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Microbiology Flashcards

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Dermatology Board Prep flashcards
1
Q

define virulence

A

the capacity of a microbe to cause damage to the host

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2
Q

list 5 virulence factors

A

adhesion- enables binding of the organism to host tissue

invasin - enables the organism to invade a host cell/ tissue

impedin - enables the organism to avoid host defense mechanism

aggressin - causes damage to the host directly

modulin - induces damage to the host cell indirectly

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3
Q

list 6 virulence factors of staph aureus

A

fibrinogen binding protein

leukocidin (PVL)

TSST-1 (toxin)

adhesion

kills leukocytes

shock, rash, desquamation

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4
Q

why is there many different presentation/ conditions and syndromes caused by staph aureus infection

A

lots of different strains and sub strains with different virulence factors

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5
Q

what do toxins do

A

cause direct damage to immune system or systemic damage to host

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6
Q

name 2 toxinoses caused by s. aureus

A

toxic shock, scaled skin syndrome

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7
Q

name 6 skin staph aureus infections

A

rash, folliculitis, abscess, carbuncle, impetigo, scaled skin syndrome

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8
Q

name symptoms of TSS

A

rapid progression (48hrs), high fever, vomiting, diarrhea, sore throat, muscle pain, diffuse macular rash and desquamation, hypotension

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9
Q

what toxin causes scaled skin syndrome and what do they target

A

exfoliatin toxins

desmoglein-1 (DG-1)

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10
Q

who gets SSS and where do they get it

A

neonates; face, axialla and groin

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11
Q

what do superantigens do

A

overstimulate immmune system (activate 1 in 5 t cells when normal is 1 in 10000) causing massive release of cytokines and inappropriate immune response

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12
Q

how does staph aureus cause TSS

A

on tampon diffuse through wall of vagina into bloodstream then superantigens overstimulate immune response

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13
Q

name components invloved in adhesion

A

extra cellular matrix, fibrinogen binding, collagen binding

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14
Q

name components of host defence evasion

A

superantigens, alpha toxin and PVL, coagulase

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15
Q

what is PVL and what skin infections is it associated with

A

panton valentine leukocidin

reccurent furunculosis
sepsis
necrotising fascitis (PVL and alpha toxin linked with CA-MRSA responsible for NF)

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16
Q

give features of nectorising pneumonia

A

precedes influenza like illness, rapid progression, acute resp distress, deterioration in pulmonary function

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17
Q

strep pyogens is beta haemolytic- why is this important

A

as haemolysis breakdown of red blood cells- has power to do this in host and cause damage to tissues

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18
Q

what skin infections can be cause by s. pyogenes

A

impetigo, cellulitis, NF

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19
Q

where does s. pyogenes adhere to

A

oropharynx and nasopharynx on non ciliated cells covered in mucus

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20
Q

name two components of s. pyogenes adhesion

A

hyaluronic acid, CD44 +ve keratinocytes

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21
Q

how does s. pyogenes evade host defense

A

CAPSULEs

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22
Q

give features of impetigo

A

highly contagious through contact with discharge on the face (usually face)

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23
Q

name 6 GAS diseases

A

impetigo, cellulitis, erysipelas, NF, TSS, pyrogenic exotoxin

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24
Q

what is GAS

A

group A streptocoocal

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25
Q

what are features of erysipelas

A

localised, fever, rigours and nausea

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26
Q

where in skin is a cellulitis infection

A

dermis

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27
Q

name two components of GAS tissue/ cell destruction

A

hemolysins, stretolysin

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28
Q

does s aureus or s pyrogenes cause TSS- why

A

both- as produce similar exo proteins, virulence factors and diseas mechanisms

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29
Q

where is s pyogenes normally found

A

pharynx

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30
Q

how does sebum protect from infection

A

fatty acids inhibit bacterial growth

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31
Q

what does a skin swap showing staph epi mean

A

most likely a commensal

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32
Q

MRSA is transient, what does this mean

A

colonies in skin come and go

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33
Q

how can skin commensals protect from infection

A

competition with pathogens

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34
Q

name three common skin commensals

A

staphylococcus epidermis

corynebacterium sp. (diptheroids)

propionobacterium so.

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35
Q

when can skin commensals cause infection

A

if they enter the blood stream could cause infection

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36
Q

cocci in bunches=

A

staph

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37
Q

cocci in chains=

A

strep

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38
Q

when do you take blood cultures to diagnose an infection

A

if patient is showing systemic symptoms

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39
Q

ONLY 1 staph is coagulase positive, which one is it

A

s. aureus

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40
Q

which is the most common type of beta haemolytic strep

A

group A

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41
Q

how do you classify streptococci

A

haemolysis

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42
Q

what are the 3 subdivisions of streptococci

A

alpha (partial) haemolysis
beta (complete) haemolysis
gamma (non) haemolytic

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43
Q

name 2 alpha haemolytic strep and what they cause

A

strep. pneumonia (pneumonia)

strep viridans (commensals, endocarditis)

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44
Q

name 2 beta haemolytic strep and what they cause

A

group A strep (throat, skin infection)

group B strep (neonatal meningitis)

groups C, G ect

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45
Q

name a non haemolytic strep and what it causes

A

enterococcus sp. (gut commensal, UTI)

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46
Q

how do you distinguish staphylococci

A

coagulase testing

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47
Q

name the coagulase positive staphylcocci and what it causes

A

staph aureus, wound, bone, joint and skin infections

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48
Q

what type of environment does staphylococcus grow in best

A

is aerobic (best in air) and facultatively anaerobic (can grow without air)

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49
Q

why does staph aureus test coagulase positive

A

as produces the enzyme coagulase

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50
Q

what antibiotics are used to treat s aureus infections

A

FLUCLOXACILLIN

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51
Q

what is MRSA

A

methicillin resistant staph aureus

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52
Q

name 3 toxins produces by strains of s aureus and what they cause

A

enterotoxin- food poisening
SSSST- staphylococcal scaled skin syndrome toxin
PVL- panton valentine leucocidin

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53
Q

why is flucloxacillin used to treat s aureus

A

as other antibiotics have much higher mortality rates

54
Q

name 7 skin infections caused by staph aureus

A 
boils and carbuncles,
minor skin sepsis',
cellulitis,
infected eczema,
impetigo,
wound infection,
Staph scaled skin syndrome
55
Q

can antibiotics penetrate pus

A

no

56
Q

what are the treatment options for MRSA causing skin and soft tissue infections

A

NOT FLUCLOXACILLIN

  • doxycycline (oral)
  • co-trimoxazole
  • clindamycin
  • linezolid
57
Q

what are the treatment options for MRSA causing bloodstream infections

A

NOT FLUCLOXACILLIN

  • vancomycin
  • daptomycin
58
Q

are coagulase negative staph usually skin commensals or pathogens

A

commensals

59
Q

when can coagulase negative staph cause infections

A

in association with implanted material- produces slime that enables it to stick to prosthetic material

60
Q

in who can staph saprophyticus cause UTIs

A

in women of child bearing age

61
Q

are staph and strep cocci gram positive or negative

A

positive

62
Q

what environment to streptococci grow best in

A

aerobic and facultatively anaerobic

63
Q

are beta haemolytic steptococci pathogenic or commensal organisms

A

pathogenic

64
Q

name a toxin produced by beta haemolytic strep that causes damage to tissues

A

haemolysin

65
Q

what classifies beta haemolytic strep in groups (a, b, c…)

A

antigenic structure on surface (serological grouping)

66
Q

what infections does group A strep. pyogenes cause

A

infected eczema, impetigo, cellulitis, erysipelas, NF

67
Q

where is strep viridans a commensal of

A

mouth, throat, vagina

68
Q

what antibiotics for strep. pyogenes (group A strep)

A

penicillin, also flucloxacillin

69
Q

what is the treatment for NF

A

surgical debridement and antibiotics

70
Q

what are helpful diagnostic signs of NF

A

pain much worse than presentation, crepitous sound when you press it, air on xray, CT and MRI if very severe

71
Q

what is NF

A

necrotising facitis- bacterial infection spreading along fascial planes below skin surface causing rapid tissue destruction

72
Q

what are the two types of NF

A

type 1- mixed anaerobes and coliforms (post abdo surgery)

type 2- group A strep infection

73
Q

what antibiotic for NF

A

depends on microorganisms found on tissue taken from surgery

74
Q

what is the underlying problem of leg ulcers

A

vascular

75
Q

when should you take a swap from a leg ulcer

A

if signs of cellulitis or infection are present

76
Q

what organisms are worth treating if found on leg ulcers

A

strep pyogenes (group A), staph aureus, beta haemolytic strep, anaerobes (especially in diabetic patients)

77
Q

when is an ulcer likely to be associated with osteomyelitis

A

if there for over 2 months and bigger than 2 cm

78
Q

what is tinea

A

ringworm

79
Q 
name the places affected by tinae form the name
tinea capitis
tinea barbae
tinea corporis
tinea manuum
tinea unguium
tinea cruris
tinea pedis
A 
captitis- head
barbae- beard
corporis- body
manuum- hand
unguium- nails
cruris- groin
pedis- foot (athletes foot)
80
Q

describe the pathogenesis of ring worm

A

fungus enters through abraded or soggy skin

hyphae spread in stratum corneum

infects keratonised tissues only (skin, hair, nails)

increased epidermal turnover causes scaling

inflammatory response provoked (dermis)

hair follicles and shafts invaded

lesion grows outward and heals in centre giving a ring appearance

81
Q

who does ringworm generally and scalp ringworm gernerally affect

A

generally men

scalp children

82
Q

what are the sources of dermatophyte infections (fungal)

A

other humans (most common)
animals
soil

83
Q

name another fungal organism spread by human to human transmission

A

trichophyton rubrum

84
Q

how do you diagnose fungal (dermatophyte) infections

A

clinical appearance
woods light (fluorescence)
skin scrapings, nail clippings, hair

85
Q

where should skin scrapings be taken from

A

the edge of the scaly lesion

86
Q

how do you treat small areas of fungally infected skin or nails

A

clotrimazole (canestan) cream/ similar

topical nail paint (amorolfine)

87
Q

how do you treat fungal scalp infections

A

terbinafine orally

itraconazole orally

88
Q

where is candida intertrigo seen and why

A

intertrigo (in skin folds)- under breasts, groin areas, abdo folds, nappy areas

89
Q

how do you treat candida intertrigo

A

clotrimazole cream, oral fluconazole

90
Q

what bug causes scabies

A

sarcoptes scabiei

91
Q

what is norwegian scabies

A

chronic crusted form of scabies

92
Q

where does scabies affect

A

finger webs, wrists, genital area

93
Q

how do you treat scabies

A

malathion lotion applied overnight to whole body and washed off next day
benzyl benzoate

94
Q

what are pediculosis

A

lice
capitis- head
corporis- body

95
Q

what is phthirus pubis

A

pubic louse

96
Q

what is the treatment for lice

A

malathion

97
Q

why are gram positive organisms a worry for infection control

A

can survive in environment because of cell wall structure

98
Q

what skin conditions require single room isolation for infection control

A

group a strep infection
MRSA infection
scabies (long sleeve gown for norwegian)

99
Q

what organisms causes athletes foot

A

trichophyton rubrum

100
Q

what is the treatment for tineae pedis

A 
oral terinafine (if nails involved)
topical clotrimazole (if just skin)
101
Q

what two organisms cause impetigo

A

staph aureus and strep pyrogenes

102
Q

how do you treat strep pyogenes impetigo

A

oral penicillin

103
Q

what extra infection control precautions for a child with impetigo

A

droplet and contact precautions

104
Q

what bacterial can cause infection from cat and dog bites

A

pasturella multocida- gram negative bacilli

105
Q

what are the presenting features of rabies

A

viral encephalitis- fever, altered mental state

106
Q

what is the treatment for rabies

A

post exposure vaccination, hyperimmune globulin

107
Q

how can you get rabies in UK

A

bite from UK bat

108
Q

is rabies a virus or bacteria

A

virus

109
Q

dermatophyte infections can be treated with which two drugs when small areas or skin and nails are implicated

A

clotrimazole (cream)

amorolfine (nail paint)

110
Q

how can candida intertrigo be treated (3)

A

clotrimazole cream

nystatin (oral/topical)

oral fluconazole

111
Q

in a diabetic patient with a severe leg ulcer, what antibiotic could be given for anaerobic cover

A

metronidazole

112
Q

what class of haemolytic strep is S. pneumoniae

A

alpha

113
Q

what class of haemolytic strep is S. agalactiae

A

alpha

114
Q

what class of haemolytic strep is S. pyogenes

A

beta

115
Q

what class of haemolytic strep is S. viridans

A

alpha

116
Q

what class of haemolytic strep are bowel commensals

A

trick question= non- haemolytic

117
Q

what bacteria commonly causes UTIs in women of child bearing age

A

atpah, saprophyticus (young sexually active girls)

118
Q

what are the two types of NF

A

type 1- caused by aerobic/ anaerobic bac (usually after surgery)

type 2- associated with group A strep arises spontaneously in healthy individuals

119
Q

what is nokilskys sign

A

when slight rubbing causes exfoliation of the outermost layer (seen in staph scaled skin syndrome)

120
Q

what is the most common causative organism of tinea fungal infections

A

trichophytom rubrum

121
Q

what organisms causes golden crusting on infections

A

S, aureus

122
Q

which antibiotics can be used to treat step. pyogenes

A

flucloxicillin or penicllin

123
Q

what bacteria sauses SSSS

A

staph aureus

124
Q

what class of beta haemolytic strep is associated with neonatal menigitis

A

B

125
Q

would a patient with group A strep infection need isolation

A

no

126
Q

what investigations are best for dermatophyte infections

A

woods light (fluorescence), skin scrapings, nail clippings or hair sampling fro culturing

127
Q

how would an infection with scabies be treated

A

benzyl benzoate

128
Q

what bacteria causes acne of the upper arm and armpit

A

propionobacterium

129
Q

is staph epidermis coagulase positive or negative

A

negative

130
Q

what bacteria causes sphillis

A

treponema pallidum

Dermatology (23 decks)

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