Bacterial Skin Infections

Question 1

Function of the skin

Answer 1

Protective barrier against micro-organisms, chemicals, radiation, temperature changes

Question 2

Characteristics of the skin

Answer 2

Keratinised stratified epithelium

pH 4-6

Gram negative bacteria live in moist regions (underarm - apocrine glands)

Halophiles favour as high salt concentration

Resident microbiota is S.aureus, S.epidermis, P.acnes, Corynebacterium

Question 3

Skin infections ranked least to most important

Answer 3

1. Infections of hair follicles/glands
2. Infections through minor lesions
3. Ulcers/burns
4. Infections of other skin layers

Question 4

Folliculitis

Answer 4

Minor skin infection of the hair follicles, caused by S.aureus, Pseudomonas aeruginosa, C.albicans.

Furuncles - small abscesses
Carbuncles - combination of furuncles creating bigger deeper wounds spread through different skin layers

Question 5

Acne

Answer 5

Propionibacterium acnes
Gram positive bacilli

P.acnes colonises sebum which is converted to free fatty acids. An inflammatory response occurs to this, and oleic acids are produced which kill Gram negative bacteria on the skin.

Treatment with anti-microbial drugs, or accutane in severe cases. New treatment uses blue light to destroy P.acnes.

Question 6

Staphylococcus

Answer 6

Non-motile, clustered, Gram positive cocci, Cat+, Ox-

Frequently found in upper respiratory tract and on skin.

Can cause skin abscesses, impetigo (blisters/crusts I’m skin), MRSA. Can cause pneumonia and sepsis.

Question 7

Mastitis

Answer 7

Inflammation of the mammary glands caused by S.aureus.

Toxins produce inflammation (immune response), and tissue damage.

Question 8

Streptococcus

Answer 8

Non-motile, chains, Gram positive cocci, Cat-, Ox-

Can cause cellulitis (inflammation of connective tissue), Erysipelas (blistering on face), impetigo (blistering/crusts on skin), Scarlet fever (fine pink rash all over body) and Strep throat (throat infection/tonsillitis)