DIVERSITY AND EVOLUTION OF B-LACTAMASE ampC IN LONG-TERM Pseudomonas aeruginosa CHRONIC INFECTIONS

HEDEMANN G; MOLIN S; A. ALBARRACÍN; SOMMER LM; SMANIA, A; C. A. COLQUE; HICKMAN RA; JOHANSEN HK

Paraná

Congreso; LIV Reunión Anual de la Sociedad Argentina de Bioquímica y Biología Molecular; 2018

SAIB

Chronic Pseudomonas aeruginosa (PA) infections in the airways of patients with cystic fibrosis (CF) offer extraordinary opportunities to study bacterial evolution in natural environments. Continuous antibiotic treatment is a major factor in PA evolution, producing antibiotic-resistant bacterial lineages that expand under high selective pressure. We previously studied the evolutionary trajectories of two PA mutator lineages for 20 years of CF infection. Comparative genomic characterization showed that PA populations underwent extensive within-patient genomic diversification. However, PA isolates from one patient (CFD), who was intensively treated with β-lactam antibiotics, showed mutations that convergently target the β-lactamase encoding ampC gene, which may optimize pathogenic fitness. Here, we used a combination of phenotypic and molecular analysis, to inquire into the genetic diversity of ampC within long-term PA evolved populations. Sequential collections of isolates obtained from single sputum samples from the CFD patient were used, extending our study to 26 years of evolution. We obtained a time resolved map that shows that evolution is still occurring and driven by antibiotic treatment and that the ampC sequence is highly diverse across populations. Furthermore, some ampC allelic variants, which dominate the populations, were associated to high resistance towards cephalosporins and monobactams. Remarkably, by ultra-deep sequencing of ampC from sputum samples, we show that some positions in the ampC sequence are frequently hit by mutations across different CF patients suggesting a key role of these mutations in β-lactam resistance.