Kozel: Skin and Soft Tissue Infections II

Question 1

Gram positive bacillus
Aerobic and facultative anaerobe
Spore former
200 species

Answer 1

Bacillus spp.

Question 2

What is unique about the capsule of Bacillus spp? What is its role?

Answer 2

it is a polypeptide (poly-D-glutamic acid) capsule instead of a polysaccharide capsule;
it is antiphagocytic and induces protective immunity

Question 3

What type of toxin is associated with Bacillus spp?

Answer 3

A-B type toxin

Question 4

What are the three antigens on the Bacillus toxin?

Answer 4

Protective antigen - induces protective immunity
Lethal factor - produces cell death
Edema factor - produces edema

Question 5

Follows inoculation with spores

Painless papule progresses to ulcer to necrotic black eschar (malignant pustule)

Answer 5

cutaneous anthrax

Question 6

Follows ingestion of spores

Local infection that may spread to systemic disease

Answer 6

GI anthrax

Question 7

Follows inhalation of spores
Lungs → regional lymph nodes → systemic spread
Hypotension, pulmonary edema, massive bacteremia, acute fatal toxic shock
May have prolonged incubation period
Fatal if untreated

Answer 7

Inhalation anthrax

Question 8

What type of specimen would you obtain for Bacillus infection?

Answer 8

blood or material from eschar

Question 9

What would you see on the blood culture of Bacillus spp?

Answer 9

gram-positive rods in chains, capsule can be seen via negative stain

Question 10

Bacillus infection is primarily a disease of (blank); humans are normally infected by exposure to (blank) or (blank) products

Answer 10

herbivores; animals; animal

Question 11

Is there a human vaccine for anthrax?

Answer 11

yes, there is also a live vaccine for animals

Question 12

What is the treatment for antrax poisoning?

Answer 12

ciprofloxacin
there is also a potential for monoclonal antibodies to protective antigen

**can use prophylaxis for exposed individuals or vaccinate with AVA

Question 13

Gram-positive bacillus
Anaerobic
Spore-formers
Ubiquitous in soil, water, sewage
Normal flora of GI tract of man and animals
Produce numerous toxins

Answer 13

Clostridium spp.

Question 14

What is the major lethal toxin produced by C. perfringens in gas gangrene? What does this toxin do?

Answer 14

alpha toxin; lecithinase, lyses numerous host cells and causes massive hemolysis

Question 15

This is another toxin released by C. perfringens when cells undergo sporulation
Altered membrane permeability – loss of fluids and ions
Superantigen

Answer 15

enterotoxin

Question 16

What 3 diseases can be caused by Clostridium perfringens infection? What are the symptoms of each?

Answer 16

Cellulitis and gas gangrene: spores introduced by trauma or surgery, causes intense pain, muscle necrosis, shock and renal failure

Food poisoning: ingestion of contaminated meat leads to ab cramps and watery diarrhea

Necrotizing enteritis: ingestion of contaminated meat leads to necrosis of the small intestine

Question 17

Where is Clostridium perfringens found?

Answer 17

ubiquitous in soil, water, and human GI tract

Question 18

What is the treatment for C. perfringens?

Answer 18

for soft tissue infections: rapid treatment necessary, surgical debridement as needed and high dose penicillin + clindamycin

for food poisoning: antibiotics not effective, symptomatic treatment

Question 19

Weakly gram-negative, motile, spirochete

Complex nutritional requirements; can be grown in culture

Answer 19

Borellia burgdorferi

Question 20

What occurs during the early localized infection in Lyme disease? Early disseminated disease? Late in infection?

Answer 20

early localized infection: incubation period of 3-30 days, characteristic skin lesion (erythema migrans) at site of initial infection

early disseminated disease: days to weeks after onset of erythema migrans, multiple secondary annular skin lesions, fatigue, arthritis, myalgia, cardiac dysfunction

late infection: months after initial infection, more extensive arthritis, chronic skin involvement and neuro symptoms

Question 21

What occurs with post-Lyme disease syndrome?

Answer 21

symptoms similar to chronic fatigue syndrome or fibromyalgia

Question 22

What is acrodermatitis chronica atrophicans?

Answer 22

bluish-red skin lesions

occur in late, disseminated stage of lyme disease

Question 23

When diagnosing Lyme disease, what do you look for?

Answer 23

erythema migrans (5cm)

or

at least one late manifestation (musculoskeletal, CNS, or cardiovascular) + lab confirmation

Question 24

What is the lab test of choice for diagnosing Lyme disease?

Answer 24

antibody detection
IgM peak after 6-8 weeks
IgG peak after 4-6 months

Question 25

What is the vector for Lyme disease? What is the reservoir?

Answer 25

hard ticks (nymph stage causes >90% of cases); white footed mouse or white-tailed deer

Question 26

Where is Lyme disease seen in the US?

Answer 26

NE and mid-Atlantic states, upper midwest and Pacific west

Question 27

What is the drug of choice for Lyme disease?

Answer 27

doxycycline for early disease | IV ceftriazone for recurrent arthritis or CNS/PNS disease

Question 28

Gram-negative rods Aerobic Obligate intracellular parasites – grow only in cytoplasm of eukaryotic cells Maintained in animal and arthropod reservoirs and transmitted by arthropod vectors Humans are accidental hosts

Answer 28

Rickettsia

Question 29

Rickettsia replicates in cytoplasm/nucleus of (blank) cells; causes (blank) due endothelial cell damage and leakage of blood vessels

Answer 29

endothelial; vasculitis

Question 30

How does Rickettsia present clinically?

Answer 30

7 day incubation after bite high fever, headache, malaise macular rash w centripetal spread which becomes petechial complications include pulmonary, CNS, renal or cardiac abnormalities

Question 31

What are two methods of antibody detection for Rickettsia?

Answer 31

Weil-Felix test: detects antibodies that cross-react with a Proteus antigen Indirect immunofluorescnece: detects ab against outer membrane protein and LPS**

Question 32

What is the principal reservoir and vector for Rickettsia? Where is it found?

Answer 32

ticks; throughout the US

Question 33

Treatment for Rickettsia?

Answer 33

doxycycline **early treatment is critical

Question 34

What do the following cause? Orientia tsutsugamushi? Rickettsia prowazekii? Rickettsia typhi? What symptoms are common to all?

Answer 34

scrub typhus *sudden onset epidemic typhus *sudden onset murine endemic typhus *gradual onset **fever, headache, myalgia, maculopapular rash

Question 35

Gram-negative, facultatively anaerobic rod with bipolar staining Member of Enterobacteriaceae Zoonotic disease Enormous historic importance

Answer 35

Yersinia pestis

Question 36

How does bubonic plague present clinically? How is it transmitted?

Answer 36

incubation period of <7 days after FLEA BITE; high fever, painful inflammatory swelling of lymph nodes; high mortality if untreated

Question 37

How does pneumonic plague present clinically? How is it transmitted?

Answer 37

incubation period of 2-3 days after AEROSOL EXPOSURE; initially headache, malaise and pulmonary signs; high mortality in untreated

Question 38

How do you make a lab diagnosis of Yersinia?

Answer 38

culture a sample of blood, bubo aspirate, sputum

Question 39

What are the natural hosts for Yersinia pestis? How is it transmitted?

Answer 39

rats, squirrels, rabits; flea bite transmission

Question 40

What is the drug of choice for plague?

Answer 40

streptomycin **doxycycline could be used alternatively

Question 41

molds that invade stratum corneum of skin or other keratinized tissues

Answer 41

dermatophytes

Question 42

3 major genera of dermatophytes

Answer 42

Trichophyton Microsporum Epidermophyton

Question 43

What are the following? ``` Tinea pedis Tinea cruris Tinea corporis Tinea capitis Onchomycosis ```

Answer 43

``` Tinea pedis: athletes foot Tinea cruris: jock itch Tinea corporis: infection of arm, legs, trunk Scalp ringworm infection of nails ```

Question 44

There are anthrophilic, zoophilic, and geophilic species of dermatophytes. Which species cause chronic, relatively noninflammatory infections and are difficult to cure? Which species cause profound host reaction, high inflammatory lesions, and respond well to therapy

Answer 44

anthropophilic; zoophilic/geophilic

Question 45

How do you diagnose dermatophyte infection?

Answer 45

take a sample of the scraping or clipping and dissolve the tissue with KOH, examine microscopically for hyphae you can also culture the scrapings, but it takes weeks

Question 46

What do you use to treat dermatophytes?

Answer 46

topicals for locolized infections, azoles or terbinafine | oral agens for more extensive infection, itraconazole, fluconazole, terbinafine

Question 47

What is pityriasis (tinea) versicolor?

Answer 47

it is caused by Malassezia furfur (budding yeast like cells) which cause small hypo or hyper-pigmented macules (depending on skin color)

Question 48

What does pityriasis versicolor look like on a KOH mount?

Answer 48

spaghetti and meatballs | yeast + hyphal elements

Question 49

How do you treat pityriasis versicolor?

Answer 49

topical azoles or selenium sulfide shampoo | oral azoles for widespread infection

Question 50

Classic infection follows traumatic inoculation of soil or vegetable matter; termed “rose gardener's disease” Small nodule at site of inoculation; may ulcerate Secondary nodules along lymphatics that drain primary lesion

Answer 50

Lymphocutaneous sporotrichosis

Question 51

What is the dimorphic fungus responsible for lymphocutaneous sporotrichosis?

Answer 51

Sporothrix schenckii

Question 52

Why is lymphocutaneous sporotrichosis considered "rose gardener's disease?"

Answer 52

because sporothrix schenckii grows on soil, plants, and decaying vegetation **seen w florists, rose gardener's, greenhouse workers

Question 53

What do you use to treat sporotrichosis?

Answer 53

itraconazole

Question 54

Localized, chronic, granulomatous process involving cutaneous and subcutaneous tissues Multiple granulomas and abscesses containing masses of hyphae Abscesses drain through skin; may extrude granules of hyphae May destroy muscle and bone locally

Answer 54

mycetoma

Question 55

What causes mycetoma?

Answer 55

multiple filamentous fungi: Curvularia, Fusarium, Exophiala, etc

Question 56

What will you see in the exudate of mycetoma?

Answer 56

grains or granules

Question 57

What is the only definitive treatment for mycetoma?

Answer 57

amputation