December 3, 2005
New Intestinal Bug Emerging in North America
NEW YORK -- Two reports highlight the emergence of a new, highly toxic strain of the bacterium Clostridium difficile that is resistant to fluoroquinolone antibiotics, such as Cipro (ciprofloxacin) and Levaquin (levofloxacin), and is causing geographically dispersed outbreaks.
The reports were released early by The New England Journal of Medicine to coincide with this week's report by the Centers for Disease Control and Prevention C. difficile infections in low-risk patients.
C. difficile is a microbe that can be a member of the normal bacterial colonies that live in the intestines. Problems occur, however, when neighboring bacteria are disturbed allowing an overgrowth of C. difficile, which typically results in a foul-smelling watery diarrhea. Overuse of certain antibiotics is one common cause of such disturbances.
The CDC has received an increased number of reports from health care facilities of cases of severe C. difficile-associated disease, according to one of the papers. Dr. L. Clifford McDonald, from the CDC in Atlanta, and colleagues say this suggests the emergence of an epidemic strain with increased virulence, antibiotic resistance, or both.
To test this hypothesis, the research team collected 187 C. difficile samples from outbreaks since 2001 in eight health care facilities in six states, and compared their characteristics with those of 6000 samples obtained between 1984 and 1990.
More than half of the recent samples were of one strain, termed BI/NAP1. Testing showed that this strain was particularly resistant to fluoroquinolone antibiotics.
By contrast, just 14 of the 6000 isolates obtained in the past were of this strain, the report indicates.
"If this epidemic strain continues to spread and to contribute to increased (disease and death), it will be important either to reconsider the use of fluoroquinolones or to develop other innovative measures for controlling C. difficile-associated disease," McDonald's group writes.
They stress the need for strict infection-control measures. Because alcohol does not kill C. difficile spores, they recommend that health care workers wash their hands with soap and water instead of using alcohol-based hand sanitizers during outbreaks.
According to a second report, Canadian researchers, led by Dr. Vivian G. Loo from McGill University Health Center in Montreal, identified 1719 episodes of C. difficile-associated diarrhea at 12 Quebec hospitals between January and June of 2004.
From 1997 to 2004, the rate of infections increased from 6 to 22.5 cases per 1000 admissions. Moreover, in 2004, nearly 7 percent of patients with this infection died within 30 days compared with 1.5 percent in 1997.
The predominant strain was similar to that observed by McDonald's group and was resistant to ciprofloxacin, moxifloxacin, gatifloxacin and levofloxacin.
Loo's team conducted a study comparing 237 patients with C. difficile-associated diarrhea with 237 patients outcome this problem. They found that treatment with cephalosporin antibiotics or fluoroquinolones increased the risk of this diarrhea by nearly fourfold each.
In an editorial accompanying the two papers, Drs. John G. Bartlett and Trish M. Perl, from Johns Hopkins University School of Medicine in Baltimore, point out that standard stool tests will not identify this epidemic strain.
They therefore advise that "physicians and infection-control personnel need to monitor for an increasing (rate) of C. difficile-associated disease on the basis of some classic features" in patients who have recently been treated with antibiotics.
SOURCE: The New England Journal of Medicine, December 8, 2005.