Nanoplastics derived from single-use plastic bottles (SUPBs) contribute to the spread of antibiotic resistance (AR), shows a new study, underscoring an unrecognized public health risk.

The joint threats of plastic pollution and antibiotic resistance are growing concerns. Nanoplastics and microorganisms coexist in diverse environments, including the human gut.

This problem led scientists from Institute of Nano Science and Technology (INST) Mohali, an autonomous institution of the Department of Science and Technology (DST), to trace how plastic nanoparticles could impact bacteria. Recognizing the central role of Lactobacillus acidophilus in the gut microbiota, Dr. Manish Singh and his team investigated whether nano-plastics could transform beneficial bacteria into carriers of AR genes and pose a risk to human gut microbiome health.

They utilized the used plastic water bottles to synthesise environmentally relevant nanoplastics particles as these polyethylene terephthalate bottle-derived nanoplastics (PBNPs) better represent the actual pollutant nanoplastics generated due to dumping of single use plastic bottles and containers.

The scientists demonstrated that PBNPs can facilitate the cross-species gene transfer from E. coli to Lactobacillus acidophilus, a significant bacteria found in human gut microbiota, through a process called horizontal gene transfer (HGT), particularly through outer membrane vesicle (OMV) secretion in bacteria.

According to the researchers there are two novel mechanisms through which PBNPs facilitate AR gene transfer. One of them is through direct transformation pathway in which PBNPs act as physical carriers, transporting AR plasmids across bacterial membranes and promoting direct gene transfer between bacteria. The other one is through OMV-Induced Transfer Pathway in which PBNPs induce oxidative stress and damage to bacterial surfaces, which makes stress response genes pro-active and triggers an increase in outer membrane vesicle (OMV) secretion. These OMVs, loaded with AR genes, become potent vectors for gene transfer across bacterial species, thus facilitating the spread of AR genes even among unrelated bacteria. This reveals an important and previously overlooked dimension of nanoplastics' effects on microbial communities.

The study published in the journal ‘Nanoscale’ highlights how nanoplastics might unexpectedly contribute to the AR crisis by introducing AR genes to beneficial gut bacteria like Lactobacillus acidophilus, which may subsequently pass these genes to pathogens. It indicates that beneficial bacteria like Lactobacillus acidophilus could act as reservoirs for AR genes, potentially transferring these genes to pathogenic bacteria during the course of infections.

Protecting beneficial gut bacteria is crucial for immune support, digestion, and disease prevention. Limiting nanoplastic contamination could help preserve gut microbiota integrity, minimizing the chances of AR gene transfer from beneficial to pathogenic bacteria and supporting microbiome resilience.

With increasing plastic pollution, this finding highlights the need for strict safety guidelines, awareness programs as well as the necessity of policies that prioritize responsible usage of plastics and it’s adequate waste management to safeguard the human health and microbiome stability.

Publication link: https://pubs.rsc.org/en/content/articlelanding/2024/nr/d4nr02613f