Pathogens
Pathogenic bacteria are bacteria that can cause infection.
Although most bacteria are harmless or often beneficial, several are pathogenic. One of the bacterial diseases with the highest disease burden is tuberculosis, caused by the bacterium Mycobacterium tuberculosis, which kills about 2 million people a year, mostly in sub-Saharan Africa. Pathogenic bacteria contribute to other globally important diseases, such as pneumonia, which can be caused by bacteria such as Streptococcus and Pseudomonas, and foodborne illnesses, which can be caused by bacteria such as Shigella, Campylobacter, and Salmonella. Pathogenic bacteria also cause infections such as tetanus, typhoid fever, diphtheria, syphilis, and leprosy. Pathogenic bacteria are also the cause of high infant mortality rates in developing countries.[
Pathogenic susceptibility
Some pathogenic bacteria cause disease under certain conditions, such entry through the skin via a cut, through sexual activity or an compromised immune function.
Streptococcus and Staphylococcus are part of the normal skin microbiota and typically reside on healthy skin or in the nasopharangeal region. Yet these species can potentially initiate skin infections. They are also able to cause sepsis, pneumonia, meningitis. These infections can become quite serious creating a systemic inflammatory response resulting in massive vasodilation, shock, and death.[2]
Other bacteria are opportunistic pathogens and cause disease mainly in people suffering from immunosuppression or cystic fibrosis Examples of these opportunistic pathogens include Pseudomonas aeruginosa, Burkholderia cenocepacia, and Mycobacterium avium.[3][4]
Intracellular
Obligate intracellular parasites (e.g. Chlamydophila, Ehrlichia, Rickettsia) have the ability to only grow and replicate inside other cells. Even these intracellular infections may be asymptomatic, requiring an incubation period. An example of this Rickettsia which causes typhus. Another causes Rocky Mountain spotted fever.
Chlamydia is a phylum of intracellular parasites. These pathogens can cause pneumonia or urinary tract infection and may be involved in coronary heart disease.
Other groups of intracellular bacterial pathogens include: Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, and Yersinia pestis. These can exist intracellularly, but can exist outside of host cells.
Infections in specific tissue
