Microbiology 4: Skin infections

Question 1

WHat % of GP consultations in the UK are skin-related?

Answer 1

15%

Question 2

In which climates are skin conditions most prevalent?

Answer 2

Hot and humid

Question 3

Which pathogen is responsible for tinea infections

Answer 3

Tricophytum rubrum

Question 4

What sort of infection is caused by tricophytum rubrum?

Answer 4

Tinea

Question 5

What sort of pathogen is trycophytum rubrum?

Answer 5

Fungus

Question 6

Give 3 examples of tinea infections

Answer 6

Tinea capitis
Tinea ungulum
Tinea manu (“ringworm”)

Question 7

Which pathogen is responsible for causing scabies?

Answer 7

Sarcoptes scabei

Question 8

Recall the pathophysiology of a scabies infection

Answer 8

Sarcoptes scabei burrows into the infected epidermis to cause a Type IV DTH reaction

Question 9

Give 3 common sites for scabies burrows

Answer 9

Groin
Axilla
Anticubital fossae

Question 10

Recall the main symptom of a scabies infection and how long the latent period is before symptoms are seen

Answer 10

Widespread erythrematous rash

4 week latent period

Question 11

What classification of bacterium is S aureus?

Answer 11

G+ coccus

Question 12

Recall the 4 toxins produced by S aureus

Answer 12

PVL
Exfoliative toxin
TSS1
Enterotoxin

Question 13

What is the result of PVL production by S aureus?

Answer 13

Causes necrotising infection

Question 14

What is the result of exfoliative toxin production by S aureus?

Answer 14

Blisters

Question 15

Recall 3 symptoms of S aureus infection?

Answer 15

Skin infection
Severe pneumonia
Sepsis

Question 16

What is impetigo?

Answer 16

An S aureus infection of the subcorneal layer of the epidermis

Question 17

Recall the appearance of imeptigo

Answer 17

Yellowish with golden crust, eroded base

Question 18

In what subset of the population is bullous impetigo most common?

Answer 18

Neonates

Question 19

What is ecythema?

Answer 19

Full thickness involvement of the epidermis in an S aureus infection

Question 20

What is the result of exfoliative-toxin productioon by S aureus?

Answer 20

Staphlococcal Scalded skin Syndrome

Question 21

Recall the pathophysiology of staphylococcal scalded skin syndrome

Answer 21

S aureus releases exfoliative toxin into the bloodstream at wound site
–> systemic infection –> widespread erythema

Question 22

Differentiate SSSS and toxic epidermal necrolitis

Answer 22

SSSS does not infect the mucous membranes but TEN does

Question 23

What sort of pathogen is treponema pallidum?

Answer 23

G- bacterium

Question 24

What is syphillis caused by?

Answer 24

Treponema pallidum

Question 25

Recall the duration of each of the phases of syphillis infection

Answer 25

``` Primary = 3-8 weeks Secondary = 6-12 weeks Tertiary = years later ```

Question 26

Recall the main symptoms of the primary phase of syphillis

Answer 26

Chancre (painless ulcer) in genital/ oral area

Question 27

Recall the symptoms of secondary syphillis

Answer 27

Generalised rash, lymphadenopathy and flu-like illness

Question 28

Describe the rash of secondary syphillis

Answer 28

Maculopapular and erythrematous

Question 29

Which body systems are affected by tertiary syphillis?

Answer 29

Skin CNS PNS CVS

Question 30

What is the first-line treatment for congenital syphillis?

Answer 30

Penicillin

Question 31

Recall which serotypes of HHV are known as EBV, VZV and CMV

Answer 31

``` EBV = HHV4 VZV = HHV3 CMV = HHV5 ```

Question 32

Recall which types of HSV cause oral and genital herpes

Answer 32

``` Oral = type 1 Genital = type 2 ```

Question 33

Which cells are infected in an HSV infection?

Answer 33

Neurons

Question 34

Which pathogen commonly infects at defective skin barriers due to eczema?

Answer 34

HSV --> eczema herpeticum

Question 35

What disease is produced by herpes spreading to the brain?

Answer 35

Herpes encephalitis

Question 36

Which serotype of HHV is associated with Kaposi's sarcoma?

Answer 36

HHV8

Question 37

Where does VZV have latency?

Answer 37

Dorsal root ganglia

Question 38

Recall a virus that can cause non-cardiac chest pain

Answer 38

VZV when it is reactivated in shingles

Question 39

How does treatment of VZV differ in shingles that does/ does not affect CNV?

Answer 39

When CNV is infected you get face involvement so acyclovir is given IV rather than orally so as to avoid blindess