Microplastics and the Impact on Healthcare

Environment, Energy, & Related News from the Week ending March 15th, R.J. Sigmund.

Two interesting articles on microplastics in healthcare and the environment.

– Microplastics contribute to evolution of antimicrobial resistance, study finds, University of Minnesota

A new study by researchers at Boston University indicates microplastics in the environment might facilitate antimicrobial resistance (AMR).

The Applied and Environmental Microbiology study added new concerns about the role of the small (<5 millimeters in length) pieces of plastic. They are are ubiquitous in the environment and play in promoting the emergence and spread of drug-resistant bacteria. Previous studies have shown how microplastics can serve as vehicles on which bacterial communities can form and share resistance genes. This study suggests there’s an interaction occurring between the microplastics and bacteria that influences the development of AMR.

“This challenges the notion that microplastics are merely passive carriers of resistant bacteria and highlights their role as active hotspots for antimicrobial resistance evolution,” lead study author Neila Gross, a Boston University PhD candidate, said in a press release from the American Society for Microbiology.

To investigate the interaction between bacteria and microplastics, Gross and her colleagues exposed  Escherichia coli bacteria grown in liquid media. Each type was in varying concentrations of different sizes and types of microplastics. The study included polyethylene, polystyrene, and polypropylene, until biofilm growth was detected. They then added subinhibitory levels of four different antibiotics commonly found in the environment—ampicillin, ciprofloxacin, doxycycline, and streptomycin. They then tested for antibiotic susceptibility every 2 days.

For comparison, the researchers tested antibiotic susceptibility in E coli grown without exposure to microplastics. They also measured the minimum inhibitory concentration (MIC, the amount of antibiotic needed to kill bacteria) in cells grown with a single subinhibitory antibiotic with or without microplastics.

Within 10 days, they found that exposure to microplastics led to increased resistance to all four antibiotics compared with E coli grown in liquid media without microplastics. Researchers wrote:

“Our results suggest that the addition of MPs [microplastics] led to an increase in AMR for nearly all antibiotics. In each case where bacteria were grown and tested in the same antibiotic. The addition of MPs to antibiotics in the media led to an MIC increase of at least five times more compared to cells grown in the antibiotics alone.”

Furthermore, when the antibiotic exposure was halted and the bacteria were grown in antibiotic-free media for 5 days, the E coli that had been grown with antibiotics and microplastics retained the same resistance level, and some even gained resistance. Additional analysis showed that E coli grown with concentrations of polystyrene developed higher levels of resistance compared with polyethylene and polypropylene.

“Our findings reveal that microplastics actively drive antimicrobial resistance development in E. coli, even in the absence of antibiotics, with resistance persisting beyond antibiotic and microplastic exposure.”

Gross said. Gross and her colleagues say the findings are important because global plastic use has risen 20-fold since 1964 and microplastics have infiltrated ecosystems throughout the planet. At the same time, there is increased recognition of the role that environmental contamination from antibiotic residues, particularly in wastewater in low- and middle-income countries, plays in the spread of AMR.

As a result, they argue, the role of microplastics in AMR development makes them both an environmental and public health threat. In particular, they suggest that understanding how microplastics, bacteria, and antibiotics interact in low-resource countries—where infection rates are high, wastewater treatment is poor, and there is significant plastic waste—could be critical for efforts to address the growth and spread of drug-resistant pathogens that pose a threat to human health.

– Medical infusion bags can release microplastics, Medical Press 

Microplastics have been found almost everywhere that scientists have looked for them. Now, according to research published in Environment & Health, these bits of plastic—from 1 to 62 micrometers long—are present in the filtered solutions used for medical intravenous (IV) infusions. The researchers estimate that thousands of plastic particles could be delivered directly to a person’s bloodstream from a single 8.4-ounce (250-milliliter) bag of infusion fluid.

In clinical settings, IV infusions are packaged in individual plastic pouches and deliver water, electrolytes, nutrients or medicine to patients. The base of these infusions is a saline solution that contains filtered water and enough salt to match the content of human blood. Research from the 1970s suggests IV fluid bags can contain solid particles, but few scientists have followed up on what those particles are made of.

Researchers Liwu Zhang, Ventsislav Kolev Valev and colleagues suspected that these particles could be microplastics that—upon infusion—would enter the recipient’s bloodstream and potentially cause  negative health effects. So, they set out to analyze the types and amounts of particles in commercial IV fluid bags.

The team purchased two different brands of 8.4-ounce bags of IV saline solution. After the contents of each bag dripped into separate glass containers, the liquids were filtered to catch microscopic particles. Then the researchers counted a portion of the individual plastic fragments, using that amount to estimate the total number of microplastics in the entire pouch of IV liquid and to analyze the composition of the particles.

The researchers discovered that both brands of saline contained microplastic particles made from polypropylene—the same material as the bags—which suggests that the bags shed microplastics into the solutions. They estimated that each bag of infusion fluid could deliver about 7,500 microplastics directly into the bloodstream. This figure rises to about 25,000 particles to treat dehydration or 52,500 for abdominal surgery, which can require multiple IV bags. The researchers recommend keeping IV infusion bags away from ultraviolet light and heat to reduce microplastic shedding, and they say that micrometer-level filtration systems could be used to remove the particles during infusion.

While there are no clinical studies to date that have assessed the health risks of microplastics exposure, the researchers say their findings will help “provide a scientific basis for formulating appropriate policies and measures to mitigate the potential threats posed by microplastics to human health.”