Chapter 21 Microbial diseases of skin Flashcards
what type of organism causes folliculitis?
bacteria; Staphylococcus aureus
what causes S. aureus to infect to cause folliculitis?
enters through a natural opening in the skin (hair follicle)
what 4 things can folliculitis appear on the skin as?
pimples
sty
furuncle
carbuncle
what is a sty?
infected follicle of an eyelash
what is a furuncle?
(boil) abscess, localized region of pus surrounded by inflamed tissue
hard to treat with antibiotics (they do not penetrate well into abscesses)
what is a carbuncle?
very deep, hard round deep inflammation of tissue under skin
produces fever
more severe than furuncle
what type of organism causes impetigo?
bacteria; Staphylococcus aureus and also Streptococcus pyogenes
what is the difference between non-bullous impetigo and bullous impetigo?
non-bullous: most common form/ occurs mostly in children/ mild form
bullous: “scalded skin syndrome” release 2 toxins = more severe
what is a vesicle?
small fluid-filled lesions
when does a vesicle become a bullae?
when it becomes larger than 1 cm in diameter
what are macules?
flat lesions
what are papules? pustules?
raised lesions
pustules contain pus
Which Gram + bacterium causes inflammatory acne?
Propionibacterium acnes
what are comedos?
whiteheads
what are comedones?
blackheads
what is a virulence factor?
anything that makes an organism more harmful to the host
- protection against sunlight
- surface proteins allowing for host attachment
- contains coagulase
- produce toxins
- secrete protein blocking chemotaxis of neutrophils
- resistant to opsonization
- super antigens
What are the names of the toxins that cause scalded skin syndrome?
Exfoliative toxin A (localized)
Exfoliative toxin B (distant)
Which two bacteria cause impetigo?
Staphylococcus aureus
Streptococcus pyogenes
How does TSST-1 affect the body?
Toxic shock syndrome;
due to toxins, it is life-threatening
- fever
- vomiting
- sunburn-like rash
- organ failure
Which organic acid produced by fermenting bacteria causes inflammation in the skin?
Propionibacterium acnes metabolizes sebum, eats glycerol and leaves fatty acids behind causing inflammatory acne
Which type of acne is the most severe?
Nodular cystic acne
What is the basis for subdividing Streptococcus into smaller divisions - specifically Greek letters?
Gets broken down into Greek letter groups based on whether it can:
- slightly lyse RBCs with hemolysin toxins (alpha-hemolytic)
- fully lyse RBCs with hemolysin (beta-hemolytic)
-don’t use hemolysin (gamma-hemolytic)
What is the basis for subdividing Streptococcus into smaller divisions - specifically serological group?
They are then further broken down into groups A-T based on what antigens they have in their cell walls
Why are the Group A β Strep relevant?
Group A beta (aka: GAS) can fully lyse RBC so they are most commonly associated with human disease (most common human pathogens)
In what groups of people does Group B β Strep mainly cause disease?
- Newborn babies (can be passed during childbirth b/c mom has it apart of their microbiome)
- Pregnant women
- Elderly
- Immunosuppressed people
What are the toxins that contribute to necrotizing fasciitis?
pyrogenic toxins - initiate a fever
Which bacterium is associated with water and can cause problems with swimmers or bathers?
Pseudomonas aeruginosa can cause Pseudomonas dermatitis (rash) b/c pores open up in warm water and bodies make the water alkaline allowing bacteria to flourish and then invade
How does measles spread?
through respiratory route (breathing, talking, etc)
What is the approximation incubation period of measles?
10-12 days
How does the chicken pox rash change over time?
First 3-4 days cause just vesicles
Then vesicles fill with pus and rupture forming scabs
how does an adult with shingles give chicken pox to a child?
chicken pox and singles are caused by the same virus (Varicella-Zoster Virus) but chicken pox is due to the initial infection, and shingles is due to virus being reactivated within the body
Are the viruses present in the body continually between chicken pox and shingles?
Yes, they remain latent within the host’s cells peripheral nerves
Which form of herpes simplex most commonly manifests near the mouth?
Herpes simplex virus-1 (HSV-1)
How is oral herpes usually spread?
Orally or respiratory route
Which type of herpes simplex is much more common?
Herpes simplex virus-1 (HSV-1)
Where does herpes simplex type-2 show lesions?
around genitalia (genital herpes)
How do superficial mycoses obtain nutrients?
Use keratin as food source (hair, nails, and stratum corneum)
What are some genera of fungi that can infect the skin?
Trichophyton
Microsporum
Epidermophyton
Know the naming of ringworm infections based on their locations.
Tinea capitis – ringworm of scalp
Tinea cruri – groin
Tinea pedis – foot
Tinea unguium – fingernails and toenails
What are the two skin parasites discussed in lecture?
Sarcoptes scabiei – scabies
Pediculus humanus – lice
How are skin parasites usually transmitted to a new host?
direct contact
what are the two subspecies of body lice.
Pediculus humanus capitis : head louse
Pediculus humanus corporis : body louse
Which subspecies of lice can transmit disease?
Pediculus humanus corporis: body louse (causes typhus)
what organism causes toxic shock syndrome?
gram + bacteria; Staphylococcus aureus
what type of bacteria cause erysipelas?
Streptococcus pyogenes
Group A beta strep (GAS)
what is erysipelas?
reddish patches with raised margins (can be local and systemic)
what is Necrotizing fascilitis? what organism causes it?
Streptococcus pyogenes
Group A beta strep (GAS)
“flesh eating bacteria” causes extreme swelling and destruction of skin
what bacteria is associated with GBS? what does it stand for?
Group B beta strep
Streptococcus agalactiae
what is the most common skin disease in humans? what organism causes it? what is its other name?
acne
Propionibacterium acnes
(Cutibacterium)
what are the three types of acne in order of increasing severity?
comedonal (mild) - white/blackheads
inflammatory (moderate)
nodular cystic acne (severe)
what is Rubeola? what organism causes it?
measles
virus
what is Rubella? what organism causes it?
german measles
virus
what are symptoms of rubeola?
cold
rash on face/trunk/extremeties
Pneumonia
secondary bacterial infections
encephalitis
what are symptoms of Rubella?
much milder than rubeola
often goes undetected except when fetuses become infected = Deaf, heart defects, autism and death
what type of organism causes small pox? what is it?
virus
rash that permanently disfigures
what is the difference between all three herpes viruses?
HSV: oral herpes
HSV-2: genetal herpes
HSV-3: chicken pox
