Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

RC Test 4 > B4.068 Staphylococcus Aureus > Flashcards

B4.068 Staphylococcus Aureus Flashcards

1
Q

pyogenic

A

pus forming

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

common gram neg pyogenic bacteria

A

Neisseria
E.coli
pseudomonas aeruginosa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

common gram pos pyogenic bacteria

A 
strep pyogenes
staph aureus (80% of pus forming infections)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

suppuration

A

formation of pus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is pus

A

mixture of living and dead neutrophils, bacteria, and cellular debris
usually forms in an area of persistent infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

abscess

A

circumscribed collection of pus
relatively inaccessible to antibodies and antibiotics
may have to be drained to relieve pressure or to resolve infections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

preliminary immune response to pyogenic bacteria

A

activation of macrophages and other innate immune cells
chemotactic factors produced by resident cells to mount and acute phase response
activation of adaptive immunity and Th17 cells
acute inflammation (neutrophil infiltration, production of lysosomal enzymes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how does an abscess form?

A

inflammatory area contained within a thick walled fibrous cap
from the hosts point of view, it has contained the invading organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

describe the overarching features of staph aureus

A 
gram pos coccus
grow in irregular grapelike clusters
nonmotile, non spore forming
catalase positive
coagulase positive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

why is the coccus shape important?

A 
highly resistant shape/size
can survive:
high temp
high salt concentrations
drying
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how does staph aureus react on blood agar

A

colonies are golden
strongly hemolytic
B hemolytic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how many individuals in the US are colonized with s. aureus?

A

as many as 80%
most only intermittently
20-30% colonized persistently

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

who has high rates of colonization?

A

health care workers
persons with diabetes
patients on dialysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

main site of colonization

A

anterior nares

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

other sites of colonization

A

axilla
rectum
perineum
vaginal (higher during menses)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what can happen after abscess formation with s. aureus?

A

organisms can disseminate hematogenously

largely due to bacterial proteolytic enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what are some signs of s. aureus dissemination?

A

pneumonia, bone and joint infections, infection of heart valves

pneumonia: infants, young children, debilitated
endocarditis: janeway lesions, oslers nodes, roth’s spots

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

mortality rate of untreated s. aureus

A

80%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

mortality rate of staph TSS

A

3-5%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

TSS diagnostic criteria

A

fever 102 or higher
rash resembling scarlet fever
desquamation of skin 1-2 weeks after onset
hypotension
clinical/lab abnormalities in 3 organ systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what cell type is a major player against staph aureus

A

neutrophils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is the difference between colonization and non-colonization pathways

A

colonization: ClfB binding, micro-invasion, upregulation of IL-10
non-colonization: bacterial clearance rather than ClfB binding, upregulation of IL-17, neutrophil infiltration

23
Q

what is ClfB and what opposes it?

A

clumping factor B, allows for adhesion

hBD-3 = human B-defensing 3 blocks binding

24
Q

most common cause of septicemia following surgical procedures

A

staph aureus

25
Q

common pathology of MRSA

A

mild to severe skin infections resulting in death if not treated promptly

26
Q

common manifestations of staph infections

A

skin (folliculitis, furuncles/carbuncles, impetigo)
wound
scalded skin syndrome

27
Q

folliculitis

A

tender pustule involving a hair follicle

28
Q

furuncle

A

small abscess that exudes purulent material from a single opening

29
Q

carbuncle

A

aggregate of furuncles with several openings

30
Q

septic arthritis

A

warmth, erythema, and tenderness of the joint together with constitutional symptoms and fever
nearly always unilateral

31
Q

osteomyelitis

A

fever and bony tenderness/a limp

32
Q

endocarditis due to s. aureus

A

usually acute course
most present with high fever
common in IV drug users

33
Q

what bacteria causes many catheter associated infections?

A

staph epidermidis

34
Q

what does staph saprophyticus cause

A

UTIs in sexually active young girls
dysuria and pyuria
responds to many antibiotics

35
Q

examples of s. aureus virulence factors

A 
cell surface:
1. protein A
2. fibronectin binding protein
3. clumping factor
4. other MSCRAMMs
secreted:
1. superantigen
2. cytolysins (toxins)
3. exoenzymes
4. polysaccharide intracellular adhesion
36
Q

function of capsule

A

inhibits phagocytosis

37
Q

function of protein A

A

binds to the H chain of Ab and can inhibit Ab opsonization, preventing phagocytosis
can activate classical complement pathway with Ab/protein A complex

38
Q

how does s. aureus form a fibrin barrier around infectious loci?

A

coagulates plasma with coagulase

binds fibrinogen and causes production of fibrin

39
Q

how can s.aureus break down clots and why?

A

enzymes like staphylokinase break down fibrin and clots

breaks out of walled off areas to colonize rest of body

40
Q

function of toxins

A

toxic for many blood cells (aka cytotoxins, lysins)

41
Q

panton valentine leucocidin (PVL)

A

exotoxin
occurs in <5% of strains
phage derived
causes leukocyte destruction and necrosis, especially in skin and lungs

42
Q

exfoliatin toxins

A

consist of ETA and ETB

result in scalded skin syndrome (SSSS)

43
Q

what is SSSS

A

fever, erythema, blisters
blisters eventually rupture and leave a red base
positive nikolskys sign (bullae moves under skin)

44
Q

bullous impetigo

A

localized SSSS
culture positive (unlike disseminated SSSS)
nikolskys sign not present
primarily occurs in infants and young children

45
Q

which virulence factors are responsible for food poisoning with s. aureus

A

enterotoxins A-E and G-I
superantigens that stimulate certain T cells
stimulate production of cytokines such as IFN-y and TNF causing inflammation of the tissues

46
Q

symptoms of enterotoxins

A

often localized to gut, but can be fatal is systemic
often occur from skin of food handlers
cause vomiting and watery diarrhea 2-6 hours after ingestion
usually self limited

47
Q

characterize toxic shock syndrome

A

caused by a superantigen
first described in kids
most frequently associated with tampons, but at least half of cases not associated with menstruation

48
Q

which exotoxins are associated with TSS

A

TSST-1

enterotoxin B and C

49
Q

how to diagnose s. aureus

A

obtain cultures as appropriate for site of infection

blood cultures from patients with serious infections

50
Q

who is more susceptible to s. aureus infections?

A

neutropenic patients

51
Q

important factors in defense against s. aureus

A
  1. neutrophils
  2. opsonization w Ab and complement
  3. T cells, Th17 recently implicated
  4. IL-1
  5. recognition by TLR-2
52
Q

what can defend against toxins?

A

antibody

53
Q

characterize coagulase negative staph

A

s. epidermidis most common
lack many virulence factors
cause problem in artificial heart valves

RC Test 4 (22 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions