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Biofilms Of Water Borne Pathogens

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Most microorganisms on Earth live in various aggregates which are generally termed “Bio films”. They present and represent the most successful form of life. They are the active agents in bio filtration and carriers of the self-cleaning potential in soils, sediments and water. They are also common in surfaces in technical systems where they sometimes cause bio fouling. In recent days it has become evident that bio-films in drinking water distribution can become a long-term, habits for hygienically relevant microorganisms. Important categories of these organisms include faecal indicator bacteria like (e.g. E. coli), obligate bacterial pathogens of faecal origin (e.g. campylobacter spp.) opportunistic bacteria of environmental origin (e.g. Legionella spp., pseudomonas aeruginosa), enteric viruses (e.g., adenoviruses, rotaviruses, noroviruses) and parasitic protozoa (e.g. Cryptosporidium parvum). These types of organisms can attach to preexisting biofilms, depending upon biology and ecology these organisms integrated and survive for days to weeks or even longer duration. There are some indicators at a part of the biofilm populations of pathogenic bacteria persists, but non-culturable state and remains unnoticed by some methods we use for detection. Thus, these biofilms act as a reservoir for pathogenic microorganisms and represent a potential source of water contamination, this results in health risk for humans if they are unnoticed.


According to the World Health Organization the drinking water should be free from any organisms that might cause health risk to human population. The life of microorganisms in environment is different from the laboratories. In biofilms, the organisms are irreversibly associated with a surface and enclosed in a matrix. Biofilms are also called as solid surfaces; all these common features take substantial ecological benefits from these structures.

Among those the formation of stable, synergistic micro consortia, the EPS; containing extracellular enzymes they convert matrix into extracellular digestion system; facilitated gene transfer and intense intracellular communication. These features have recently been reviewed by Flemming, 2008 and Wingender, 2010. For long time biofilms became a side issue and they experienced little awareness, also they were a common sight all the time.

On seeing this some sophisticated methods have been introduced into biofilms such as fluorescence microscopy and confocal laser scanning microscopy, micro electrode and advanced chemical analysis, molecular biology is the most powerful among them. Biofilms have a very beneficial aspect. They are carriers of self-cleaning potential of soil, sediment and water by mineralization of organic matter.

They mostly employed for biological purification of drinking water in biofilters of waste water treatment and they also drive waste water disposal. They also do composting processes and done by thermophilic organisms which generates sufficient heat to inactivate pathogens from raw material composts. They mainly focus on role of biofilms as a habitat for pathogens and other hygienically closer microorganisms.


Biofilms develop on all surfaces in contact with non-sterile water. Pathogen even present below the detectable limit in water and can accidently attach to biofilms which then act as their environmental reservoir and represent a potential water contamination source. Due to continuous erosion their will be detachment from biofilms, but it has to be taken into account that erosion does not occurs constant base. Patches of biofilms can be detached by leading to locally high cell densities in water phase. Bacterial numbers in water phase do not indicate biofilms nor they can locate. Humans are the main host when susceptible and exposed to contaminated water, a health risk is present. Infection can be occurred by ingestion of contaminated water, inhalation of aerosols containing pathogens or in contact with skin, mucous membrane, eyes and ears. Some metabolic products like hydrogen sulfide and nitrite or endotoxins impacts of biofilms to the hygienic quality of water. It can be seen by discoloration, turbidity and malodors. Sometimes biofilms support the trophic food chain that leads to occurrence and growth of protozoa and eventually invertebrate animals.

Some of the critical conditions are the water systems of hospitals and other health care facilities, where biofilms born pathogens can contribute to water associated nosocomial infections. Biofilms acts as a source for the pathogens at continuous expose of patients and all surfaces which may come into contact with polluted water.

In fact, about 95% of bacterial numbers in drinking water system are located at surface compared to water phase and detected by using sampling techniques used by quality control these strategy were used by the water suppliers to limit the growth of microbes, it acts as goal of water treatment based on water depletion. This results in ‘stable drinking water’ which does not show elevated microbes number to the consumer due to regrowth.

After several months, a phase of biofilms formation on inert materials employed in drinking water when surface is reached, which varies strongly. The total cell count is between 104 to 108 cells/ cm2, the culturable HPC count of bacteria in biofilms can be vary between 101 to 106 Cfu/cm2.

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Water temperature, hydraulic conditions, nutrient availability and concentration of dis infectant these are some factors that influences the biofilms growth. By grazing protozoa, they control biofilm in drinking water. These natural population usually develop and constitute the biofilms, and are commonly non pathogens.


Two categories of relevant microorganisms can be distinguished:

  1. Microorganisms with pathogens and its properties which have been shown to be associated with water related illness and its out breaks.
  2. Bacteria which are primarily used as index and indicator organisms in water analysis, indicating the presence of pathogenic organisms of faecal origin or indicating effectiveness of water treatment processes as well as integrity of water distribution system.

Obligate water related pathogens, those which cause disease in humans are faecally derived for their health status. Others are opportunistic pathogens which causes disease in sensitive human groups such as elders, children’s, immunocompromised individuals, patients with preexisting disease which facilitates infection by these organisms.

Opportunistic pathogens are frequently as well as natural aquatic organisms and adapted to oligotrophic environmental conditions mainly on drinking water system. Some are derived as emerging pathogens either newly discovered pathogens or pre existing pathogens like campylobacter spp, H. pylori, Legionella spp., cryptosporidium spp. Or as new varieties of already known species e.g., enterohaemorrhagic E. coli 0157:H7.[image: ]

The organisms may attach to surface as primary colonizer and establish an active biofilm in combination with other microorganisms. They also can become integrated in preexisting biofilms as secondary colonizers. Some bacteria, can multiply if they adapted to oligotrophic conditions of many artificial water systems like hetero trophic bacteria, free living protozoa and fungi. Suitable laboratory conditions, all relevant water related pathogenic species of bacteria have actually been shown to be attached to solid surface and to form mono-species biofilms, which indicating their potential as biofilm organisms. However, enteric viruses and parasitic protozoa are obligate parasites mainly depend on multiplication in animal or human hosts. Such organisms can only be expected to attach to persist in biofilms without being able to proliferate.

Microcolony on steel after 14 days of exposure to drinking water. Partially, normally stainless-steel products strongly support the bacterial growth in the biofilm formation for an extended period of time, which greatly increases the risk of cross contamination of bacteria such as Escherichia coli and staphylococcus aureus.

Drinking water biofilms on steel surface after 14 days of exposure to drinking water (magnification: 1000x).


  1. Bacterial pathogens of faecal origin: some water born bacterial pathogens which can infect the gastrointestinal tract in humans. And in warm blooded animals they are extracted with faeces into environment that includes Salmonella enterica, Shigella spp., Vibrio cholerae, pathogenic E. coli, Yersinia enterocolitica, Campylobacter spp., etc. These pathogens have in common that they are transmitted by ingestion of faecally contaminated water and causes primarily diarrhea diseases.
  2. Enteric viruses: These viruses involved in water related diseases cause acute gastrointestinal illness (e.g., noroviruses, rotaviruses) and can also affect other organs like the liver or central nervous system caused by Poliovirus. They also excreted in the faeces of infested humans and transmitted by ingestion. In contrast to bacterial pathogens, if little information exists on the presence and survival of enteric viruses in biofilms of water distribution system.
  3. Intestinal protozoan parasites and free-living protozoa: Main protozoan parasite which involved in waterborne outbreaks of gastrointestinal disease due to the contamination of swimming pools and DWDS water system include Cryptosporidium spp., and Giardia lamblia. They are also called obligate parasites present in the intestine of host like humans or animals and excreted through faeces and highly infective during oocyst stage. This transmissible stage can present viable in aqueous environment out the hosts for along weeks to months and they are highly resistant to chlorine and chloramine.
  4. Free living protozoa: some free-living protozoa like Naegleria and Acanthamoeba species are opportunistic pathogens and been implicated in water related disease. Free living protozoa are common group of biofilm communities in drinking water systems including filters like sand filters, activated carbon filters of water treatment plants, plumbing systems and cooling towers and water system. For example, amoeba, including hygienically relevant thermophilic Acanthamoeba species, they were detected in recovered biofilm pipe surface at densities between 2 and over 300 amoeba/cm2.
  5. FUNGI: Fungi are common contaminators and they are observed by scanning electron microscopy further suggested that spores, not hyphae or vegetative cells. Fungi were isolated from water of municipal water distribution networks and from plumbing system in hospitals. The observation suggests that biofilms of drinking water distribution network like hospital plumbing systems occasionally be a reservoir of fungi with pathogenic properties.
  6. ALGAE: These are most biofilm forming organisms on the earth. In surface of the water, algae occurring in both planktonic form and biofilms may contain toxins forming species such as microcystin and represent a serious threat to human health. Recently, a highly sensitive amperometric immunosensor for microcystin detection in algae and their biofilms are detected. In the drinking water distribution network and installation, however, algae do not occur due to lack of light.


The detergent 1 type is the initial enzyme solution, and the detergent was 2 type that represents soda or acid which were used to adjust the pH and clean the pipe lines. The process of cleaning can be carried by following steps:

  • Drain the retention water in all pipes and equipment.
  • Remove the in line micro filter unless they are necessary to protect instruments or be cleaned.
  • Pump detergent second type (200g/L soda) into water tank to keep the pH at 10 ±1.
  • Pump detergent first type (enzyme) into water tank and water distributing networks to make the enzyme concentration reach 0.25%.


So, to conclude the present study, culture of aqua guard water reveals a very low prevalence of bacteria and all were low biofilms producers. Whereas water from pipeline sources was unsatisfactory for consumption as the MPN counts were > 10. Most of the biofilms producer were gram negative(-ve) and Pseudomonas and Acinetobacter spp. They were strong (4+) biofilm producers in high numbers (17.1%).

It has become clear that the biofilm mode of existence of pathogens is an important factor that has to be include in risky assessment applied to water related pathogens. This knowledge contributes to a basis for the proper operation and maintenance of water system in order to assume the provision of micro-biologically safe drinking water and other types of water network systems. Their main aim is to minimize the disease affect or burden on human population from their artificial man made water plants and system.


  3. International Journal of Hygiene and Environmental Health by Jost Wingender, Hans-Curt Flemming.

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Biofilms Of Water Borne Pathogens. (2022, February 17). Edubirdie. Retrieved March 27, 2023, from
“Biofilms Of Water Borne Pathogens.” Edubirdie, 17 Feb. 2022,
Biofilms Of Water Borne Pathogens. [online]. Available at: <> [Accessed 27 Mar. 2023].
Biofilms Of Water Borne Pathogens [Internet]. Edubirdie. 2022 Feb 17 [cited 2023 Mar 27]. Available from:
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