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March 2003

VISA/VRSA
Vancomycin-Intermediate/Resistant Stapylococcus aureus

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 g/ml, and classified as VRSA if the vancomycin MIC is >32 g/ml.

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.

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.

What should I do if I think I have a Staph, MRSA, VISA, or VRSA infection?

See your healthcare provider.

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.

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.

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.

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.

Department of Health and Human Services, Centers for Disease Control and Prevention, Safer-Healthier-People