Three cases of resistant staph cause concern
The culprit: Vancomycin misuse
Put Staphylococcus aureus on your hospital’s hit list. It’s the leading cause of costly, quality-eroding nosocomial infections. In the preantibiotic era, an outbreak could shut down a hospital wing. Staph is responsible for 13% of the nation’s 2 million hospital infections that kill 60,000 to 80,000 people each year. The gram-positive organism causes, among other things, rapidly fatal septic infections in surgical patients.Twenty years ago, most bacteria responded to a wide range of antibiotics. In the early 80s, a strain resistant to methicillin (Staphcillin) — then the drug of choice — emerged. Today, methicillin is useless against half of staph infections, and in recent years staph has become increasingly resistant to other antibiotics as well. Until now, an IV dose of vancomycin was the silver bullet — the only way to combat some multiple-resistant strains. It was one drug considered totally effective.
Two occurrences of vancomycin intermediate-resistant S. aureus (VISA) in this country were confirmed last fall by the Centers for Disease Control and Prevention (CDC) in Atlanta. Both involved methicillin-resistant S. aureus (MRSA) infections that went on to develop resistance to vancomycin. A year prior to that, six hospitals in Japan acknowledged infections by resistant staph. The first case was a 4-month-old Tokyo boy who acquired staph infection while being treated with vancomycin for 29 days for heart problems. Resistance developed. When ampicillin/ sulbactam was added to his regimen, at first he improved, then relapsed. Additional therapy with other antibiotic combinations cleared the infection.
The Japanese staph strain and those that followed in the United States showed an intermediate level of resistance — one step from immunity — because the bacteria eventually succumbed to a different antibiotic. But, said the CDC report, the outbreaks "may be an early warning that S. aureus strains with full resistance to vancomycin may emerge."
The first U.S. VISA incident involved a Michigan patient with kidney failure who was using a home dialysis system. After 18 months of repeated IV treatments with vancomycin for periodic abdominal staph infections, the drug lost effect. Tests by the CDC showed the staph had developed a mechanism for surviving moderate levels of the antibiotic.
"It’s become common practice in some dialysis centers to give a bolus of vancomycin if a patient develops a fever or pain at the catheter site or some other nonspecific symptom," said William Jarvis, MD, an epidemiologist and acting director of the hospital infection program of the CDC, in a statement regarding the outbreak. "That practice has to stop. We have to recommend that . . . if [an infection] is susceptible to other antibiotics, then we must use those instead." (See related article on peritoneal dialysis, p. 30.) The Michigan patient’s infection eventually responded to a combination of antibiotics after vancomycin failed.
A Camden, NJ, patient provided the third documented VISA case. He had a history of heart disease, arthritis, and other chronic illnesses when he developed an infection that proved "moderately" resistant to vancomycin. Over the previous five months he’d been treated repeatedly with the antibiotic. The patient’s resistant infection was eventually eradicated with a trio of antibiotics, and to date he’s had no recurrence.
"I think it is a fair assumption that we are going to see more of these cases," warns David Bell, MD, assistant director for antimicrobial resistance at the CDC’s national center for infectious diseases. "If the pattern holds up, it will be among people who have received vancomycin intermittently for a lengthy period." The CDC has received a number of other reports of VISA isolates in patients, but thus far has not confirmed any other cases.
In each of the documented resistance cases, the hospitals took precautions to prevent the spread of the staph organisms, which collect on clothing, blankets, walls, and medical equipment. Although the epidemiology of vancomycin-resistant enterococci (VRE) is not fully understood, and most enterococcal infections have been attributed to the patient’s endogenous flora, recent studies have demonstrated that VRE can be spread directly from patient to patient or indirectly on the hands of personnel or contaminated environmental surfaces and patient-care equipment.
"We use double-gloving because of the concern for environmental contamination," says Karen Green, RN, CIC, infection control coordinator at Mount Sinai and Princess Margaret Hospitals in Toronto. "As soon as you finish your contact with the patient, the outer pair of gloves comes off for handling other things in the room. We aim to minimize transmission from the patient to all the environmental surfaces we touch in the room."
Green urges hospital infection control professionals to alert other facilities when a patient being transferred is known to have a multidrug-resistant organism or is coming from a facility where such pathogens are endemic. Likewise, patients colonized or infected with such pathogens should be educated to alert caregivers of their medical history when later readmitted, she adds.
"The frustrating thing about VRE is that it is not inevitable," says Allison McGeer, MD, director of infection control at Mount Sinai and Princess Margaret Hospitals in Toronto. "You can control it, and it is cost-effective to control it. There is no doubt that efforts put into detecting and eradicating VRE early will pay off in terms of costs. The problem is that they cost money up front. If you are in a VRE-free area, at the moment you are unlikely to get VRE evolving in your area, but it will be imported. If you want to detect it and keep it out of your area, you have to have a system for picking up the VRE that is coming in."
(Editor’s note:For more information on VISA, see related story in our sister publication, Hospital Infection Control, June 1997, pp. 97-100.)
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