In vitropersistence level reflectsin vivoantibiotic survival of naturalPseudomonas aeruginosaisolates in a murine lung infection model

Abstract

Nowadays, clinicians are more and more confronted with the limitations of antibiotics to completely cure bacterial infections in patients. It has long been assumed that only antibiotic resistance plays a pivotal role in this. Indeed, the worldwide emergence of antibiotic resistance is considered as one of the major health threats of the 21stcentury. However, the presence of persister cells also has a significant influence on treatment outcomes. These antibiotic-tolerant cells are present in every bacterial population and are the result of the phenotypic switching of normal, antibiotic-sensitive cells. Persister cells complicate current antibiotic therapies and contribute to the development of resistance. In the past, extensive research has been performed to investigate persistence in laboratory settings, however, antibiotic tolerance in conditions that mimic the clinical setting is still poorly understood. In this study, we have optimized a mouse model for lung infections of the opportunistic pathogenPseudomonas aeruginosa. In this model, mice are intratracheally infected withP. aeruginosaembedded in seaweed alginate beads and subsequently treated with tobramycin via nasal droplets. A strain panel of 18P. aeruginosaisolates originating from environmental, human and animal clinical sources was selected to assess survival in the animal model. These survival levels were positively correlated with the survival levels determined via time-kill assays which is a common method to study persistence in the laboratory. We showed that both survival levels are comparable and thus that the classical persister assays are indicative for antibiotic tolerance in a clinical setting. The optimized animal model also allows us to test potential antipersister molecules and study persistence.ImportanceThe importance of targeting persister cells in antibiotic therapies becomes more evident as these antibiotic-tolerant cells underlie relapsing infections and resistance development. Here, we studied persistence in a clinically relevant pathogen,Pseudomonas aeruginosa. It is one of the six ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, P. aeruginosa, Enterobacterspp.) that are considered as a major health threat.P. aeruginosais mostly known for causing chronic lung infections in cystic fibrosis patients. We mimicked these lung infections in a mouse model to study persistence in more clinical conditions. We showed that the survival levels of naturalP. aeruginosaisolates in this model are positively correlated with the survival levels measured in classical persistence assays. These results not only validate the use of our current techniques to study persistence, but also open opportunities to study new persistence mechanisms or evaluate new antipersister compoundsin vivo.

Environmental, mechanistic and evolutionary landscape of antibiotic persistence

“…Therefore, it is critical to contextualize basic research findings in in vivo mammalian models or clinical settings (Box 1). Recent research conducted with murine models appears to hold great potential for translating in vitro findings (Newson et al , 2022; preprint: Verstraete et al , 2022a). Additionally, several promising strategies have been proposed to combat antibiotic persistence, but their efficacy is yet to be validated.…”