Flashcards in Unit 5 - Chapter 21 - Information Deck (50)
thin outer portion composed of several layers of epithelial cells, an effective physical barrier against microorganisms
outermost layer of the epidermis, consists of many rows of dead cells that contain waterproofing protein called keratin
waterproofing protein in stratum corneum
composed of what?
what is in it?
inner, relatively thick portion of skin, composed mainly of connective tissue.
Hair follicles, sweat glands, oil glands in dermis provide passageways through which microorganisms can enter skin and penetrate deeper tissues
provides moisture and some nutrients for microbial growth.
Contains SALT which inhibits many microorganisms
and LYSOZYME, capable of breaking down cell wall of bacteria,
and ANTIMICROBIAL PEPTIDES
secreted by what, and what does it contain?
secreted by oil glands, mixture of lipids, proteins, and salts that prevents skin and hair from drying out. Nutritive for many microorganisms.
enzyme that digests peptidoglycans
in perspiration & sebum, inhibits many microorganisms
in perspiration & sebum, inhibits microbes
defensins of the skin
gram positive normal flora
numbers and 2 types
large numbers, include staphylococci and micrococci
gram positive, part of the skin's normal microbiota; relatively resistant to environmental stresses such as drying and high-salt
where does it inhabit
growth supported by what?
diptheroids (pleomorphic rods), typically anaerobic, inhabit hair follicles. Growth is supported by sebum, cause acne
gram negative normal flora
Acinetobacter, Malassezia furfur (yeast that causes dandruff)
small, fluid-filled lesions
vesicles larger than about 1cm
flat, reddened lesions
lesions containing pus
skin rash that arises from disease conditions
skin rash that occurs on mucous membranes (such as interior of the mouth)
spherical, G+, irregular clusters, non-spore forming, nonmotile
what percentage of what?
coagulase --; 90% of the normal microbiota; not pathogenic unless skin is broken
Staphylococcus aureus -
mannitol salt agar culture friendly?
location & population percentage
mannitol salt agar +
the most pathogenic staphylococci
permanent resident of nasal passages of 20% of the population; an additional 60% carry it there occasionally
S. aureus - virulence and host evasion
have a lot of virulence factors and means of evading host defenses
S. aureus - when it infects (inflammation)
when it infects, it stimulates a vigorous inflammatory response and macrophages & neutrophils are attracted to the infection site
S. aureus - how it evades host defenses
resistant to o...
resistant to l...
blocks chemotaxis of neutrophils to site;
produces toxins that kill macrophages;
resistant to opsonization;
produces proteins to neutralize antimicrobial peptide defensins of skin;
cell wall is resistant to lysozyme
enzymes S. aureus produces:
hyaluronidase: digests the intercellular hyaluronic acid that binds connective tissue
staphylokinase: digests blood clots
DNAse: degrades DNA - deoxyribonuclease
lipase: helps bacteria colonize on oily skin surfaces
cutaneous anthrax - most common and least dangerous; caused by endospores entering through skin through small cuts/abrasions
which group is most important
Group A strep is most important beta-hemolytic streptococci
most common human pathogen,
responsible for a number of human diseases;
cells contain hemolysins that can lyse RBCs and almost any type of cell.
S. pyogenes: M protein
allows microbe to:
prevents the activation of complement
allows the microbe to evade phagocytosis and killing by neutrophils
Strep pyogenes enzymes:
Streptokinases: dissolve blood clots
Streptolysin: lyse RBC
Hyaluronidase: dissolve hyaluronic acid in connective tissues
DNAse: degrades dna (deoxyribonucleases)
where is it located?
capable of surviving...
causes what disease?
in soil & water.
Capable of surviving in any most environment,
resistant to many antibiotics and disinfectants.
Cause pseudomonas dermatitis.
P. aeruginosa toxins
produces how many exotoxins and endotoxins?
grows in what, which contributes to what?
what kind of pathogen for what kind of patients?
produces several exotoxins and 1 endotoxin,
grows in dense biofilms that contribute to its frequent identification as a cause of nosocomial infections of indwelling medical tubes/devices.
A serious opportunistic pathogen for patients w/ cystic fibrosis & burn patients w/ 2nd/3rd degree burns.
enveloped DNA virus;
hhv-3 diseases caused
causes chickenpox and herpes zoster (shingles);
hhv-3 incubation pd
incubation period is 10-20 days;
hhv-3 first symptoms
hhv-3 portal of entry
Attaches to what
Invades & enters what?
enters respiratory tract, attaches to respiratory mucosa, then invades and enters bloodstream.
virus enters sensory nerves and travels to dorsal root ganglia, where it remains latent. Provides a resevoir of virus for the reactivation condition of shingles.
hhv-3 mode of transmission
very contagious--almost certainly will get it once exposed to it
live attenuated vaccine; zostavax is for 60+
fungi that colonize the hair, nails, and outer layer (stratum corneum) of the epidermis; grow on keratin
ringworm, dermatomycoses (skin disease caused by fungus); caused fungal infections
athletes foot, ringworm of the feet
scalded skin syndrome -
caused by which toxin?
endo or exotoxin
encoded by phage or plasmid?
toxin causes what?
toxin enters where and goes where?
caused by staphylococcal toxin, caused by exfoliative toxins A and B (exotoxins),
encoded by a phage.
The toxins cause a separation in the skin layers.
Toxins enter through blood stream to some focus of infection (throat, eye, impetigo infection) and travel throughout body). Split occurs just above stratum basale