21.E: Skin and Eye Infections (Exercises)
21.1: Anatomy and Normal Microbiota of the Skin and Eyes
Human skin consists of two main layers, the epidermis and dermis, which are situated on top of the hypodermis, a layer of connective tissue. The skin is an effective physical barrier against microbial invasion. The skin’s relatively dry environment and normal microbiota discourage colonization by transient microbes. The skin’s normal microbiota varies from one region of the body to another. The conjunctiva of the eye is a frequent site for microbial infection; deeper infections are less common.
Multiple Choice
_____________ glands produce a lipid-rich substance that contains proteins and minerals and protects the skin.
- Sweat
- Mammary
- Sebaceous
- Endocrine
- Answer
-
C
Which layer of skin contains living cells, is vascularized, and lies directly above the hypodermis?
- the stratum corneum
- the dermis
- the epidermis
- the conjunctiva
- Answer
-
B
Fill in the Blank
The ________ is the outermost layer of the epidermis.
- Answer
-
stratum corneum
The mucous membrane that covers the surface of the eyeball and inner eyelid is called the ________.
- Answer
-
conjunctiva
Short Answer
What is the role of keratin in the skin?
What are two ways in which tears help to prevent microbial colonization?
Which label indicates a sweat gland?
(credit: modification of work by National Cancer Institute)
Critical Thinking
Explain why it is important to understand the normal microbiota of the skin.
Besides the presence or absence of ulceration, how do acute ulcerative and nonulcerative blepharitis differ?
21.2: Bacterial Infections of the Skin and Eyes
Staphylococcus and Streptococcus cause many different types of skin infections, many of which occur when bacteria breach the skin barrier through a cut or wound. S. aureus are frequently associated with purulent skin infections that manifest as folliculitis, furuncles, or carbuncles. S. aureus is also a leading cause of staphylococcal scalded skin syndrome (SSSS). S. aureus is generally drug resistant and current MRSA strains are resistant to a wide range of antibiotics.
Multiple Choice
Staphylococcus aureus is most often associated with being
- coagulase-positive.
- coagulase-negative.
- catalase-negative.
- gram-negative
- Answer
-
A
M protein is produced by
- Pseudomonas aeruginosa
- Staphylococcus aureus
- Propionibacterium acnes
- Streptococcus pyogenes
- Answer
-
D
___________ is a major cause of preventable blindness that can be reduced through improved sanitation.
- Ophthalmia neonatorum
- Keratitis
- Trachoma
- Cutaneous anthrax
- Answer
-
C
Which species is frequently associated with nosocomial infections transmitted via medical devices inserted into the body?
- Staphylococcus epidermidis
- Streptococcus pyogenes
- Proproniobacterium acnes
- Bacillus anthracis
- Answer
-
A
Fill in the Blank
A purulent wound produces ________.
- Answer
-
pus
Short Answer
How are leukocidins associated with pus production?
What is a good first test to distinguish streptococcal infections from staphylococcal infections?
21.3: Viral Infections of the Skin and Eyes
Papillomas (warts) are caused by human papillomaviruses. Herpes simplex virus (especially HSV-1) mainly causes oral herpes, but lesions can appear on other areas of the skin and mucous membranes. Roseola and fifth disease are common viral illnesses that cause skin rashes; roseola is caused by HHV-6 and HHV-7 while fifth disease is caused by parvovirus 19. Viral conjunctivitis is often caused by adenoviruses and may be associated with the common cold. Herpes keratitis is caused by herpesviruses.
Multiple Choice
Warts are caused by
- human papillomavirus.
- herpes simplex virus.
- adenoviruses.
- parvovirus B19.
- Answer
-
A
Which of these viruses can spread to the eye to cause a form of keratitis?
- human papillomavirus
- herpes simplex virus 1
- parvovirus 19
- circoviruses
- Answer
-
B
Cold sores are associated with:
- human papillomavirus
- roseola
- herpes simplex viruses
- human herpesvirus 6
- Answer
-
C
Which disease is usually self-limiting but is most commonly treated with ganciclovir if medical treatment is needed?
- roseola
- oral herpes
- papillomas
- viral conjunctivitis
- Answer
-
A
Adenoviruses can cause:
- viral conjunctivitis
- herpetic conjunctivitis
- papillomas
- oral herpes
- Answer
-
A
Fill in the Blank
Human herpesvirus 6 is the causative agent of ________.
- Answer
-
roseola
Short Answer
Compare and contrast bacterial and viral conjunctivitis.
21.4: Mycoses of the Skin and Eyes
Mycoses can be cutaneous, subcutaneous, or systemic. Common cutaneous mycoses include tineas caused by dermatophytes of the genera Trichophyton , Epidermophyton , and Microsporum . Tinea corporis is called ringworm. Tineas on other parts of the body have names associated with the affected body part. Aspergillosis is a fungal disease caused by molds of the genus Aspergillus . Primary cutaneous aspergillosis enters through a break in the skin, such as the site of an injury or a surgical wound.
Multiple Choice
___________ is a superficial fungal infection found on the head.
- Tinea cruris
- Tinea capitis
- Tinea pedis
- Tinea corporis
- Answer
-
B
For what purpose would a health-care professional use a Wood’s lamp for a suspected case of ringworm?
- to prevent the rash from spreading
- to kill the fungus
- to visualize the fungus
- to examine the fungus microscopically
- Answer
-
C
Sabouraud dextrose agar CC is selective for:
- all fungi
- non-saprophytic fungi
- bacteria
- viruses
- Answer
-
B
The first-line recommended treatment for sporotrichosis is:
- itraconazole
- clindamycin
- amphotericin
- nystatin
- Answer
-
A
Fill in the Blank
The most common subcutaneous mycosis in temperate regions is ________.
- Answer
-
sporotrichosis
Short Answer
What yeasts commonly cause opportunistic infections?
Critical Thinking
What steps might you recommend to a patient for reducing the risk of developing a fungal infection of the toenails?
21.5: Protozoan and Helminthic Infections of the Eyes
The protozoan Acanthamoeba and the helminth Loa loa are two parasites that can breach the skin barrier, causing infections of the skin and eyes. Acanthamoeba keratitis is a parasitic infection of the eye that often results from improper disinfection of contact lenses or swimming while wearing contact lenses. Loiasis, or eye worm, is a disease endemic to Africa that is caused by parasitic worms that infect the subcutaneous tissue of the skin and eyes. It is transmitted by deerfly vectors.
Multiple Choice
Which of the following is most likely to cause an Acanthamoeba infection?
- swimming in a lake while wearing contact lenses
- being bitten by deerflies in Central Africa
- living environments in a college dormitory with communal showers
- participating in a contact sport such as wrestling
- Answer
-
A
The parasitic Loa loa worm can cause great pain when it:
- moves through the bloodstream
- exits through the skin of the foot
- travels through the conjunctiva
- enters the digestive tract
- Answer
-
C
A patient tests positive for Loa loa antibodies. What does this test indicate?
- The individual was exposed to Loa loa at some point.
- The individual is currently suffering from loiasis.
- The individual has never been exposed to Loa loa .
- The individual is immunosuppressed.
- Answer
-
A
________ is commonly treated with a combination of chlorhexidine and polyhexamethylene biguanide.
- Acanthamoeba keratitis
- Sporotrichosis
- Candidiasis
- Loiasis
- Answer
-
A
Fill in the Blank
Eye worm is another name for ________.
- Answer
-
loiasis
The ________ is the part of the eye that is damaged due to Acanthamoeba keratitis.
- Answer
-
cornea
Critical Thinking
Why might a traveler to a region with Loa loa worm have a greater risk of serious infection compared with people who live in the region?
What preventative actions might you recommend to a patient traveling to a region where loiasis is endemic?