Screening clinical isolates for plastic-degrading capacity may help improve infection control strategies and medical device safety.
A clinical strain of Pseudomonas aeruginosa has been found to degrade a common medical plastic, use it as a carbon source, and enhance its biofilm-forming ability.
“Being able to utilize plastic as a carbon source may enable pathogens to persist within the host or the hospital-built environment for prolonged periods under nutrient-limiting conditions,” reported Sophie A. Howard from Brunel University of London, and colleagues.
The strain, named PA-W23, was isolated from a wound and shown to break down polycaprolactone (PCL), a biodegradable polymer used in sutures, wound dressings, drug delivery systems, and 3D-printed implants. Researchers identified a gene in the strain, pap1, which encodes the plastic-degrading enzyme Pap1.
In laboratory experiments, PA-W23 degraded 78.4% of PCL within 7 days and grew using PCL as its sole carbon source. “This enzyme had 87% query cover and 61.76% identity to the previously characterized polyester-degrading enzyme PET5,” noted investigators.
Pap1 was confirmed to be secreted via the type II secretion system, a common protein export pathway in pathogens.
Further tests showed that exposure to PCL significantly increased biofilm formation—an important mechanism of antibiotic resistance and persistent infection. Deletion of pap1 significantly reduced plastic degradation and biofilm formation, both of which were restored upon complementation.
Biofilms are protective bacterial communities that help shield microbes from antibiotics and immune responses. In PA-W23, biofilm levels increased by over 85% in the presence of PCL, but only when pap1 was intact. Control strains unable to degrade plastic showed no such increase, confirming that plastic degradation drives biofilm enhancement.
To assess potential clinical relevance, researchers implanted PCL into wax moth larvae and infected them with PA-W23. Larvae with implants died more frequently, indicating increased virulence in the presence of plastic. This effect was absent in strains lacking pap1 or plastic-degrading ability.
Chemical analysis identified 6-hydroxyhexanoic acid (6OH-HA), a PCL degradation byproduct, embedded in the biofilm matrix. Its presence stabilized and strengthened the biofilm. When 6OH-HA was added directly to the bacterial culture, it further enhanced biofilm formation.
The researchers also screened additional P. aeruginosa clinical isolates and found another strain with similar plastic-degrading and biofilm-promoting traits, suggesting this may be a broader phenomenon.
Given the widespread use of plastic-based devices in health care, the findings highlight a potential under-recognized risk: that some medical plastics may inadvertently support the survival and virulence of opportunistic pathogens.
Screening clinical isolates for plastic-degrading capacity, particularly in device-associated infections, may help improve infection control strategies and medical device safety.
Author disclosures can be found in the published study.
Source: Cell reports
