CDC: Staph super-strain is worrisome’

Step up surveillance to stem spread of deadly super-bugs

As if your plate wasn’t already full with potential quality problems, now it seems you must add antibiotic resistance. And those concerns involve making sure your infection control and quality departments stay in sync.

Resistance has become a full-blown problem of late. (See article on three documented cases, p. 24.) Hospitals nationwide will have to be more aggressive than ever in their surveillance efforts to keep a lid on it. (See article on surveillance in the ICU, p. 28.) One of your top priorities now is to launch a front-line assault and curb this dangerous trend.

"Once you see [antibiotic-resistant staph], don’t let it stay and spread around the hospital until you can’t get rid of it," said Robert Haley, MD, chief of epidemiology at the University of Texas Southwestern Medical Center in Dallas, in a written statement. "Also, we’re going to have to be much more stingy with our use of vancomycin."

Examine the prescribing patterns of your facility’s doctors to see whether they’re misusing antibiotics. Education is the key to rectifying that situation. Specifically, make sure the antibiotic vancomycin (Eli Lilly’s Vancocin) is being used appropriately.

Equally important: Many antibiotic resistance cases come from outside the hospital. Keep on top of your facility’s policies for patient transfer from nursing homes and home health care. These transfers can be virtual petri dishes for vancomycin-resistant enterococci (VRE). Your challenge is to manage those cases and make sure the resistant bug doesn’t spread. While you can’t control what happens outside your facility, you may have to keep transferees hospitalized because the nursing homes they came from are unwilling to take them back — even though their infections likely originated in the nursing home itself.

This need for increased infection surveillance comes when restructuring and managed care have put such programs in peril, notes Haley. With the advent of financial pressures on hospitals to reduce expenditures in the last five years, many hospitals have been cutting back, de-emphasizing, and reducing their infection control programs. The worst-case scenario is a resistant case evading attention because of poor surveillance, and becoming indigenous before it is recognized. It can move into your hospital via a patient from a hospital where resistance is endemic, spread within your hospital, and then bounce to other hospitals. Infection control is not a luxury you can cut back on when your budget gets tight.

Hospitals don’t routinely screen for VRE

"The CDC [Centers for Disease Control and Prevention in Atlanta] has come out with vancomycin guidelines, but the problem lies in enforcing them," explainsPaul J. Deziel, PA-C, MHA, a physician assistant in the division of infectious disease at The Grace Hospital, a division of Wayne State University School of Medicine in Detroit.(See article on CDC guidelines, p. 25.)The CDC has left the VRE transfer issue for individual states to resolve, however, and there have been problems — particularly between hospitals and nursing homes. The CDC’s Hospital Infection Control Practices Advisory Committee (HICPAC) guidelines do not recommend routine screening of patients for VRE, but do note that those wishing to do so can reduce the costs of testing by targeting efforts to those patients "who have been admitted from a facility, such as a tertiary care hospital or a chronic-care facility where VRE are known to be present."1

As a result, most U.S. hospitals do not routinely screen patients for VRE on discharge or admission. If a patient is known to be colonized or infected prior to transfer, the information is routinely added in the discharge summary, according to an infection control professional at a New York City hospital.

"It’s usually part of the information with the patient, but we have had some problems here with patients being transferred in with [VRE] from nursing homes," says Kathleen Jacob, RN, BSN, CIC, nurse epidemiologist at Columbia Presbyterian Medical Center. Most such omissions are due to the transferring facility not being aware that the patient is VRE-colonized. It would probably not be practical or affordable for hospitals to adopt a policy of routinely screening all patients on discharge or transfer, Jacobs adds.

"There are patients we have with VRE who are clearly identified and are on isolation during their entire hospitalization," she says. "We can’t guarantee that we are identifying everybody with these organisms, but I think we are identifying most of them."

Constraints on prescribing are difficult. "Some doctors say they don’t want to be told what to use," explains Deziel, "and it’s hard to pit their clinical judgment against yours. All you can do is try to educate them, show them the existing problems and show them the documents that are put out, and hope that they’ll learn as they go along."

Attempts to decrease use of a drug — especially a potent, broad-spectrum antibiotic that may be very effective in an individual patient — run against the time-honored medical mindset in this country, notes William Schaffner, MD, professor of infectious diseases and chairman of the department of preventive medicine at the University of Vanderbilt School of Medicine in Nashville, TN. "It is clear there is a great overuse of antibiotics, but that is very difficult to [change] in a country that values individual decision-making," he says. "Constraints on prescribing come slowly and by the hardest [means] in this country." Doctors are trained to think, "What is the best I can do for the patient in front of me?"

But you must discourage indiscriminate misuse of vancomycin. Make sure your facility’s medical staff are aware of these issues. (See article on vancomycin abusers on p. 26, and guidelines for vancomycin use on p. 27.) The antibiotic’s improper and random use weakens its effectiveness in combating Staphylococcus aureus infections. It has been estimated that vancomycin is used inappropriately 50% of the time. Physicians and other health care professionals must be educated to use vancomycin and similar antimicrobials as appropriate and necessary. And the public should be educated not to pressure physicians to prescribe unnecessary antibiotics.

In a statement on the emergence of the drug-resistant strain of staph, William Jarvis, MD, an epidemiologist and acting director of the CDC’s hospital infection program, said the trend is largely a result of doctors overprescribing vancomycin when less potent drugs would have worked just as well. "The more a strain of bacteria comes into contact with a given antibiotic, the more opportunities it has to figure out a way to resist that drug’s effects," said Jarvis.

"One of the areas where we can cut back vancomycin use is after the sensitivities come back," says Timothy Leach, MD, MPH, chief of infection control at the VA Medical Center in East Orange, NJ. He says he finds that even after a staph isolate returns methicillin-sensitive, people still use vancomycin. "When I do consults and one of the dialysis patients gets admitted [with] a methicillin-sensitive staph bacteremia, [we] switch him over to a beta-lactam instead of vancomycin. Beta-lactams are considered the drug of choice for sensitive organisms." Leach recommends oxacillin or nafcillin.

Two new antibiotics are undergoing clinical trials. Rhone-Poulenc Rorer’s Synercid, a combination of two antibodies that work synergistically and are effective against VRE, will be submitted to the FDA shortly. Synercid was effective in lab tests against the first Japanese strain of vancomycin intermediate-resistant Staphylococcus aureus (VISA). In addition, a Canadian biopharmaceutical company has developed a peptide capable of restoring vancomycin’s antibiotic activity against VRE. Micrologix’s Enhancin has restored the drug’s effectiveness in vitro, and studies show that combining Enhancin with vancomycin may overcome resistance. Even if those emerging drugs are effective when introduced, resistance will probably develop to them as time goes on unless surveillance is stepped up and antibiotic abuse is stanched.

What is the connection between VRE and antibiotic-resistant staph? "Gram-positive enterococcus has been shown to pass vancomycin resistance to Staphylococcus aureus," explains Rob Stanton, PharmD, clinical pharmacist at Cabell Huntington Hospital in Huntington, WV. "Enterococcus faecium is intrinsically resistant to most drugs, including vancomycin. People do get infected with the bacterium, but it’s not a very virulent organism, and people don’t get very sick. However, the problem is that E. faecium has been showing up more and more lately, and the organism has the potential to transfer resistance to staph, a very virulent organism. That’s where the real concern lies."

Because VREs are resistant to other antibiotics as well as vancomycin, that leaves few if any effective therapeutic options. Patients with resistant infections have a death rate of 37%, significantly higher than the 16% mortality in patients whose infection responds to vancomycin.

Combining antibiotics that have different mechanisms may be the only means available to deal with this problem. A team at Northwestern University Medical School in Chicago investigated the use of synergy, or combination, to counteract enterococci resistance.2 Study participants received high-dose ampicillin, ampicillin/ sulbactam, and trovafloxacin, alone and in combination against 24 unrelated strains of VRE. The trovafloxacin-ampicillin/sulbactam combination was effective against some strains. Trovafloxacin is expected to be approved by the FDA as Hospital Peer Review goes to press.

"A very high dose of ampicillin/sulbactam — 20 to 30 grams a day — is most useful in treating resistant patients," says Lance R. Peterson, MD, professor of pathology at Northwestern and one of the investigators. Ampicillin is cell-wall-active, meaning it works by punching a hole in the bacteria’s cell wall. "Trovafloxacin will be especially useful for treating the multidrug-resistant pneumonias," he continues. "It has a unique mechanism of action against highly resistant pneumococcus compared to the other quinolones that are out there."

Reference

1. Hospital Infection Control Practices Advisory Committee. Recommendations for preventing the spread of vancomycin resistance. MMWR 1995; 44:(no. RR-12)1-13; or Infect Control Hosp Epidemiol 1995; 16:105-113.

2. Mekonen ET, Noskin GA, Hacek DM, Peterson LR. Successful treatment of persistent bacteremia due to vancomycin-resistant, ampicillin-resistant Enterococcus faecium. Microb Drug Resis 1995; 1:249-253.

Suggested reading

Centers for Disease Control and Prevention. Staphylococcus aureus with reduced susceptibility to vancomycin — United States, 1997. MMWR 1997; 46:765-766.

Centers for Disease Control and Prevention. Update: Staphylococcus aureus with reduced susceptibility to vancomycin — United States, 1997. MMWR 1997; 46:813-814.

Centers for Disease Control and Prevention. Reduced susceptibility of Staphylococcus aureus to vancomycin — Japan, 1996. MMWR 1997; 46:624-626.

Centers for Disease Control and Prevention. Interim guidelines for prevention and control of staphylococcal infection associated with reduced susceptibility to vancomycin. MMWR 1997; 46:626-628.