Escherichia coli
One of the most common species of bacterium is Escherichia coli which can live happily inside your gut and help you to digest your food. However, if you have too many Escherichia coli cells in your gut you can get an upset tummy. Escherichia coli can survive on food that hasn’t been washed or cooked properly, or in soil, so it is important to wash your hands before you eat!
Escherichia coli is a common bacterium that can live inside the gut and help humans and animals to digest foods using enzymes. However, some strains of Escherichia coli can cause food poisoning in if contaminated products are eaten. One example is Escherichia coli O157:H7 which causes severe disease because it produces a specialised toxin that causes haemorrhagic diarrhoea, kidney failure, and potentially death (Jianghong Meng, 2012).
Escherichia coli can be transmitted in drinking water, fruits and vegetables (tomatoes, melons, parsley, cilantro, lettuce, spinach, etc.), raw milk or fresh meat. These products may have been contaminated at their origin or as part of the food manufacturing process. In the food industry, this contamination may take place before harvest, due to a contaminated water supply during cultivation. Contamination may also take place in post-harvest environments, where it may appear after washing and processing the raw material (e.g. carcasses, vegetables), but also when storage temperatures are too high and allow fast growth of any bacterial contaminants present.
The initial attachment of Escherichia coli and biofilm development on the surfaces is enhanced by the presence of flagella and fimbria. Many studies have demonstrated that Escherichia coli strains can attach to a variety of natural and synthetic surfaces including stainless steel, Teflon, glass, polystyrene, polypropylene and PVC. For example, one Escherichia coli strain showed strong biofilm formation on borosilicate glass and stainless steel, but little or no biofilm growth was observed on polypropylene, probably due to its hydrophobic (water repelling) nature. Temperature is also an important factor that affects Escherichia coli biofilm formation. For example, when Escherichia coli O157:H7 was incubated on the surface of beef at 15°C for 7 days, the number of adherent and planktonic cells increased. This behaviour represents a serious issue for meat processing plants, where the regular working temperature is 15°C.
Escherichia coli can also cause urinary tract infections in which bacteria enter the urethra and move up into the bladder. Escherichia coli move to the bladder using tiny structures, called fimbriae and pili, on their surface that propel them forwards and act as arms, allowing the bacteria to travel up the urethra (Sabitha Baby, 2016). Urinary tract infections are common in people with a catheter. Biofilms of Escherichia coli can form on the surface of catheters and enter the bladder this way. Biofilms make infections difficult to treat and can lead to recurrent infections as they persist on catheters using their adhesins to stay firmly attached to the surface as long as a catheter is present. It is difficult to get rid of catheter-associated biofilms.
Biofilms of Escherichia coli may also include other species, which benefit its survival. For example, survival rates of Escherichia coli on food industry surfaces were increased up to six-fold in the presence of other bacterial species such as Ralstonia insidiosa or Burkholderia caryophylli.
Escherichia coli survival under stress conditions and its biofilm formation abilities are strain dependent. For example, strain O157:H7 (a common STEC strain) was much more resistant to high temperature, high pressure and common food industry disinfectants than other pathogenic and non-pathogenic strains. Escherichia coli is also well known because of its ability to resist acid environments; this capacity enables strains like O26 to survive in the extreme acid conditions generated in some food industry processes involving acetic acid (e.g. canned vegetable products), citric acid (e.g. in the fruit juice industry), and propionic and lactic acids (e.g. in fermented dairy and meat products). Acid-resistant E. coli strains are also more resistant to gastric acid in the stomach and therefore more likely to survive and cause infection.
Soups, sauces, cooked chicken, ground beef, salads and other fresh products contaminated with acid- resisting strains have led to outbreaks and even death.
Another major problem with acid-resisting strains only a few are needed to cause infection. Therefore, even a low-grade biofilm contamination of a food factory installation is a serious health problem and requires that strong control measures be in place.
Between 2007 and 2013, in the EU, 423 foodborne outbreaks associated with pathogenic E. coli were reported. In 2011 a major outbreak of strain O104 was first identified in Germany in association with consumption of fenugreek sprouts and led in over 4,000 cases of infection and 54 deaths in 14 European countries, United States, and Canada. Also, 885 cases of haemolytic uremic syndrome (HUS) and 3,019 cases with diarrhoea were reported as a consequence of this outbreak.
Further reading on Escherichia Coli biofilms
Food microbiology: fundamentals and frontiers (4th edition), Chapter 12, Enterohemorrhagic Escherichia coli Jianghong Meng, Jeffrey T. LeJeune, Tong Zhao, Michael P. Doyle Book Editor(s): Michael P. Doyle, Robert L. Buchanan. First published: 28 December 2012. https://doi.org/10.1128/9781555818463.ch12.
Adhesins of Uropathogenic Escherichia coli (UPEC) Sabitha Baby, Vimal Kumar Karnaker, Geetha R K. International Journal of Medical Microbiology and Tropical Diseases, January-March,2016;2(1): 10-18. https://www.ijmmtd.org/article-details/1709.
Galié Serena, García-Gutiérrez Coral, Miguélez Elisa M., Villar Claudio J., Lombó Felipe. Biofilms in the Food Industry: Health Aspects and Control Methods. Frontiers in Microbiology, Vol 9, 2018, pp898. https://doi.org/10.3389/fmicb.2018.00898