2/14 Bacterial Skin infections Flashcards by Jullet Han

Agent that causes Impetigo

Staph aureus
Strep (group A - ß hemolytic)
or Both

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Agent that causes Staphylococcal Scalded Skin Syndrome

exfoliatin, ET-A, ET-B produced by Staph aureus (phage II strain)

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Agent that causes folliculitis, furuncles, carbuncles

S. aureus (predilection for hair follicles)

Pseudomonas aeruginosa (hot tub/swimming pool folliculitis)

Yeasts: Candida and Pityrosporum

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Agent that causes MRSA

S. aureus

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Agent that causes Cellulitis

S. pyogenes and/or S. aureus

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Agent that causes Erysipelas

S. pyogenes

H. influenze can cause similar facial infections in non-immunized children

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Agent that causes Necrotizing Fasciitis

Polymicrobial (Strep, S. aureus, E. coli, Bacteroides spp, Clostridium spp)

10% due to group A streptococcus alone

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Agent that causes Lyme disease

Borrelia burgdorferi

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Agent that causes Syphillis

Treponema pallidum

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What is this and what are the forms that are present?

What are some defining features of each? (bacteria caused by each one)

Impetigo

*Non-bullous (crusted)**
S. aureus, and occasionally by Strep (group A, beta-hemolytic)
Moist, honey colored crusts on erythematous base
Fever, systemic symptoms are rare (usually due to Strep, which progresses rapidly from impetigo -> cellulitis -> fever)
May be preceded by skin trauma; located around nose and mouth
Often complicates atopic dermatitis (secondary impetiginization)
*Bullous (Non-crusted)**
caused by S. aureus, phage II, type 71 – produces exfoliatin that produces the bullae)
may arise without obvious trauma
large flaccid bullae may develop and rupture, leaving shiny shallow erosions

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What are some characteristic features of impetigo?

Be sure to touch upon:
age of patients
predisposing factors
contagiousness
source of infection

Young children
Predisposing factors: heat, humidity, crowding, poor hygiene
Occurs year round
Contagious - spreads via direct contact, autoinoculation
Nasal and/or perineal areas may be the source of infection (S. aureus

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How do you diagnose and treat Impetigo? (mild cases, widespread/complicated cases, and recurrent cases)

culture/sensitivities - recommended due to rise of resistant organisms

Mild cases: topical mupirocin

Widespread, complicated cases:

**penicillinase-resistant penicillins
first generation cephalosporin**

Recurrent cases:

treat nares (mupirocin) and body (chlorhexidine)
bleach baths

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What is this? What is it caused by?

SSSS - exfoliatin, ET-A, ET-B produced by S. aureus (phage II strain) circulate systemically and split the skin at the superficial granular layer

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What are some characteristic features of SSSS? (typical patients, prognosis)

Children <6 yo, good prognosis

Immunosuppressed adults, esp. with renal failure (rare), BAD prognosis

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What is the clinical presentation of SSSS?

Site of infection may or may not be apparent
Prodrome of malaise, fever, irritability
skin becomes tender, symmetrical sunburn-like erythema develops around facial orifices, neck, flexures
superficial skin blisters, which sloughs and leaves behind moist skin, scales
heals without scarring 10-14d

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How is SSSS diagnosed and treated?

Diagnosis is primarily based on clinical presentation (cultures are negative because the symptoms are caused by teh exfoliatins that S. aureus secretes!!!)

Trmt:
oral penicillinase-resistant penicillin
1st generation cephalosporin

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What other syndrome must you differentiate SSSS from?

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from toxic epidermal necrolysis (TEN),

drug-induced reaction that causes full thickness skin sloughing that leads to widespread denudation
mucosa is involved, high mortality, treat with burn units +/- IVIg

What is the difference between all of these and what causes it?

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S. aureus (predilection for hair follicles)

Pseudomonas aeruginosa (hot tub/swimming pool folliculitis)

Yeasts: Candida and Pityrosporum

What are some defining characteristics of folliculitis, furuncles, carbuncles? What is it and how are they different? How what are some predisposing factors?

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Bacterial infection (pustules) of hair follicle

Predisposing factors: trauma, maceration, occlusion, diabetes, immunosuppression

depth of infection determines lesion

superficial/small pustules at orifice: folliculitis
entire follicle and surrounding tissue (a red, warm, painful, nodule): furuncle
multiple coalescing furuncles, deep tissues (a really large, bad, ugly, complicated “boil”) carbuncle

How is Folliculitis, furuncles, carbuncles diagnosed and treated?

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furuncles: compression or spontaneous rupture may be enough
Superficial Folliculitis: Topical mupirocin
Abscesses: may rupture or require incision/drainage
widespread involvement or lesions in critical areas or patients: antibiotics

**penicillinase-resistant penicillins (dicloxicillin)
1st generation cephalosporin (culture recommended)**
fluoroquinolone for hot-tub folliculitis
seek and treat for nasal / perineal colonization if recurrent

NOTE: if it is due to community-acquired MRSA (causes very painful, virulent furuncles): **culture it!! **

What is MRSA?

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Methicillin-Resistant Staph Aureus (MRSA) - S. aureus strain that is resistant to penicillinase-resistant penicillins (ie dicloxicillin) and other commonly used oral medications traditionally used to treat staph infections (ie cephalosporin, amoxicillin)

What are 5 characteristics that facilitate the transmission of MRSA?

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

How do you tell a MRSA infection from a non-MRSA infection?

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they are clinically indistinguishable from one another (i.e. a furuncle caused by  an MRSA strain looks like one cause by a non-MRSA staph strain)

How is MRSA treated?

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Sulfonamides (TMP/SMX) and tetracyclines
Clindamycin is an option but some strains are prone to inducible clindamycin resistance
Topical meds (esp to address nasal carriage): mupirocin (Bactroban) or silver-containing compounds.
Chlorhexidine (Hibiclens) scrubs are useful for skin colonization, use as body wash
Bleach baths are cheap and effective

What is this and what is it caused by?

Cellulitis - caused by S. pyogenes and/or S. aureus

How is cellulitis acquired? What does it affect? What can it be complicated by?

- Infection of **deep dermis and subcutaneous tissues** - Infects skin either from **break in the skin** (immunocompetent pts) or **hematogenous spread** (immunosuppressed pts) - damage to **lymphatic system** may predispose to recurrent infections -\> lymphadema - strep cellulitis can be complicated by glomerulonephritis, lymphadentis, lymphatic scarring, endocarditis

What is the clinical presentation of cellulitis? What can occur in children?

- red, warm, painful and swollen - ill-defined - can blister - associated fever, chills, malaise common * *borders are _not_ well demarcated** **streptococcal perianal disease:** recurrent bright perianal erythema in otherwise-healthy children

How do you diagnose and treat cellulitis?

diagnosis is based on **clinical picture** because **cultures are usually negative** ``` oral antibiotics (**penicillinase-resistant pen, 1st gen. cephalosporins**) if systemically ill, consider **IV antibiotics** ```

What is this and what is it caused by?

**Erysipelas** - caused by **S. pyogenes** H. influenze can cause similar facial infections in non-immunized children; requires IV antibiotics

What is the clinical picture of erysipelas?

- Superficial **cellulitis** with **significant lymphatic involvemen**t (lymphadenopathy) - **well-demarcated** painful erythema, usually on face, with **peau d’orange texture** * *- rapidly progressive**

How is erysipelas treated?

penicillin

What is this and what is it caused by?

Necrotizing Fasciitis “Flesh-eating bacteria” Syndrome **Polymicrobial (Strep, S. aureus, E. coli, Bacteroides spp, Clostridium spp)** - 10% due to group A streptococcus alone

What are some of the clinical features of Necrotizing Fasciitis? (trauma? complications/mortality? illnesses that predispose one to this?

- skin trauma may or may not precede symptoms - underlying illnesses predispose including **OH, DM, vascular + cardiac disease** - **complications common**: mortality, deformity, TSS - resembles cellulitis early on, but **pain may be unusually severe**! - progresses rapidly with **necrosis** developing **within 24-36 hrs** - systemic illness can be profound - usually involves **extremities** - **Fournier’s gangrene** - involvement of perineum and genitalia

How is Necrotizing Fasciitis diagnosed and treated?

diagnosis: MRI, surgical exploration treatment: - extensive **surgical debridement** - IV **broad spectrum antibiotics** * *- hyperbaric oxygen** therapy (controversial)

What is this and what is it caused by?

Lyme disease **Borrelia burgdorferi**, a tick-borne illness that is common in the NE

What are some complications of Lyme disease? (4)

- Bell’s palsy - arthritis - myocarditis - meningoencephalitis BAMM wha wha...

What is the clinical presentation of Lyme disease?

**“bulls eye rash” erythema migrans** rash because it enlarges rather than remaining static

How do you diagnose and treat Lyme disease?

**ELISA** test for antibodies followed by Western Blot if positive **Doxycycline** for 10 to 21 days (**amoxicillin** for children and pregnant women)

What is this and what is it caused by?

Syphilis - Treponema pallidum

What are the 4 stages of syphillis and what parts of the body does it affect? What happens if the fetus contracts syphillis from the mother?

**Primary** – **painless chancre** on **genitals**; highly infectious **Secondary** – (4-10wks after chancre) spirochete spreads throughout body; **maculopapular rash** on** palm, soles, and mucous membranes** (most contagious) **Latent** – asymptomatic, but pts may have secondary syphilis skin lesions **Tertiary** – **cardiovascular and CNS** involvement (ie degeneration of DCML columns in spine** -\> TABES DORSALIS)** **Congenital syphilis** – high rates of spontaneous abortion and stillbirth

How is syphillis diagnosed and treated?

Nontreponemal serology: **VDRL, RPR Treponemal test** Non-Treponemal test **- ****Flourescent treponemal antibody-absorpsion (FTA-ABS)** **Penicillin G benzathine** for all stages of syphilis

2/14 Bacterial Skin infections Flashcards

(41 cards)