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Staph aureus & MRSA

Methicillin resistant Staph aureus (MRSA) infections (meaning none of the penicillins can treat MRSA infections) have recently received a lot of media attention, however MRSA infections are not new. MRSA is a common bacteria that has been around for a long time. MRSA has become increasingly dangerous because it has acquired genes that make it more resistant to antibiotics. MRSA is particularly worrisome because it is resistant to the common antibiotic methicillin, and because some patients can get very ill (and even die). Yet there are still antibiotics other than methicillin to treat MRSA infections, and not all Staph aureus bacteria (S. aureus) are resistant to methicillin. S. aureus resistance: in intensive care units the percent of S. aureus resistant to antibiotics has increased from 37% in 1995 to 60% in 2004. This increased resistance is being seen worldwide.

Where S. aureus is Found

  • 2/3 to 3/4 of us are colonized by S. aureus at some point
  • 20% to 50% of us are colonized at any given time
  • 20% of us are persistently colonized
  • The nose is the most common site of colonization
  • 80% to 90% of serious Staph infections come from bacteria a person has on their skin or in their system

S. aureus Most Common Causes

  • Heart infections (38%)
  • Infections patients get while being in a healthcare facility (13%)
  • Skin and soft tissue infections (20%)
  • Infections in the bones or joints
  • Infections in the blood stream

Types of S. aureus Infections

  • Methicillin sensitive Staph aureus (MSSA)
  • Methicillin resistant Staph aureus (MRSA); which includes: Hospital Acquired MRSA (HA-MRSA), Community-Acquired MRSA (CA-MRSA). Community-Acquired MRSA (CA-MRSA) is the term used for MRSA infections that get started outside the hospital setting. These infections usually presents as a skin infections. Many patients with CA-MRSA will come in for a "spider bite", but the only spider bite that causes a skin infection is the brown recluse spider, and bites from the brown recluse are exceedingly rare. Physicians should consider your "spider bite" to be CA-MRSA until it is proven otherwise!

Treatment of CA-MRSA

  • 75% - 80% of patients with CA-MRSA present with skin infections
  • Many cases can be treated with incision and drainage only - without antibiotics
  • If an antibiotic is required, options for treating CA-MRSA in adults include: Trimethoprim/sulpha DS - 1 to 2 twice daily for 7-10 days; Doxycycline 100mg twice daily for 7-10 days; Clindamycin 300-450mg twice daily for 7-10 days (resistance to this is forming)

Treatment of recurrent CA-MRSA furunculosis (boils): There is little evidence that there is a long-term benefit to trying to get rid of CA-MRSA in a patient who is a chronic carrier. Potential toxicity of agents, their cost, and the potential for creating resistance will need to be considered by your doctor.

Options for Treatment

  • A combination of topical, mucosal, and systemic antibiotics, such as oral Trimethoprimsulfa, nasal mupirocin (Bactroban), or chlorhexidine showers (Hibiclens) 5 times a day
  • Bleach baths (1 teaspoon of bleach per gallon of water) x 10 minutes 2 times/wk
  • Environmental cleaning (bedclothes, towels, surfaces)
  • More controversial is the consideration of treating people around you
  • There may be some potential transmission from pets, so pet reservoirs need to be considered for recurrent cases
  • Getting CA-MRSA from your environmental transmissions may need to be considered in some cases


  • How can I protect myself from getting MRSA? The main way to protect against MRSA is by frequent and thorough hand washing.
  • Is MRSA a reportable disease? Invasive MRSA infections in hospitals (i.e., positive blood cultures) are reportable. But routine positive cultures from skin and soft tissues are not.
  • What is the best anti-bacterial soap for MRSA? Hibiclens - available over-the-counter.
  • Is Purell effective? All alcohol gels and foams like Purell are very effective against MRSA.
  • Should Bactroban be used to prevent MRSA colonization? The routine use of Bactroban in the nose has not been shown to prevent colonization.
  • Should family members of MRSA patients use Hibiclens washes? Family members of patients who are MRSA carriers should scrub weekly with Hibiclens. They should scrub more often if skin eruptions are present.
  • How long does MRSA stay potentially infective in the environment? Days to weeks.

Source: MedScape