Newly Discovered Oral Bacterium Could Result in Heart Disease, Meningitis

[drsushant]

Newly Discovered Oral Bacterium Could Result in Heart Disease, Meningitis

A recently identified type of bacterium could have devastating effects.

The bacterium, which inhabits the oral cavity, could result in major health problems, according to the International Journal of Systemic and Evolutionary Microbiology. The discovery will enable scientists to figure out the way it works and the risks it poses.

This type of bacterium was pinpointed by a research team at the Institute of Medical Microbiology of the University of Zurich. The bacterium, Streptococcus tigurinus, was separated from the blood of patients who had endocarditis, meningitis and spondylodiscitis. This bacterium is similar to others that inhabit the mouth.

This bacteria has been around for a while but had never been identified until recently. This step is crucial, according to study leader Dr. Andrea Zbinden, because now it can be treated properly.

This particular bacterium tends to cause major diseases. But dentists and doctors should soon be able to recommend the proper treatment orally and for overall health. Researchers next need to determine how common this bacterium is and how many people need to be treated.

More research is necessary to determine the specific risk factors for S. tigurinus.

        

[Drsumitra]

 Bifidobacteria, largely known as long-term beneficial gut bacteria, are often included as probiotic components of food to aid digestion and boost the immune system. However, not all species within the genus Bifidobacterium provide beneficial effects to the host’s health. In fact, the Bifidobacterium dentium species is an opportunistic pathogen since it has been linked to the development of tooth decay. The genome sequence of B. dentium Bd1 reveals how this microorganism has adapted to the oral environment through specialized nutrient acquisition features, acid tolerance, defences against antimicrobial substances and other gene products that increase fitness and competitiveness within the oral niche.
This report identifies, through various genomic approaches, specific adaptations of a Bifidobacterium taxon to a lifestyle as a tooth decay-causing bacterium. The data in this study indicate that the genome of this opportunistic pathogen has evolved through only a small number of horizontal gene acquisition events, highlighting the narrow boundary that separates bacteria that are long-term residents on or in the human body from opportunistic pathogens.

        

[drmithila]

Good dental hygiene and health may be crucial in preventing heart valve infection, according to research reported in Circulation: Journal of the American Heart Association.
In a study of 290 dental patients, researchers investigated several measures of bacteremia (bacteria released into the bloodstream) during three different dental activities — tooth brushing, a single tooth extraction with a preventive antibiotic and a single tooth extraction with a placebo.
As expected, researchers found bacteria in the blood more often with the two extraction groups than with the brushing group. However, the incidence of bacteremia from brushing was closer to an extraction than expected. "This suggests that bacteria get into the bloodstream hundreds of times a year, not only from tooth brushing, but also from other routine daily activities like chewing food," said the study’s lead author Peter Lockhart, D.D.S.
In 2007, the American Heart Association modified its recommendation that preventive antibiotics be used prior to most dental procedures for the great majority of those at risk for infective endocarditis (IE) — a rare but life-threatening infection of the lining of the heart or heart valve that can occur when bacteria enter the bloodstream. The association now recommends preventive antibiotics only for patients at the highest risk for a bad outcome from IE.
In this double-blind, placebo-controlled study, researchers sought to determine if daily dental activities like tooth brushing posed as much risk for IE as major dental procedures (e.g., tooth extractions) for which preventive antibiotics might be prescribed. Researchers drew blood from each patient a total of six times — before, during and after these interventions — and analyzed the samples for bacterial species that are associated with IE.
They found that bacteria enter the bloodstream in most patients early on during a dental extraction or tooth brushing, and that bacteria can still be found in the blood as long as an hour after these procedures in a small number of cases.
"While the likelihood of bacteremia is lower with brushing, these routine daily activities likely pose a greater risk for IE simply due to frequency: that is, bacteremia from brushing twice a day for 365 days a year versus once or twice a year for dental office visits involving teeth cleaning, or fillings and other procedures," said Lockhart, chair of the Department of Oral Medicine at the Carolinas Medical Center, Charlotte, N.C.
"For people who are not at risk for infections such as IE, the short-term bacteremia is nothing to worry about," he said.
"If you stop oral hygiene measures, the amount of disease in your mouth goes up considerably and progressively and you’ll have far worse oral disease," Lockhart said. "It’s the gingival (gum) disease and dental caries (decay), that lead to chronic and acute infections such as abscesses. It’s that sort of thing that puts you at risk for frequent bacteremia and presumably endocarditis if you have a heart or other medical condition that puts you at risk."
"The incidence of IE-related bacteremia from all blood draws was 23 percent in the tooth-brushing group, 33 percent in the extraction plus antibiotic group, and 60 percent for the extraction-placebo group," Lockhart said. The researchers therefore found that amoxicillin significantly decreased the incidence of bacteremia from an extraction but did not eliminate it altogether.
The highest incidence of positive IE-related bacterial cultures occurred within five minutes of all three procedures, with the majority (93 percent) of patients with bacteria in the blood experiencing the condition for less than 20 minutes after the procedures. Only 5 percent of the extraction-placebo group and 2 percent of the brushing group still had bacteria in the blood at one hour.
"The human mouth is colonized by a larger variety of bacteria than any other body area, and many of the bacterial species in the mouth that cause disease are found in the periodontal pocket (below the gum line) adjacent to the teeth," said Lockhart, adding that some of those species have been associated with IE. "Bacteria commonly gain entrance to the circulation through ulcerated gingival (gum) tissue surrounding the teeth, but oral hygiene reduces gingival disease and reduces that risk."
Patients in this study came to an urgent care clinic in need of tooth extractions. So it’s likely they had a higher level of dental disease and poorer oral hygiene than the general population.
The researchers are analyzing additional data from this study to determine if there is a direct correlation between the level of dental disease and the likelihood of IE bacteria getting into the bloodstream.
According to the American Heart Association, those at highest risk for adverse outcomes from IE are 1) patients with a prosthetic cardiac valve or prosthetic material used for cardiac valve repair; 2) previous endocarditis; 3) cardiac transplantation recipients who develop cardiac valve abnormalities; and 4) congenital heart disease for unrepaired cyanotic congenital heart disease, including palliative shunts and conduits; completely repaired congenital heart defect with prosthetic material or device, during the first six months after the procedure; or repaired congenital heart disease with persisting leaks or abnormal flow at the site or adjacent to the site of a prosthetic patch or prosthetic device.

 

        

[drmithila]

 Howard Jenkinson, Ph.D., a professor of oral microbiology at Bristol’s School of Oral and Dental Sciences, explained how oral bacteria can wreak havoc if they are not kept in check by regular brushing and flossing during a presentation at the Society for General Microbiology’s fall meeting in Nottingham, U.K., on September 6.

"Poor dental hygiene can lead to bleeding gums, providing bacteria with an escape route into the bloodstream, where they can initiate blood clots leading to heart disease," Jenkinson said.

The University of Bristol researchers, in collaboration with scientists at the Royal College of Surgeons in Ireland, have shown that once let loose in the bloodstream, streptococcus bacteria can use a protein on their surface, called PadA, as a weapon to force platelets in the blood to bind together and form clots.

"We are currently investigating how the platelet-activating function of PadA can be blocked," Jenkinson said. "This could eventually lead to new treatments for cardiovascular disease, which is the biggest killer in the developed world."

Jenkinson said the bacteria completely encase themselves in a clump of platelets, enabling them to avoid detection by the host immune system and to hide from antibiotics, his study found.

"Unfortunately, as well as helping out the bacteria, platelet clumping can cause small blood clots, growths on the heart valves (endocarditis), or inflammation of blood vessels that can block the blood supply to the heart and brain," he said.

        

[drmithila]

The bacterium was identified by researchers at the Institute of Medical Microbiology of the University of Zurich and has been named Streptococcus tigurinus after the region of Zurich where it was first recognised. S. tigurinus was isolated from blood of patients suffering from endocarditis, meningitis and spondylodiscitis (inflammation of the spine). It bears a close resemblance to other Streptococcus strains that colonise the mouth. Bleeding gums represent a possible route of entry for oral bacteria into the bloodstream.
The similarity of S. tigurinus to other related bacteria has meant that it has existed up until now without being identified. Its recent identification is clinically important, explained Dr Andrea Zbinden who led the study. "Accurate identification of this bacterium is essential to be able to track its spread. Further research must now be done to understand the strategies S. tigurinus uses to successfully cause disease. This will allow infected patients to be treated quickly and with the right drug."
Dr Zbinden said that while the discovery of the bacterium is no cause for alarm, it is important that it is recognised and the risk is quantified. "This bacterium seems to have a natural potential to cause severe disease and so it’s important that clinicians and microbiologists are aware of it," she said. "The next step is to work out exactly how common this bacterium is in the oral cavity and what risk it poses. Immunosuppression, abnormal heart valves, dental surgeries or chronic diseases are common predisposing factors for blood infections by this group of bacteria. However, the specific risk factors for S. tigurinus remain to be determined."

 

        

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