MRSA Infections

Introduction

• The Centers for Disease Control and Prevention defines SSIs as infections related to an operative procedure that occur at or near the surgical incision within 30 days or within 90 days if the procedure involved implantation of prosthetic material.¹
• MRSA is defined as an S. aureus isolate with an oxacillin minimum inhibitory concentration of ≥ 4 mcg/mL.5
• Between 1986 and 2003, S. aureus was the most common pathogen associated with SSIs in the US, responsible for 22% of SSIs and increasing to 30% between 2006 and 2007; nearly half of which were due to MRSA.
• Though the proportion of SSI due to MRSA has since declined, it remains a significant source of concern given the higher mortality rates, prolonged hospital stays, and increased costs associated with MRSA infections.¹
• The decline in MRSA-related SSIs in recent years can be attributed to multi-faceted approach to infection control and prevention.⁶

Clinical Epidemiology

• HA-MRSA vs community-associated MRSA (CA-MRSA)
  • There are two overarching classifications of MRSA: HA-MRSA and CA-MRSA⁶
    • HA-MRSA is defined as an MRSA infection that occurs more than 48 hours following hospitalization or an infection that occurs outside of the hospital but within 12 months of exposure to healthcare
    • CA-MRSA is defined as MRSA that occurs in the absence of healthcare exposure.
  • Historically, these classifications differed by MRSA strains; however, those differences have blurred recently, given that patients can develop MRSA colonization in the community that later manifests in the hospital, and vice versa.⁶
  • Both types typically cause skin and soft-tissue infections, with the potential to become severe and invasive. These are particularly challenging to resolve given MRSA’s potential for multidrug resistance and ability to form biofilms on foreign devices such as endotracheal tubes.⁶

• Associated invasive syndromes include:⁶
  • Necrotizing pneumonia
  • Osteomyelitis
  • Infective endocarditis
  • Septic arthritis
  • Sepsis

Perioperative Infection Control Practices

Hand Hygiene³

• Preoperative cleansing of hands, under nails, and forearms with an antiseptic agent
  • May use either antimicrobial soap or alcohol-based handrub
  • Remove watches and finger rings before scrubbing
• Nails
  • No artificial nails
  • Must be clipped
• Must be practiced by all members of the surgical team, including all anesthesia providers. “Contaminated hands of anesthesiologists can serve as a significant source of patient environmental and stopcock set contamination in the operating room.”³

Surgical Attire/Barrier Devices³

• Surgical attire includes:
  • Scrubs
  • Gloves
  • Barrier devices (include masks, caps, gowns, drapes, and shoe covers)
• According to guidelines issued by the American College of Surgeons:^3,7
  • Scrubs should not be worn during patient encounters outside of the operating room or outside of the hospital perimeter
    • If worn outside, it should be covered by a lab coat or other appropriate cover-up
  • Scrubs/hats worn during contaminated cases should be changed before subsequent cases, even if not visibly soiled
  • Mouth, nose, and hair should be covered during all invasive procedures.
  • Jewelry should be removed or covered.
  • Double gloving is recommended to protect the surgeon from the risk of holes in inner gloves.

S. aureus Decolonization³

• There is limited evidence for routine S. aureus decolonization.
  • There is currently no consensus regarding the benefit of routine preoperative screening for S. aureus colonization.¹
• Decolonization may be considered in surgical patients who are nasal carriers of S. aureus and are at high risk of adverse outcomes if S. aureus infection develops at the surgical site.
• There are no current standardized decolonization regimens. Some studies have used the following:

Skin Antisepsis³

• Application of antiseptics to the skin prior to incision to reduce the burden of skin flora
  • Recommend using chlorhexidine/alcohol-based skin antiseptics for routine skin preparation of surgical patients
• Interventions that do not appear to reduce the likelihood of SSI include:
  • Applying skin prep agents in concentric circles as opposed to a horizontal pattern
  • Use of surgical site markers
  • Preoperative use of antimicrobial sealants for skin prep

Hair Removal³

• Preoperative removal of hair is associated with increased risk for SSI
  • Shaving hair with razors at the planned operative site should be avoided
• If hair removal is necessary, it should be performed with clippers or depilatory agents just prior to incision
• Other strategies with limited evidence include:³
  • Maintain normothermia
  • Limit traffic through OR
  • Use of laminar airflow systems
  • Use of high-inspired supplemental oxygen
  • Minimize red cell transfusion
  • Perioperative glucose control

Antimicrobial Prophylaxis

• The goal of antimicrobial prophylaxis is to reduce the burden of microorganisms at the surgical site during the operative procedure.¹
  • Patients who receive antimicrobial prophylaxis within 1-2 hours prior to initial incision have lower rates of SSIs than those who receive it outside of this window.
• Patients who meet the following criteria should receive MRSA prophylaxis:¹
  • Multiple SSIs due to MRSA or methicillin-resistant coagulase-negative staphylococcus were detected at the institution
  • Patient is known to be colonized with MRSA
    • Previously colonized patients should be considered at high risk of continued carriage for at least four years.^2,8
  • Patient is at high risk for MRSA colonization in the absence of surveillance data (e.g., recent hospitalization, nursing home residents, on hemodialysis or immunosuppressed)

Antimicrobial Selection¹

• MRSA prophylaxis includes a combination therapy of vancomycin + cefazolin
  • Vancomycin
    • Provides effective coverage for MRSA
  • Cefazolin
    • Added to prevent SSI due to coagulase-negative S. aureus
    • More effective coverage for methicillin-sensitive S. aureus than vancomycin

Antimicrobial Administration

• Dosing
  • Standardized dosing is typically acceptable.⁹
    • Vancomycin 15 mg/kg
      • Cefazolin 2 g
  • 3 g for patients weighing ≥ 120 kg
• Timing¹
  • Cefazolin should be initiated within 60 minutes prior to incision.
  • Vancomycin should be initiated 120 minutes prior to incision to ensure adequate tissue levels, given its prolonged infusion times
• Repeat dosing¹
  • Warranted for procedures that:
    • Exceed 2 half-lives of the drug
    • Have excessive blood loss (more than 1500 mL)
    • Have risk factors for shortened antimicrobial half-life (e.g., extensive burns)
• Duration¹
  • Repeat dosing is not necessary after wound closure
    • May cause increased risk of Clostridium difficile infection (CDI)
  • If the duration is continued beyond closure, it should not exceed 24 hours postoperatively
    • High risk for CDI and acute kidney injury
• Please see the OA summary on perioperative antibiotic prophylaxis for more details. Link

Considerations for Pediatric Populations

Epidemiology⁴

• Invasive HA-MRSA
  • More common in children younger than 1 year; relatively rare in children older than 1 year.
  • “In contrast to reports of declining invasive HA-MRSA in adults, the prevalence of HA-MRSA in children has remained relatively stable since 2005.”⁴

Preoperative Decolonization¹⁰

• It may be warranted in children who meet the following criteria:
  • Undergoing cardiac surgery
  • Scheduled to receive an implantable device (e.g., cerebrospinal fluid shunt, spinal instrumentation, baclofen pump)
• Should include both:
  • Mupirocin ointment to the anterior nares twice daily for the 5 days preceding surgery
  • Chlorhexidine bath or chlorhexidine antiseptic wipes for the 5 days preceding surgery

Antimicrobial Prophylaxis and Dosing⁹

• Same as adults, except for the dosage of cefazolin
  • Vancomycin 15 mg/kg (maximum dose of 2 g)
  • Cefazolin 30 mg/kg (maximum dose of 2 g)

Antimicrobial Administration⁹

• Timing, repeat dosing, and duration are the same as adults
  • Data in pediatric patients is limited; thus, recommendations have been extrapolated from adult data.