Emergence of resistant staph puts new emphasis on IC guidelines

Workers could contract and spread emerging pathogen

Health care workers must maintain strict adherence to infection control precautions if the threat of vancomycin resistance is to be minimized, according to interim guidelines released by the U.S. Centers for Disease Control and Prevention.1

The guidelines (see excerpt in box, p. 123) were issued in response to a report earlier this year of a patient in a Japanese hospital who was diagnosed with an infection caused by a Staphylococcus aureus isolate with low-level resistance to vancomycin.2

Since the guidelines’ release, two more cases have been found within a one-month period. In one case, the first vancomycin intermediate-resistant S. aureus (VISA) isolate in the United States was reported in Michigan. The patient had been treated for six months with multiple courses of vancomycin for repeated episodes of vancomycin-susceptible methicillin-resistant S. aureus (MRSA)-associated peritonitis.3

In the second case, a VISA-associated bloodstream infection was diagnosed in a New Jersey resident with long-term MRSA colonization and repeated MRSA infections over six months. In addition, the patient had vancomycin-resistant enterococcal colonization during that time. For most of that period, the patient was treated with multiple courses of vancomycin for repeated MRSA bloodstream infections. Last August, a blood culture from the patient grew an MRSA strain with intermediate resistance to vancomycin.3

No HCW transmissions found so far

CDC investigations are still under way but so far have revealed no cases of transmission to HCWs, says William Jarvis, MD, acting director of the CDC’s hospital infections program.

"Luckily, there is no evidence so far of any transmission to health care workers, which is probably a testimony to the fact that there has been good adherence to infection control practices in these episodes, primarily because the patients were known to have been colonized with MRSA," Jarvis tells Hospital Employee Health.

CDC officials are concerned that the emergence of VISA in the United States suggests that S. aureus strains with full resistance to vancomycin might eventually emerge. For that reason, Jarvis says the agency is calling for hospitals and health care providers to take the following three-pronged preventive approach:

Enhance laboratory capacity at the hospital and state levels to recognize these strains. Use a quantitative method (broth dilution, agar dilution, or agar gradient diffusion) to identify strains.

Use antimicrobials prudently. Ensure appropriate use of vancomycin, including the review of antibiograms for alternative antibiotics.

Fully implement recommended infection control measures to prevent transmission of these strains. Educate HCWs about the epidemiologic implications of emergence of such strains and the appropriate infection control precautions necessary to prevent their spread; strictly adhere to and monitor compliance with contact-isolation precautions and other recommended infection control practices; and conduct surveillance to monitor for the emergence of resistant strains.1,4

Disk diffusion technique is insufficient

Ensuring that microbiology personnel know what tests should be done to detect strains is the first line of defense, says Jarvis, who estimates that about 30% of laboratories are using the "Kirby Bauer" or disk diffusion technique, which does not identify these organisms.

The second line of defense is to establish effective communication between microbiology labs and infection control personnel in hospitals, "so if one of these patients is identified, it’s reported quickly to the clinician in infection control and the patient is placed in appropriate precautions," Jarvis explains.

Third, make sure HCWs know the appropriate precautions. "The most important is washing hands before and after entering the room, possibly the use of gloves if they’re going to have contact with the patient, and the use of gowns and even a mask if they’re going to have close contact with the patient," he says.

Because only two U.S. cases have been identified, most employee health practitioners have not had to deal with occupational exposures to patients with vancomycin-resistant staph infections, but some are becoming concerned due to the reported cases.

"We haven’t had this come up, but it certainly is a concern and a very serious issue," says Charlene Gliniecki, RN, MS, COHN-S, director of employee health and safety at Camino Healthcare in Mountainview, CA. "The infection control practitioner would be the first person to become involved, but when it involves staff — if a staff member has become infected or might not be following infection control practices — that’s when employee health and infection control practitioners would get together."

CDC recommends baseline cultures

Jarvis points out that beyond standard infection control precautions, the CDC recommends that if a resistant case is identified, baseline cultures for staphylococci with reduced susceptibility to vancomycin should be obtained from the anterior nares and hands of all HCWs with patient contact.

"Culture your health care workers before they have contact with that patient so you at least have some baseline data that they were not colonized, and then culture them after they have concluded contact with the patient," he states. "We need to make sure that our health care workers don’t become colonized with these organisms and spread them either to other patients or family members. We take these episodes very, very seriously."

Similar to other staphylococci, the most likely mode of transmission is on the hands of health care workers.

"The patients that have been infected so far have had a bloodstream infection, which probably is not particularly communicable, and a peritoneal infection, which again is not particularly communicable. But if you had a patient with either a decubitus ulcer or a surgical wound infection or pneumonia, the former would be much more likely to be transmitted on the hands of health care workers, and the latter might even be transferred short distances through respiratory secretions," Jarvis notes.

He adds that antimicrobial pressure can add to the likelihood of emergence of resistant strains. "If more and more vancomycin is used, it increases the likelihood that a strain like this will evolve. People have been using it as a preferred choice, instead of as a last resort, for treatment of methicillin-resistant Staph aureus infections. But as demonstrated by the New Jersey, Michigan, and Japanese episodes, in all of these instances, the Staph aureus isolate was resistant to methicillin and intermediately resistant to vancomycin, but was actually sensitive to two or three or even four other available agents."

CDC officials hope that additional cases will be prevented if microbiology labs are enhanced, infection control recommendations are implemented, and physicians use antimicrobials more prudently, Jarvis says.

"We’re hoping that other cases will be forestalled until new [antimicrobial] agents will have been developed and approved by FDA," he says.

Already, drug manufacturer Rhone-Poulenc Rorer has filed for U.S. Food and Drug Administration approval for the first of a new kind of antibiotic designed to battle emerging resistant bacteria. Synercid, the first injectable streptogramin (a distinct class of antibiotics), is made up of two molecules that combine to stop bacteria from making essential proteins. No new class of antibiotics has been developed for 20 years. Rhone is asking the FDA to license Synercid for use against pneumonia, bacteremia, and skin infections. Company spokesman Jean-Jacques Bienaime says the FDA urged Rhone to move quickly on developing the drug, indicating it would give "fast-track" review to Rhone’s application.

Meanwhile, the CDC urges health care providers who isolate S. aureus with confirmed or "presumptive" reduced vancomycin susceptibility to report immediately through state and local health departments to CDC’s investigation and prevention branch, hospital infections program, National Center for Infectious Diseases, Mailstop E-69, 1600 Clifton Road NE, Atlanta, GA 30333; telephone: (404) 639-6413.

"We want to alert everybody out there to look for these organisms, and we want to be notified if they find them," Jarvis says.

References

1. 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, 635-636.

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

3. Centers for Disease Control and Prevention. Update: Staphylococcus aureus with reduced susceptibility to vancomycin —United States, 1997. MMWR 1997; 46:813-815.

4. Centers for Disease Control and Prevention. Recommendations for preventing the spread of vancomycin resistance: Recommendations of the Hospital Infection Control Practices Advisory Committee (HICPAC). MMWR 1995; 44(No. RR-12).