Agents of bacterial skin infection

Question 1

manifestations from a distant infection site

Answer 1

toxin mediated

Question 2

resident skin flora

Answer 2

mostly bacterial, includes staph epidermidis and p. acnes

Question 3

transient skin flora

Answer 3

mostly staph aureus and strep pyogenes (group A)

Question 4

spreading exogenous infection confined to epidermis

Answer 4

impetigo

Question 5

spreading exogenous infection involving dermal lymphatics

Answer 5

erysipelas

Question 6

spreading infection involving all the way down through subcutaneous layer

Answer 6

cellulitis

Question 7

2 or more furuncles

Answer 7

carbuncle (abscess formation)

Question 8

myonecrosis

Answer 8

muscle tissue death/infection

Question 9

all streptococci are gram ___ and catalase ___

Answer 9

gram + and catalase -

Question 10

all staphylococci are catalase ___

Answer 10

catalase + (distinguishes them from strep)

Question 11

pyogenic cocci are obligate..?

Answer 11

obligate extracellular bacteria meaning they do not want to be inside cells

Question 12

how do pyogenic cocci avoid being phagocytosed?

Answer 12

anti-phagocytic virulence factors

but sometimes cells have antibodies against these factors allowing uptake by PMNs

Question 13

strep are classified by three things…

Answer 13

1. hemolytic pattern (beta is clearing, alpha is partial)
2. physiological traits and biochemical reactions
3. antigenic composition (group A has A antigen in cell wall)

Question 14

beta hemolytic strep

Answer 14

complete lysis of rbc around colony on blood agar

Question 15

alpha hemolytic strep

Answer 15

partial hemolysis of rbc around colony on blood agar

Question 16

gold standard detection method for group A strep?

Answer 16

culture

–strep is sensitive to bacitracin –> will be a clearing around bacitracin disc

Question 17

group A strep

Answer 17

strep pyogenes

Question 18

rapid looking for lancefield group A detection

Answer 18

strep test with great specificity but bad sensitivity

detects carbohydrate antigen that is part of cell wall murein layer, no virulence factor

Question 19

major virulence factor in s pyogenes (group A)

Answer 19

M proteins

Question 20

m protein

Answer 20

anti-phagocytic virulence factor in strep pyogenes

involved in binding to epidermis

Question 21

why cant an antibody to hyaluronic acid be made against s pyogenes?

Answer 21

because humans have hyaluronic acid inour bodies so that would not be protective

Question 22

components of streptococcal cell wall

Answer 22

capsule, m proteins, lipotechoic acid, phospholipid membrane

Question 23

super antigens

Answer 23

stimulate excessive cytokine production –> lots of T cells

exotoxins involved in scarlett fever and toxic shock-like syndrome

Question 24

extracellular virulence

Answer 24

exotoxins/super antigens
streptolysin 0
DNAases
streptokinase
C5a peptidase

Question 25

depolymerizes cell-free DNA in purulent lesions

Answer 25

DNAases

Question 26

lyses blood clots helping bacteria spread

Answer 26

streptokinase

Question 27

degrades complement component C5a that attracts PMNs

Answer 27

c5a peptidase

Question 28

strawberry tongue, circum-oral pallor, desquamation

Answer 28

scarlet fever

Question 29

purulent (pus) skin lesion

Answer 29

pyoderma

Question 30

four pyodermas caused by s pyogenes

Answer 30

impetigo erysipelas cellulitis necrotizing fasciitis

Question 31

strep vs staph toxic shock syndrome

Answer 31

clinically the same except with strep patients are bacteremic(bacteria in blood) -->may have necrotizing fasciitis

Question 32

autoimmune cross reaction between anti-M antibodies and the heart tissue group A strep

Answer 32

rheumatic fever

Question 33

renal injury due to deposition of antigen-antibody complexes on glomeruli

Answer 33

acute glomerulonephritis

Question 34

PANDAS syndrome

Answer 34

pediatric autoimmune neuropsychiatric disorder associated with group A strep

Question 35

5 criteria for PANDAS

Answer 35

``` prescence of OCD or tic pediatric onset abrupt/episodic GAS infections neurologic abnormalities (hyper, tics, etc) ```

Question 36

how to treat pandas?

Answer 36

penicillin G or oral cephalisporins if there is a co-infection with staph aureus, use penicillinase (will treat both)

Question 37

penicillinase

Answer 37

resistant antibiotic to treat both strep pyogenes and staph aureus at the same time

Question 38

what drug will treat both s pyogenes and s aureus simultaneously

Answer 38

penicillinase

Question 39

gram +, catalase +, coagulase -

Answer 39

staph epidermidis or staph saprophyticus

Question 40

gram +, catalase +, coagulase +

Answer 40

staph aureus

Question 41

white nonhemolytic colony morphology

Answer 41

staph epidermidis

Question 42

yellow beta hemolytic colony

Answer 42

staph aureus

Question 43

gram +, catalase -

Answer 43

streptococci

Question 44

catalase test

Answer 44

H2O2 plus bacteria - ->bubbling = catalase + (staph) - -> no bubbling = catalase - (strep)

Question 45

hallmark of staph skin infections?

Answer 45

presence of pus

Question 46

how to treat furuncle?

Answer 46

heat and or drainage antibiotics if it invades subcutaneous layer

Question 47

hydradentic suppurativa

Answer 47

infection of sweat glands

Question 48

stye is what kind of infection and can progress to what?

Answer 48

folliculitis | can progress to cellulitis

Question 49

impetigo is usually due to?

Answer 49

group A strep

Question 50

binds fibronectin and induces shock

Answer 50

techoic acid

Question 51

converts fibrinogen to fibrin

Answer 51

coagulase

Question 52

hyaluronidase

Answer 52

acts on hyaluronic acids in CT facilitating dissemination through subcutaneous

Question 53

potent pore former, toxic to many cell types

Answer 53

alpha hemolysin

Question 54

also called spyngomyelinase C, kills cells via hydrolysis of membrane phospholipids

Answer 54

beta toxin

Question 55

cytolytic, nonspecific detergent like action

Answer 55

delta toxin

Question 56

poreforming toxins, lysis of neutrophils and macrophages

Answer 56

gamma toxin and panton-valentine leukocidin (PVL)

Question 57

staph intermedius

Answer 57

coagulase/staph zoonotic pathogen common from dog bite or exposure common oral, nasal, skin flora in healthy dogs

Question 58

food poisoning is caused by

Answer 58

staph enterotoxins

Question 59

TSST1

Answer 59

staph aureus induced toxic shock syndrome

Question 60

exfoliatin A/B cause...

Answer 60

staph aureus impetigo, Scalded skin syndrome, scarlet fever

Question 61

exfoliatin

Answer 61

a serine protease that splits desmosomes in granulosum

Question 62

major risk group for TSS

Answer 62

menstruating women use ofcontraceptive devices nasal surgery patients

Question 63

semi-synthetic penicillin | resistant to penicillinase

Answer 63

methicillin

Question 64

penicillinase-producing s aureus

Answer 64

generally plasmid encoded transferred by conjuugation or transduction treat with methicillin

Question 65

MRSA

Answer 65

due to mecA gene (encodes PBP2 - altered penicillin binding protein) methicillin resistance

Question 66

what was developed to treat MRSA?

Answer 66

vancomycin - glycopeptide that binds to D-ala-D-ala residues of peptidoglycan precursors - stops chain

Question 67

VISA

Answer 67

vancomycin intermediate of s aureus

Question 68

VRSA

Answer 68

vancomycin resistant s aureus acquisition of vanA gene peptidoglycan precursor with D-ala-Dlactate terminus hasnt spread as much as mrsa

Question 69

what causes UTI, endocarditis, infections of foreign devices, endophthalmitis, osteomyelitis?

Answer 69

s epidermidis

Question 70

biofilms

Answer 70

s epidermidis irreversible adherence to device surfaces by extracellular polymers in a structural matrix protects bacteria from antibiotics nosocomial detachment of bacteria can lead to sepsis

Question 71

nosocomial

Answer 71

arising in a hospital

Question 72

culprits of nosocomial skin infections

Answer 72

staph eureus mRSA acinetobacter baumanii pseudomonas aeruginosa