MRSA, Community Acquired

[Section Outline]

Description
Etiology

Author:

Benjamin S.Heavrin

Description

Methicillin-resistant Staphylococcus aureus (MRSA) has historically been a pathogen endemic within health care settings, usually affecting the elderly and chronically ill
- This strain of S. aureus has been termed “health care-associated MRSA” (HA-MRSA)
Throughout the past decade, MRSA has become an increasingly common pathogen among younger, healthier populations who do not have a health care-related exposure history
- This type of MRSA pathogen has been termed “community-acquired MRSA” (CA-MRSA)
CA-MRSA is the most common cause of skin and soft tissue infections seen in the ED
While CA-MRSA may cause skin and soft tissue infection, it may also lead to severe multisystem disease, including sepsis and necrotizing pneumonia

Geriatric Considerations
HA-MRSA (see below) is a different genotypic form of MRSA that frequently causes morbidity among the elderly, especially those living within extended-care facilities or those with health care-related exposures

Etiology

S. aureus is a gram-positive cocci frequently colonizing the skin
MRSA refers to a specific strain of S. aureus that has resistance against the antimicrobial properties of numerous antibiotics, including methicillin
Highest risk for colonization and subsequent infection:
- Prisoners
- Athletes (especially wrestlers, football, rugby)
- Soldiers
- Children in daycare
- IV drug users
- Those with prior treatment for MRSA or exposure to MRSA

Diagnosis ⬆ ⬇

[Section Outline]

Signs and Symptoms
Essential Workup
Diagnostic Tests & Interpretation
Differential Diagnosis

Signs and Symptoms

History

Skin and soft tissue infections:
- Increasing redness
- Pain
- Warmth
- Swelling
- Fever
- Chills
- Malaise
Sepsis/pneumonia:
- Weakness
- Dyspnea
- Fever
- Rigors
- Productive cough
- Chest pain
Inquire about prior diagnosis of MRSA infections, MRSA exposures, and family members or close contacts with a history of MRSA

Physical Exam

Skin and soft tissue infections:
- Abscess: Tender, raised boil with underlying induration and fluctuance
- Cellulitis: Warm erythema possibly with lymphangitic streaking
Sepsis:
- Vital sign abnormalities including tachycardia and hypotension, respiratory failure, mental status changes, petechiae, systemic signs of toxicity
Pneumonia:
- Tachypnea, crackles, retractions, hypoxia
- Alveolar opacities on chest radiographs

Pediatric Considerations
MRSA is the leading cause of skin and soft tissue infections among children presenting to the emergency department

Essential Workup

Abscess:
- I&D with packing and prompt follow-up is warranted for abscess
- Microbiology often performed for antibiotic sensitivity given the changing antimicrobial resistance patterns
Sepsis:
- Source identification, including blood culture/urine culture, CXR, is indicated as resuscitation begins
Pneumonia:
- Chest radiographs and continuous vital sign monitoring is indicated

Diagnostic Tests & Interpretation

Lab

Skin and soft tissue infections:
- Bacterial culture is often warranted to monitor for CA-MRSA resistance patterns
Sepsis and pneumonia:
- Blood, urine, and body fluid cultures. CBC, CMP to assess for organ dysfunction

Imaging

Bedside US:
- Abscess: Anechoic fluid collection
- Cellulitis: “Cobblestoning” within the soft tissue
CXR:
- Indicated for patients with presumed sepsis, systemic illness, or pneumonia

Diagnostic Procedures/Surgery

Cultures of skin and soft tissue infections are frequently obtained to monitor microbiology and antimicrobial resistance patterns should a patient fail a course of therapy

Differential Diagnosis

Other skin and soft tissue infections:
- Pathogens beyond MRSA which cause abscesses and cellulites should be considered (i.e., streptococcus)
Necrotizing fasciitis
Contact dermatitis
Deep vein thrombosis
Spider/insect bite
Drug reaction

ALERT
Empiric antimicrobial treatment of skin and soft tissue infections should cover for common skin pathogens beyond MRSA (i.e., streptococcus)

Treatment ⬆ ⬇

[Section Outline]

Prehospital
Initial Stabilization/Therapy
ED Treatment/Procedures
Medication

Prehospital

Contact precautions for all providers if MRSA is suspected
IV access and fluid resuscitation if sepsis is suspected

Initial Stabilization/Therapy

Begin resuscitation and administer early empiric antibiotics if pneumonia, fasciitis, or sepsis is suspected:

Include early coverage with antibiotics effective against MRSA

ED Treatment/Procedures

Skin and soft tissue infections:
- Abscess:
  - I&D with packing
  - Antibiotics may be considered as an adjunct to I&D
- Cellulitis:
  - Cellulitis caused by CA-MRSA in a healthy, well-appearing patient may be treated with oral antibiotics in the outpatient setting, but antibiotics should cover both strep and staph
  - Ill-appearing patients, patients with underlying medical conditions, and patients failing outpatient therapy require IV antibiotics with coverage that includes treatment for CA-MRSA
Sepsis and pneumonia:
- Early administration of broad-spectrum antibiotics that include coverage against MRSA should be given promptly if the patient is at risk for CA-MRSA

Medication

ALERT
Review antimicrobial resistance patterns of CA-MRSA within your community prior to choosing a specific antibiotic regimen, as many antibiotics listed below may not be 100% effective against CA-MRSA

First Line

Bactrim:
- Adults: Bactrim DS 800/160; 1-2 tabs PO b.i.d
- Children: 10 mg/kg PO b.i.d
Clindamycin:
- Adults: 150-450 mg PO q.i.d
- Children: 5 mg/kg PO/IV t.i.d-q.i.d
- Resistance rates to clindamycin are increasing
Doxycycline:
- Adults: 100 mg PO b.i.d
- Children: 2.2 mg/kg PO b.i.d
Vancomycin:
- Adults: 1 g IV q8-12h
- Children: 15 mg/kg IV q8-12h

Second Line

Rifampin:
- Should not be used as monotherapy due to inducible resistance
- Adults: 300 mg PO b.i.d
- Children: 10-20 mg/kg/d in 2 div. doses PO for 5 d; not to exceed 600 mg/d
Daptomycin 6 mg/kg IV per day
Linezolid:
- Adults: 600 mg PO/IV q12h
- Children: 10 mg/kg PO/IV q8h

Pregnancy Prophylaxis
Avoid the use of tetracyclines in pregnancy

Follow-Up ⬆ ⬇

[Section Outline]

Disposition
Follow-up Recommendations

Disposition

Admission Criteria

Patients with signs/symptoms of bacteremia, progressive infection, or systemic illness should be admitted:
- Fever, chills, lymphangitic streaking
Patients with underlying comorbid diseases such as diabetes or immunodeficiency should be admitted
Individuals who have failed a course of outpatient therapy should be admitted and given IV antibiotics effective against MRSA

Discharge Criteria

Healthy, well-appearing patients with simple skin and soft tissue infections may be followed in the outpatient setting

Issues for Referral

MRSA infection refractory to multiple medications may require infectious disease consultation

Follow-up Recommendations

All skin and soft tissue infections should be re-evaluated within 24-48 hr to monitor for clinical improvement
Individuals failing outpatient therapy require hospital admission and IV antibiotics

Pearls and Pitfalls ⬆ ⬇

CA-MRSA is the most common cause of skin and soft tissue infections seen in the ED
CA-MRSA is a rare but serious cause of rapidly progressive pneumonia and sepsis
Antibiotic resistance patterns are dynamic and vary widely across geographic boundaries
Be cautious with long-term use of tetracyclines in children

Additional Reading ⬆ ⬇

LiuC, BayerA, CosgroveSE, et al. Clinical practice guidelines by the infectious diseases society of America for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children: Executive summary . Clin Infect Dis. 2011;52(3):285-292.
OdellCA. Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) skin infections . Curr Opin Pediatr. 2010;22(3):273-277.
PallinDJ, CamargoCA, SchuurJD. Skin infections and antibiotic stewardship: Analysis of emergency department prescribing practices, 2007-2010 . West J Emerg Med. 2014;15(3):282-289.
PrusakiwskiMK, KuehlDR. Trends in emergency department management of skin abscesses . Am J Infect Control. 2015;43(4):336-340.
SingerAJ, TalanDA. Management of skin abscesses in the era of methicillin-resistant Staphylococcus aureus . N Engl J Med. 2014;370(11):1039-1047.
WallinTR, HernHG, FrazeeBW. Community-associated methicillin-resistant Staphylococcus aureus . Emerg Med Clin North Am. 2008;26(2):431-455.

See Also (Topic, Algorithm, Electronic Media Element)

Codes ⬆

ICD9

041.12 Methicillin resistant Staphylococcus aureus in conditions classified elsewhere and of unspecified site

ICD10

A41.02 Sepsis due to Methicillin resistant Staphylococcus aureus
A49.02 Methicillin resis staph infection, unsp site

SNOMED

423561003 community-acquired methicillin-resistant Staphylococcus aureus infection (disorder)
448812000 Sepsis due to methicillin resistant Staphylococcus aureus (disorder)
282028001 Multiple-resistant Staphylococcus aureus infection (disorder)

section name header

Basics ⬇

Geriatric Considerations

Diagnosis ⬆ ⬇

History

Physical Exam

Pediatric Considerations

Lab

Imaging

Diagnostic Procedures/Surgery

ALERT

Treatment ⬆ ⬇

ALERT

First Line

Second Line

Pregnancy Prophylaxis

Follow-Up ⬆ ⬇

Admission Criteria

Discharge Criteria

Issues for Referral

Pearls and Pitfalls ⬆ ⬇

Additional Reading ⬆ ⬇

Codes ⬆