Bacterial pathogenesis is the process by which bacteria infect and cause disease in a host. Not all bacteria are pathogens and have the ability for pathogenesis (also known as virulence). Pathogenic bacteria utilise a number of mechanisms to cause disease in human hosts. Bacterial pathogens express a wide range of molecules that bind host cell targets to facilitate a variety of different host responses. The molecular strategies used by bacteria to interact with the host can be unique to specific pathogens or conserved across several different species. A key to fighting bacterial disease is the identification and characterisation of all these different strategies. The availability of complete genome sequences for several bacterial pathogens coupled with bioinformatics will lead to significant advances toward this goal. There are several bacterial pathogenic diseases. One among them is tuberculosis which is caused by Mycobacterium tuberculosis. It includes other pathogens of bacteria such as Streptococcus and Pseudomonas. These pathogens and form of bacteria causes many foodborne illnesses and infections such as tetanus, typhoid fever and diphtheria. Microbes express their pathogenicity by means of their virulence. The determinants of virulence of a pathogen are any of its genetic or biochemical or structural features that enable it to produce disease in a host. In bacterial host mediated pathogenesis, (e.g., tuberculosis), tissue damage results from the toxic mediators released by lymphoid cells rather than from bacterial toxins.