Is Bacterial Persistence a Social Trait?

The ability of bacteria to evolve resistance to antibiotics has been much reported in recent years. It is less well-known that within populations of bacteria there are cells which are resistant due to a non-inherited phenotypic switch to a slow-growing state. Although such ‘persister’ cells are receiving increasing attention, the evolutionary forces involved have been relatively ignored. Persistence has a direct benefit to cells because it allows survival during catastrophes–a form of bet-hedging. However, persistence can also provide an indirect benefit to other individuals, because the reduced growth rate can reduce competition for limiting resources. This raises the possibility that persistence is a social trait, which can be influenced by kin selection. We develop a theoretical model to investigate the social consequences of persistence. We predict that selection for persistence is increased when: (a) cells are related (e.g. a single, clonal lineage); and (b) resources are scarce. Our model allows us to predict how the level of persistence should vary with time, across populations, in response to intervention strategies and the level of competition. More generally, our results clarify the links between persistence and other bet-hedging or social behaviours

The functional resistance of bacterial biofilms

There is intellectual coherence when a physician must tell patients that the bacteria causing their infection have tested resistant to the empiric antibiotic therapy, and that an alternative drug must be used. In this chapter, we will concern ourselves with the growing number of bacterial infections in which antibiograms of the causative organism show sensitivity to standard antibiotics in readily attainable concentrations, but the infection fails to be cleared. This discrepancy is troubling and frustrating for patients, physicians, and diagnostic laboratories alike, but it can now be resolved by concepts that have become widely accepted in microbial ecolog