Common coliform bacteria. Bacteria of the Escherichia coli group

Modern sanitary microbiology, when indicating and identifying sanitary-indicative and pathogenic microorganisms, when determining the total microbial contamination of environmental objects, seeks to use all the methods that are used in diagnostic microbiological laboratories:

microscopic– for indication and direct counting of microorganisms in the test object;

bacteriological– isolation of microorganisms and their identification;

biological– infection of sensitive animals and accelerated methods research (RIF, etc.).

To obtain a versatile and complete sanitary and microbiological characteristics of environmental objects, as a rule, a set of tests is used. These include the determination of the total microbial contamination (total microbial number).

The total microbial contamination of an object is characterized by the number of microorganisms in 1 ml of water, liquid or 1 g of a solid (product). Determination of the microbial number is an indirect method and makes it possible to judge the possibility of contamination of the object under study with pathogenic microorganisms.

There are two methods for determining microbial contamination:

Method of direct counting under a microscope;

The method of quantitative inoculation of various dilutions of samples and samples of the object under study.

The first method - the method of direct counting of microorganisms in the object under study is carried out under a microscope in Goryaev's counting chambers or in chambers specially designed for counting bacteria. Previously, the sample of the object under study is subjected to processing in order to obtain a homogeneous suspension. To better account for bacteria, a dye is added to the test suspension.

The second method - the method of quantitative inoculation of the test material on dense nutrient media - is used most often. From the prepared serial tenfold dilutions of the test liquid or suspension, 1 ml is transferred into sterile Petri dishes (starting with a larger dilution, each dilution with a separate pipette) and poured with meat-peptone agar melted and cooled to 45-50 0 C.

It should be noted that both methods for determining the total microbial contamination are relative and approximate. To obtain comparable results in determining the total microbial number, studies are carried out according to standard, specific for each case, methods regulated by the relevant GOSTs.

Identification in each specific case of damage to an environmental object is carried out according to the research schemes developed for each group of microorganisms.

Bacteria of the Escherichia coli group (bgcp)

Escherihia coli (E. coli) was first isolated by T. Escherich in 1885 from the feces of a patient. E. coli is a permanent inhabitant of the large intestine of humans, mammals, birds and fish. Among E. coli bacteria, along with saprophytic strains, there are enteropathogenic ones that can cause gastrointestinal diseases in humans and animals.

Morphology. These are polymorphic rods with rounded ends, 1-3 μm long, gram-negative, non-spore-forming, motile peritrichous (some immobile). The capsule is formed only by pathogenic serovars (08, 09, 0101).

cultural properties. E. coli aerobe or facultative anaerobe, optimal growth temperature 37-38 0 C, pH 7.0-7.4. It grows well on ordinary nutrient media - MPA, MPB, Endo and Levin media. On MPA, after 24 hours, juicy, round with smooth edges and a smooth surface (s-shape) gray-white colonies appear. In MPB form an intense turbidity of the medium and a precipitate at the bottom of the test tube, easily broken when shaken.

Biochemical(enzymatic) properties in bacteria E. coli are well expressed, unlike other bacteria of the Enterobacteriaciae family, they ferment lactose to acid and gas, which is used for differentiation and identification.

The bacteria of the E. coli group include 3 genera of bacteria: Escherihia, Citrobacter and Enterobacter. The last two genera are close, in contrast to the genus Escherihia, they have limited sanitary significance and are not regarded as indicators of fresh fecal contamination, since they are more often found in the soil, on plants.

In all previous classifications, much attention was paid to the ability of Escherichia coli to ferment lactose, since it was believed that soil, water, and plants are the habitat of lactose-negative bacteria.

In connection with the unequal sanitary and indicative value of individual genera, a set of signs indicated by the abbreviation - TIMAC.

T– temperature test (Aikman test);

And– test for indole formation;

M– reaction with methyl red;

BUT- reaction to acetymethylcarbinol (Voges-Proskauer reaction);

C- citrate test.

The features included in this complex determine whether CGB belongs to one of three genera: Escherihia, Citrobacter, and Enterobacter.

Temperature test. To confirm the fecal origin of the isolated strains of Escherihia coli, take its ability ferment carbohydrates at a temperature of 43-44 0 With, exceeding the temperature of the human body, i.e. temperature test. Most bacteria of the genera Citrobacter and Enterobacter do not have this ability.

indole formation. The essence of the method is that 98% of the isolated strains of Escherihia coli are able to cleave the amino acid tryptophan, which is part of many proteins and peptones of the nutrient medium, with emphasis range of products, including indole, which stains the nutrient medium red when interacting with reagents containing paramethylamidobenzaldehyde. Bacteria from the genera Citrobacter and Enterobacter do not form indole.

Reaction with methyl red(Clark reaction). This reaction is used to determine the intensity of acid formation during the fermentation of glucose in a nutrient medium. As an indicator, methyl red is used, which changes color from light yellow to red at pH 5.0 and below (at pH above 5.0, the medium remains light yellow). It is believed that typical Escherihia coli ferment glucose to acid and gas more intensively than Enterobacter.

Formation of acetylmethylcarbinol. Using this reaction, the ability of microorganisms to form acetylmethylcarbinol in a medium with glucose is determined. It is formed by Enterobacter, while Escherihia coli and Citrobacter do not have this ability.

The ability of microorganisms to form acetylmethylcarbinol in a medium with glucose is determined by the following method: the same volume of a 40% KOH solution is added to 5 ml of a 4-5 day old culture grown on peptone water with glucose or on Clark's medium. In the presence of acetylmethylcarbinol, the medium turns pink.

citrate test based on the ability of certain microorganisms to digest citric acid and its salts in a nutrient medium.

Citrobacter and Enterobacter grow on citrate media and are called citrate-positive bacteria, while Escherihia coli of fecal origin do not utilize citrate and are citrate-negative.

GOST provides for a citrate test in the control of milk and dairy products on the Coser medium.

Fermentation of lactose. In all pre-existing classifications, much attention was paid to the ability of E. coli to ferment lactose. This feature was differentiating in determining the sanitary and indicative value of the studied microorganisms. It was believed that lactose-negative variants differ from lactose-positive ones in that their habitat is soil, water, and plants.

However, in the intestines of humans and animals, as well as in the external environment, various variants of Escherichia coli can be found, which have signs that are not typical for the genus Escherihia. This is explained by the fact that in E. coli, under the influence of various environmental factors, a number of biological properties change: the loss of the ability to ferment lactose and ferment carbohydrates at 43 0 C and even at 37 0 C.

Therefore, this sign is unstable, therefore, in present time when classifying or confirming the fecal origin of isolated strains of Escherichia coli, the ability not only to ferment lactose, but the ability to ferment carbohydrates at a temperature exceeding the body temperature of humans and animals, i.e. temperature test.

In the TIMAC complex, temperature and citrate tests are the main, most stable ones that allow differentiating CGB of fecal origin from bacteria of the Escherichia coli group living in the external environment.

The use of BGKP as sanitary-indicative

microorganisms in food sanitary microbiology

BGKP are considered a classic indicator of fecal contamination of environmental objects. Depending on the objectives of the study, the entire group of Escherichia coli or its individual representatives are taken into account. From the point of view of their sanitary and hygienic significance, G.P. Kalina (1968) divides BGKP into 3 subgroups.

The first subgroup includes BGKP in the broadest sense of the word (gram-negative rods growing on universal media), fermenting glucose and lactose or only glucose with the formation of K and G (acid and gas) at 37 0 C, which do not have proper sanitary value.

The second group includes bacteria that are of sanitary significance and indicate faecal contamination of indefinite time; they have properties characteristic of the first subgroup, but ferment glucose and lactose or glucose at 43-45 0 C.

The third subgroup includes bacteria that are indicators of fresh and undoubtedly faecal contamination (E. coli). These include microorganisms that have properties characteristic of bacteria of the second subgroup, but do not grow on Coser's medium with citrate salts and ferment carbohydrates at 43-45 0 C.

Currently, many researchers believe that when assessing water quality and food products Representatives of any of the subgroups of Escherichia coli, capable of multiplying at 43 0 C and fermenting glucose with the formation of gas, are of sanitary and indicative importance.

Enteropathogenic Escherichia coli

In its natural habitat - the contents of the large intestine - E. coli is a commensal and, of course, plays a positive role.

At the same time, outbreaks of food toxic infections caused by enteropathogenic Escherichia coli have been repeatedly described in the literature. Studies of the antigenic structure of Escherichia coli have shown that the causative agents of intestinal diseases are certain serological types of E. coli:

In calves, serogroups 08, 09, 015, 0101, etc. are more often distinguished;

In piglets - 08, 09, 0137, 0138, etc.;

In humans, 026, 055, 0111 and some other serogroups, mainly possessing the somatic O-antigen. These types are enteropathogenic.

Enteropathogenic Escherichia coli cause diseases: colibacillosis of young animals, mastitis in cows, acute intestinal diseases in children. Enteropathogenic types of Escherichia coli are also isolated from healthy people and animals. There are opinions that the main cause of the disease may be toxins produced by Escherichia coli in vivo and, therefore, the disease can be considered more like an intoxication than a toxic infection.

The possibility of a disease in humans depends on a number of factors - the dose of the microbe, the age of the patient, the condition of the body, etc.

Decontamination of conditionally suitable meat. If there are dystrophic changes in the muscles, then carcasses and internal organs are subject to recycling. In the absence of such changes, only internal organs are sent for disposal, and carcasses are used for the preparation of products, in technological process which is subject to heat treatment.

coliform bacteria coliform bacteria

gram-asporogenic oxidase-negative, growing on Endo's medium and fermenting lactose with the formation of to-you and gas at 37 ° C for 48 hours, enterobacteria. K. b. normalized according to international standards as an indicator of faecal contamination K. b. together with bacteria similar in St. to you, but fermenting glucose with the formation of to-you and gas during the day, make up the group of Escherichia coli, which is normalized as an indicator of fecal pollution.

(Source: Glossary of Microbiology Terms)

See what "Coliform bacteria" is in other dictionaries:

coliform bacteria- 3.2 coliform bacteria lactose-positive bacteria that are oxidase-negative when tested by a standard test Source: GOST R 52426 2005: Drinking water ...

Coliform bacteria are thermotolerant- bacteria that have all the features of common coliform bacteria and are capable of fermenting lactose to acid and gas at a temperature of 44 C for 24 hours. Indicate fecal feces that have recently entered the water ... ... Official terminology

coliform bacteria common- Common coliform bacteria are gram-negative, non-spore-forming rods that produce aldehyde on differential lactose media, do not have oxidase activity, ferment lactose or mannitol with the formation of acid and gas when ... ... Official terminology

thermotolerant coliform bacteria- Bacteria that have the characteristics of common coliform bacteria, and are also capable of fermenting lactose to acid, aldehyde and gas at a temperature of 44 ° C for 24 hours. Note An indicator group of bacteria indicating fecal ... ...

thermotolerant coliform bacteria- 64 thermotolerant coliform bacteria; thermotolerant coliforms: Bacteria that have the characteristics of common coliform bacteria, and are also capable of fermenting lactose to acid, aldehyde and gas at a temperature of 44 ° C for 24 hours ... ... Dictionary-reference book of terms of normative and technical documentation

common coliform bacteria- common coliforms: Gram-negative, oxidase-negative, non-spore-forming rods capable of growing on differential lactose media, fermenting lactose to acid, aldehyde and gas at 37 °C for 24-48 hours. Note ... Technical Translator's Handbook

Escherichia coli (lat. Escherichia coli) is a microorganism discovered in 1885 by Escherich from the remains of human life. This microorganism is a permanent inhabitant of the large intestine of humans and animals. In addition to E. coli, in the group ... ... Wikipedia

See also: Escherichia coli Bacteria of the Escherichia coli group (BGKP, also called colimorphic and coliform bacteria) a group of bacteria of the Enterobacteriaceae family, conditionally distinguished by morphological and cultural characteristics, used ... ... Wikipedia

GOST 30813-2002: Water and water treatment. Terms and Definitions- Terminology GOST 30813 2002: Water and water treatment. Terms and definitions original document: 65 Escherichia coli; E. coli: Aerobic and facultative anaerobic heat-tolerant coliform bacteria that ferment lactose or mannitol when ... ... Dictionary-reference book of terms of normative and technical documentation

GOST R 52426-2005: Drinking water. Detection and quantification of Escherichia coli and coliform bacteria. Part 1. Membrane filtration method- Terminology GOST R 52426 2005: Drinking water. Detection and quantification of Escherichia coli and coliform bacteria. Part 1. Membrane filtration method original document: 3.4 Escherichia coli (E. coli): Bile-resistant bacteria that … Dictionary-reference book of terms of normative and technical documentation

Sanitary and epidemiological rules and regulations SanPiN 2.1.4.1074-01 “Drinking water. Hygienic requirements for water quality of centralized drinking water supply systems. Quality control." apply to water supplied by water supply systems and intended for public consumption for drinking and domestic purposes, for use in the processing of food raw materials and the production of food products, their storage and trade, as well as for the production of products requiring the use of water of drinking quality.
coliform bacteria

To drink clean water, it must, first of all, be evaluated by the example of the content different kind inclusions. Even tap water can be contaminated with bacteria. And the reason for this is the poor condition of the water supply system. Very often in water, especially untreated today, you can find all kinds of bacteria. And in order for the water to become drinkable, colimorphic bacteria in the water must be destroyed.
Finding bacteria in water is not easy. They cannot be seen or tasted. Any presence of coliform bacteria in water, or any other, can cause mass epidemics. That is why their presence is banned. This can lead to the death of many people. Typhoid fever, dysentery, just those diseases that manifest themselves when drinking water contaminated with Escherichia coli. To avoid mass infection, you need to constantly monitor the composition of the water.

Coliforms have long been considered useful microbial indicators of drinking water quality, mainly because they are easy to detect and quantify.

Common coliform bacteria

Thermotolerant fecal coliforms

According to SanPiN, thermotolerant fecal coliforms should be absent in 100 ml of the studied drinking water.

Thermotolerant fecal coliforms are microorganisms capable of fermenting lactose at 44°C or 44.5°C.
Secondary growth of faecal coliforms in the distribution network is unlikely unless sufficient nutrients are present (BOD greater than 14 mg/l), water temperature is above 13°C and there is no free residual chlorine. This test cuts off the saprophytic microflora.

Coliforms may indicate the ingress of pathogenic microorganisms into the water. Intestinal pathogenic diseases are widespread throughout the world. Among the pathogens found in contaminated drinking water, strains of Salmonella, Shigella, enteropathogenic Escherichia coli, Vibrio cholerae, Yersinia, enterocolitics, campylobacteriosis are found. These organisms cause diseases ranging from mild form gastritis to severe and sometimes fatal forms of dysentery, cholera, typhoid fever.

Other organisms naturally present in environment and not considered pathogenic agents, can sometimes cause opportunistic diseases (i.e., diseases caused by opportunistic microorganisms - Klebsiela, Pseudomonas, etc.). Such infections most often occur in people with impaired immune systems (local or general immunity). Wherein drinking water, used by them, can cause a wide variety of infections, including lesions of the skin, mucous eyes, ear, and nasopharynx.
Do not put yourself and your loved ones in danger, use only proven water!

Today, when health has become not only a necessity, but also fashion brand we are paying more and more attention proper nutrition and physical activity. But very often we forget that our well-being is largely determined by the water balance of the body. And here it is important not only how much water we drink, but also what kind. Coliform bacteria have long been our assistants in determining the quality of water. This living indicator of drinking water quality is easy to detect and count and is used in microbiological analysis. Bacteria in drinking water should not be - this is a fact. But we know little about coliform bacteria in drinking water.

Their army is innumerable

Bacteria are shaped like balls (cocci) and rods (bacilli), spirals (spirilla) and curved (vibrios). Autotrophic bacteria themselves synthesize organic substances from inorganic (photosynthetics and chemosynthetics). But they are in the minority. Most bacteria are heterotrophs, among which saprotrophs are distinguished (they use organic matter waste products and dead parts of living organisms) and symbionts (use organic substances of living organisms or their waste products). Human symbionts are called enterobacteria, and the coliform bacteria we are interested in are precisely such.

Who is this?

Representatives of the genera Escherichia, Citrobacter, Enterobacter and Klebsiella, which are used in sanitary microbiology as markers of the entry of potentially dangerous microorganisms into environmental objects. in plain language- these are bacteria of the E. coli group, that is, everything that looks like E. coli ( Escherichia coli). These are gram-negative (a purely microbiological characteristic in relation to the ability of organisms to stain or not in smears) rods that live in the lower intestines of humans and many warm-blooded animals (livestock and poultry). They end up in water with fecal effluents and can serve as markers of its pollution.

Biochemical characteristics

All bacteria of the Escherichia coli group have the ability to ferment lactose, but do so at different temperatures. There are two groups of bacteria:

• Common coliform bacteria. Carbohydrates are fermented in the temperature range of 35-37°C.
• Fecal or thermotolerant coliform bacteria. Fermentation of carbohydrates occurs at 44.0-44.5°C.

This separation is important when conducting microbiological analysis. Drinking water should not contain common coliform bacteria. They are allowed to enter the drinking water distribution systems, but not more than 5% of samples taken within 12 months. In addition, when common coliform bacteria are found in water, a test for the presence of thermotolerant species is mandatory.

How dangerous are they

Among all representatives of coliform bacteria, representatives of 15 species of various genera are considered opportunistic pathogens. Their habitat is the lower parts of the intestinal tract of humans and animals. This is not the same as pathogenic bacteria. Such organisms are always present in the microflora of the digestive tract, many of them help the body absorb and synthesize vitamins, decompose proteins and carbohydrates. They can become pathogenic (causing diseases) when environmental conditions change, which will lead to their excessive reproduction. Such reasons can be a decrease in immunity, the death of normal microflora after taking medications, inhibition of the protective properties of mucous membranes, and much more. But it is not a fact that a person who has drunk water, even containing these microorganisms, will get sick.

Do we need it?

Identifying coliform bacteria in drinking water is not easy - you can't taste or see them. But for those who are building a house or want to buy a water softener, it is advisable to check the water for their presence. The table below gives the standards for central water supply, but it is worth considering that even in an ordinary cooler bacteria can be found.

In addition to these indicators, bacteriological analysis also operates with other standards. But one thing is important - there should be no bacteria in the water. And their detection is fraught with epidemics and mass infection with pathogenic forms. In Russia and the countries of the Customs Union, there are standards for the content of coliform bacteria in food and water in accordance with TR CU 021/2011 "On Food Safety" and other regulations.

If you decide to take the water for analysis

First of all, familiarize yourself with the rules of sampling (sterile container, personal hygiene before sampling, which are valid for two hours). This is important - but it is an indicator of the purity of the analysis. In the laboratory, cultures will be carried out on various media (agar or broth), where multi-colored colonies of bacteria will grow (it is by their color and shape that coliform bacteria are determined) and the number of microorganisms in the sample will be counted. But coliforms in the samples have different sanitary and epidemiological significance. So, members of the genus Escherichia show a very recent contamination of water with faecal effluent. Presence Citrobacter or Enterobacter show contamination occurring over several weeks.

Ways to eliminate bacteria from water

There are only two ways to eliminate coliform bacteria: disinfection and disinfection. In the first case, the effect on bacteria is chemical, in the second - physical, namely:

• heat treatment;
• exposure to strong oxidizing agents (chlorine, sodium hypochlorite);
• oligodynamia (exposure to silver and gold ions);
• use of ultrasound radioactive radiation, ultraviolet.

Disinfection of wastewater is carried out using elements containing chlorine. In such cases, it is necessary to carry out post-treatment to remove excess chlorine-containing elements that adversely affect the human body. Disinfection using ultraviolet emitters only affects bacteria and leaves no traces in the water. Ozone is also used for disinfection - concentrated liquid oxygen. This method is expensive and difficult to produce, but it is the future. It is completely eco-friendly and will not leave marks in the water we drink. The previously popular method of disinfection - iodization - is now used only for a short time and in areas where the iodine content in the environment is below the norm.

Preventive actions

The ways in which pathogenic coliform strains enter our body are fecal and oral. To ensure personal safety, it is important to follow very simple rules:

• Do not eat unwashed vegetables, herbs, fruits, berries.
• Carefully monitor personal hygiene.
• Do not use water that has not been properly purified. Including for irrigation of agricultural crops. By the way, experienced gardeners and gardeners do not even use rainwater for irrigation.
• Direct routes of infection are the consumption of water and milk that have not passed heat treatment. Boiling (100°C) for one minute kills most of the bacteria.
• Careful bathing in lakes and other bodies of water with stagnant water. They are at risk for the development of conditionally pathogenic flora. The only exceptions are the oceans - high salinity almost completely disinfects their water.

By the way, coolers popular today among the population are far from being so safe. The more people use them, the higher the probability of finding various organisms in the water - both harmless and pathogenic.

Summarizing

There should be no bacteria in our drinking water. None. And not only because they can cause serious disorders of the gastrointestinal tract, even death. It should not contain opportunistic coliform bacteria, which are now used as markers of water pollution by organic matter, feces and other things. That is why government agencies control and monitor the state of not only the water of our supply systems, but also the water of reservoirs and underground sources. And the goal of everyone who cares about their health and the health of their loved ones should be the observance of personal hygiene rules, safety precautions when using water for drinking and washing dishes. Take care of yourself and be healthy!

Many different microorganisms live in water. People drink fluids and come into contact with many microorganisms, among which coliform bacteria are isolated. Some of them pose a serious threat to health and even human life.

To reduce the number of harmful microorganisms in the liquid, special complexes for filtration and water purification are used. But coliform bacteria are too resistant to various temperatures, so it is not so easy to remove them.

Fluid in everyday life

Today, a person can get water for daily consumption from absolutely different sources from wells to bottled water. Many methods have been invented to purify water from any type of pollution and pathogenic microorganisms. The basis of water purification is its filtration or purification with the help of chemical elements.

These types of cleaners help get rid of the following main types of bacteria:

• enterobacteria;
• Pseudomonas aeruginosa;
• cyanobacteria;
• cholera sticks;
• some coliform bacteria.

All these pathogenic microorganisms are dangerous for the human body. Most often they are manifested by disorders of the gastrointestinal tract. Depending on the level of toxicity of the products that bacteria secrete, the degree of manifestation varies in each individual person.

The presence of pathogenic organisms in water is determined by bacterial culture. According to all the rules, such an analysis should be carried out in the laboratories of the water utility. But this does not mean that the consumer cannot independently check the quality of tap water.

coliform bacteria

Coliform thermotolerant bacteria are considered faecal because they enter the water through the excrement of some animals or birds. Harmless bacteria of this species belong to the organisms that inhabit the intestines. Coliforms themselves cannot harm the human body, but symptoms may appear that will accurately indicate that he has been in contact with contaminated water.

Dangerous for humans are those bacteria that enter the water through the excrement of animals. Such coliforms can cause great harm to the human intestinal microflora. Almost all bacteria of this type are thermotolerant, that is, they are not afraid of low temperatures. They can survive and develop at temperatures down to -60 degrees. Bacteria that can multiply rapidly at very high temperatures are called thermophiles. So in a simple way to eliminate coliform bacteria is the ordinary boiling of water.

Detection of pests in liquid

Before drinking tap water, make sure that it is clean. Very often running water is filled with pathogenic microorganisms. This is due to the poor condition of the water supply complexes.

If coliform bacteria are found in drinking water, such water should not be drunk or used. You need to clean it up first. If this is not done, then mass infection can occur, which in the worst case leads to death.

Many types of bacteria in water are very difficult to identify. Therefore, special laboratory chemical and biological methods are being developed. If we talk about the possibility of detecting coliforms through the color, taste or smell of water, then it is impossible to identify them this way.

Where do coliforms come from?

These pathogenic microorganisms live in the intestines of humans and animals. The reproduction of bacteria in water occurs after feces enter it. These excreta can enter the water supply through cesspools or stock channels. Coliforms can appear in wells after moving soil. On their own, a person cannot notice that the water is infected with bacteria. Therefore, if there is no filtration system and people use water from a well, then experts advise taking water and soil samples to avoid infection.

Disinfection methods

At each water supply station there is a stage of water disinfection. It is necessary for cleaning from harmful bacteria. Disinfection plants are the most widely used, they are fully automated. It is also possible to eliminate coliform bacteria manually, but this can lead to unpleasant consequences.

Industrial plants use a variety of chemicals to purify water. But it should be understood that such water is unsuitable for consumption. Ultraviolet light is used to disinfect drinking water, which is considered absolutely safe.

If you need to take a sample of water from a well on your own to determine whether it is clean or not, experts advise following certain rules:

• to take the liquid, sterile dishes are required;
• before starting the procedure, wash your hands well with soap;
• treat the tap with alcohol;
• deliver water to the laboratory for analysis no later than 2 hours after sampling.

Features of the vital activity of bacteria

Coliforms will be clearly visible in the meat broth. Here they can be very a large number of. But how much sediment is left cannot be determined with the naked eye. Usually the broth may just become a little cloudy. Microorganisms are gray in color, and coliforms are marked with a specific red tint. Bacteria that cannot tolerate lactose most often remain colorless. Therefore, it is almost impossible to determine the presence of bacteria by color.

Coliforms have specific biochemical parameters that do not allow milk to curdle, and gelatin will never dissolve in contaminated water.

Resistance of coliforms to various factors

Decontamination of coliforms or bacteria such as Escherichia coli is not difficult. They can die in 15 minutes if exposed to temperatures above 65 degrees. The stick can be eliminated in a 1% phenol solution.

Such microorganisms affect not only water, but also fruits, vegetables, household items. E. coli often appears with prolonged use of antibiotics. Coliforms can provoke the appearance of diseases such as typhoid and dysentery.

To avoid mass infection of people, you need to monitor what kind of water to use. Bacteria can be eliminated by physical and by chemical means. Chemicals are used to treat wastewater, after which they are re-disinfected by more gentle methods.

Most effective method water purification - the use of concentrated liquid oxygen. It quickly evaporates from the liquid, has a high cleaning quality. But liquid oxygen is too difficult to produce, and therefore this method of water purification is quite expensive.

The main sources of bacteria in the home

Public utilities are required to monitor the quality of tap water. But how can you avoid infection at home? You can get infected in several ways:

• cooler water. The risk of infection is quite high if the hands of the previous user were contaminated;
• for coliforms, rain collection is a favorable environment. Such a liquid is not recommended to be used even for irrigation;
• coliform bacteria and many other types of pathogens live in open sources. These do not include only sea water, so the risk of infection in this case will be minimal;
• microflora water pipes. Infection of tap water is quite often due to the poor condition of the pipes, on which plaque and rust form over time.

To avoid infection by contact or household contact, you just need to follow the basic rules of personal hygiene, wash your hands with soap and water. All drinking water should be from trusted sources. Before use, water must be boiled or passed through special filters.