Skin infections Flashcards by Daniel Kruger

What is folliculitis? What is it mostly caused by? Tx?

Folliculitis
- inflammation/infection of the hair follicle
- Mostly caused by staph>strep
- Erythematous pustule involving the hair follicle
- Treat with warm compress - avoid systemic abx.

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What are furnuncles? What usually causes them? Treatment?

Furnuncles are boils
Usually involve entire hair follicle and surrounding soft tissue
Single abscess
Staph aureus is the usual organism
Treat with I&D and warm compress
Abx
- Keflex (cephalexin) - non MRSA
- Doxycylcine - good MRSA coverage
- tetracycline

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What are carbuncles? What usually causes them? Tx?

Carbuncles are a coalesence of furnuncles
Multiple drainage points
mainly casued by staph aureus
Tx: I&D and systemic abx
- Cefalexin (1st gen cephalosporin) and trimethoprim/sulfamethaoxazole (Batrim) (Sulfas, cover gram - and MRSA coverage)
- Follow up 1-3 days and then weekly.
Pus under pressure!

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What is erysipelas? what usually causes it? Most common portal of entry? Treatment?

Infection of the dermis
Usually caused by B-hemolytic strep
Erythema clasically shiny, well demarcated
Fever, chills common
Facial cheek is common site of infection
Treatment
- Vancomycin 15mg/kg
- follow up? –> going to be admitted into the hospital.

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What is cellulitis? What is it usually caused by? Most common portal of entry? How do you treat it?

Cellulitis is a diffuse spreading infection of the epidermis, dermis, and subcutaneous (connective tissue)
Usually present on the lower leg
Most commonly due to gram positive cocci - staph and strep
Most common portal of entry - Toe fissures or tinea pedis
- Can be very seious in diabetic patients
  - can turn pre-septic and septic quickly
Can affect all layers of the skin
- Generally starts as small patch of eythema with spread over hours
Symptoms
- swelling, pain, erythema
- septic appearence
  - fever, not feeling well.
treatment?
- Good empiric choices for outpatient
  - Keflex (cephalexin) 1st generation cephalosporin. Non MRSA
    - or ceftaroline (Teflaro) for MRSA
  - Trimethoprim/sulfamethoxazole (bactrim) Sulfa- MRSA coverage
  - Penicillins
  - B-lactam inhibitors (Augmentin Amox/Clav, Zosyn Piper/tazo, Unasyn amp/sulbactam)
  - Tetracyclines - Doxycycline (MRSA)
  - Vancomycin (MRSA) - glycopeptide
  - Azithromycin (Macrolide) - Sanford
  - outpatient follow up in 1-2 days - want quickly as possible because of posibility of going septic
- Patient is hospitalized?
  - Pt hospitalized when becomes febrile

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What are necrotizing skin and soft tissue infections? What is first line treatment?

Necrotizing fasciitis
Fournier’s gangrene - gangrene of the genetalia
Gas gangrene
Surgical emergenceis - treatment for all of the above is SURGERY FIRST THEN ABX

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Necrotizing fasciitis, def, how do you diagnose? What layer of tissue does it spare? Treatment?

Definition
- Very rapid progression of an infection that progresses minutes to hours.
- Quickly and progressively destroys subcutaneous fascia
  - “flesh eating”
  - Bullae, and crepitus of the skin from gas under skin
    - SPARES MUSCLE - can help you ddx between gas gangrene.
Cause
- Usually group A strep (Mprotein) but can be staph aureus)
tx?
- SURGERY FIRST AND THEN ABX

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Fournier’s Gangrene, def, cause, treatment?

Definition
- another necrotizing skin infection.
- Rapidly progressing cellulits/gangrene of the penis and scrotum - can happen in women too
- diabetes, alcohol useage, HIV, obesity, and malginancy predispose people to the infection
s/s
- Insidious onset with itching and discomfort near portal of entry - perianal.
- pain out of proportion to appearnce at first
- Worsening - pain subsides due to necrosis of nerve tissue during progression
cause
- Usually polymicrobial with high likelihood of anaerobic organisms
tx
- surgical and then broad spectrum abx until cultures are back
  - vancomycin (glycopeptide), piperacillin/tazo (Beta-lactam inhibitor, Zosyn), metronidazole (Nitroimidazole, flagyl)

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Gas gangrene, def, cause, treatment?

Def

Also known as clostridial myonecrosis
Progressively destroys subcutanoeus fascia, fat and muscle

s/s

often acute presentation with severe pain-sometimes painless due to nerve damage- crepitus

cause

Usually caused by clostridium perfringens
Often from traumatic wounds/perforation of bowel

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Staph Aureus pathogenicity, bacterial surface components and extracellular proteins.

Bacterial surface components
- capsular polysaccharide
- protein A
- clumping factor
- fibronectin binding protein
Extracellular proteins
- coagulase
- hemolysins
- enterotoxins
- toxic -shock syndrome toxin
- exfloiatins
- Pranton-Valentine leukocidin (PVL)
  - Unique to MRSA, allows it to penetrate intact skin.

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Staph Aureus Resistance mechanisms

By definition - harbors mecA gene for methicillin resistance
mecA gene codes for a different type of penicillin -binding protein
This PBP allows continual synthesis of cell wall in presence of B-lactam antibiotics
- Only 5th gen cefalosporins have ability to kill MRSA in cefalosporin family.

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Traditional risk factors for MRSA

Previous hospital stay
Prolonged length of stay prior to infection
surgical procedures (2-3 months)
Enteral feeding
Prior antibiotic use
- 3rd generation cephalosporins
- fluroquinolones
- vancomycin

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Clincal concerns with CA-MRSA. Populations with CA-MRSA

They cause syndromes not typically associated with S.aureus
- Necrotizing fasciiits
- purpura fulminans
- necrotizing pneumonia
- larger community outbreaks - especially in specific populations.
Populations
- children, jail, military, native americans and native alaskans, homeless populations, football teams, wrestlers, gymnats, fencing teams, MSM, HIV patients, Injectio ndrug users

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What syndromes are most CA-MRSA infections associated with?

Skin and soft tissue 77%
wound (traumatic) - 10%
urinary tract infection - 4%
sinusitis - 4%
bacteremia 3%
pneumonia 2%

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What is an unfortunate mistake in treatment that people used to treat pediatrics that had MRSA?

All treated with cephalosporin which the organism was resistant to. this delayed the use of the correct antibitoic and may have contributed to their deaths.

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What are some of the impacts that bacterial resistance is causing in society?

Lack of coverage–> increase in complicatoins and length of stay in hospitals
increased morbidity and mortality
requires more complicated treatment regimens
leads to earlier use of previously reserved agents (vancomycin) –> increase resistance VISA, VRSA. Rare but very difficult to treat
Contributes to treatment failure –> more medical visits, –> greater use of abx.

MRSA vs spider bite

Spider bites are more necrotic, can usually see a puncture bite
MRSA has a lot more erythema, involvement of a larger area of skin

Traditional treatment options for MRSA?

IV vancomycin (glycopeptide)
Trimethoprim-sulfamethoxazole (Sulfa, Bactrim)
Tetracycline - doxycycline covers MRSA
Clindamycin - not used as much anymore, things becoming clindamycin resistant, not as sensitive.

What test do you use to test clindamycin resistance?

Some strains are clindamycin resistant despite standard in-vitro testing showing susceptibility
Some strains are carrying the erm gene (erythromycin resistance), and can be induced to become clindamycine resistant when exposed to clindamycin
THE d test - checks for clindamycin -susceptible,
- Erythromycin-resistant organisms to determine inducible clindamycin resistance
- If D test is positive - means clindamycin won’t work
- Get a D-Shape around the antibiotic marker. Means its showing some resistance to erythromycin which means clindamycin would not work.

What are the newer treatment options for MRSA?

linezolid (Zyvox) IV OR PO an oxazolidinones. (Non Beta lactam)
Tedizolid (sivextro) IV OR PO an oxazolidinones. (Non beta lactam)
Daptomycin (cubicin) IV. A lipopeptide (Non beta lactam)
tygecycline (Tygacil) IV. A glycylcycline. (non beta lactam)
Ceftaroline (teflaro) IV. 5th gen cefalosporin (Beta lactam)
Oritavancin (Orbactiv) IV. Lipoglycopeptide (non beta lactam) 1 dose lasts 2 weeks.
Dalbavancin (Dalvance) IV. Lipoglycopeptide (NBL) (one dose lasts 2 weeks)

What is MRSA colonizatoin associated with? what are the guidelines for eradicating it?

Recent nasal aquisition of CA-MRSA associated with 10-fold increae in risk of devleoping skin and soft tissue infections
occasionally try to eradicate MRSA in nose b/c of this reason.

guidelines

do not routinely attempt to decolonize all pts with MRSA colonizatoin, just those likely to benefit clinically
topical intranasal mupirocin for 5 days (not more)
Daily bathing with antibacterial agent
Oral or IV antibiotics - not routine, but not more than 10 days in selected patients
Only HCW suspected to transmit MRSA should be screened and treated for carriage of MRSA
- usually in high risk areas .

What are diabetic foot wounds most likely caused by?

Most likely caused by a polymicrobial infection, anaerobes are highly likely. Can become necrotic and if it does they are likely to lose their lower leg.

What is hot tub folliculitis caused by? Treatment?

Caused by psuedomonas, get an itchy rash after hot tub use

Outpatient treatment usually consists of antipruretics (anti itch), and a steroid cream.

If it gets worse then you can use ciprofloxin, a fluroquinolone. But try to avoid.

Dog bite common pathogens and treament?

First have to think if the dog had a rabies vaccine, tetanus status and most common pathogen is pasturella.
- pasturella is carried by both dogs and cats
First want to irrigate, then most likely prescribe antibiotics
- Augmentin orally, IV equiv -ampicillin sulbactam (unasyn) Beta lactam inhibitors.
- Alternative: clindamycin & fluroquinolones

Dog and Cat bites, most common pathogen? What is cat scratch fever.

* Both dogs and cats carry pasturella multocida * Treat with augmentin, amoxicillin/clav Cat scratch fever. * Caused by bartonella * treatment is **doxycycline**

Mice and rat bites cause rat bite fever. What are common pathogens that cause this?

* Streptobacillus causes rat bite fever - * treat with augmentin * alt- doxy *

What most common pathogen are you worried about with human bites? tx?

* **Eikenella corrodens** is the most common pathogen * treat with **augmentin**

Yeast cellulitis treatment and management?

* can occur anywhere where skin touches skin * well defined border, sometimes itchy, and somewhat burn * tx * fluconazole - orally if more invovled. * **topically - nystatin - comes in a powder - 1st line** * can use ketoconazole but want to keep area dry.

What skin infection does measles cause? What are the three C's of measles.

* Measles is a paramyxoviridae family of viruses * Humans are the only natural hosts * Symptoms * **prodrome of fever, 3 C's cough, coryza (runny nose), conjunctivitis, malaise** * **Koplik spots - pathopneumonic - bluish spots in the mouth** * **maculopapular rash - body wide rash.**

What are some complications that go with measles? who is at high risk? contagious factor, and vaccines

* Common complications from measles include * otitis media * bronchopneumoniaa, * laryngothrachebronchitis, * diarrhea * Serious illness * One out of every 1000 measles cases will develop encephalitis which often results in permanent brain damage * one or two out of every 1000 children who become infected with measles will die frrom respiraotyr and neurologic complications * Subacute scleoriss parencephalaitis (SSPE) is rare but fatal degenerative disease of the CNS that is characterized by behavioral and intellectual deterioration and seizures that generally develop 7 to 10 years after measles infection. High risk * infants and children less than 5 * adults aged more than 20 * some not immunized, some only got 1 immunization. * pregnant women * can pass to fetus, cause death, hearign loss or other congenital defects * peole with compromised immune systems such as leukemia and HIV infection. spreadability * one of the most contagious of respiratory spead infections * 9 in 10 people who do not have immunity will become infected if exposed. Vaccine preventable * first dose at age 12-15 months * second dose at age 4-6 years or at least 28 days following first dose * adolescents 2 doses 28 days apart * adults born after 1857 2 doses 28 days apart or proof of immuinity * currently considered 3rd dose. * This is a live virus vaccine.

Herpes Zoster definition. Pattern? diagnosis? treatment?

* Latent varicella zoster virus * s/s * Get a prodrome - burning and tingling at site of eruption * Vesicular dermatomal lesions --\> follows the nerves * Does not cross midline unless it disseminates -- only if someone is immunosupressed. * Painful * can also get on the face called herpes zoster ophthalmacus. Can be associated with a stroke. * dx * No accurate lab test, only a clinical diagnosis * tx * Antivirals started within 1st 72 hours of onset of vesciles/prodrome * acyclovir, famcyclovir, valacyclovir are options * vaccine preventable * shringrex killed preparation 2 shot series starting at age 50 * zostavax- live virus - not used as much any more.