skin diseases

• staphylococcus or streptococcus

• The normal skin microbiota contains staphylococcus species specifically S. Epidermidis and S. Hominis

Most common causes of skin infections

• hemolysis

• Coagulase

• Leukocidins

• Protein A

• Toxic shock syndrome toxin-1

Staphylococcal virulence factors

• staphylococcal aureus often causes pyoderma (pus forming) skin infections

• Folliculitis: bacteria invades hair follicle. Can also be contributed by sweat, shaving, ect.

• Deeper infection causes boil, abscesses, furuncle

• Progression from a boil causes carbuncle

Superficial staphylococcal infections common cause

• Folliculitis: bacteria invades hair follicle. Can also be contributed by sweat, shaving, ect.

• Deeper infection causes boil, abscesses, furuncle

• Progression from a boil causes carbuncle

Common superficial staphylococcal infections

• S. Aureus cause

• Exotoxins produce erythema and severe skin peeling

• Antibiotics of cephalosporin or oxacillin and fluid therapy

Staphylococcal scaled skin syndrome cause, sings, treatment

• caused by S.aureus or in combination with streptococcus pyogenes

• Formation of lesions around the mouth and nose where bullae can become yellowish crusted sores

• Topical ointment (mupirocin) or oral

Impetigo

• Streptococcus pyogenes

• infection of dermis or hypodermis

• Painful red skin

Cellulitis cause, appreance

~ streptococcal pyogenes

• cellulitis

• Erysipelas

• Erythema nodosum

• Necrotizing fasciitis

~ penicillin

Common streptococcal skin infections and treatment

• Streptococcus pyogenes

• Infected dermis causing inflamed skin on legs or face

• Can be suppurative where bullous forms from erysipelas

• Usually self limiting

Erysipelas case, appearance

• Streptococcus pyogenes

• inflammation of the subQ

• May cause red nodules on skin or shins

Erythema nodosum cause, appearance

• when streptococcus spreads to fascia

• Virulence factors destroy host tissue and prevent neutrophils to reach infection site

• Requires debridement, amputation, IV antibiotics

Necrotizing fasciitis cause, treatment

• caused by pseudomonas aeruginosa

• Blue-green pus due to pyocyanin and pyoverdine pigments

• Can cause hot tub rash

• Tend to be antibiotic resistant due to production of beta-lactamases

Pseudomonas skin infection cause, appearance, treatment

• acne originally forms due to clogged follicles forming comedones that either turn into white or black heads

• Cutibacterium acne that feeds on sebum can infect comedones causing inflammatory lesions of papules, pustules, nodules, pseudocysts

Acne vulgaris cause and MOA

• mild: salicylic acid or retinoids

• Moderate: antibiotics of erythromycin or clindamycin, acne creams (benzoyl peroxide), hormones

• Severe: isotretinoin that reduces oil buildup

Acne vulgaris treatment

• bacillus anthracis

• Affects animals and can be spread by their products such as wool or hide casing wool sorters disease

• Penicillin and tetracycline

• Vaccine is available

Anthrax cause and treatment

• endospores enter body through abrasions of skin to form a nodule where cells die to then form a black eschar

• Can lead to Bacteremia and Septicemia

• Has a capsule

• Produces 2 exotoxins: enzymatic lethal toxin and edema toxin

• Its spores and toxins are used as biological weapons

Anthrax MOA and use

• gastrointestinal

• Pulmonary / inhalation

• Injection: IV drug users

Non-cutaneous anthrax

• caused by mycobacterium leprae

• Not highly contagious

• Affects PNS and skin cells

• Patients cannot sense environmental changes and have deformed hands, feet, eroded bones

Leprosy cause, signs

• capsule and cell wall allow it to invade Schwann cells to cause demyelination

Leprosy virulence factors

• caused by mycobacterium chelonae or haemophilum within the group of rapidly growing mycobacterium

• Treatment of Macrolide antibiotics with many used concurrently

Tattoo associated mycobacteria infection cause and treatment

• inflammation of the conjunctiva causing pink eye

• Caused by haemophilus influenzae most common, moraxella caarrhalis, streptococcus pneumoniae, staphylococcus aureus

• Treatment with neomycin

Bacterial conjunctivitis cause, MOA, treatment

• occurs in newborns where mothers have certain STDs

• Can be caused by neisseria gonorrheae, chlamydia trachomatis

• Treatment is silver nitrate, erythromycin

Neonatal conjunctivitis cause, treatment

• caused by staphylococcus aureus and/or pseudomonas aeruginosa

• Contact users are at high risk

• Can cause blindness so treatment is important

Bacterial keratitis cause and effects