The bacteria that cause staph infections seem to prefer chomping on human blood than on the blood of other animals.
A new study finds that tiny differences in hemoglobin molecules may allow Staphylococcus aureus to thrive better in some bloodstreams than in others, and human hemoglobin is slightly different from hemoglobin in other animals, study researcher Eric Skaar of Vanderbilt University said. Hemoglobin is the oxygen-carrying protein in red blood cells that contains iron.
There are even differences in hemoglobin molecules from person to person, which could explain why some people have a high susceptibility to staph infections, added Skaar, an associate professor of microbiology and immunology.
“Staph lives in about 30 percent of people's noses without making them sick, yet some people get terrible staph infections,” Skaar told MyHealthNewsDaily. That means “staph may preferentially infect some people versus others.”
Staph is one of the main causes of pus-forming infections of skin and soft tissue and of infectious heart disease. It's also common in hospital-acquired infections, and is one of the leading causes of food poisoning, Skaar said. Antibiotic-resistant strains of staph such as MRSA (methicillin-resistant Staphylococcus aureus) are also a problem in hospitals.
For their study, Skaar and his colleagues infected two groups of mice with the bacteria. One group had been engineered to produce human hemoglobin, and the other group had regular, mouse hemoglobin.
The researchers found 10 times more bacteria in the bodies of the mice with human hemoglobin than in the other mice.
Staph gets iron from blood by popping open red blood cells and binding to the hemoglobin. Skaar found that a binding protein produced by staph, called IsdB, prefers to bind to human hemoglobin than to the hemoglobin of mice, horses, cows and pigs.
Other bacteria, such as the ones that cause diphtheria, also prefer human hemoglobin to animal hemoglobin, Skaar said. But still others, such as Bacillus anthracis, which causes anthrax, don't have a preference.
Skaar hopes to use these findings to come up with a preventive therapy for people at high risk for staph infections.
“A lot of times, people get infections from surgery,” he said. More research might allow doctors “to see if the person has a hemoglobin sequence that staph tends to favor, so we would treat him with prophylactic antibiotics [as a] sort of a preventive measure.”
Skaar is now examining the DNA of people who had staph infections, to look for similarities in the genes that determine their hemoglobin.
Pass it on: Differences in people's hemoglobin may explain why some are more susceptible to Staph infections than others.
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