Vancomycin Intermittent-Resistant Staphylococcus Aureus

Vancomycin intermittent-resistant Staphylococcus aureus (VISA) is a mutation of a bacterium that is spread easily by direct person-to-person contact. It was first discovered in mid-1996 when clinicians discovered the microbe in a Japanese infant's surgical wound. Similar isolates were later reported in Michigan and New Jersey. Both patients had received multiple courses of vancomycin for methicillin-resistant S. aureus infections.

Another mutation, vancomycin-resistant S. aureus (VRSA), is fully resistant to vancomycin.

Causes

VISA or VRSA enters a health care facility through an infected or colonized (symptom-free but infected) patient or colonized health care worker. It's spread during direct contact between the patient and caregiver or patient-to-patient. It may also be spread through patient contact with contaminated surfaces, such as an over-bed table. It's able to live for weeks on surfaces. It has been detected on patient gowns, bed linens, and handrails.

A colonized patient is more than 10 times as likely to become infected with the organism, such as through a breach in the immune system. Patients most at risk for resistant organisms include immunosuppressed patients or those with severe underlying disease; patients with a history of taking vancomycin,third-generation cephalosporins, or antibiotics targeted at anaerobic bacteria (such as Clostridium difficile); patients with indwelling urinary or central venous catheters; elderly patients, especially those with prolonged or repeated hospital admissions; patients with malignancies or chronic renal failure; patients
undergoing cardiothoracic or intra-abdominal surgery or organ transplants; patients with wounds with an Dpening to the pelvic or intra-abdominal area, such as surgical wounds, burns, and pressure ulcers; patients with enterococcal bacteremia, often associated with endocarditis; and patients exposed to contaminated equipment or to a patient with the infecting microbe.

Complications

VISA can cause sepsis, multisystem organ involvement, and death in an immunocompromised patient.

Diagnostic tests

The causative agent may be found incidentally when culture results show the organism. A person with no signs or symptoms of infection is considered colonized if VISA or VRSA can be isolated from stool or arectal swab.

Treatment

There is virtually no antibiotic to combat VISA or VRSA. Because no single antibiotic is currently available, the doctor may opt not to treat an infection at all. Instead, he may stop all antibiotics and simply wait for normal bacteria to repopulate and replace the strain. Combinations of various drugs may also be used, depending on the source of the infection.

To prevent the spread of VISA and VRSA, some hospitals perform weekly surveillance cultures on at risk patients in intensive care units or oncology units and those transferred from a long-term care facility. Any colonized patient is then placed in contact isolation until his culture is negative or he's discharged. Colonization can last indefinitely, and no protocol is established for the length of time a patient should remain in isolation.

Recently, the Centers for Disease Control and Prevention and the Hospital Infection Control Practices Advisory Committee proposed a two-level system of precautions to simplify isolation for resistant organisms. The first level calls for standard precautions, which incorporate features of universal blood and body fluid precautions and body substance isolation precautions. The second level calls for transmission-based precautions, implemented when a particular infection is suspected.