The survival strategies of bacteria in biofilms are highly effective. Nevertheless, scientists have already been able to develop the first preventive measures and control agents in the event of an infestation by biofilms and are continuing to research new possibilities.
One starting point is cleaning medical devices and utensils. So that new germs do not get onto the materials with the water, special sterile water filters are used that hold back all water-bound germs with the help of special membranes.
Anti-sticking coatings
In addition, research is already being carried out on coatings for implants, catheters and the like, which do not even give microbes the chance to colonize and form biofilms. “In order to fight the bacteria, you have to prevent the process of attachment,” says Qun Ren from the Federal Materials Testing and Research Institute.
A research team led by Friedrich Götz from the University of Tübingen has developed a coated surface for this purpose, from which thread-like structures protrude that resemble animal fur. In fact, microorganisms struggled to attach themselves to it in their first attempts. However, when the researchers covered the fur-like surface with blood – in order to simulate the natural environment in the body – a carpet of bacteria grew again because the organisms were able to bind to blood components such as immunoglobulins. However, if Götz and his team treated the bacteria beforehand with immunoglobulins, their receptors were occupied and they could no longer bind to the blood components on the surface.
Nanosilver also inhibits biofilms
An implant coating made of silver nanoparticles has already been successful, at least in animal models: silver is known for its bactericidal effect and in the form of nanoparticles it can work better than silver itself due to the larger surface-to-volume ratio. The biofilm formation by the bacterium Staphylococcus epidermidis could thus be reduced by 95 percent in tests. Researchers at the Leibniz Institute for New Materials have discovered something similar: their antimicrobial, abrasion-resistant coatings with silver and copper colloids kill germs reliably and over the long term and prevent new germs from nesting.
Another research team tested silicone strips to which an antibiofilm surface for medical catheters was applied layer by layer with the help of the enzyme acylase and the molecule polyethyleneimine. In fact, the adhesion of bacteria could be effectively inhibited for up to 24 hours.
Viruses against bacteria
Even if there is already an infestation with microbial biofilms, agents can be used against them. For example phage – viruses that attack and dissolve bacteria. They have a high host specificity, so they can be used specifically against certain microbes and also attack inactive cells, so that the persisters responsible for recurring infections are also destroyed.
The problem: In the case of multiple infections and unknown pathogens, the host specificity of the phages can be disadvantageous. In addition, bacteria can develop resistance to phages or the phages could transfer resistance genes to the bacteria to be controlled. This is why only phages that do not incorporate their genetic material into the bacterial genome can be used for therapy.
Another possibility to destroy existing biofilms has been discovered by researchers working with Xinpei Lu from Huazhong University in Wuhan. They used cold plasmas with a low degree of ionization, which are mostly generated by laser pulses from gas at low pressure. When the high-energy electrons of this plasma hit the molecules in the ambient air, they partially ionize them and produce highly reactive new compounds such as hydroxyl ions. A plasma can generate billions of such free radicals per cubic centimeter. This means that even pathogens in stubborn biofilms can be killed, against which current methods hardly help.
Destroy the matrix
Another starting point is the extracellular matrix of the biofilms. If it is destroyed, the most important protection of the bacteria is lost. One possibility for this is the use of special enzymes.
Dispersin B, derived from Actinobacillus actinomycetemcomitans, is an enzyme that cleaves a matrix component found in certain bacterial biofilms and can dissolve biofilms both in vivo and in vitro. However, the in vivo use of enzymes is not always possible due to potential immune reactions.
Destroying the lectins that hold the bacteria together in the biofilm could also be effective. “Lectins network the components of the biofilm,” explains Alexander Titz from the Helmholtz Institute for Pharmaceutical Research in Saarbrücken. Once separated, the biofilm residents would be vulnerable to the immune system or antibiotics again. Together with his research team, Titz has developed a lectin-blocking molecule that suppresses the biofilm formation of the dangerous germ Pseudomonas aeruginosa. And active ingredients that interfere with quorum sensing, the communication between bacteria, could reduce the stability of the biofilms. Research is already being carried out into funding for this.
Bacteria as a biofilm killer
In addition to these mostly already promising methods, researchers led by Wook Chang from the Nanyang Technological University in Singapore have developed another, unusual strategy against biofilms: They genetically modified harmless intestinal bacteria in such a way that they hunted down deadly Pseudomonas aeruginosa germs.
The researchers constructed the sensors and weapons of the manipulated “helper” from scratch using genetic engineering methods and then implanted them in the intestinal bacteria as carriers. In laboratory tests, these artificially generated “killer bacteria” have proven to be extremely effective and effective against the resistant germs and biofilms.
Home remedies against the germs
Another rather astonishing weapon against biofilms is a medicine from the Middle Ages: It effectively kills pathogenic bacteria such as Staphylococcus aureus and acts against microbial biofilms, as an experiment by Jessica Furner-Pardoe from the University of Warwick and her colleagues has revealed. The amazing thing about it: The thousand-year-old eye ointment consists only of garlic, onion, wine and beef bile. While these ingredients are hardly effective individually, they are unexpectedly effective together.
And yet another home remedy is said to be effective in preventing infections: dark manuka honey is not only highly antibacterial, but research by Bashir Lwaleed from the University of Southampton and his team has even been able to help prevent biofilms. Even a very dilute honey solution reduced the adhesion of bacterial films to plastic and impaired their growth.
–
