Management of CA-MRSA

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) are strains of MRSA that are known to cause infections in people living in the community.

Those infected are often otherwise healthy, with no traditional risk factors for MRSA acquisition, such as chronic disease or prior medical interventions.

CA-MRSA primarily cause community-onset skin and soft-tissue infections (SSTIs), which are often recurrent and can spread easily to others who are in close contact with a person who has CA-MRSA, especially those who share the same household.

Less commonly, CA-MRSA can lead to more severe disease, such as bacteraemia, musculoskeletal infections and pneumonia. CA-MRSA strains are also the cause of the majority of healthcare associated MRSA infections acquired in Western Australian hospitals.

Key points

Antibiotic therapy

  • CA-MRSA strains, like all MRSA, are resistant to all beta-lactam antibiotics, including flucloxacillin, amoxycillin / clavulanate and all cephalosporins, for example cephalexin.
  • Refer to the antibiotic therapy recommendations below.

Management of skin and soft tissue infections (SSTIs)

  • Incision and drainage (I&D) is recommended, whenever possible, as a priority.
  • I&D may be sufficient for small abscesses and boils and when the patient is well and has no systemic symptoms and/or no co-morbidities.
  • Prescribe antibiotics if I&D is not possible, and/or the patient has significant co-morbidities.
  • Management in a hospital is likely to be required for patients with large or deep abscesses, extensive cellulitis and/or are unwell with systemic symptoms.

Decolonisation treatment

Decolonisation is recommended when individuals or their household contacts:

  • have recurrent CA-MRSA or staphylococcal-like infections
  • are at increased risk of infection due to other existing medical conditions
  • are healthcare workers or carers

or

  • when there are ongoing MRSA infections occurring in a well-defined, closely-associated cohort, such as a household or close group, for example a dormitory or sports club.

Decolonisation is required for all people with colonisation or infection caused by specific rare strains of CA-MRSA that are of concern to the Department of Health due to increased antibiotic resistance.

These people, and their GP or other healthcare provider, will be sent a letter requesting that they have decolonisation and screening swabs (nose, throat and wounds) taken at week 1 and 12 post-decolonisation to ensure clearance of the organism.

If there are ongoing infections in a household despite treatment, decolonisation of all household members should be undertaken, even if some members do not have an active infection. All household members should commence decolonisation on the same day.

Antibiotic therapy

All MRSA are resistant to all the beta-lactam antibiotics including flucloxacillin, amoxycillin/clavulanate and all cephalosporins e.g. cephalexin.

The decision to prescribe antibiotics requires clinical judgment and an assessment of the severity of the infection. The choice of antibiotics is dependent on the age, allergy history and co-morbidities of the patient.

It is advised that you discuss with an infectious diseases physician/clinical microbiologist if:

  • the patient’s symptoms are worsening despite therapy
  • the patient has multiple drug allergies
  • the isolate is resistant to suggested antibiotic agents
  • the patient is a neonate (< 2 months).

Adults

Table: Antibiotic therapy recommendations for adults
In order of preference  Antiobiotic  Dose  Pregnancy category # 
First line Clindamycin Δ 450mg TDS, orally for 5 days (see Note 1) A
Second line Trimethoprim with sulphamethoxazole 160+800mg BD, orally for 5 days (see Note 1) C
Third line  Doxycycline 100mg BD, orally for 5 days (see Note 1) D

Children

Table: Antibiotic therapy recommendations for children
In order of preference Antiobiotic  Dose 
First line  Trimethoprim with sulphamethoxazole 

4+20mg/kg (up to max 160+800mg) per dose orally, 12 hourly for 5* days

Tablets / oral suspension available on PBS (See Note 2 below)

Second line  Clindamycin Δ

10mg/kg (up to max 450mg) per dose orally, 8 hourly for 5*days (suitable for older children if able to swallow 150mg capsule)

Oral suspension not on PBS list nor readily available off PBS

Third line  Doxycycline

ONLY Suitable for Children >8 years:
2.5mg/kg (up to max 100mg) orally, 12 hourly for 5* days

Tablets and capsules available on PBS

# Therapeutic Guidelines Antibiotic 

Δ Clindamycin should NOT be used for MRSA isolates RESISTANT to erythromycin and related macrolide class antibiotics (azithromycin, clarithromycin, roxithromycin). PBS restricted benefit listing for clindamycin courses of <=24 150mg capsules. PBS authority prescription required for courses >25 150mg capsules (Indication: gram-positive coccal infections where these cannot be safely and effectively treated with penicillin).

* See Note 1

Note 1

Longer therapy may be required for carbuncles, cellulitis, widespread or recurrent impetigo. 

Note 2

Where trimethoprim with sulphamethoxazole is not appropriate (MRSA is resistant or patient allergy) and second line agent clindamycin capsules cannot be swallowed or taken, consider use of PBS listed erythromycin ethyl succinate oral suspensions, provided MRSA sensitivity to erythromycin has been demonstrated.

Note 3

Neonates (<2 months) requiring antibiotic therapy should be discussed with relevant specialist colleagues with paediatric expertise.

Erythromycin is specifically contraindicated in this age group because of an increased risk of pyloric stenosis.

Note 4

Group A streptococci (GAS) are another common cause of skin and soft tissue infection, particularly cellulitis and impetigo.

If GAS infection is suspected, therapy should include an agent active against this organism (beta-lactam or clindamycin).

Tetracyclines and Trimethoprim-sulphamethoxazole, although active against MRSA, are not recommended treatments for suspected GAS.

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