22 Skin Infections

tick

Skin provides a tough, flexible outer covering impenetrable to most microbes

can become vulnerable to injuries when:

» cuts, punctures, burns, chemical injury, and insect or [__] bites that can break the barrier → provides entry for pathogens

» skin infections occur when pathogens are carried to it via bloodstream following entry from respiratory system or another site → infections can spread from point of entry of skin to other areas this way as well

Bacterial

[__] skin diseases include:

• hair follicle infections

• scalded skin syndrome

• impetigo

• Rocky mountain Spotted Fever

• Lyme disease

Hair follicle

Bacterial skin disease

[__] infections: generally mild disease caused by infection of the opening of the hair follicle

» Folliculitis: small area of infection where there is inflammation, red bumps (pimples)

» Furuncle → infection spreads out to adjacent tissues;

localized redness, swelling, tenderness, pain, and pus (build up of dead cells)

» Carbuncle: large area of infection; cause for concern

Spread: boils shed large numbers of bacteria (S. aureus) that transmits via hands and fomites in hair follicle infections

Treatment: surgical draining, oral antibiotic treatment

Complicated by antibiotic resistance

» MRSA strain → methicillin resistant staphylococcus aureus

» VRSA strain → vancomycin resistant staphylococcus aureus

Staphylococcus aureus

Hair follicle infection and SSS and Streptococcal Impetigo

Causative agent [__]: normal microbiota that exists on our skin

Staphylococcal Scalded Skin Syndrome

Bacterial skin disease

[__] (SSS): toxin mediated disease

Causative agent: S. aureus that produce exfoliatins

→ circulate around body and destroy cells under outer exterior and outer epidermis begins to diet and peel off

» occurs most frequently in babies and neonatal units → small epidemics can occur in nurseries

Prevention: patient isolation → limits spread and prevent possibility of secondary infections as exposed skin is vulnerable

Treatment: removal of dead skin infected→ serves as food for bacteria

» Antibiotic treatment

Streptococal Impetigo

Bacterial skin disease

[__]: most common type of pyoderma: skin infection with pus production

» Superficial → blisters develop as it breaks down cells it colonizes (due to self-destructing enzymes) and pops. leaves behind by yellowing crusts

Causative Agent: Streptococcus pyogenes or S. aureus

Spread: person-to-person contact, insects that land in area of infection, fomites

Rickettsia rickettsii

Rocky Mountain Spotted Fever

Causative agent [__]: small, gram-negative coccobacillus bacterium

» Obligately intracellular → must reside in other organisms/cells

Rocky Spotted Fever

Bacterial skin disease

[__]: disease that results in rash on palms, wrists, ankles, and soles of feet. Spots become raised bumps and are hemorrhagic

» replicates inside our cells

» gram-negative infection → can cause septic shock if destroyed

→ when systemic, causes damage to heart, kidneys, brain, other tissues leading to drop in blood pressure, shock, and death, without prompt treatment

Spread: from animals to humans via tick bites

» American dog tick

» Rocky Mountain wood tick

» brown dog tick

Preventon: avoid tick-infested areas

» use protective clothing; use tick repellents

» carefully inspect body and remove attached ticks carefully

Treatment: antibiotics (more effective the earlier it is given)

→ doxycycline

→ chloramphenicol

» 20% mortality rate without treatment; 5% with treatment

Borrelia burgdorferi

Lyme Disease

Causative agent [__]: large microaerophilic spirochete

Lyme Disease

Bacterial skin disease

» recognized mid 1970’s in Lyme, Connecticut by Dr. Willy Burgdorfer

[__]: progresses through 3 stages

days-weeks » early localized infection

→ Erythra migrans: expanding, “bulls eye” rash as bacteria migrates outward

→ flu-like symptoms, such as chills, headaches, and muscle pains

2-8 weeks » early disseminated infection

→ enters bloodstream and affects other parts of the body

• _{in the heart, impairs electric conduction}

• _{in nervous system, leads to paralysis and impaired mental stability}

• _{in joints, leads to arthritis}

• _{(doesn’t affect the placenta as it isn’t able to cross)}

~6 months after skin rash

→ severe headache, neck stiffness, joint pain, swelling

→ chronic nervous system impairments

• _{facial palsy, swollen knee}

• _{inflammation of brain and spinal cord}

• _{nerve pain, numbness or tingling in the hands or feet}

• _{problems with short-term memory}

Spread: bite of infected deer tick

Prevention: avoid tick-infested areas

_{» use protective clothing; use tick repellents}

_{» carefully inspect body and remove attached ticks carefully}

Treatment: antibiotics effective in early stages

Viral

[__] skin diseases include:

• chickenpox

• measles

• rubella

All are common childhood diseases and highly contagious

_{» spreads through air, as well as eye contact, and fomites}

_{» initially infects respiratory system, travel to skin by blood, and cause rashes}

Virulent as humans are their only host

Varicella-zoster virus

Chickenpox (Varicella)

Causative agent [__]: member of the herpes family

_{Herpes viruses remains in sensory nerves → can causes a latent disease that can be reawakened}

Varicella

Viral skin disease

[__] (Chickenpox): leads to diagnostic rash with red exterior and white-interior (pus-filled) blisters (pustules) → itchy lesions

_{» mild in young children; recovers well}

_{» more severe in babies, older children, adults, and immunocompromised (20% death rate)}

Pathogenesis: _{enters via respiratory tract » gets into bloodstream » infects and causes swelling alongside death of skin cells » forms the blister (sack of viruses)}

» when it pops, enables it to be spread easily

herpes

Complications of chickenpox:

_{» Secondary infections by staphylococci or streptococci can occur due to scratchy/itchy lesions}

_{» reactivates as Shingles or [__]-zoster (latent infection you can get when you are older or immunocompromised)}

_{» major threat to babies when mother are infected early in pregnancy, as they can develop congenital varicella syndrome (30% fatality rate)}

_{» Reye’s Syndrome}

^{→ characterized by brain and liver damage}

^{→ rare but high mortality rate of 30%}

^{→ aspirin increases risk}

Thankfully, Varicella has declined due to a vaccine (Attenuated vaccine) licensed in 1995

Measles

Viral skin disease

[__]: also known as “Rubeola,” “hard measles,” or “red measles”

Causes a skin rash due to the cellular immune response to viral antigens in skin

Causative Agent: Rubeola virus

Spread: respiratory droplets; highly contagious

Confirmed by: Koplik’s spots: white spots in the back of the throat

---

Many cases complicated by secondary infections

→ Pneumonia and earaches » most common

→ Subacute sclerosing panencephalitis (SSPE): death due to brain degradation » least common

---

Prevention: vaccination (MMR vaccine)

» prior to immunization, over 99% of population infected

» outbreaks occur due to lapses in vaccination

Rubella

Viral skin disease

[__]: also known as German measles, is a mild illness

but also harmful to fetuses their first summer

→ causes defects in eye, heart, and brain damage in fetus if mother is infected

→ results in spontaneous abortion; why women test for immunity against Rubella

» when antigens and antibodies bind, antigen-antibody complex can cause for inflammation and rash and joint pain

Causative agent: [__] virus

Spread: respiratory droplets

Pathogenesis: transmitted into the respiratory route

» multiplies and get send to the bloodstream (viremia) and affects body tissues

» can cross placenta and affect fetuses

Prevention: Attenuated rubella virus vaccine (MMR)