Biofilms and Healthcare
By David W Koenig, PhD., EAS Consulting Group Independent Consultant
Healthcare facilities — such as hospitals, nursing homes and outpatient facilities — are opportunistic locations for acquiring secondary infections unrelated to a patient’s primary condition. Healthcare-acquired infections (HAIs) are a primary concern for healthcare providers, administrators, and governments worldwide due to the reduced quality of healthcare and the considerable associated socioeconomic costs resulting from extended hospital stays for infection treatment.
Some of the most common HAI types occur during the use of in-dwelling medical devices, such as a catheter, endotracheal tube, feeding tube or prosthesis. According to the Centers for Disease Control and Prevention (CDC), the most common underlying cause of infections related to in-dwelling medical devices is the ability of microorganisms to adhere to the surface of devices and form biofilms. Biofilms are often associated with tissue infections such as chronic wounds, skin infections, endocarditis, chronic otitis media and cystic fibrosis.
Biofilms are a gathering of microbes that colonize various surfaces. Many biofilms are beneficial. The beneficial human microbiome consists of diverse biofilms on the skin, teeth and mucosa of the gut, nasal, and reproductive organs; however, if a biofilm contains pathogens, these biofilms can become a severe concern for healthcare facilities, leading to HAIs.
The aspect of most concern is increased resistance to antimicrobials and antibiotic therapy; because of this concern’s broad acceptance that the most effective way to reduce the incidence of medical device-related infections is to prevent primary microbial adhesion and subsequent biofilm formation.
Biofilms produce an extracellular polymeric substance (EPS) that protects the microbes in the biofilm. EPS interferes with the penetration of antibiotics or antimicrobials through the biofilm. EPS interference is compounded by the cells in the biofilm having an altered physiology that further protects those cells from any antimicrobial that might penetrate the biofilm. Biofilms also provide the microbes with an environment that allows cell-cell communication and quorum sensing and enhances the transfer of genetic elements and resistance genes. Indeed, biofilm bacteria can transform into a persistent state that mimics a spore. Ultimately, biofilms increase the prevalence of antibiotic-resistant microbes and the risk of transmission to the caretaker and patient.
Healthcare environmental biofilms can act as reservoirs for the transmission of pathogens. Biofilms are commonly associated with surfaces that remain wet; however, a biofilm cover surface does not necessarily have to appear watery to the eye for a biofilm to persist. Recently, dry surface biofilms have been receiving extensive study. Dry surface biofilms form an exterior veneer while the surface is wet and then dry when the moisture dissipates. Biofilm EPS plays a critical role in the persistence of a dry biofilm allowing the retention of enough water for sustained survival. Biofilm “hot spots” can include drains, sinks, plumbing connections, areas of toilets that remain wet and not cleaned with mechanical action, bathrooms, sink traps, air filtration mediums, window ledges and seals, air conditioning systems, fabrics, – carpets and rugs. Dry surface biofilms develop on various surfaces, such as blood pressure cuffs, intravenous poles, door handles, touch screens, and cell phones. Dispersion of cells from biofilms can perpetuate microbial resistance, recurrence, and transmission of dangerous pathogens in the healthcare environment.
The types of microbes associated with biofilms are very diverse. The most common bacteria associated with hospital device-related infections is Staphylococcus epidermidis. Other hospital biofilm bacteria are methicillin-resistant Staphylococcus aureus (MRSA), viridans streptococci, Enterococcus faecalis, vancomycin-resistant Enterococci (VRE), Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, Proteus mirabilis, and Klebsiella pneumoniae. Recently, the fungi Candida auris has emerged as a critical biofilm-associated pathogen. Other medically associated fungi that form biofilms are Aspergillus, Cryptococcus, Trichosporon, Coccidioides, and Pneumocystis— furthermore, human viruses and bacteriophages are present in biofilms.
Control of biofilms is complex. For device-related biofilms, various prevention strategies are initiated. One process is to impregnate the device with leachable antimicrobials such as silver. Another is to coat the surface with anti-adherents that interfere with the initial attachment of the microbe to the surface, interfering with the 1st step of biofilm formation. There is also the possibility of imprinting micro-patterns on surfaces that inhibit biofilm formation. These tactics have allowed various levels of protection from biofilm formation on devices. Removing biofilms from animate surfaces commonly involves mechanical methods such as water jets and sonic disruption, widely found in dental cleaning.
Prevention and removal of biofilms on inanimate environmental surfaces are just as challenging. The biofilm is often on a surface that is hard to reach or in a dead leg within a water system. Cleaned and disinfected surfaces contiguous to the contaminated area can be readily re-contaminated by biofilm dispersion leading to a transmission hot spot. A strategy to help reduce surface recontamination is to employ a persistent antimicrobial. For example, copper-containing materials, such as bed rails, have prevented biofilm formation. Using a residual disinfectant may also be an excellent option to reduce the recontamination of a surface.
Biofilms are inherently resistant to chemical disinfectants; therefore, mechanical and chemical methods are usually employed to effectively treat environmental biofilms. Mechanical methods may include abrasive scrubbing, high-power sprays and jets, and sonic cleaning, to name a few. Strong oxidants such as peracetic acid are good candidates for treating biofilms, although insufficient evidence exists to distinguish between product performance and biofilms. Recently, there has been a trend for disinfectant manufacturers to evaluate disinfectant performance against biofilms. Additionally, if the biofilm matrix or dead cells remain on a surface after cleaning, biofilms will form faster than surfaces free of the contaminating material. Removal of the biofilm matrix after disruption on surfaces points out the importance of removing biofilm debris as a prophylactic for future biofilm control.
Healthcare biofilm control is a cornerstone in reducing antimicrobial resistance and making a significant dent in HAIs. Everyone involved in cleaning must better understand and grasp the types of disinfectants required to control healthcare biofilms. Therefore, more effort is needed in all these knowledge areas to help healthcare practitioners and caregivers develop efficient approaches to identify, prevent, and remove biofilms.
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