**8.1 Dental biofilms**

Dental biofilms, commonly known as plaque are the most studied biofilm in human. It involves hundreds of species of bacteria. Some significant microbes include *Porphyromonas gingivalis, Bacteroides forsythus*, *Actinobacillus actinomycetemcomitans*, *Treponema denticola*, and a number of *Streptococci* including *Streptococcus mutans* [11].

After a good oral wash or dental cleaning, the tooth enamel acquires a coating called as pellicle which is composed of various proteins and glycoproteins of host origin. Then with the help of adhesion molecules and pilli, first *Streptococci* then *Actinomycetes* colonizes the teeth surface. Bacterial cells start interacting with each other on the pellicle and a number of *Streptococci* and related organisms starts synthesizing insoluble glucan via glucan binding protein. After few successive colonization with few more organisms, demineralization of tooth enamel starts (which leads to caries) by the acids which are produced by fermentation of the dietary sucrose and other carbohydrates [11].

## **8.2 Native valve endocarditis (NVE)**

This condition arises due to the interaction between bacteria, vascular endothelium and generally of mitral, aortic, tricuspid and pulmonary valves of the heart. The organisms responsible for these conditions are species of *Streptococcus*, *Staphylococcus*, *Pneumococci*, *Candida*, *Aspergillus,* and some Gram-negative bacteria, which get access to the blood stream via the oropharynx, gastrointestinal, and urinary tract. When the intact endothelium gets damaged, microbes

### *Bacterial Biofilms*

adhered to it and as a result nonbacterial endocarditis (NBTE) develops at the site of injury and thrombus (accumulation of platelets, fibrin, and red blood cells) formed [13]. Fibronectin which has been found as a thrombotic lesion of the heart valve can simultaneously bind to fibrin, collagen, human cell and bacteria. Fibronectin receptors are found in many bacterial species like *Staphylococcus and Streptococcus* [5]*.*

Many antibiotic therapies are suggested depending on the organisms involved as Penicillin is recommended for normal treatment of *Streptococcal endocarditis* and for synergistic killing gentamycin may be supplemented. Fluconazole can successfully terminate the effect of *Candida endocarditis* [5].
