Skin Infections Flashcards
What are the layers of the skin?
Epidermis (stratum corneum)
Dermis
Subcutaneous Layer
Stratum corneum
25 cells thick, dead cells that have migrated from deeper layers
how often does the entire epidermis replace itself?
every 25-45 days
keratin
give cells the ability to withstand damage, abrasion, and water
Stratum Basale
several layers below the stratum corneum, attached to the dermis, source of cells that make up epidermis
What are the other protective characteristics of the skin?
sebaceous glands
antimicrobial peptides
sweat
lysozyme
What are the characteristics of the normal biota of the skin?
must be capable of living in dry and slaty conditions
majority of the normal biota are not culturable
What genera are found on the skin according to the Human Microbiome Project (HMP)
Streptococcus Staphylococcus Propionibacterium Corynebacterium Malassezia Pseudomonas Janthinobacterium
What are the maculopapular rash diseases?
characterized by flat to slightly raised colored bumps: measles rubella fifth disease roseola scarlet fever
What are other skin diseases that are not maculopapular rash diseases?
impetigo
cellulitis
SSSS
Rocky Mountain Spotted Fever
What are the vessicular or pustular rash diseases?
Chicken pox, small pox, HSV, warts, mycoses
Fifth disease
B19 parvovirus
Roseola
human herpes viruses
Impetigo
bacterial infection of skin common in children- usually near nose/mouth
Cellulitis
infected dermis connective tissue and subcutaneous layer
What is the common name for measles?
rubeola
Why was there a massive reduction in measles cases within the twentieth century?
Vaccination program
How do the symptoms of the measles start?
Fever, runny nose, cough and red weepy eyes
What appears within a few days of contracting measles?
fine rash: appears first on forehead then spreads to the rest of the body
When do measles symptoms generally disappear?
within a week
What are common and less common secondary infections you can get from measles?
common: pneumonia and earaches
Less common: encephalitis and subacute sclerosing panechalitis (SSPE: chronic progressive encephalitis)
What is the causative agent of measles?
rubeola virus
What are the characteristics of the rubeola virus?
pleomorphic, medium sized enveloped
Single stranded RNA genome
Belongs to paramyxovirus family
What are the virulence factors of the rubeola virus?
contains spike proteins, one for viral attachment to host, one for fusion with host membrane
What is the pathogenesis of measles?
infection via respiratory route» virus replicated in epithelium of upper respiratory tract» spreads to lymph nodes then spreads to the rest of the body
What is an important diagnostic sign of having measles?
infected mucous membranes
What is the epidemiology of measles?
humans are only natural host
virus spread by respiratory droplets
How many of the population was infected before routine immunization of measles?
over 99% of the population
What is the prevention and treatment of measles?
vaccine is usually given in conjunction with mumps, rubella, varicella vaccine
MMRV
no antiviral treatment exists for rubeola infection
What is scalded skin syndrome?
SSSS staphylococcal scalded skin syndrome
toxin mediated disease, occurs primarily in infants, potentially fatal
within 48 hours of the infection how is scalded skin syndrome manifested?
sin becomes red and wrinkled
large fluid-filled baskets appear
skin is tender to the touch and may feel like sandpaper
What are other symptoms of scalded skin syndrome that may arise?
malaise, irritability, fever
nose, mouth and genitalia may be painful before other indicators become apparent
What is the causative agent of scalded skin syndrome?
bacterial agent: staphylococcus aureus
disease is due to the toxins S. aureus produces called exfoliantins
What are the characteristics of exfoliatins? What do exfoliatins destroy in scalded skin syndrome?
they are toxins coded wither by plasmid or on the bacterial chromosome: destroy integral layers of the outer epidermis
How is the toxin carried in scalded skin syndrome? Where does the split occur?
released at the site of infection, absorbed and carries by the bloodstream to larger areas of skin, toxin then causes split in epidermis which occurs just below the dead keratinized outer layer of the epidermis
What is lost due to the release of the toxin in scalded skin syndrome? and what does this cause?
outer layer of skin is lost; causes body fluid loss and increases susceptibility to secondary infection
What can the mortality rates reach in scalded skin syndrome?
40%
how many % of S. aureus strains produce exfoliants?
5
Which age group can scalded skin syndrome appear in?
any age group. most frequently seen in infants, the elderly and immunocompromised
What is the only preventative measure for scalded skin syndrome?
patient isolation; limits patient exposure to potential secondary pathogens
What does the treatment include for scalded skin syndrome?
bactericidal antibiotics, antistaphylococcal such as penicillinase- resistant penicillin, treatment also involved removal of dead skin to prevent secondary infection
What is another name for the chicken pox?
varicella
What does it mean that the chickenpox produces a a latent infection?
that becomes reactive after recovery of initial illness» shingles
Which age groups are symptoms more severe in with chicken pox?
older children and adults: 20% of adults develop pneumonia
Where does the skin rash appear in chicken pox? what is the rash?
back of head, face and mouth, the rash is diagnostic
How does the rash progress in varicella?
progresses from red spots called macules to small bumps called papules to small blisters called vesicles to puss filled blisters called pustules:
Macules»Papules»Vesicles»Pustules
When does the healing begin in varicella?
after pustules break and crust over
What may lead to congenital varicella syndrome? and what is it?
the varicella infection in a newborn. it is the malformation of hands/feet, eyes, skin, neurological damage
Which patients are more at risk for varicella?
immunocompromised
What is a sequella?
condition as a result of previous infection
What are the sequellas of chicken pox?
Shingles or Herpes Zoster
Reye’s Syndrome
Shingles
caused by reactivation of dormant virus
characterized by rash around waist
Reye’s syndrome
condition evident by vomiting and coma
predominantly seen in children 5-15
mortality around 30%
asprin therapy increases risk
What is the causative agent of chicken pox?
What are its characteristics?
varicella-zoster virus
member of the herpesvirus
medium sized enveloped virus
double-stranded DNA genome
How does the chicken pox virus enter?
respiratory route, replicated and moves to the skin via bloodstream
What happens to cells infected by the varicella virus?
they swell up and lyse: release virus to enter sensory nerves
What does the occurrence of shingles correlate to?
with decline in cell mediated type 1 immunity
Recrudescence
latent virus nerve cell replicated and is carried to the skin
When does the incidence of chicken pox increase?
in winter and spring
how long is the viral incubation period of chicken pox
approximately 2 weeks, infective 1-2 days before rash until blisters crust over.
What in the body allows survival of isolated viral populations?
persistence
What is the prevention for chicken pox?
attenuated vaccine licensed in 1995
immunization should be done before 13th birthday
should not be given during pregnancy or 3 months prior to pregnancy
can be partially protected by passive immunity via infection of zoster immune globulin (ZIG)
What are warts caused by?
papillomavirus
How can warts infect skin and how long is the incubation period?
can infect skin through minor abrasion, incubation period ranges between 2-18 months
What are warts called (small tumors)
papillomas
how many skin warts nearly disappear within 2 years without treatment?
1/2
What are the characteristics of the papillomavirus? Where can they survive?
belong to papovirus family
small nonenveloped
double stranded DNA genome
50 different papillomaviruses known to infect humans
Can survive on inanimate objects including; wrestling mats, towels, shower floors
What are skin diseases caused by fungi called?
superficial cutaneous mycoses
What are superficial cutaneous mycoses caused by?
numerous species of molds, invade nails, hair and keratinized layer of skin
What are examples of Superficial Cutaneous Mycoses?
Tinea capitis= mycosis of scalp
Tinea axillaris= mycoses of the underarm
Tinea cruris= mycoses of the groin; jock itch
Tinea pedis= mycoses of the foot; athletes foot
