Gram Positive Cocci Part 1 (Exam 1) Flashcards
(110 cards)
1
Q
What characteristics are shared by all gram-positive cocci
A
all have a spherical shape, no endospores, and are aerobic
2
Q
How are gram positive cocci differentiated
A
presence of catalase
3
Q
What is the function of catalase
A
breaks down peroxide into oxygen and water
4
Q
What are the catalase positive gram positive cocci
A
staphylococcus
5
Q
What are the catalase negative gram positive cocci
A
streptococcus and enterococcus
6
Q
What type of structure does staphylococcus have
A
grape like clusters
7
Q
What type of structure does streptococcus have
A
chains or pairs
8
Q
What type of infections does staphylococcus have
A
pyogenic infection
9
Q
What type of infections does streptococcus have
A
pyrogenic infections
10
Q
What is the difference between pyogenic and pyrogenic infections
A
pyogenic= pus (neutrophils) pyrogenic= fever (TNF alpha, IL-1, IL-6)
11
Q
How will staph appear on gram stain
A
purple cocci in clusters
12
Q
What are the environmental requirements of staph
A
facultative anaerobes
halophiles
non-motile
13
Q
What are halophiles
A
salt loving, can grow in high salt concentrations at at 18-40C
14
Q
What is the catalase reaction results of staph
A
catalase positive
15
Q
What diseases are associated with Staph aureus
A
Toxin mediated diseases cutaneous diseases
systemic diseases
16
Q
What are the toxin mediated diseases of staph aureus
A
Scalded skin syndrome
TSS
Food poisoning
17
Q
What are the cutaneous diseases of staph aureus
A
folliculitis, carbuncles, impetigo, wound infections
18
Q
What are the systemic diseases of staph aureus
A
bacteremia empyema endocarditis osteomyelitis pneumonia septic arthritis
19
Q
What diseases are associated with staph epidermidis
A
bacteremia
endocarditis
UTIs
opportunistic infections
20
Q
How do opportunistic infections of staph epidermidis occur
A
via catheters, shunts, prosthetics
21
Q
What diseases are associated with staph saprophyticus
A
UTIs; opportunistic infections
22
Q
Staph saprophyticus UTIs often occur in what population
A
young, newly sexually active women
23
Q
What are other staph distractors in questions? Be familiar enough to not pick them
A
S. lugdunensis
S haemolyticus
24
Q
Where are staph found normally
A
oropharynx, GI tract, urogenital tract
25
Where is S. epidermidis found on everyone
the skin
26
What percent of population carries S. aureus and are healthy
15-20%
27
How is staph transmitted
direct contact or fomites
28
What is staph susceptible to
hand washing
disinfectants, antiseptics
high temps
29
What are the main virulence factors seen in staph
capsule
peptidoglycan
teichoic acids
30
What role does the capsule of staph play in virulence
inhibits phagocytosis by PMNs
31
What role does peptidoglycan play in staph virulence
makes cell wall rigid
| stimulates cytokine production, activates complement, causes aggregation of PMNs to form an abscess
32
What role do teichoic acids play in staph virulence
major component of cell wall
binds to fibronectin and mediates attachment to mucosal surfaces
33
What type of immunogen is teichoic acid
poor
34
What will be the gram stain, catalase, and coagulase results of staph aureus
gram positive cocci
catalase positive
coagulase positive
35
What agar is used to culture staph aureus
blood agar
| mannitol salt agar
36
What is staph aureus on blood agar
beta hemolytic
37
What are the specific virulence factors associated with staph aureus
adhesins
protein A
toxins
enzymes
38
What do the adhesins do
adhere to host matrix proteins: fibronectin, fibrinogen, elastin, collagen
39
What are the toxin mediated diseases associated with staph aureus
scalded skin syndrome/ bulious impetigo
TSS
food poisoning
40
What are the suppurative infections associated with staph aureus
folliculitis, impetigo, furuncles, boils, bacteremia, endocarditis, pneumonia, empyema, osteomyelitis, septic arthritis
41
What role does protein A play in virulence of S. aureus
binds to Fc receptors of IgG to prevent trigger of immune response
forms immune complexes
binds up complement
42
What virulence factor of S. aureus can be used as identification
Protein A, only found on S. aureus
43
What are the 5 cytolytic toxins of S. aureus
```
alpha
delta
beta
gamma
Panton-Valentine (PV) leukocidin
```
44
What is the function of cytolytic toxins of S. aureus
membrane damaging toxins: act as perforins
45
What are the 2 exfoliative toxins of S. aureus
A and B
46
What are the 8 enterotoxins of S. aureus
A-E, G-I
47
What toxin from S. aureus is associated with toxic shock syndrome
TSST-1
48
What toxins of S. aureus are superantigens
TSST-1, exfoliative toxin A, enterotoxins
49
Where do superantigens bind
to TCR-MHCII groove
50
How will cytolytic toxins of S. aureus affect neutrophils
lyse all neutrophils
51
What does lysis of neutrophils lead to
release of lysosomal enzymes and damage to tissue
52
Describe the effects of the alpha-gamma cytolytic toxins of S. aureus
affect RBCs and other cell types
53
What is the function of the P-V leukocidin in S. aureus
pore formation in PMNs
54
What are the heat tolerances of the exfoliative toxins of S. aureus
ETA is heat stable
| ETB is heat labile
55
What is the function of ETA and ETB
serine proteases
56
What do serine proteases do
split intercellular bridges (desmosomes) in stratum granulosum epidermis
57
Will there be bacteria or WBCs in affected area of S. aureus skin infections
none
58
What are the two diseases associated with exfoliative toxins of S. aureus
Staphylococcal scalded skin syndrome and bullous impetigo
59
What is scalded skin syndrome characterized by
exfoliative dermatitis
60
Who is scalded skin syndrome commonly seen in
neonates and young children
61
What is another name for scalded skin syndrome
Ritter's disease
62
What is the progression of scalded skin syndrome
abrupt onset of localized perioral erythema that covers the entire body
large cutaneous blisters form
epithelial desquamation
63
What is bullous impetigo
localized form of SSSS
64
What is the symptom of bullous impetigo
superficial skin blisters
65
What is different in bullous impetigo than scalded skin syndrome
culture positive
66
What type of toxin is responsibel for S. aureus food poisoning
enterotoxin
67
What are enterotoxins
superantigens that are heat and acid resistant
68
What type of cells are thought to be responsible for the emesis associated with S. aureus food poisoning
mast cells
69
What toxin is associated with staphylococcal pseudomembranous enterocolitis
Enterotoxin B
70
What can enterotoxin b also cause
TSS
71
How can staph aureus lead to TSS
enterotoxins enter blood to cause TSS
hypotension: fluid leaves vasculature and enters tissue
72
What cuases the presentation of S. aureus food poisoning
sudden onset of diarrhea, vomiting
73
Does heating food kill the toxin
no
74
How is S. aureus food poisoning transmitted
human carrier with wound infection contaminates food
75
What foods are common for S. aureus food poisoning
salted meats
custard filled pastries
potato salad
ice cream
76
What will be the result of Toxic shock syndrome toxin-1 staph aureus
cytokine storm leading to hypotension
77
Where are S. aureus that produce TSST-1 found
rapidly in hyperabsorbent tampons
78
What are the clinical manifestation of TSS from staph aureus
fever
hypotension
diffuse macular erythematous rash
79
What is the function of coagulase in S. aureus
converts fibrinogen to fibrin
80
What are the 2 forms of coagulase
bound and free
81
What does bound coagulase do
converts fibrinogen to insoluble fibrin
82
What does free coagulase do
reacts with globulin plasma factor then converts fibrinogen to fibrin
83
What is used to differentiate S. aureus from other staph species
coagulase test
84
What is the function of catalase in s aureus
breakdown H2O2
85
What is the function of penicillinase in S. aureus
breaks down beta lactams
86
What is the pathogenesis of S. aureus
production of toxin: no organisms are present at site
direct invasion and destruction of tissue: suppurative infections, organisms are present
87
What factors contribute to the enhanced virulence of Staph aaureus
presence of foreign body
congenital diseases
88
Where are S. aureus found in TSS and scalded skin syndrome
TSS: toxin in blood, bug not in blood
Scalded skin: bug not found in skin, bug found in mom's vaginal tract or nose
89
How will S. aureus impetigo present
superficial infection
| small macule: pus filled vesicle primarily on face and limbs
90
What population is most at risk of impetigo
young children
91
What is S. aureus foliculitis
pyogenic infection in hair follicles
92
What is folliculitis presentation symptoms
follicle base is raised and reddened, contains pus
stye: base of eyelid
93
What is a S. aureus furuncle
large, painful, raised nodules
94
What is a s. aureus carbuncle
extension of furuncles into subcuaneous tissues and blood; abscess
95
Symptoms of carbuncle
fever, chills, bacteria
96
How will s. aureus appear on microscopy
gram positive cocci in grape like clusters
97
What agars can be used to culture S. aureus
Blood agar
| Mannitol salts agar
98
What seriological tests can be used to diagnoses Staph aureus
antibodies to teichoic acids
99
What gene encodes for methicillin resistance in S. aureus
mecA
100
What does the mecA gene encode
mutant PBP
101
How is the mutant PBP different than normalPBP
low affinity for beta lactams
102
What does low affinity for beta lactams mean
resistance to all penicillins, cephalosporins, carbapenems
103
What chromosome carried the mecA gene
staphylococcal cassette chromosome
104
How is mecA gene detected
PCR and PFGE
105
How is high level antibiotic resistance acquired in S. aureus
van A gene from vancomycin resistant enterococci
106
What antibiotic is used to treat MRSA
vancomycin
107
How is staph epidermidis diagnosed
novobiocin sensitive, will not grow
108
What disease is associated with S. epidermidis
UTI and endocarditis
109
How is staph saprophyticus diagnosed
Novobiocin resistant
110
What disease is associated with staph saprophyticus
UTI in young, sexually active females
