microbio ch 17 study guide: skin & eye infections

what is the function of the epidermis?

the skin's outermost defensive structure

what cells comprise most of the epidermis? what protein is a main component of these cells? what is the protein's function?

tightly packed dead cells; most epidermis is made of keratinocytes, specialized cells that contain keratin, a waterproofing protein

what layer of skin is located below the epidermis?

dermis

what layer associated with the skin is below the dermis?

subcutaneous layer: fat cells, nerves, and blood vessels

what is melanin? what is its function?

brown pigment in our skin; has antimicrobial properties and protects against UV radiation that depletes the skin of folic acid and causes skin damage

what is the enzyme found in perspiration? what is its function?

lysosome; breaks down the peptidoglycan found in bacterial cell walls

what is sebum?

oily or waxy substance produced by the skin's sebaceous glands (oil glands) that moisturize and protect the skin

define dermatoses

infectious and noninfectious skin diseases

define lesion. what is the difference between a primary and secondary lesion?

- lesion: clinical term for any observable abnormality of the skin
- primary: directly associated with a disease and are considered key features for diagnosing a variety of infections
- secondary: less strictly defined and have diverse origins - may evolve from primary lesions, or from external forces like trauma or scratching

what is the etiological agent of chickenpox? how is it typically spread?

herpesviridae family viruse varicella-zoster; respiratory droplets and occasionally from direct contact with pox lesions

reactivation of which dormant pathogen causes shingles? where in the body does the pathogen remain dormant until reactivation?

varicella-zoster viruses; in the nerves

what is postherpetic neuraliga (PHN). what infection is it associated with?

a chronic pain condition that results from shingles

what is the etiological agent of smallpox? before eradication, why was smallpox one of the most feared diseases?

variola major virus; highly contagious pathogen acquired from inhaling respiratory droplets

what is the etiological agent of oral herpes? how does oral herpes present?

herpes simplex virus 1; cold sores or fever blisters - painful, itchy, vesicular lesions may develop on the lips about a week after infection

does HSV-1 cause a latent infection? if so, where does the pathogen lie dormant before reactivation?

yes; nerve endings at the lip

true or false. there is no cure or vaccine available for HSV-1infections.

true

what is the etiological agent of the measles?

rubeola

why is the measles making a comeback?

vaccination exemption and unvaccinated individuals

what are Koplik's spots? where are they found? what disease are they associated with?

dry spots on the mouth, macropapular rash; associated with measles

what is the mode of transmission for measles?

through the air and by contact with an infected person's respiratory droplets

what infections does the MMR vaccine protect against

measles, mumps, and rubella

what is the etiological agent of german measles? what is another name for german measles?

togaviridae; rubella

what causes congenital rubella syndrome (CRS)? what are three possible outcomes of CRS?

rubella infections in pregnant women, especially during the first trimester; stillbirth, miscarriage, or variety of birth defects (blindness, deafness, heart defects, and growth or mental disabilities)

what is the etiological agent of fifth disease? why is it referred to as "slapped cheek syndrome"?

- parvovirus B19
- causes a red facial rash

why isn't the MMR and Var vaccines administered to infants until they are one year of age or older

include live attenuated (weakened) viruses and should not be given before the immune system has time to develop

what is the etiological agent of roseola

Human herpes viruses 6 and 7

what are the two etiological agents of hand, foot, and mouth disease (HFMD)

coxsackievirus A16 and enterovirus 71 viruses

what are the etiological agents that cause warts?

papillomaviruses

which bacterium plays a major role in certain types of acne

propionibacterium acnes

staph infections are mainly caused by which bacterium

staphylococcus aureus

the textbook states that most strains of staphylococcus aureus are mannitol fermenters and beta hemolytic. what growth media are used to determine these characteristics? are they general growth, selective, differential, or selective and differential media? what does the media select for? what does it differentiate?

growth media; blod agar and msa

what two factors protect staphylococcus aureus from phagocytosis

protective polysaccharide capsule and protein A

what etiological agent can cause impetigo, erysipelas, cellulitis, and folliculitis

S. aureus

what is cellulitis

deep infection of the lower dermal and subcutaneous fat

what is folliculitis

swollen, red, pus-filled hair follicles

what does the acronym MRSA and VRSA stand for?

- MRSA: methicillin-resistant staphylococcus aureus
- VRSA: vancomycin-resistant staphylococcus aureus

what is the etiological agent of scalded skin syndrome? what virulence factor causes the skin to peel in sheets?

S. aureus; the exfoliative toxins cause the outer layer of epidermal cells to peel in sheets and leave the skin red and exposed

staphylococcus aureus can be differentiated from streptococcus pyogenes by which two biochemical tests

coagulase and catalase

true or false. streptococcus pyogenes is coagulase and catalase positive

false; S. aureus is coagulase and catalase positive

true or false. both S. aureus and S. pyogenes cause impetigo and cellulitis

true

what are streptococcus pyogenes strains clinically referred to as?

strep throat

what is the function of S. pyogenes hyaluronic acid capsule?

breaks down connective tissues

what is the etiological agent of necrotizing fasciitis and streptococcal toxic shock syndrome? what is necrotizing fasciitis referred to as

S. pyogenes; flesh-eating disease

true or false. pseudomonas aeruginosa is a common cause of HAIs. it is an opportunistic pathogen that readily establishes infections in people with weak immune systems, damaged skin, or other underlying health conditions.

true

infection with which bacterium develops in 2/3rds of burn patients

p. aeruginosa

what is pyocyanin? what bacterium produces it?

greenish-blue pigment that generates reactive forms of oxygen to further damage tissue; P. aeruginosa

what is the etiological agent of otitis externa? what is otitis externa?

P. aeruginosa; swimmer's ear, outer ear canal is infected

define necrosis

tissue death- decreased blood flow to tissue

what is the etiological agent of gas gangrene

clostridium perfringens

what is the etiological agent of cutaneous anthrax

bacillus anthracis

what are cutaneous mycoses? what is subcutaneous mycoses? which, if either, are more serious infections?

cutaneous: fungal skin infections; subcutaneous: deeper dermal or muscle infections (more serious)

define dermatophyte

collection of fungal organisms that cause conditions of the skin, hair, or nails

what is the etiological agent that causes many cutaneous mycoses, such as a diaper rash

candida albicans

what type of organism causes ringworm

fungus

what type of organism causes jock itch and athlete's foot

fungus

list three main fungal genera that cause most tinea infections

trichophyton, microsporum, and epidermophyton species

what is the etiological agent of the neglected tropical disease called leishmaniasis? what type of microbe is it? how is it transmitted?

leishmania; protozoan; bite of infected sand flies

what are the differences between cutaneous, mucocutaneous, and visceral leishmaniasis?

cutaneous: skin ulcers; mucocutaneous: lesions develop in mucous membranes of the nose or mouth; visceral: protozoan spreads throughout the body

what is the cornea of the eye? what is the conjunctiva?

transparent layer at the front of the eye that covers the iris; epithelial membrane that covers the eyeball and lines the eyelids

besides oils, mucus, sugars, what two protective factors are contained in tears? what is the function of lactoferrin

lysozyme and lactoferrin; binds up free iron

what is conjunctivitis? what is it commonly known as

inflammation of the conjunctiva or epithelial membrane over and around the eye; pink eye

what clinical features can distinguish bacterial vs. viral conjunctivitis

nature of the fluid discharge from the eye
- bacterial: puslike discharge and swollen conjunctiva
- viral: watery discharge

what microbe causes most viral eye infections

adenoviruses and herpes viruses

how can neonatal HSV eye infections be contracted

transmission from the mother to the infant as the baby passes through the birth canal

which two bacteria cause neonatal bacterial conjunctivitis? how is it acquired

neisseria gonorrhoeae or chlamydia trachomatis; acquired by vertical transmission at birth

why are antibiotic drops administered to baby's eyes after delivery

prevent infections

what is the leading cause of bacterial blindness in the US? what is the etiological agent?

trachoma; chlamydia trachomatis

what is keratitis

severe inflammation of the cornea

what is the etiological agent of most herpetic keratitis infections? what nerve does this microbe lay dormant in

herpes simplex 1 virus; ophthalmic nerve

what is the leading cause of infectious blindness in the US? why?

herpetic keratitis

what two organisms are the most common cause of bacterial keratitis?

pseudomonas aeruginosa and staphylococcus aureus

which individuals are at highest risk for fungal keratitis

individuals that have suffered eye trauma or have had eye surgery

what is the etiological agent of protozoan keratits

acanthamoeba

what is the etiological agent of helminthic keratitis? what is the medical name and the common name for this infection

onchocerca volvulus; ocular onchocerciasis

how is helminthic keratitis introduced into humans? what nerve and/or eye structure is damaged by this pathogen

infected blackfly bites someone; optic nerve and/or cornea