Chapter 21 Flashcards
Natural defenses of the skin
Keratin: Tough waterproof layer
Skin sloughing: Every 20-40 days
Sebum: Low pH, high lipid
Sweat: Low pH, high salt, and
Lysozyme: which digests peptidoglycan
Normal skin flora
•Propionibacterium acnes
•Corynebacterium spp. (Dipththeroids)
•Micrococcus spp.
•Staphylococcus spp.
•Streptococcus spp.
•Yeasts
•Many others
Propionibacterium acnes: Gram positive rod is also known as
Acne
Steps of acne formation
- Digests sebum
- Attracts neutrophils
- Neutrophil digestive enzymes cause lesions, “pus pockets”
Most common skin disease in humans
Acne
Oil-based cosmetics worsen disease
Acne
Benzoyl peroxide dries plugged follicles, kills microbes which treats
Acne
Tetracycline (antibiotic) can treat
Acne
Accutane – inhibits sebum formation can treat
Acne
Contagious crusty skin
Impetigo
Impetigo is caused by
Staphylococcus aureus or Streptococcus pyogenes
Large red blisters that peeled off in sheets; typically not deadly although very painful
(SSSS) Staphylococcal scalded skin syndrome
Most treated pathogen
Staphylococcus aureus
Associated with a number of diseases, including impetigo and SSSS
Staphylococcus aureus
These enzymes are virulence factors for Staphylococcus aureus
Coagulase (diagnostic test for S. aureus), Hyaluronidase, Staphylokinase, Lipases
“Flesh Eating Strep”
Necrotizing Fasciitis
Necrotizing Fasciitis “Flesh Eating Strep” is caused by
Streptococcus pyogenes (Group A Strep)
Tissue digesting enzymes
• Hyaluronidase
• Streptokinase
• Streptolysins
Rapidly spreading cellulitis may lead to loss of limb due to this condition
Necrotizing Fasciitis “Flesh Eating Strep”
Disease starts as localized infection; Pain in area, flu-like symptoms
Necrotizing Fasciitis
Invasive and spreading; May lead to toxic shock (drop in blood pressure)
Necrotizing Fasciitis
30-70% mortality, requires surgical removal and antibiotics
Necrotizing Fasciitis
Causes fever, chills, headache, muscle pain
Rocky Mountain Spotted Fever
Red to black rash (caused by subcutaneous hemorrhaging) Petechiae
Rocky Mountain Spotted Fever
Transmitted to humans by tick bites, now found mostly in Eastern Atlantic states
Rocky Mountain Spotted Fever
A negative bacillus or coccobacillus, is also obligate intracellular parasite
Rickettsia rickettsii
Bind to cell surface and are taken into endothelial cells
Rickettsia rickettsii
Escape from phagosome into
cytoplasm, have ETC
Rickettsia rickettsii
Obtain nutrients, NAD+ and CoA
from host; Cause capillaries to degrade
Rickettsia rickettsii
Vectors of Rickettsia rickettsii
Wood Tick and Dog Tick
Treatable with antibiotics; Diagnosed using fluorescent antibodies on tissue samples, PCR
Rocky Mountain Spotted Fever
30% of untreated cases and 5% of treated cases are still fatal
Rocky Mountain Spotted Fever
Vesicles are
Vesicular or pustular rash (elevated lesions filled with fluid)
Human Pox virus
Smallpox
Human simplex 1 and 2
Cold Sores
Human Herpesvirus-3
Chickenpox
This disease has been eliminated due to world-wide vaccine program (Vaccinia: a Jennerian vaccine) very infectious viral disease (epidemic)
Smallpox
The virus has been preserved in government labs by agreement, at CDC in Atlanta, and in Russia, considered a bioterrorism agent
Smallpox
This disease was known for thousands of years; Overall death rate was 20-80% of those infected (Death in children was more common)
Smallpox
“Varicella – Zoster”
Chickenpox
Common virus; decreasing disease in the USA due to effective childhood vaccine
Chickenpox “Varicella – Zoster”
Benign disease with life long immunity, but life-threatening for immunocompromised individuals
Chickenpox “Varicella – Zoster”
Recuperation can result in life long benign Varicella-zoster virus latency (shingles)
Chickenpox “Varicella – Zoster”
Viral infection through aerosol droplet; systemic infection
Chickenpox virus
Maculo-papular rashes
flat to slightly raised colored bump (Measles virus, Rubella virus, Fifth Disease)
Chickenpox virus infection life cycle
1.local infection in lymph node(s) (neck)
2.lymphocyte associated viremia(Fever, malaise)
3. Spread throughout the body
4.Shed in respiratory tract secretions and Skin Vesicles (blisters of clear fluid)
5.Recovery with virus latency in neurons
6.Life long immunity
Viral infection through aerosol droplet: One of the MOST communicable viruses
Measles
Measles infection life cycle
- Initial infection of the oro-pharynx; local infection lymph node(s) (of the neck)
2.lymphocyte associated viremia (Fever, malaise)
3.Spread throughout the body
4.Shed in respiratory tract secretions
Koplik’s spots (Skin Rash)
5.Recovery; life long immunity
MMR vaccine
Effective childhood vaccine (2-3 doses): MMR (measles,mumps, rubella), but measles still exists worldwide
The leading cause of vaccine-
preventable death among children
Measles
Measles causes
health complications, pneumonia, diarrhea, encephalitis
Death Rate for Measles
Developed countries: 1-5%
Malnourished children: 10-30%
The primary reason for ongoing high childhood deaths
is the failure to deliver at least one dose of measles vaccine
Viral infection through aerosol droplet; systemic infection (mild rash)
Rubella
Rubella is serious for a fetus when contracted in the first trimester of pregnancy because
•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
Rubella has a vaccine that is highly effective called
MMR (measles, mumps, rubella)
