Chapter 21 - Microbial Diseases of the Skin and Eyes Flashcards
Staphylococcus Aureus affects the _____.
skin
Staphylococcus aureus is gram +/-?
positive
S.aureus is coagulase ________ meaning….
-positive
-it can produce coagulase
Coagulase
-an enzyme that clots fibrin in blood
Staphylococcus epidermis is coagulase _________ meaning….
-negative
-it does not produce coagulase
S. epidermidis make up ___% of normal microbiota on the skin
90
When is S. epidermidis pathogenic?
when the skin barrier is broken or invaded by medical procedures (ie. catheter)
Which staphylococci is the most pathogenic?
S. aureus
What is the purpose of the gold pigment in S. aureus?
-protects against the antimicrobial effects of sunlight
Enterotoxins
-affect GI tract
How does S. aureus invade?
-direct invasion, attach to follicle
-stimulates vigorous inflammatory response
-produces toxins that kill phagocytic cells
Where is S. aureus common in humans?
nasal passages
Folliculitis
-a symptom of S. aureus
-often occur as pimples
Sty
-a symptom of S. aureus
-the infected follicle of an eyelash
Furuncle (Boil)
-symptom of S. aureus
-more serious hair follicle infection
-pus, red, swollen surrounded by inflamed tissue
-a type of abscess
Carbuncle
-development of furuncle of S. aureus
-inflammation of tissue under the skin
-usually has fever
What is the treatment of a carbuncle?
-surgery
-penicillin
What bacteria causes impetigo?
Staphylococci
What is impetigo?
-highly contagious skin infection
-affects children age 2-5
-yellow crusts
Pemphigus Neonatorum
impetigo of the newborn
Does impetigo use an exotoxin?
no
Impetigo is a __________ meaning…
pyoderma; pus in the skin
Scalded Skin Syndrome (SSSS)
-redness
-itching
-blisters
-exfoliation, separation of skin layers
-contagious clear fluid filled blisters
What is a big risk of SSSS?
secondary infection, SSSS is a great portal of entry for other bacteria
Who is most at risk of SSSS?
in children and elderly
How do you treat SSSS?
-penicillin
-isolation
-clean fomites
What is the role of the exotoxin in SSSS?
-it is exfoliative
-breaks ester bonds between skin cells
Desquamation
skin shedding
Exfoliative Toxin A
-local
-causes bullous impetigo
Exfoliative Toxin B
-circulates
-causes SSSS
What does SSSS stand for?
Staphylococcal Scalded Skin Syndrome
Name 3 ways someone can get TSS
- tampon use
- surgical wound
- childbirth
Why are tampons such a good medium for bacterial growth?
-blood makes them nutrient rich
-abrasive material
Symptoms of TSS
-fever
-aches
-nausea
-vomiting
-confusion
-shock (impaired kidney function)
-red skin rash
What can the TSS rash be?
SSSS
What is the occurrence of death with with TSS?
less than 3%
TSS Toxin 1 and 2
-formed at the growth site and circulates in the bloodstream
Why do TSS symptoms result?
Super antigenic properties of the toxin
How to prevent TSS?
-hand washing
-frequently changing tampons
-using pads or menstrual cups
Streptococci are gram ____ bacteria
positive
What do streptococci secrete as they grow?
toxins and enzymes
__________ are a toxin released by streptococci?
hemolysins; they lyse red blood cells
What two categories are streptococci grouped into?
alpha-hemolytic and beta-hemolytic
What is GAS?
group A streptococci
How are streptococci grouped by serology?
according to antigenic carbohydrates in their cell walls
GAS are synonymous with Streptococcus ________.
pyogenes
What kind of hemolytic group is S. pyogenes?
beta-hemolytic
Streptolysins
-released by S. pyogenes
-lyse red blood cells
-toxic to neutrophils
S. pyogenes has ________ which is…
M protein; external to the cell walls prevents the activation and allows the microbe to evade phagocytosis and neutrophils and colonize mucous membranes
Does GAS have a capsule?
yes
What does GAS produce?
-streptokinases (dissolve blood clots)
-hyaluronidase (cements cells together)
-deoxyribonucleases (degrade DNA)
What is a common infection S. aureus and S. pyogenes cause?
Impetigo in children age 3-5
What is erysipelas?
-an infection of the dermis caused by S. pyogenes
What is the symptom of erysipelas?
-skin errupts into reddish patches with raised margins
What antibiotic usually is sensitive to S. pyogenes?
cephalosporins and penicillin
What can erysipelas become if not treated?
septicemia