Biofilm – Problem Areas
Biofilms directly cause infection in periodontal disease, chronic wounds, chronic ear infections, pneumonia in cystic fibrosis patients, endocarditis, implant and catheter associated infections, and are also associated with inflammatory skin infections such as seborrheic dermatitis and atopic dermatitis.
HAIs (Hospital-Acquired Infections) are infections acquired from hospitals as well as any other health care facilities (such as nursing homes and health clinics). The US Center for Disease Control and Prevention has attributed HAIs as the fourth leading cause of death, after heart disease, cancer and strokexix. In the United States, about two million HAIs occur every year resulting in 99,000 deaths and an estimated range of $28 billion to $45 billion in annual healthcare costsxx. MRSA (Methicillin-resistant Staphylococcus aureus) infections alone kill approximately 19,000 hospitalized American patients annually, which is similar to the number of deaths due to HIV/AIDS, Parkinson’s disease, emphysema and homicide combinedxxi.
1.1 Hospital-Acquired Infections
It is estimated that 80% of health care infections are caused by the microorganisms that patients bring with them to the health care facilityxxii. These microorganisms are opportunistic to the new environment and are able to take advantage of new routes into the body that medical procedures offer including surgery, implanted medical devices, and reusable medical devices.
About 60–70% of HAIs are associated with implanted medical devices. These include catheters, artificial hip and knee joints and cosmetic breast implants. It is estimated that over 5 million medical devices or implants are used per annum in the U.S. alone. The worldwide production of biomedical devices and tissue engineering-related materials is estimated to be a $180 billion a year industry and expanding rapidlyxxiii. Regardless of the sophistication of the biomedical implant (i.e. catheters versus an artificial heart valve), all medical devices or tissue engineering constructs are susceptible to biofilm growth and infection.
Other HAIs (10% to 20%) develop following contamination found within the health care environment including; hospital beds, furniture, clothing, toilets, air, water, and healthcare personnel. The contamination of the inanimate environment acts as a reservoir for multidrug-resistant organisms with the risk of HAIs increasing by 73%xxiv,xxv,xxvi. Multiple studies have shown these organisms can persist for weeks and even months in a biofilm, even after a complete disinfection of a room between occupying patients xxvii,xxviii.
1.2 Oral Health
Research over the past decade has recognized that oral plaque and tartar is made up of bacterial biofilms. These biofilms exist on the tooth surfaces both above and below the gum line, the gums, the tongue and the cheeks. Both dental cavities and periodontal disease are the result of damage caused by dental plaque biofilm accumulationxxix. As the biofilm matures and grows, it can penetrate the gums, leading to chronic inflammation and gingivitis (bad breath). Further breakdown of the gums and the diminishing of the jaw bones leads to periodontal disease.
In recent years, studies have shown a connection between periodontal disease and various systemic diseases and conditions, including heart disease, diabetes, respiratory disease, adverse pregnancy outcomes, obesity, pancreatic cancer, and Alzheimer’s diseasexxx,xxxi. This may result from the ability of the oral biofilm to gain access to the circulatory system, leading to inflammation throughout the body.
1.3 Chronic Wounds
Chronic wounds are wounds that are unable to progress through the healing process and can be classified into four categories: pressure ulcers, diabetic ulcers, venous ulcers and arterial insufficiency ulcers. It is estimated that up to 2% of the population in developed countries will experience a chronic wound during their lifetime. In the US, chronic wounds are reported to affect 6.5 million patients costing more than US $25 billion annuallyxxxii.
Over 90% of chronic wounds contain biofilms which act as a constant source of re-infection, preventing healingxxxiii. The current method for removing the biofilm involves the regular removal of all dead and contaminated tissue in the wound, by mechanical, chemical or surgical means. However, this method cannot totally eliminate all biofilm leading to the chance of further infection and longer recovery time.
1.4 Inflammatory Skin Disorders
In the field of dermatology, most inflammatory skin disorders are thought to be due to an autoimmune reaction/ deficiency. However, it has become increasingly evident that biofilms exacerbate symptoms and contribute to the difficulty in treating these chronic skin infections.
Seborrheic dermatitis (SD) is a chronic inflammation of the skin that affects 5% of the worldwide population. It causes scaly patches, red skin, itching and stubborn dandruff. Dandruff is much more common, and affects approximately 50% of the general adult population worldwidexxxiv. In infants, the condition is known as cradle cap and causes crusty, scaly patches on the scalpxxxv. The underlying cause of SD is unknown but thought to be a combination of genetic and environmental factors. It may involve an inflammatory reaction to a proliferation of the biofilm forming yeast malasseziaxxxvi,xxxvii. It has been suggested that this yeast produces toxic substances that irritate and inflame the skin. A 2013 study showed that malassezia biofilms exhibit significantly higher resistance to common antifungals (e.g. ketoconazole, miconazole) than planktonic cells (free floating)xxxviii. Because of this a number of anti-dandruff treatments on the market today do not fully eradicate the biofilm leading to recurrence.
Atopic dermatitis (AD) or eczema is a chronic inflammatory skin disorder that leads to itchy, red, cracked skin. It affects 10-20% of all children and many cases can persist into adulthood as evidenced by the 1-3% prevalence of AD among the adult populationxxxix. The exact cause of AD is unknown but thought to be a combination of genetics and immune dysfunction affecting the permeability of the skin. Many past studies have shown AD patients are colonized with the biofilm-forming bacteria Staphylococcus aureus (S. aureus), with the severity of the disease directly linked to the amount of this bacteria presentxl. The difficulty in preventing S. aureus colonization with conventional antibiotic therapy may be due to the presence of biofilmsxli,xlii.
Athlete’s foot is a common chronic fungal infection affecting the toes and feet and is estimated to affect 15-25% of the worldwide population at any one time. The fungi species Trichophyton rubrum and Trichophyton mentagrophytes are most closely associated with athlete’s footxliii. Both these fungi species have been shown to form biofilms in lab studiesxliv. The ability of these fungi to form biofilms may contribute to the persistence of this infection.
The United States Department of Agriculture (USDA) estimates the costs associated with food borne illness to be about $5.5 billion to $22 billion a year. This doesn’t include the billions lost every year due to spoiled product, which must be disposed of or sold as a lesser valued product. Along with economic problems, biofilm formation on food poses a health risk to consumers due to the ability to make the food more resistant to disinfectants. The Center for Disease Control and Prevention estimated 48 million food borne illnesses per year in the US alonexlv.
The presence of biofilms is common in the food industry. Biofilms can exist on all types of surfaces in food processing plants ranging from floors, walls, pipes and drains, as well as surfaces of equipment including stainless steel, aluminum, nylon, Teflon, rubber, plastic and glass. Food contact surfaces such as conveyer belts, pasteurizers, crevices, gaskets, as well as areas that are hard to clean and sanitize, may harbor biofilms. Also of concern is the potential biofilm formation on food surfaces, which may affect the efficacy of food processing procedures applied to carcasses, meat, produce and other foods, to reduce contaminationxlvi. The presence of biofilm leads to serious hygienic problems and economic losses due to food spoilage. In addition, there are a number of studies on the persistence of pathogens on food contact surfaces (cutting blades, conveyor belts, drains, packaging equipment and storage environment etc.) through formation of biofilm, which cannot be fully removed through use of disinfectantsxlvii,xlviii,xlix,l. Although many species of bacteria are able to form biofilms in the food industry, the most important species in relation to food safety are Listeria monocytogenes, Salmonella spp., Escherichia coli O157:H7, Campylobacter jejuni and Bacillus spp.
Many areas in a household can harbor biofilms including kitchen and bathroom surfaces (counter tops, cutting boards, sinks and faucets, toilets, showers and floors, etc.), as well as kitchen appliances and cleaning tools, such as sponges and dish cloths. Household biofilms are difficult to remove with conventional detergents and can range from bad odors and unsightly dirt and grime to an increased risk of infection and food poisoning. While the most frequent sources of food poisoning are from food service and catering, such as in hospitals and restaurants, the second most common source is in the home.
Past studies have shown kitchen sinks and sponges to harbor large numbers of potentially pathogenic bacteria including fecal coliforms, E. coli, Salmonella, and Campylobacterli,lii,liii. The presence of these bacteria could be attributed to hard to clean biofilm, which acts as a constant source of contamination. In fact, another study demonstrated that cleaning products could only remove as little as 10% of bacteria growing as biofilm on plastic cutting boardsliv.
The results of these studies and an escalation in the outbreaks of food borne diseases has led to the increased realization of the need for disinfectants with anti biofilm activity.