BacteriaBacteria (bækˈtɪəriə; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria play a vital role in many stages of the nutrient cycle by recycling nutrients and the fixation of nitrogen from the atmosphere.
Passive immunityPassive immunity is the transfer of active humoral immunity of ready-made antibodies. Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta, and it can also be induced artificially, when high levels of antibodies specific to a pathogen or toxin (obtained from humans, horses, or other animals) are transferred to non-immune persons through blood products that contain antibodies, such as in immunoglobulin therapy or antiserum therapy.
AntiserumAntiserum is a blood serum containing monoclonal or polyclonal antibodies that is used to spread passive immunity to many diseases via blood donation (plasmapheresis). For example, convalescent serum, passive antibody transfusion from a previous human survivor, used to be the only known effective treatment for ebola infection with a high success rate of 7 out of 8 patients surviving. Antisera are widely used in diagnostic virology laboratories. The most common use of antiserum in humans is as antitoxin or antivenom to treat envenomation.
DiphtheriaDiphtheria is an infection caused by the bacterium Corynebacterium diphtheriae. Most infections are asymptomatic or have a mild clinical course, but in some outbreaks the lethality rate approaches 10%. Signs and symptoms may vary from mild to severe and usually start two to five days after exposure. Symptoms often develop gradually, beginning with a sore throat and fever. In severe cases, a grey or white patch develops in the throat, which can block the airway and create a barking cough similar to what is observed in croup.
Pathogenic bacteriaPathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases. The number of these pathogenic species in humans is estimated to be fewer than a hundred. By contrast, several thousand species are part of the gut flora present in the digestive tract.
InoculationInoculation is the act of implanting a pathogen or other microbe or virus into a person or other organism. It is a method of artificially inducing immunity against various infectious diseases. The term "inoculation" is also used more generally to refer to intentionally depositing microbes into any growth medium, as into a Petri dish used to culture the microbe, or into food ingredients for making cultured foods such as yoghurt and fermented beverages such as beer and wine.
