The researchers developed a highly toxic and resistant strain of an antibiotic resistant bacteria called Pseudomonas aeruginosa and used it to investigate how it could spread through hospitals and into the wider environment.
“Normally the cost of making the extra proteins needed by bacteria to fight off antibiotics slows down the cells, making them weaker and less able to compete against their ordinary cousins”, say Dr Ger Fleming and his team leader Paul Mc Cay from the National University of Ireland, Galway. “When there aren’t any antibiotic residues about, the ordinary, susceptible strains become dominant, crowding out the superbugs”.
The university team discovered that when low levels of antibiotics were introduced – as little as 15% of the level normally needed to kill the ordinary bacteria – the resistant strain became dominant after just a few divisions.
“In places like hospital corridors or wards, there is a constant low level exposure to antibiotics which encourages the resistant strains to succeed, especially if there are already a few resistant bacteria about”, says Dr Fleming and Mc Cay. “Our results suggest that hospitals need to re-evaluate the minimum levels of treatments they think will stop infections, and include data on the way bacteria are selected and survive as well”.
Administering too low a level of antibiotics can cause a much more dangerous and long lasting infection by encouraging a resistant strain of bacteria to emerge. Disinfectant resistant bacteria are also emerging with increased use, and the scientists think this may be contributing to the problem through cross resistance.
MEDICA.de; Source: Society for General Microbiology