Module 12: Skin and Eye Infections

Question 1

Skin Defenses

Answer 1

• keratin
• sloughing of skin
• antimicrobial peptides
• sebum
• sweat (lysozyme)

Question 2

Skin Infections Caused by Staphylococcus aureus

Answer 2

• folliculitis
• scaled skin syndrome
• toxic shock syndrome
• HA-MRSA and CA-MRSA

Question 3

Folliculitis

Answer 3

• mild superficial inflammation of the hair follicles or glands
• can lead to an abscess
• furuncle (boil)
• carbuncle

Question 4

Furuncle

Answer 4

• single hair follicle or gland becomes inflamed and progresses into a large abscess

Question 5

Carbuncle

Answer 5

• cluster of furuncles that are interconnected

Question 6

Scalded Skin Syndrome

Answer 6

• affects mostly newborns and babies
• sign and symptoms: large areas of skin peel off or fall away, layer of skin slips off with gentle pressure leaving wet red areas
• pathogenesis: exfoliative toxins A and B, exotoxins enter the bloodstream, toxins cause bulls lesions, slips occurs in epidermal layers
• direct contact and droplet contact
• 30% of adults are asymptomatic carriers
• treatment IV antibiotics

Question 7

Toxic Shock Syndrome

Answer 7

• signs and symptoms: rash which looks like severe sunburn -> peels off after a few days
• pathogenesis: toxic shock syndrome toxin (TSST), superantigen = potent stimuli for T-cells, activates T-cells at a rate 100x greater than ordinary antigens, cause release of cytokines
• treatment IV antibiotics

Question 8

HA-MRSA and CA-MRSA

Answer 8

• healthcare-acquired methicillin resistance Staphylococcus aureus
• community-acquired methicillin resistant Staphylococcus aureus
• encode enzyme called B-lactamase
• virulence factors enzymes expressed: coagulase, hyaluronidase, lipases

Question 9

HA-MRSA

Answer 9

• associated with hospital stays on long term care facilities
• immunocompromised

Question 10

CA-MRSA

Answer 10

• healthy individuals

Question 11

MRSA

Answer 11

• lesions are raised, red and tender
• warm to tough, pus secretion
• consider a serious threat by the WHO

Question 12

Skin Infections caused by Streptococcus pyogenes

Answer 12

• cellulitis
• erysipelas
• scarlet fever
• necrotizing fasciitis

Question 13

Cellulitis

Answer 13

• infection in the dermis and subcutaneous layers of the skin
• tight glossy stretched appearance of skin
• affected area is warm to touch
• pathogenesis: produces hyaluronidase
• treatment: penicillin, cephalexin

Question 14

Erysipelas

Answer 14

• enters through a small wound in face of extremities
• site of entry becomes redder and skin texture like orange peel
• lesions spreads and edge is slightly elevated and warm to touch
• treatment: penicillin

Question 15

Scarlet Fever

Answer 15

• red rash - sand paper texture
• strawberry tongue - sometimes whitish coating
• pathogenesis: erythrogenic toxin is produced, super antigen, production of rash and fever
• treatment: penicillin or cephalexin

Question 16

Necrotizing Fasciitis

Answer 16

• flesh eating disease
• centre of bump may become blackened
• pathogenesis: Exotoxin B, bacteria spreads
• treatment: IV antibiotics, surgery, amputation

Question 17

Viral Skin Infections

Answer 17

• oral herpes
• chicken pox/shingles
• rubella
• measles (covered in assignment)

Question 18

Oral Herpes

Answer 18

• Herpes Simplex 1 Virus (HSV-1)
• vesicles filled with fluid in or around mouth
• pathogenesis: enters through oral mucosa, stays dormant in nerve cells, reactivates and travels to area of cold sore
• very contagious
• no prevention
• treatment: usually self-resolved

Question 19

Chicken Pox/Shingles

Answer 19

• Varicella-Zoster Virus (VZV), human Herpesvirus 3
• itchy rash -> blisters filled with fluid
• pathogenesis: enters respiratory tract and attaches to respiratory mucosa -> blood stream -> skin, causes adjacent cells to fuse and lyse
• contagious until all lesions have crusted over
• virus enter dorsal root ganglion and remains dormant (protect from immune system), then re-emerges as shingles
• transmission: respiratory droplets and fluid of the skin lesions, most contagious a day or two prior to rash development
• prevention: live attenuated vaccines
• treatment: none

Question 20

Rubella

Answer 20

• Rubella virus
• mild rash, joint inflammation and pain
• diagnosis - look for presence of rubella genetic material, or antibodies against rubella
• congenital Rubella, mother can still transmit disease if asymptomatic, first trimester -> miscarriage or permanent defects in a newborn
• pathogenesis: multiplies in respiratory tract -> lymph nodes -> spreads to rest of body; has ability to stop mitosis; induces apoptosis of normal tissue; damages vascular endothelium -> poor organ development
• transmission: contact with respiratory secretions
• prevention: MMR vaccine, live attenuated

Question 21

Skin Mycoses (fungal infections)

Answer 21

• Ringworm
• Tinea versicolor
• chromoblastomycosis

Question 22

Ringworm

Answer 22

• pathogenesis: invade and digest Keratin, can suppress the immune system which allows persistence
• transmission: direct or indirect contact with infected humans/animals
• treatment: topical antifungal

Question 23

Tinea versicolor

Answer 23

• superficial mycoses, outer epidermal surface
• caused by the yeast genus Malassezia
• scaling of skin, discoloured skin pigmentation
• pathogenesis: yeast feeds on the high oil content of the skin glands
• treatment: topical antifungal

Question 24

Chromoblastomycosis

Answer 24

• chronic fungal infection
• subcutaneous mycoses
• papular lesions, which appear first on the extended slowly -> nodular -> large wart-like lesions
• treatment: difficult to treat, Itraconazole

Question 25

Bacterial Infections

Answer 25

• Pseudomonas aeruginosa
• Gas Gangrene

Question 26

Pseudomonas aeruginosa

Answer 26

• most common bacteria to infect wound of burn patients
• virulent factors: proteases (digest proteins), exotoxin A (halts synthesis of proteins), Hemolysin (break down lipids in epithelial cells, bacteria penetrate deeper and spread infection)
• treatment: topical antimicrobial agents, wound excision

Question 27

Gas Gangrene

Answer 27

• caused by Clostridium perferingens
• produces gas in affected tissue (muscle tissue)
• blisters filled with brown-red liquid
• pathogenesis: infection requires damaged or dead tissue, alpha toxin causes RBC to rupture and destroys tissue and generates gas
• Prevention: rigorous cweaingin and surgical repair of deep wounds
• Treatment: antibiotics alone are not effective, excision

Question 28

Eye Infections

Answer 28

• Conjunctivitis (pink eye)
• Keratitis

Question 29

Eye Defenses

Answer 29

• tears
• immunologically privileged

Question 30

Conjunctivitis (Pink Eye)

Answer 30

• inflammation or swelling of the conjunctiva
• bacteria -> milky discharge
• viral -> clear watery discharge

Question 31

Neonatal Conjunctivitis

Answer 31

• passed from mother to child
• treatment: antibacterial eye drops

Question 32

Keratitis

Answer 32

• inflammation of the cornea
• invasion of deeper eye tissues
• can lead to complete corneal destruction
• herpes simplex type 1 or protozoa Acanthamocba (people who wear contact lenses)
• gritty feeling in eye
• sharp pain
• sensitivity to light
• treatment: topical trifluoride +/- oral acyclovir