2: Staph Flashcards
1
Q
general features of staph aureus
A
G(+) clusters
catalase (+)
coagulase (+)
2
Q
where do you normally find s. aureus
A
ubiquitous - skin + membranes
3
Q
how does s. aureus normally cause infection?
A
- breaks in skin: wound infections
- secondary overgrowth: sinusitis, OM
- get into blood stream: only problem for immunocompromised -> heart, joints, bones
- most common cause of acute endocarditis, joint infections, osteomyelitis
4
Q
what can s. aureus cause in very immunocompromised patients?
A
necrotizing pneumonias
5
Q
what are s. aureus infections characterized by, histologically?
A
neutrophils!
- supporative: localized collections of pus -> abscesses
- liquefactive necrosis
- role of phagocytosis/opsonization very important
6
Q
what is the role of protein A in s. aureus?
A
it binds Ab’s backwards (on the Fc portion), blocking opsonization
7
Q
problems S. aureus can cause
A
- supporative disease - impetigo, folliculitis
- enteritis
- TSS
- post-op pneumonia
- Staph scalded skin syndrome (SSSS)
- food poisoning (enterotoxin)
8
Q
staph virulence factors
A
- coag (+) in aureus
- enterotoxins
- cytolytic toxins
- exfoliative toxins
- TSST-1
- lipases
- penicillinase
- fibronectin and vitronectin (bind to host cells)
- protein A
9
Q
types of staph infections
A
- overgrowth of normal flora/ URT:
- sinusitis
- OM
- access to sterile areas:
- skin/wound infections
- hematogenous spread from punctures
- bacteremic spread to joints, bone, heart valves, etc.
- ingestion/absorption of toxins
- deep infections in immunocompromised/debilitated
- necrotizing pneumonia
- septicemia
10
Q
types of staph skin/wound infections
A
- furuncle
- carbuncle (many furuncles communicating under skin)
- associated with suture/ foreign bodies
- surgical wounds
- impetigo (horny layers of skin)
- major cause of infection in burns and surgical wounds**
- common cause of nosocomial infections**
11
Q
incubation of staph enterotoxin
A
1-6 h
12
Q
what food is staph food poisoning associated with?
A
- custards
- milk products
- meats
- potato salad
13
Q
describe staph TSS
A
- from T cell super Ag (non-specific activation)
- fever, vasodilation - diffuse macular rash, shock, hypotension
- confused with G(-) sepsis
14
Q
describe staph bacteremia
A
- relatively common, but non-threatening
- seeding of damaged tissues from circulation
- acute endocarditis
- septic arthritis
- osteomyelitis
- meningitis
15
Q
describe staph bronchopneumonia
A
- in debilitated patients (nosocomial)
- secondary to viral infection or obstructive illness
- very destructive purulent lesions**
