Antibiotic contamination of the environment, fueled by industrial-scale use in livestock production in some countries, is a global problem that requires addressing, according to the authors of a just-published review.
The global challenge is to reduce and improve antibiotic use, Lizbeth Robles-Jimenez and her fellow researchers wrote in the journal Animals.
The review team examined previously published research about antibiotic drug residues and evaluated their use in livestock production, as well as their excretion in animal products, water, soil, and water.
Some antibiotics are widely used worldwide for their health protection, treatment of disease, and growth stimulators in animal production.
The authors pointed out that antibiotics are often poorly absorbed by animals and that 70 to 90% of them may be excreted in the environment without being metabolized. “These residues remain unchanged in the environment.”
The authors found 165 published studies in all, reporting the concentration of antibiotic residues found in the environment, livestock (cow, sheep, pig, horse, chicken, rabbit, goat), aquatic and terrestrial animal tissues, animal products (milk and eggs), wastewater, and soil. These papers were obtained from Asia and Africa, North America, South Americas, Europe, and Oceania.
China (55%), Brazil (7.9%), USA (7.0%) and Thailand (2.2%), India (2.2%), Iran (1.9%), Spain (1.9%), Russia (1.9%), Mexico (1.7%) and Argentina (1.5%).
The review team noted that there was a wide range of antimicrobial families in the residue levels of antibiotics depending on continent.
Cephalosporins were the antimicrobial most concentrated in Asia, followed by fluroquinolone.
The antibiotic family with the highest residual concentration in Africa was the tetracyclines. In South America, fluroquinolones followed by macrolides was the family with the highest levels of residues.
The European -lactam had the highest concentration of residues, followed by nitroimidazole.
“It is important to note,” they said, “that there is a particular distribution of antibiotic use by geographical area depending on their policies, economic/market conditions, and dietary habits.”
The authors noted that the regulation of antibiotics in animal feed, for growth promotion or therapeutic use, is a priority for the Asian region, and policies for their prohibition have been developed. Unfortunately, not all countries have the ability to guarantee their use.
The Chinese government has established a series of policies to restrict the use antibiotics in livestock. These include the requirement for prescriptions. They are still available for purchase without prescription, and most farms do not monitor their use.
Russia allows farmers to use antibiotics without restrictions. However, some feed antibiotics can be controlled by the state.
The researchers found that India’s higher standard of living had led to an increased demand for animal protein. This in turn has resulted a rise in the number of fish, poultry, and pig farms, which has had a significant effect on antibiotic use.
“When talking about meat producers, one must mention the worlds leading meat producers, North and South America, which are also among the main consumers of veterinary antibiotics.
“For example, the United States uses 24.6 million pounds of antimicrobials for non-therapeutic purposes in chickens, cattle, and pigs, the most commonly used being tetracyclines, penicillins, fluroquinolones, and sulfonamides, and Brazil, being the fourth largest pork producer in the world, uses sulfonamides.
“However, although government agencies are trying to regularize the use of antibiotics, producers are not willing to stop using them, as they consider that it would be impossible to sustain current market demands without the use of antimicrobials.
“In our study, we can confirm this since most of the articles found on antibiotic residues were from the USA and Mexico. Although Brazil is one of the largest meat producers, only one article was found, which may be due to the lack of published reports and complex political barriers.”
The researchers said that although most countries have joined in the program of non-misuse of antibiotics in food animals, publication of reports, complex political, economic, and social barriers still limit the quality of data on this issue.
The data on antibiotic use is easier to find from countries that export significant amounts of their animal production than those whose majority of production is destined for the domestic marketplace.
The authors stated that antibiotic contamination can cause environmental pressure on microorganisms in soil or water, which leads to a reduction in diversity and composition in the microbial community.
“Appreciating that antibiotic exposure tends to favor an increase in Gram-negative bacteria compared to Gram-positive bacteria, this will result in the disruption or loss of bacteria that play key ecological roles such as in the decomposition of matter,” they said.
They acknowledged that antibiotics are now only used as therapeutics and have been restricted from being used as growth promoters in animal agriculture by international policies.
“Intensive livestock production must change, as it would be impossible to sustain current market demands without the use of antimicrobials or friendlier alternatives, with a future decrease in antimicrobial resistance, so we are challenged to reduce their use.
“At present, despite the trends of increased regulations on the use of antibiotics worldwide, antibiotics are still utilized in food animal production, and are present in water and soil.”
The misuse of antibiotics continues in many countries, they said. “We need to become aware that antibiotic contamination is a global problem, and we are challenged to reduce and improve their use.”
The review team, from a range of institutions, including the Autonomous University of Mexico State, comprised Robles-Jimenez, Edgar Aranda-Aguirre, Octavio Castelan-Ortega, Beatriz Shettino-Bermudez, Rutilio Ortiz-Salinas, Marta Miranda, Xunde Li, Juan Angeles-Hernandez, Einar Vargas-Bello-Prez, and Manuel Gonzalez-Ronquillo.
Robles-Jimenez, L.E.; Aranda-Aguirre, E.; Castelan-Ortega, O.A.; Shettino-Bermudez, B.S.; Shettino-Bermudez (B.S. Animals 2022, 12, 60. https://doi.org/10.3390/ani12010060
The study, published under a Creative Commons License, can be read here.