It is no secret that the use of antibiotics took the world by storm since Alexander Fleming discovered this magnificent substance in 1928. Not only did it save countless lives during the Second World War, but its ability to treat general infections caused by bacteria, such as pneumonia and sepsis, changed the world. In fact, it had such a great impact that antibiotics were administered for almost every ailment. This overuse of antibiotics left behind a footprint now referred to as antibiotic residue which is leading to frightening consequences.

When they asked Fleming about his discovery, his response was: “When you use antibiotics, use enough”. At the time, these words had little meaning, however recently people have started noticing the diminishing capabilities of antibiotics during treatment of bacterial infections. Antibiotic resistance (the ability of bacteria to resist the effects of antibiotics) is no longer a stranger to clinical, agricultural, and environmental settings. The over- and irresponsible use of antibiotics could have an unprecedented effect on our daily lives. It has already become apparent that individuals infected with bacteria are more difficult to treat, even if they have never used antibiotics before. The question lingers: How is it possible that people with little to no exposure to antibiotics suffer the effects of antibiotic resistance?

The answer might be in the food we consume…

Antibiotics in Food

It is inevitable that animals will become infected by bacterial pathogens causing common diseases such as Bovine Pleuropneumonia and Chlamydia Abortus. Antibiotics are used to treat such diseased animals. In an effort to prevent disease, antibiotics may be administered as a precaution to healthy individuals. Additionally, antibiotics are commonly mixed with food for livestock which acts as growth promoters. The consequence of this antibiotic overuse is the accumulation of antibiotics in agricultural food products distributed to the average consumer. Food products where antibiotic residue can be detected includes foods commonly consumed in any household, such as red meat, poultry, eggs, milk, and fish. The dangers of antibiotics ingested with these foods can understandably be considered as negligible. However, the indirect implications are much more dire during the silent development of antibiotic resistance in  bacteria that often infect humans.

Figure 1: Illustration of the footprint left by antibiotic residue in food.
[Image Credit: R.D Coertze –]

The Development of Antibiotic Resistance

Antibiotics can be described as a by-product of certain bacteria and fungi. Exposure to this substance can inhibit growth or destroy bacterial cells, which is why it is popular for the treatment of bacterial infections. One of the most widely administered group of antibiotics to clinical and agricultural settings is the beta-lactams. This includes antibiotics such as penicillin and cephalosporins. This group functions by inhibiting the synthesis of bacterial cell walls, thereby killing the bacteria.

There is one problem, antibiotics do not always kill bacterial pathogens. Some bacteria are naturally resistant to an antibiotic even without administering the proper dosages. This is why it is so important to complete a course of antibiotics to ensure the death of all potentially resistant bacteria. If used irresponsibly or in too small dosages, the resistant bacteria that survive will proliferate and when an illness inevitably returns, it will be very difficult to treat with the same antibiotic. The problem is that even with responsible and correct use of antibiotics, an increase in the number of antibiotic resistant bacteria in both clinical and agricultural settings is still observed.

What about the antibiotic residue in food mentioned earlier? As you ingest food that contain trace amounts of antibiotics, it is possible that these antibiotics create a selective pressure environment for natural gut bacteria. Without a person knowing, the antibiotics select for bacteria that can withstand the antimicrobial effects, thus resulting in a consortium of antibiotic resistant bacteria in the body. This is the exact same effect as knowingly using antibiotics. The real danger is not with natural occurring bacteria, in fact they ensure a heathy constitution. The problem arises with a bacterial infection and the transmission of antibiotic resistance from healthy bacteria to the pathogen. This means that previously susceptible pathogens that could be treated with antibiotics, suddenly become resistant, limiting the effectiveness of antibiotic treatment and effectively thrusting the patient back in time to a world before the discovery of Penicillin.

One of the best examples of the dangerous extent of how antibiotic resistance has developed is Staphylococcus aureus. This is only one of the many bacteria with a reputation for developing resistance to more than one group of antibiotics. Research have shown that S. aureus infections are more common in livestock than we originally thought. S. aureus was responsible for disease outbreaks dating as far back as the 1880s. This organism produces a toxin that directly influences the host, therefore, even if the bacteria are destroyed, the toxins produced can still negatively impact the host. A problem arises when one animal becomes infected and the whole herd receives medication as a precautionary measure. This frequent exposure to antibiotics causes the development of antibiotic resistant bacteria in animals used for consumption. This opens up a whole new can of worms where either a consumer can directly be exposed to antibiotic resistant bacteria or residual antibiotics in food can induce the development of antibiotic resistance. In events where food poisoning caused by bacteria such as S. aureus arises, the illness would be more difficult to treat due to resistance to multiple groups of antibiotics.

Additional Dangers

It is important to acknowledge the risks involved with using antibiotics. Not only when treating yourself or loved ones, but in agriculture and our fragile environment. Farmers use antibiotics to treat infections and these substances ultimately have an impact on the consumer. Besides the dangers of infection by antibiotic resistant bacteria, antibiotic residue in food may cause accumulation in human tissue that poses additional risks to human health. Frequent use of antibiotics has several harmful side effects that include allergies, toxicity, teratogenicity, and carcinogenicity.

An allergy can be developed over time and frequent exposure to a substance. The body then recognises the substance as harmful and triggers an immune response. In the case where a person develops an allergy towards an antibiotic, the residue in food will trigger an immune response that could be mistaken for the allergy of the food itself, not the antibiotic residue present in the food.

Teratogenicity refers to the abnormal development of human tissue during pregnancy. The antibiotic residue in food and foodstuffs might have an impact on the development of the unborn baby. It is advised that women consider organic food during pregnancy to eliminate the chances of development restrictors. Food and foodstuffs that are tested for antibiotic residue are naturally safer for pregnant women to consume.

Toxicity in food that has antibiotic residue can lead to complications in human health. Antibiotics used to treat animals are not always compatible with human physiology and may have an impact in how our cells metabolize. The disruption of cell metabolism can lead to abnormal energy production and inadequate removal of metabolic by-products. Antibiotic residue also disrupts the natural microflora in the human gut that is responsible for digestion.

Tests and Effective Monitoring

Following the potential dangers highlighted in the prior sections, the frequent screenings of food for chemical substances are crucial. There are acceptable levels in antibiotic residue testing to ensure the safety of the consumer. Even though diagnostic laboratories can detect and report these levels, it is up to the distributor to enforce transgressions and take responsibility in the event of a violation. An undeniable fact is that animals become infected in agriculture. Considering the dangers, dosages of antibiotic administration should always be monitored to ensure the antibiotic residue levels present in food is not harmful to consumers. The tests used to detect and quantify the amounts of antibiotic residue in food differs and the specific use relies on the application.


Everyone in the realm of Food Safety have a responsibility to consumers. It starts with responsible administration of antibiotics in the agricultural setting. There are acceptable limits for antibiotic residue in food and foodstuffs. These limits can guide the producer to ensure healthy limits of these substances without harming the consumers. It is recommended to do the necessary tests to clarify the status of the food a distributor produces. Alexander Fleming was not wrong when he warned us about the effects of antibiotics. In 1945, Alexander Fleming’s famous Noble prize-winning speech read:

“The time may come when penicillin can be bought by anyone in the shops. Then there is the danger that the ignorant man may easily underdose himself and by exposing his microbes to non-lethal quantities of the drug, make them resistant.”


All information presented in this publication is the opinion of SMT LABS based on literature reviews and interpretation. Under no circumstances should it be used to replace scientific findings.

Information Links

FutureLearn. (2018). A warning from Fleming., 13.08.2020.,the%20drug%20make%20them%20resistant

Dweba, C. C., Zishiri, O. T., & El Zowalaty, M. E., (2018). Methicillin-resistant Staphylococcus aureus: livestock-associated, antimicrobial, and heavy metal resistance. Infection and drug resistance, 11, 2497–2509.

Singh, S. B., Shukla, S., Tandia, N., Kumar, N., & Paliwal, R. (2014). ANTIBIOTIC RESIDUES: A GLOBAL CHALLENGE. Pharma Science Monitor 5(3), 184-197.