Although we are not yet in a “post antibiotic era,” untreatable gram-negative resistant infections are occurring with greater frequency, emphasizing the need for quick action to control these pathogens. Arjun Srinivasan, MD, an epidemiologist with the U.S. Centers for Disease Control and Prevention (CDC), shared this perspective during a symposium outlining the growing problem at the 47^th Annual Meeting of IDSA in Philadelphia.

Data from a recent CDC analysis underscored the threat and showed a continuing increase in resistance among gram-negative strains to antimicrobials in four classes (beta-lactams, quinolones, aminoglycosides, and carbapenems) compared to previous data. At the symposium, Dr. Srinivasan presented parts of this analysis, which was based on data collected through CDC’s National Health Safety Network from more than 400 hospitals in 45 U.S. states from January 2006 to January 2009.

The analysis included four infection types: ventilator-associated pneumonias, central-line associated bloodstream infections, catheter-associated urinary tract infections, and surgical site infections.

Among the findings, 30 percent of Acinetobacter baumannii isolates reported to the network tested resistant to all agents in all four drug classes, an increase from approximately 16 percent of isolates reported in 2004. “We now stand at a place where a third of all the acineobacter isolates causing these health care-associated infections, at least in our data, are resistant to all the frontline therapies,” Dr. Srinivasan said.

A poster presentation described a similar trend involving an older and infrequently used class of antibiotics, polymyxins, that recently more clinicians have come to rely on for treating gram-negative resistant bacteria. The research found a 50 percent increase in resistance to polymyxin B over a two-year period among three gram-negative bacteria species at a New York hospital. In addition, 75 percent of the organisms studied were resistant to at least three classes of antibiotics, while 30 percent were resistant to five or more classes, reported Jason Kessler, MD, clinical fellow in the division of infectious diseases at Columbia University in New York.

In his presentation, Dr. Srinivasan noted that gram-negative resistant infections are not limited to certain parts of the country or specific types of facilities: Four-class resistant acineobacter isolates, for instance, came from 23 different states, while isolates resistant to drugs in three of the classes were reported in 28 states.

The emerging trend of increasing resistance to carbapanem shown by Klebsiella pneumoniae is particularly frightening, Dr. Srinivasan said. In CDC’s analysis, 10 percent of K. pneumoniae isolates, reported from 11 states, showed carbapanem resistance, compared with less than 1 percent of reported klebsiella isolates in 2000. The increase helps demonstrate the epidemiology of KPC-producing organisms, Dr. Srinivasan added, including their ability to disseminate very quickly, within individual hospitals and throughout the country.

The troubling statistics highlight the need for action to address gram-negative resistant pathogens, including broad and aggressive use of infection control measures, Dr. Srinivasan concluded, in addition to raising awareness among the public and policymakers about the growing problem.

Several speakers echoed these concerns at a press conference and highlighted IDSA’s efforts to address the threat of drug-resistance on several fronts, including antimicrobial stewardship, infection control, and stimulating the development of new antimicrobial agents. “Antibiotic development is dying, and we’re running out of drugs,” said Brad Spellberg, MD, FIDSA, a member of IDSA’s Antimicrobial Availability Task Force and an associate professor of medicine at the University of California-Los Angeles. “We have organisms that are already resistant to every antibiotic we can throw at them. It’s already being seen.”

A recent article and accompanying editorial in the Journal of the American Medical Association underscore the growing problem. In an international study, researchers found that infections, including those caused by drug-resistant gram-negative organisms, are common in intensive care units worldwide and associated with increased risk of hospital death.

To address the urgent threat of antimicrobial resistance around the world, IDSA in November called on U.S. and European Union leaders to commit to developing 10 new antibiotics by 2020, known as the 10 X ’20 Initiative (see related IDSA News story). The new initiative follows an agreement by U.S. and European political leaders to establish a transatlantic taskforce to help address the global crisis posed by resistance. For more information about the Society’s efforts to address antimicrobial resistance, see IDSA’s website.

Audio and synchronized speaker slides from sessions at the 2009 IDSA Annual Meeting are available for purchase online.

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