Chapter 17: Skin and Eyes Infection

What is the function of the epidermis?

keep out infectious agents

What cells comprise most of the epidermis? What protein is a main component of these cells? What is the protein’s function?

keratinocytes that contain keratin which is used for waterproofing the skin

What layer of skin is located below the epidermis?

dermis

What layer associated with the skin is located below the dermis?

subcutaneous layer

What is melanin? What is its function?

the brown pigment in our skin, has antimicrobial properties and protects ultraviolet radiation

What enzyme is found in perspiration? What is its function?

lysozyme that breaks down peptidoglycan found in bacterial cells walls

What is sebum?

an oily or waxy substance produced by the skin’s sebaceous glands (oil glands) and is a combination of low-pH lipids and proteins that moisturize and further protect the skin

Define dermatoses

infections and noninfectious skin diseases

Define lesion

change or abnormality in the skin that is usually in a defined area; may be harmless or serio

What is the difference between a primary and secondary lesion?

primary - closely associated with a specific disease process; useful for diagnosis

secondary - have diverse origins and are less obviously associated with a specific disease; may develop from a primary lesion

What is the etiological agent of chickenpox? How is it typically spread?

varicella-zoster, spreads through 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(chicken pox), remains in peripheral nerves

What is postherpetic neuralgia (PHN). What infection is it associated with?

pain that persists after a shingles rash heals; due to skin nerve damage caused by a virus in the herpes family

What is the etiological agent of smallpox? Before eradication, why was smallpox one of the most feared diseases?

variola virus, had a high mortality rate and could be easily transmitted through inhaling respiratory droplets

What is the etiological agent of oral herpes? How does oral herpes present?

Herpes simplex virus 1, vesicular lesions(cold sores) around the mouthv

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

can cause latent infections by migrating to the trigeminal nerve

True or False. If the statement is false, correct it. There is no cure or vaccine available for HSV-1 infections

true

What is the etiological agent of the measles?

rubeola virus

Why is measles making a comeback?

legislation to mandate the vaccine was removed or limited, there was an outbreak

What are Koplik’s spots? Where are they found? What disease are they associated with?

red spots with white dots in the center that may appear in the mouth, associated with measles

What is the mode of transmission for measles?

through 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?

rubella virus, also called Rubella

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

rubella infections in pregnant women, can lead to stillbirth, miscarriage, or birth defects

What is the etiological agent of fifth disease? Why is it referred to as “slapped cheek syndrome”?

human parvovirus B19, because it 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?

they 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? IF APPLICABLE, what does the media select for? What does it differentiate?

mannitol salt agar(MSA), both selective and differential, selects for bacteria that can thrive in high salt environment, differentiates mannitol fermentation

What two factors protect Staphylococcus aureus from phagocytosis?

protective polysaccharide capsule and protein A on its cell surface

What etiological agent can cause impetigo, erysipelas, cellulitis, and folliculitis?

Staphylococcus aureus and Streptococcus pyogenes

What is cellulitis?

deeper Staphylococcus aureus infection of the lower dermal and subcutaneous fat, red, swollen, and painful skin

What does the acronym MRSA stand for?

(methicillin-resistant Staphylococcus aureus

What does VRSA stand for?

vancomycin-resistant S. aureus

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

Staphylococcus aureus, exfoliative toxins A and B

Staphylococcus aureus can be differentiated from Streptococcus pyogenes by which two biochemical tests?

coagulase test and catalase test

True or False. If the statement is False, correct it: Streptococcus pyogenes is coagulase and catalase positive

false, Staphylococcus aureus is coagulase and catalase positive, S. pyogenes is negative

True or False. If the statement is False, correct it. Both S. aureus and S. pyogenes cause impetigo and cellulitis

true

What are Streptococcus pyogenes strains clinically referred to as?

group A streptococci

What is the function of S. pyogenes’ hyaluronic acid capsule?

camouflage the bacteria from host

What is the etiological agent of necrotizing fasciitis and streptococcal toxic shock syndrome?

S. pyogenes

What is necrotizing fasciitis referred to as?

flesh eating disease

True or False. If the statement is False, correct it. 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 infections

What is pyocyanin? What bacterium produces it?

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

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

P. aeruginosa, aka swimmer’s ear, outer ear canal is infected and sometimes pinna, can also become inflamed and exhibit pus-filled lesions

Define necrosis

tissue death

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 are subcutaneous mycoses? Which, if either, are more serious infections?

cutaneous mycoses - fungal skin infections

subcutaneous mycoses - deeper dermal or muscle infections and can be more serious

Define dermatophyte

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

What is the etiological agent that causes many cutaneous mycoses, such 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 the main three fungal genera that cause most tinea infections

Trichophyton, Microsporum, and Epidermophyton

What is the etiological agent of the neglected tropical disease called leishmaniasis? What type of microbe is it? How is it transmitted?

Leishmania parasites, transmitted through the bite of infection sand flies

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

cutaneous - usually painless, form at bite sites and can persist for months or even years

mucocutaneous - lesions develop in mucous membranes of the nose or mouth; it can lead to severe and permanent disfigurement

visceral - spreads throughout the body

What is the cornea of the eye? What is the conjunctiva?

cornea - transparent layer at the front of the eye that covers the iris

conjunctiva - epithelial membrane that covers the eyeball and lines the eyelids

Besides oils, mucus, sugars, what two protective factors are contained in tears? We learned about one of these that is contained in perspiration (sweat) earlier in this chapter

lysozyme and lactoferrin

What is the function of lactoferrin?

binds up free iron which certain microbes need

What is conjunctivitis? What is it commonly known as?

inflammation of the conjunctiva, aka pink eye

What clinical features can distinguish bacterial vs. viral conjunctivitis?

viral - often begins in one eye and spreads to the other, a watery discharge

bacterial - puslike discharge that is often green or yellow, more likely to be swollen

What microbe causes most viral eye infections?

adenovirus

How can neonatal HSV eye infections be contracted?

following 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, and is acquired by vertical transmission at birth

Why are antibiotic drops administered to baby’s eyes after delivery?

because neonatal bacterial conjunctivitis can lead to serious eye damage if not treated

What is the leading cause of preventable microbial blindness worldwide? What is the etiological agent of this infection?

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 United States? Why?

herpetic keratitis because herpes can reoccur

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 keratitis?

Acanthamoeba

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

Onchocerca volvulus, river blindness

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

larvae of this parasitic helminth (worm) then migrate throughout the body, optic nerve and/or cornea