As if infection control practitioners (ICPs) and their colleagues didnt have enough to worry about, research is exposing more about yet another foe caregivers must fight: biofilm. Microorganisms attach to living and nonliving surfaces including medical devices and form biofilms that can lead to infection.
Biofilm is the cosmopolite of the bacteria world: comfortable in almost any setting. Most microorganisms subsist in elaborate colonies embedded in biofilms of self-produced exopolymer matrices, and the biofilm allows the microorganisms to adhere to any surface, living or dead.¹ Microorganisms within biofilm adapt readily and are therefore resistant to all known antimicrobial agents. Therefore, strategies which are used to fight acute infections do not work on medical device biofilmrelated infections or chronic biofilm diseases.¹
What It Is
There is much to discover about microbial life, but there is some controversy about how to study it.
Microbiologists often study microorganisms in a liquid homogeneous suspension and plate culture format, which often provides a biased view of microbial life in nature and disease, according to Marcia Ryder, PhD, MS, RN, of Medical Biofilm Research & Consulting, based in Los Angeles.
More recent direct microscopic observations and direct quantitative recovery techniques demonstrate unequivocally that more than 99.9 percent of bacteria grow as aggregated sessile communities attached to surfaces, rather than as planktonic or free-floating cells in liquid, she writes in her paper, Catheter-related infections: its all about biofilm. Microorganisms inside the protected biofilm community are extremely different than when they are in the form of independent cells, which means each should be studied separately.
Most die rapidly when treated with a cidal antibiotic such as ciprofloxacin that effectively kills slow-growing cells, Ryder writes. It is now thought that the presence of a subpopulation of persister cells within the biofilm may account for the profound resistance to complete eradication of biform bacteria. Persisters are phenotypic variants of wild-type cells that neither grow nor die in the presence of bactericidal agents and that exhibit multi-drug tolerance.
Why Its Dangerous
Microbial biofilms are often formed by antimicrobial-resistant organisms and are responsible for 65 percent of treated infections in the developed world.¹ Some chronic biofilm-related diseases are: cystic fibrosis, endocarditis, otitis media, prostatitis, chronic wounds, tonsillitis, peritonitis and Legionnaires disease.
A terrible Catch-22 is that medical devices are necessary in medical care, and yet they are big contributors to illness and mortality, mostly because of their propensity to carrying biofilm.¹ Biofilm is a disease that affects as much as 80 percent of infectious diseases such as chronic wounds, cystic fibrosis, COPD, endocarditis, pressure ulcers, etc., Ryder says. Virtually all medical device-related infections and healthcare-associated infections (ventilator-associated pneumonia, for instance) are biofilm diseases. Added up, this involves billions of patients, billions of dollars and hundreds of thousands of deaths, more than cancer and heart disease.
Our current methods of diagnosis and treatment are based on bacteria existing as single cells in a laboratory media, she adds. This approach is in error as biofilm bacteria living in highly protected and cooperative communities are genetically different, profoundly resistant to therapeutic doses of antibiotics and are capable of rapidly increasing antimicrobial resistance.
Every healthcare worker needs to understand that biofilm develops on just about every surface you can imagine, and certainly within the plumbing of every healthcare institution, says Joseph Cervia, MD, FACP, FAAP, clinical professor of medicine and pediatrics at Albert Einstein College of Medicine; medical director and senior vice president of the biomedical division at Pall Medical.
What we can do at this point is to prevent to the passage of the organisms that exist within that biofilm, Cervia says. Aeresolization of organisms happens considerably in sinks at bedside.
Biofilm reaches patients in several other capacities as well, and all these ways can spur illnesses.
Education and Research
A majority of healthcare workers have limited or no knowledge of biofilm; however, some have a piqued interest and are seeking more information, Ryder says.
If we do not direct our research efforts at the microbial level, we will continue to experience the exorbitant rates of infections despite our increased but waxing and waning efforts at surveillance and prevention, Ryder adds. Bacteria are winning the battle and are getting stronger, as scientists are unable to produce efficacious antibiotics fast enough.
Understanding the epidemiology of disease is very important but we need to focus less on counting the problem and increase efforts at new methods of prevention, diagnosis and treatment based on the science behind biofilm microbiology, Ryder says.
The infection control and infectious disease community needs to embrace the science of biofilm disease themselves, direct research dollars to this area, and focus on the translation of the science into more effective clinical practices, she adds.
Education is always the first step, according to Cervia.
If one doesnt even realize that biofilm exists in plumbing everywhere, then one is going to be a long way from being able to protect patients who are more vulnerable, he says.
Water: Friend or Foe?
Another irony: healthcare facilities and patients cannot function without water, and yet water itself can carry the biofilm that breeds illness.
Fortunately, biofilm can be removed and destroyed by physical treatments such as hot water (greater than 80 degrees Celsius) and mechanical scrubbing. Biofilm can also be compromised by chemical biocides, most of which are either oxidizing or non-oxidizing.² Chlorine is an oxidizing biocide and is likely the most effective and inexpensive, according to the paper, The key to understanding and controlling bacterial growth in automated drinking water systems.
The paper states that chlorine works against planktonic and biofilm bacteria, and also destroys the polysaccharide web and its attachments to the surface. By destroying the extra-cellular polymers, chlorine breaks up the physical integrity of the biofilm.
Other non-oxidizing biocides are chlorine dioxide and ozone, both of which fight biofilm in similar fashions (though ozone is twice as powerful as chlorine). Both are unstable though, and must therefore be prepared on site. Systems that use ozone must be made with ozone-resistant materials.²
Non-oxidizing biocides are quaternary ammonium compounds (quats) and formaldehyde. Quats often require exhaustive rinsing from purified water systems, however, and formaldehyde is toxic. Formaldehyde is relatively noncorrosive to stainless steel, but its effectiveness against biofilm is questionable.²
Biofilm is a major concern in all water sources be it potable water in third world countries, ice machines in convenience stores, hemodialysis water lines, dental unit water lines, etc. Ryder says. It is the immunocompromised patients that are at the most risk. We are only beginning to understand the ramifications of biofilm sources in healthcare facilities bath basins and nosocomial infections, for example.
Material and surface has little or no affect on biofilm development, which means stainless steel is as vulnerable as plastic. Pipe material to which microorganisms cannot adhere is not yet known.²
One of the reasons why purified-water systems are so prone to biofilm is the large surface area of the tanks, piping systems, etc., needed to store and carry water. These industrial systems have a huge amount of surface area on which bacteria can adhere, whereas natural environments such as lakes and rivers do not provide as many risky surfaces.²
The risks of water in the healthcare environment are substantial, Cervia says. Water is traditionally looked upon as an ally in the fight of infection, but it can also be a vehicle for transporting very pathogenic microbes to the point of care, he says.
High profile examples include Legionella.
Other organisms that are known to be water-associated organisms are seen in healthcare institutions every day, Cervia adds. Hospitals are just now recognizing the need to take precautions beyond hand washing in reducing (infections). There needs to be an understanding of the risk posed by biofilm in hospital water systems and the need to protect patients by preventing exposure to biofilm-born microorganisms at the point of use.
The problem is pervasive and vast.
I would say that in hospitals across the countries today we are seeing large numbers of infections related to waterborne pathogens, and biofilms play a major role in the epidemiology and pathogeneses of these infections in healthcare institutions, Cervia says. This is really a relatively under recognized problem taking proper precautions.
Cervia believes that healthcare decision-makers are only very recently understanding the measures they can take to protect and treat their water systems.
I dont believe we are doing everything we can at this point, he says. For example, the number of hospitals that use point-of-use filters (which can make water safer) in critical care units, bone-marrow transplant units, chemotherapy units and other units wherein vulnerable patients are cared for, those numbers are nowhere near where you would expect. There is an emerging recognition of the role that waterborne organisms play in infections and particularly infections to hosts who are at high risk.
A potential solution is to install 0.2 micron filters at the points of use including showers, faucets and ice machines.
Catheter Culprits and Other Devices
A few of the catheters associated with biofilm include: urinary, central venous, pulmonary and umbilical arterial.
In order to attach and colonize, a microorganism must make direct contact with the catheter.
The mere touch of the cell wall with the biomaterial alters the microorganisms phenotypic expression to begin production of a sticky adhesion that attaches the cell to the surface, Ryder writes.
The first time this can happen is when the catheter is inserted and makes contact with transient and resident microorganisms that are on the surface of the skin.
Roughly 80 percent of resident microorganisms inhabit the first five cell layers of the stratum corneum.¹ The following implants are also risky: middle ear, breast, penile, spinal, dental, as well as pacemakers, etc. Other devices inclined to biofilm are mechanical heart valves, coronary stents, intraocular lenses, contact lenses and suture material.
Microorganisms can enter a flow system through any access portal or connection site unless the site is disinfected. Attachment can occur once the microorganisms are inside and make contact with any internal surface component of the administration, such as extension tubing, needleless connector, hubs, or the conditioned or unconditioned catheter.¹ Even at this point, damage can be mitigated. If left too long, however, catheter-related bloodstream infections (CRBSI) can wreak havoc. Therefore, they must be diagnosed early.
CRBSI is not diagnosed early and often enough which stems from the lack of understanding of the disease, Ryder says. As above, our methods of diagnosis are not based on biofilm science. We continue to rely on peripheral blood cultures that reflect individual bacteria cells floating in the bloodstream (bacteremia) but do not measure the presence of biofilm associated with the catheter as the source of the bacteremia.
The best method currently available is the time-to-positivity blood culture method but it is not well understood and probably not widely used despite the strong data to support it, Ryder adds.
The most common clinical signs of CRBSI are fever, chills, inflammation at the catheter site, and hypotension when no apparent source of infection besides the catheter is present.¹
The Industry Responds and Doesnt
The implant market is growing rapidly, and with that growth the chances for device-related biofilm complications rise. Manufacturers have been paying more attention to the issue of biofilms on implantable medical devices, Cervia says.
Manufacturers are looking at ways of impregnating devices with antimicrobial substances, he says. Silver and other coatings are being explored. Hospital staffs are doing a good job focusing on proper hygiene and infection reduction practices, but could take more precautions against biofilm contaminants in drinking water systems, Cervia states.
I believe that up until now the types of precautions that healthcare institutions have been appropriately advocating in reducing infection rates in the hospitals revolve around hand washing, he says. Hand washing is certainly a critical component to infection control and nothing can take the place of that.
However, far more needs to be done.
There are many systemic treatment technologies that healthcare intuitions are utilizing, Cervia says. it varies from institution to institution. If you survey institutions individually, youll see that some employ no systemic water treatment technologies; others will use copper, silver, ironization, or hot water flushes periodically. These are all techniques that some institutions will employ at least from time to time to try to reduce the bio-burden of organisms in their water systems.
The problem with all these techniques is that they are limited in the extent to which they can provide uniform exposure of the biofilm bacteria to the toxic substances in the systemic treatment technologies without interfering with water quality, he adds. These technologies are certainly other important steps.
The first step that can be taken right now is for institutions to educate their personnel, including facilities managers, ICPs and administrators, to make them more aware of the risks posed by biofilm. The next step is to implement solutions such as point-of-use filtration, particularly where the most vulnerable patients are, Cervia says.
There are technologies that are being looked at to limit the growth of biofilm on surfaces, he says. Its not something that youll be able to implement tomorrow, but in the future there will be materials that will be more resistant to the growth of biofilm on surfaces and will leave some of those surfaces less vulnerable.
For information on water treatment solutions from Pall Medical, call: 1-800-645-6578.
1. Ryder M. Catheter-related infections: its all about biofilm. Topics in Advanced Practice Nursing eJournal. August 2005.
2. Dreeszen P. The key to understanding and controlling bacterial growth in automated drinking water systems, second edition. June 2003.