PHAR 506 EXAM IV: Lecture Review

(4/11) Wenzler Lecture: Acute Bacterial Skin and Skin Structure Infections (ABSSSI)

Acute Bacterial Skin and Skin Structure Infections (ABSSSI) - Epidemiology: ABSSSI are the most commonly seen type of infection in clinical practice, leading to over 750,000

hospitalizations each year (10% of total). The prevalence and resistance has been increasing over recent years - Etiology: ABSSSIs arise from a large array of precipitous events and conditions. Immune status, geography, and

travel history may all contribute to infection development. A recent history of trauma/surgery, antibiotic therapy, alternative hobbies (IVDA), and exposures through occupation to animals may also predispose development.

o Typical pathogens include the gram positives: b-hemolytic streptococcus and staphylococcus aureus - Classification:

o Purulent: Consisting of pus. Likely pathogen: Staph aureus o Non-Purulent: Absence of pus, more superficial Likely pathogen: Streptococcus spp

Purulent ABSSSI - Infection: Collections of pus that may extend deep within the dermis, in some cases reaching the adipose layer. A

common location for infection is the butt. o Bug: Staphylococcus Aureus (May be MSSA or MRSA)

- Clinical manifestations: Cutaneous abscesses, furuncles, carbuncles o Furuncles: Also known as boils, furuncles are infections of the hair follicles. They are not

to be confused with folliculitis, a superficial inflammation of the epidermis often attributable to shaving.

o Carbuncle: Several adjacent furuncles that may intrude deeper than that of furuncles. These are common in obese patients, especially around the neck/hairline.

- Sx o Mild/Moderate: Painful, tender, and fluctuant red nodules localized to the infected

area that are often surmounted by a pustule, circumscribed by a rim of erythema and swelling o Severe: Systemic illness noticeable by patient vital signs (tachycardia, tachypnea, temperature)

- `Purulent ABSSSI` - Treatment Approach o Cultures: Traditionally No. A microbiological workup is not necessary as the causative agent may be

assumed to be Staph aureus o Incision and Drainage (I+D): I+D functions as source control and as 1st-line treatment.

§ Furuncles: Apply moist heat in the form of a warm washcloth. The boil should rupture or drain § Carbuncle: Will likely require I+D

2014 IDSA Guidelines Guidelines for the management of ABSSSIs are currently being updated Purulent (Expect Staphylococcus aureus) Mild: No cultures, No Abx, Just I+D Mod/Severe: Cultures + Empiric Abx Therapy Mod/Severe? Systemic Sx emerge or the patient is immunocompromised. In such cases, we will need to empirically cover MRSA and narrow our tx when cultures return Non-Purulent (Expect Streptococcus spp) Treating non-purulent infections requires getting a good patient history to identify risk factors for optimal empiric treatment. No cultures. Mild/Mod: Empiric Abx Therapy Severe: Broad-spectrum Empiric Abx Therapy

o Antibiotic Therapy: Traditionally No. In rare cases when tx is needed, Anti-MRSA agents are ascribed. Systemic signs and symptoms of infection is an appropriate validation of abx use. Evidence has shown that adding systemic abx to I+D does not improve cure rates, even in cases of MRSA

§ Exceptions: Patients who are immunocompromised, multiple abscesses, extremes of age, lack of response to I+D, and systemic illness

à IV: Vanco, Dapto, Telavancin, Oritavancin, Dalbavancin, Ceftaroline, Quinupristin/Dalfopristin à PO: Bactrim, Clinda, Linezolid, Tedizolid, Doxycycline, Minocycline, Rifampin

- `Recurrent Purulent ABSSSI` - Treatment Approach o Cultures: Still No. o Incision and Drainage: Yes, I+D will always be first-line for purulent ABSSSI o Abx Therapy: Still No. There is no clear benefit of abx therapy o *Decolonization Procedures: Patients experiencing recurrent purulent ABSSSI are recommended for

decolonization. Apart from the antiseptic procedures, daily washing of personal items is important § Chlorhexidine Bath + ¼ cup Bleach – Boom. § Intranasal Mupirocin or Povidone Iodine ointment

o If decolonization efforts are unsuccessful, patient should be evaluated with neutrophil disorders Non-Purulent ABSSSI

- Infection: A diffuse, often erythemic, superficial infection of the upper dermis that spreads o Bug: Streptococcus spp

- Clinical Manifestations o Erysipelas: Limited to the upper dermis, erythema with clearly delineated borders often involving the face o Cellulitis: Infection involves the deeper dermis and subcutaneous fat, presenting with erythema, swelling,

tenderness, and warmth. Rapidly spreads, with bursting vesicles, bullae (blister), and petechiae (red dot) § Pathology: Infection arises when microbes breach the skin surface, often affecting the lower legs § Risk Factors: Obesity, trauma/surgery, Hx, Venous Stasis/Lymphedema § Impaired blood flow or lymphatic return greatly promotes development of cellulitis

o Necrotizing fasciitis: A deep infection involving the fascia and/or muscle compartments, also known as ‘flesh-eating disease.’ It is an aggressive subcutaneous infection that rapidly spreads and induces great pain; has potential for mortality

§ Distinguishing features: (1) Degree/Severity of x – critically ill with ÝWBC, ÝT, PainÝÝÝ • Radiology: CT/MRI shows free air • Crepitus: CO2 released by rapid bacteria metabolism causes air to be stuck beneath the

skin, which when moved or irritated makes crackling sounds like rice crispies (yum yum) • Wood-hardness: The infected area will be very dense, full of pressure, cannot feel the

anatomy below • Gangrene: Well yea, it is necrotizing

- `Non-Purulent ABSSSI` - Treatment Approach o Cultures: Traditionally No. Blood cultures are rarely positive, and skin culture will be non-specific.

While we should get cultures for pt with systemic sx, the overwhelming majority of cases will be Streptococcus spp

o Incision and Drainage: There’s nothing to drain, we need to give abx o Abx Therapy: Yes. Cephalexin 500mg PO q6º -OR- Clindamycin 300mg PO q8º

- `Recurrent Non-Purulent ABSSSI` - Treatment Approach o Qualification: ³ 3-4 annual episodes of cellulitis each year, with attempts of treatment o Goal: Determine the precipitating cause – generally obesity, though often can be tinea pedis o Abx Therapy: Yes. Cephalexin 500mg PO q6º -OR- Clindamycin 300mg PO q8º

§ Prophylaxis? No. Flaws in external validity have produced limited data, mostly useless. - `Necrotizing fasciitis ABSSSI` - Treatment Approach

o à Surgery is required, extensive and repeated debridement. Keep cutting until you hit clean tissue § Abx therapy is required during and in-between debridement procedures § D/C Abx once clinically improved and afebrile for 48-72h

o Clinical Manifestations § Fournier’s gangrene: Necrotizing fasciitis of the genitals (has good bloodflow. Hmm.)

• Patho: Perianal or retroperitoneal infection spreads along fascial planes to genitalia • Risk Factors: Elderly (50+), Significant comorbidities (DM, Obesity)

o Potential Bugs: § Streptococcus pyrogenes - b-hemolytic = hemolyzes RBC § Aeromonas hydrophilia – Found in leaches of fresh/brackish water § Vibrio vulnificus – Found in coastal regions, may acquire if you eat 100lbs of shellfish

o Abx Therapy: Yes. Empiric therapy should cover: Streptococci, MRSA, Gram(-), Anaerobes • Gram(+) + MRSA Coverage à Vanco, Linezolid, Dapto • Gram(-) + Anaerobe Coverage à PipTazo, Carbapenem, Ceftriaxone + Metronidazole If suspect GAS, add protein synthesis inhibitor to decrease toxin production à Linezolid, Clindamycin

Infection ? Bug Cultures 1st Line Tx Abx therapy and beyond Purulent (Furuncles, Carbuncles)

Pus Staph aureus No* I+D No cultures, No antibiotics†. Just I+D Exception: Systemic Sx of Infection

- Outpatient: Bactrim, or alt - Inpatient: Vancomycin

If recurrent, will need to repeat I+D, decolonize with intranasal mupirocin, and consider chlorhexidine bathing

Non-Purulent (Erysipelas, Cellulitis)

No Pus Streptococcus (b-hemolytic group A)

No* Abx If recurrent, try to find an underlying cause. While it is usually obesity, it may also be tinea pedis.

Necrotizing fasciitis (special case of non-purulent)

OMG Strep pyrogenes

No I+D Broad Spectrum Gram(+) and Gram(-) therapy • Gram(+): Vanco or Linezolid or Dapto • Gram(-): PipTazo or Carbapenem

- May use Ceftriaxone, add Metronidazole (anaerobes) Abx therapy continues until: • No more debridement is needed • Clinically improved and • Afebrile for 48-72h

Bite Wound Ouch Oral Flora No Abx Human: Give Augmentin. PCN-ALL à FQ + Clinda for 7-14d Dog; Give Augmentin PCN-ALL à Clinda + 3rd gen cephalo

* = Exceptions: Clinical presentations involving systemic symptoms † = Exceptions: Patient shows systemic symptoms

Bite Wounds

- Infection rate after a dog or cat bite is 20% - Antibiotic therapies are given prophylactically based on risk

o Risk Factors: Puncture wounds, wounds to hand/face/foot, presenting > 12-24 hours after bite, or immunocompromised

o Choice of therapy is dependent on the oral flor of the biting species Antibiotic Therapy for Bite Wounds: 7-14 days, give Tdap if it has been > 10 years.

- Dogs and Cats (Pasteurella spp) à Augmentin –OR- Clinda + 3rd generation cephalosporin –OR- Doxycycline –OR- Bactrim

- Cats (Bartonella) à Azithromycin

- Humans (Eikenella corrodens) à Augmentin –OR- FQ + Clinda

May need to consider rabies Ig and Vaccine. (4/13) Schriever C Lecture: Emerging Infectious Diseases Emerging Infectious Diseases are defined to follow one or more of the following criteria:

- (1) Increasing prevalence within in the past 2 decades (HIV) o Slide says ‘Incidence’ but prevalence is likely correct. Dr. Max said HIV incidence is down this year

- (2) Infections resulting in changes of existing organisms (SARS) - (3) Infections spreading to new geographic regions (Zika) - (4) Re-emergence of older infections secondary to changes in resistance (Ebola, MDR)

Precipitating Factors of emerging infectious diseases - Most (60-80%) human infections originate in mammals, whereby the animal is the vector. Climate changes,

extreme weather changes, and sanitation issues may all impact rodent/bat/whatever populations. As an example, during periods of drought, mosquito populations flourish in the arid environment and the incidence of West Nile Virus may rise.

o Human Host Factors: Susceptibility (immunocompromised), demographics, trade, occupation, abx use o Human environment: Ecosystem, technology, war and famine, etc.

Example Regimen Vanco + Meropenem This isn’t an “Or”

è Both therapies should be started