Organisms that are indicators of fecal contamination

The use of typical enteric organisms as indicators of fecal contamination (rather than pathogenic agents themselves) is a generally accepted principle for monitoring and assessing the microbiological safety of water supplies. Ideally, the detection of such indicator bacteria should indicate the possible presence of all pathogenic agents associated with such contamination. Indicator microorganisms must be easily isolated from water, identified and quantified. At the same time, they should survive longer in the aquatic environment than pathogenic agents, and should be more resistant to the disinfecting effect of chlorine than pathogenic ones. Almost no single organism can meet all of these criteria, although many of them do in the case of coliform organisms, especially E. coli, an important indicator of water contamination from human and animal feces. Other organisms that meet some of these requirements, although not to the same extent as coliform organisms, may also be used as additional indicators of fecal contamination in some cases.

Coliform organisms used as indicators of fecal contamination include common coliforms, including E. coli, fecal streptococci, sulfite-reducing spore-bearing clostridia, especially Clostridium perfringens. There are others anaerobic bacteria(for example, bifidobacteria), found in large quantities in feces. However, routine methods for detecting them are too complex and time consuming. Therefore, specialists in the field of aquatic bacteriology settled on simple, accessible and reliable methods for the quantitative detection of indicator coliform microorganisms, using the titration method (serial dilutions) or the membrane filter method.

Coliform organisms have long been considered useful microbial indicators of drinking water quality, mainly because they are easy to detect and quantify. These are gram-negative rods, they have the ability to ferment lactose at 35-37 °C (common coliforms) and at 44-44.5 °C (thermotolerant coliforms) to acid and gas, oxidase-negative, do not form spores and include species E. coli, Citrobacter , Enterobacter, Klebsiella.

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

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

    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

    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

Several groups of bacteria fall under the definition of “coliform”. For all cultural and morphological characteristics These are enterobacteria from the Escherichia coli group. They have several common features and are sanitary indicator microorganisms, since their detection in water, soil or other media indicates fecal contamination of the samples being studied.

Coliforms is a collective name that includes bacteria such as:

  • Escherichia coli.
  • Klebsiella.
  • Hafnia.
  • Citrobacter.
  • Enterobacter.

E. coli is present in every body, and this does not cause any consequences for human health as long as the indicator does not exceed the natural number of these bacteria. But when the norm is exceeded for some reason, symptoms of dysbiosis appear, which in most cases can be successfully treated in hospital. E. coli has two groups of representatives: normal and pathogenic. Lactose-positive and lactose-negative are not dangerous, and serotype O157:H7 is the cause of severe food poisoning.

The rod-shaped bacteria Enterobacter is found in soil and water, as well as in the intestines of mammals. Some representatives of this genus were isolated from plant roots. They are the causative agents of urinary tract infections and foodborne infections.

Microorganisms prefer Citrobacter aquatic environment, found in the ground and food products. They cause diseases only against the background of a weakened immune system.

Klebsiella is a protozoan capable of forming a protective capsule. Such coliforms, in addition to the intestines, are found on the mucous membranes and on the skin. Their presence in water, soil and plants makes it possible for Klebsiella to be present in fruits and vegetables.

Klebsiella pneumoniae

Hafnia is a genus of rods that have a negative Gram stain and live in humans, birds and bees. They are often isolated from honey, river fish, and dairy products.

The listed coliforms are unique indicators indicating the possible presence of pathogenic microorganisms in the sample.

Classification of coliform microorganisms

All of the described bacteria of the E. coli group are capable of fermenting lactose, but this happens at different temperatures. Therefore, they distinguish:

  • common coliforms (ferment carbohydrates contained in milk at 35-37°C),
  • thermotolerant or fecal coliforms (ferment sugar in milk at 44-44.5 ° C).

It is quite easy to detect them in the water and count the number. There should be no common coliform (as well as thermotolerant) microorganisms in it at all. Otherwise, the liquid is considered insufficiently purified and unsuitable for drinking.

How is research carried out in laboratories?

Coliforms identified in the studied samples have different sanitary and epidemiological significance. If thermotolerant bacteria of the genus Escherichia are found in milk, water or soil, this is direct evidence that fresh fecal contamination is occurring.

The presence of protozoa from the genera Citrobacter or Enterobacter will indicate that contamination occurred in the environment under study several weeks ago. Their presence is less significant.

If a person was sick with dysentery or typhoid fever, then lactose-negative types of E. coli will be found in the microflora by the time of recovery. They are so called because they have lost the ability to ferment lactose. But coliforms that will not grow in Coser's citrate medium and can ferment carbohydrates at temperatures between 43 and 45°C will tell doctors that there is fresh fecal contamination.

Coliform bacteria are detected using Koda nutrient medium. It allows you to find and identify enterobacteria by their ability to ferment lactose. If coliforms are present in the test samples, then the Code environment will either change the original green color to yellow and will become cloudy, or only cloudiness will be observed.

Thermotolerant and other coliforms are well detected on other nutritional compositions(meat peptone broth and meat peptone agar). If research is carried out using Endo medium, then they will appear on it in the form of flat red colonies. Escherichia coli forms a colony with a dark metallic sheen.

It must be remembered that pathogenic coliform strains enter the body through the fecal-oral route:

  • unwashed vegetables and fruits;
  • failure to comply with hygiene rules;
  • use of water (untreated) for irrigation;
  • Drinking milk or water that has not undergone heat treatment is a direct route of infection.

Since it is impossible to determine the presence of coliform bacteria in water or food at home, preventive measures include: The best way protect yourself from diseases.

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 number 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 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:

  1. Coliform bacteria (including thermotolerant ones).
  2. 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.

  1. Accordingly, if these bacteria are in drinking water, this means that there is a possibility of water contamination by wastewater.
  2. 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:

  1. Use only bottles that have been previously disinfected in an autoclave.
  2. Wash your hands with soap before taking a sample.
  3. 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.
  4. 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 diseases, but also because they are an indicator of water contamination by by-products (for example, too much organic matter, fecal water, etc.). In other words, this data does not have of great importance 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 when analyzing water from a groundwater source may be an early signal of aquifer contamination.

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

STYLAB offers test systems for the analysis of coliform bacteria (coliform bacteria) in food samples, as well as on work surfaces, tools and other objects.

Coliform (colimorphic) bacteria, or coliform bacteria (coliforms) is the collective name for some that have general features. Coliforms are usually classified as (E. coli), klebsiella ( Klebsiella), enterobacter ( Enterobacter), citrobacter ( Citrobacter) and hafnium ( Hafnia), however, sometimes Salmonella, Shigella, Yersinia and other bacteria are included in this group.

Enterobacter is a facultative anaerobic, motile, gram-negative, non-spore-forming rod-shaped bacteria, present in the intestines of many mammals, as well as in water and soil. Some of them, for example, Enterobacter cloacae, were isolated from plant roots. They are causative agents of food poisoning, as well as wound infections and urinary tract infections. Most often, diseases caused Enterobacter, occur in people with reduced immunity.

Klebsiella are gram-negative, non-motile, rod-shaped bacteria with a capsule that protects them from environmental influences. In addition to the intestines, they are found on the skin and mucous membranes, in water, soil and plants, incl. in fruits, vegetables, flowers and wood. In humans, Klebsiella causes intestinal infections, respiratory tract infections, including pneumonia, as well as conjunctivitis and meningitis; in animals, in addition, mastitis. The heat- and acid-stable enterotoxin of Klebsiella is similar in action to the heat-stable enterotoxin of Escherichia coli.

Citrobacter are gram-negative, motile, rod-shaped bacteria. living in water, soil and food. Many of them are opportunistic and cause opportunistic infections. Eg, Citrobacter freundii associated with diseases such as neonatal meningitis, brain and liver abscesses, etc.

Some bacteria of the genus Citrobacter are multi-resistant to antibiotics, which increases their potential danger.

Hafnia is a genus of gram-negative rods that live in humans, birds and bees, as well as in soil and water. Bacteria Hafnia alvei often isolated from vacuum-packed cold meat products, honey, dairy products, freshwater fish, and less commonly from vegetables. Hafnias cause diseases in poultry, accompanied by loss of appetite, decreased productivity, catarrhal enteritis, diarrhea and multifocal necrotizing hepatitis. There are known cases of septicemia in birds and rainbow trout.

For humans, these bacteria are opportunistic. Data on enteritis caused by hafnia are contradictory; it is currently believed that these microorganisms are likely causative agents of gastroenteritis. Hafnia causes respiratory and genitourinary tract infections, as well as abscesses.

Coliform bacteria are sanitary indicator microorganisms, indicating the likelihood of the presence of pathogenic bacteria in the sample. A separate sanitary indicator is fecal (or thermotolerant) coliforms. These include certain strains of coliforms. The presence of these organisms in the sample indicates fecal contamination. Based on the isolated bacteria, one can determine its age.

IN Russian Federation and countries of the Customs Union, the content of coliform bacteria in food products is limited by TR CU 021/2011 “On the safety of food products”, TR CU 033/2013 “On the safety of milk and dairy products” and other technical regulations. Current legislative information can be found on the website compact24.com .

Microbiological methods are used to determine coliform bacteria. Because they have general properties, for the analysis of coliforms it is convenient to use selective media.

Literature

  1. OK. Pozdeev. Medical microbiology. Moscow, GEOTAR-MED, 2001.
  2. João P. S. Cabral. Review. Water Microbiology. Bacterial Pathogens and Water. Int. J. Environ. Res. Public Health 2010, 7 , 3657-3703
  3. Badger, J.D.; M.F. Stins; K.S. Kim (1999). Citrobacter freundii Invades and Replicates in Human Brain Microvascular Endothelial Cells. Infection and Immunity 67 (8): 4208-15.
  4. Jia-Yi Tan, Wai-Fong Yin, and Kok-Gan Chan. Quorum Sensing Activity Hafnia alvei Isolated from Packed Food. Sensors (Basel). 2014 Apr; 14(4): 6788-6796.
  5. J. Michael Janda and Sharon L. Abbott. The Genus Hafnia: from Soup to Nuts. Clin Microbiol Rev. 2006 Jan; 19(1): 12-28.