02-14 Bacterial Skin Infections

Question 1

Normal Skin Flora

Answer 1

Fxn: functions largely to prevent skin infections

Common examples

• Staphylococcus epidermidis - most common coccus on skin
• Corynebacterium spp. common in intertriginous areas.
• Propionibacterium spp. in sebaceous glands.
• Gm-neg bacteria in the axillae and perineum.
• Yeasts (Pityrosporum spp.) are found on skin rich with sebaceous glands.

Question 2

Dx?

• Causative organism?
• Mechanism of spread?
• Describe typical presentation of subtypes
• Contagious?
• Tx
• Complications

Answer 2

Dx = impetigo

• Organism = S. aureus, group A (ß-hemolytic) strep, or both
  
  • nasal, subungal and perineal colonization may serve as source of infx (S. aureus)
• Spreads via direct contact or auto-innoculation; usually kids
  
  • year-round; heat, humidity, crowding, poor hygiene predispose but not req’d
• Presentation
  
  • non-bullous: moist honey-crust on erythematous base around mouth, nose, extremities; usually Staph a.
    
    • often s/p minor traum
    • usu no systemic sx
    • may itch
  • Bullous [seen here]: yellow, fragile vesicles, surrounding skin intact
    
    • often occurs w/o obvious trauma
    • exfoliatin producing S. aureus
• Yes, it is contagious!
• Tx: abx coverage for staph and strep
  
  • mildcases: topical mupirocin 2% (bacitracin if no insurance)
  • wide spread/complicated: penicillinase-resistant pens or 1st gen cephalosporins
  • recurrent: treat nares (mupirocin) and body (chlorhexidine or bleach baths (1/2 cup in bathtub for 15 mins)
• Complications: most cases uncomplicated
  
  • may progress to ecthyma (deeper infx) w/o tx
  • staph scalded skin syndrome from toxin-producing staph
  • Glomerulonephritis (but not rheumatic fever) can complicate G.A.S. impetigo
    
    • abx do not prevent nephritis

N.B. : other lesions can be 2°ly impetiginized (e.g. HSV ulcer → ask “how often does this happen, q few months?”)

Question 3

Dx?

• Cause?
• Dx options
• Prognosis
• DDx - how to differentiate

Answer 3

Staph Scalded Skin Syn

• Cause: usu. S. aureus, phage group II strains produce exfoliatin that circulate systemically
  
  • split the skin at superficial granular layer
• Clinical Picture: usu kids < 6 y/o; when in adults usu w/ immunocomp e.g. renal failure
  
  • site of infection may/may not be apparent
  • prodrome of malaise, fever, irritability
  • skin tender → symmetrical sunburn-like erythema around facial orifices, neck, flexures → superficial blisters → sloughs leaving behind moist skin, scales
    
    • heals w/o scarring 10-14d
• Dx: usu. clinical dx; cultures can be negative; if culturing go for nares, conjunctiva, small foci of infection (pustules, etc)
• Prognosis
  
  • good in healthy children (mortality 3%),
  • bad in adults (over 50% all adults, up to 100% in adults with underlying diseases)
• DDx: SSSS vs. TEN (toxic epidermal necrolysis)
  
  • Biopsy: TEN is full thickness vs SSSS is partial thickness
  • TEN presentation different:
    
    • usu drug rxn
    • full thick. sloughing → widespread denudation
    • mucosae involved
    • high mortality – treated in burn units +/- IVIg

Question 4

Dx

• Causative Organism
• Predisposing factors
• Names by depth

Answer 4

Folliculitis

Causative Organism

• Usu. S. aureus: predilection for hair follicles
  
  • MRSA: very painful
• Occas. gram-neg
  
  • “hot tub” → Pseudomonas)
  • Gm neg folliculitis: pts on tetracycline → elimination of facial Gm(+)s, overgrowth of Gm(-)s
• Rare: Candida, Pityrosporum (yeasts)

Predisposing Factors

• trauma, maceration, occlusion, diabetes, immunosupp

Names by depth

• Folliculitis: small pustules at orifice
• Furuncle: involves entire follicle and surrounding tissue (a boil)
  
  • rubor, calor, dolor and tumor
• Carbuncle: multiple coalescing furuncles, deep into subQ

Treatment

• Superficial folliculitis: topical mupirocin and antibact soap
• Widespread or immunosuppressed or prosethic valves
  
  • PO/IV penicillinase-resistant penicillins, 1st gen cephs (culture rec’d).
• Hot tub: cipro or acetic acid soaks
• Furuncles: compresses, spont rupture may be enough may need incision and drainage

Question 5

MRSA

• Presentation
• Tx

Answer 5

Culture results should guide abx therapy

• Simple furuncles: incision & drainage alone
• Most community-acquired strains are sensitive to sulfonamides (TMP/SMX) and tetra(doxy,mino)cycline*
  
  • don’t use w/ kiddos b/c stains teeth
• Clindamycin, but some strains are prone to inducible clindamycin resistance
• Topical meds: mupirocin (Bactroban) or silver-containing compounds.

Preventing Recurrence

• Chlorhexidine (Hibiclens) scrubs are useful for skin colonization, use as body wash
  • Bleach baths are cheap and effective
  • Nasal carriage needs to be addressed (treat with mupirocin)

Question 6

CDC’s Five C’s of MRSA Transmission

Answer 6

• Crowding
• Frequent Skin-to Skin Contact
• Compromised Skin (cuts, abrasions)
• Contaminated surfaces and other items
• Lack of Cleanliness

Question 7

Cellulitis

• Organism(s)
• Where is the infection
• Describe lesion/dx
• Predisposing Factors
• Tx
• Complications

Answer 7

Cellulitis

• Organism(s): usu S. pyogenes and/or S. aureus
• Where is the infection: deep dermis/subQ
• Describe lesion/dx: usu. clinical dx; blood culture usu. negative
  
  • “rubor, calor, dolor and tumor”
  • ill-defined
  • Vesicles and bullae
  • associated fever, chills, malaise is common.
• Predisposing Factors:
  
  • Lymphatic damage (i.e. post resection) leads to recurrent infx in drainage area
  • Skin break usu. responsible in immunocomp pts
  • can be blood borne origin in immunosupp’d pts
• Tx: PO abx (penicillinase-resistant pen, 1st gen. cephalosporins) x 10-14d
  
  • If systemically ill or immunosuppressed, consider IV abx
• Complications
  
  • streptococcus (S. pyogenes) cellulitis can be complicated by glomerulonephritis, lymphadentis,
    lymphatic scarring, endocarditis
  • streptococcal perianal disease: recurrent bright perianal erythema in otherwise-healthy
    children;
    
    • may also occur in the intertriginous areas such as the neck.

Question 8

Dx?

• Organism?
• Clinical picture (vs. DDx)
• Tx
• In kids?

Answer 8

Erysipelas

• usually caused by S. pyogenes
• distinctive clinical picture: more superficial cellulitis with significant lymphatic involvement
  
  • rapidly progressive, well-demarcated (vs. ill-defined in cellulitis), painful erythema, usually on face, peau d’orange texture. Associated systemic symptoms, lymphadenopathy
• treatment with penicillin x 10-14 d

**Hemophilus influenza can cause similar facial infection in non-immunized children

• requires IV antibiotics

Question 9

Necrotizing Fasciitis

• Organism(s)
• Where is the infection
• Describe lesion/dx
• Predisposing Factors
• Tx
• Complications

Answer 9

Cellulitis

• Organism(s): usu polymicrobial incl strep, S. aureus, E. coli, Bacteroides spp, Clostridium spp
  
  • Often becomes anaerobic 2° to compartment syndrome
• Where is the infection: down to fascia layer
• Describe lesion/dx: Dx w/ MRI, surgical exploration
  
  • resembles cellulitis early on: pain unusually severe
  • progresses rapidly with necrosis developing within 24-36 hrs: blue-grey skin, blisters, thin watery discharge
  • systemic illness can be profound – usually involves extremities
• Predisposing Factors
  
  • Trauma may or may not contribute
  • underlying illnesses (alcoholism, DM, vascular dz, cardiac dz)
• Tx: extensive surgical debridement, broad spec IV abx, IVIG, hyperbaric O2 controversial
• Complications common, include death, deformity, toxic shock syndrome
  
  • Mortality: 20-40%
  • involvement of perineum and genitalia = Fournier’s gangrene [SEEN HERE]

Question 10

How do you call this?

Answer 10

furuncle

Question 11

How do you call this?

Answer 11

carbuncle

Question 12

Dx?

• Name lesion
• Organism(s)
• Presentation/Course
• Dx
• Tx
• Complications

Answer 12

Lyme Disease

• Lesion name: Erythema migrans b/c it enlarges rather than being static
• Causative Organism: Borrelia burgdorferi
  
  • Vector: deer (Ixodes spp) tick
• Presentation/Course: incubation period usually 1 to 2 weeks, but canbe 3-30 days.
  
  • First sign usu = “bulls-eye” rash in 70-80% of pts
  • starts small, then expands over several days
• Dx: ELISA for Abs followed by Western Blot if (+)
  
  • False negs possible if tested early dz (false positives if late)
• Tx: many abx options: doxycycline common
• Complications
  
  • Bell’s palsy
  • arthritis
  • meningitis
  • other neuro sx
  • carditis and arrhythmias

Question 13

Dx?

• Causative Organism
• Transmission by?
• Presentation by stages
• Dx options
• Tx
• Complications

Answer 13

Syphilis (2° on front of card; 1° penile here)

• Causative Organism: Treponema pallidum
• Transmission by: sexual contact, mother to fetus in utero, blood transfusion, skin contact w/ damage skin
• Presentation by stages
  
  • Primary: painless, punched out chancre, wicked infectious
  • Secondary: 4-10 wks s/p chancre (spirochetes spread throughout body & in skin lesions)
    
    • malaise/feel crummy
    • Palms, soles, muc. membranes (most contagious)
    • Diverse in morphology – reddish brown macules, papules, pustules, annular and scaly.
    • Condyloma lata – grey white mucous membrane lesions, painless and alopecia “moth eaten”
  • Tertiary: primarily affects cardiovascular and CNS
• Dx options:
  
  • non-treponemal (VDRL and PRP)
  • Treponemal: confirms (+) or equivocal nontreponemal test (eg. Fluorescent
    treponemal antibody-absorption (FTA-ABS))
• Tx: Pen G benzathine for all stages
• Complications: neurosyph, etc.

Question 14

Congential Syphilis (not in slides but in notes) FYI

Answer 14

• High rates of spontaneous abortion and stillbirth
• Cutaneous findings similar to adult secondary syphilis
• Snuffles – mucopurulent rhinitis

Later manifestations

• Saddle nose – due to destruction of the nasal septum
• Saber shins – bowing of the tibia
• Clutton’s joints – inflammation of knee joints.
• Hutchinson’s teeth – widely spaced and notched incisors
• Mulberry molars – molars have too many cusps.