Persistence phenotype of adherent-invasive Escherichia coli in response to ciprofloxacin, revealing high-persistence strains

Persister cells are a subpopulation of bacteria capable of surviving antibiotic treatments and are thought to contribute to disease chronicity and symptom relapse of chronic conditions. Crohn's disease (CD) is a multifactorial chronic inflammatory condition of the gastrointestinal tract, and ad herent invasive Escherichia coli (AIEC) have emerged as a key contributor to its pathogenesis. AIEC can survive, replicate, and produce persister cells within macrophages; however, beyond the LF82 reference strain, little is known about the persistence phenotype and its variability among AIEC strains. In this study, the survival of two AIEC reference strains was analyzed following ciprofloxacin treatment, a fluoroquinolone antibiotic commonly used in CD therapy. In addition, four AIEC clinical isolates and two non AIEC E. coli pathotypes were included for comparison. We investigated the roles of the resident antibiotic resistance plasmid, the stress response protein HtrA, and macrophage-induced persister formation. Our results revealed broad variability in persister cell formation among AIEC strains. Remarkably, the reference NRG857c strain exhibits a threateningly high persistence phe notype, with persistence levels 200 fold higher than LF82 and certain clinical isolates. Neither the antibiotic resistance plasmid nor HtrA were required for this phenotype. Moreover, unlike LF82, NRG857C did not exhibit increased persistence following macrophage internalization. Overall, our findings demonstrate the presence of distinct persistence phenotypes among AIEC strains and identify NRG857c as a high persistence variant. These observa tions underscore the need to consider bacterial persistence in the manage ment of CD, particularly given the potential presence of AIEC strains with elevated persistence capabilities.