updated 1/26/2011 12:21:10 PM ET 2011-01-26T17:21:10

Bacteria called Listeria monocytogenes can cause mild food-poisoning symptoms in healthy individuals, but some strains have an enhanced ability to invade the heart, a new study finds.

The ability to infect the heart, possibly causing serious heart disease, may be due to particular proteins on the surface of these bacteria. If so, these proteins could serve as a way to alert doctors to the threat of heart infections, the researchers said.

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"If we find that these proteins are indeed how the bacteria target heart cells …then they'd almost be like a barcode," said study researcher Nancy Freitag, a professor at the University of Illinois, Chicago. "And so if people come down with an infection, or there's an outbreak and it's due to one of these strains, I think medical personnel could just be aware that there's an increased risk for cardiac infection."

The study was conducted in mice, so further research is needed to determine whether the findings are true for humans.

The study is in the latest issue of the Journal of Medical Microbiology.

Up to 30 percent of listeria cases cause death
Other food-borne pathogens, such as salmonella and E. coli, sicken people more often than the listeria bacterium does, but disease from listeria can be deadlier. Freitag said about 20 to 30 percent of those cases result in death. People who are immunocompromised, such as those who've had an organ transplant, are the most vulnerable to infection.

The bacteria often infect the central nervous system, but in 7 percent to 10 percent of cases, it infects the heart. Researchers didn't know whether certain patients were more susceptible to heart infections, or whether there was something different about certain strains of the bacteria that made them better able to target the heart, Freitag told MyHealthNewsDaily.

Freitag and her colleagues infected mice with several strains of Listeria monocytogenes, some which were taken from contaminated food, others from laboratory stocks, and one obtained from a patient.

Two strains in particular appeared to be attracted to the heart. Mice infected with these strains were more likely to have heart infections, and had 10-fold to 15-fold more bacteria in their hearts than animals infected with other strains.

Proteins on the surface on the heart-targeting strains were slightly different from the surface proteins of other strains, the researchers said, which may have increased these strains' ability to invade heart cells. However, more research would be needed to confirm this, they said.

Figuring out a way to identify the heart-targeting bacteria would be particularly useful for patients thought to be particularly prone to developing Listeria monocytogenes cardiac infections, such as patients with heart valve replacements, Freitag said.

Follow MyHealthNewsDaily staff writer Rachael Rettner on Twitter @Rachael_MHND.


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