Methicillin Resistant S. aureus (MRSA)

• Contact Infection Prevention and Control if MRSA positive, or if suppression while an inpatient is being considered.
• Consult Infectious Diseases/Clinical Microbiology if invasive MRSA infection.
• For all MRSA isolates including positive screening swabs (nose, perineum, groin) use topical antiseptics (see decolonisation guideline below). Add systemic antimicrobials where appropriate for surgical prophylaxis or treatment of infection.
• Co-infection with Group A streptococci can occur – see below.

Decolonisation protocol

Refer to MRSA decolonisation guideline in the Multidrug Resistant Organisms (MDRO): Guidelines for control, and in Hospital HealthPathways.

• Not to be used for more than 7 days – contact Infection Prevention and Control if longer course needed.

OR, if mupirocin resistance:

• Warn patient product may stain.
• Do not use with octenidine skin wash (potential for discolouration and altered antibacterial affects).

AND EITHER

OR, for patients intolerant of chlorhexidine and those with sensitive or fragile skin:

Surgical prophylaxis

Surgical prophylaxis if MRSA colonised, or previously MRSA colonised and current status unknown.

• Start decolonisation regimen (above) at least 24 h before surgery, and
• Add vancomycin to standard antimicrobial prophylaxis, as:

vancomycin HMLSchedNZFPMLnoids Vancomycin F: n/a Half life: 6 hours Elimination: renal fe: 0.9 Additional points: TDM

IV 1 g (< 70 kg), 1.5 g (70 – 100 kg) or 2 g (>100 kg). See surgical antimicrobial prophylaxis.

• Must be given diluted (1 g in at least 200 mL) and slowly (≤ 1000 mg/hour) to minimise infusion reactions.

MRSA soft tissue infection

• Usual treatment duration 5–10 days

trimethoprim+sulfamethoxazole HMLSchedNZFPMLnoids Trimethoprim+Sulfamethoxazole F: 0.8 Half life: 9 hours / 12 hours Elimination: CYP2C8/9 acetylated fe: 0.3 / 0.7

PO 160 mg/800 mg to 320 mg/1600 mg twice a day

• fe (trimethoprim) = 0.7, fe (sulfamethoxazole) = 0.3, consider adjusting dose if CrCl reduced.
• Sulfamethoxazole is metabolised by CYP2C8/9 and conjugation.

OR

clindamycin HMLSchedNZFPMLnoids Clindamycin F: 0.9 Half life: 3 hours Elimination: CYP3A fe: 0.1

PO 450 mg three times a day or IV 600 mg every eight hours

• Metabolised by CYP3A. (fe < 0.1).

Co-infection with group A streptococcus

Use clindamycin alone if susceptible, or add penicillin to above antimicrobials:

benzylpenicillin HMLSchedNZFPMLnoids Benzylpenicillin F: n/a Half life: 1 hour Elimination: hydrolysis fe: 0.9 (Penicillin G)

IV 1.8 g (3 megaunits) every six hours

• fe = 0.8, consider adjusting dose if CrCl is reduced.

followed by early switch to

phenoxymethylpenicillin HMLSchedNZFPML Phenoxymethylpenicillin F: 0.4 Half life: 0.5 hours Elimination: renal fe: 0.9 (Penicillin V)

PO 500 mg four times a day

• fe = 0.9, consider adjusting dose if CrCl is reduced.

Bacteraemia

• Usual treatment duration is at least two weeks IV.
• All MRSA bacteraemias should be discussed with Infectious Diseases.

Suspected S. aureus bacteraemia (MRSA status unknown)

flucloxacillin HMLSchedNZFPMLnoids Flucloxacillin F: 0.9 Half life: 1 hour Elimination: renal fe: 0.7

IV 2 g every six hours

• fe = 0.7, consider adjusting dose if CrCl reduced.
• Risk of hepatotoxicity is increased in females, patients > 55 years old, high doses, and courses longer than 14 days duration.

Mild penicillin allergy

cefazolin HMLSchedNZFPMLnoids Cefazolin F: n/a Half life: 2 hours Elimination: renal fe: 0.9

IV 2 g every eight hours

• fe = 0.9, consider adjusting dose if CrCl is reduced.

Severe penicillin allergy

• fe = 0.9, adjust dose if CrCl reduced.
• Must be given diluted (1 g in at least 200 mL) and slowly (≤ 1000 mg/hour) to minimise infusion reactions.

Suspected S. aureus bacteraemia with risk factors for MRSA colonisation

ADD vancomycin to the above regimens (flucloxacillin or cefazolin) until culture and susceptibility results are available:

• fe = 0.9, adjust dose if CrCl reduced.
• Must be given diluted (1 g in at least 200 mL) and slowly (≤ 1000 mg/hour) to minimise infusion reactions.

Confirmed MRSA bacteraemia

• fe = 0.9, adjust dose if CrCl reduced.
• Must be given diluted (1 g in at least 200 mL) and slowly (≤ 1000 mg/hour) to minimise infusion reactions.

Topic Code: 132653

must be prescribed or recommended by a consultant.