Posted by: Glow-worm PJ3 NOV 2011
Water and soil polluted by animal waste, for example, on farmland, can act as a reservoir of antibiotic-resistant bacterial genes, according to a paper in the October issue of Antimicrobial Agents and Chemotherapy, and these genes can be spread across species by bacteriophage viruses.
It is believed that these resistance genes are produced not as a result of human use of antibiotics, or even from use in animal feed, but are the result of millions of years of evolution, with antibiotics and resistance genes evolving side by side to enable different organisms to compete with each other.
Another method of resistance gene transfer between bacteria is via conjugative plasmids, which are segments of bacterial DNA. They are only able to divide and multiply inside the bacterial cell, using the cell’s own machinery, but once formed they can move freely between cells of widely different types of bacteria, including pathogens, thus transferring antibiotic resistance to new hosts.
Other studies have shown that the effects of a short course of antibiotics upon the natural flora of the gut can still be seen up to two years after treatment. It had previously been thought that the flora returned to normal within weeks of treatment, but these findings could have potentially life-threatening implications. Resistance genes lingering in the intestine within the normal gut bacteria could be passed to pathogens, which could then pass through the gut wall and cause infection that is resistant to treatment.
The World Health Organization has stated that bacterial resistance to antibiotics represents one of the biggest threats to public health. As the development of new antibiotics is relatively slow, the emphasis should be on using existing effective drugs with care and on the development of rational antibiotic administration guidelines worldwide.