Many millions of people around the world still die each year from infectious diseases, despite the fact that antibiotics were thought to have conquered such diseases forever. A sometimes dramatic increase in antibiotic resistance means that science and medicine must adapt to these highly flexible pathogens in an unceasing battle. The overall situation in Germany has also deteriorated significantly in this respect. While an almost unchanged level of resistance was observed in bacteria between 1975 and 1984, the frequency of resistance increased enormously in many bacteria thereafter.
What are antibiotics and how do they work?
Antibiotics are substances that kill single-cell microorganisms (which include bacteria) (bactericidal action) or inhibit their growth (bacteriostatic action). Since bacteria differ from human body cells in essential respects, for example cell wall, entirety of the hereditary apparatus (genome), cell organelles for protein synthesis (ribosomes), antibiotics can target these sites to prevent their spread in humans.
These are generally referred to as broad-spectrum antibiotics, which are effective against many different bacteria, and narrow-spectrum antibiotics (specialized for specific pathogens). In addition to common antibiotics, reserve antibiotics play an important role. They are used when antibiotic resistance occurs and/or very severe infections are present. However, they are often much more expensive, are often poorly tolerated, or/and resistance develops particularly quickly with them.
Antibiotics in animal feeds
Until 2006, the use of certain antibiotics was permitted as so-called performance enhancers in animal feed. Particularly fattening animals in large barns were continuously given a small dose of antibiotics in the form of a feed supplement. This served to promote animal growth and prevent disease.
This practice harbored a large reservoir of resistance genes because it systematically bred strains of bacteria with resistance to a particular antibiotic through widespread use of antibiotics. The resistance of certain bacterial strains can spread to others and thus poses a high risk.
Therefore, the addition of antibiotics to animal feed was banned throughout the EU in 2006.
Antibiotics in veterinary medicine
After the ban on antibiotics as performance enhancers in animal feed took effect in 2006, the use of antibiotics for veterinary purposes initially increased. However, official figures on this are not available until 2011.
Over the course of recent years, however, the amount of antibiotics used for veterinary medicine in Germany has decreased significantly. While 1,706 tons of antibiotics were still sold by wholesalers to veterinarians in 2011, the figure was only 805 tons in 2015. However, it should not be ignored that this still involves the use of antibiotics that are actually intended as reserve antibiotics for human medicine.
Antibiotics in genetic engineering
One area of antibiotic use that has received little public attention is the use of antibiotic resistance as so-called marker genes in genetic engineering. They are called marker genes because they are designed to mark genetically modified (transformed) cells. If these cells are placed on a culture medium soaked with the antibiotic in question, all the cells die except for those that have taken up the marker gene and thus also the desired gene, which is supposed to give the plant a new property. The antibiotic resistance gene thus plays only a purely technical role.
However, there are now fears that “horizontal gene transfer” may occur between genetically modified plants and the bacteria. This is theoretically possible wherever already decomposed plant material encounters large quantities of bacteria, for example in compost, silage or the gastrointestinal tract of humans and animals.
Although such gene transfer is very unlikely, it cannot be ruled out. Thus, in the EU release directive of fall 2002, the use of antibiotic resistance markers has been significantly restricted, but not generally banned.
