Mechanism of Bacterial Endocarditis Discovered



Infection by Streptococcus mutans is a leading cause of bacterial endocarditis. Scientists have identified the protein that allows S mutans to invade heart tissue, as reported in the June issue of Infection and Immunity by microbiologists at the University of Rochester Medical Center. The work raises the possibility of creating a screening tool—perhaps a cheek swab or a saliva test—to gauge a dental patient’s vulnerability to the condition.
Jacqueline Abranches, PhD, a microbiologist and the corresponding author of the study, and her team at the University’s Center for Oral Biology discovered that a collagen-binding protein known as CNM gives S mutans its ability to invade heart tissue. In laboratory experiments, scientists found that strains with CNM are able to invade heart cells, and strains without CNM are not. When the team removed the gene for CNM in strains where it’s normally present, the bacteria were unable to invade heart tissue. With­out CNM, the bacteria simply could not gain a foothold; their ability to adhere was about one tenth of what it was with CNM. The work may someday enable doctors to prevent S mutans from invading heart tissue. Even sooner, since some strains of S mutans have CNM and others do not, the research may enable doctors to gauge a patient’s vulnerability to a heart infection caused by the bacteria. Dr. Abranches has identified 5 specific strains of S mutans that carry the CNM protein, out of more than 3 dozen strains examined. CNM is not found in the most common type of S mutans found in people, type C, but is present in rarer types of S mutans, including types E and F.
“It may be that CNM can serve as a biomarker of the most virulent strains of S mutans,” said Abranches.” When patients with cardiac problems go to the dentist, perhaps those patients will be screened to see if they carry the protein. If they do, the dentist might treat them more aggressively with preventive antibiotics, for example.”

(Source: ScienceDaily; University of Rochester Medical Center, June 27, 2011)