microbio ch. 22 - skin infections

What skin diseases are caused by Staphylococcus aureus? 

food poisoning, hair follicle infections, impetigo, infective endocarditis, staphylococcal scalded skin syndrome, toxic shock syndrome

What virulence factors does S.aureus possess? 

capsule, clumping factor, coagulase, enterotoxins, exfollative toxins, fibronectin-binding protein, tissue-damaging enzymes, pore-forming toxins, protein A, toxic shock syndrome

What do capsules of S.aureus play in causing disease or evading the host immune system?

antiphagocytic

What do clumping factor of S.aureus play in causing disease or evading the host immune system?

allows it to clot and stick

What do coagulase of S.aureus play in causing disease or evading the host immune system?

blocks immune response

What do enterotoxins of S.aureus play in causing disease or evading the host immune system?

supterantigen that causes food poisoning

What do exfollative toxins of S.aureus play in causing disease or evading the host immune system?

causes scalded skin syndrome because connection between layers is broken

What do fibronectin-binding protein of S.aureus play in causing disease or evading the host immune system?

adhesin that allows it to attach

What do tissue-damaging enzymes of S.aureus play in causing disease or evading the host immune system?

kill off tissues

What do pore forming toxins of S.aureus play in causing disease or evading the host immune system?

causes leakage

What do proetin A of S.aureus play in causing disease or evading the host immune system?

type of Fc receptor that renders antibody ineffective

What do TSS toxin of S.aureus play in causing disease or evading the host immune system?

non-specific activation of t cells

How do folliculitis, furuncles/carbuncles, and boils develop?

inflammatory response in hair follicle that progresses to carbuncle (has pus)

What are the symptoms of staphylococcal scalded skin syndrome?

malaise, irritability, fever, sensitive red rash with sandpaper texture, large blisters, peeling of outer skin layers

Why do some strains of S. aureus cause scalded skin syndrome while others don’t?

there are different virulence factors

What toxin is associated with staphylococcal scalded skin syndrome and what is its mechanism of action?

strains of Staphylococcus aureus that produce exfoliative toxins

How is staphylococcal scalded skin syndrome treated?

antibiotics; remove dead tissue; isolate patient to limit spread of the pathogen to others and to prevent secondary infection.

What are the etiological agents of impetigo?

Staphylococcus aureus, Streptococcus pyogenes

What are the symptoms of impetigo?

non-bullous impetigo: papules, vesicles, then pustules that break, releasing plasma which dries, forming yellowish crusts. Bullous impetigo: large, gradually darkening blisters (bullae), no crusts

How is impetigo spread and where do the organism that cause the disease originate?

organisms enter the skin, sometimes through minor breaks; some S. pyogeness trains that cause impetigo can also cause glomerulonephritis; exfoliative toxin-producing S. aureus causes bullous impetigo: Staphylococcus aureus, Streptococcus pyogenes

How is impetigo treated?

appropriate antibiotic, topical or oral

What disease can occur as a result of Streptococcus pyogenes caused impetigo? 

AGN or rheumatic fever

What agent causes bullous and non-bullous impegito

only s aureus; s. aureus and pyogenes

What is the etiological agent of Rock Mountain Spotted Fever?

Rickettsia rickettsii, an obligate intracellular bacterium

What are the symptoms of Rock Mountain Spotted Fever?

headache, muscle and joint pain, and fever, followed by a rash that begins on the extremities

How is Rock Mountain Spotted Fever spread?

zoonosis transmitted by bite of infected tick

What is the pathogenesis of Rock Mountain Spotted Fever?

organisms multiply at site of tick bite, invade the bloodstream, and then infect endothelial cells; blood vessel involvement and systemic inflammatory response damage tissues.

How is Rock Mountain Spotted Fever prevented and treated?

appropriate antibiotics; avoid tick-infested areas; use tick repellent; remove attached ticks.

What is the etiological agent of chicken pox?

Varicella-zoster virus, a herpesvirus; enveloped double-stranded DNA virus

What are the symptoms of chicken pox?

fever, headache malaise; itchy bumps and blisters in various stages of development; latent infections can reactivate, resulting in shingles.

How is chicken pox spread?

respiratory route and skin lesions

What is the pathogenesis of chicken pox?

virus enters the respiratory tract, replicates in lymph nodes, and is carried in the bloodstream to the skin; there it spreads locally, resulting in development of the characteristic rash.

How is chicken pox prevented and treated?

antiviral medication; attenuated vaccine, post-exposure prophylaxis with VAR (vaccine) or VARIZIG (hyperimmune globulin). Shingles incidence can be significantly reduced with recombinant zoster vaccine (RZV).

What disease occurs later in life due to a reactivation of the Varicella virus? 

herpes zoster/shingles (same symptoms, etc. as chickenpox)

What is the etiological agent of measles? 

rubeola virus, an enveloped single-stranded RNA virus

What are the symptoms of measles?

koplik spots, fever, weepy eyes, cough, nasal discharge, rash

How is measles spread?

acquired by respiratory route; highly contagious; humans are the only source

What is the pathogenesis of measles?

virus multiplies in respiratory tract; spreads to lymph nodes, then to other parts of body; immune response to infection in skin cells leads to maculopapular rash.

How is measles prevented and treated?

no antiviral treatment; attenuated vaccine (MMR or MMRV).

What is the etiological agent of German measles?

rubella virus, an enveloped RNA virus

What are the symptoms of German measles?

mild fever and cold symptoms, swollen lymph nodes behind the ears, rash beginning on forehead and face; joint pain in some teens and adults

How is German measles spread?

infection occurs via the respiratory route; humans are the only source.

What is the pathogenesis of German measles?

replication in the upper respiratory tract, then virus spreads to all parts of the body; immune response results in rash; an infected fetus may develop abnormally.

How is German measles prevented and treated?

no specific antiviral treatment; attenuated vaccine (MMR or MMRV).

Why is German measles of special concern to pregnant women?

spread to baby

What group of fungi cause skin diseases? 

dermatophytes

What enzyme do these fungi (that cause skin diseases) possess and what is its function? 

produce keratinase

What yeast is a frequent cause of diaper rash?

candida albicans

How are fungal skin diseases prevented and treated?

antifungals; keep skin clean and dry