Chapter 21 - Microbial Disease of the Skin and Eyes

MICR130 Final Exam

Components of the skin that naturally protect agianst microbial invasions

perspiration (sweat)

Lysozymes

sebum

mucus membranes

perspiration (sweat)

provides moisture and nutrients for growth of bacteria

contains salt and dermocain that inhibits microorganisms

Lysozymes

breaks down bacteiral cell walls (specifically peptidoglycan)

Sebum

provides a slightly acidic film that acts as a barrier agianst pathogens

contains fatty acids that have activity agianst broad range of Gram+ bacteria

Mucus Membranes

line the body cavities that open to the exterior; made of epithelial cells

secrete mucus

often acidic

some have cilia

membrane of eyes washed by tears containg lysozymes

Normal Microbiota of the skin

large numbers of gram positive cocci

• staphylococcus (s. epidermidi)

• corynebactericease

Propionibacterium acnes

normal flora of skin

inhabits hair follicles

producces acids that maintian low skin pH

populations rise and result in inflammation and acne

Acne

most common skin disease in humans

skin cells shed in the hair follicles and combine with sebum

leads to inflammation

Corynebacterium xerosis

part of normal skin microbiota

occupy the skin surface

normal commensal, but can be opportunisitc

• opportunistic infection leads to endocarditis, sepsis, pneumonia, etc

Staphylococcal Skin infections

Staphylococcus Epidermidis

• 90% of normal skin microbiota

• coagulase negative

• common HAI

Staphyloccous Aureus

• carries in the nasal passage of 20% of the population

• coagulase positive

• produces damging toxins and can cause sepsis

• avoids host defense in the skin; secretes proteins and toxins that kill phagocytes

Toxic Shock Syndrome (TSS)

caused by staphylococcal infection

fever, vomitting, shock, and organ fialure caused by toxic shock syndrome toxin 1 in the blood stream

classic symptoms: desquamation (especially on palms) and rash

Streptococcal Skin Infection

Group A streptococci (GAS) also known as Streptococcus pyogenes

• produce virulence factors: m proteins, hyaluronidase, etc

• necrotazing fasciitis: “flesh eating disease

  • exotoxin produced by S. pyogenes acts as a superanitigen

• Streptococcal toxic shock syndrome: similar to staph TSS

Pseudomonas Aeruginosa

produces exotoxins and endotoxins

pyocyanin, toxin produced almost exclusively by this causes characteristic blue-green pus

• depresses host immune response, causes neutrophil apoptosis

opportunisitc infection of burn patients

• biofilm production and resistant to antibiotics

otitis externa

hot tub folliculitis

can cause meningitis and pneumonia

Warts

caused by Human Papillomavirus (HPV)

most common sexually transmitted disease in the US and world

more than 50 species

viral infection that can lead to cancer

can be vaccinated against common subtypes

Smallpox

caused by the Variola virus

two forms of the disease: variola major, variola minor

completely eradicated from the human population via vaccination

Chickenpox

caused by herpesvirus varicella zoster (human herpesvirus 3)

cuases pus filled vesicles

reyes syndrome

virus becomes latent in the central nerve ganglia

prevented by live attenuated vaccine

shingles

caused by the reactivation of the latent varicella zoster virus that moves along peripheral nerves to the skin

due to stress or lowered immunity

follows the distribution of affected cutaneous sensory nerves

• limited to one side of the body

Herpes Simplex Virus

Life long infection

HSV-1 is spread primarily by oral or respiratory routes

HSV-2 is spread primarily sexually

usually develop as cold sores or fever blisters

HSV-1 remains latent in trigeminal nerve ganglia

HSV-2 remains latent in sacral nerve ganglia near the spine

Measles virus

hallmark sign of infection: Koplick spots

• red spots on the oral mucosa opposite of the molars

prevented by the MMR vaccine —> live attenuated

Hand-Foot-and-mouth disease

caused by an enterovirus

spread via mucous or saliva (usually children)

rash on the hands, feet, mouth, and tongue

Ringworm

Fungal infection

dermatomycoses

tinea species

shows in a ring-like or oval rash on various body parts