Breaking down biofilms

By Jake Anderson

Since the transition to antibiotic-free (ABF) and No Antibiotics Ever (NAE) production models, the focus on water quality has continually increased. The focus isn’t only on the chemical composition of the water, but the organisms that inhabit the inside of water lines. When it comes to discussing these organisms, the term “biofilm” is frequently used.
chickens drinking water

Biofilm or “biofilms” for the lack of better term have become a buzzword in poultry production. However, this is not without cause. Biofilms pose unique challenges once established on the inside of water lines. This article will briefly discuss biofilms, the challenges they pose, and how to properly manage them.

What are biofilms?

A biofilm is a group of microbial cells attached to a surface and enclosed in an extracellular polymeric substance matrix (Donlan, 2002). Think of biofilms as a community of microorganisms that are inhabiting the inside of water lines. No different than the communities we live in, biofilms are very diverse and are composed of a wide variety of organisms. Most of these organisms likely do not pose a threat to production. But there are many organisms that live in these biofilms that can cause problems.

The extracellular polymeric substance matrix (EPS) is the structure of the biofilm viewed as the “house” inhabited by these organisms. The main building blocks of the EPS are polysaccharides (Brider et al., 2011), but they also utilize calcium, iron, and manganese in their construction. The EPS is essentially the brick and mortar of the biofilm; the other components such as calcium, iron, and manganese would be analogous to rebar for reinforcement. The extent of biofilm formations inside the water lines is dependent on a multitude of factors such as the chemical composition of the water, the organisms present in the water lines, the materials of the water system, and the production practices that are employed regarding water. All in all, biofilms are very diverse and dynamic environments and are ever changing based on internal and external factors.

What challenges do biofilms present?

Biofilms pose significant challenges to disinfection. The “resistance” to disinfectants expressed by the organisms that inhabit the biofilms could more aptly be described as an insusceptibility or lack of physical accessibility. The insusceptibility exhibited is multifaceted. These factors include, but are not limited to, the structure of the EPS, disinfectant penetration (or the lack thereof) into the biofilm, and synergistic effects between the organisms inside the biofilms (Brider et al., 2011). Most of the disinfectants available or commonly used for disinfection of poultry water lines (while birds are present) are oxidizers (there are some exceptions) that are highly chemically reactive. This high level of reactivity, paired with the primary organic composition of the EPS, has been shown to lead to reduced efficacy and penetration into the biofilms. Ultimately, this results in organisms being exposed to sublethal levels of disinfectant (Brider et al., 2011).

Synergistic effects between various species of organisms that inhabit biofilms have also been observed that result in increased insusceptibility (Brider et al., 2011). These observed mechanisms of insusceptibility to disinfectants pose significant challenges to removal of biofilms in water lines. This insusceptibility is typically only observed for the organisms that are on the inside of the biofilm; planktonic organisms (those on the outside of the film) are vulnerable to standard disinfection practices.

Removing or controlling biofilms on the inside of water lines takes a comprehensive approach in order to be successful. Typically, most approaches to water line cleaning/ disinfection only cover part of the holistic approach. A comprehensive water program should include three separate and unique processes:

  1. Removing the structure and building blocks of the biofilm (water line cleaning or descaling).
  2. Killing the organisms that lead to the formation of the biofilm (water line disinfection).
  3. Preventing the establishment of these organisms in the water lines (continuous disinfection).

Water line cleaning/disinfection, often referred to as “terminal” water line cleaning in between flocks, has been commonplace for many years and most production models have at least some sort of cleaning program in place. Having some sort of program is better than having nothing at all, but developing a program that is suited to the needs based on the end goal is going to be much more effective. Water line cleaning/disinfection is a great opportunity to make a large impact in a short amount of time due to the advantages presented by not having animals present at the time of application. Without animals, the types of chemicals and concentrations that can be used is far greater than what can be used with animals (low ppm versus 3% application rates). Also, the low-cost versus potential return is a very attractive part of terminal cleaning/disinfection.

When it comes to water line cleaning. there are two separate and distinct processes: cleaning and disinfection. These two processes are often lumped together, but are significantly different. Water line cleaning is the process of removing debris, buildup, and scale. Disinfection is the process of killing the organisms that are inhabiting the inside of the water lines themselves.

Locations that are good candidates for a water line cleaning are those with high calcium (“hard water”), iron, and manganese content. Locations that have high concentrations of these elements will often have visible signs, such as crusty scale on the cool cell pads or on the drinker nipples. High iron will have the telltale signs of red/ orange staining on the cool cell pads or water spigots or a red/orange tinge to the water. High levels of these elements can be confirmed by a water test. Locations where these conditions exist should focus on the cleaning or descaling aspect and select products that are suited to cleaning and the removal of the scale architecture that supports biofilm formation and growth.

Scenarios where to focus disinfection include those locations that either have performed the cleaning process prior and have returned the lines to their original “slick”, clean status or locations that have source water that is low in calcium, iron, and manganese, and the risk of scale formation is minimal. Other locations that are good candidates for terminal disinfection are those that have filtration in place, have strict water line flushing/cleaning programs, and have been on continuous disinfection for an extended period.

How are biofilms best managed?

Selecting a product(s) to carry out the terminal water line cleaning/disinfection should be directly based on the process needed. There are a multitude of products used for water line cleaning and disinfection that represent a wide variety of chemical classes such as, but not limited to, peroxygens, halogens, acids, chelators, and quat-based products. Most products that fall into this category of water line cleaners or disinfectants are either good at cleaning or good at disinfecting; there are not many that are good at both due to the chemical nature of the product. Many of these products are commodity-type products, although there have been a few unique combination chemistries developed that employ chemicals from multiple classes to achieve the best results in their respective application. It is imperative to choose a product that matches the desired end goal of either cleaning or disinfection.

After terminal line cleaning or terminal disinfection is performed, the residual chemical is typically flushed from the water lines before animals are placed. By doing so, any residual protection from these chemicals is negated. Once this residual is gone, any organisms that may have survived or any new organism that may enter the water lines can then begin the process of inhabitation and biofilm formation all over again. This is where continuous disinfection comes into play.

Continuous disinfection provides protection over the life of the flock or over duration of the turn. Having a good, continuous disinfection program prevents repopulation of water lines and provides “protection” until the next line cleaning or line disinfection is performed. Just like terminal line cleaners and terminal line disinfectants, continuous disinfectants are available in a wide array of products and should be matched to the water and production model.

Biofilms are an ever-present problem and threat to the production model. However, possessing a basic understanding of how they work, the impact they can have on disinfection, and how to combat them is key to being successful. For more information on biofilms and their control, please reach out to your MWI Territory Manager.

Having a good, continuous disinfection program prevents repopulation of water lines and provides “protection” until the next line cleaning or line disinfection is performed.

References
Donlan RM. Biofilms: microbial life on surfaces. Emerg Infect Dis. 2002;8(9):881-890. doi:10.3201/eid0809.020063
Bridier A, Briandet R, Thomas V, Dubois-Brissonnet F. Resistance of bacterial biofilms to disinfectants: a review, Biofouling. 2011;27:9, 1017- 1032. DOI: 10.1080/08927014.2011.62689

About the Author

Jake Anderson

Water Treatment
MWI Animal Health
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