Methicillin-Resistant Staphylococcus aureus (MRSA)

1
Antimicrobial (Drug) Resistance
Methicillin-Resistant Staphylococcus aureus
(MRSA)

• By Paul Parks RN
• Legal Nurse Consultant

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Overview of MRSA

• During the past four decades, a type of bacteria
  has evolved from a controllable nuisance into a
  serious public health concern. This bacterium is
  known as methicillin-resistant Staphylococcus
  aureus, or MRSA. About one-third of people in the
  world have S. aureus bacteria on their bodies at
  any given time, primarily in the nose and on the
  skin. The bacteria can be present without causing
  an active infection. Of the people with S. aureus
  present, about 1 percent has MRSA, according to
  the Centers for Disease Control and Prevention
  (CDC).

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MRSA can be categorized according to where the
infection was acquired hospital-acquired MRSA
(HA-MRSA) or community associated MRSA
(CA-MRSA).
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Hospital-acquired MRSA (HA-MRSA)

• HA-MRSA is acquired in the hospital setting and
  is one of many hospital-acquired infections
  exhibiting increased antimicrobial resistance.
  HA-MRSA has increased during the past decade due
  to a number of factors including an increased
  number of immunocompromised and elderly patients,
  an increase in the number of invasive procedures
  e.g., advanced surgical operations and life
  support treatments, and failures in infection
  control measures such as hand washing prior to
  patient contact and removal of non-essential
  catheters.

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Community associated MRSA (CA-MRSA)

• CA-MRSA is caused by newly emerging strains
  unlike those responsible for HA-MRSA and can
  cause infections in otherwise healthy persons
  with no links to healthcare systems. CA-MRSA
  infections typically occur as skin or soft tissue
  infections, but can develop into more invasive,
  life-threatening infections. CA-MRSA is occurring
  with increasing frequency in the United States
  and around the world and tends to occur in
  conditions where people are in close physical
  contact, such as athletes involved in football
  and wrestling, soldiers kept in close quarters,
  inmates, childcare workers, and residents of
  long-term care facilities.

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The History of Methicillin-Resistant
Staphylococcus aureus (MRSA)

• The S. aureus bacterium, commonly known as staph,
  was discovered in the 1880s. During this era, S.
  aureus infection commonly caused painful skin and
  soft tissue conditions such as boils,
  scalded-skin syndrome, and impetigo. More serious
  forms of S. aureus infection can progress to
  bacterial pneumonia and bacteria in the
  bloodstreamboth of which can be fatal. S. aureus
  acquired from improperly prepared or stored food
  can also cause a form of food poisoning.

7
MRSA History

• In the 1940s, medical treatment for S. aureus
  infections became routine and successful with the
  discovery and introduction of antibiotic
  medication, such as penicillin.
• From that point on, however, use of
  antibioticsincluding misuse and overusehas
  aided natural bacterial evolution by helping the
  microbes become resistant to drugs designed to
  help fight these infections. In the late 1940s
  and throughout the 1950s, S. aureus developed
  resistance to penicillin.

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History

• Methicillin, a form of penicillin, was introduced
  to counter the increasing problem of
  penicillin-resistant S. aureus. Methicillin was
  one of most common types of antibiotics used to
  treat S. aureus infections but, in 1961, British
  scientists identified the first strains of S.
  aureus bacteria that resisted methicillin. This
  was the so-called birth of MRSA.

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First Reported Case

• The first reported human case of MRSA in the
  United States came in 1968. Subsequently, new
  strains of bacteria have developed that can now
  resist previously effective drugs, such as
  methicillin and most related antibiotics.
• MRSA is actually resistant to an entire class of
  penicillin-like antibiotics called beta-lactams.
  This class of antibiotics includes penicillin,
  amoxicillin, oxacillin, methicillin, and others.

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Evolution of S. Aureus

• S. aureus is evolving even more and has begun to
  show resistance to additional antibiotics. In
  2002, physicians in the United States documented
  the first S. aureus strains resistant to the
  antibiotic, vancomycin, which had been one of a
  handful of antibiotics of last resort for use
  against S. aureus. Though it is feared that this
  could quickly become a major issue in antibiotic
  resistance, thus far, vancomycin-resistant
  strains are still rare at this time.

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Transmission of MRSA

• Today, S. aureus has evolved to the point where
  experts refer to MRSA in terms ranging from a
  considerable public health burden to a crisis.
  The bacteria have been classified into two
  categories based on where infection is first
  acquired.
• The first category is Hospital Acquired-MRSA and
  the second is Community-Associated-MRSA

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Hospital-Acquired (HA)-MRSA

• HA-MRSA has been recognized for decades and
  primarily affects people in healthcare settings,
  such as those who have had surgery or medical
  devices surgically implanted. This source of MRSA
  is typically problematic for the elderly, for
  people with weakened immune systems, and for
  patients undergoing kidney dialysis or using
  venous catheters or prosthetics.

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Hospital-Acquired (HA)-MRSA

• A study published in 2005 found that nearly 1
  percent of all hospital in-patient stays, or
  292,045 per year, were associated with S. aureus
  infection. The study reviewed nearly 14 million
  patient discharge diagnoses from 2000 and 2001.
  Patients with diagnoses of S. aureus infection,
  when compared with those without the infection,
  had about three times the length of stay, three
  times the total cost, and five times the risk of
  in-hospital death. Notably, the S. aureus
  infections in this hospital study resulted in
  14,000 deaths.

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Community-Associated (CA)-MRSA

• CA-MRSA has only been known since the 1990s.
  CA-MRSA is of great concern to public health
  professionals because of who it can affect.
  Unlike the hospital sources, which usually can be
  traced to a specific exposure, the origin of
  CA-MRSA infection can be elusive. CA-MRSA skin
  infections are known to spread in crowded
  settings in situations where there is close
  skin-to-skin contact when personal items such as
  towels, razors, and sporting equipment is shared
  when personal hygiene is compromised and when
  healthcare is limited.

15
Community-Associated (CA)-MRSA

• Outbreaks of CA-MRSA have involved bacterial
  strains with specific microbiologic and genetic
  differences from traditional HA-MRSA strains, and
  these differences suggest that community strains
  might spread more easily from person to person
  than HA-MRSA. While CA-MRSA is resistant to
  penicillin and methicillin, they can still be
  treated with other common-use antibiotics.

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Community-Associated (CA)-MRSA

• CA-MRSA most often enters the body through a cut
  or scrape and appears in the form of a skin or
  soft tissue infection, such as a boil or abscess.
  The involved site is red, swollen, and painful
  and is often mistaken for a spider bite. Though
  rare, CA-MRSA can develop into more serious
  invasive infections, such as bloodstream
  infections or pneumonia, leading to a variety of
  other symptoms including shortness of breath,
  fever, chills, and death. CA-MRSA can be
  particularly dangerous in children because their
  immune systems are not fully developed.

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Community-Associated (CA)-MRSA

• You should pay attention to minor skin
  problemspimples, insect bites, cuts, and
  scrapesespecially in children. If the wound
  appears to be infected, see a healthcare
  provider.
• Researchers continue to study information about
  these cases in an attempt to determine why
  certain groups of people become ill when exposed
  to these strains. Researchers also continue to
  try to understand why high-incidence areas may
  appear. For example, for unknown reasons, severe
  outbreaks have occurred in Alaska, Georgia, and
  Louisiana.

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Diagnosis of MRSA

• To diagnose S. aureus, a sample is obtained from
  the infection site and sent to a microbiology
  laboratory for testing. If S. aureus is found,
  the organism should be further tested to
  determine which antibiotic would be effective for
  treatment.
• Doctors often diagnose MRSA by checking a tissue
  sample or nasal secretions for signs of
  drug-resistant bacteria. Current diagnostic
  procedures involve sending a sample to a lab
  where it is placed in a dish of nutrients that
  encourage bacterial growth (a culture).

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Diagnosing MRSA

• It takes about 48 hours for the bacteria to
  grow. However, newer tests that can detect staph
  DNA in a matter of hours are now becoming more
  widely available. This will help healthcare
  providers decide on the proper treatment regimen
  for a patient more quickly, after an official
  diagnosis has been made.
• In the hospital, you might be tested for MRSA if
  you show signs of infection, or if you are
  transferred to a hospital from another healthcare
  setting where MRSA is known to be present. You
  also might be tested if you have had a previous
  history of MRSA.

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Treatment for MRSA Infections

• Healthcare providers can treat many S. aureus
  skin infections by draining the abscess or boil
  and may not need to use antibiotics. Draining of
  skin boils or abscesses should only be done by a
  healthcare provider.
• For mild to moderate skin infections, incision
  and drainage by a healthcare provider is the
  first-line treatment. Before prescribing
  antibiotics, your provider will consider the
  potential for antibiotic resistance.

21
Treatment for MRSA Infections

• Thus, if MRSA is suspected, your provider will
  avoid treating you with beta-lactam antibiotics,
  a class of antibiotic observed not to be
  effective in killing the staph bacteria. For
  severe infection, doctors will typically use
  Vancomycin intravenously.
• NOTE Vancomycin is extremely nephrotoxic and can
  lead to acute renal failure (ARF).
• Even with careful monitoring of peak and trough
  levels acute renal failure is always a
  possibility.

22
MRSA Prevention

• The best defense against spreading MRSA is to
  practice good hygiene, as follows
• Keep your hands clean by washing thoroughly with
  soap and water. Scrub them briskly for at least
  15 seconds, then dry them with a disposable towel
  and use another towel to turn off the faucet.
  When you dont have access to soap and water,
  carry a small bottle of hand sanitizer containing
  at least 62 percent alcohol.
• Always shower promptly after exercising.

23
MRSA Prevention

• Keep cuts and scrapes clean and covered with a
  bandage until healed. Keep wounds that are
  draining or have pus covered with clean, dry
  bandages. Follow your healthcare providers
  instructions on proper care of the wound. Pus
  from infected wounds can contain S. aureus and
  MRSA, so keeping the infection covered will help
  prevent the spread to others. Bandages or tape
  can be discarded with regular trash. Avoid
  contact with other peoples wounds or bandages.
  Avoid sharing personal items, such as towels,
  washcloths, razors, clothes, or uniforms.

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MRSA Prevention

• Wash sheets, towels, and clothes that become
  soiled with water and laundry detergent use
  bleach and hot water if possible. Drying clothes
  in a hot dryer, rather than air-drying, also
  helps kill bacteria in clothes. Tell any
  healthcare providers who treat you if you have or
  had an S. aureus or MRSA skin infection. If you
  have a skin infection that requires treatment,
  ask your healthcare provider if you should be
  tested for MRSA. Many healthcare providers
  prescribe drugs that are not effective against
  antibiotic-resistant staph, which delays
  treatment and creates more resistant germs.

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Researching the MRSA Superbug

• Healthcare providers are fighting back against
  MRSA infection by tracking bacterial outbreaks
  and by investing in products, such as
  antibiotic-coated catheters and gloves that
  release disinfectants.
• Community-associated strains are notably
  effective at causing severe infections in
  otherwise healthy individuals and are different
  from the strains that cause hospital infections.
  As these strains begin to appear in hospitals
  where immuno-compromised patients are at risk, it
  becomes increasingly important to understand how
  CA-MRSA can colonize and invade healthy people.

26
Researching MRSA

• The National Institute of Allergy and Infectious
  Diseases (NIAID) funds basic and translational
  research with the ultimate goal to develop and
  promote enhanced diagnostics, better therapeutic
  treatments, and new vaccines that are effective
  against Methicillin-Resistant Staphylococcus
  aureus (MRSA). Given the increasing prevalence of
  MRSA in both hospital and community settings, it
  is important to understand how MRSA spreads, the
  factors that influence the severity of disease
  (virulence factors), and how best to treat MRSA
  infections.

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Researching MRSA

• Virulence factors can include proteins that allow
  the bacteria to adhere to and colonize the host,
  to invade host cells, to inhibit the host immune
  response, and to poison and damage host cells.

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Virulence Associated Factors of Community-
Associated MRSA (CA-MRSA)

• Drs. Michael Otto and Frank DeLeo, and their
  colleagues at NIAIDs Rocky Mountain Laboratories
  (RML), recently described the essential role of
  the phenol-soluble modulin (PSM) protein family
  in CA-MRSA disease severity. These PSM proteins
  are able to destroy most immune cells,
  particularly white blood cells that help people
  fight off infection. While these proteins may not
  be the only virulence factors produced by
  CA-MRSA, they have been identified as major
  factors in the disease severity of CA-MRSA.

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How CA-MRSA Spreads Among Households

• Dr. Robert Daum, a researcher at the University
  of Chicago, is seeking to determine the best
  methods for containing, preventing, and treating
  CA-MRSA infections by understanding the
  circumstances that facilitate the transfer of
  CA-MRSA among household members. The study will
  determine how easily CA-MRSA is transferred from
  the initial infected person to other members
  within his/her household and at what rate
  household members become colonized or infected
  with CA-MRSA.

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The Spread of MRSA Among Households

• The rate of CA-MRSA spread among household
  members will be compared to the rate of spread
  that occurs between a person infected with
  hospital-acquired MRSA (HA-MRSA), and other
  members within a household.

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Strategies to Optimize the Use of Existing
Antibiotics for MRSA Therapy

• Two clinical trials are underway to define the
  optimal treatment for skin and soft tissue
  infections caused by CA-MRSA. CA-MRSA strains
  have remained more susceptible to commonly
  available antibiotics than hospital-associated
  MRSA strains therefore, these trials will
  evaluate how effective off-patent antimicrobials
  are in treating uncomplicated cases of skin and
  soft tissue infections caused by CA-MRSA
  bacteria.

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Strategies to Optimize the Use of Existing
Antibiotics for MRSA Therapy

• Off-patent antimicrobials would be a
  cost-effective means of treating these infections
  and would alleviate the use of last-resort
  antibiotics such as Vancomycin, which is
  essential for the treatment of hospital-associated
  MRSA.

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A Few Facts About Vancomycin

• Vancomycin is indicated for the treatment of
  serious, life-threatening infections by
  Gram-positive bacteria which are unresponsive to
  other less toxic antibiotics. In particular,
  vancomycin should not be used to treat
  methicillin-sensitive Staphylococcus aureus
  because it is inferior to penicillins such as
  nafcillin.
• The increasing emergence of vancomycin-resistant
  enterococci has resulted in the development of
  guidelines for use by the Centers for Disease
  Control (CDC) Hospital Infection Control
  Practices Advisory Committee. These guidelines
  restrict use of vancomycin.

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These guidelines restrict use of vancomycin to
the following indications

• treatment of serious infections caused by
  susceptible organisms resistant to penicillins
  (methicillin-resistant Staphylococcus aureus and
  multi-resistant Staphylococcus epidermidis
  (MRSE)) or in individuals with serious allergy to
  penicillins
• pseudomembranous colitis (relapse or unresponsive
  to metronidazole treatment)
• For treatment of infections caused by
  gram-positive microorganisms in patients who have
  serious allergies to beta-lactam antimicrobials.

35
Restricted use of Vancomycin for the following
indications

• Antibacterial prophylaxis for endocarditis
  following certain procedures in
  penicillin-hypersensitive individuals at high
  risk.
• Surgical prophylaxis for major procedures
  involving implantation of prostheses in
  institutions with a high rate of MRSA or MRSE.

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Adverse effects of Vancomycin

• Although vancomycin levels are usually monitored,
  in an effort to reduce adverse events, the value
  of this is not beyond debate.15 Peak and trough
  levels are usually monitored, and for research
  purposes, the area under the curve is also
  sometimes used. Toxicity is best monitored by
  looking at trough values.
• Common adverse drug reactions (1 of patients)
  associated with IV vancomycin include local
  pain, which may be severe and/or
  thrombophlebitis.

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Adverse effects of Vancomycin

• Damage to the kidneys and to the hearing were a
  side effect of the early impure versions of
  vancomycin, and these were prominent in the
  clinical trials conducted in the mid-1950s. Later
  trials using purer forms of vancomycin found that
  nephrotoxicity is an infrequent adverse effect
  (0.11 of patients), but that this is
  accentuated in the presence of aminoglycosides.

38
Red man syndrome

• Vancomycin must be administered in a dilute
  solution slowly, over at least 60 minutes
  (maximum rate of 10 mg/minute for doses gt500 mg).
  This is due to the high incidence of pain and
  thrombophlebitis and to avoid an infusion
  reaction known as the red man syndrome or red
  neck syndrome. This syndrome, usually appearing
  within 410 minutes after the commencement or
  soon after the completion of an infusion, is
  characterized by flushing and/or an erythematous
  rash that affects the face, neck and upper torso.
  These findings are due to non-specific mast cell
  degranulation and are not an IgE mediated
  allergic reaction

39
Red man syndrome

• . Less frequently, hypotension and angioedema may
  also occur. Symptoms may be treated or prevented
  with antihistamines, including diphenhydramine,
  and are less likely to occur with slow infusion.

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Red Man Syndrome
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The Effects of MRSA
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MRSA
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MRSA
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The End

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