New study shows microplastics turn into ‘hubs’ for pathogens, antibiotic-resistant bacteria

It is estimated that an average-sized wastewater treatment plant serving about 400,000 inhabitants will dissolve 2,000,000 microplastic particles per day into the environment. However, researchers are still learning the environmental and human health effects of these ultra-fine plastic particles, less than 5 millimeters in length, found in everything from our cosmetics, toothpaste and clothing microfibers to our food, air and drinking water. .

Now, researchers at the New Jersey Institute of Technology have shown that ubiquitous microplastics can form ‘hubs’ on the surface of a building, which builds up on the surface Which allows pathogenic microorganisms and antibiotic wastes to attach and come off.

Findings published in Journal of Hazardous Materials Letters, Researchers found a 30-fold increase in some strains of living bacteria on microplastic biofilms that can form inside active sludge units in a municipal wastewater treatment plant.

“Many recent studies have focused on the negative effects of millions of tons of microplastic waste a year on our freshwater and ocean environments, but so far the role of microplastics in the wastewater treatment of our towns and cities remains largely unknown.” Said Mangian Li, associate professor and co-author of the study. “These wastewater treatment plants can be hotspots where various chemicals, antibiotic-resistant bacteria and pathogens combine and our study shows that microplastics can pose negative risks to aquatic biota and human health if they bypass the water process.”

“Most wastewater treatment plants are not built to remove microplastics, so they are constantly discharged into the receiving environment,” Dung Negok Fam added, adding that NJIT Ph.D. Candidate and first author of the study. “Our goal was to investigate whether microplastics are enriching antibiotic-resistant bacteria from activated sludge in municipal wastewater treatment plants, and if so, learn more about the microbial communities involved.”

In their study, the team collected batches of sludge samples from three domestic wastewater treatment plants in northern New Jersey, inoculating samples into the lab with two extensive commercial microplastics – polyethylene (PE) and polystyrene (PS). The team used quantitative PCR and next-generation sequencing techniques to identify species of bacteria growing on microplastics, tracking bacterial genetic mutations.

The analysis found that the three genes in common antibiotics, especially Sal 1, Sal 2 and Inti1, known to help resistance to sulfonamides, were 30 times more than lab control tests using sand biofilms after just three. Day.

When the team sampled the antibiotic, sulfamethoxazole (SMX), they found that the antibiotic resistance genes were increased by 4.5 times.

“Previously, we thought that the presence of antibiotics would be necessary to enhance antibiotic-resistance genes in these microplastic-related bacteria, but it seems that microplastics can naturally consume these resistance genes.” Fame said. “However the presence of antibiotics has a significant multiplication effect.”

Eight different species of bacteria have been found to be very rich on microplastics. In these species, the team observed two emerging human pathogens commonly associated with respiratory infections, Roulette ornithanolitica and Stanotrophomonas maltophilia, which are frequently reluctant to microplastic biofilms.

The team says that the most common strain ever seen on microplastics, Novosphingobium pokkali, is probably a major initiator in the formation of the sticky biofilm that attracts such pathogens – as it can contribute to plastic degradation and expand the biofilm. Can. At the same time, the team’s study highlighted the role of the mobile genetic element gene, Inti1, primarily responsible for enabling the exchange of antibiotic-resistant genes between microplastic-bound microorganisms.

“We would think of microplastics as small beads, but they provide a large surface area for microbes to live,” Lynn explained. “When these microplastics enter a wastewater treatment plant and mix with sludge, bacteria such as novosphinobium can accidentally attach to the surface and secrete foreign cellular substances such as glue. Other bacteria attach to the surface and grow. They can also exchange DNA with each other. “This is how antibiotic resistance genes are spread in the community.”

“We have evidence that the bacteria thus resisted other antibiotics, such as aminoglycosides, beta-lactam and trimethoprim,” he added.

Now, Li says, the lab is doing more studies on the role of novosphinobium in biofilm formation on microplastics. By studying the resistance of microplastic biofilms during treatment of wastewater with disinfectants such as TV UV light and chlorine, it seeks to better understand the extent to which such pathogen carriers can bypass water treatment processes to microplastics.

“Some states are considering new regulations regarding the use of microplastics in consumer products. This study calls for further investigation into microplastic biofilms in our wastewater systems and the development of effective means to remove microplastics in aquatic environments,” Lee said.