Healthcare Hygiene magazine May 2021 May 2021 - Page 8

under the microscope

under the microscope

By Rodney E . Rohde , PhD , MS , SM ( ASCP ) CM SVCM , MBCM , FACSc

Microplastics and Antibiotic Resistance

Antibiotic and antimicrobial resistance ( AMR ) continues to be a slow-burning pandemic . It is not as recognized as the SARS-CoV-2 / COVID-19 pandemic . Even before the current ongoing global pandemic , AMR was a major global emergency , and we must not forget about this very dangerous public health threat . Most experts agree that AMR is a multi-faceted , complex problem . Resistance happens when germs ( any microbe ) defeat the drugs designed to kill them . Any antibiotic or antimicrobial use — in people , animals , or crops — can lead to resistance . Resistant germs are a One Health problem , as they can spread between people , animals and the environment .

The Centers for Disease Control and Prevention ( CDC ) tells us that antibiotic resistance is one of the biggest public health challenges of our time . Each year in the United States , at least 2.8 million people get an antibiotic-resistant infection , and more than 35,000 people die . Fighting this threat is a public health priority that requires a collaborative global approach .
As many of you know , I have discussed many forms of AMR in this column . Surfaces and biofilms intersect with AMR . Now , we have another hidden surface to consider regarding the problem of resistance . In a recent Elsevier Journal of Hazardous Materials Letters , researchers found certain strains of bacteria elevated antibiotic resistance by up to 30 times while living on microplastic biofilms that can form inside activated sludge units at municipal wastewater treatment plants .
These ultra-fine plastic particles , less than 5 m in length , are in everything from cosmetics , toothpaste and clothing microfibers , to our food , air and drinking water . News Medical reports that estimates show an average-sized wastewater treatment plant serving roughly 400,000 residents will discharge up to 2,000,000 microplastic particles into the environment daily . Researchers are still learning the environmental and human health impact of these ultra-fine plastic particles .
The authors of the study discuss that some research focuses on the negative impacts that millions of tons of microplastic waste a year is having on our freshwater and ocean environments . Only recently , have studies started looking into the role of microplastics in towns and cities ’ wastewater treatment processes which means we do not really know much there . The wastewater treatment plants may be hotspots where various chemicals , antibiotic-resistant bacteria and pathogens converge . The authors believe this is what their study documents regarding microplastics serving as their ( AMR ) carriers and posing hazards to aquatic biota and human health if they bypass the water treatment process .
The study was designed to collect batches of sludge samples from three domestic wastewater treatment plants in northern New Jersey , inoculating the samples in the laboratory with two widespread commercial microplastics – polyethylene and
polystyrene . Quantitative PCR and next-generation sequencing techniques identified the species of bacteria that tend to grow on the microplastics . These powerful molecular techniques allowed them to track and detect how the bacteria adapted and changed in real time .
The study revealed that three genes in particular – sul1 , sul2 and intI1 – known to aid resistance to common antibiotics , sulfonamides , were up to 30 times greater on the microplastic biofilms than in the experimental controls after just three days . Further , when they spiked the samples with the antibiotic , sulfamethoxazole , it amplified the antibiotic resistance genes an additional 4.5 times . The authors think the presence of antibiotics would be necessary to enhance AMR genes in these microplastic-associated bacteria , but it seems microplastics can naturally allow for uptake of these resistance genes on their own . However , it does appear that the presence of antibiotics can have significant amplification .
The study revealed eight different species of bacteria were highly enriched on the microplastics . Two of those species were emerging human pathogens typically linked with respiratory infection , Raoultella ornithinolytica and Stenotrophomonas maltophilia . The most common strain found on the microplastics was , Novosphingobium pokkalii , and is likely a key initiator in forming the sticky biofilm that attracts such pathogens because it leads to breakdown of the plastic and expands the biofilm . The study also highlighted the role of the gene , intI1 , a mobile genetic element chiefly responsible for enabling the exchange of antibiotic resistance genes among the microplastic-bound microbes .
Most people likely think that these tiny microplastic “ bead-like ” materials are unseen and not a problem . However , what this study has shown us is that microbes always find a way to develop a niche and take advantage of their environment and surfaces . When a bacterium like Novosphingobium accidentally attaches to a microplastic surface and secretes glue-like extracellular substances ( biofilms ), it can allow other bacteria to stick to surfaces and grow . More worrisome is that it will offer them the opportunity to exchange DNA . This is how the antibiotic resistance genes are being spread among the community . Ultimately , this study and others may bring new regulations on the use of microplastics in consumer products .
Rodney E . Rohde , PhD , MS , SM ( ASCP ) CM SVCM , MBCM , FACSc , serves as chair and professor of the Clinical Laboratory Science Program at Texas State ; associate director for the Translational Health Research Initiative ; as well as associate dean for research in the College of Health Professions . Follow him on Twitter @ RodneyRohde / @ TXST _ CLS , or on his website : http :// rodneyerohde . wp . txstate . edu /
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