Fighting bacterial diseases is a perpetual arms race between medical scientists developing new therapeutics and the pathogenic bacteria continuously changing their genetic makeup to survive the drugs.

When antibacterial treatment is initiated, the high concentration of antibiotics kills most bacteria or stops them from growing almost immediately. The patient often feels better after just a few days of treatment, but the rapid recovery can be treacherous. In a study that was recently published in PNAS, we show that a small fraction of the bacteria often continues to grow, sometimes up to 10 generations.

These bacteria are not resistant. They can continue to divide despite a relatively high concentration of antibiotics due to natural variations in the bacterial strain. But each cell division gives the bacterium a chance to mutate in a way that makes the strain resistant. However, this is a rare event; if you continue your treatment until the last pill, you stand a good chance of clearing the infection.

Many research studies look at the bacterial population as a whole, that is, the collective response of many bacteria. Since perseverent bacteria are very rare, these have so far escaped attention. We specialize in studies of individual bacteria and how they react to different stimuli, for example, antibiotics. With the help of microfluidic culture chips and AI-based analysis algorithms, we can follow the growth of tens of thousands of individual bacteria in one experiment.

Read the study open access in PNAS