A new scientific study finds antibiotics can have detrimental effects on the descendants of those exposed to them, including weaker immune systems. Antibiotics have once proclaimed the salvation of the world. However, now researchers fear that antibiotics could become a threat to public health and the natural environment.

Since its invention, we have used antibiotics in such large doses and so often that more and more of us become resistant, and thus otherwise common and harmless infections can become life-threatening for us.

In recent years, research has also shown that just being exposed to antibiotics can have a negative effect; both on the organism being exposed and on the offspring of the organism.

Antibiotics always found in our water

And we are many, both humans and animals, who are exposed to antibiotics. Antibiotics are often found in wastewater, groundwater, surface water, and even bottled water and are thus difficult not to come into contact with.

“The half-life of antibiotics is quite short – it is out of the water again after hours or days – but since large amounts are continuously released into our water, we consider antibiotics as pseudo persistent water pollution,” says Elvis Genbo Xu, who is an expert in ecotoxicology and assistant professor at the Department of Biology, University of Southern Denmark.

He is the co-corresponding author of a new study on the undesirable effects of antibiotics, published in the Environmental Science & Technology journal.

The background for the study is that in recent years, researchers have discovered that antibiotics can have a detrimental effect on the descendants of the individuals exposed to the drugs.

“In this study, we examined the offspring of zebrafish that were exposed to CTC, which is a common antibiotic. The CTC concentrations of the experiment corresponded to the concentrations that wild organisms may encounter in nature.

“We can see that the young generations, ie the offspring, are less effective at fighting bacteria and in general have a weaker immune system than the parent generation,” explains Elvis Genbo Xu.

More specifically, the study shows that the first generation of zebrafish, born to CTC-exposed parents, had weakened antibacterial defenses and that the number of their immune cells decreased. The latter also applied to the third generation. When an organism’s immune system is weakened, the organism becomes less able to fight viruses and bacteria and thus more prone to diseases.

Previous research has also shown that males among so-called false scorpions (Cordylochernes scorpioides) have poorer sperm quality when their fathers have been exposed to the antibiotic tetracycline: the number of viable sperm cells fell by 25 percent.

Increased antibiotics usage

• Between 2000 and 2018, global antibiotic consumption rates increased by 46% (from 9.8 to 14.3 Defined Daily Dose (DDD) per 1000 population per day).
• In low- and middle-income countries, there was a 76% increase observed between 2000 and 2018 (from 7.4 to 13.1 Defined Daily Dose (DDD) per 1000 per day).
• The largest increases in antibiotic consumption rates were seen in the North Africa and Middle East region (111% increase) and South Asia (116%).
• Every year, more than 700,000 people die as a result of antibiotic resistance; a number expected to rise to 10 million in 2050!

Antibiotic Chlortetracycline causes transgenerational immunosuppression via NF-κB

The extensive and increasing global use of antibiotics results in the ubiquitous presence of antibiotics in the environment, which has made them “pseudo persistent organic contaminants.”

Despite numerous studies showing wide adverse effects of antibiotics on organisms, the chronic environmental risk of their exposure is unknown, and the molecular and cellular mechanisms of antibiotic toxicity remain unclear.

Here, the researchers systematically quantified transgenerational immune disturbances after chronic parental exposure to environmental levels of a common antibiotic, chlortetracycline (CTC), using zebrafish as a model. CTC strongly reduced the antibacterial activities of fish offspring by transgenerational immunosuppression.

Both innate and adaptive immunities of the offspring were suppressed, showing significant perturbation of macrophages and neutrophils, expression of immune-related genes, and other immune functions.

Moreover, these CTC-induced immune effects were either prevented or alleviated by the supplementation with PDTC, an antagonist of nuclear factor-κB (NF-κB), uncovering a seminal role of NF-κB in CTC immunotoxicity.

The study results provide the evidence in fish that CTC at environmentally relevant concentrations can be transmitted over multiple generations and weaken the immune defense of offspring, raising concerns on the population hazards and ecological risk of antibiotics in the natural environment.

When using antibiotics, doctors now often advice the use of probiotics to minimize the negative impact on the human microbiome (gut flora). This also might help to mitigate the risks on the harmed immune system as decribed in the study.

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Sources: Neuroscience News, ACS Publications, University of Oxford, The Lancet, HelloDoc Health