Infectious Diseases Of The Skin And Nervous System

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Natural Defenses of the skin: KSSSL

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Keratin

Skin Sloughing

Sebum

Sweat

Lysozyme

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Keratin:

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Tough waterproof layer

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Skin sloughing:

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every 20-40 days

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Sebum:

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Low pH, high lipid

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Sweat:

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Low pH, high salt

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Lysozyme:

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which digests peptidoglycan

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Normal skin flora:

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-Propionibacterium acnes

-Corynebacterium spp. (Diphtheroids)

-Micrococcus spp.

-Staphylococcus app.

---Staphylococcus epidermidi

--Staphylococcus aureus

-Streptococcus spp

-Yeasts

-Many others

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Acne causative agent:

Propionibacterium acnes

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Propionibacterium acnes

-Gram + rod

-digests sebum

-attracts neutrophils

-Neutrophil digestive enzymes cause lesions, "puss pockets" (pimples)

-Most common skin disease in humans

-Oil-based cosmetics worsen disease

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Acne Treatments:

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Benzoyl peroxide dries plugged follicles, kills microbes

-Tetracycline (antibiotic)

-Accutane- inhibits sebum formation

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Impetigo

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-Caused by

--Staphylococcus aureus

--Streptococcus pyogenes

* Peeling crusty skin

** Contagious!!!!

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SSSS: Staphylococcal scalded skin syndrome

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-Caused by: Staphylococcus aureus

-Large red blisters that peeled off in sheets

-Typically not deadly although very painful

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Staphylococcus aureus

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is associated with a number of diseases, including impetigo and SSSS

-Enzymes are virulence factors

-Coagulase (diagnostic test for S.aureus)

-Hyaluronidase

-Staphylokinase

-Lipases

** Most treated pathogen***

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Scanning Electron Micrograph (SEM) and colonies of Staphylococcus aureus:

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The causative agent of impetigo

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Necrotizing Fasciitis "Flesh Eating Strep"

GROUP A STREP-

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Streptococcus pyogenes*****

-Tissue digesting enzymes:

~Hyaluronidase

~Streptokinase

~Streptolysins

*Rapidly spreading cellulitis may lead to loss of limb

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Necrotizing Fasciitis:

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Disease starts as localized infection. Pain in area, flu-like symptoms.

-invasive and spreading

-may lead to toxic shock (drop in blood pressure)

-incidence 1-20/100,000

-30-70% mortality

-surgical removal

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Rocky Mountain Spotted Fever

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* Fever, skills, headache, muscle pain

- Red ---> black rash

~ blackish caused by hemorrhaging

----Petechiae

** Transmitted to humans BY TICK BITES (Vector- biological transmission) Now found mostly in Eastern Atlantic states

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Rocky mountain spotted fever treatable with...

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antibiotics

-diagnosed using fluorescent antibodies on tissue samples, PCR

-30% of untreated cases and 5% of treated cases are still fatal

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Rickettsia rickettsii

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--Gram negative bacillus or coccobacillus

---Obligate intracellular parasite

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Rickettsia an Obligate Intracellular Parasite:

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-bind to cell surface and are taken into

ENDOTHELIAL CELLS

-Escape from phagosome into cytoplasm

-Have ETC

-Obtain nutrients, NAD+ and CoA from host

-Cause capillaries to degrade

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Rickettsia rickettsii vectors:

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Wood Tick and Dog Tick

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Virus infections of the Skin: Vesicles

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Vesicular or pustular rash

(elevated lesions filled with fluid)

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Cold Sores

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Human simplex 1 and 2

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Chickenpox

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human Herpesvirus-3

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Smallpox

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-A disease with an interesting history

-Very infectious VIRAL disease (epidemic)

-The disease has been eliminated due to world-wide vaccine program:

--Vaccinia: a Jennerian vaccine named for Edward Jenner, 1796

**Virus has been preserved in government labs by agreement, at CDC in Atlanta and in Russia. Considered a bioterrorism agent***

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Smallpox Death rate and history stats:

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-Known for 1000s of years

-Overall death rate was 20-80% of those infected

--death in children was more common

-18th century- 400,000 per year die (Europe)

-20th Century -3 to 5 million deaths per year

-Global vaccine eradicated the disease globally

---fully eradicated by 1980

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Chickenpox

"Varicella-Zoster"

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-Common virus; decreasing disease in the USA due to effective childhood vaccine

-Benign disease with life long immunity

-Life-threatening for immunocompromised individuals

-Recuperation can result in life long benign Varicella-zoster virus latency

-May re-emerge as shingles (skin lesion)

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Chickenpox virus in the body:

Viral infection through AEROSOL DROPLET; systemic infection--->

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local infection in LYMPH NODE(S) (neck)

--lymphocyte associated viremia

-----fever, malaise

~spread throughout the body

~shed in respiratory tract secretions and Skin Vesicles (blisters of clear fluid)

--Recovery with virus latency in neurons

--> life long immunity

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Chickenpox reemerges as SHINGLES

CAUSES:

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Stress, immune suppression, drug therapy?

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Virus Infections of the Skin: Rashes

Spots, Bumps

Maculo-papular rashes (flat to slightly raised colored bump)

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Measles virus (Rubeola)

Rubella Virus (German Measles)

Fifth Disease (Human Parvovirus B19)

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Measles

Back 30

VIRAL infection through AEROSOL DROPLET: one of the MOST communicable viruses

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Measles:

Initial infection of the oro-pharynx

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--> local infection lymph node (s) of the

-->lymphocyte associated viremia

fever, malaise

--> spread throughout the body

--> Shed in respiratory tract secretions

Koplik's spots

Skin rash

--> recovery; life long immunity

*** Effective childhood vaccine (2-3 doses): MMR (measles, mumps, rubella ), but disease still exists worldwide

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Measles World Wide

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** Measels is the leading cause of vaccine-preventable death among children

** Millions of children still remain at risk from measles

- Developed countries measles death rates range from 1-5%, but among malnourished children, the death rate reaches 10-30%

- over 500,000 children under the age of five die/yr

-measles causes health complications, including pneumonia, diarrhea, encephalitis

---THE PRIMARY reason for ongoing high childhood death is the failure to deliver at least one dose of measles vaccine.

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Rubella:

Viral infection through AEROSOL DROPLET; systemic infection-->

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A mild rash

-serious for a fetus when contracted in the first trimester of pregnancy

-disrupts fetus development of the CNS and/or other organs: Congenital Rubella Syndrome

---small birth weight, blindness, hearing loss, mental retardation, heart problems

---infection lasts for months-years in the newborn

** Vaccine highly effective (MMR)**