Study Shows Water Hoses as Reservoirs for Biofilms in Food Processing Facilities
A recent study investigating biofilms in water hoses used in a meat processing facility revealed ubiquitous microbial colonization, reaffirming concerns about hoses as reservoirs for pathogens that could lead to cross-contamination in food production environments.
Biofilms are an important food safety threat in food processing environments, as they can promote the growth and survival of foodborne pathogens that have significant public health implications. For example, another recent study demonstrated Listeria monocytogenes’ ability to colonize preexisting multispecies biofilms within hours and persist over time, without disrupting the biofilm’s structure or matrix composition. Moreover, research has shown that L. monocytogenes from multispecies biofilms may grow in much greater abundance than those from single-species biofilms.
For the present study, over the course of an eight-month sampling assignment, biofilms were detected in 14 out of 15 water hoses made of thermoplastic elastomer and polyester, most of which were used daily. The 13-millimeter (mm) hoses, which were connected to a drinking water-quality supply, were used for cleaning and sanitation of the equipment and facility, as well as supplying water for food production.
Hoses were sampled from five different locations throughout the facility, at three different points across the eight-month period. The hoses were replaced after each sampling event. A regular cleaning schedule for the hoses was not in place.
Using a combination of optical coherence tomography (OCT), biochemical assays, and DNA sequencing, researchers identified and characterized diverse bacterial and fungal populations inhabiting the inner surfaces of the hoses.
The most prevalent bacteria present in the biofilm communities included Mycobacterium, Rhodococcus, and members of the families Comamonadaceae and Rhodobacteraceae. Notably, Mycobacterium—which includes opportunistic pathogens like M. avium—was consistently present across all samples. Opportunistic pathogens such as Legionella, Pseudomonas, and Neochlamydia were detected at low levels.
Fungal diversity was limited, with Trichoderma emerging as the most prevalent genus. Other fungi, including Polyschema, Sistotrema, and Asterostroma, were sporadically detected. The presence of Trichoderma, which has been linked to human infections, raises additional health concerns.
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Despite uniformity in hose material, water source, and ambient temperature (10–12°C), microbial communities varied significantly between sampling points. Only one of the hoses was used on a weekly basis as opposed to daily, and that hose exhibited distinct microbial profiles compared to those used more frequently. Variations in water pressure and potential desiccation may have contributed to these differences.
Interestingly, the presence of biofilms did not correlate with usage frequency or sampling time point, suggesting that other operational factors may influence biofilm development. The study also noted that OCT imaging, while useful for detecting thick biofilm layers, may miss thinner or patchy biofilms detectable through biochemical methods.
The detection of opportunistic pathogens and spoilage-associated bacteria—even at low levels—highlights the potential for water hoses to act as reservoirs for contamination. These findings align with previous research indicating that biofilms in water systems can compromise hygiene and product shelf life in food processing facilities.
Given the lack of a cleaning schedule for the hoses and the observed microbial diversity, the study underscores the need for routine monitoring and maintenance of water delivery systems. Future research should aim to identify the specific factors influencing biofilm formation and persistence in food industry settings.
Published in the Journal of Food Protection, the study was conducted as part of a project within the Austrian Competence Center for Feed and Food Quality, Safety, and Innovation (FFoQSI); and included researchers from FFoQSI, the University of Veterinary Medicine Vienna, and the Research Center for Non-Destructive Testing. The study’s first author was Nadja Pracser, Ph.D.
