Methicillin-Resistant Staphylococcus Aureus (MRSA)

MRSA is a staph infection you cannot clear with the usual antibiotics, and you are the main thing standing between one colonized patient and the rest of the unit. Most of the work is unglamorous: contact precautions, hand hygiene, and clean equipment. Do it consistently and you stop transmission. Skip it and MRSA spreads through the hospital, other healthcare facilities, and the community where people live, work, and go to school.

What Is MRSA?

Methicillin-resistant Staphylococcus aureus is a staph infection that is hard to treat because it resists several antibiotics. In the community it most often causes skin infections, and in some cases pneumonia and other infections. Left untreated, MRSA can become severe and cause sepsis, the body's extreme response to infection.

Pathophysiology

Staphylococcus aureus is a gram-positive coccus that is both catalase- and coagulase-positive.

It has evolved numerous strategies to evade neutrophil-mediated killing across activation, migration, opsonization, and phagocytosis. As many as 40 immune-evasion molecules are known, with new functions still being identified. The organism produces a range of toxins: alpha-toxin, beta-toxin, gamma-toxin, delta-toxin, exfoliatin, enterotoxins, Panton-Valentine leukocidin (PVL), and toxic shock syndrome toxin-1 (TSST-1). Enterotoxins and TSST-1 drive toxic shock syndrome; PVL drives necrotic skin and lung infection and is a major virulence factor for pneumonia and osteomyelitis.

Statistics and Incidences

Up to 80% of people are eventually colonized with Staphylococcus aureus. Most are colonized only intermittently; 20-30% are persistent carriers.

Colonization rates run higher in healthcare workers, people with diabetes, and dialysis patients than in the general population. MRSA hand colonization among healthcare workers exceeds 4% (over 8% in North America). Infection occurs worldwide, with S aureus pyomyositis more common in the tropics. About one in three people (33%) carry S. aureus in the nose, usually without illness, and about two in every 100 carry MRSA, though most never develop serious infection. MRSA bloodstream infections in healthcare dropped 17.1% each year from 2005-2012, then leveled off from 2013-2016 with no significant change.

Causes

Predisposing factors include:

Neutropenia or neutrophil dysfunction, since S aureus evades neutrophil-mediated killing. Diabetes, where nonhealing wounds open the door. IV drug use; the opioid epidemic tracks with rising staph infections, and people who inject drugs are 16 times more likely to develop a serious staph infection. Foreign bodies, including intravascular catheters and prosthetic joints, heart valves, shunts, and grafts, with incidence rising alongside line-related bacteremias. Trauma, where open wounds become breeding sites.

Clinical Manifestations

Symptoms depend on the body part infected.

Skin infections bring swelling, warmth, redness, and pain. A serious MRSA infection in blood or deep tissue may show a fever of 100.4°F or higher, chills, malaise, dizziness, confusion, muscle pain, swelling and tenderness in the affected part, chest pain, cough, and wounds that will not heal.

Assessment and Diagnostic Findings

MRSA resists all β-lactams because of mecA, a gene that produces a penicillin-binding protein (PBP2a) with low affinity for β-lactam antibiotics.

Alongside broth microdilution, the Clinical and Laboratory Standards Institute (CLSI) recommends the cefoxitin disk diffusion test, or a plate with 6 μg/ml of oxacillin in Mueller-Hinton agar supplemented with 4% NaCl, as alternative testing methods. FDA-approved assays detect the mecA gene, and commercial chromogenic agars can be used for detection. Anti-PBP2a monoclonal antibodies, available as latex agglutination or immunochromatographic membrane assays, offer another detection route.

Medical Management

CDC urges clinicians to consider MRSA in the differential for skin and soft tissue infections (SSTIs) compatible with S. aureus, especially purulent ones: fluctuant or palpable fluid-filled cavity, yellow or white center, central head, draining pus, or pus aspirated with a needle.

Incision and drainage is primary therapy for furuncles, other abscesses, and septic joints and should be done routinely. If you are unsure whether pus is present, aspirate the lesion with an adequately sized needle and syringe.

Pharmacological Management

Several agents serve as alternatives to beta-lactams for outpatient SSTIs when oral MRSA activity is needed: clindamycin, tetracyclines (doxycycline and minocycline), trimethoprim-sulfamethoxazole (TMP-SMX), rifampin (only in combination), and linezolid.

Clindamycin is FDA-approved for serious S. aureus infections. It is not specifically approved for MRSA but has been used widely for SSTIs, with reports of success against CA-MRSA. Doxycycline is FDA-approved for S. aureus skin infections but not specifically MRSA; the long-acting tetracyclines doxycycline and minocycline appeared adequate for MRSA SSTIs caused by tetracycline-susceptible isolates in a small case series, though data did not support use in invasive infection. TMP-SMX is not FDA-approved for any staphylococcal infection, but case reports describe success against S. aureus including MRSA; in a CA-MRSA skin infection series in Los Angeles, California, prompt resolution occurred in six (50%) of twelve patients on double-strength TMP/SMX alone (plus incision and drainage) and in all six patients treated initially with TMP/SMX plus rifampin. Linezolid is FDA-approved for complicated skin infections and hospital-acquired MRSA pneumonia in adults.

Nursing Management

Nursing Assessment

Take a health history and document any allergies. Assess the patient's skin daily to confirm the treatment is not causing an adverse skin effect.

Nursing Diagnosis

Based on assessment, the major diagnoses are: Risk for infection related to inadequate primary defenses; Impaired skin integrity related to swelling and redness that may break the skin; Acute pain related to an infected open wound; and Impaired social interaction related to isolation.

Nursing Care Planning and Goals

Ensure isolation and contact precautions, enforce strict hand hygiene and PPE use, keep the environment clean, and prevent the spread of infection.

Nursing Interventions

Isolation and contact precautions. Isolate the patient in a side room, keep the door closed, and keep the contact precaution sign visible.

Hand hygiene. Follow the WHO 5 moments for hand hygiene using soap and water or alcohol gel as appropriate. Offer the patient hand hygiene opportunities, keep their fingernails short and clean, and have visitors decontaminate hands before and after visiting.

PPE. Wear a plastic apron and gloves before entering the patient's area. Wear PPE for contact with the patient, environment, and equipment, ask visitors to wear PPE if visiting another patient, keep PPE on while removing used equipment, and discard it in a clinical waste bin before leaving.

Environmental cleaning. Use disposable mops and cloths, keep lockers and tables clear to ease cleaning, change curtains if applicable, and have domestic staff use a Chlorine Based Product (CBP).

Equipment decontamination. Provide designated equipment for the patient's own use where possible, clean removed equipment with Tristel, keep items in the room to a minimum, discard all unused disposable items once the patient is discharged, and wash removed cutlery normally.

Monitor for infection. Check lab results and vital signs, especially temperature, every shift, document clearly in medical and nursing notes, and report significant results to the nurse in charge or medical team.

Evaluation

Goals are met when isolation and contact precautions are maintained, hand hygiene and PPE use are enforced, the environment stays clean, and the spread of infection is prevented.

Documentation Guidelines

Document individual findings and behaviors, cultural and religious beliefs and expectations, the plan of care, the teaching plan, responses to interventions and teaching, and progress toward outcomes.