Doctors often deal with bacterial infections, but they are less familiar with infections involving several different kinds of bacteria in a matrix. This form, known as biofilm, is surprisingly common, resistant to many antibiotics, and gaining new attention as a source of hard to eradicate infections. Experts discuss.
- Dr. Phil Stewart, Professor of Chemical and Biological Engineering, Montana State University
- Dr. Randall Wolcott, Medical Director, Southwest Regional Wound Care Center, Lubbock, TX
- Bill Soukup, President, Scientific Biofilm Solutions and Healthy Household Cleansers
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Reed Pence: Disinfectants are big business. Even though we couldn’t live without the trillions of bacteria living inside our bodies, we try to get rid of them everywhere else whenever we can. But we’re learning that that’s a tougher job than we thought. Scientists are changing how they think about bacteria.
Dr. Phil Stewart: And the changes goes from thinking about primitive single-celled organisms that live insolation and are just floating around at the whim of the currents, to thinking about these as multicellular structures in which microbes are communicating with each other through the metabolites that they secrete, that they’re probably cooperating metabolically, that there are divisions of labor strategies.
Pence: That’s Dr. Phil Stewart, professor of chemical and biological engineering at Montana State University. He says what’s prompted scientists to upgrade their estimation of bacterial communities is something called biofilm. Montana State’s Center for Biofilm Engineering is one of the world’s leading biofilm research centers.
Stewart: Biofilms are microorganisms – we’re talking about bacteria or yeast, for example, that are banded together in dense aggregates, usually stuck to a wetted surface. So, a classic example is dental plaque most of us confront daily with our toothbrushes. If you’re out for a hike and cross a little stream and slip on a slimy rock, that was a biofilm, probably a mixture in that case of microalgae and bacteria living together in symbiotic relationship. So this turns out to be very very common. We would say even ubiquitous ancient survival strategy for microorganisms.
Dr. Randall Wolcott: People deal with biofilm everyday. When they’re scrubbing, when they’re using chemicals, more often than not they are dealing with biofilm. So it’s the ring in the toilet, it’s the ring in the tub, it’s the plaque on our teeth, the things on the counter, or things in the sink. So whenever there’s a nutrient source, a little bit of water, bacterial will adhere to the surface. Once they are attached they grow quite differently from what we learned about in our science classes in school.
Pence: Dr. Randall Wolcott is medical director of the Southwest Regional Wound Care Center in Lubbock, Texas, one of the few wound clinics that focuses on biofilm and infections.
Wolcott: They secrete a substance around themselves; they incorporate substances from around them and they weave this tight matrix around themselves to protect themselves. So they are quite different. Think of the plaque on your teeth…you don’t take antibiotics to cure those. Those antibiotics can help, but mainly it’s brushing and putting topical things on them to suppress it. You don’t get rid of them. You keep them knocked down so they don’t cause cavities and periodontal disease and stuff like that. So people really deal with biofilms everyday of their life. They know the strategies for dealing with those bacteria; they’ve just never known to call them biofilm.
Bill Soukup: I think Harvard did a study that about 100,000 people in the United States died per year from biofilm related illnesses. And now these appliances that people have, for example like a dishwasher, you have the slime or the contamination build up inside a dishwasher.
Pence: Biofilm inside your house is an important issue, too, according to Bill Soukup, president of Scientific Biofilm Solutions and Healthy Household Cleansers, which make products designed to attack biofilm and the substances that help them grow.
Soukup: And it’s not just biofilm with our cleaners, we’re trying to remove other contamination too. Like the dishwasher would be fats and oils, food deposits, scale and other build up that builds up inside the dishwasher, and they don’t get hot enough to kill or remove biofilm. The backside of a washing machine is full of all kinds of contamination of biofilm, which is the slime on the backside of say a drum in a washing machine. The biofilm absorbs the contamination, then feeds off this contamination. So you have dirt and oils and fecal contamination that are feeding the biofilm, then that’s what’s keeping the bacteria alive on the backside of the drum and inside the washing machine, so that’s what needs to be removed.
Pence: Stewart believes biofilms in household appliances are less of a health hazard unless someone’s immunity is compromised. But he says biofilm slime… the matrix holding everything together… can certainly be unpleasant and then some.
Stewart: It’s a watery hydro gel made of proteins, polysaccharides, even nucleic acids. So not only are there microbial cells, but there’s this matrix surrounding them that they have exported and that matrix offers some degree of protection, just immediately, it offers some mechanical protection. So it’s harder to tear that structure down than it is just a lone cell.
Pence: However, lone cells are what most scientists study. Bacteria in the lab don’t live like those in real life. In the lab, they float freely with nothing to stick to and with plenty of food, so they have no reason to form a matrix. But grouped together as biofilm, bacteria have plenty of advantages that haven’t been studied all that well.
Stewart: One of those is that the ones in the center of a biofilm can become starved for nutrients and stop growing. That turns out to be a great way to defeat an antibiotic. So most of our antibiotics target actively dividing microorganisms. If some fraction of the population in a biofilm for example, simply stops growing, they can outlast an antibiotic treatment. The other big protective mechanism is that the antimicrobial chemical doesn’t actually penetrate all the way in.
Pence: Stewart says big numbers provide one other defense — most biofilms are made up of more than one kind of bacteria. So an antimicrobial attack on one or two types won’t touch some of the others.
Stewart: Very often in these real world biofilms systems we find a whole zoo of different microorganisms living together in the same biofilm. So for example, hundreds of different species of bacteria have been isolated from human dental plaque. It’s a rather fabulous mixture of organisms with very different properties that live together in close proximity.
Pence: Given all those defenses that biofilms have it’s no wonder that it can be extremely difficult to get rid of them. Washing machines and dishwashers are one thing, but a biofilm infection in the human body can be extremely serious. Yet medicine is only beginning to catch up with the discovery that biofilms and infections are closely related.
Wolcott: The European Infectious Disease Society says that if you get those chronic infections that it’s biofilm that’s causing those infections, which means every tissue of the body suffers a chronic infection. In the heart valve, it’s endocarditis, in bone it’s called osteomyelitis on skin it’s called a chronic wound. So that’s biofilm that drives that. There are host factors, but at the end of the day a chronic wound in a chronic infection.
Stewart: It now looks like diabetic foot ulcers, venous stasis ulcers, decubitus ulcers are bed sores, very often involve a polymichrobial, a mixed species biofilm growing in the damaged tissue of that wound and setting up this stalemate or standoff in which the biofilm is present and defended and can’t easily be eradicated by topical antiseptics or host defenses, yet the presence of the biofilm at the same time is arresting the normal healing process. These are sores that can stay open for weeks or months or even years; they are really tragic for the patient.
Pence: But chronic wounds aren’t the only place where biofilm infection is especially troublesome. Stewart says implants are also prone to infection.
Stewart: These are typically slow moving, but very persistent infections, and they tend to be associated with implanted devices or tissue that is damaged somehow. For example, prosthetic joints or artificial hip has a certain risk of developing an infection, that’s directly associated with the implant and it’s only about one percent of people who end up with that problem, but it’s actually a rather catastrophic problem if your hip gets infected. It’s a huge expense and trauma to the patient to deal with a hip joint that becomes infected, or a knee joint. Same goes for catheters, hernia meshes and there are so many biomaterials that are used in medicine these days, they all have a risk of an infection.
Pence: Still, Wolcott says biofilms are a hard sell to doctors. Most of them don’t really know much about biofilm, and the normal medical world can make it a hard concept for them to grasp.
Wolcott: We’re still steeped in the “one thing causes the infection and everything else is a contaminant.” So that’s the thing we run into when we try to talk about biofilm with clinicians. It’s like they’ll say, “You’re naming four or five different organisms, which one’s causing the infection?” That’s hard to get across. Used to you’d get a staph aureus report back from your culture. The culture reports one thing, you treat the one thing. If you get five, six, seven different microorganisms that you’ve never heard of before, it makes it more difficult for your treatment decisions. So they’ve been very resistant to that.
Pence: But when doctors embrace the concept that treatment will have to be a little different than how they’d combat a single organism, Wolcott says they can have much more success.
Wolcott: We did a, it was four months. We identified 93 inpatients that were told that they had to have their limb amputated for ulcers. The vast majority were diabetic foot ulcers, there were four or five venous leg ulcers, but they were recommended by there treating physician to have a major limb amputation either below or above the knee. They all healed but three. So we were successful in cases where the treating physicians that had them before thought that they were at the end of their road and they could never heal.
Pence: Wolcott says the key to treating biofilm infection is the realization that more than one approach is necessary. At first, the strategy was almost dental—brushing to get rid of the biofilm… then topical antiseptics to prevent it from coming back. Over time, those multiple strategies may become more and more important in medicine, as we learn more about the importance of inflammation and biofilm in many human diseases.
Wolcott: You can’t overstate the problem. If you look at cancer, 25% of cancers are caused by persistent inflammatory conditions like colon cancer and stomach cancer. And now stomach cancer is directly linked to bacteria. The H. pylori causes most stomach cancers. So bacteria, this biofilm type bacteria with its persistent inflammation can cause a significant amount of the cancer that we see in the United States. Atherosclerosis looks like it’s going to be a biofilm disease — that’s heart disease and perivascular disease. So that’s big. But if you take that out, if you just look at the chronic sinus infections and Crone’s disease and chronic Prostatitis and ventilator acquired pneumonia, and infected medical devices, it’s well over 10 million, probably closer to 20 million Americans suffer from most chronic infections. That’s all biofilm disease.
Pence: You can find out more about all our guests through links on our website, radiohealthjournal.net, where you can also find archives of our programs. You can also find them on iTunes and Stitcher.
I’m Reed Pence.
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