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What is Staphylococcus
aureus?
Staphylococcus aureus, often
simply referred to simply as “staph”, are bacteria
commonly found on the skin and in the noses of healthy people.
Occasionally, staph can cause infection; staph bacteria are one
of the most common causes of skin infections in the United States.
Most of these infections are minor (such as pimples, boils, and
other skin conditions) and most can be treated without antimicrobial
agents (also known as antibiotics or antibacterial agents). However,
staph bacteria can also cause serious and sometimes fatal infections
(such as bloodstream infections, surgical wound infections, and
pneumonia). In the past, most serious staph bacterial infections
were treated with a type of antimicrobial agent related to penicillin.
Over the past 50 years, treatment of these infections has become
more difficult because staph bacteria have become resistant to
various antimicrobial agents, including the commonly used penicillin-related
antibiotics.
What are VISA and VRSA?
VISA and VRSA are specific types of antimicrobial-resistant
staph bacteria. While most staph bacteria are susceptible to the
antimicrobial agent vancomycin some have developed resistance.
VISA and VRSA cannot be successfully treated with vancomycin because
these organisms are no longer susceptibile to vancomycin. However,
to date, all VISA and VRSA isolates have been susceptible to other
Food and Drug Administration (FDA) approved drugs.
How do VISA and VRSA
get their names?
Staph bacteria are classified as VISA or VRSA
based on laboratory tests. Laboratories perform tests to determine
if staph bacteria are resistant to antimicrobial agents that might
be used for treatment of infections. For vancomycin and other
antimicrobial agents, laboratories determine how much of the agent
it requires to inhibit the growth of the organism in a test tube.
The result of the test is usually expressed as a minimum inhibitory
concentration (MIC) or the minimum amount of antimicrobial agent
that inhibits bacterial growth in the test tube. Therefore, staph
bacteria are classified as VISA if the MIC for vancomycin is 8-16
µg/ml, and classified as VRSA if the vancomycin MIC is >32
µg/ml. top
How common are VISA
and VRSA infections?
VISA and VRSA infections are rare. Only eight
cases of infection caused by VISA (Michigan
1997, New
Jersey 1997, New
York 1998, Illinois
1999, Minnesota 2000, Nevada
2000, Maryland 2000, and Ohio 2001) and two cases of infection
caused by VRSA (Michigan
2002 and Pennsylvania
2002) have been reported in the United States. top
Who gets VISA and VRSA
infections?
Persons that developed VISA and VRSA infections
had several underlying health conditions (such as diabetes and
kidney disease), previous infections with methicillin-resistant
Staphylococcus aureus (MRSA),
tubes going into their bodies (such as intravenous [IV] catheters),
recent hospitalizations, and recent exposure to vancomycin and
other antimicrobial agents. top
What should I do if
I think I have a Staph, MRSA, VISA, or VRSA infection?
See your healthcare provider. top
Are VISA and VRSA infections
treatable?
Yes. To date, all VISA and VRSA isolates have
been susceptible to several Food and Drug Administration (FDA)
approved drugs. top
How can the spread of
VISA and VRSA be prevented?
Use of appropriate infection control practices
(such as wearing gloves before and after contact with infectious
body substances and adherence to hand
hygiene) by healthcare personnel can reduce the spread of
VISA and VRSA.
Because VISA and VRSA are only part of the
larger problem of antimicrobial resistance in healthcare settings,
CDC has started a Campaign
to Prevent Antimicrobial Resistance. The campaign centers
around four strategies that clinicians can use to prevent antimicrobial
resistance: prevent infections; diagnose and treat infections
effectively; use antimicrobials wisely; and prevent transmission.
A series of evidence-based steps are described that can reduce
the development and spread of resistant organisms such as VISA
and VRSA. top
What should I do if
a family member or close friend has VISA or VRSA?
VISA and VRSA are types of antibiotic-resistant
staph bacteria. Therefore, as with all staph bacteria, spread
occurs among people having close physical contact with infected
patients or contaminated material like bandages. Therefore, persons
having close physical contact with infected patients while they
are outside of the healthcare setting should: (1) keep their hands
clean by washing thoroughly with soap and water, (2) avoid contact
with other people’s wounds or material contaminated from
wounds. If you visit a friend or family member who is infected
with VISA or VRSA while they are hospitalized, follow the hospital’s
recommended precautions. top
What is CDC doing to
address VISA and VRSA?
CDC has established several programs to promote
appropriate use of antimicrobial agents because inappropriate
antibiotic use is a major cause of antimicrobial resistance. One
program that focuses on patients in healthcare facilities is the
Campaign
to Prevent Antimicrobial Resistance. The campaign centers
around four strategies that clinicians can use to prevent antimicrobial
resistance: prevent infections; diagnose and treat infections
effectively; use antimicrobials wisely; and prevent transmission
of infections. A series of evidence-based steps are described
that can reduce the development and spread of resistant organisms,
such as VISA and VRSA. CDC also has published guidance to prevent
the spread of vancomycin resistance in healthcare settings.
In addition to providing guidance for
clinicians and infection control personnel, CDC is also working
with state and local health agencies, healthcare facilities and
clinical microbiology laboratories to ensure that laboratories
are using proper methods to detect VISA and VRSA (S.E.A.R.C.H.).
Recently CDC developed a training tool for laboratorians to enhance
their understanding and improve their proficiency in performing
antimicrobial susceptibility testing (M.A.S.T.E.R.).
Accurate antimicrobial susceptibility test results not only help
physicians choose the best therapy for their patients, but guide
infection control efforts to the most serious infections.
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