What is coliform bacteria? Escherichia coli and other bacteria of this group as inhabitants of the planet “Man”

1. Review of literature sources

.1 Taxonomy of Escherichia coli

Scientific classification

Domain: Bacteria

Type: Proteobacteria

Class: Gammaproteobacteria

Order: Enterobacteriales

Family: Enterobacteriaceae

Genus: Escherichia

Species: Coli (Escherichia coli)

International scientific name

Escherichia coli (Migula 1895)

1.2 Structure and chemical composition of a bacterial cell

The internal organization of a bacterial cell is complex. Each systematic group of microorganisms has its own specific structural features.

The bacterial cell is covered with a dense membrane. This surface layer, located outside the cytoplasmic membrane, is called the cell wall. The wall performs protective and supporting functions, and also gives the cell a permanent, characteristic shape (for example, the shape of a rod or coccus) and represents the external skeleton of the cell. This dense shell makes bacteria similar to plant cells, which distinguishes them from animal cells, which have soft shells. Inside the bacterial cell, the osmotic pressure is several times, and sometimes tens of times, higher than in the external environment. Therefore, the cell would quickly rupture if it were not protected by such a dense, rigid structure as the cell wall.

The thickness of the cell wall is 0.01-0.04 microns. It makes up from 10 to 50% of the dry mass of bacteria. The amount of material that makes up the cell wall changes during bacterial growth and usually increases with age.

The main structural component of the walls, the basis of their rigid structure in almost all bacteria studied to date, is murein (glycopeptide, mucopeptide). This is an organic compound of a complex structure, which includes nitrogen-carrying sugars - amino sugars and 4-5 amino acids. Moreover, cell wall amino acids have an unusual shape (D-stereoisomers), which is rarely found in nature.

Using a staining method first proposed in 1884 by Christian Gram, bacteria can be divided into two groups: gram-positive and gram-negative .

Gram-positive organisms are able to bind some aniline dyes, such as crystal violet, and after treatment with iodine and then alcohol (or acetone) retain the iodine-dye complex. The same bacteria in which this complex is destroyed under the influence of ethyl alcohol (the cells become discolored) are classified as gram-negative.

The chemical composition of the cell walls of gram-positive and gram-negative bacteria is different. In gram-positive bacteria, the composition of the cell walls includes, in addition to mucopeptides, polysaccharides (complex, high-molecular sugars), teichoic acids (complex compounds in composition and structure, consisting of sugars, alcohols, amino acids and phosphoric acid). Polysaccharides and teichoic acids are associated with the wall framework - murein. We do not yet know what structure these components of the cell wall of gram-positive bacteria form. Using electronic photographs of thin sections (layering), no gram-positive bacteria were detected in the walls. Probably all these substances are very tightly interconnected.

The walls of gram-negative cells contain a significant amount of lipids (fats) associated with proteins and sugars in complex complexes - lipoproteins and lipopolysaccharides. There is generally less murein in the cell walls of gram-negative bacteria than in gram-positive bacteria. The wall structure of gram-negative bacteria is also more complex. Using an electron microscope, it was found that the walls of these bacteria are multilayered.

The inner layer consists of murein. Above it is a wider layer of loosely packed protein molecules. This layer is in turn covered with a layer of lipopolysaccharide. The topmost layer consists of lipoproteins.

The cell wall is permeable: through it, nutrients freely pass into the cell, and metabolic products exit into the environment. Large molecules with high molecular weight do not pass through the shell.

The cell wall of many bacteria is surrounded on top by a layer of mucous material - a capsule. The thickness of the capsule can be many times greater than the diameter of the cell itself, and sometimes it is so thin that it can only be seen through an electron microscope - a microcapsule.

The capsule is not an essential part of the cell; it is formed depending on the conditions in which the bacteria find themselves. It serves as a protective cover for the cell and participates in water metabolism, protecting the cell from drying out.

The chemical composition of capsules is most often polysaccharides. Sometimes they consist of glycoproteins (complex complexes of sugars and proteins) and polypeptides (genus Bacillus), in rare cases - of fiber (genus Acetobacter).

Mucous substances secreted into the substrate by some bacteria cause, for example, the mucous-stringy consistency of spoiled milk and beer.

The entire contents of a cell, with the exception of the nucleus and cell wall, are called cytoplasm. The liquid, structureless phase of the cytoplasm (matrix) contains ribosomes, membrane systems, mitochondria, plastids and other structures, as well as reserve nutrients. The cytoplasm has an extremely complex, fine structure (layered, granular). Using an electron microscope, many interesting details of the cell structure have been revealed.

The outer lipoprotein layer of the bacterial protoplast, which has special physical and chemical properties, is called the cytoplasmic membrane.

Inside the cytoplasm are all vital structures and organelles.

The cytoplasmic membrane plays a very important role - it regulates the entry of substances into the cell and the release of metabolic products to the outside.

Through the membrane, nutrients can enter the cell as a result of an active biochemical process involving enzymes. In addition, the synthesis of some cell components occurs in the membrane, mainly components of the cell wall and capsule. Finally, the cytoplasmic membrane contains the most important enzymes (biological catalysts). The ordered arrangement of enzymes on membranes makes it possible to regulate their activity and prevent the destruction of some enzymes by others. Associated with the membrane are ribosomes - structural particles on which protein is synthesized. The membrane consists of lipoproteins. It is strong enough and can ensure the temporary existence of a cell without a shell. The cytoplasmic membrane makes up up to 20% of the dry mass of the cell.

In electronic photographs of thin sections of bacteria, the cytoplasmic membrane appears as a continuous strand about 75A thick, consisting of a light layer (lipids) sandwiched between two darker ones (proteins). Each layer has a width of 20-30A. Such a membrane is called elementary.

Between the plasma membrane and the cell wall there is a connection in the form of desmoses - bridges. The cytoplasmic membrane often gives rise to invaginations - invaginations into the cell. These invaginations form special membrane structures in the cytoplasm called mesosomes. Some types of mesosomes are bodies separated from the cytoplasm by their own membrane. Numerous vesicles and tubules are packed inside these membrane sacs. These structures perform a variety of functions in bacteria. Some of these structures are analogues of mitochondria. Others perform the functions of the endoplasmic reticulum or Golgi apparatus. By invagination of the cytoplasmic membrane, the photosynthetic apparatus of bacteria is also formed. After invagination of the cytoplasm, the membrane continues to grow and forms stacks, which, by analogy with plant chloroplast granules, are called thylakoid stacks. In these membranes, which often fill most of the cytoplasm of the bacterial cell, pigments (bacteriochlorophyll, carotenoids) and enzymes (cytochromes) that carry out the process of photosynthesis are localized.

The cytoplasm of bacteria contains ribosomes - protein-synthesizing particles with a diameter of 200A. There are more than a thousand of them in a cage. Ribosomes consist of RNA and protein. In bacteria, many ribosomes are freely located in the cytoplasm, some of them may be associated with membranes.

The cytoplasm of bacterial cells often contains granules of various shapes and sizes. However, their presence cannot be considered as some kind of permanent sign of a microorganism; it is usually largely related to the physical and chemical conditions of the environment. Many cytoplasmic inclusions are composed of compounds that serve as a source of energy and carbon. These reserve substances are formed when the body is supplied with sufficient nutrients, and, conversely, are used when the body finds itself in conditions that are less favorable in terms of nutrition.

In many bacteria, granules consist of starch or other polysaccharides - glycogen and granulosa. Some bacteria, when grown in a sugar-rich medium, have droplets of fat inside the cell. Another widespread type of granular inclusions is volutin (metachromatin granules). These granules consist of polymetaphosphate (a reserve substance containing phosphoric acid residues). Polymetaphosphate serves as a source of phosphate groups and energy for the body. Bacteria are more likely to accumulate volutin under unusual nutritional conditions, such as sulfur-free media. In the cytoplasm of some sulfur bacteria there are droplets of sulfur.

In addition to various structural components, the cytoplasm consists of a liquid part - the soluble fraction. It contains proteins, various enzymes, t-RNA, some pigments and low molecular weight compounds - sugars, amino acids.

As a result of the presence of low molecular weight compounds in the cytoplasm, a difference arises in the osmotic pressure of the cellular contents and the external environment, and this pressure may be different for different microorganisms. The highest osmotic pressure is observed in gram-positive bacteria - 30 atm; in gram-negative bacteria it is much lower than 4-8 atm.

The nuclear substance, deoxyribonucleic acid (DNA), is localized in the central part of the cell.

Bacteria do not have such a nucleus as higher organisms (eukaryotes), but have its analogue - the “nuclear equivalent” - the nucleoid , which is an evolutionarily more primitive form of organization of nuclear matter. Microorganisms that do not have a real nucleus, but have an analogue of it, are classified as prokaryotes. All bacteria are prokaryotes. In the cells of most bacteria, the bulk of DNA is concentrated in one or several places. In bacteria, DNA is packed less tightly, unlike true nuclei; A nucleoid does not have a membrane, a nucleolus, or a set of chromosomes. Bacterial DNA is not associated with the main proteins - histones - and is located in the nucleoid in the form of a bundle of fibrils.

Some bacteria have appendage structures on the surface; The most widespread of them are flagella - the organs of movement of bacteria.

The flagellum is anchored under the cytoplasmic membrane using two pairs of discs. Bacteria may have one, two, or many flagella. Their location is different: at one end of the cell, at two, across the entire surface. Bacterial flagella have a diameter of 0.01-0.03 microns, their length can be many times greater than the length of the cell. Bacterial flagella consist of a protein - flagellin - and are twisted helical filaments.

1.3 Morphology of Escherichia coli and its representatives

coli microflora

Escherichia coli is a polymorphic facultative anaerobic short (length 1-3 µm, width 0.5-0.8 µm) gram-negative rod with a rounded end. Strains in smears are arranged randomly, without forming spores and peritrich. Some strains have a microcapsule and pili, and are widely found in the lower intestines of warm-blooded organisms. Most strains of E. coli are harmless, but serotype O157:H7 can cause severe food poisoning in humans.

Bacteria of the coli group grow well on simple nutrient media: meat-peptone broth (MPB), meat-peptone agar (MPA). On Endo medium they form flat red colonies of medium size. Red colonies may have a dark metallic sheen (E. coli) or no sheen (E. aerogenes).

They have high enzymatic activity towards lactose, glucose and other sugars, as well as alcohols. They do not have oxidase activity. Based on their ability to break down lactose at a temperature of 37°C, bacteria are divided into lactose-negative and lactose-positive Escherichia coli (LKP), or coliform, which are formed according to international standards. From the LCP group, fecal coliforms (FEC) are isolated, capable of fermenting lactose at a temperature of 44.5 ° C. coli do not always live only in the gastrointestinal tract; their ability to survive for some time in the environment makes them an important indicator for testing samples for the presence of fecal contamination.

Common coliform bacteria (TCB) are gram-negative, non-spore-forming rods capable of growing on differential lactose media, fermenting lactose to acid, aldehyde and gas at a temperature of 37 +/- 1°C for 24 - 48 hours.

Coliform bacteria (coliforms) are a group of gram-negative rods that primarily live and reproduce in the lower digestive tract of humans and most warm-blooded animals (such as livestock and waterfowl). Vvoda are usually found in fecal waste and are able to survive in it for several weeks, although (in the vast majority) they do not reproduce.

Thermotolerant coliform bacteria play an important role in assessing the effectiveness of water treatment from fecal bacteria. A more accurate indicator is E. coli (Escherichia coli), since the source of some other thermotolerant coliforms can be not only fecal water. At the same time, the total concentration of thermotolerant coliforms is in most cases directly proportional to the concentration of E. coli, and their secondary growth in the distribution network is unlikely (unless there are sufficient nutrients in the water, at temperatures above 13 ° C.

Thermotolerant coliform bacteria (TCB) - are among the common coliform bacteria, have all their characteristics and, in addition, are able to ferment lactose to acid, aldehyde and gas at a temperature of 44 +/- 0.5 ° C for 24 hours.

Includes the genus Escherichia and, to a lesser extent, individual strains of Citrobacter, Enterobacter and Klebsiella. Of these organisms, only E. coli is specifically of fecal origin, and it is always present in large quantities in human and animal excrement and is rarely found in water and soil that have not been subject to fecal contamination. It is believed that the detection and identification of E. coli provides sufficient information to establish the fecal nature of the contamination.

Coliforms are found in large quantities in domestic wastewater, as well as in surface runoff from livestock farms. In water sources used for centralized drinking and domestic water supply, the number of common coliforms is allowed to be no more than 1000 units (CFU/100 ml, CFU - colony-forming units), and thermotolerant coliforms - no more than 100 units. In drinking water, coliforms should not be detected in a 100 ml sample. Incidental introduction of coliform organisms into the distribution system is acceptable in no more than 5% of samples collected during any 12-month period, provided that E. coli is absent.

The presence of coliform organisms in water indicates insufficient treatment, secondary pollution, or the presence of excess nutrients in the water.

2. Materials and research methods

When examining relatively microbially clean water for the presence of pathogenic microorganisms, it is necessary to concentrate the desired microflora, which is contained in negligible quantities in the water. Detection of pathogens of intestinal infections in water from open reservoirs and wastewater against the background of a predominant mass of saprophytic microflora is most effective when the desired bacteria are concentrated in accumulation environments that inhibit the growth of accompanying microflora. Consequently, when analyzing water that has varying degrees of general microbial contamination, certain methods for isolating pathogenic microflora are used.

Open waters are usually characterized by a significant content of suspended solids, i.e. turbidity, often color, low salt content, relatively low hardness, the presence of a large amount of organic matter, relatively high oxidability and significant bacterial content . Seasonal fluctuations in river water quality are often quite sharp. During floods, the turbidity and bacterial contamination of water greatly increases, but its hardness (alkalinity and salinity) usually decreases. Seasonal changes in water quality significantly affect the nature of the operation of water treatment facilities during certain periods of the year.

The number of microbes in 1 ml of water depends on the presence of nutrients in it. The more polluted the water is with organic residues, the more microbes it contains. Open reservoirs and rivers are especially rich in microbes. The largest number of microbes in them is located in the surface layers (in a layer 10 cm from the surface of the water) of coastal zones. With distance from the shore and increasing depth, the number of microbes decreases.

River silt is richer in microbes than river water. There are so many bacteria in the very surface layer of sludge that a film forms from them. This film contains many filamentous sulfur bacteria and iron bacteria; they oxidize hydrogen sulfide to sulfuric acid and thereby prevent the inhibitory effect of hydrogen sulfide (fish death is prevented).

Rivers in urban areas are often natural recipients of wastewater from household and fecal waste, so the number of microbes increases sharply within populated areas. But as the river moves away from the city, the number of microbes gradually decreases, and after 3-4 tens of kilometers it again approaches its original value. This self-purification of water depends on a number of factors: mechanical sedimentation of microbial bodies; reduction in water nutrients digestible by microbes; exposure to direct rays of the sun; devouring bacteria by protozoa, etc.

Pathogens can enter rivers and reservoirs with wastewater. Brucellosis bacillus, tularemia bacillus, polio virus, foot-and-mouth disease virus, as well as pathogens of intestinal infections - typhoid bacillus, paratyphoid bacillus, dysentery bacillus, Vibrio cholerae - can persist in water for a long time, and water can become a source of infectious diseases. It is especially dangerous for pathogenic microbes to get into the water supply network, which happens when it malfunctions. Therefore, sanitary biological control has been established over the condition of reservoirs and the tap water supplied from them.

2.1 Hydrometric float method for measuring and determining water flow speed

To measure and determine the speed of water flow, there is a float method, which is based on tracking the movement of an object lowered into the flow (float) using instruments or the naked eye. Floats are thrown into the water on small rivers from the shore or from a boat. Using a stopwatch, the time and passage of the float between two adjacent targets, the distance between which is known, is determined. The surface speed of the current is equal to the speed of the float. By dividing the distance traveled by the float by the observation time, the flow velocity is obtained.

2.2 Water collection, storage and transportation of samples

Water samples for bacteriological analysis are taken in compliance with the rules of sterility: in sterile bottles or with sterile devices - bottlemeters in an amount of 1 liter.

The so-called bottle bottle meter is convenient for collecting water from open reservoirs, wastewater, and water from swimming pools and wells.

Guidelines for detecting pathogens of intestinal bacterial infections in water.

When taking water samples from open reservoirs, the following points should be provided: at the point of stagnation and at the place of the fastest flow (from the surface and at a depth of 50 - 100 cm).

Bottle bottle meter. Bathometers are devices of various designs for taking water samples from different depths. In their classic form, these are cylinders that can be lowered to a certain depth, then closed and removed. Making a classic bathometer yourself is not easy. But instead, you can use a simple glass or plastic bottle with a narrow neck, weighted with some kind of weight and plugged with a cork, ideally a cork one. Ropes are tied to the neck of the bottle and to the cork. Having lowered the bottle to the desired depth (the main thing is that it sinks, that’s what the load is for), you need to pull out the cap - so you shouldn’t plug it tightly. After giving the bottle time to fill at the desired depth (1-2 minutes), it is pulled to the surface. This should be done as energetically as possible - with a high speed of rise and a narrow neck, water from the overlying layers will practically not get inside.
Samples brought to the surface using a bathometer should also be "thickened" using a plankton net, and then the volume of strained water should be calculated. Since this volume should be as large as possible, the bottlemeter should be made as large as possible, for example, use a 2-liter glass or plastic bottle or some other large vessel with a narrow neck. Marks should also be made every meter on the rope to which the bottle is tied to determine the sampling depth.

The first control point at the dam (beginning of the beach) is the fence point (TZ1).

The second control point at the boat station (end of the beach) is the pick-up point (TZ2).

T31-first control point at the dam (beginning of the beach) T32-second control point at the boat station (end of the beach)

2.3 Sample storage and transportation

Sample examination in the laboratory must begin as soon as possible from the moment of collection.

The analysis should be carried out within 2 hours after collection.

If the sample delivery time and storage temperature cannot be met, the sample should not be analyzed.

2.4 Preparation of glassware for analysis

Laboratory glassware must be thoroughly washed, rinsed with distilled water until detergents and other foreign impurities are completely removed, and dried.

Test tubes, flasks, bottles, and vials must be sealed with silicone or cotton-gauze stoppers and packaged in such a way as to prevent contamination after sterilization during operation and storage. Caps can be metal, silicone, foil or thick paper.

New rubber stoppers are boiled in a 2% sodium bicarbonate solution for 30 minutes and washed 5 times with tap water (boiling and washing are repeated twice). Then the corks are boiled in distilled water for 30 minutes, dried, wrapped in paper or foil and sterilized in a steam sterilizer. Previously used rubber stoppers are disinfected, boiled for 30 minutes in tap water with a neutral detergent, washed in tap water, dried, mounted and sterilized.

Pipettes with inserted cotton swabs should be placed in metal cases or wrapped in paper.

When closed, Petri dishes should be placed in metal cases or wrapped in paper.

The prepared dishes are sterilized in a dry-heat oven at 160-170°C for 1 hour, counting from the moment the specified temperature is reached. Sterilized dishes can only be removed from the drying cabinet after it has cooled below 60 °C.

After the analysis, all used dishes and tubes are disinfected in an autoclave at (126±2)°C for 60 minutes. Pipettes are disinfected by boiling in a 2% NaHC03 solution.

After cooling, the remaining media are removed, then the dishes and test tubes are soaked, boiled in tap water and washed, followed by rinsing with distilled water.

Pre-prepared nutrient agar ENDO is poured into Petri dishes and left to harden.

2.5 Membrane filter method

Method for determining the number of E. coli cells per unit volume of liquid (coli index); The essence of the method is to filter the analyzed liquid through membrane filters that retain bacteria, after which these filters are placed on a solid nutrient medium and the bacterial colonies grown on it are counted.

Preparation of membrane filters

Membrane filters must be prepared for analysis in accordance with the manufacturer's instructions.

Preparing the filter apparatus

The filter apparatus is wiped with a cotton swab moistened with alcohol and flambéed. After cooling, a sterile membrane filter is placed on the lower part of the filter apparatus (table) with flambéed tweezers, pressed with the upper part of the device (glass, funnel) and secured with a device provided for in the design of the device.

With the membrane filter method, a certain amount of water is passed through a special membrane with a pore size of about 0.45 microns.

As a result, all bacteria in the water remain on the surface of the membrane. After which the membrane with bacteria is placed on a special nutrient medium (ENDO). After which the Petri dishes were turned over and placed in a thermostat for a certain time and temperature. Total coliform bacteria (TCB) - incubated at a temperature of 37 +/- 1°C for 24-48 hours. To determine thermotolerant bacteria, inoculation is carried out in a medium preheated to a temperature of 44°C and incubated at the same temperature for 24 hours.

The medium is photosensitive. Therefore, all seeded cups are protected from light.

During this period, called incubation, bacteria are able to multiply and form clearly visible colonies that can be easily counted.

At the end of the incubation period, the crops are examined:

a) the absence of microbial growth on the filters or the detection of colonies on them that are not characteristic of intestinal bacteria (spongy, filmy with an uneven surface and edge), allows the research to be completed at this stage of the analysis (18-24 hours) with a negative result for the presence of intestinal bacteria sticks in the analyzed volume of water;

b) if colonies characteristic of E. coli are detected on the filter (dark red with or without a metallic sheen, pink and transparent), the study is continued and microscopically examined.

If the growth of round colonies is crimson in color with a metallic sheen with a diameter of 2.0-3.0 mm - Escherichia coli 3912/41 (055:K59);

If the growth of round colonies of crimson color with a diameter of 1.5-2.5 mm with a fuzzy metallic sheen - Escherichia coli 168/59 (O111:K58)

2.6 Accounting for results

After an incubation period of 48 hours for common coliform bacteria and 24 hours for thermotalerant bacteria, the colonies grown on the plates are counted.

Colonies growing on the surface, as well as in the depths of the agar, were counted using a magnifying glass with fivefold magnification or a special device with a magnifying glass. To do this, the cup is placed upside down on a black background and each colony is marked from the bottom with ink or glass ink.

To confirm the presence of OKB, the following is examined:

all colonies, if less than 5 colonies grew on the filters;

at least 3 - 4 colonies of each type.

To confirm the presence of TSD, all typical colonies are examined, but not more than 10.

The number of colonies of each type is counted.

Calculation and presentation of results.

The result of the analysis is expressed as the number of colony forming units (CFU) of total coliform bacteria in 100 ml of water. To calculate the result, the number of colonies confirmed as total coliform bacteria grown on all filters is summed up and divided by 3.

Since this method of water analysis only involves determining the total number of colonies - forming bacteria of different types, its results cannot clearly judge the presence of pathogenic microbes in the water. However, a high microbial count indicates general bacteriological contamination of the water and a high probability of the presence of pathogenic organisms.

Each selected isolated colony is examined for Gram origin.

Gram stain

Gram staining is of great importance in the taxonomy of bacteria, as well as for the microbiological diagnosis of infectious diseases. A feature of the Gram stain is the unequal attitude of various microorganisms to dyes of the triphenylmethane group: gentian, methyl or crystal violet. Microorganisms belonging to the group of gram-positive Gram (+), for example staphylococci, streptococci, give a strong connection with the indicated dyes and iodine. Stained microorganisms do not become discolored when exposed to alcohol, as a result of which, with additional staining with Gram fuchsin (+), the microorganisms do not change their initially purple color. Gram-negative Gram (−) microorganisms (bacteroides, fusobacteria, etc.) form with crystalline gentian or methylene violet and iodine a compound that is easily destroyed by alcohol, as a result of which they become discolored and then stained with fuchsin, acquiring a red color.

Reagents: carbolic solution of gentian violet or crystal violet, aqueous solution of Lugol, 96% ethyl alcohol, aqueous-alcoholic solution of fuchsin.

Coloring technique. A piece of filter paper is placed on the fixed smear and a carbolic solution of gentian violet is poured onto it for 1/2 to 1 minute. Drain the dye and, without rinsing, pour in Lugol's solution for 1 minute. Drain the Lugol's solution and rinse the preparation in 96% alcohol for 1/2 to 1 minute until the dye stops coming off. Wash with water. Additionally, stain with diluted fuchsin for 1/2 to 1 minute. Drain off the dye, wash and dry the preparation.

3. Research results

.1 Microbiological analysis of Pechersk Lake water (using the exampleE. coli) during the spring period (May) of the study 2009-2013.

As a result of three-time water sampling at two sampling points (TZ1 - at the beginning of the beach, near the dam, TZ2 - end of the beach, boat station), we calculated the average indicators of OKB and TKB, the results of which are presented in Table 3.1.

Table 3.1. Average indicators of OKB and TKB in the water of Pechersk Lake for May 2013.

The indicator of the content of E. coli bacteria according to the OKB at the beginning and at the end of May in TZ1 (near the dam) does not differ, amounting to 195 CFU/cm3, which is 3.3 times less compared to the water sample taken in TZ2 (at the boat station ) at the beginning of May and 4.3 times more at the end of May.

A study of the dynamics of the content of E. coli in the water of Lake Pechersk in May 2013 according to the SES confirmed the correctness of our own research and showed that the TBC indicator in TZ2 is 3.4 times higher than in TZ1 (according to our own results, 3.3 times higher).

Study of changes in OKB and TKB indicators for the month of May from 2009 to 2013. showed a wide variation in indicators, which is clearly presented in Figures 3.1 - 3.2

Analysis of data from the health care institution “Mogilev Zonal Center for Hygiene and Epidemiology” for the beginning of May 2008-2013.

At the end of the analysis of data for the beginning of May 2008-2013, we found that in 2008 and 2012 there were more OKB in TZ1 than in TZ2.

Analysis of data from the health care institution “Mogilev Zonal Center for Hygiene and Epidemiology” for the end of May 2008-2013.

According to SanPiN, common coliform bacteria should be absent in 100 ml of drinking water

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

For open reservoirs, according to the OKB, no more than 500 CFU per 100 ml of water, according to the TKB, no more than 100 CFU per 100 ml of water.

The presence of E. coli in the water confirms the fecal nature of the contamination.

According to the results of measurements, during the summer low-water period, coliform bacteria are present in small quantities, usually from one hundred to several hundred units, and only during periods of floods they briefly increase to 1000 or more units.

Low values in summer may be due to several factors:

) intense solar radiation, which is harmful to bacteria;

) increased pH values in summer (usually pH > 8 in summer, winter< 8) за счет развития фитопланктона;

) release of phytoplankton metabolites into the water, inhibiting bacterial flora.

With the beginning of the autumn-winter season, these factors are significantly weakened, and the number of bacteria increases to a level of several thousand units. The greatest extremes occur during periods of snow melting, especially during floods, when meltwater washes away bacteria from the surface of the catchment area.

The total number of colony-forming bacteria in mid-summer is lower than in the spring-autumn period, which is associated with intense solar radiation, which is detrimental to bacteria.

The largest number of microbes in open water bodies is found in the surface layers (in a layer 10 cm from the surface of the water) of coastal zones. With distance from the shore and increasing depth, the number of microbes decreases.

Conclusion

coli pathogen bacteria

To find and identify E. coli, a microbiological analysis of samples was carried out for the beginning of May 2013. A statistical analysis of data from the health care institution “Mogilev Zonal Center for Hygiene and Epidemiology” for the beginning of May 2008-2012 was also carried out.

At the end of the analysis, it was found that the number of coliform bacteria we calculated did not exceed the permissible limit.

At the end of the statistical analysis of data from the health care institution “Mogilev Zonal Center for Hygiene and Epidemiology” for 2008-2012, it was found that during the summer low water coliform bacteria are present in small quantities. The total number of colony-forming bacteria in mid-summer is lower than in the spring-autumn period, due to intense solar radiation, which is detrimental to bacteria, and with the beginning of the autumn-winter season the number of bacteria increases to a level of several thousand units. The greatest extremes occur during periods of snow melting, especially during floods, when meltwater washes away bacteria from the surface of the catchment area.

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From the remains of human activity. This microorganism is a permanent inhabitant of the large intestine of humans and animals. In addition to E. coli, the group of intestinal bacteria includes epiphytic and phytopathogenic species, as well as species whose etiology (origin) has not yet been established. The bacteria of the E. coli group include the genera Escherichia (a typical representative of E. coli), Citrobacter (a typical representative of Citr. coli citrovorum), Enterobacter (a typical representative of Ent. aerogenes), which are combined into one family Enterobacteriaceae due to the common morphological and cultural properties. They are characterized by different enzymatic properties and antigenic structure.

Morphology

Bacteria of the coli group are short (length 1-3 µm, width 0.5-0.8 µm) polymorphic motile and immobile gram-negative rods that do not form spores.

Cultural properties.

E. coli colonies on solid nutrient medium

Bacteria grow well on simple nutrient media: meat-peptone broth (MPB), meat-peptone agar (MPA). On MPB they produce abundant growth with significant turbidity of the medium; the sediment is small, grayish in color, easily broken. They form a wall ring; there is usually no film on the surface of the broth. On MPA, colonies are transparent with a grayish-blue tint, easily merging with each other. On Endo medium they form flat red colonies of medium size. Red colonies may have a dark metallic sheen (E. coli) or no sheen (E. aerogenes). Lactose-negative variants of Escherichia coli (B.paracoli) are characterized by colorless colonies. They are characterized by wide adaptive variability, as a result of which various variants arise, which complicates their classification.

Biochemical properties

Most coliform bacteria (coliforms) do not liquefy gelatin, coagulate milk, break down peptones to form amines, ammonia, hydrogen sulfide, and have high enzymatic activity towards lactose, glucose and other sugars, as well as alcohols. They do not have oxidase activity. Based on their ability to break down lactose at a temperature of 37°C, coliforms are divided into lactose-negative and lactose-positive Escherichia coli (LKP), or coliform, which are formed according to international standards. From the LCP group are fecal coliforms (FEC), which are capable of fermenting lactose at a temperature of 44.5°C. These include E. coli, which does not grow on citrate medium.

Sustainability

Sources

R.P. Kornelaeva, PP. Stepanenko, E.V. Pavlova Sanitary microbiology of raw materials and products of animal origin. 2006, p.15-18

Model organisms in biological research

Bacteriophage · Escherichia coli ( E. coli ) chlamydomonas ( C. reinhardtii) · tetrahymena ( T. thermophila) · budding yeast ( S. cerevisiae) · fission yeast ( S. pombe) Neurospora ( N. crassa) · corn ( Z. mays) · alfalfa ( M. truncatula) Arabidopsis ( A. thaliana) · nematode ( C. elegans) · fruit fly ( D. melanogaster) · zebrafish ( D. rerio) · frog ( X. laevis) · rat ( R. norvegicus) · mouse ( M. musculus)

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See what “Escherichia coli bacteria” are in other dictionaries:

coli bacteria- 3.2 coliform bacteria; Coliforms, if forms: Microorganisms of the enterobacteria family of the genera Escherichia, Citrobacter, Enterobacter, Klebsiella, Serratia; sporeless, gram-negative, aerobic and facultative anaerobic rods,... ...

Under the name of bacteria in science, the smallest, microscopic-sized organisms belonging to the plant kingdom are known. In terms of their organization and their morphological characteristics, B. are closest to the so-called cyan or... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

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

Escherichia coli Photo of Escherichia coli via SEM Scientific classification Kingdom: Bacteria ... Wikipedia

TIMATS A set of tests for differentiating individual genera of bacteria from the group of coliforms T temperature test (Eijkman test); And indole formation test; M reaction with methyl red; And the reaction to acetylmethylcarbinol (reaction... Wikipedia

GOST R 53430-2009: Milk and milk processing products. Microbiological analysis methods- Terminology GOST R 53430 2009: Milk and milk processing products. Methods of microbiological analysis original document: 3.2 coliform bacteria; Coliforms, if forms: Microorganisms of the family of enterobacteria of the genus Escherichia,... ... Dictionary-reference book of terms of normative and technical documentation

Vologda butter is unsalted sweet cream butter with a moisture mass fraction of no more than 16.0%, produced in the Vologda region, a well-known good... Wikipedia

coliform- large group of Escherichia coli coliform bacteria of the coliform group

Coliform bacteria Coliform bacteria

gram-asporogenic oxidase-negative enterobacteria, growing on Endo medium and fermenting lactose with the formation of lactose and gas at 37°C for 48 hours. K.b. are standardized according to international standards as an indicator of fecal contamination of K. b. together with similar bacteria, but fermenting glucose with the formation of acid and gas during the day, they form a group of Escherichia coli, which is standardized as an indicator of fecal contamination.

(Source: Dictionary 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 using a standard test. Source: GOST R 52426 2005: Drinking water...

Coliform bacteria are thermotolerant- bacteria that have all the characteristics 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 matter that has recently entered the water... ... Official terminology

Common coliform bacteria- 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 a temperature of 37 °C for 24-48 hours. Note... Technical Translator's Guide

Escherichia coli (Latin: Escherichia coli) is a microorganism discovered in 1885 by Escherich from the remains of human activity. This microorganism is a permanent inhabitant of the large intestine of humans and animals. In addition to E. coli, the group... ... 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-stable coliform bacteria that ferment lactose or mannitol at... ... 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

A topic dedicated to those from whom we disinfect water (see the article “Legionnaires’ disease (legionellosis)”). But there are many more bacteria that live in water and from which you need to protect yourself using, for example, ultrafiltration. Therefore, our topic today is bacteria in our water. Where we will tell you a little about what bacteria should not live in our water.

Bacteria in our water is an undesirable phenomenon for a number of reasons, which we will discuss below. Bacteria in general are determined by microbiological analysis of water, and are expressed as a total microbial count with a unit of measurement " colony forming units", k.o.e. (or k.u.o in Ukrainian, colony forming units - CFU in English).

The total microbial count reflects the overall level of bacteria in the water, and not just those of them that form colonies visible to the naked eye on nutrient media under certain cultivation conditions.

Bacteria as a whole, expressed by the total microbial number, includes several groups and subgroups of bacteria. This:

Coliform bacteria (including thermotolerant ones).
Sulfite-reducing clostridia.

A few words about clostridium. Clostridia is a kind of standard. They are very tenacious, or if scientifically speaking, resistant to disinfection, which makes them a kind of indicator - there are no clustridia, and there are no other, even more dangerous microorganisms.

And finally, let's pay attention to the most common indicator - coliform bacteria as one of the stumbling blocks in microbiological analysis of water.

The stumbling block, by the way, is that it is often believed that these are pathogenic bacteria, and if you take a sip of such water, dysentery or cholera begins almost immediately. But this is not entirely true for coliform bacteria. According to the dictionary definition,

Coliform bacteria are bacteria of the Escherichia coli group (coliforms, also called coliform and coliform bacteria) - a group of bacteria of the enterobacteria family, conditionally distinguished by morphological and cultural characteristics, used by sanitary microbiology as a marker of fecal contamination

In normal language, this means that all bacteria that are somewhat similar to the bacterium “Escherichia coli” (Escherichia coli, named after Theodor Escherich; abbreviated as E.coli) are combined into one group called “coliform bacteria”, that is, bacteria , similar to "E.coli". In addition, coliform organisms are convenient microbial indicators of drinking water quality and have been used as such for many years. This is due, first of all, to the fact that they are easy to detect and quantify.

The term "Coliform organisms" (or "coliform bacteria") refers to a class of gram-negative, rod-shaped bacteria that primarily live and reproduce in the lower digestive tract of humans and most warm-blooded animals (such as livestock and waterfowl). Consequently, they usually enter water with fecal waste and are able to survive in it for several weeks, although they are (in the vast majority) deprived of the ability to reproduce.

Accordingly, if these bacteria are found in drinking water, this means that there is a possibility of water contamination by wastewater.
And secondly, if among coliform bacteria there are virulent strains (pathogenic varieties) of bacteria, then diseases may also occur.

In addition, another group is often identified among coliform bacteria - thermotolerant coliform bacteria. These are bacteria that are similar to “Escherichia coli”, and are capable of digesting food at higher temperatures (44 - 45 o C) and include the genus Escherichia itself (better known as E. Coli) and some others.

Thermotolerant coliforms are classified as a separate subgroup in microbiological analysis because they indicate recent fecal contamination. Plus, they're relatively easy to identify—so why not include them in your analysis?

Be that as it may, any increased level of bacteria in the water is an alarming sign, and when it appears, you need to do something with the water (for example, start using).

So, we have made a general theoretical overview of the bacteria in our water, and we can move on to practice.

Sometimes the following situation arises: someone wants to conduct a microbiological analysis of water. He takes a water sample, takes it to the sanitary and epidemiological station, and there... Thousands and thousands of bacteria. The problem is that this does not mean that these bacteria were in the source water. In fact, there are three options for their appearance in a water sample:

bacteria are actually present in the water;
entered during the installation of equipment and pipelines;
there was improper sampling for microbiology.

In order to exclude the third reason for the excess amount of bacteria in water, you need to correctly take a water sample. Accordingly, we bring to your attention important rules for proper sampling water for microbiological analysis. Yes, you need:

Use only bottles that have been previously disinfected in an autoclave.
Wash your hands with soap before taking a sample.
The spout of the tap from which the samples will be taken must be wiped with alcohol or burned with a flame from a lighter or match.
Take the bottle filled to the top with water to the laboratory as quickly as possible (for example, within two hours).

Therefore, we can conclude: bacteria should not be in the water, not only because they can lead to disease, but also because they are an indicator of water contamination by byproducts (for example, too much organic matter, fecal water, etc.). In other words, these data are of little value for the detection of fecal contamination and should not be considered an important indicator in assessing the safety of drinking water supplies, although a sudden increase in the number of colonies in the analysis of water from a groundwater source may be an early signal of aquifer contamination.

Accordingly, bacteria in our water is not what should be there :)

Bacteria of the Escherichia coli group (coliforms) are a group of bacteria from the family Enterobacteriaceae, conditionally distinguished by morphological and cultural characteristics, used by sanitary microbiology as a marker of fecal contamination; they belong to the group of so-called sanitary indicator microorganisms.

Bacteria of the E. coli group include representatives of the genera Escherichia (including E. coli), Citrobacter (a typical representative of C. coli citrovorum), Enterobacter (a typical representative of E. aerogenes), which are combined into one family Enterobacteriaceae due to the common morphological and cultural properties . They are characterized by different enzymatic properties and antigenic structure.

4. The presence of what bacteria indicates fresh fecal contamination of water?

These bacteria include thermotolerant coliform bacteria, fecal coliforms, which ferment lactose to acid and gas at a temperature of 44°C for 24 hours and do not grow on a nitrate medium.

The detection of enterococcus also indicates fresh fecal contamination.

There is a known method for determining fresh fecal contamination, which consists in isolating enterococci from the test water, and when the index of these microorganisms is over 500, the arrival of fresh fecal contamination is assumed.

5. What indicators are determined during sanitary-microbiological testing of water?

1. Determination of the number of saprophytic microorganisms.

2 . Determination of the number of lactose-positive Escherichia coli.

3 . Determination of the number of Escherichia coli.

4. Determination of the number of enterococci.

5 . Determination of the number of staphylococci.

6 . Determination of the number of PFU of E. coli phages.

7 . Determination of bacteria of the genera Salmonella and Shigella.

8 . Determination of the presence of intestinal viruses.

9 . Definition of Vibrio cholerae.

6. What is a “germ number” and how is it determined?

Microbial number is a quantitative indicator of bacterial contamination of the environment, one of the laboratory sanitary and hygienic indicators, indicating the “total number of microbes” in 1 ml of water, 1 g of solid product or soil, 1 m 3 of air, grown at MPA at 37 ° C in 48 hours

To determine the microbial number, inoculations are done in compliance with the rules of asepsis into Petri dishes with MPA using the pouring method so that from 30 to 300 colonies grow on the dishes.

7. What method is used to detect coliforms in water?

There are two methods for determining the number of coliform bacteria: fermentation and membrane filters.

The essence of the membrane filter method is to concentrate bacteria from a certain volume of test water on a membrane filter and grow them at a temperature of 37 ± 0.5 ° C in Endo medium. This temperature creates optimal conditions for growing bacteria.

8. For what purposes are the Koch and Krotov methods used?

The Koch and Krotov methods are used for sanitary and microbiological examination of air.

9. Name the sanitary indicator microorganisms, by the presence of which in the air one can assess its purity?

Sanitary indicator microorganisms for air are Staphylococcus aureus and hemolytic streptococci (Staphylococcus aureus, group Streptococcus viridans and Streptococcus haemolyticus).

10. What is the aspiration method and for what purpose is it used?

The aspiration method is based on the forced settling of microorganisms onto the surface of a dense nutrient medium or into a trapping liquid. For this purpose, the Krotov apparatus, the Rechmensky bacteria trap, the POV-1 device, etc. are used.

To determine the total number of bacteria, two samples of 100 liters each are taken. The crops are incubated in a thermostat for 24 hours and then left for 48 hours at room temperature. The number of colonies on the plates is counted, the arithmetic mean is calculated and recalculated to the number of microorganisms in 1 m 3 of air.

Air testing includes determining the total number of saprophytic bacteria, staphylococci, streptococci, which are indicators of biological contamination of the air by the microflora of the human nasopharynx.

11. On what media is coliform cultured?

On Endo medium, on simple nutrient media: meat-peptone broth (MPB), meat-peptone agar (MPA).

12. What objects and items are subject to examination in the premises of pharmacies during sanitary and microbiological control?

Objects of bacteriological research in pharmacies during sanitary and microbiological control:

1 . Distilled water.

2 . Injection solutions before sterilization.

3 . Injection solutions after sterilization.

4 . Eye drops after sterilization.

5 . Eye drops prepared under aseptic conditions on sterile bases.

6 . Dry medicinal substances used for the preparation of injection solutions.

7. Pharmaceutical glassware, stoppers, gaskets, and other auxiliary materials.

8. Inventory, equipment, hands and sanitary clothing for personnel.