Microscopic view of e. coli bacteria

Type Tests and Characteristics of E. coli (Escherichia coli) Bacteria

Meaning of e. coli: E. coli, also called Escherichia coli, was discovered by Escherich in 1885. Escherichia coli is a conditionally pathogenic bacterium that can cause gastrointestinal infections or urinary tract infections of various tissues and organs in humans and various animals under certain conditions.

 

English name:    Escherichia coli

Latin name:    Escherichiacoli

Nickname:    E.coli

Boundary:    Bacterial community / Bacteriology

Door:    Proteobacteria

Gang:    γ-proteobacteria

Mesh:    Enterobacteriaceae

Section:    Enterobacteriaceae

Genus:    Escherichia

Species:    E.coli

Distribution area:    Normal inhabitants of human and animal intestines

 

Table of Content

    1 Introduction

    2 Type

    ▪ According to pathogenic effect

    ▪ By Hemolysis

    ▪ According to enterotoxigenicity

    3 Biological characteristics

    ▪ Physical and chemical properties

    ▪ Biochemical characteristics

    ▪ Pathogenic properties

    4 Epidemiological characteristics

    ▪ Regional distribution

    ▪ Susceptible host

    ▪ Season of onset

    ▪ Source of infection and route of transmission

    5 Testing methods

    ▪ Fermentation method

    ▪ Membrane method

    ▪ Tablet counting method

    ▪ Immunomagnetic bead method

    ▪ Automated instrument testing method

    ▪ ATP bioluminescence method

 

Introduction to E. coli (Escherichia coli)

This bacterium is Bacteroides brevis with blunt ends at both ends, and this bacterium mostly exists alone or in pairs.

This bacterium is Bacteroides brevis with blunt ends at both ends, and this bacterium mostly exists alone or in pairs.

E. coli is a normal resident bacteria in the intestines of animals, and a small part of them cause disease under certain conditions.

The serotypes of E. coli can cause gastrointestinal infections in humans or animals, mainly caused by specific fimbria antigens, pathogenic toxins and other infections.

In addition to gastrointestinal infections, it can also cause urinary tract infections, arthritis, and meninges. Inflammation and septic infections.

 

What is the Type or Classification of e.coli Bacteria?

Pathogenic effect

At present, the internationally recognized classification mainly includes six types of E. coli, namely:

  1. Intestinal Pathogenic E. coli (EPEC)
  2. Intestinal Toxigenic E. coli (ETEC) and itestinal invasion that can cause gastrointestinal infections.
  3. Escherichia coli (EIEC)
  4. Intestinal Hemorrhagic Escherichia coli (EHEC)
  5. Intestinal Aggregative Escherichia coli (EAEC)
  6. Intestinal Shiga-like toxins found in recent years also have certain invasive Escherichia coli (ESIES)

 

In addition, there are urethral pathogenic Escherichia coli (UPEC) that can cause urinary tract infection, and the newly named intestinal agglomerative adherent E. coli (EAggEC)

 

Hemolytic

According to the ability of E. coli to produce hemolysin and the ability to hemolyze, E. coli can be divided into two categories: hemolytic E. coli and non-hemolytic E. coli.

 

Enterotoxigenic

According to the ability of Escherichia coli to produce enterotoxin during the infection process, Escherichia coli can be divided into two categories: enterotoxigenic Escherichia coli and non-entotoxinogenic E. coli.

Enterotoxigenic E. coli is an important pathogen of any infectious diarrhea in humans and various animals.

The identification of enterotoxigenic E. coli is mainly to determine the type of enterotoxin secreted by the isolated E. coli.

In addition, according to E. coli’s ability to produce enterotoxin, combined with its sensitivity to different enterotoxins, E. coli can be typed, called enterotoxin type.

 

What are the Biological Characteristics of e coli (Escherichia coli)?

e. coli Physical and chemical properties

Escherichia coli is Brevibacterium, with blunt round ends and Gram-negative. Sometimes, due to different environments, individual cells appear to be spherical or filament-like.

E. coli are mostly single or two, but they will not be arranged in a long chain shape.

Mmost E. coli strains have capsules or microcapsules Structure, but cannot form spores.

Mmost E. coli strains grow fimbriae, some of which are host-specific fimbriae that have adhesion to the host and some other tissues or cells.

 

e. coli Biochemical properties

The biochemical metabolism of E. coli is very active. E. coli can ferment glucose to produce acid and gas, while some strains do not produce gas. E. coli can also ferment a variety of carbohydrates, and can also use a variety of organic acid salts.

In the commonly used biochemical characteristics test items for E. coli, the methyl red test is positive.

Tthe indole production and lactose fermentation are positive (individual strains are negative).

The Wei-pei test is negative, and the urease and citrate utilization are negative ( Very few strains were positive)

The nitrate reduction test was positive. The oxidase was negative, and the oxidation-fermentation test was F type.

 

e. coli Pathogenic properties

For humans and a variety of animals, pathogenic E. coli often tends to have a certain host specificity, and strains that have a pathogenic effect on humans often cause little infection in animals, and vice versa.

According to which the pathogenic E. coli it is roughly divided into two types: human pathogenic E. coli and animal pathogenic E. coli.

The animal’s diarrheagenic E. coli has been clearly characterized by strains similar to ETEC. UPEC is a group of the most common pathogenic E. coli that can cause human urinary tract infections.

Urinary tract infection is an infection symptom that rarely exists independently in animal colibacillosis .

 

What are the epidemiological characteristics of e coli (Escherichia coli)?

Regional distribution of e. coli

The occurrence and epidemic of E. coli are distributed worldwide, but the epidemic of E. coli still has certain regional distribution characteristics. The characteristics of these regional distributions are more obvious in human E. coli infections, the most likely because they are related to economic conditions and social health conditions among regions.

 

Susceptible host for e. coli

Animal colibacillosis can occur in a variety of domestic animals, poultry, farmed economic animals, other terrestrial animals and certain aquatic animals, of which pigs and chickens are the most susceptible and are very harmful.

 

Season of onset of e. coli

The seasonal incidence of E. coli infection among animal populations is not very obvious. Pigs can occur in all seasons of the year, but as long as they occur from the farrowing period to the weaning period of the pig, this is related to the susceptible age of the pig.

Calves and lambs occur mostly in winter and spring. E. coli infections in other animals occur all year round, and the seasonality is not obvious.

 

Source of infection and route of transmission

The main source of infection of human E. coli disease is that a large number of E. coli pathogens are excreted in the feces of gastrointestinal infection patients.

The transmission route of E. coli among people is mostly through the fecal-oral transmission route, which can cause the spread or epidemic of E. coli disease under certain conditions.

 

What is the e coli ( Escherichia coli ) Detection Method?

The rapid and accurate detection of E. coli in food has become a common concern. The following describes the method and analysis of E. coli detection in food.

 

Fermentation method for e.coli detection

This method is mainly for the cultivation of E. coli on a medium at 44.5 ° C, which contains a fluorescent substrate and requires 24 hours of cultivation.

Then the release of the fluorescent substrate needs to be performed with glucuronic acid, so that the medium can fluoresce under the irradiation of ultraviolet light.

In this way, the colonies in the original sample can also be statistically estimated. The main steps include fermentation, separation culture, secondary fermentation, microscope observation, etc.

 

Membrane method for e.coli detection

The main process of this method: Add about 10 mL of sterile water to the filter, then mix some sterile water to clean the inner wall of the filter, and then filter, put the filter membrane in M-FC medium, between the two.

There should be no bubbles, and then sealed, the storage temperature is 44.5 , the storage time is about 24 h, until the E. coli flora becomes blue or blue-green. Then record the data, estimate the number of bacteria in each unit of the aqueous solution, and then convert the amount of E. coli.

 

Tablet Counting Method

Use a sterile pipette to draw 1 mL of the dilution sample, which is similar to lactose bile salt fermentation, and then place it in a sterile Petri dish.

Then add 10 mL of CDLJ JD chromogenic medium at 45 ° C, and mix the solution in the Petri dish evenly.

You can quickly turn the Petri dish and wait for the solution to solidify, then add about 5 mL.  Then, shake the medium quickly so that it can evenly cover the surface of the plate. After it solidifies, turn the medium over and incubate at a temperature of 37 ° C for about 24 h, and then observe the changes in shape and color.

In addition, two dilution media are set in parallel. The first step is to dilute the sample.

After dilution, the microorganisms can be dispersed into single cells, and then cultured under certain environmental conditions until they grow into colonies, and then calculate the large intestine.

The number of bacilli is calculated by the dilution and the number of samples.

 

Immunomagnetic bead method

The main principle of the separation technology is to use magnetic beads as a carrier and an antibody to combine the antibody and the magnetic beads. Then complete the mechanical movement through magnetic technology to further isolate E. coli.

Compared with other ways of separating bacteria, this method has certain advantages. This technology can improve the detection success rate of pathogenic Vibrio in samples. The immunomagnetic bead technology can treat different microorganisms in different bacterial species, and to a large extent improve the detection efficiency.

 

Automated instrument testing

The main use of immune automated analyzer, this technology was produced and used in 1970.

With the development and progress of science and technology, automatic instrument detection technology is widely used, and it is very convenient to operate.

It can save a lot of time. Its degree of interference is small.

It can save manpower and material investment, and can also improve the accuracy of detection.

In the current development process, the application of automatic enzyme immunoassay system is very extensive.

 

ATP bioluminescence

In the development process in recent years, bioluminescence technology is widely used, and it is a relatively rapid technology for detecting microorganisms.

In active cells, ATP is its common energy metabolic product, which can provide the energy required during the physiological activities of cells.

This technology can maintain a certain content within a certain range in the living body.

The detection technology of Escherichia coli in food can adopt the method of fluorescence photometry.  This is because the reason that the organism emits light is the role of luciferase, which produces the effect of light emission.

The substance comes from the fireflies in North America and can catalyze the oxidation of fluorescein. However, the substance is unstable and can quickly decompose the fluorescence.

In addition, the process of obtaining the results of the detection technology is very fast, and the device is easy to carry, which is very suitable for on-site detection.

 

See also:

 

 

 

 

 

 

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