Researchers find a way to detect stealthy, 'hypervirulent' Salmonella strains

Apr 12, 2012
Salmonella typhimurium (red) invades cultured human cells in this color-enhanced scanning electron micrograph. Credit: Rocky Mountain Laboratories, NIAID, NIH

A recent discovery of "hypervirulent" Salmonella bacteria has given UC Santa Barbara researchers Michael Mahan and Douglas Heithoff a means to potentially prevent food poisoning outbreaks from these particularly powerful strains. Their findings, in a paper titled "Intraspecies Variation in the Emergence of Hyperinfectious Bacterial Strains in Nature," have been published in the journal PLoS Pathogens.

Salmonella is the most common cause of infection, hospitalization, and death due to foodborne illness in the U.S. This burden may continue to worsen due to the emergence of new that would tax current health-control efforts. To address this problem, researchers sought out -- and found -- hypervirulent strains that present a potential risk to and the livestock industry.

An international team of scientists -- which also included Robert Sinsheimer and William Shimp from UCSB; Yi Xie and Bart Weimer from UC Davis; and John House from University of Sydney, Australia –– conducted a global search for hypervirulent Salmonella strains. They were found among isolates derived from livestock, and rendered current vaccines obsolete.

Bacteria behave like a Trojan Horse, exposing their weapons only after initiating infection. "These strains exhibit this behavior in the extreme -- essentially having a '5th gear' they can switch to during infection," said Heithoff, lead author of the paper.

Previous efforts to find hypervirulent strains were unsuccessful since bacteria behave much like their less-virulent cousins after environmental exposure. "The trick was to assess their virulence during infection -- before they switch back to a less-virulent state in the lab," said Professor Mahan.

Now that researchers know what to look for, they are developing methods to rapidly detect and discriminate the more harmful strains from their less-virulent cousins. The strategy is aided by a special medium utilized by the researchers that forces the bacteria to reveal their weapons in the laboratory -- the first step in the design of therapeutics to combat them.

Humans usually get Salmonella from eating contaminated beef, chicken, or eggs. However, animal waste can contaminate fields where fruits, nuts, and vegetables are grown, thus posing a particular health concern for vegetarians. The threat is exacerbated when these foods are not cooked. control efforts are expensive -- recent estimates place this cost up to $14.6 billion annually in the U.S.

As hypervirulent strains pose a potential risk to human and animal health, mitigation efforts warrant researchers' careful attention. "Now that we have identified the problem -- and potential solutions -- we just need to get to work," Heithoff said.

Explore further: Two-armed control of ATR, a master regulator of the DNA damage checkpoint

More information: dx.plos.org/10.1371/journal.ppat.1002647

Related Stories

Salmonella in garden birds responsive to antibiotics

Jun 02, 2008

Scientists at the University of Liverpool have found that Salmonella bacteria found in garden birds are sensitive to antibiotics, suggesting that the infection is unlike the bacteria found in livestock and humans.

The time is ripe for Salmonella

Mar 26, 2012

The ripeness of fruit could determine how food-poisoning bacteria grow on them, according to scientists presenting their work at the Society for General Microbiology's Spring Conference in Dublin this week. ...

Discovery paves way for salmonella vaccine

Feb 13, 2012

(Medical Xpress) -- An international research team led by a University of California, Davis, immunologist has taken an important step toward an effective vaccine against salmonella, a group of increasingly antibiotic-resistant ...

Research traces bacteria in salmonella outbreaks

Aug 31, 2011

(Medical Xpress) -- During such mass food-poisoning outbreaks as the recent contamination of ground turkey, speedy identification of the bacteria involved can save lives and reduce illness. New research co-authored ...

Recommended for you

Devising a way to count proteins as they group

1 hour ago

A new study from Indiana University-Purdue University Indianapolis and University of California Berkeley researchers reports on an innovative theoretical methodology to solve "the counting problem," which is key to understanding ...

Mysteries of 'molecular machines' revealed

2 hours ago

"Inside each cell in our bodies and inside every bacterium and virus are tiny but complex protein molecules that synthesize chemicals, replicate genetic material, turn each other on and off, and transport ...

Bacteria are wishing you a Merry Xmas

8 hours ago

A bacterium has been used to wish people a Merry Xmas. Grown by Dr Munehiro Asally, an Assistant Professor at the University of Warwick, the letters used to spell MERRY XMAS are made of Bacillus subtilis, ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.