Ear Center: MRSA Infection (Methicillin Resistant Staphylococcal Aureus)

ca-MRSA  |  Signs & Symptoms  |  Treatment  |  Prevention  |  Suspect Infection?  |   New MRSA Strain | References

About MRSA (Methicillin Resistant Staphylococcal Aureus, a bacteria)

What is MRSA?
What is "Community Acquired" MRSA (ca-MRSA)
How is ca-MRSA treated?
How can ca-MRSA be prevented?
What should I do if I think that I or my child might have a ca-MRSA infection?

MRSA

MRSA stands for methicillin resistant staphylococcus aureus. MRSA is a type of gram positive bacteria that causes serious infections of various types such as skin, incision, and wound infections as well as blood infections (septicemia).
For many years, MRSA has been the number one bacteria causing in-hospital infections. Over the years, MRSA has become resistant to many antibiotics. MRSA is usually seen in hospitalized patients who have undergone an operation or have had their "barrier defenses" violated by indwelling catheters (central venous lines, foley catheters, endotracheal tubes, kidney dialysis catheters, etc.). Health care acquired MRSA is usually treated with intravenous vancomycin in addition to several other IV antibiotics. Rare cases of vancomycin resistant MRSA infections have been reported.

Community Acquired MRSA (ca-MRSA)

Recently, a new strain of MRSA has been identified in the community setting. It is referred to as "community acquired MRSA or ca-MRSA" in contrast to health care acquired MRSA (hc-MRSA). ca-MRSA is causing an epidemic and is more virulent than hc-MRSA.

How did ca-MRSA develop?

Genetic analysis of ca-MRSA points to methicillin sensitive staphylococcal aureus (MSSA) strains acquiring a "staphylococcal cassette chromosome (SCC) mec type IV element in the community. SCCmec is a mobile genetic element that is conjectured to have entered MSSA and codes for genes that changed the MSSA's penicillin-binding proteins. In turn, the change in penicillin-binding proteins leads to methicillin resistance.

Symptoms & Signs

The symptoms and signs of ca-MRSA include the acute onset of painful skin boil(s) or abscess(es) anywhere on the body. There may be one lesion or many. The abscesses may be clustered together or in several locations at once such as on the face and legs. ca-MRSA infection may involve the ears and may cause painful ear drainage and multiple abscesses in and around the external ear. Facial and scalp ca-MRSA infections are painful and tend to become deep abscesses before they spread out into the surrounding tissue. It is common for patients to think that they have been bitten by an insect such as a spider, etc.

ca-MRSA is thought to reside in the perineum or colon rather than in the nose like hc-MRSA. Abscesses often begin in the buttocks, thighs, or lower legs. Some patients have developed colitis due to ca-MRSA.

A group of researchers at the Wake Forest University School of Medicine recently studied children 18 or younger who presented to their Emergency Department with skin abscesses requiring incision and drainage. Although only a small number of children were reported (N=68), 88% (60/68) were found to have culture proven staphylococcal aureus as the causative organism. Of those 88%, 85% (51/60) were caused by ca-MRSA. All (100%) of their cases of ca-MRSA were sensitive to trimethoprim/sulfamethoxazole; 90% were sensitive to clindamycin.

Duggal et.al. reported in January 2011on a series of 136 children presenting to the Emergency Department with deep neck abscesses. The median age was 16 months (range 1 month to 13 years). Patients aged < 16 months were 10 times more likely to have a staph infection and 12 times more likely to have a MRSA infection (p < 0.0001). Of 118 isolates, 42% were MRSA, 30% were methicillin-sensitive S aureus, and 28% were non-S aureus species. MRSA accounted for 58% of the isolates. In their series, 8% of the MRSA isolates were resistant to clindamycin. All isolates were sensitive to Bactrim and vancomycin.

Treatment

ca-MRSA is treated by:

  1. Debridement or drainage of infected sites. Large abscesses may require gauze packing. Active draining lesions are the most contagious to others. Infected ears may require tympanomastoidectomy.
  2. Covering draining lesions with sterile bandages.
  3. Outpatient treatment: oral antibiotics such as double doses of doxycycline, trimethoprim-sulfamethoxazole, clindamycin (10-15% resistance reported), linezolid (limited to 4 weeks in adults or 2 weeks in children) for 10 days or longer. Adding rifampin may be useful in some situations.
  4. Inpatient treatment: IV vancomycin or other appropriate medications known to treat ca-MRSA.
  5. Otic drops that may be useful include: tobramycin, gentamicin, vancomycin, TMP/SMX, polymyxin B/hydrocortisone, ofoxacin, sulfacetamide, dilute acetic acid, fusidic acid (available in Europe but not in the US), Caution must be exercised when using potentially ototoxic topical medications with existing perforations or tubes.

For vancomycin resistant strains, the following medications may be usefu (some of these medications are still in trials):

  • linezoid
  • teicoplanin or tigecycline
  • ceftobiprole or ceftaroline
  • dalbavancin
  • iclaprim
  • oritavancin or telavancin

Prevention

There is no sure way to prevent becoming infected with ca-MRSA. However, common sense precautions can be taken to help prevent infection and the spread of infection:

  1. The use antibacterial soap is recommended (check the soap's label for the words "Antibacterial").
  2. Bathe with a washcloth that is routinely washed in hot water. Avoid using sponges.
  3. Use Hibiclens® for cleansing active lesion areas. Hibiclens® is available as an over-the-counter solution.
  4. Wash clothes in a washing machine set on the hot cycle.
  5. Avoid sharing cups, towels, sports equipment, etc.
  6. Disinfect sports equipment regularly.

What should I do if I think that I or my child might have a ca-MRSA infection?

If you think that you, your child, or anyone else in your family might have a ca-MRSA infection, you should contact your family doctor or pediatrician immediately. The longer that ca-MRSA infections remain untreated, the more chance there is for significant complications and for spreading the infection to others. Currently, approximately 70% of ca-MRSA infections remain confined to the skin or soft tissues. However, ca-MRSA has the pathologic potential to cause very serious complications such as sepsis (blood infection), bone and joint infections, epidemic furunculosis (multiple abscesses), necrotizing pneumonia, and death.

Emerging New Resistant MRSA Strain

A new highly drug resistant, "flesh eating" strain, of MRSA has been recognized in gay men, particularly in San Francisco and Boston. The new strain is called "MRSA USA300" and contains a plasmid call pUSA03. The new strain is similar to the ca-MRSA described above. However, it has become resistant to clindamycin, tetracycline (Vibramycin™, doxycycline, etc.), and mupirocin (Bactroban™). The new resistance to these antibiotics will make it more difficult to treat. The bacteria spreads through anal intercourse and skin-to-skin contact. It can cause necrotizing fasciitis, pneumonia, and single or multiple skin abscesses.

If you think that you or a member of your family might have ca-MRSA infection, you should notify your family doctor immediately and/or seek immediate emergency medical treatment.

References

  1. Robinson, W. MRSA: It's Not Just a Hospital Problem Now. Moses Cone Health System, MD Journal, Winter, 2007, 3.
  2. Altman LK. New Bacteria Strain is Striking Gay Men. The New York Times, 1-15-08.
  3. Magilner D, Byerly MM, Cline DM.The Prevalence of Community-Acquired Methicillin-Resistant Staphylococcal Aureus (CA-MRSA) in Skin Abscesses Presenting to the Pediatric Emergency Department. NC Med J. September/October 2008;69(5):351-354.
  4. Baugher KM, Hemme TS, Hawkshaw M, Sataloff RT. MRSA otorrhea: a case series and review of the literature. ENT Journal 2011;90(2):60-70.(includes 28 references)
  5. Smith A, Buchinsky FJ, Post JC. Eradicating chronic ear, nose, and throat infections: a systematically conducted literature review of advances in biofilm treatment. Otol HNS 2011;144(3):338-347.
  6. Duggal P, Naseri I, Sobol SE. The increased risk of community-acquired methicillin-resistant Staphylococcal aureus neck abscesses in young children. Laryngoscope 2011;121:51-55.
  7. Hobson EC, Moy JD, et al. Malignant otitis externa: evolving pathogens and implications for diagnosis and treatment. Otolaryngol Head Neck Surg 2014; March 26: epub ahead of print.

Last revised June 15, 2014