Bacterial Skin infxns

Question 1

Localized abscesses

Answer 1

Staph aureus

Question 2

Spreading infections

Answer 2

Step pyogenes

Question 3

Non-inflam acne vulgaris

Follicle opening partially obstructed, filled with sebum, keratinocytes, hair

Answer 3

Microcomedo

Question 4

Primary pathogens of folliculitis (to differentiate from acne)

Answer 4

Staph aureus g+
Pseudomonas aeruginosa g-
(pyocin, pyoverdin)

Question 5

Enlarged folliculitis eruptions that extend into dermis and subcutaneous tissue

Answer 5

Furuncles/boils

neck, ass-cheeks, face

Question 6

Massive inflammation involving several hair follicles extend into dermis and subcutaneous tissue

Answer 6

Carbuncles

neck, back, thighs

Question 7

Staph aureus
Strep pyogenes
GABHS
Can be a/w glomerulonephritis

Answer 7

Nonbullous impetigo
(amber colored crust, aka honey colored crust)

(NOT a/w rheumatic fever)

Question 8

Staph aureus
Rare
Have localized action of Exfoliatin Toxin that interferes with intercellular connections

Answer 8

Bullous impetigo

Question 9

> 90% of cases are staph aureus or pyogenes
Acute inflammation of subcutaneous connective tissue
HEET, looks like localized sunburn

Answer 9

Cellulitis

HEET - heat, erythema, edema, tenderness

Question 10

CellulitisL infection of subcu connective tissue:
Emerging infection, pleomorph
A/w preious trauma or surgery

Answer 10

Acinetobacter baumannii

Question 11

CellulitisL infection of subcu connective tissue:Coccobacillus a/w CAT or dog bite

Answer 11

Pasteurella multocida

Question 12

CellulitisL infection of subcu connective tissue:Bacillus a/w fresh water injuries

Answer 12

Aeromonas hydrophilia

Question 13

CellulitisL infection of subcu connective tissue:Vibrio a/w salt water injuries

Answer 13

Vibrio vulnificus

Question 14

CellulitisL infection of subcu connective tissue:

If minimal pain, confined to small area, no risk factors for serious illness

Answer 14

NO LAB WORKUP

Question 15

CellulitisL infection of subcu connective tissue:

If spreading or large area involvement, must confirm cellulitis and not NF

Answer 15

Lab workup:
Cultures of blood, pus, bullae
MRI, CT, US, Xray

Question 16

Avoid NSAIDs in cellulitis

Answer 16

May mask pain indicators of worsening disease (NF, myonecrosis)
Affect immune response
-Inhobit PMN response
-Interfere with cytokine release

Question 17

Type 1 - Polymycrobic NF

Answer 17

At least one facultative aerobe (PESSKEYs) and 1 anaerobic bacterium
Risk factors: DM, surgery, immune compromise

Question 18

Type 2 NF - Flesh eating bacteria

Answer 18

Group A strep pyogenes
(monomicrobic)

No risk factors, can follow small trauma like bug bite, IVFU, blunt trauma

Question 19

Infection of deeper tissues: muscle fascia and overlying subQ
Spreads along fascia (poor blood supply)
Muscle tissue spared
Pain out of proportion to phys exam

Answer 19

Necrotizing fasciitis

*Clue: cutaneous anesthesia precedes skin necrosis

Question 20

NF- putrid odor

Answer 20

only with anaerobic pathogen (type 1)

Question 21

To differentiate btwn cellulitis and NF

Answer 21

Failure to respond to antibiotic therapy (bcz poor blood supply)
Cellulitis would respond in 24-48 hours

Question 22

Dx of NF

Answer 22

Surgery only way to confirm presence and extent
Initial extent detected by MRI, CT
Gram stain and culture from tissue bx
Rapid stress test

Question 23

Myonecrosis - Gas Gangrene
Medical emergency
sudden onset of pain, bronze appearance

Answer 23

C. perfringens type A
spore forming gram +
Gram variable in wound
(sweet, mousy smell)

Question 24

Virulence factor for myonecrosis

Answer 24

Alpha toxin - phospholipase C

Question 25

Dx of Myonecrosis - Gas Gangrene

Answer 25

Tissue bx: Criterion standard | Gram stain of bx shows gram variable rods with ABSENCE of PMNs