Primary pathogen

Examples of Primary pathogen in the following topics:

• Extent of Host Involvement

  • Clinicians therefore classify infectious microorganisms or microbes according to the status of host defenses - either as primary pathogens or as opportunistic pathogens.
  • Primary pathogens cause disease as a result of their presence or activity within the normal, healthy host, and their intrinsic virulence is, in part, a necessary consequence of their need to reproduce and spread.
  • Many of the most common primary pathogens of humans only infect humans; however many serious diseases are caused by organisms acquired from the environment or which infect non-human hosts.
  • Primary pathogens may also cause more severe disease in a host with depressed resistance than would normally occur in an immunosufficient host.
  • Differentiate between primary and opportunistic pathogens in regards to host involvement

• 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.
  • Skin flora are usually non-pathogenic and either commensal or mutualistic.
  • Infectious disease results from the interplay between those few pathogens and the defenses of the hosts they infect.
  • Primary pathogens cause disease as a result of their presence or activity within the normal, healthy host.
  • The success of any pathogen depends on its ability to elude host immune responses.

• Immunological Memory

  • During the adaptive immune response to a pathogen that has not been encountered before, known as the primary immune response, plasma cells secreting antibodies and differentiated T cells increase, then plateau over time.
  • A memory cell is an antigen-specific B or T lymphocyte that does not differentiate into an effector cell during the primary immune response, but that can immediately become an effector cell on re-exposure to the same pathogen.
  • Memory B cells that differentiate into plasma cells output ten to hundred-fold greater antibody amounts than were secreted during the primary response .
  • Vaccination is based on the knowledge that exposure to noninfectious antigens, derived from known pathogens, generates a mild primary immune response .
  • In the primary response to infection, antibodies are secreted first from plasma cells.

• Natural Active Immunity

  • Naturally acquired active immunity occurs when a person is exposed to a live pathogen, develops the disease, and then develops immunity.
  • Naturally acquired active immunity occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary immune response.
  • Once a microbe penetrates the body's skin, mucous membranes, or other primary defenses, it interacts with the immune system.
  • The adaptive immune response generated against the pathogen takes days or weeks to develop but may be long-lasting, or even lifelong.
  • The principle behind immunization is to introduce an antigen, derived from a disease-causing organism, that stimulates the immune system to develop protective immunity against that organism, but which does not itself cause the pathogenic effects of that organism.

• Ecology, Epidemiology, and Evolution of Pathogens

  • Pathogens have evolved to adapt to their environment and their host in order to survive.
  • If a pathogen does not have this, it will likely become extinct.
  • In the case of plant pathogens, it is also their ability to survive between growing seasons.
  • For example, peanut clump virus can survive in the spores of its fungal vector until a new growing season begins and it can proceed to infect its primary host again.
  • Diseases can emerge when existing parasites become pathogenic or when new pathogenic parasites enter a new host.

• Primary and Secondary Antibody Responses

  • Pathogens can rapidly evolve and adapt to avoid detection and neutralization by the immune system.
  • As a result, multiple defense mechanisms have also evolved to recognize and neutralize pathogens .
  • Adaptive (or acquired) immunity creates immunological memory after an initial response to a specific pathogen, leading to an enhanced response to subsequent encounters with that same pathogen.
  • When B cells and T cells are first activated by a pathogen, memory B-cells and T- cells develop.
  • Throughout the lifetime of an animal these memory cells will "remember" each specific pathogen encountered, and are able to mount a strong response if the pathogen is detected again.

• Protists as Human Pathogens

  • A pathogen is anything that causes disease.
  • A significant number of protists are pathogenic parasites that must infect other organisms to survive and propagate.
  • Of the four Plasmodium species known to infect humans, P. falciparum accounts for 50 percent of all malaria cases and is the primary cause of disease-related fatalities in tropical regions of the world.

• Primary Immunodeficiency Diseases

  • The precise symptoms of a primary immunodeficiency depend on the type of defect.
  • These proteins, generated by plasma cells, normally bind to pathogens, targeting them for destruction.
  • Phagocytes are the cells that engulf and ingest pathogens (phagocytosis), and destroy them with chemicals.
  • Reduction of exposure to pathogens may be recommended, and in many situations prophylactic antibiotics may be advised.
  • Describe primary immunodeficiency disorders and explain what treatment options are available

• Primary and Secondary Metabolites

  • Pathogenic bacteria are capable of exhibiting various types of metabolism.
  • Metabolites can be categorized into both primary and secondary metabolites.
  • Primary metabolites are involved in growth, development, and reproduction of the organism.
  • Examples of primary metabolites include alcohols such as ethanol, lactic acid, and certain amino acids.
  • Another example of a primary metabolite commonly used in industrial microbiology includes citric acid.

• Cells and Organs of the Immune System

  • The immune system includes primary lymphoid organs, secondary lymphatic tissues and various cells in the innate and adaptive immune systems.
  • The red bone marrow is a key element of the lymphatic system, being one of the primary lymphoid organs that generate lymphocytes from immature hematopoietic progenitor cells.
  • Bone marrow and thymus constitute the primary lymphoid tissues involved in the production and early selection of lymphocytes.
  • Neutrophils and macrophages are phagocytes that travel throughout the body in pursuit of invading pathogens.
  • These cells have no cytotoxic activity and do not kill infected cells or clear pathogens directly.