Bacterial and Parasitic Infections of Skin

Question 1

impetigo

Answer 1

yellow crusted skin lesions, near nostrils typically. can spread across face and appear on trunk and limbs. more common in children. very contagious. some cases show severe bullae

Question 2

impetigo etiology

Answer 2

usually a mix of staph and strep. 30% of population is a carrier of staph aureus. carriers may suffer periodic infections or infect others by contact or via fomites

Question 3

impetigo diagnosis

Answer 3

clinical appearance and history. smears from pus may show gram positive cocci. cultures show gram + cocci, either coagulase pos, beta hemolytic, DNAse pos, salt resistent (staph aureus), or coag neg, beta hemolytic, bacitracin sensitive, reactive with group A antiserum (s. pyogenes). bullous impetigo is associated with staph aureus due to exofolatin

Question 4

impetigo treatment

Answer 4

keep area clean and dry. for mild cases, mupirocin ointment topically. severe cases: penicillinase resistant penicillins or amoxicillin with penicillinase inhibitor, or cephalosporins. drug resistant cases get sensitvity report and prescribe accordingly

Question 5

impetigo prevention

Answer 5

cover lesions. isolate infected people. no sharing of clothes. wash hands. treat carriers topically

Question 6

infected piercings/catheters etiology

Answer 6

entry site of foreign materials can be infected by biofilms, that contain large numbers of bacteria. typically these start with the attachment of low-grade pathogens from the normal skin flora that stick to the foreign material. infected sites can include decorative piercings, or catheters, IV lines, shunts, and other medical devices

Question 7

infected piercings/catheters diagnosis

Answer 7

clinical features. lab culture would probably show gram positive cocci, catalase positive, coagulase negative, non hemolytic

Question 8

infected piercings/catheters treatment

Answer 8

remove infected piercing/device. elimination of biofilms by cleaning and antibiotics is not likely to be effective

Question 9

infected piercings/catheters prevention

Answer 9

change all indwelling catheters, IV lines, etc on a regular schedule. use gold or surgical stainless steel for decorative piecrces. not plastic.

Question 10

scabies etiology

Answer 10

sarcoptes scabei- a mite, approximately a half millimeter long with eight legs burrows into the skin and lays eggs. linear lesions which itch severely due to cell mediated hypersensitivity. itching is worse at night, typically on wrists and genitals

Question 11

scabies transmission

Answer 11

personal contact/fomites

Question 12

scabies diagnosis

Answer 12

clinical findings plus mites in skin scrapings

Question 13

scabies prevention

Answer 13

hygiene! change clothes regularly. dont share towels

Question 14

scabies treatment

Answer 14

topical steroids for itching. permethrin to kill mites

Question 15

skin abscesses etiology

Answer 15

abscess is a localized collection of pus. abscesses may be deep or superficial, infected or sterile. typically due to s. aureus, along with multiple non-pathogenic skin bacteria.

Question 16

furunculitis

Answer 16

superficial sweat gland or follicle infection

Question 17

carbuncle

Answer 17

multiple abscesses fused subcutaneously

Question 18

acne

Answer 18

a mixed infection involving increased susceptibility of the skin to infection with small abscesses and superficial inflammation of the surface and sebaceous glands. Propionobacterium acnes is an anaerobic bacterium commonly present at the same time as s. aureus

Question 19

skin abscess diagnosis

Answer 19

clinical appearance and history. smears from pus show mixed bacterial populations, including gram positive cocci. cultures show gram + cocci which are coag pos and beta hemolytic, DNAse pos, salt resistant along with other organisms

Question 20

skin abscess treatment

Answer 20

drain abscess. mupirocin ointment. systemic antibiotics for severe case. nafcillin/oxacillin, alternatively cephalosporins. drug sensitivity testing may be necessary.

Question 21

acne treatment

Answer 21

multiple agents to reduce skin susceptibility as well as multiple empirical topical or systemic antibiotics

Question 22

skin abscess prevention

Answer 22

public health measures. remove carriers from ICU, ORs and nurseries. carrier state can be eliminated by mupirocin ointment to the nares

Question 23

scalded skin syndrom

Answer 23

widespread exfoliation due to a localized infection by s. aureus. the exofoliation toxin causes separation between epidermal cells. usually seen in newborns

Question 24

toxic shock syndrome

Answer 24

systemic immune reaction to the super antigen toxic shock syndrome toxin or streptococcal toxic shock syndrome toxin

Question 25

erysipelas/cellulitis/necrotizing fascitis

Answer 25

beneath the surface of skin spread in a diffuse manner. erysipelas is superficial. cellulitis is deeper and associated with lymphadenopathy, fever, and bacteremia. necrotizing fascitis starts as minor infection and spreads through subcutaneous fascia with widespread necrosis and gangrene.

Question 26

cause of erysipelas/cellulitis/necrotizing fascitis

Answer 26

S. pyogenes. C. perfiringens can be seein in gas gangrene (necrotizing fasciitis)

Question 27

erysipelas/cellulitis/necrotizing fascitis diagnosis

Answer 27

clinical features, cultures from tissue or blood are often negative.

Question 28

erysipelas/cellulitis/necrotizing fascitis treatment

Answer 28

erysipelas and cellulitis: penicillin or cephalosporin. necrotizing fascitis: rapid surgical intervention

Question 29

surgical site infections

Answer 29

usually strep or staph. strep shows signs similar to cellulitis. staph can lead to toxic shock syndrome. excise and drain to treat.

Question 30

post streptococcal nephtitis

Answer 30

analagous to rheumatic fever, but tends to follow skin infections rather than pharyngitis. associated with particular M protein types