The ugly grasp of biofilms

The plated filters yielded the following results

Growth on EMB was followed by the use of Enterotube II, a commercial testing system for identification of gram negative, oxidase negative rods belonging to the enterobacteriaceae family.

Escherichia coli (E. coli), Proteus mirabilis, Yersinia pseudotuberculosis, Shigella sp, Serratia sp., and Klebsiella sp., were among the organisms identified in this group.

Gram positive, catalase positive cocci that formed yellow colonies on MSA followed by a positive rabbit plasma coagulase test confirmed the presence of Staphylococcus aureus, Pseudomonas F agar, and OxiFerm tubes, a commercial test system for gram negative, oxidase positive rods were used to identify the presence of various Pseudomonas species. Growth on Sabaroud Dextrose agar, colony morphology, and gram stain indicated the presence of fungi.

BCYE agar with polymyxin-anisomycin-vancomycin (PAV) was used for enhanced growth of presumptive Legionella species. PAV inhibits gram positive organisms, while polymyxin B inhibits many gram negative bacilli, and anisomycin suppresses yeast. On BCYE agar, Legionella pneumophila produces green colonies and Legionella micdadei produces blue colonies and suspected Legionella sp., was further tested serologically using a latex bead agglutination test.

Association of infections with whirlpool bathtubs has been recognized for a number of years, but due to the increased popularity of hydrotherapy the matter should be brought to public attention. There are several explanations for this lack of association between whirlpool bathtub use and subsequent clinical disease in the public eye. The implication of whirlpool bathtub aerosol exposure may represent 
an unrecognized source of infection in 
the medical history of a high proportion 
of clinical cases.

Whirlpool bathtubs remain popular with homeowners

A survey by the National Association of Home Builders (NAHB) shows 58 per cent of owners want a hot tub or whirlpool bathtub, with the latter being increasingly popular in hotels, hospitals, and health resorts.

Due to this popularity, not only does the public need to be educated on the possible risks associated with them, but the industry also needs to explore more effective ways to prevent the growth of biofilm in these environments through advanced cleaning methods and new design technologies.

Ideally, every time a dormant hot tub 
is filled with water it should be purged, drained, cleaned, and refilled until there is no more evidence of biofilm. Hot tubs are constructed in such a way where they
do not gravitationally drain so water can remain in lower lying pipe areas making them even more susceptible to biofilm growth. Once hot water is circulating within the hot tub, there is a new breeding ground for continued bacteria and biofilm growth.

What is lurking in the plumbing?

According to Moyes, whirlpool bathtubs are almost always a prime area for potentially harmful microbes, with the main reason being the lining of the pipes.

“They are full of inaccessible air, and water tends to get trapped in these pipes, often for long periods of time,” she explains. “When the jets are then switched on, this water, containing harmful bacteria, gets blown into the tub where bathers are soaking.”

A typical whirlpool bathtub incorporates a system of inaccessible airlines and plumbing lines. When a bather fills the tub and activates the system, normal flora, dirt, sloughed skin, body fluids, bath oils and additives, fecal matter and soap scum circulate through the system and buildup inside the plumbing lines as biofilm. Biofilm is abundant in nutrient-containing aquatic environments and, due to physiological co-operation, is inherently more resistant to various antimicrobial treatments and cleaning methods. Manufacturers recommend flushing the system with automatic dishwasher detergent, bleach, vinegar, or baking soda, but the effectiveness of these products are highly doubtful. In fact, most systems permit dirty bathwater to backfill the airlines when the pump is turned off.

Unlike plumbing lines, airlines will not admit fluid while the pump is operating. Even if industry-recommended cleaning agents were effective, they cannot reach the airlines, making it impossible to completely clean the entire system, although whirlpool bathtubs are typically drained after each use, it appears the circulation system does not fully drain. The American National Standards Institute (ANSI) has adopted a standard that permits the typical circulation system to retain more than 295 ml (10 oz) of bathwater when the whirlpool tub is fully drained. Stagnant, organic-containing bathwater trapped inside a system already rich in biofilm provides an ideal environment for bacteria to flourish. These factors combine to expose the bather to potentially pathogenic organisms.

To get an idea of how much bacteria can be in the pipelines of a whirlpool bathtub, the study shows a normal teaspoon of tap water contains an average of 138 types of bacterium, with many samples not having any bacteria at all; however, the same teaspoon of water from a whirlpool bathtub contains an average of more than 2.17 million bacterium.

As well as leading to numerous diseases (e.g. urinary tract infections, septicemia, pneumonia, and several types of skin infections), because of the aerosol mist created by the whirlpool action, microbes are forced into bather’s lungs or even open wounds. One bacterium, Legionella pneumophila, can cause Legionnaires’ disease, of which 90 per cent of all cases can be traced back to bacteria developed from a warm environment.

Moyes says studies such as this were performed in the ’70s, but the evidence collected did not show any sufficient reasons for concern as whirlpool bathtubs, or even spas/hot tubs for that matter, cannot be clearly identified as the source of infection. For instance, should someone develop 
a respiratory problem, a doctor can diagnose a respiratory infection, but he/she cannot determine how they got it. Therefore, the best way to prevent biofilm from forming is to scrape the pipes clean.