New York: Ultra-fine plastic particles can become ‘hubs’ for antibiotic-resistant bacteria and pathogens to grow once they wash down household drains and enter wastewater treatment plants, a new study says.
According to the scientists, including those from the New Jersey Institute of Technology (NJIT) in the US, these plastic particles less than five millimeters in length, called microplastics, allow the formation of a slimy layer, or biofilm, on their surface which allows bacteria and antibiotic waste to attach and mingle.
The research, published in the Journal of Hazardous Materials Letters, noted that certain strains of bacteria have elevated antibiotic resistance by up to 30 times when living on microplastic biofilms that form inside sludge units at municipal wastewater treatment plants. “A number of recent studies have focused on the negative impacts that millions of tons of microplastic waste a year is having on our freshwater and ocean environments, but until now the role of microplastics in our towns’ and cities’ wastewater treatment processes has largely been unknown,” said study co-author Mengyan Li from NJIT.
“These wastewater treatment plants can be hotspots where various chemicals, antibiotic-resistant bacteria and pathogens converge and what our study shows is that microplastics can serve as their carriers, posing imminent risks to aquatic biota and human health if they bypass the water treatment process,” Li said.
In the study, the scientists assessed batches of sludge samples from three domestic wastewater treatment plants in New Jersey, US, inoculating the samples in the lab with two widespread commercial microplastics — polyethylene and polystyrene.
They then identified the species of bacteria that tend to grow on the microplastics, tracking genetic changes of the bacteria along the way.
The researchers found that three genes in particular — sul1, sul2 and intI1– known to aid resistance to common antibiotics, sulfonamides, were found to be up to 30 times greater on the microplastic biofilms than in the lab’s control tests using sand biofilms after just three days.
When the scientists added the antibiotic, sulfamethoxazole, to these samples they found it further amplified the antibiotic resistance genes by up to 4.5-fold.
“Previously, we thought the presence of antibiotics would be necessary to enhance antibiotic-resistance genes in these microplastic-associated bacteria, but it seems microplastics can naturally allow for uptake of these resistance genes on their own,” said Dung Ngoc Pham, another co-author of the study from NJIT.
“The presence of antibiotics does have a significant multiplier effect however,” Pham said. Of the eight different bacterial species that the scientists found growing on the microplastics, they found two emerging human pathogens typically linked with respiratory infection.
“We might think of microplastics as tiny beads, but they provide an enormous surface area for microbes to reside,” Li said. According to the researchers, when microplastics enter the wastewater treatment plant and mix in with sludge, bacteria can accidentally attach to the surface and secrete glue-like substances.
“As other bacteria attach to the surface and grow, they can even swap DNA with each other. This is how the antibiotic resistance genes are being spread among the community,” Li explained.
The scientists said further studies are needed to better understand the extent to which such pathogen-carrying microplastics may be bypassing water treatment processes.
—PTI

Coronavirus variants from Brazil, South Africa are less susceptible to antibodies, says study
Berlin: Variant forms of the novel coronavirus which were first reported in South Africa and Brazil are less efficiently inhibited by antibodies from recovered patients and vaccinated individuals, a new study confirms. According to the research, published in the journal Cell, recovery from COVID-19 as well as vaccination may offer only incomplete protection against these mutant virus forms.
“This is worrisome because the rapid spread of variants that might not be efficiently inhibited by antibodies could undermine our current vaccination strategy,” said Stefan Pohlmann, a co-author of the study from the German Primate Center in Gottingen.
These virus variants have mutations in the spike protein — the structure on the surface of the virus that is responsible for attachment to host cells — the researchers said. In order for the virus to enter a cell, they said it must first attach to the host cell surface using its spike protein, which is located on the viral envelope.
The spike protein is also the target for antibody therapies and vaccines aimed at preventing the virus from replicating in the body, they researchers added.
Based on the research, the scientists said an antibody used for COVID-19 therapy did not inhibit the South African and Brazilian coronavirus variants — B.1.351 and P.1.
“Moreover, these variants were less well inhibited by antibodies from convalescent or vaccinated individuals, they partially bypassed the neutralising effect of the antibodies,” said Jan Munch, another co-author of the study.
The study noted that vaccination or recovery from COVID-19 may offer reduced protection from SARS-CoV-2 variants B.1.351 and P.1.
“Our findings show that it is important to limit the spread of the virus as much as possible until widespread vaccination is feasible. Otherwise, we risk the emergence of new variants that cannot be effectively controlled by the currently available vaccines,” said Markus Hoffmann, first author of the study.
—PTI

Press Trust of India