A “plastic eating” bacteria discovered in the hospital (and she attacks patients)

The bacteria Pseudomonas aeruginosa is particularly feared in the hospital, because it attacks patients whose immune system is degraded. New works reveal that this dangerous microbe has a major asset to ensure its success: it is able to degrade plastics to feed on it and better persist on the surfaces it colonizes.

Plastic pollution represents one of the major environmental challenges of our time. In recent years, microbiologists have discovered bacteria capable of degrading various types of plastic. One day, these “plastic eaters” microbes could help us reduce the mountains of waste that clutter our discharges and finish in the oceans.

If microorganisms with such capacities arouse hope, they can also, in other contexts, be the cause of serious problems. This is for example the case of one of the strains of the bacteria Pseudomonas aeruginosa that we have identified in the hospital, which is able to degrade certain medical materials.

Plastic eaten bacteria in the hospital

Plastics are widely used in medicine, especially for sutures (in particular absorbable sutures), dressings and implants. We wondered if there could be, in hospitals, bacteria capable of degrading plastics.

To verify this, we have analyzed the genomes of different pathogenic microbes known to be present in hospitals, in order to determine if some of them contained enzymes close to those which are equipped with environmental bacteria capable of tackling the plastic. We had the surprise to see That some hospital microbes are actually equipped with it, which suggests that they could also be able to break down plastic. For example, this type of enzymes has been identified in Pseudomonas aeruginosaa opportunistic bacteriain other words, which becomes dangerous when the immune system is weakened, responsible each year for around 559,000 deaths worldwide.

A large number of infections by this microbe (which result in various ways depending on the location of the infection site : infection of hair follicles, eye, ear, lungs, blood circulation, heart valves, etc.) are contracted in hospital. Patients under artificial ventilation or suffering from surgical wounds or burns are particularly exposed to infections P. aeruginosa. The same goes for those who are equipped with catheters.

After this discovery, we decided to check in the laboratory if this bacteria was actually capable of “eating” plastic.

We focused on a specific strain of this bacteria, isolated in a patient with a skin infection, and having a gene coding for an enzyme degrading plastic. We discovered that it could not only decompose plastic, but that it used it as a nutritious source to grow. This aptitude is conferred by an enzyme that we have named PAP1.

Reinforced biofilms thanks to degraded plastic

Classified among high priority pathogens by the World Health Organization, P. aeruginosa is capable of forming biofilms (bacterial cells adopt an organization in a viscous layer, which protects them from the immune system and antibiotics), which greatly complicates its treatment. Our team had demonstrated in previous works that when environmental bacteria form such biofilms, they can degrade the plastic accelerated.

We then wondered if having an enzyme degrading plastic could strengthen the pathogenic power of P aeruginosa. And we discovered that indeed, bacteria with such an enzyme had increased virulence and formed larger biofilms.

To understand why the biofilm produced by P. aeruginosa was more imposing in the presence of plastic, we analyzed the composition. It turns out that this bacteria is able to incorporate degraded plastic within this viscous layer – or “matrix”, according to the scientific term – using it as a “cement”, which has the effect of strengthening the bacterial community forming biofilm.

Orthopedic implants, catheters, dental implants, “hydrogel” dressings intended for burns … Plastics are omnipresent in hospitals. The fact that a pathogen such as P. aeruginosa Either capable of persisting permanently in a hospital environment could explain its ability to feed on plastic? In our opinion, this is a possibility to consider.

A pathogen capable of degrading plastic of these devices, as that described in our study, could constitute a major problem, compromising the effectiveness of treatment and aggravating the condition of the patient. Fortunately, researchers are already working on solutions, including the incorporation of antimicrobial agents into medical plastics, in order to prevent germs from feeding on them. Furthermore, now that we know that certain bacteria can degrade plastic, this data should be taken into account in the choice of materials intended for future medical uses.

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