Category: Antibiotic of the week

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Antibiotic of the week: Metronidazole

Antibiotics Pollution Index: 400 (11 September 2017)
What is the Antibiotics Pollution Index?

What it does
Metronidazole gets activated in cells that live in oxygen-low environments, known as anaerobic cells. It is effective against many anaerobic organisms, which include bacteria and parasites. It binds DNA, and causes breaks which cells do not survive.
Due to activation in an oxygen-low environment, this drug separates anaerobic cells from the patient’s own aerobic (oxygen-breathing) cells. Metronidazole use, however, increases the risk for cancer, which may be the result of activation in human cells, too. When received in high doses, this drug can also be neurotoxic.

Who gets it
An infamous target for metronidazole is Clostridium difficile, a typical landmark for bad hygiene and incorrect antibiotic use, leading to diarrhea, colon perforation, with a potential fatal outcome. It is also administered to prevent surgery-related infections and sexually transmitted diseases. Not only people are treated. This carcinogenic antibiotic is a frequently used drug in animal husbandry and aquaculture. It has been banned in the USA and Europe for food-producing animals, but big and small pets (such as horses, dogs, ornamental fish and reptiles) still receive it. Outside the EU and USA, you may find your metronidazole in your food, too: it is given to poultry, pigs, and fish. In all animals studied, this antibiotic remains detectable in many organs up to 2-3 weeks after the last dosage. This is 2 weeks short of the complete life of your average meat-chick.

Where may it be produced?
Poland, India, Italy, Portugal, China, Mexico, USA, France.

And, SquaredAnt, does it pollute?
We found evidence for pollution in WWT effluent, hospital effluent and river water. The concentration in WWT effluents is around 0.1 ng/ml. 500 million liters of waste water would give you approximately one dosage of metronidazole, of which you’d probably need 4 in a day. Spectacular enough, this low concentration could trigger resistance against metronidazole. Given the usage in farms, hospitals and pets throughout the world, there are probably quite a few places oxygen-low places -such as sewage systems and lagoons -where metronidazole pollution stimulates resistance on the long term.

Warning lights
The high cost of appropriate tests for infections and the seriousness of anaerobic infections has lead to an overuse of usage and an under-reporting of resistance against metronidazole.  But let’s give patients and doctors the benefit of the doubt. A more worrying signal is our finding that the on-line demand of this drug is very high. For those who ignore resistance, oncogenic and neurotoxic risks, metronidazole may seem like a wonder drug that can compensate bad hygiene and poor maintenance in stables, ponds, terrariums, etc.

Any common sense in this antibiotic?
Since 2 decades, metronidazole has been banned from food producing animals in the USA (1994) and the EU (1998). From 2017, authorities in China have introduced a standard to test for metronidazole in food. This indicates at the very least that metronidazole pollution is on the radar in China.

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Antibiotic of the week: Cefotaxime

Antibiotic pollution index: 236 (11 September 2017)
What is the Antibiotic Pollution Index?

What it does
The cell wall separates the bacterial cell from its surroundings, gives it strength and protection. With cefotaxime, cell walls break and bacteria die.

Who gets it
Cefotaxime is used to treat a wide range of infections, such as pneumonia, meningitis, abdominal infections and joint infections. It is a typical broad spectrum antibiotic: many bacteria dislike it. Veterinarians, however, do like it. Cefotaxime is used to treat pets and small farm animals worldwide, and cattle and pigs in a number of countries.

Where may it be produced?
India, China, Korea, USA, Italy, Germany.

And, SquaredAnt, does it pollute?
It may very well be. We found evidence for pollution in Spain and the United Kingdom, from hospital waste, waste water treatment effluents, and river water. All concentrations lie around 0.1 ng/ml. This means: if a course of cefotaxime would be be 2 gram per day, you would have to drink 20,000,000 liter if you’d like to recycle from river water directly. A daunting task, but hey, what doesn’t kill you makes you stronger!

Warning lights
If antibiotics concentrations are too low to kill bacteria, bacteria may start to allow this antibiotic in their daily lives at higher concentrations. What doesn’t kill them, makes them stronger… we call this “Antibiotic Resistance”, but the term could be “Antibiotic Ignorance” too. Resistance gives the impression of combat, that bacteria struggle to survive, that some day, resistance may be broken. But in many cases, bacteria don’t fight. For resistant bacteria, the antibiotic has become one of the many chemicals they simply deal with. From their perspective, the antibiotic is not even an antibiotic any more. They changed the lock, got a new key, end of story.
Antibiotic resistance (or should I say “ignorance”) against cefotaxime is on the rise everywhere. Portuguese rivers, American fruits an Indian dairy, they all contain bacteria that are perfectly fine to be exposed to cefotaxime.

Any common sense in this antibiotic?
No. Cefotaxime is a very powerful antibiotic to treat serious human diseases. But for now, treating pets, poultry, pigs and other animals with cefotaxime, which leads to a noticeable release into the environment as well as a rise in antibiotic resistance, is incompatible with a common sense strategy that reserves this drug for patients in need.

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Antibiotic of the week: Sulfadimethoxine

Antibiotics Pollution Index: 73 (11 September 2017)
What is the Antibiotics Pollution Index?

What it does
It prevents bacteria to form folic acid. Folic acid is crucial for cell division of bacteria; without folic acid, a bacterium cannot multiply and thereby spread the infection. It does not kill the bacteria directly.

Who gets it
Pets, cattle, poultry and fish. It is given to treat skin infections, urinary tract infections, respiratory infections and even parasitic (non-bacterial) infections. It is also used to treat “Bovine Respiratory Disease”, in cows. This disease  is caused by a combination stress, a mix of infections, and other unknown triggers. This disease is costing the USA alone USD 500 million/year.

Where may it be produced?
China, Japan, Poland, Switzerland.

And, SquaredAnt, does it pollute?
Yes, it does. We found publications about sulfadimethoxine in rivers in across the USA, and in waste-water and soil around farms in the USA and China. Around farms, the concentrations lie around 1 nanogram per gram. For a small farm, this is sufficient for 10 dosages for an animal that weighs 800 kg (see table below).

Farm size 100,000 square meter
Top soil mass 1000 kg/ cubic meter
Penetration of antibiotic (estimation) 0.1 meter
Concentration 0.000001 gram / kg
Product by multiplication 10 gram
(Equals to ~10 dosages for a cow)

Conservative estimation of Sulfadimethoxine pollution on a polluted farm

Warning lights
In 2015, the article “The Ocean as a Global Reservoir of Antibiotic Resistance Genes” described a number of lagoons and bays, where scientists found bacteria that were resistant against sulfadimethoxine. This is remarkable, as sulfadimethoxine is not produced in nature: it is a synthetic molecule. Apparently, some marine bacteria carry resistance against this non-natural antibiotic – in vast amounts, as the ocean harbors so many bacteria.
Coastal waters are increasingly put to use for humans. Creating a meeting point for resistant bacteria from the sea (via seafood, recreation, shipping, or desalination) and sulfadimethoxine residue (via meat, vegetables, pet excretion and surface waters) gives microbes a dream start to spread resistance among each other and should be avoided.

Any common sense in this antibiotic?
It is hopeful that as of 2017, sulfadimethoxine has changed status from OTC to prescription drug for veterinarian use in the USA. Before, gallon-sized bottles were available for anyone. When these are disposed of, and the residue has run off the land, then the pollution level may decrease.

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