Infection Control Today - 03/2002: Fighting Resistance

Fighting Resistance

By Michelle Gardner

Duringthe past, indiscriminate use of antibiotics has given once-susceptible bacteriathe chance to develop defenses against antibiotics, thus providing theopportunity for resistant strains to flourish. Reports of vancomycin-resistant enterococcus(VRE) and methicillin-resistant Staphylococcus aureus (MRSA) haveincreased in oncology units of large teaching hospitals, and nursing homes,long-term care facilities, and community hospitals, respectively.

Both Enterococci and Staphylococcus are part of the body'snormal flora, which is considered "good" bacteria and essential forhuman health.⁴ But if the body's natural defense system breaks down (i.e.,after an invasive procedure, trauma, or chemotherapy), these normally benignbacteria can invade tissue, proliferate, and cause infection.

At one time, enterococcal infections were easily treated with high doses ofpenicillin or ampicillin, which progressed to aminoglycosides, then vancomycin.Many clinicians suspect that over reliance on vancomycin led to the developmentof VRE, which isn't easily treated with any antibiotic.

Who's at risk?

Patients most at risk for VRE include, but are not limited to,immunosuppressed patients or those with severe underlying disease; elderlypatients, especially those who've had prolonged or repeated hospital admissions;patients with wounds with an opening to the pelvic or intra-abdominal area,including surgical wounds, burns, and pressure ulcers; and patients exposed tocontaminated equipment or to a VRE-positive patient.

According to the Centers for Disease Control and Prevention (CDC), infectedpatients carry VRE and show clinical signs or symptoms of disease. Colonizedpatients carry VRE but do not have clinical signs or symptoms of infection.Patients are usually colonized in the gastrointestinal tract and occasionally inthe urinary tract. The goal of screening is to identify as many colonizedpatients as possible so that infection control measures can be implemented todecrease transmission and reduce the number of patients infected with VRE.

VRE is spread through direct contact between patient and caregiver, orpatient to patient. It also can be spread through patient contact withcontaminated surfaces. VRE has been detected on patient gowns, bed linens, andhandrails.

Understanding MRSA

Patients most at risk for MRSA include immunosuppressed patients, burnpatients, intubated patients, and those with central venous catheters, surgicalwounds, or dermatitis.

Risk factors include prolonged hospital stays, extended therapy with multipleor broad-spectrum antibiotics, and close proximity to those colonized orinfected with MRSA.

Like VRE, MRSA enters health care facilities through an infected or colonizedpatient or colonized healthcare worker (HCW). Although MRSA has been recoveredfrom environmental surfaces, it's transmitted mainly on HCWs' hands. Typically,MRSA colonization is diagnosed by isolating bacteria from nasal secretions as40% of adults and most children become transient nasal carriers.

The following guidelines apply when caring for a patient with MRSA or VRE:

• Wash your hands before and after caring for any patient. Good handwashing is the most effective way to prevent VRE and MRSA from spreading.

• Use an antiseptic soap such as chlorhexidine. Enterococci have been cultured from HCWs' hands after they have washed with a milder soap. One study showed that without proper hand washing, MRSA could survive on HCWs' hands for 3 hours.

• Institute contact isolation precautions, one of the three types of transmission-based precautions. (The others are airborne and droplet precautions.) This includes wearing gloves and a gown if you might be in direct patient contact, giving the patient a private room, using dedicated equipment, and disinfecting the environment.

• Be particularly prudent in caring for a patient with an ileostomy, colostomy, or draining wound not contained by a dressing--again, especially with VRE patients.

• Make sure family and friends know why they need to wear protective garb when they visit the patient, how to put it on, and how to dispose of it. Before they leave the room, make sure they remove protective equipment and wash their hands.

• As always, use aseptic techniques for such procedures as suctioning, catheterizing, and inserting intravenous lines. Any breach in aseptic technique may allow pathogens to gain a foothold.

More bad bugs

Besides MRSA and VRE, antibiotic-resistant organisms continue to appear:

• Penicillin-resistant Streptococcus pneumoniae and Neisseria gonorrhoeae, as well as antibiotic-resistant Mycobacterium tuberculosis.

S. aureus intermediately resistant to vancomycin (known by the acronymVISA). To prevent the rise of VRSA and other antibiotic-resistant organisms, usesimilar techniques for preventing the spread of VRE and MRSA. Among the mostimportant measures: good hand washing, barrier precautions, and continuedvigilance against the spread of these organisms.