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Microbiology Flashcards

1
Q

Name five virulence factors

A
  • adhesin
  • invasin
  • impedin
  • aggressin
  • modulin
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2
Q

What does adhesin do?

A

Enables binding of the organism to host tissue

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3
Q

What does invasin do?

A

Enables the organism to invade a host cell/tissue

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4
Q

What does impedin do?

A

Enables the organism to avoid host defence mechanisms

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5
Q

What does aggressin do?

A

Causes damage to the host directly

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6
Q

What does modulin do?

A

Induces damage to the host indirectly

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7
Q

State the name for hospital acquired

A

Nosocomial

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8
Q

What skin conditions can staph aureus cause?

A
  • folliculitis
  • carbuncle (boils)
  • abscess
  • impetigo
  • scalded skin syndrome
  • toxic shock syndrome
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9
Q

State the virulence factors of staph aureus

A
  • adhesin (collagen & fibrinogen binding protein)
  • coagulase positive (clots plasma)
  • PVL (leukocidin - kills leukocytes)
  • TSST-1 (shock, rash, desquamation)
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10
Q

Describe how toxic shock syndrome arises

A

Superantigen TSST1 activates 1 in 5 T cells causing a massive release of cytokines & inappropriate immune response

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11
Q

What are the signs and symptoms of toxic shock syndrome?

A

Diffuse macular erythroderma
Hypotension
>/= three organ systems involved
Also includes high fever, vomiting, diarrhoea, sore throat, muscle pain

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12
Q

How does scaled skin syndrome arise?

A

Toxins produced by specific types of staph aureus cause disruption of epidermal keratinocyte adhesion causing blistering, desquamation and re-epithelialisation

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13
Q

What are the signs and symptoms of SSS?

A

Pyrexia, tender erythema, superficial blisters that are easy to burst, bulls impetigo (skin looks burnt).

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14
Q

Why are young children mainly affected by SSS?

A

As they have underdeveloped immune systems & kidneys

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15
Q

How is SSS diagnosed?

A

Swab

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16
Q

What does PVL stand for?

A

Panton Valentine Leukocidin

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17
Q

Describe the mechanism of action of PVL

A

Toxin that can kill white blood cells & cause damage to skin and deeper tissue

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18
Q

What are the five C’s of PVL?

A 
Close contact 
Contaminated items 
Crowding 
Cleanliness
Cuts
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19
Q

How can PVL present?

A

Recurrent and painful boils/red areas of skin that don’t get better with antibiotics

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20
Q

How is PVL diagnosed?

A

Swab

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21
Q

What happens if PVL is combined with other toxins e.g MRSA or alpha toxin?

A

Necrotising pneumonia

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22
Q

What is the most common type of group A strep?

A

Strep pyogenes - most GAS come under this name however there are some other GAS strains

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23
Q

How can strep pyogenes be identified?

A

Beta haemolysis & by lancefield system

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24
Q

What is the lancefield system?

A

Serotyping cell wall carbohydrate of change in M protein

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25
What conditions can GAS cause?
- impetigo - cellulitis - erysipelas - necrotising fascitis - infected eczema
26
Describe the presentation of impetigo
Red, sore, itchy skin with pus filled blisters on hands and face which pop to leave brown crusty patches
27
What is cellulitis?
Infection of the dermis that is not associated with necrosis
28
What is erysipelas?
Infection of the upper dermis & superficial lymphatics
29
How will cellulitis and erysipelas present?
Cellulitis - lower leg (ill defined edge) Erysipelas - legs and face (sharp edge) Pyrexia, shivers, sore, swollen, erythema, blisters, enlarged lymph nodes.
30
What causes necrotising fasciitis?
invasive GAS
31
Describe necrotising fasciitis
Penetration of mucous membrane causes a lesion and bacteria rapidly destroys the connective tissue
32
Name the symptoms of necrotising fasciitis
Severe pain, fever, purple coloured skin, abscess, vomiting Necrosis - bullae, bleeding into the skin, reduced sensation, shock. Spreads along facial planes - life threatening disease
33
State four virulence factors of invasive GAS responsible for necrotising fasciitis
- haemolysin - superantigen - streptolysin - capsule
34
How is intact skin able to fight infection?
- dry (desiccation of micro-organisms) - sebum (inhibit bacterial growth) - competitive flora
35
How do you treat staph aureus & MRSA?
Flucloxacillin | MRSA - doxycycline, co-trimoxazole, clindamycin, vancomycin
36
What are the three strains of strep with examples?
alpha - pneumonia and viridian's beta - GAS & GBS (meningitis in neonates) none - enterococcus (bowel commensal & UTIs)
37
How do you treat streptococcus infections?
Penicillin but flucloxacillin will kill both staph and strep
38
What in ringworm commonly known as?
Tinea
39
Where can tinea occur and what is it called in each place?
``` scalp - capitis beard - barbae body - corporis hand - manuum nails - unguinm groin - cruris foot - pedis ```
40
What is tinea pedis commonly known as?
Athletes Foot
41
What is the name of fungi that require keratin to grow?`
Dermatophyte
42
Describe the pathogenesis of ringworm
1. Fungus enters abraded/soggy skin 2. Hyphae spread in stratum corneum 3. Infects keratinised tissue 4. Increases epidermal turnover (scaling) 5. Inflammatory response 6. Invades hair follicles & shafts 7. Lesion grows outwards but heals in the centre
43
How is tinea transmitted?
Infected humans, animals, soil
44
How is tinea diagnosed?
Appearance, woods light, skin scrapings around edge of lesion
45
What is the treatment for tinea?
Small areas/nails - clotrimazole cream or amorolfine nail pain Extensive skin/nail/scalp - oral terbinafine or itraconazole
46
How is candida treated?
Clotrimazole (cream or pessary) | Fluconazole (oral)
47
What parasites can cause skin conditions?
Scabies | Lice
48
Describe scabies
Highly infectious, mites spread through skin to skin contact - main symptom is an itch (worse at night) and they may develop a rash (similar to eczema)
49
How is scabies treated?
``` Malathion lotion Benzyl benzoate (not in children) ```
50
Where can lice be found?
Head, body, pubic hair - present with severe itch and visible lice and eggs
51
How is head lice commonly treated?
Malathion lotion
52
What causes chickenpox and shingles?
Varicella Zoster virus
53
Describe chickenpox
Primary infection typically occurs in childhood effects sensory nerve roots and causes generalised rash and fever
54
What is the pathway of a chickenpox rash?
macule - papule - vesicle - scab - recovery
55
What are the complications of chickenpox?
secondary bacterial pneumonitis, scarring, encephalitis, haemorrhagic rash
56
Which groups of patients are at increased risk if they catch chickenpox?
Immunocompromised | Pregnant women
57
Why are pregnant women at increased risk?
Neonatal VZV is secondary to chickenpox in a mother in late pregnancy
58
How is VZV prevented in pregnant women?
Immune globulin or aciclovir
59
Describe shingles
Caused by zoster/herpes zoster it presents with dermatomal distribution due to reactivation of the virus. Increased incidence in elderly & immunocompromised tingling - erythema - vesicles - crusts
60
What is a serious type of shingles?
Ophthalmic zoster - need urgent ophthalmology referral - can happen in children due to chicken pox in utero
61
What is Ramsay Hunt Syndrome Type 2?
Reactivation of heres zoster in the geniculate ganglion (sensory fascial nerves)- also known as herpes zoster otic
62
How does Ramsay Hunt Type 2 present?
Vesicles & pain in the auditory canal & throat, fascial palsy (7th nerve palsy) & irritation of 8th cranial nerve (deafness, vertigo, tinnitus)
63
What is the treatment for Ramsay Hunt Syndrome Type 2?
Prednisolone & aciclovir
64
Describe Herpes Simplex virus
Gingivostomatitis common in pre school children - extensive ulceration in and around the mouth - heals without scarring
65
When does herpes simplex become an emergency?
If it spreads to eczema
66
What is the difference between type 1 and type 2 herpes simplex virus?
Type 1 - mainly oral lesions, 50% genital | Type 2 - rarely oral lesions, encephalitis/disseminated infection can occur in neonates
67
What can herpes simplex virus provoke?
Erythema multiforme
68
How can recurrent herpes simplex virus be treated if recurrent?
3-6 months of aciclovir
69
Describer molluscum contagiosum
Fleshy firm umbilicate pearlescent nodules usually asymptomatic but can be itchy. They are fairly self limiting and may take months to go away.
70
What causes warts?
HPV
71
How can warts be treated?
Topical salicylic acid
72
What is herpangina?
Blistering rash on back of mouth caused by enterovirus
73
What are the three causes of herpangina?
- Hand/Foot/Mouth Disease - Coxsackie virus - Echovirus
74
Who usually presents with hand/foot/mouth disease?
Children, often family outbreaks
75
How is herpangina diagnosed/treated?
Swab/stool sample is required, condition is self limiting
76
What is erythema infectiosum?
Contagious viral infection that causes a blotchy or raised red rash with mild illness
77
What causes erythema infectiosum?
Parvovirus B19 (slap cheek disease)
78
How does parvovirus B19 present?
Bright red rash on cheeks, mild systemic illness, acute polyarthritis of the small joints may be more common in adult patients
79
What are the complications of parvovirus B19?
- spontaneous abortion - aplastic crises (sudden drop in haemoglobin) - chronic anaemia
80
Describe Orf
Virus of sheep - nodules found on farmers hand, Self limiting
81
Describe the difference between primary, secondary and tertiary syphilis
Primary - chancre (painless ulcer at site of entry) Secondary - red rash on soles of feet & palms, snail track ulcers on mucous membrane Tertiary - CNS, cardiovascular, gummatous necrosis
82
What causes syphilis?
STI - treponema pallidum bacteria
83
How is syphilis diagnosed and treated?
Blood test or swab for diagnosis | Treated using injections of penicillin

Dermatology (13 decks)

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