Shower Head
Introduction
Shower heads are overhead projectors containing pores in which water is sprayed out onto the body of individuals, usually for the purpose of cleaning oneself. But other than removing the dirt on an individual's body, the shower head may expose these individuals to microbes that colonize the inside of these shower heads. Although the types of microbes that live there differ depending on the water source and other external factors, some of these microbes may be opportunistic pathogens that have the potential of harming immunosuppressed individuals (1). It is thus beneficial to explore the composition of the microbial community that resides within the shower head to devise a way to counteract opportunistic pathogens.
Physical environment
The inside of the shower-head is typically dark and its physical conditions fluctuate from each use. The environmental conditions change from having extreme amounts of water flow of various temperatures to being static and moist. Each use of the shower replenishes the niche with low levels of nutrient and seed organisms (1). These harsh conditions within the shower head pose a benefit to microbes that have the ability to form biofilms (1). Based on where the water source is supplied from, the composition of the water varies which also affects the microbial composition of the shower head biofilm. For example, in homes where the water is supplied from individual wells close to oil and gas drilling sites, there is an abundance of methane and methanol metabolizing organisms due to increased methane and chemicals in the water system (1).
Microbial processes
Biofilm Formation
The microorganisms found to highly colonize the shower head are those that have to capability of forming biofilms (1). Some of these microorganisms have the ability to secrete gellan and welan which are exopolysaccarides that form the main components of biofilm (9) while others adhere well to surfaces on the shower head (2). Acrylonitrile butadiene styrene (ABS) is commonly material used to make shower heads. However, this plastic material is prone to biofilm formation thus many researchers are trying to decrease this property (10). Further more, the flow of water brings in nutrients to the immobilized bacteria of the biofilm thus enhancing their colonization and increasing the rate of its biofilm formation (2). All of these environmental conditions support and select for microorganisms that have the ability of forming and surviving in biofilms. Thus it is no surprise that the main microorganisms found in the shower head biofilm are all capable of biofilm formation.
Key Microorganisms
The majority of the microorganisms that are found in the shower head biofilm are composed of microbes that can commonly be found in water and soil. However because of the physical environment within the shower head, microbes that are capable of forming biofilms are strongly selected for (1).
Mycobacterium spp.
Feazel et al. found Mycobacterium spp. (hyperlink 1) as the most abundant (28.1%) microorganism in the shower head biofilm community (1). Mycobacterium can be found in water as free-living microbes or attached onto surfaces between liquid-solid interfaces (2). The high hydrophobic content in their cell wall positively influences their adhesion properties thus they adhere especially well to hydrophobic substances (2) (ie. the shower head made of ABS). The flow of water to the biofilm site which brings in nutrients to the immobilized bacteria also increases the rate of biofilm formation (2). Just as the environmental conditions within the shower head support the accumulation of Mycobacterium, their resistance to chlorine is thought to be another reason of its high concentration within shower head biofilms (1).
Methylobacterium spp.
Methylobacterium (hyperlink 2) have been found to grow well in wet environments (9). These bacteria are capable of biofilm formation and are found to exist in a high percentage (21.7%) within the shower head biofilm, making it the second most abundant microorganism in the biofilm community(1). Experiments showed that Methylobacterium are strong biofilm producers even when competing with other bacteria (11) which may be linked to its high colonization of the shower head biofilm. In regions where the water source came from wells near sites of oil and gas drilling, an increased methane and chemical substances can be found in the water, promoting the growth of methane using microbes (1).
Sphingomonas spp.
Sphingomonas (hyperlink 3) can often be found in environments such as soil, water and sediments (9). These bacteria are known to form biofilms in water systems such as water meters, water taps and water pipes (1, 4) which does not come as a surprise that they are also found in biofilms within the shower head. Sphingomonas populate 2.7% of the shower head biofilm community (1).
When Sphingomonas adhere to surfaces, they readily secrete gellan and welan which are exopolysaccarides that are the main components of biofilm (9). It may be due to their ability to survive harsh environmental conditions such as low nutrient levels and in the presence of toxic chemical materials that Sphingomonas can be found in these different environments (4).
Concerned opportunistic pathogen in biofilm community
Although there is little growth of L. pneumophila (hyperlink 4) in the shower head biofilms, many people fear its increase because inhalation of this opportunistic pathogen may cause Legionnaire’s Disease (hyperlink 5) (1). If L. pneumophila were to colonize the shower head biofilm in a higher density, there would be an increased chance that this bacteria would arrive in lungs of individuals via aerosols generated from showering water (1).
L. pneumophila
Legionellae can be found in freshwater environments, growing within free-living protozoa. The reason that they are usually found as intracellular parasites is because they are often out-competed by indigenous organisms (5). For example, the nutrients that these bacteria require to grow on are often not found in aquatic environments such that when the nutrients do come about, they are quickly taken up by other organisms. For this reason, to have Legionellae growing in a bacterial biofilm within the shower head, requires the presence of free-living protozoa even though Legionellae have the ability to adhere to existing biofilms (5). Without the presence of these protozoa, even if Legionellae can attach to the biofilm but they will not be about to survive long (6).
Current Research
Does shower usage increase risk for Non-tuberculous mycobacteria Disease?
With the knowledge that Mycobacterium avium are known to populate the biofilm within shower heads, the question now is whether shower usage would increase the risk for Non-tuberculous mycobacteria (NTM) (hyperlink 6) disease. Although currently there is no epidemiological data that can be used to answer this question, some recent studies have found a link between pulmonary M. avium infections and the microbiology within home shower heads (1, 7). It has been hypothesized that the increased occurrence of NTM diseases can be correlated to the increased popularity of showers over baths (8). This means that the increased exposure to microorganisms via aerosols generated from the use of showers can be correlated with the rise of individuals infected with NTM diseases (1). Therefore it is advised that immunosuppressed individuals should take caution when taking showers or instead of taking showers, they should change to taking baths which decreases the chance of breathing in aerosols containing shower head biofilm microorganisms (1).
References
1. Feazel LM, Baumgartner LK, Peterson KL , Frank DN, Harris JK, and Pace NR. 2009. Opportunistic pathogens enriched in showerhead biofilms. PNAS.106:16393–16399. DOI: 10.1073/pnas.0908446106.
2. Schulze-Robbecke R, Janning B, and Fischeder R. 1992. Occurrence of mycobacteria in biofilm samples. Tubercle Lung Dis. 73:141–144. DOI: 10.1016/0962-8479(92)90147-C.
3. Yamazaki Y, Danelishivili L, Wu M, MacNab M, and Bermudez LE. 2006. Mycobacterium avium Gene Associated with the Ability to form a Biofilm. Appl. Environ. Microbiol. 72:819-825. DOI: 10.1128/AEM.72.1.819-825.2006.
4. Koskinen R, Ali-Vehmas T, Kampfer P, Laurikkala M, Tsitko I, Kostyal E, Atroshi F, and Salkinoja-Salonen M. 2000. Characterization of Sphingomonas isolates from Finnish and Swedish drinking water distribution systems. J. Appl. Microbiol. 89:687-696. DOI: 10.1046/j.1365-2672.2000.01167.x.
5. Murga R, Forster TS, Brown E, Pruckler JM, Fields BS, and Donlan RM. 2001. The role of biofilms in the survival of Legionella pneumophila in a model potable water system. Microbiology. 147:3121–3126. DOI: not found.
6. Donlan RM. 2002. Bioflims:Microbial Life on Surfaces. Emerg. Infect. Dis. 8:881-890. DOI: 10.3201/eid0809.020063.
7. Falkinham JO, Iseman MD, Haas P, and Soolingen D. 2008. Mycobacterium avium in a shower linked to pulmonary disease. J. Water Health. 6:209–213. DOI: 10.3201/eid1711.110050.
8. O’Brien DP, Currie BJ, and Krause VL. 2000. Nontuberculous mycobacterial disease in northern Australia: A case series and review of the literature. Clin. Infect. Dis. 31:958–967. DOI: 10.1086/318136.
9. Kelley ST, Theisen U, Angenent LT, Amand AS, and Pace NR. 2004. Molecular Analysis of Shower Curtain Biofilm Microbes. Appl. Environ. Microbiol. 70:4187-4192. DOI: 10.1128/AEM.70.7.4187–4192.2004.
10. Junker LM, and Hay AG. 2004. Effects of triclosan incorporation into ABS plastic on biofilm communities. J. Antimicrob. Chemoth. 53:989-996. DOI: 10.1093/jac/dkh196.
11. Simoes LC, Simoes M, and Vieira MJ. 2007. Biofilm Interactions between Distinct Bacterial Genera Isolated from Drinking Water. Appl. Environ. Microbiol. 73:6192-6200. DOI: 10.1128/AEM.00837-07.
