The incidence of Methicillin-Resistant Staphylococcal Aureus (MRSA) continues to be a major health care concern in hospitals and the community. This infection encompasses a wide spectrum of severity, ranging from mild cellulitis to serious life-threatening necrotizing infections and sepsis. National guidelines for its management in both hospitals and communities vary widely and may be confusing for both nurses and patients. Nurses need to understand these differences so they can prevent transmission and educate their patients.
Epidemiology
The first infection involving MRSA in the United States was diagnosed in 1968, and the organism has continued to evolve ever since. The proportion of hospital associated Staphylococcal infections that are due to MRSA (HA-MRSA) rapidly increased from 2% in intensive-care units in 1974 to 64% in 2004. Over 120,000 hospitalizations are due to MRSA annually. More deaths were caused by MRSA than HIV in 2016. Of MRSA infections that cause death, about 86% are HA-MRSA and 14% are Community-Acquired MRSA (CA-MRSA). Before 2000, MRSA was a rare pathogen in community-acquired infections and was more common in nosocomial infections; however, the prevalence of CA-MRSA has increased greatly in the past decade. In addition, beginning in 2002 there have been a handful of cases documented in which the bacterium was also found to be resistant to one of the last available drugs being used to treat it.
MRSA is the result of decades of often unnecessary antibiotic use. Inappropriate antibiotics have been prescribed for colds, flu and other viral infections that don’t respond to those drugs. Even when appropriate, antibiotics usage has contributed to the rise of drug-resistant bacteria because they don’t destroy all the bacteria they target. The mechanism of methicillin resistance involves a mutation in one of the bacterial cell-wall proteins to which penicillin must bind to kill the bacterium. This mutation renders the organism resistant to all penicillin and almost all cephalosporins. Microorganisms live on an evolutionary fast track, so bacteria that survive treatment with one antibiotic soon learn to resist it.
Because MRSA is so antibiotic resistant, it is termed a “superbug” by some investigators. This superbug is a variation of an already recognized human pathogen, S. aureus, a gram-positive bacteria that occur in grape-like clusters termed cocci. This variation is usually found in the nose, armpit, groin, throat, and perianal areas. Damage to the skin or other injury may allow the bacteria to overcome the body’s natural protective mechanisms leading to infection and dermal destruction. MRSA is also one of the types of bacteria that have been termed a “flesh-eating bacterium” because of the widespread necrotizing complications. MRSA differs from the VRE organisms (vancomycin-resistant enterococcus) in that enterococci are bacteria that occur in the intestine. However, a strain of MRSA can also be resistant to vancomycin.
Transmission
Both CA-MRSA and HA-MRSA are spread both directly through person-to-person contact and indirectly by a person touching objects such as towels, toys, doorknob or other surfaces and leaving behind MRSA bacteria. Some MRSA bacteria may survive for weeks on surfaces like towels, furniture, and many other items. Although MRSA can be found in secretion droplets by infected individuals, direct contact is the usual way MRSA is transmitted to others. Wounds or injuries from gunshot wounds to minor lacerations may introduce MRSA as well. The incubation period for MRSA varies from 1 to 10 days, with the contagious period including the incubation period. The contagious period can continue through the time it takes to eliminate an individual’s MRSA infection and test negative.
Pathology
Staph aureus infections breakdown the body’s defenses by producing a variety of toxins and enzymes. Adding antibiotic resistance to this list of pathogenic mechanisms makes MRSA more dangerous.
proteolytic enzymes – break down proteins resulting in pus production
enterotoxins – proteins that cause vomiting, diarrhea and in some cases, shock
exfoliative toxin – a protein causing skin disruption, blisters
exotoxin TSST-1 – a protein that can cause toxic shock syndrome
coagulase – an enzyme produced that can aid in diagnosis
CA-MRSA Infection Risk Factors
Athletic sports, sharing towels, mats or other personal items
Conditions that suppress the immune system function such as HIV, cancer, autoimmune disorder or chemotherapy
Unsanitary or crowded living conditions such as prisons, dormitories or military barracks
Residential or assisted living facilities
Poor hand washing
Eczema or psoriasis
IV drug use
Farm work – pigs, cattle and poultry carry a clone-like version
HA-MRSA infection Risk Factors
Infected hospital personnel
Accidental transfer by hospital personnel
Peripheral or central catheter
Hemodialysis – the largest risk group
Surgery
Burns
Urinary catheter
Mechanical ventilation
Symptoms of MRSA
Skin and dermal complaints are the most common in CA-MRSA infections. They can be easily dismissed by a healthcare provider as being unrelated to a larger disease, and require a good history and evaluation to properly diagnose. Other symptoms include:
Recent history of dermal, nasal or perianal injury
Swelling
Pain at the site
Fever or warmth at the site
Pus or drainage
Itching
The site may present as a sore, boil, abscess, carbuncle, cellulitis, sty or impetigo-like lesions on the face or other areas
Antibiotic treatment not reducing symptoms
More serious infections may have red streaks that progress from the site
Ulceration with draining pus
HA-MRSA infections are usually suspected when the hospitalized patient develops signs of sepsis, fever, chills, low blood pressure, weakness, and mental deterioration, even if the patient is being treated with an antibiotic. Hospitalized patients do not need to have a primary site of MRSA infection, only a site where MRSA can invade and proliferate.
Signs and symptoms of HA-MRSA infections are:
Any of the above skin infections (early signs and symptoms)
IV site infection
Surgical wound infection
Pneumonia
Infection not responding with antibiotic therapy
Sepsis
Osteomyelitis
Organ failure
Tachycardia
Death
Diagnosis
The diagnosis of MRSA is done by culturing the infected site. A high index of suspicion should be held if the patient has any risk factors. Areas of the skin with pus, abscesses, or blisters should be cultured for MRSA. Patients with sepsis or pneumonia should also have blood cultures drawn. Any surgical site, bone marrow, joint fluid, catheter site or other potential source needs to be cultured specifically for MRSA. Unfortunately, MRSA infections look like almost any other staph infection initially, so identification of MRSA strains is important.
The definitive laboratory studies to diagnose MRSA are straightforward. S. aureus is isolated and identified by standard microbiological techniques (growth on agar plates and a positive coagulase test). The coagulase test is a laboratory test based upon the ability of S. aureus to produce the enzyme coagulase that ultimately leads to the formation of a blood clot. After S. aureus bacteria are isolated, the bacteria are then cultured in the presence of methicillin (and usually other antibiotics). If S. aureus grows in the presence of methicillin, the bacteria are termed MRSA. Because of this process, the definitive diagnosis may take several days to complete before proper treatment can begin.
Treatments
Standard contact precautions in HA-MRSA:
The most important nursing concern in HA-MRSA is to prevent the spread of the infection to other patients. Patients should be placed in a single isolation room with its own bathroom. Risk assessment will be important in this situation. Patients considered to be most vulnerable to cross-infection are those with large open wounds or invasive devices such as intravenous cannula and those who are immunosuppressed. Where there are insufficient single rooms or definitive diagnosis is not available, patients may be nursed in double room with separate handwashing and bathroom facilities. The door to all rooms should be kept shut to minimize the spread of infection to adjacent areas. Hand hygiene should be undertaken before and after all patient contact and upon leaving the isolation facility. Protective clothing, such as disposable outerwear and gloves, should be worn when direct patient contact is performed. Infected wounds must be kept covered with an impermeable dressing regardless of the patient’s location.
A placard should be placed on the door of the patient room to inform new visitors to contact the nursing personnel for education on the proper precautions. Visitors should be told to refrain from eating and drinking in the room. Brief noncontact interactions do not require garbing. Used gloves and barriers should be removed and disposed of inside the isolation room. All waste generated within the isolation room should be labeled as clinical waste and all linen should be marked as contaminated/infected and managed according to institutional policy. Wherever possible, equipment should be for single-patient use; if multipatient-use equipment is required it should be decontaminated according to manufacturer’s instructions. All equipment should be clean and dust free since dust can play a minor role in MRSA transmission.
Patient isolation in CA-MRSA:
Isolation is generally not needed in the community as Staphylococcus aureus does not pose a serious infection risk to people in their own homes or residents in nursing/residential facilities. The major principles of good hand washing technique and the need to keep the area covered apply. If there are vulnerable residents in a home, such as those with open postoperative wounds or those who are immunocompromised, isolation of the patient with MRSA will be required following the principles used in the hospital. Nurses should obtain a health history of household members so appropriate information can be given.
Decolonization:
An additional element of many infection control strategies involves MRSA decolonization, but there is uncertainty about which patients benefit. Skin decolonization treatment will reduce the number of bacteria on the skin, nares and head of patients with MRSA, which will reduce the risk of cross-infection. Several studies have indicated that MRSA decolonization is only temporary and that patients become recolonized over time. Many patients who are scheduled for cardiothoracic, orthopedic and abdominal surgery are frequently cultured and instructed on decolonization prior to admission in hope of decreasing post-operative MRSA.
There are multiple decolonization strategies though they are lacking in large evidence-based research. In vitro data suggest that zinc may interfere with bacterial adherence. A product such as the ZNP bar, soap containing 2% pyrithione zinc, may be helpful. Products containing 10% benzoyl peroxide are another alternative in body washes. Household bleach bath are another approach for outpatients with colonized MRSA. Two tablespoons (about 2 capfuls) in a bathtub filled with water is sufficient. Up to 1/4 cup can be used, but skin peeling or irritation may occur at this dose. The optimal frequency for bleach bathing has not been established. Recommendations range from weekly to daily. Patients should be warned that repeated bleach baths may remove the finish from nonporcelain bathtubs. Other products include chlorhexidine topical antiseptic wash for 5 days.
As for nares decolonization, mupirocin is losing efficacy because of increasing resistance. Clearance rates may be as low as 30% and may be replaced by another topical ointment such as Neosporin or used in conjunction with it. Tea tree oil also appears to be effective. Soaps and creams containing tea tree oil were shown in at least one study to be as effective as a number of antibiotic drugs for decolonization when used in the nares with less expense.
MRSA in the Health Care Worker (HCW):
One in every 20 healthcare workers carries MRSA, but the vast majority of these carriers are without symptoms. Healthcare workers are usually vectors, rather than the main sources of MRSA transmission. Some institutions suggest that screening workers be part of pre-employment exams. Regardless, screening should only be part of a comprehensive infection control policy including staff education and emphasizing high compliance with hand hygiene and contact precautions. Routine decolonization of HCWs who are asymptomatic MRSA carriers is not recommended. If staff is identified as the source of a MRSA outbreak they should be fully treated and refrain from patient care until cultures are negative. Similarly, guidelines do not recommend restricting work activities unless colonized HCWs are found to be the source of MRSA transmission.
Microbial Therapy:
Antibiotic therapy is still the mainstay of medical care for MRSA, but antibiotic therapy is complicated by MRSA’s antibiotic resistance. Once the antibiotic sensitivities of the patient’s cultures are determined, the patient can be treated appropriately. Unfortunately, sensitivity testing takes several days for results which may delay appropriate treatment.
Patients presenting with superficial skin lesions are frequently given penicillinase-resistant penicillin, or first-generation cephalosporin’s antibiotics. These are not effective against MRSA. An evaluation of risk factors and culturing of the wound should be done in patients suspected of MRSA infections. For patients with CA-MRSA who are being sent home, it is important for them to be instructed to take all antibiotics as directed and not to stop the antibiotic even if the symptoms seem to resolve before the prescription is finished. Early stoppage of antibiotics can allow MRSA to survive and develop further antibiotic resistance. All wounds should have a follow up appointment within 48 hours to ensure that there is improvement. The earlier the appropriate diagnosis and therapy is instituted for MRSA, the better the prognosis.
The majority of serious HA-MRSA infections are treated with two or more antibiotics. A number of IV antibiotics can effectively treat MRSA infections, including the following:
Vancomycin 30 mg/kg, the dose should not exceed 2 g in any 24-hour period. It is important to administer vancomycin slowly over 90 minutes to prevent “red man syndrome,” a hypersensitivity reaction linked to rapid administration of the antibiotic.
Daptomycin (Cubicin) 4 to 6 mg/kg administered via IV piggyback every 24 hours. This drug has been shown to be safe, although it can occasionally cause elevations in creatine kinase levels.
Linezolid (Zyvox) 600 mg every 12 hours. Linezolid is a monoamine oxidase (MAO) inhibitor. The usefulness of linezolid is limited by its cost and toxicity as well as the potential for the organism to develop resistance to the drug. Side effects related to treatment include thrombocytopenia, peripheral and optic neuropathy, and lactic acidosis in patients with prolonged therapy.
Tigecycline (Tygacil) 100 mg IV once, then 50 mg IV every 12 hours. This drug has a broader spectrum of antimicrobial activity.
When MRSA is confirmed or suspicion is high the following oral antibiotics should be used.
Trimethoprim-sulfamethoxazole. This agent has been shown to be 95% effective.
Clindamycin. Drug resistance has been found, particularly if it is resistant to erythromycin.
Tetracycline or doxycycline/minocycline. A 21-day course is given.
Linezolid.
Rifampin. It is typically effective in combination with other drugs. Patients should be told about changes in urine color
The CDC suggests that a number of different antibiotic regimens may work to help patients based on the type of infection, its severity, and the patient age, pregnancy or health status. The CDC recommends following the guidelines published by the Infectious Diseases Society of America in 2011, which are still recommended to date.
Debridement:
Drainage of exudate or abscess is the main surgical treatment of MRSA infections. Items that can serve as sources of infection (tampons, intravenous lines) should be removed. Drainage of pus needs to be followed by appropriate antibiotic therapy as discussed above. Debridement may be extensive in the cases of necrotizing fasciitis, with the removal of muscle mass and long term disfigurement. Foreign bodies present that are likely sources of infection such as, artificial grafts, artificial heart valves, pacemakers, or joint prosthetic may need to be removed if appropriate antibiotic therapy is unsuccessful.
Discharge
When patients with MRSA are discharged from the hospital to their own home they do not need routine MRSA screening, and it should only be carried out if there are clinical indications; for instance, where a wound appears infected. In some situations screening may be required if the patient needs to be readmitted into hospital in the near future.
If a patient with MRSA is discharged to a nursing/residential home, screening should be undertaken according to local guidelines and the potential risk to others in the care facility needs to be considered. Following skin decolonization treatment, the need for screening will vary and depends on the level of cross-infection risk. Again, local infection control policies should be followed. All health workers should understand the different MRSA-management protocols so that effective communication may be achieved. This will help to minimize anxiety and enable patients to make a seamless transition from hospital to community care or home.
According to the U.S. National Institutes of Health, the prognosis of MRSA infection varies according to the severity of the infection and the general condition of the person who has the infection. People in good health who have mild CA-MRSA, which is appropriately treated, recover in almost every case. The recurrence rate of MRSA infection in mild cases is thought to be very low, but some investigators report that patients may be carriers for up to 30 months, so it is possible for a carrier to have a contagious period for this length of time.
Although MRSA is still a major patient threat, a CDC study showed that invasive MRSA infections in healthcare settings are declining. Invasive HA-MRSA infections declined 54% between 2005 and 2011, with 30,800 fewer severe MRSA infections. In addition, the study showed 9,000 fewer deaths in hospital patients in 2011 versus 2005. Little is known about the population at large that may be MRSA carriers, but a new more virulent strain of CA-MRSA has been identified, so a high index of suspicion in patients presenting with skin lesions, good hand washing, and contact precautions should be the nurse’s priority.
References:
Making Health Care Safer. (2011). CDC: Vital Signs. Retrieved from https://www.cdc.gov/vitalsigns/pdf/2011-03-vitalsigns.pdf
Moran, Gregory J. et. al. (2013). Acute Bacterial Skin Infections: Developments Since the 2005 Infectious Diseases Society of America (IDSA) Guidelines. Journal of Emergency Medicine, 44 (6), 397-412. Retrieved from https://www.clinicalkey.com/#!/content/journal/1-s2.0-S0736467912015740.
MRSA Tracking. Retrieved from https://www.cdc.gov/mrsa/tracking/index.html.
Overview, Methicillin-Resistant Staphylococcus aureus. Retrieved from https://www.niaid.nih.gov/research/mrsa-overview.
The Impact of Treating Staphylococcus Aureus Infection and Colonization on the Clinical Severity of Atopic Dermatitis. (2012). Retrieved from https://www.clinicalkey.com/#!/content/clinical_trial/24-s2.0-NCT0017995…
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