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GEN News Highlights : Sep 25, 2009

C. Difficile Hypervirulence Genes Pinpointed

Research appearing in Genome Biology found five genes in the current epidemic strain that have developed in the last 20 years.

A group of researchers have identified five genetic regions that are unique to the most virulent C. difficile strains. The study, which is detailed in Genome Biology, was looking for genes relating to motility, antibiotic resistance, and toxicity.

Brendan Wren, Ph.D., from the London School of Hygiene & Tropical Medicine worked with a team at The Wellcome Trust Sanger Institute to compare the genomes of three strains of the bacterium: the hypervirulent 027 strain, a historic, nonepidemic 027 strain, and one less related and also nonepidemic 630 strain.

“In the past five years a new group of highly virulent C. difficile strains has emerged to cause outbreaks of increased severity in North America and Europe,” notes Dr. Wren. “Several studies have shown that patients infected with these 027 strains have more severe diarrhea, higher mortality, and more recurrences. This study provides genetic markers for the identification of 027 strains and offers a unique opportunity to explain their emergence.”

The researchers found that the 027 strains had considerable genetic differences compared to the nonepidemic 630 strain. They believe this may relate to the observed phenotypic difference in virulence. Additionally, five genetic regions appear to have accumulated over the last 20 years in the modern-day epidemic 027 strain compared to its historic counterpart.

“The observed gene differences between these strains might individually or collectively explain why modern 027 strains are more likely to be epidemic and could explain the higher case-fatality ratio and persistence associated with infection by these strains,” Dr. Wren reports.