoliative toxins
Enterotoxins
Toxic shock syndrome toxin-1
What is Panton-Valentine Leukocidin?
Encoded on a mobile phage
Active against PMNs and Macrophages causing cell lysis
Makes S. aureus more resistant to phagocytosis
Airway bleeding, erythroderma and leucopenia, often caused by MRSA
What are toxin-mediated diseases caused by S. aureus?
Toxic shock syndrome
S. aureus food poisoning
Scalded skin syndrome
What skin and soft tissue skin infections can S. aureus cause?
Impetigo, uncomplicated abscess
Necrotizing fasciitis, pyomyositis
Describe S. aureus bacteremia.
Common SAB sources are vascular catheter-related infections, skin infections, and pulmonary infections
Most important distinction is complicated vs. uncomplicated infection
How can SAB be considered uncomplicated?
No endocarditis
No implanted prostheses
Follow-up cultures 2-4 days later are negative
No evidence of metastatic sites of infection
Patient defervesces within 72 hours after initiation of antibiotics
What is the most common cause of infective endocarditis in the industrialized world?
S. aureus
What three major classes of bone and join infections does S. aureus cause?
Osteomyelitis
Native joint septic arthritis
Prosthetic joint infections
What pulmonary infections can S. aureus cause?
Ventilator-associated pneumonia
Post-viral pneumonia
CA-MRSA necrotizing pnemonia
Empyema
What are the four classes of B-Lactams?
Penicillins
Monobactams
Cephalosporins
Carbapenems
What antibiotics can be used against S. aureus?
Most resistant to penicillin
Antistaphylococcal penicillins - Dicloxacillin, Nafcilin, Oxacilin
Firs gen cephalosporins - Sephalexin
B-lactam plus inhiitor
