A further concern has been added to the considerable tally of issues relating to microplastics dispersed in the environment. This relates to the role that plastic particles can play in terms of spreading antibiotic resistance.
Antibiotic resistance is a global health problem that has bedevilled our health sector worldwide, affecting both the developed and developing countries of the world.
This relates to new research, from Rice University, that has looked at how chemical-leaching plastics affect bacteria in different ways, including enhancing resistance. The primary concern is with polystyrene, which like other plastics does not biodegrade but instead fragmentizes into smaller fractions.
This arises, as the research has identified, because free-floating genetic materials (that provide bacteria with resistance) are also found in association with plastic particles. Hence, the plastic particles act as vehicles for spreading antimicrobial resistance amongst microbial populations.
The genes are protected by bacterial chromosomes, bacteriophages and plasmids. In turn, these act as biological vectors.
As chemicals leach out from a particle of plastic as it ages (via depolymerization), this serves to increase the susceptibility of the vectors to horizontal gene transfer – this is the primary method by which resistance spreads between microbial cells and between cells and genetic material.
One reason for the aging factor risk is that as plastic is aged by exposure to the ultraviolet part of sunlight, this alters the surface and makes it easier to trap microbial cells. These altered surfaces serve as aggregation sites for susceptible bacteria. Furthermore, the mass of plastic substrates promotes attachment of and subsequent biofilm production by microbes, thereby increasing the community size overall by attracting more microorganisms into the community.
The study forms part of efforts to characterize microplastics based ecosystems (the so-termed “plastisphere”) together with and their antimicrobial resistance promoting elements (including traces of antibiotics, heavy metals, and microbial inhabitants).
Chemicals from the plastics can also later the microbial cells, making it easier for generic material to enter the cells, and this can be a mechanism to boots resistance. Since this generally occurs under conditions where there are no antimicrobials present, there are not direct challenges to microbial populations thereby allowing resistant genes to be shared more widely.
The research appears in the publication Journal of Hazardous Materials, with the research titled “UV-aging of microplastics increases proximal ARG donor-recipient adsorption and leaching of chemicals that synergistically enhance antibiotic resistance propagation.”
