MICR 2050 Ch. 19: Skin and Eye Diseases

anatomical features/defenses of the skin

- epidermis (keratinized surface)

- chemicals (oils and sweat)

- antimicrobials ( sebum and sweat)

- antimicrobial peptides in epithelial cells

normal biota of skin

Streptococcus, Staphylococcus, Corynebacterium, Propionibacterium, Pseudomonas, Lactobacillus; yeasts such as Candida

What does MRSA stand for?

Methicillin-Resistant Staphylococcus aureus

How is MRSA acquired?

direct contact: touching skin/wounds, bodily fluids

indirect contact: touching contaminated surfaces like hospital beds, gym equipment, toys, etc.

What can help prevent MRSA?

Good hygiene practices

What is the primary treatment for MRSA?

Vancomycin, MRSA is on the serious threat list for antibiotic resistance

MRSA distinguishing symptoms

Skin infections that may look like pimples or boils and can be red, swollen, painful, and full of pus

What causes impetigo?

Staphylococcus aureus and Streptococcus pyogenes (bacterial)

How is impetigo acquired?

direct: touching skin or sores

indirect: sharing contained objects like towels, washcloths, etc.

Impetigo distinguishing symptoms

itchy, oozing skin lesions with honey-like appearing crust that peels off

How is impetigo prevented?

good hygiene, don't touch infected people, antibiotics

What tests are used to confirm the presence of Staphylococcus aureus?

coagulase test: it will coagulate plasma

latex bead agglutination test (binds to IgG antibodies)

What are the virulence factors of Staphylococcus aureus?

exoenzymes: hylaronidase, coagulase, staphylokinase

exotoxins: toxic shock toxin, exfoliative toxin, hemolysin

protein A: IgG binding

What are the virulence factors of Staphylococcus pyogenes?

exoenzymes: hyaluronidase, streptokinase

exotoxins: superantigens, hemolysins

What is a furuncle?

a boil, abscess of a hair follicle

What causes furuncles?

Staphylococcus aureus (bacterial)

How are furuncles acquired?

direct contact with pus/skin, contact with contaminated surfaces

How are furuncles prevented?

good hygiene

What is a carbuncle?

cluster of boils

What causes carbuncles?

Staphylococcus aureus (bacterial)

How are carbuncles acquired?

direct contact with pus/skin, contact with contaminated surfaces

How are carbuncles prevented?

good hygiene

What is Erysipelas?

subcutaneous infection that causes inflammation over a large portion of the body

-skin will be warm to touch

What causes Erysipelas?

Streptococcus pyogenes (bacterial)

How is Erysipelas acquired?

small cuts, breaks in skin

How is Erysipelas prevented?

promptly sanitizing any cuts, scratches, or other wound

What is necrotizing fasciitis?

spreading infection of connective tissue

What causes necrotizing fasciitis?

Streptococcus pyogenes/Staphylococcus aureus (bacterial)

How is necrotizing fasciitis acquired?

breaks in skin, surgical/traumatic wounds

How is necrotizing fasciitis prevented?

good hygiene, avoid touching patients with bare skin

necrotizing fasciitis distinguishing symptoms

Extensive soft-tissue destruction

What is cellulitis?

acute, spreading infection in the dermis and subcutaneous tissues (lymphangitis often occurs)

What causes cellulitis?

Streptococcus pyogenes/Staphylococcus aureus (bacterial)

How is cellulitis acquired?

breaks in skin

What is Staphylococcal Scalded Skin Syndrome?

syndrome of acute exfoliation of skin , causing top layers of epidermis to slough off

What causes SSSS?

Staphylococcus aureus (bacterial)

How is SSSS acquired?

through direct contact or droplet contact

How is SSSS prevented?

by eliminating carriers in contact with newborns

SSSS distinguishing symptoms

split skin within epidermis that causes sloughing

What is gas gangrene?

infection of tissue that causes necrosis

What causes gas gangrene?

Clostridium perfringens (bacterial)

How is gas gangrene acquired?

through a vehicle (soil), endogenous transfer through the skin, GI tract, etc.

How is gas gangrene prevented?

proper cleaning of wounds

What is Pseudomonas aeruginosa?

opportunist pathogen of burn victims

What is Mycobacterium leprae?

Leprosy= Hansen's disease

Affects cooler (peripheral) body regions

Vesicular and Pustular Rash Diseases

- rash with lesions containing fluid

- chicken pox (varicella/zoster)

- smallpox

- HFMD

What is varicella?

superficial lesions in centripetal distribution, no prodromal fever

What causes varicella?

varicella zoster virus (viral)

How is varicella acquired?

through the respiratory tract

- incubates for 10-20 days, rash resolves in 2-3 weeks

How is varicella prevented?

live- attenuated vaccine

What is zoster?

reactivation of varicella that was latent in spinal ganglia

What causes zoster?

varicella-zoster virus (viral)

How is zoster acquired?

recurring from chickenpox

How is zoster prevented?

Some immunization from varicella as a child

Once to age 50 vaccination is recommended to boost immune system

What is smallpox?

deep rash all over body, fever precedes rash, 50% fatality

- Category A bioterrorism agent

What causes smallpox?

Variola virus

How is smallpox acquired?

through droplet contact or indirect contact

How is smallpox prevented?

live virus vaccine

What is Hand, Foot, Mouth disease?

lesions in mouth with fever, common in children

What causes HFMD?

coxsackie virus (enterovirus)

How is HFMD acquired?

secretions: saliva, sputum, blister fluid, feces

How is HFMD prevented?

hand hygiene

Maculopapular Rash Diseases

measles, rubella, fifth disease, roseola, scarlet fever

What is measles (rubeola)?

Very contagious virus, report cases to CDC, Maculopapular rash on head that spreads to whole body

What causes measles?

Rubeola virus (viral)

How are measles acquired?

droplet contact

How are measles prevented?

live-attenuated vaccine (MMR/MMRV)

What is a complication of measles in young people?

subacute sclerosis panenchephilitis

What is rubella?

Relatively minor rash disease with few complications

- tetrogenic, if acquired congenitally, can cause birth defects

What causes rubella?

Rubella virus (viral)

How is rubella acquired?

respiratory droplets

-postnatal or congenital infection possible

How is rubella prevented?

MMR vaccine

What is a complication of rubella in young people?

dangerous for unborn children, can cause birth defects

What is Fifth Disease?

"slapped face" rash that spreads to limbs and trunk, tends to be confluent rather than distinct bumps

What causes Fifth disease?

Parovirus B19 (viral)

How is Fifth disease acquired?

through droplet contact or direct contact

How is Fifth disease prevented?

Frequent handwashing [no vaccine or medicine yet]

What is Roseola?

high fever that can produce rash, common in young children and babies

What causes Roseola?

human herpes virus 6 (viral)

How is Roseola acquired?

unknown

How is Roseola prevented?

unknown, it is thought that 100% of US population is exposed at some point

Wart and Wart-like Eruption Diseases

warts and molluscum contagiosum

What are warts?

A contagious infection of the epidermal layer of the skin

What causes warts?

HPV (viral)

How are warts acquired?

direct contact, auto inoculation, indirect contact

How are warts prevented?

avoid contact

What is molluscum contagiosum?

smooth, waxy nodules on the face, trunk and limbs

- can be disfiguring to immunocompromised

What causes molluscum contagiosum?

molluscum contagiosum virus (viral)

How is molluscum contagiosum acquired?

direct contact (including sexual), auto inoculation

How is molluscum contagiosum prevented?

avoid contact

Large Pustular Skin Lesions

Leishmaniasis and cutaneous anthrax (lesions greater than a few millimeters)

What is Leishmaniasis?

Protozoan disease carried by sand flies, volcano like edges with central crater

What causes Leishmaniasis?

Leishmania species (protozoan)

How is Leishmaniasis acquired?

sand fly bites

How is Leishmaniasis prevented?

avoid sand fly (vector)

What is Cutaneous Anthrax?

Painless black necrotic lesion

- least dangerous type of anthrax

- papule that grows into necrotic eschar

- category a bioterrorism agent

What causes Cutaneous Anthrax?

Bacillus anthracis (bacterial)

How is Cutaneous Anthrax acquired?

Through skin cuts, abrasions, or insect bites contaminated with anthrax spores

How is Cutaneous Anthrax prevented?

vaccine, avoid contact

Fungal Infections

cutaneous (ringworm) and superficial mycoses