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Bacteria Eyed for Possible Role in Atherosclerosis

Enterobacter Bacteria - Normally Associated with Pneumonia and Sepsis - Found in Atherosclerotic Plaque Tissue

(HealthNewsDigest.com) - NEW YORK (Jan. 5, 2011) - Dr. Emil Kozarov and a team of researchers at the Columbia University has identified specific bacteria that may have a key role in vascular pathogenesis, specifically atherosclerosis - the number one cause of death in the United States.

Presence of bacteria in the blood circulation can lead to inflammation and narrowing of the vessels, known as atherosclerosis, and to formation of blood clots that lead to myocardial infarction and stroke.

Fully understanding the role of infections in cardiovascular diseases has been challenging because researchers have previously been unable to isolate live bacteria from atherosclerotic tissue. Using tissue specimens from the Department of Surgery and the Herbert Irving Comprehensive Cancer Center at Columbia University, Dr. Kozarov and his team, however, were able to isolate bacteria from a 78-year-old male who had previously suffered a heart attack. Their findings are explained in the latest Journal of Atherosclerosis and Thrombosis.

In the paper, researchers describe processing the tissue using cell cultures and genomic analysis to look for the presence of culturable bacteria. In addition, they looked at five pairs of diseased and healthy arterial tissue. The use of cell cultures aided in the isolation of the bacillus Enterobacter from the patient's tissue. Implicated in bloodstream infections and other life-threatening conditions, the isolated bacteria were resistant to multiple antibiotics. Surprisingly, using quantitative methods, this microbe was further identified in very high numbers in diseased but not in healthy arterial tissues.

The data suggest that a chronic infection may underlie the process of atherosclerosis, an infection that can be initiated by the systemic dissemination of bacteria though different "gates" in the vascular wall - as in the case of a septic patient, through intestinal infection. The data support Dr. Kozarov's previous studies, where his team identified periodontal bacteria in carotid artery, thus pointing to tissue destructing periodontal infections as one possible gate to the circulation. Bacteria can gain access to the circulation through different avenues, and then penetrate the vascular walls where they can create secondary infections that have been shown to lead to atherosclerotic plaque formation, the researchers continued. "In order to test the idea that bacteria are involved in vascular pathogenesis, we must be able not only to detect bacterial DNA, but first of all to isolate the bacterial strains from the vascular wall from the patient," Dr. Kozarov said.

One specific avenue of infection the researchers studied involved bacteria getting access to the circulatory system via internalization in white blood cells (phagocytes) designed to ingest harmful foreign particles. The model that Dr. Kozarov's team was able to demonstrate showed an intermediate step where Enterobacter hormaechei is internalized by the phagocytic cells, but a step wherein bacteria are able to avoid immediate death in phagocytes. Once in circulation, Dr. Kozarov said, bacteria using this "Trojan horse" approach can persist in the organism for extended periods of time while traveling to and colonizing distant sites. This can lead to multitude of problems for the patients and for the clinicians: failure of antibiotic treatment, vascular tissue colonization and initiation of an inflammatory process, or atherosclerosis, which ultimately can lead to heart attack or stroke.

"Our findings warrant further studies of bacterial infections as a contributing factor to cardiovascular disease, and of the concept that 'bacterial persistence' in phagocytic cells likely contributes to systemic dissemination," said Dr. Kozarov, an associate professor of oral biology at the College of Dental Medicine. Dr. Jingyue Ju, co-author and director of the Columbia Center for Genome Technology & Biomolecular Engineering, also contributed to this research, which was supported in part by a grant from the National Heart, Lung, and Blood Institute of the National Institutes of Health and by the Columbia University Section of Oral and Diagnostic Sciences.

The article appeared in Volume 18 of the Journal of Atherosclerosis and Thrombosis.

Could simple antimicrobials be the long-awaited cure for heart attack and stroke?

Study Finds Viable Bacteria in Atherosclerotic Plaque Tissue

NEW YORK (July 1, 2011) - The same plaque that is clogging the arteries of people with atherosclerosis and other forms of cardiovascular disease may have a direct link to pathogenic bacteria dwelling in the mouth, a new study by Dr. Emil Kozarov has found.

Furthering his pioneering research into whether bacteria play a direct role in atherosclerosis, Dr. Emil Kozarov and an interdisciplinary team of scientists at Columbia University Medical Center set out to culture and identify several bacterial species from the atherosclerotic tissue of aseptic patients undergoing surgery for arterial obstruction.

Some of the bacteria, the researchers found, could be traced back to species that typically originate in the mouth - such as the bacterium Porphyromonas gingivalis, the precursor and main culprit in periodontitis. Unlike in the mouth, however, these bacteria in the arteries keep low profile, causing low grade inflammation until something happens in the tissue - a triggering mechanism that is not completely understood yet.

According to his latest findings, now published online in the Journal of Internal Medicine, atherosclerotic tissue samples taken from otherwise healthy individuals reveal a flora of bacteria heretofore unassociated with atherosclerotic lesions. Some of these bacteria are highly responsive to antibiotics and so the thinking is that relatively common anti-microbials (such as doxycycline, or vancomycin) can be enlisted to fight the development of plaque in arterial tissue, Dr. Kozarov said.

Dr. Kozarov and his team recovered a limited number of bacterial species from tissues from the seven patients studied. Using biochemical analyses, DNA sequencing and databases, they identified the species as Propionibacterium acnes, Staphylococcus epidermidis, Streptococcus infantis and Porphyromonas gingivalis. The presence of P. gingivalis in tissue was confirmed using quantitative DNA analysis and double immunofluorescence imaging. The recovered bacteria are known to induce blood clotting. The presence of these bacteria suggests they may play a key role in vascular pathogenesis, specifically atherosclerosis, or what is commonly referred to as "clogging of the arteries."

Atherosclerosis is a chronic inflammatory condition associated with hypertension, hyperlipidemia, diabetes and smoking. "Although it has been shown that these conventional risk factors are prevalent among individuals with cardiovascular disease, the incidence of atherosclerosis is not fully explained by them," Dr. Kozarov said. "The mechanisms involved in atherogenesis resemble protection from microbial assault. A mountain of epidemiological data suggests that chronic infectious diseases, such as periodontitis, may be a strong contributing factor in the development of atherosclerotic plaques."

In the study, researchers demonstrated the presence of thousands of P. gingivalis genomes per gram of diseased arterial tissue. Further, genomic analysis of diseased tissue and matching healthy tissue from the same individual identified a higher presence of bacteria in the diseased tissue. The data suggest that underlying the process of atherosclerosis is a chronic infection which can be initiated by the systemic dissemination of bacteria though different "gates" such inflamed gums. The data also support Dr. Kozarov's previous studies, in which his team identified periodontal bacteria in carotid arteries, thus pointing to tissue-destroying periodontal infections as one possible entry to the body's circulatory system.

"So far we have had bacterial 'fingerprints' at the crime scene. Now we are searching for the 'smoking gun,'" Dr. Kozarov said. "The next step now is to study a larger number of samples and gather evidence in order to assess just how much of a role bacteria play, and which are the prevalent species at the diseased vascular sites. This will open the possibility of using antibiotics for treatment of atherosclerosis."

The paper's other authors include Brian Rafferty and Daniel Jönsson, Mitchell S.V. Elkind and Roman Nowygrod of the Columbia University College of Physicians and Surgeons, Ryan Demmer from the Mailman School of Public Health, and Sergey Kalachikov from the Columbia Genome Center.

The article appeared in the Journal of Internal Medicine.

Bacterial Infection Spreading In Vascular Cells Has a Possible Role in Atherosclerosis

In their paper published in February 2008, a team of researchers including Dr. Emil Kozarov demonstrated the ability of infectious agents to reside in tissues from large vessels, isolated from patients. The micrograph represents the infectious agent (red dots) residing in vascular endothelial cells (Li L. et al, BMC Microbiology, 2008, 8:26). Such microorganisms have been shown to destabilize and disrupt tissues, therefore they may be the culprit for triggering heart attack and stroke.

Press Releases:

http://news.columbia.edu/research/2269

http://www.news-medical.net/news/20110106/Columbia-research-team-identifies-bacteria-may-play-a-key-role-in-atherosclerosis.aspx

http://www.health.am/vein/more/bacteria-eyed-for-possible-role-in-atherosclerosis/

http://www.sciencedaily.com/releases/2011/01/110105131753.htm

NEW PROJECTS: Disease Risk Determination

A team of investigators, including Dr. Kozarov as Principal Investigator, obtained an award from the National Institutes of Health to explore the genetic background of the infectious agents discovered to reside in atherosclerotic plaques. The investigations involve testing of patient specimens from diseased and from healthy sites to identify unique disease-associated virulence factors (“disease genotype”). This investigation will enable us to design diagnostic tools for risk assessment and therapies. This approach will also likely identify moieties involved in cross talk between invasive clinical strains and the vascular tissue.

Human Tissue Invasion-Associated Factors

A team of investigators, including Dr. Kozarov as Principal Investigator, obtained an award from the National Institutes of Health to identify unique invasion-associated virulence factors in the genetic background of the infectious agents discovered to reside in atherosclerotic plaques. Identification of the virulence mechanisms and genetic heterogeneity of these agents will likely identify moieties involved in cross talk between invasive bacteria and the human tissue. Such information will facilitate the development of novel defined molecular approaches for the disease treatment.