pathogenic bacteria

Examples of pathogenic bacteria in the following topics:

• Extent of Host Involvement

  • Host-pathogen interactions are the interactions taking place between a pathogen (e.g. virus, bacteria) and their host (e.g. humans, plants).
  • Host-pathogen interactions are the interactions that take place between a pathogen (e.g. virus, bacteria) and their host (e.g. humans, plants).
  • By definition, all pathogens damage their host to some extent.
  • The appearance and severity of disease resulting from the presence of any pathogen depends upon the ability of that pathogen to damage the host as well as the ability of the host to resist the pathogen.
  • Opportunistic diseases may be caused by microbes that are ordinarily in contact with the host, such as pathogenic bacteria or fungi in the gastrointestinal or the upper respiratory tract, and they may also result from (otherwise innocuous) microbes acquired from other hosts or from the environment as a result of traumatic introduction.

• Overview of Human-Microbial Reactions

  • Human-microbial interactions can be commensal or mutualistic, as with many types of gut flora, or harmful, as with pathogenic bacteria.
  • The metabolic activities performed by these bacteria resemble those of an organ, leading some to liken gut bacteria to a "forgotten" organ.
  • The benefits of bacteria include preventing transient pathogenic organisms from colonizing the skin surface, either by competing for nutrients, secreting chemicals against them, or stimulating the skin's immune system.
  • Infectious pathogens include some viruses, bacteria, fungi, protozoa, multicellular parasites, and aberrant proteins known as prions.
  • Opportunistic disease may be caused by microbes that are ordinarily in contact with the host, such as pathogenic bacteria or fungi in the gastrointestinal tract.

• Siderophores

  • The siderophores are then utilized by the pathogen to obtain iron.
  • The pathogenic bacteria, Yersinia pestis, Yersinia pseduotuberculosis, and Yersinia enterocolitica have the ability to produce a siderophore called yersiniabactin.
  • The yersiniabactin-Fe3+ complex will then bind to the outer membrane of the bacteria based on specific receptor recognition.
  • Pathogenic bacteria such as Escherichia coli and Salmonella typhimurium have the ability to produce a siderophore called enterobactin.
  • Due to the high-binding affinity of enterobactin, the bacteria require a highly specific enzyme, ferrienterobactin esterase, to cleave the iron from the complex.

• Microorganisms and Water Quality

  • Although there are many pathogens which can be transmitted through water, bacteria and protozoa are some of the most common organisms that cause disease.
  • Monitoring for waterborne disease can be difficult because humans often shed very low numbers of pathogenic bacteria when they are infected.
  • To test whether disease causing bacteria might be present, researchers measure the presence of indicator species, such as coliform bacteria (which are the group to which the pathogenic E. coli belongs) or Pseudomonas aeruginosa.
  • If the number of bacteria exceeds the limits set by water quality standards, the next step is to test for the presence of specific pathogens.
  • An influx of human pathogens can cause problems for ecosystems in several ways.

• Intracellular Pathogens

  • Not all pathogens are undesirable to humans.
  • There are several types of intracellular pathogens.
  • Pathogenic viruses are mainly those of the families of Adenoviridae, bacteria Picornaviridae, Herpesviridae, Hepadnaviridae, Flaviviridae, Retroviridae, Orthomyxoviridae, Paramyxoviridae, Papovaviridae, Polyomavirus, Rhabdoviridae, and Togaviridae.
  • Although the vast majority of bacteria are harmless or beneficial, a few pathogenic bacteria can cause infectious diseases.
  • Bacteria can often be killed by antibiotics because the cell wall in the outside is destroyed, expelling the DNA out of the body of the pathogen, therefore making the pathogen incapable of producing proteins, so it dies.

• Plant Pathogens

  • Most bacteria that are associated with plants are actually saprophytic, and do no harm to the plant itself.
  • Most plant pathogenic bacteria are rod shaped (bacilli).
  • In order to be able to colonise the plant they have specific pathogenicity factors.
  • There are 4 main bacterial pathogenicity factors:
  • Bacteria, fungus and oomycetes are known for this function.

• Direct Damage

  • The pathogenic organism typically causes damage due to its own growth process.
  • The ability of a pathogen to gain entrance to a host cell is fundamental in the ability of the pathogen to promote and cause disease.
  • This is accomplished by the ability of the bacteria to exhibit produce molecules that interfere with the phagocytes ability to internalize the bacteria.
  • Once the pathogen has successfully evaded engulfment and destruction by the immune system, it is detrimental because the bacteria then multiply.
  • Describe the different processes used by pathogens to damage the host and ensure infection

• Extracellular Immune Avoidance

  • A pathogen's success depends on its ability to evade the host's immune responses.
  • A pathogen's success depends on its ability to evade the host's immune responses.
  • Bacteria usually overcome physical barriers by secreting enzymes that digest the barrier in the manner of a type II secretion system.
  • Some bacteria even form biofilms which protect them from the proteins and cells of the immune system.
  • Some bacteria create surface proteins, such as Streptococcus, that will bind to antibodies making them ineffective.

• Regulating Virulence

  • The ability of a microorganism to cause disease is described in terms of the number of infecting bacteria, the route of entry into the body, the effects of host defense mechanisms, and intrinsic characteristics of the microorganism called virulence factors.
  • Pathogen strains that kill the host can increase in frequency as long as the pathogen can transmit itself to a new host, whether before or after the host dies.
  • The evolution of virulence in pathogens is a balance between the costs and benefits of virulence to the pathogen.
  • After C. tetani bacteria enter a human wound, the bacteria may grow and divide rapidly, even though the human body is not their normal habitat.
  • The bacteria Mycobacterium tuberculosis can evolve to subvert the protection offered by immune defenses.

• Pathogenicity Islands and Virulence Factors

  • Pathogenicity islands (PAIs) are a distinct class of genomic islands acquired by microorganisms through horizontal gene transfer.
  • Pathogenicity islands (PAIs) are a distinct class of genomic islands acquired by microorganisms through horizontal gene transfer.
  • They are incorporated in the genome of pathogenic organisms, but are usually absent from those nonpathogenic organisms of the same or closely related species.
  • These mobile genetic elements may range from 10-200 kb, and may encode genes contributing to the virulence of the respective pathogen.
  • One species of bacteria may have more than one PAI (i.e. salmonella has at least five).