Abstract
Bacteria commonly form dense biofilms encased in extracellular polymeric substances (EPS). Biofilms are often extremely tolerant to antimicrobials but their reliance on shared EPS may also be a weakness as social evolution theory predicts that inhibiting shared traits can select against resistance. Here we show that EPS of Salmonella biofilms is a cooperative trait whose benefit is shared among cells, and that EPS inhibition reduces both cell attachment and antimicrobial tolerance. We then compare an EPS inhibitor to conventional antimicrobials in an evolutionary experiment. While resistance against conventional antimicrobials rapidly evolves, we see no evolution of resistance to EPS inhibition. We further show that a resistant strain is outcompeted by a susceptible strain under EPS inhibitor treatment, explaining why resistance does not evolve. Our work suggests that targeting cooperative traits is a viable solution to the problem of antimicrobial resistance.
Highlights
Bacteria commonly form dense biofilms encased in extracellular polymeric substances (EPS)
We demonstrate that EPS is a public good in Salmonella biofilms, that resistance does not evolve under 40 days of EPS inhibitor treatment and, most importantly, we find a resistant strain and demonstrate that this is outcompeted by a susceptible strain when we treat biofilms with the inhibitor
Our work suggests that public good inhibition is effective against biofilms, and, more generally, as a way to combat the rise of antimicrobial resistance
Summary
Bacteria commonly form dense biofilms encased in extracellular polymeric substances (EPS). The absence of biofilm cells on the surface (Fig. 3f) and the low biomass (Fig. 3e) and csgD expression levels (Fig. 3h) in the presence of 75 μM inhibitor are a result of both EPS inhibition and planktonic growth inhibition.
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