Infections of the Skin

Question 1

Explain the role of microbiota in and on the body

Answer 1

Offers protection by competing with pathogens for colonisation sites.
Some produce antibiotic substances which suppresses the growth of competing organisms. Some produce toxins to inhibit other micro-organisms

Question 2

Describe how skin acts as a defence barrier

Answer 2

It has an acidic pH which makes it uninhabitable, it also secretes sweat and produces antimicrobial substances such as fatty acids, sebum and defensins

Question 3

Name two examples of normal skin microbiota

Answer 3

Coagulase-negative staphylococci (epidermidis and aureus)

Question 4

Where can skin infections occur and give an example

Answer 4

Keratinised epithelium - ringworm
Epidermis - Impetigo
Hair follicles - folliculitis
Subcutaneous fat - cellulitis
Fascia - necrotising fasciitits 
Muscle - gas gangrene

Question 5

Describe routes of infection

Answer 5

Skin - pores and hair follicles
Wounds - scratches, cuts and burns
Bites - Insect and Animal.

Question 6

Describe some of the features of streptococcus Pyogenes

Answer 6

Gram positive cocci that grows in chains.

Its a group A, beta-haemolytic (makes it very dangerous)

Question 7

Define haemolytic

Answer 7

Involving the rupture or destroying of red blood cells.

Question 8

Describe some features of Staphylococcus aureus

Answer 8

Gram -positive cocci
Resistant to methicillin and vancomysin,
Causes a wide range of illnesses

Question 9

Describe some of the features of Pseudomonas Aeruginosa

Answer 9

Coccobacillus (between cocci and bacilli) shaped, gram negative.
Monotrichous flagellum.
Opportunistic bacteria so will colonise in catheters ect.

Question 10

Describe the different forms of skin lesions and how they appear

Answer 10

Macule - Flat and red, local inflammation
Papule - Raised and red, more marked inflammation
Vesicle - small blister
Ulcer - Disruption of epithelium

Question 11

Define Abscess

Answer 11

Collection of pus

Question 12

Define Cutaneous vesicle

Answer 12

Blister - fluid filled sac

Question 13

Define Impetigo

Answer 13

Vesicles developing and rupturing into pustules then form dried crusts

Question 14

Define Ecthyma

Answer 14

Ruptures vesicles that lead to erythematous (redness of mucosa membrane) lesions

Question 15

Folliculitis

Answer 15

Inflammation of hair follicle.

Question 16

Define Furuncle

Answer 16

Deep folliculitis boil

Question 17

Define Carbuncle

Answer 17

Collection of boils

Question 18

Define cellulitis

Answer 18

Erythematous inflammation affecting deeper dermis and subcutaneous tissue

Question 19

Define Acne

Answer 19

Infection of sebaceous follicles

Question 20

Define necrotising fasciitis

Answer 20

Cellulitis with necrosis affecting skin, deep fascia and sometimes muscle

Question 21

Define Dehiscence

Answer 21

Wound rupture along surgical site

Question 22

Name some fungal infections of the skin

Answer 22

Dermatophytes caused by tinea spp (e.g. tinea pedis)

Yeast infections caused my candida albicans and malassezia furfur.

Question 23

Name some viral infections of the skin

Answer 23

Human papilloma virus (HPV) - warts and genital warts.
Herpes simplex virus 1 - cold sores
Herpes simplex 2 - genital herpes
Varicella Zoster Virus - chicken pox and shingles
Coxsackie A virus - hand, foot and mouth disease

Question 24

Name and describe a parasitic infection of the skin

Answer 24

Sarcoptes scabei (mites) causes scabies.
Mites burrow into the skin and the females lay eggs. It may lead to superinfection