How antibiotic use in agriculture fuels resistance and threatens human health

Summary

The overuse of antibiotics in farming, especially for livestock, is a major cause of antibiotic-resistant bacteria, which can spread to humans through contaminated food, water, or direct contact with animals. This resistance makes infections harder to treat, leading to longer illnesses, higher medical costs, and even deaths. Antibiotic residues in meat, dairy, and eggs may also cause allergies, cancers, and other health problems. While some regulations exist, stricter measures are needed to reduce unnecessary antibiotic use in agriculture. Solutions include better farming practices, proper food handling, and finding alternatives like probiotics. A global "One Health" approach (that is, linking human, animal, and environmental health) is crucial to combat this growing crisis. 

Introduction

Using antibiotics a lot in farming, especially with animals we eat, is a big reason why bacteria are becoming resistant to these drugs. This resistance is a serious threat to our health and food supply. Farmers often give antibiotics to animals to keep them healthy and help them grow, but overusing these drugs has led to bacteria that can resist treatment. These resistant bacteria can spread to humans through direct contact, contaminated food, and the environment. This spread happens because bacteria can share their resistance traits with each other. The results are dangerous: treatments fail, more people die, and healthcare costs rise.

Even though there are rules to limit antibiotic use in farming, traces of these drugs still show up in food, causing allergies, disrupting gut health, and even leading to cancer. Studies show that up to 98% of meat samples in some areas contain antibiotic residues, and bacteria in livestock are becoming resistant to multiple drugs, making food safety even harder to manage. A comprehensive approach that considers human, animal, and environmental health is essential to tackle this issue. Alternatives like probiotics and plant-based feed additives show promise in reducing the need for antibiotics, but more research is needed to find scalable solutions. This review examines how using antibiotics in farm animals leads to antimicrobial resistance (AMR) in humans and explores sustainable alternatives to keep our food safe. The goal is to encourage responsible antibiotic use in farming, which will protect both human and animal health.

Widespread Use of Antibiotics in Animal Farming

Antibiotics are commonly used in food-producing animals worldwide, with agricultural practices accounting for most global antibiotic consumption [1]. These drugs are primarily administered to treat infections. Still, their excessive and improper use has led to serious public health concerns, including antibiotic resistance and residues in meat, dairy, and wastewater [2]. Furthermore, antibiotics used in aquaculture and antifungals in horticulture also contribute to the growing resistance problem, posing risks to both farmers and consumers [1]. Although some regulations have been introduced to limit antibiotic use in farming, stricter measures are still needed to minimize their impact [1].

Health Risks Linked to Antibiotic Residues and Resistance

The presence of antibiotic residues in food products presents multiple dangers, including environmental contamination, technological challenges in food processing, and health risks for both animals and humans [3]. Studies have shown that consuming contaminated food can accelerate antibiotic resistance, trigger allergic reactions, and even lead to severe health conditions such as cancer and reproductive disorders [3]. Moreover, when withdrawal periods and maximum residue limits are not followed, consumers may face additional risks, including disruptions in gut bacteria, antibiotic-resistant infections, and long-term health complications [4]. Antibiotic overuse in livestock farming affects human health and has economic consequences, as resistant infections become harder and more expensive to treat [5]. Researchers have emphasized that antibiotics should only be used to treat diagnosed illnesses in animals rather than for growth promotion, as indiscriminate use fuels the global antimicrobial resistance crisis [5].

Bacterial pathogens that are commonly transmitted to humans through food

Salmonella enterica (various serovars, including Typhimurium, Enteritidis, Typhi, Paratyphi, etc.)

• Found in poultry, eggs, meat, dairy, vegetables, nuts, and processed foods.
• Causes typhoid fever and gastroenteritis.

Escherichia coli (E. coli) (especially Shiga toxin-producing E. coli like O157:H7)

• Found in undercooked beef, raw milk, and contaminated vegetables.

Listeria monocytogenes

• Found in deli meats, soft cheeses, and unpasteurized dairy.

Campylobacter jejuni

• Common in raw poultry and unpasteurized milk.

Staphylococcus aureus (toxin-producing strains)

• Found in improperly handled cooked foods (e.g., meats, dairy).

Clostridium perfringens

• Associated with cooked meat dishes left at unsafe temperatures.

Clostridium botulinum (causes botulism)

• Found in improperly canned foods and honey.

Bacillus cereus

• Associated with rice, pasta, and other starchy foods.

Shigella spp.

• Spread via contaminated water and food handlers.

Vibrio spp. (e.g., Vibrio parahaemolyticus, Vibrio cholerae)

• Found in raw or undercooked seafood.

Yersinia enterocolitica

• Found in raw pork and contaminated water.

Enterococcus spp. (some antibiotic-resistant strains)

• Can contaminate dairy and meat products.

Source: https://doi.org/10.3389/fmicb.2019.02091

Transmission of Resistant Bacteria from Animals to Humans

Resistant bacteria developed in animals can easily spread to humans through multiple pathways, including direct contact with livestock, consumption of undercooked meat, and environmental contamination [5,6]. These bacteria can transfer resistance genes to human pathogens, making infections harder to treat and increasing mortality rates [7,8]. Fofana et al. [9] found that antibiotic-resistant E. coli in poultry poses a direct threat to consumers.

Source: https://doi.org/10.3390/foods12091756/

Surveillance programs have confirmed that reducing antibiotic use in animals leads to declining resistant bacteria in livestock and humans [7]. However, despite these findings, antibiotic residues remain prevalent in meat products. In Greece, 98% of meat samples contained antibiotic residues [10], while in Thailand, 68% of pork samples exceeded safe limits [11]. Children are particularly vulnerable due to their developing immune systems, increasing the urgency for stricter regulations [12].

Strategies to Reduce Antibiotic Use in Farming

To combat antibiotic resistance, experts recommend adopting a One Health approach, which integrates human, animal, and environmental health strategies [13,14]. This includes enforcing stricter regulations on antibiotic use, improving farm biosecurity, and promoting alternatives such as probiotics and phytogenic feed additives [15,16]. Continuous monitoring of antibiotic residues in meat and dairy is also essential to safeguard consumer health [17,18].

Conclusion

The overuse of antibiotics in agriculture poses serious risks to human health by accelerating antibiotic resistance and leaving harmful residues in food. While some risk assessments suggest that the immediate threat of resistant infections from meat is low [19], the long-term consequences demand urgent action. Farmers and policymakers can help protect public health while ensuring safe and productive farming practices by adopting responsible antibiotic use, enforcing stricter regulations, and exploring sustainable alternatives.

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