Superinfection with a transmissible strain of Pseudomonas aeruginosa in adults with cystic fibrosis chronically colonised by P aeruginosa

Infection with transmissible strains of Pseudomonas aeruginosa can occur In uncolonised patients, but cross infection (superinfection) of patients alr eady colonised with P aeruginosa has not been reported. With genotypic iden tification, we found superinfection by a multiresistant transmissible strai n of P aeruginosa in four patients with cystic fibrosis (CF) who were alrea dy colonised by unique strains of P aeruginosa. No evidence of environmenta l contamination was found, but all patients became superinfected after cont act with colonised Individuals during inpatient stays. Inpatients with CF w ho are colonised with P aeruginosa should be separated by strain type. Such strain typing can only be reliably done by genomic methods, but this has r esource Implications.