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Microbiology Flashcards

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Dermatology Board Prep flashcards
1
Q

What is virulence?

A

the capacity of a microbe to cause damage to the host

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2
Q

What are virulence ffactors?

A

The factors responsible for the variation in virulence within and between species

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3
Q

What is adhesin?

A

enables binding of the organism to host tissue

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4
Q

What is invasin

A

enabled the organism to invade a host cell/tissue

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5
Q

what is impedin?

A

enables the organims to avoid host defense mechanisms

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6
Q

What is aggressin?

A

causes damage to the host directly

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7
Q

What is modulin?

A

induces damage to the host indirectly

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8
Q

Where is S.aureus found on the body?

A

anterior nares and perineum

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9
Q

What skin diesases can Staph. aureus cause?

A

rash; folliculitis; carbuncle; impetigo; abscess; scalded skin syndrome

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10
Q

What do adhesins bind to?

A

extracellular matrix molecules that are present on cell surfaces

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11
Q

Give 2 examples of adhesins?

A

fibrinogen-binding

collagen-binding

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12
Q

What disease does collagen-binding factor allow Staph. aureus to cause?

A

osteomyelitis

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13
Q

Do all Staph. aureus have all virulence factors?

A

No

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14
Q

What is the purpose of hte capsule?

A

a thick polysaccharide layer that allows bacteria to evade and hide from the immune system

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15
Q

What is a toxinoses?

A

It is a disease that isn’t caused by the bacteria itself but by the toxin it produces

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16
Q

What is a superantigen?

A

Doesn’t bind directly to MHC class 2 complex but binds outside conventional binding groove which causes a cytokine storm and inappropriate immune response

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17
Q

Give an example of a superantigen

A

TSST-1

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18
Q

What disease does TSST-1 cause?

A

Toxic Shock Syndrome

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19
Q

What are the symptoms of Toxic Shock Syndrome?

A

fever
diffuse macular rash and desquamation
hypotension
more than three organs involved

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20
Q

What does Panton- Valentine Leukocidin do?

A

specific toxicity for leukocytes so stop immune system working

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21
Q

What conditions is PVL associated with?

A

recurrent furunculosis
sepsis/ necrotising fasciitis
necrotising pneumonia

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22
Q

Why do antibiotics fail in the treatment of necrotising penumonia?

A

The toxin is causing the disease not the bacteria and the antibitocs do not target the toxin

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23
Q

Describe Streptococci

A

gram positive cocci
chains
coagulase negative

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24
Q

What skin infections does streptococcus pyogenes cause?

A

impetigo, cellulitis, necrotising fasciitis

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25
Q

If a microbe causes beta haemolysis, what does this mean the bacteria can do?

A

produce a protein that can destroy RBCs

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26
Q

What proteins are involved in helping Strep. pyogenes in adhesion?

A

M proteins

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27
Q

What superantigens cause Toxic shock like syndrome?

A

SpeB and SpeC

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28
Q

What allows both Staph. aureus and Strep. pyogenes to cause Toxic Shock?

A

Similar exo-proteins, common virulence factors and disease mechanisms

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29
Q

What is variation in disease and virulence the result of?

A

variation in genes

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30
Q

How do staphylococcus sp. appear on staining

A

gram positive cocci in clusters

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31
Q

How are staphylococcus differentiated?

A

coagulase test

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32
Q

Name an important coag negative staph.?

A

staph. epidermidis

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33
Q

What is the only coagulase positive staph.?

A

staph. aureus

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34
Q

Name 3 toxins produced by staph. aureus?

A

enterotoxin; SSSST; PVL

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35
Q

How do streptococcus sp. appear on gram staining?

A

gram positive cocci in chain

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36
Q

How are strep. sp. classified?

A

haemolysis

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37
Q

Name 2 bacterium that are alpha haemolytic strep.?

A

strep. pneumoniae and strep. viridans

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38
Q

What are the bacteria that are beta-haemolytic?

A

Group A, group B and group C, G

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39
Q

What bacteria is non-haemolytic?

A

enterococcus

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40
Q

how does partial haemolysis appear on a petri dish?

A

green

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41
Q

What enzyme do beta-haemolytic streptococci produce?

A

haemolysin

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42
Q

What is the purpose of having a dry skin surface?

A

dessication (drying out) of microbes

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43
Q

What is the purpose of sebum?

A

inhibit bacterial growth

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44
Q

What skin infections does staph. aureus cause?

A 
boils and carbuncles
cellulitis
infected eczema
impetigo
wound infection
staph. scalded skin syndrom
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45
Q

What skin infections does strep. pyogenes cause?

A 
infected eczema
impetigo
ceullitis
erysipelas (superficial form of cellulitis- raised red patches)
nectrotising fasciitis
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46
Q

What antibiotic is given for strep. pyogenes?

A

penicillin

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47
Q

What is necrotising fasciitis?

A

bacterial infection spreading along fascial planes below skin surface leading to rapid skin destruction

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48
Q

What are the 2 types of nectrotising fasciitis?

A

type 1- mixed

type 2-group A strep

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49
Q

Where is tinea capitis found?

A

scalp

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50
Q

Where is tinea barbae found?

A

beard

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51
Q

where is tinea corporis found?

A

body

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52
Q

Where is tinea manuum found?

A

hand

53
Q

Where is tinea unguium found?

A

nails

54
Q

Where is tinea cruris found?

A

skin folds- groin; under the arm; under the breast

55
Q

What other name is tinea pedis known as?

A

athletes foot

56
Q

What type of tissue do dermatophytes infect?

A

keratinised tissues only-skin, hair and nails

57
Q

what gives a dermatophyte infection its ring appearnace?

A

lesion grows outward and heals in the centre

58
Q

What type of skin does fungus enter?

A

abraded or soggy skin

59
Q

What is the most common dermatophyte causal organism?

A

trichophyton rubrum

60
Q

What type of light can be used to diagnose fungal infections?

A

Woods light (fluroescence)

61
Q

What is the name of the anti-fungal cream given?

A

clotrimazole

62
Q

What systemic anti-fungal angents can be given?

A

terbinafine

itraconazole

63
Q

Where does candida cause skin infections?

A

in skin folds where area is warm and moist (candida intertrigo)

64
Q

How are candida skin infections treated?

A

clotrimazole cream; oral fluconazole

65
Q

What is scabies caused by?

A

sarcoptes scabiei

66
Q

What is the norwegian scabies?

A

chronic crusted form which is highly infectious

67
Q

What are the symptoms of scabies?

A

intensely itchy rash affecting finer webs, wrists and genital area

68
Q

What is the treatment for scabies?

A

malathion lotion

benzyl benzoate

69
Q

What is the treatment for lice (pediculosis)?

A

malathion

70
Q

What patients need single room isolation and contact precautions?

A

Group A strep infections
MRSA infection
Scabies (long sleeved g owns also required for norwegian scabies)

71
Q

What virus causes chickenpox and shingles?

A

varicella zoster virus

72
Q

What happens during chickenpox that allows the virus to reactivate as shingles?

A

Virus establishes latency in dorsal root ganglia

73
Q

What is the progression of the rash found in chickenpox?

A

macules to papules to vesicles to scabs to recovery (centripetal-thickest on torso)

74
Q

What is associated with chickenpox in addition to the rash?

A

fever and itch

75
Q

What are the complications of chickenpox?

A 
secondary bacterial 
pneumonitis
haemorrhagic
scarring
encephalitis
76
Q

What factors would predict chickenpox to be severe?

A

extremes of age; depressed cell mediated immunity

77
Q

What does neonatal VZV happen secondary to?

A

chickenpox in mother in late pregnancy

78
Q

How is neonatal VZV prevented?

A

varicella zoster immune globulin in susceptible women

79
Q

What is the rash progression in shingles?

A

tingling/pain to erythema to vesicles to crusts

80
Q

What is a compication of shingles?

A

post-herpetic neuralgia

81
Q

What increases the chances of getting post-herpetic neuralgia?

A

eldery

trigeminal distribution

82
Q

Why is an opthalmogy referral required urgently if zoster affects the trigeminal nerve?

A

Shingles can cause keratitis- inflammation of the cornea

83
Q

What is Ramsay-Hunt Syndrome?

A

When shingles affects CN7 and so causes vesicles and pain in the auditory canal and throat. Also causes facial palsy and if there is irritation of the 8th cranial nerve- deafness; vertigo and tinnitus

84
Q

What is Ramsay-Hunt syndrome also known as?

A

geniculate or otic herpes zoster

85
Q

Why is a vaccination for shingles given?

A

reduces incidence of shingles as well as post-herpetic neuralgia

86
Q

What is happens during the first infection of herpes simplex?

A

gingivostomatitis

87
Q

What are the symptoms of herpes simplex virus?

A

recurrent blistering rash at vermillion border

88
Q

Where can herpes simplex spread to in the body?

A

fingers- herpetic whitlow

eczema- eczema herpeticum

89
Q

Which type of herpes simplex mainly causes oral lesions

A

HSV type 1

90
Q

How does aciclovir work?

A

An analogue of guanosine and so is selectively incorporated into viral DNA inhibiting replication

91
Q

What is the drawback of aciclovir?

A

Does not eliminate latent virus

92
Q

What infections can cause erythema multiforme?

A

herpes simplex virus

mycoplasma pneumoniae bacterium

93
Q

What is molluscum contagiosum?

A

fleshy, firm umbilicated pearlescent nodules which are self limiting and common in children

94
Q

How can molluscum contagiosum be treated?

A

liquid nitrogen

95
Q

What virus causes warts?

A

HPV

96
Q

How can warts be treated?

A

topical salicyclic acid

97
Q

What age are warts most common?

A

children

98
Q

What types of HPV are most common in warts/verrucas?

A

types 1-4

99
Q

What types of HPV cause genital warts?

A

types 6 and 11

100
Q

Which types of HPV cause cervical cancer?

A

types 16 and 18

101
Q

What is herpangina?

A

blistering rash at the back of the mouth

102
Q

What viruses cause herpangina?

A

enterovirus- coxsackie virus and echovirus

103
Q

How can herpangina be treated?

A

usually self-limiting

104
Q

What viruses cause hand, foot and mouth disease?

A

enteroviruses- esp. coxsackie

105
Q

What age group typically gets hand, foot and mouth disease?

A

children

106
Q

What virus causes erythema infectiosum?

A

human parovirus

107
Q

What is the common name for erythema infectiosum?

A

slapped cheek disease

108
Q

What are the symptoms of erythema infectiosum?

A

slapped cheek appearance which as it fades becomes a lacy macular rash on the body. headache; fever; arthralgias; sore throat

109
Q

What is especially seen in adults with erythema infectiosum?

A

acute arthritis esp. in the wrists as the rash fades

110
Q

What are the complications of parovirus?

A

spontaneous abortion
aplastic crises (sudden drop in haemoglobin)
chronic anaemia

111
Q

How is parovirus diagnosed?

A

antibody testing - IgM

112
Q

What is Orf?

A

virus of sheep “scabby mouth”

113
Q

How does Orf present?

A

firm, fleshy nodule on hands of farmers

114
Q

What is the first phase of a syphilis infection?

A

chancre- painless ulcers at site of entry

115
Q

What is the secondary phase of syphilis infection?

A

red rash over body- which is prominent on soles of feet and palms of hands
mucous membrane- “snail track” ulcers

116
Q

What is the tertiary phase of syphilis infection?

A

CNS; CVS; gummatous

117
Q

What is syphilis caused by

A

bacterium- treponema pallidum

118
Q

How is syphilis diagnosed?

A

blood test or swab of chancre for PCR

119
Q

How is syphilis treated?

A

injections of penicillin

120
Q

What is the vector in Lyme disease?

A

ticks

121
Q

What bacterium causese Lyme disease?

A

Borrelia burgdorferi

122
Q

What is the early presentation of Lyme disease?

A

erythema migrans

123
Q

What is the late presentation of Lyme disease?

A

heart block; nerve palsies; arthritis

124
Q

What is the therapy for Lyme disease?

A

amoxicillin or doxycycline

125
Q

What is the lab confirmation for Lyme disease?

A

antibody blood test (mainly for late presentations)

126
Q

What are the symptoms of Zika virus?

A

fever; rash (maculopapular); headaches; arthralgia; myalgia; non-purulent conjuctivitis

127
Q

What is the vector for Zika virus?

A

mosquito

128
Q

What are the complications of Zika virus?

A

microcephaly and guillain barre syndrome

Dermatology (15 decks)

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