A comprehensive inventory of the ten common anaerobic bacteria

In the environment we live in, there has always been a group of microorganisms that can only grow in an oxygen-free or low-oxygen environment, which play a very important role in human health, that is, anaerobic microorganisms
.
The vast majority of anaerobic microorganisms are bacteria, a few are actinomycetes, and a very few are mycoplasma, so they are often called anaerobic bacteria
.

Anaerobic microorganisms are widely present in the environment where humans live, so they have always been the focus
of attention of scientists and doctors.
In recent years, with the continuous improvement of microbial detection methods, anaerobic microorganisms are gradually entering people's attention and are attracting more and more attention
.
Today, the editor will take you to know them
.

What are anaerobic bacteria

Anaerobic bacteria refer to a class of bacteria
that can grow and multiply under conditions of no oxygen or low redox potential.
Due to the lack of a perfect enzyme system, these bacteria can only metabolize
energy by anaerobic fermentation.

Distribution and hazard of anaerobic bacteria

Anaerobes are widely distributed in nature, including the
environment, soil, water sources and animals.
Among them, the human body itself also has many anaerobic bacteria, most of which exist on the skin of human and animal animals, and the deep mucous membrane surface
of the cavity.

Under normal circumstances, most anaerobic bacteria are harmless to the human body, only when tissue ischemia, necrosis or aerobic bacteria infection, etc.
, will induce infection, resulting in intra-abdominal infection, periodontitis and gynecological inflammation, trauma and upper respiratory tract infection and a series of diseases
.

Anaerobic bacteria classification

Depending on the degree of tolerance to anaerobics, it can be divided into three main categories:

1.
Anaerobic bacteria that are extremely sensitive to oxygen: These bacteria have high requirements for anaerobic conditions, and they die after exposure to the air for 10min, and it is clinically difficult to isolate
.

2.
Moderate anaerobic bacteria: such anaerobic bacteria are more common, under the corresponding technical conditions, easy to be isolated, even if exposed to the air for 60~90min or after 72h of pus withdrawal
, it can still be isolated.

3.
Aerobic anaerobic bacteria: This type of bacteria cannot use oxygen and grow well under anaerobic conditions, while they do not grow well
under aerobic conditions.

Common anaerobic bacteria in life

Clostridium tetanus

Clostridium etani is a pathogen that causes tetanus, a gram-positive anaerobic bacterium with a length of 4~8μm and a width of 0.
3~0.
5μm
.
It is widely distributed in nature in the form of spores, such as soil, human and animal intestines, feces, skin and rust
surfaces.

In a hypoxic environment, tetani spores develop into proliferators that multiply rapidly and produce large amounts of tetanus hemolytic toxin and tetanus spasm
.
The former can cause necrosis of local tissues and myocardial damage; The latter is a neurotoxin that causes the main clinical symptoms of tetanus and is one of the strongest known toxins, with a minimum lethal dose of only 2.
5 ng/kg
in humans.

Clostridium perfringens

Clostridium perfringen, a genus of clostridia, is an anaerobic, unmotilated, spores-producing gram-positive coarse bacillus, arranged alone or in pairs, two blunt circles, large spores, oval, located at the secondary end, and can form a capsule in the body
.

Clostridium perfringens belongs to the members of the normal flora in the intestines of humans and animals, is a conditional pathogenic bacteria in the intestines, under normal circumstances does not cause disease, when the body is affected by diet, drugs, microorganisms, environmental factors and changes in its own physiological state, the balance of intestinal flora will be destroyed, resulting in intestinal dysfunction, at this time Clostridium perfringens overmultiplication, so that the normal intestinal flora is inhibited, and exotoxins
are produced.
Because the bacterium is present in the feces of human feces and warm-blooded animals, it can be used as an indicator of
fecal contamination of water and soil.

Clostridium botulinum

Clostridium botulinum botulinum is a gram-positive anaerobic bacillus with flagella without capsule and is widely distributed in
nature, soil, oceans, lake sediments and human and animal waste.
The bacterium is tenacious in nature, can survive for decades in a dry environment, and is generally not pathogenic in the aerobic state
.
In an anaerobic environment, a highly toxic neuroexotoxin, Botulinum toxin, is secreted, which is more toxic than any other known natural toxin, and 0.
1-1 μg can cause human poisoning death
.

Clostridium botulinum often contaminates and breeds in sausages, ham, fish and fish products and canned food, and because of its spores heat resistance, it generally takes 1~6h to boil, or 121 °C high-pressure steam for 4~10min to kill, which is easy to cause food poisoning
.
At present, in the food industry, the sterilization effect of canned food is generally indicated by Clostridium botulinum
.

Clostridium difficile

Clostridium difficile, also known as Clostridium difficile, is a strictly obligate anaerobic bacterium without capsule and positive for Gram stain coarse longevia, which tends to turn gram-negative after 2 days of culture
.
It is mainly distributed in soil, water, hay, sand, animal and human feces, in addition to a large number of infants' intestines, which is a normal flora
in the intestines of newborns.
The bacterium can cause pyelonephritis, meningitis, abdominal and vaginal infections, bacteremia and gas gangrene, and is currently one of
the pathogenic bacteria infected in hospitals.

P.
gingivalis

Porphyromonas gingivalis is an obligate anaerobic gram-negative coccus closely related to adult periodontitis, and is also the most typical gram-negative anaerobic bacterium that causes chronic periodontitis, with no sugar decomposition properties but protein decomposition properties
.
P.
gingivalis is present in healthy people and is considered a host-adaptive pathogen that can cause disease
only when the ecological balance between host and bacteria is disrupted.
At the same time, the bacterium may also be involved in regulating the development of plaque biofilms, coordinating and controlling their pathophysiological mechanisms to reduce damage to the host
.

Shigella

Shigella (Shigella), commonly known as dysentery bacillus, is a facultative anaerobic gram-negative bacillus that is hardy and can break down glucose, producing acid but not gas
.
According to its different antigenic structure, it can be divided into four groups: dysentery, Fowler, Bao and Shigella sonnei, with a total of 48 serotypes
.
Shigella is the most common pathogen of human bacterial dysentery, prevalent mainly in developing countries, with more than 200 million
cases worldwide each year.
In China, Shigella food poisoning, mainly caused by Shigella sonnei, is transmitted
via the fecal-oral route.
Such poisoning mostly occurs in summer and autumn, caused by drinking water, hot meat products, etc
.

Lactobacillus

Lactobacillus is a group of rod-shaped or globular gram-positive bacteria named for the fermentation of
sugars due to large amounts of lactic acid.
Its existence is extensive, eosinophilic, can survive in the environment of pH 3~6, is the strongest acid resistance among Bacillus-free bacilli, generally reproduced
under anaerobic conditions.
This group of bacteria is widely distributed, animals and humans from the mouth to the rectum always have the bacteria, and most of them are non-toxic and harmless to animals and humans, bearing important physiological functions
in animals.

Studies have shown that lactobacillus has the effects
of inhibiting pathogenic bacteria, fighting infection, maintaining the microecological balance of the intestines, preventing and inhibiting the occurrence of tumors, enhancing the body's immunity, promoting digestion, synthesizing amino acids and vitamins, lowering cholesterol, inhibiting the production of endotoxins, and delaying aging.

Bifidobacteria

Bifidobacterium, the name of a bacterial genus, is a class of Gram-positive, non-motile, rod-shaped cells with sometimes bifurcated ends, and strictly anaerobic bacteria
.
It is widely found in the digestive tract, vagina and oral cavity of humans and animals, and is one of the important members of the intestinal flora of humans and animals, and is also an important class of beneficial intestinal microorganisms
.

Studies have shown that bifidobacteria can inhibit the growth of harmful bacteria in the human body, resist the infection of pathogenic bacteria, synthesize vitamins needed by the human body, promote the absorption of minerals by the human body, produce organic acids such as acetic acid, propionic acid, butyric acid and lactic acid to stimulate intestinal peristalsis, promote defecation, prevent constipation and inhibit intestinal spoilage, purify the intestinal environment, decompose carcinogens, stimulate the human immune system, and thus improve disease resistance
.

Helicobacter pylori

Helicobacter pylori is a gram-negative bacillus that is spiral-shaped, microaerobic, and very demanding on growth conditions
.
At present, the bacterium is the most common infection of the digestive system, with an average infection rate of about 50% worldwide, and even about 70% in some developing countries, which is considered to be one of
the most widespread infections in the world.
Helicobacter pylori is mainly distributed in the gastric mucosal tissue, which is a major cause of a variety of diseases in the stomach, and causes cancer in severe cases, so it is currently the key examination object
in clinical medicine.

Campylobacter

Campylobacter, comma-shaped or S-shaped, microaerobic, gram-negative bacteria
.
There are more than 10 species in the genus Campylobacter that can cause disease in humans, the most common of which are Campylobacter jejuni and Campylobacter colon, which account for 90%
of Campylobacter infections in humans.
Campylobacter is widely distributed in poultry, livestock and other animals, the fungus mainly settles in the intestines of poultry, livestock and other animals, and is also one of the pathogenic bacteria of
zoonoses.
At present, Campylobacter jejuni is a common foodborne pathogen in humans, which mainly causes acute enteritis after infection, and in severe cases, it will cause Guillain-Barré syndrome, seriously endangering human health, so the bacterium is receiving more and more attention
.