Bacterial skin infections and dermatophytes

Question 1

Propionibacterium acnes

Answer 1

Gram-positive

Anaerobic, nonmotile, pleomorphic rod

Question 2

Gram + coagulase + cocci

Answer 2

Staph aureus

Question 3

What toxin is responsible for bullous impetigo?

Answer 3

exfoliation toxin (ET digests intracellular connections)

Question 4

Cause of cellulitis
Pleomorph, HA SSTI (EMERGING INFECTION!!!)
Associated with previous trauma/surgery

Answer 4

Acinetobacter baumannii

Question 5

Coccobacillus associated with cat or dog bite

Answer 5

Pasteurella multocida

Question 6

Bacillus associated with FRESH water injuries

Answer 6

Aeromonas hydrophilia

Question 7

Vibrio associated with SALT water injuries

Answer 7

Vibrio vulnificus

Question 8

Causitive agent of myonecrosis is spore-forming, gram-positive anaerobic bacillus. What is it?

Answer 8

Clostridium perfringens type A

Question 9

What is the VF found in CP type A? What is it responsible for?

Answer 9

Alpha-toxin = Phospholipase C

-Lyses RBCs, myocytes, fibroblasts, platelets, leukocytes

Question 10

Crepitant skin, sweet mousy smell (cut hay), fever, tachycardia. Causitive agent? Key VF?

Answer 10

C. Perfringens, alpha toxin

Question 11

What is the most common causitive agent of tinea capitis? Treatment of choice?

Answer 11

M. canis; Systemic griseofulvin

Question 12

What are the most common causitive agents of t. pedis?

Answer 12

E. floccosum, T. mentgrophytes, and

T. rubrum

Question 13

What does tinea unguium usually have involved as well?

Answer 13

systemic candida

Question 14

What are the most common causitive agents of tinea cruris?

Answer 14

T. mentagrophytes, T. Rubrum, E. Floccosum, and M. Canis

Question 15

Causitive agent of tinea versicolor? What does it look like microscopically?

Answer 15

Malassezia furfur; “spaghetti and meatballs”

Question 16

Tx of tinea versicolor

Answer 16

Topical selenium sulfide, miconazole

Question 17

Dimorphic species (yeast and mold) Can grow in saturated salt solutions. What is the causitive agent and what is the name of the infection?

Answer 17

Hortaea werneckii; tinea nigra

Question 18

How is sarcoptes scabiei (mites) reproduced?

Answer 18

female is fertilized on the skin surface and burrows deep in skin, eggs will mature in skin and adult mites will appear in 2 weeks

Question 19

When are symptoms of scabies more noticeable?

Answer 19

AT NIGHT

Question 20

What population is crusted scabies found in? How is pediatric scabies different?

Answer 20

HIV infection; similar to crusted lesions except possibly blood filled

Question 21

How do you ID scabies?

Answer 21

Mineral oil scrapings and microscopy

Question 22

Pubic lice

Answer 22

Phithirus pubis

Question 23

human lice. What is different about it?

Answer 23

pediculus humanus; LARGER than scabies and p. pubis

Question 24

What can result from years of infestation with p. humanus?

Answer 24

“Vagabond’s disease” =darkened, thickened skin