Antibiotics Stimulate the Growth of Bacteria

Antibiotics were found to stimulate bacterial reproduction, finds a new study from the University of Exeter. The research team exposed E.coli bacteria to eight rounds of antibiotic for over four days and found that the bug was capable of causing severe stomach pain, diarrhea and kidney failure among humans and had increased antibiotic resistance.

They were surprised to find mutated E.coli to have reproduced much faster and formed a population which was three times larger than before encountering the antibiotic drugs because of the mutations.

When the research team took the antibiotic drugs away, they found that the evolutionary changes were done and the new-found abilities remained.

Professor Robert Beardmore, University of Exeter, said, "Our research suggests there could be added benefits for E.coli bacteria when they evolve resistance to clinical levels of antibiotics."

"It's often said that Darwinian evolution is slow, but nothing could be further from the truth, particularly when bacteria are exposed to antibiotics.”

"Bacteria have a remarkable ability to rearrange their DNA and this can stop drugs working, sometimes in a matter of days.”

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"While rapid DNA change can be dangerous to a human cell, to a bacterium like E.coli it can have multiple benefits, provided they hit on the right changes."

Efficacy of Doxycycline Antibiotic in E.Coli
The research team tested the effect of doxycycline antibiotic in E.coli bacteria to understand the changes in the DNA brought by the antibiotics.

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The E.coli that was evolved were frozen at -80℃ and the research team also used genetic sequencing to find out DNA Changes that were responsible for unusual evolution.

Clinically, E.coli producing more antibiotic pumps were found to exploit the antibiotics out of the cell. And the loss of DNA is another well-known change that is known to describe the dormant virus.

Dr. Carlos Reding, said, "Our best guess is that losing viral DNA stops the E.coli destroying itself, so we see more bacterial cells growing once the increase in pump DNA allows them to resist the antibiotic in the first place."

Dr Mark Hewlett, University of Exeter, added, "It is said by some that drug resistance evolution doesn't take place at high dosages but our paper shows that it can and that bacteria can change in ways that would not be beneficial for the treatment of certain types of infection.”

"This shows it's important to use the right antibiotic on patients as soon as possible so we don't see adaptations like these in the clinic."

The current study uses liquid conditions, so that the E.coli bacteria can increase cell production.

References

1. Carlos Reding-Roman et al, The unconstrained evolution of fast and efficient antibiotic-resistant bacterial genomes, Nature Ecology & Evolution (2017). DOI: 10.1038/s41559-016-0050