Infections and Infestations

Question 1

What is the pathogenesis of the herpes simplex virus?

Answer 1

Infection becomes latent after primary exposure - with or without a clinical episode

After infeciton is latent a trigger causes a clinical episode (trauma, menstruation, sunlight, fever)

The first clinical episode is likely to be the most severe

Question 2

Where does the herpes simplex virus reside?

Answer 2

Usually resides in the dorsal root ganglion after travelling up the peripheral nerves

Question 3

Who is likely to suffer from worse cinical episodes from the herpes simplex virus?

Answer 3

The immunosuppressed

Those with atopic eczema

Question 4

What is the pathogenesis of the herpes zoster virus?

Answer 4

Primary exposure

Chicken pox

Latent infection

Reactivation

Shingles

(pain / constitutional symptoms)

about 4 days after - rash

The rash usually tracks around the body - however it does not cross the midline of the body

Question 5

What are the common infective agents of the skin?

Answer 5

Staph aureus and strep

Question 6

Desribe the depth of infection of impetigo

Answer 6

Very superficial

Question 7

What is a furuncle?

Answer 7

Abscess in a hair follicle

Question 8

What is a carbuncle?

Answer 8

Several furuncles joined together

Question 9

Define erysipelas

Answer 9

an acute, sometimes recurrent disease caused by a bacterial infection, characterized by large raised red patches on the skin.

More superficial than cellulitis

Caused by strep

Skin is raised and inflamed over infected area

Question 10

What is the causative organism for cellulitis?

Answer 10

Staph

Question 11

What does impetigo look like on dry skin?

Answer 11

Golden and crusten, although it does look slightly different over a moist area (e.g underneath the armpit)

Very contagous

The causative organism os usually staph - however it may be strep (20%) sometimes a mixture of both

Question 12

Who is more susceptible to rcurrent furuncles?

Answer 12

People with diabetes

Question 13

What is ecthyma?

Answer 13

Ecthyma is a variation of impetigo, presenting at a deeper level of tissue. It is usually associated with Group A (beta-hemolytic) Streptococcus (abbreviated GAS).

Question 14

Where is cellulitis common?

Answer 14

Lower limb - below the knee

Question 15

What are the symptoms of cellulitis?

Answer 15

Tender and hot

If the infection is extensive then fever as well

Question 16

What is the most common yeast infection?

Answer 16

Candida albicans- grows on moist areas

(obese people who are unable to wash well)

Question 17

What does candida albicans look like?

Answer 17

Brick red erythema

Satellite pustules

(commonly foound underneath the breasts or inbetween the fingers of people who have a lot of wetness on their hands - occupation related)

Question 18

What is paronychia?

Answer 18

Inflammation of the folds of tissue surrounding the nail due to infection or inflammation. The infection may be bacterial (most commonly, staph or strep) or fungal pathogens.

Most common infective agent is candida

Question 19

What does athletes foot look like?

(tinea pedis)

Answer 19

Lots of white lacerated skin - flaky bits around the edge

Question 20

What are the fungi responsible for athletes foot?

Answer 20

Usually caused by dermatophyte fungi

Question 21

What are the best agents to treat tinea pedis (dermatophyte fungi)?

Answer 21

Clotrimazole or terbinafine

Question 22

What is the name given to athletes foot but on the body?

Answer 22

Tinea corporis

Question 23

What is the relevant investigation for tinea infections?

Answer 23

Scrapings are sent to the lab for culture

Question 24

What is the name of athletes foot in the crotch area?

Answer 24

Tinea cruris

Question 25

What happens when you use topical steroids on tinea?

Answer 25

Loss of scaly appearance

(tinea incognita)

Question 26

What is tinea barbay?

Answer 26

Tinea barbae: A fungal infection (known as ringworm) of the bearded area of the face and neck, with swelling and marked crusting, often with itching. In the days when men went to the barber daily for a shave, tinea barbae was called barber’s itch.

Question 27

How does kerion develop?

Answer 27

Kerion is the result of the host’s response to a fungal ringworm infection of the hair follicles of the scalp (occasionally the beard) that can be accompanied by secondary bacterial infection(s). It usually appears as raised, spongy lesions, and typically occurs in children

Question 28

What causes the itching in scabies?

Answer 28

A protein in mite droppings

Question 29

What is the main symptoms in scabies?

Answer 29

Itching

Question 30

Where does scabies normally infect?

Answer 30

Colder areas (extremities like the hands and even the scrotum)

Question 31

How is scabies spread?

Answer 31

Long skin-skin contact (about a minute)

Question 32

What causes the rash associated with scabies, describe the rash

Answer 32

Allergic rash is usually on the sides of the torso – lesions here do not have mites – they are the allergic manifestation of the mites

Question 33

How do we treat scabies?

Answer 33

Treatment is cream – taken and then taken again 7 days later (eggs)

The itch may reside slightly longer

Need to treat close contacts simultaneously

There is a stigma about scabies - assocaited with being filthy – but this is not true

Overtreatment may cause eczema