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Vancomycin Resistance Emerging In Epidemic CA-MRSA Strain

First VISA case reported in USA300 clone

In an ominous finding, an epidemic strain of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has developed intermediate resistance to vancomycin, the classic antibiotic weapon against staph infections, Hospital Infection Control has learned.

The finding is significant, because the strain in question is USA300, the hardy and easily transmitted predominant U.S. strain that has been detected in some 40 states. Though other drug options remain available, the appearance of vancomycin resistance in staph strains has long been one of the dreaded warning signs of a “post-antibiotic” era. Emerging resistance in a CA-MRSA strain that is causing serious infections in the community and has been displacing traditional nosocomial strains in some hospitals is particularly troubling.

“That’s one of the infectious disease doctor’s nightmares,” reacted William Schaffner, MD, chairman of the department of preventive medicine at Vanderbilt University School of Medicine in Nashville. “It’s [concerning] to have vancomycin resistance — whether it be intermediate or complete — in any staphylococcal strain, but to have it occur in a community-associated strain that has a great capacity to spread is very, very disturbing. I hope they have that patient in a bubble.”

The details of the case were not available pending publication of the research, but the finding was mentioned by one of the investigators recently in San Francisco at the Interscience Conference on Antimicrobial Agents and Chemotherapy. In response to questions by HIC, Francoise Perdreau-Remington, PhD, a leading MRSA researcher at the University of California in San Francisco and San Francisco General Hospital confirmed that vancomycin-intermediate S. aureus (VISA) had been detected in an isolate of the predominant community strain of CA-MRSA in the United States.

“The mechanism of resistance is a thickening of the cell wall,” she says. “The VISA strains that have been [previously] described were nosocomial strains that originated in the hospital. What we described is a USA300 developing intermediate vancomycin resistance after a six week treatment with vancomycin.”

While the emergence of intermediate resistance is concerning, Perdreau-Remington cited a potentially bigger problem: The USA300 clone appears to have the necessary plasmids to be receptive to a genetic transfer of full-blown vancomycin resistance from vancomycin-resistant enterococci. (For more on this important development see the November 2006 issue of HIC.)

— Gary Evans, editor

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International Infection Prevention Week

It’s in your hands!

Thousands of infection control professionals throughout the world are participating in activities to commemorate International Infection Prevention Week (IIPW).

The annual event, initiated by former President Ronald Reagan in 1986, is spearheaded by the Association for Professionals in Infection Control and Epidemiology (APIC), the nation’s largest infection prevention organization comprised of 11,000 members worldwide and headquartered in Washington, DC.

“Infection prevention and control professionals throughout the world work diligently year-round, striving to prevent deadly infections within their health care institutions and as educators within their communities,” said APIC CEO Kathy Warye. “While we acknowledge their work every day, this is our opportunity to recognize them and their service within the communities in a special way during this week. They, along with their colleagues, work to save lives daily.”

Infection Prevention — It’s In Your Hands!, this year’s theme, will be highlighted at the National Press Club on Oct. 19 in Washington, DC. Infection prevention and control professionals, congressional staff, dignitaries and media from throughout the country are expected to attend the event. One of the presenters will be Raymond T. Wagner, III, of St. Louis. Wagner, now a senior at St. Louis High School, suffered a broken arm in a sledding accident on Christmas Eve 2002, which eventually developed into a hospital-associated infection necessitating numerous surgeries and causing physical impairment. His compelling story has served as an example of the devastation health care-associated infections can cause.

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Public Apathy, Fear Undermine Flu Shots

Less than half of those polled seek shots

Despite widespread publicity about potential pandemic influenza, a good portion of the public in the United States looks on the seasonal flu vaccine with misguided fear or outright apathy. Less than half of respondents (48%) in a recent survey by the National Foundation for Infectious Diseases said they plan to be immunized against influenza this year.

“Unfortunately, public opinion is still split about the safety and effectiveness of influenza immunization,” Susan J. Rehm, MD, medical director of the Washington, DC-based organization, said a recent press conference announcing the findings. ”About half of the survey participants incorrectly believe that the vaccine can cause influenza. Others feel the vaccine is not worthwhile, since it protects only against certain strains of the virus each year.”

Reasons cited for declining vaccination included:

• 43% do not think influenza is serious enough to warrant vaccination.
• 38% feel they are not at risk for influenza and its related complications.
• 37% are not concerned about getting influenza.
• 26% are not concerned about spreading the influenza virus to a friend, family member or co-worker.
• 23% believe that they still got influenza even after being immunized one year.
• 19% worry that the vaccine is not effective.
• 15% think that since they have been vaccinated before, they do not need to receive the vaccine again this season.

Though annual vaccination is the safest and most effective way of preventing influenza infection, 30% think annual influenza immunization is not worth receiving, because the vaccine only protects against three strains of the virus, she said. The influenza viruses change every year, which is why a new vaccine is produced in time for each season, she explained to the media, hoping they would get the message out to the public. The global surveillance and production system ensures that the strains predicted to be most predominant are included in the vaccine, Rehm emphasized.

More than half of those who plan to be immunized this season (53%) acknowledged learning about the value of immunization the hard way. They now make annual vaccination a priority after suffering from influenza and its severe symptoms during a previous season.

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