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
What is necrotizing fasciitis?
-a GAS infection that eats away the fascia of connective tissue
-aka flesh eating disease
What is the mortality rate of necrotizing fasciitis?
~50%
How does necrotizing fasciitis enter?
through breaks in the skin, exoenzymes
What does NF secrete?
collagenase, hyaluronidase, and Exotoxin A
Is Pseudomonas aeruginosa gram negative or positive?
negative
Does P. aeruginosa dermatitis require hospitalization?
usually no, takes care of itself
What may cause dermatitis?
water (pools, hot tub)
How long does dermatitis usually last?
2 weeks
What is otitis externa and what bacteria causes it?
infection of the outer ear caused by P. aeruginosa
What causes otitis externa?
natural bodies of water
When is otitis externa bad?
if it infects the ear drum
How can P. aeruginosa lead to nosocomial infections?
can enter hospitals through flower vases, mop water
What do P. aeruginosa infections cause in post burn victims?
blue/green pus and a prolonged hospital stay
P. aeruginosa can lead to infection is immunosuppressed patients like…
cancer patients and CF patients
P. aeruginosa releases ______ and ______ toxins.
endo and exo
What pigment causes the blue/green pus?
pyocyanin
What virus causes warts?
Human Papillomavirus (HPV)
How many HPV species are there and how many are associated with cancers?
50 species, 16 and 18 associated with cancer
How do warts spread?
-contact
-fomites
-sexual contact
-moist areas
How are warts treated?
-liquid nitrogen
-electrodessication/ cauterization
-laser surgery
-24% salicylic acid
What is the most common STI?
genital warts
HHV-3
-varicellovirus
-chicken pox and shingles
How is chicken pox transmitted?
respiratory route
Chicken Pox Symptoms
-infection localizes in the skin cells after 2 weeks
-vesicular skin infection for 3-4 days
When can chicken pox be dangerous?
during preganacy
Where does chicken pox remain latent?
in the dorsal root ganglia
Is there a chicken pox vaccine available?
yes
Whats another name for chicken pox?
varicella
How do chicken pox wounds appear?
first as dots on skin (macule), then papule, then a fluid filled vesicle, then pustule (itchy pus filled), crust, scar
Exantham
a skin rash arising from another focus of infection (ie. chicken pox moves from respiratory tract to blood to skin)
What does chicken pox reappear as?
shingles (zoster)
Where does shingles affect?
-the girdle area (abdominal belt)
What is used to treat shingles?
acyclovir
What characterizes shingles?
-not itchy
-painful
-longer lasting (up to weeks)
Shingles is an __________.
exanthema
Is there a vaccine for shingles?
yes; for people ages 50+ called shingrix
What can trigger HHV-3 to reactivate?
stress, aging
What does HHV stand for?
Human herpesvirus
What does HSV stand for?
Herpes simplex virus
How is HSV-1 transmitted?
oral or respiratory routes
What is a symptom of HSV-1?
lesions called cold sores or fever blisters
Where does HSV-1 lay latent?
in the trigeminal nerve ganglia that communicates between the face and CNS
What can trigger recurrences of HSV-1?
UV radiation from the sun, emotional upsets, menstrual hormone changes
Does HSV need signs and symptoms to spread?
no
How is HSV-2 spread?
sexual or oral contact
How do HSV 1 and 2 differ?
-antigenic makeup and affect on cells in cell culture
-location where they lie latent
Where does HSV-2 lay latent?
in the sacral nerve ganglia near the base of the spine
Is HSV-1 or 2 more virulent?
2
Herpes Encephalitis
-when HSV-1 or 2 can rarely spread to the brain
-HSV-2 is more serious and has a 70% mortality rate
How is HSV-2 encephalitis treated?
acyclovir
Transfer between HSV-1 and HSV-2 can only happen during ____ _____.
oral sex
Herpetic Whitlow
-infection of the finger
-common in healthcare professionals
Measles and Rubella are ________.
exanthams
How is measles spread?
respiratory route
Why is quarantine not an option for preventing measles?
a person with measles is infectious before symptoms appear
Are there any antivirals that treat measles?
no
Is there a vaccine fore measles?
Yes, the MMR vaccine that has 90% efficacy
Who is most at risk for measles?
-infants, children, pregnancy
What are the initial symptoms of measles?
cold-like symptoms
Koplik’s Spots
-measles macular rash in the oral cavity
-look like salt on red bumps
The presence of Koplik’s spots is the ________ indicator for measles.
diagnostic
Measles and Encephalitis
-1/1000 measles victims
-brain degeneration
Subacute Sclerosing Panencephalitis
-1 in a million cases
-1 to 10 years after measles recovery
-severe neurological symptoms and eventually death
What complicates measles?
otitis media and pneumonia
Rubella is ________ than measles
milder
Are there any antivirals to treat Rubella?
no
Is there a vaccine for Rubella?
yes; MMR
What is another name for measles?
rubeola
What are the usual symptoms of Rubella?
-mild pink rash
-light fever
-no Koplik’s spots
How is Rubella transmitted?
respiratory route
What is the incubation period of Rubella?
2 to 3 weeks
Congenital Rubella Syndrome
-35% incidence of serious fetal damage if mother contracts during first 3 months
-leads to deafness, cataracts, heart and mental defects, maybe death
Does the Rubella rash have raised spots?
no
Conjuctivitis
inflammation of the conductive aka pinkeye
Conjunctivitis can be caused by _______ or _______.
bacteria (ie. H. influenzae) or virus (ie. measles)
Symptoms of Conjunctivitis
-pus (usually bacterial)
-redness
-red
-watery
-swollen
Whats a common cause of Pseudomonas Conjunctivitis?
-unsanitary contact lenses
How is Conjunctivitis treated?
antibiotics
What pathogen causes trachoma?
Chlamydia trachomatis
What is the leading cause of blindness?
Trachoma
Trachoma symptoms
-Conjunctivitis of eyelids, eyelids turn inward and abrade corneas (=blindness)
Trichiasis
-occurs when in-turned eyelid abrades cornea
-leads to blindness
How to fix in-turned eyelid?
surgery
How is trachoma treated?
tetracycline or erythromycin, penicillin
How is trachoma spread?
-unsanitary conditions
-overpopulation
-unavailable medical resources
