Stenotrophomonas maltophilia phenotypic and genotypic features through 4-year cystic fibrosis lung colonization

Abstract

<b>Introduction.</b> <i>Stenotrophomonas maltophilia</i> has emerged as one of the most common multi-drug-resistant pathogens isolated from people with cystic fibrosis (CF). However, its adaptation over time to CF lungs has not been fully established.<b>Hypothesis.</b> Sequential isolates of <i>S. maltophilia</i> from a Brazilian adult patient are clonally related and show a pattern of adaptation by loss of virulence factors.<b>Aim.</b> To investigate antimicrobial susceptibility, clonal relatedness, mutation frequency, quorum sensing (QS) and selected virulence factors in sequential <i>S. maltophilia</i> isolates from a Brazilian adult patient attending a CF referral centre in Buenos Aires, Argentina, between May 2014 and May 2018.<b>Methodology.</b> The antibiotic resistance of 11 S. <i>maltophilia</i> isolates recovered from expectorations of an adult female with CF was determined. Clonal relatedness, mutation frequency, QS variants (RpfC-RpfF), QS autoinducer (DSF) and virulence factors were investigated in eight viable isolates.<b>Results.</b> Seven <i>S. maltophilia</i> isolates were resistant to trimethoprim-sulfamethoxazole and five to levofloxacin. All isolates were susceptible to minocycline. Strong, weak and normomutators were detected, with a tendency to decreased mutation rate over time. <i>XbaI</i> PFGE revealed that seven isolates belong to two related clones. All isolates were RpfC-RpfF1 variants and DSF producers. Only two isolates produced weak biofilms, but none displayed swimming or twitching motility. Four isolates showed proteolytic activity and amplified <i>stmPr1</i> and <i>stmPr2</i> genes. Only the first three isolates were siderophore producers. Four isolates showed high resistance to oxidative stress, while the last four showed moderate resistance.<b>Conclusion.</b> The present study shows the long-time persistence of two related <i>S. maltophilia</i> clones in an adult female with CF. During the adaptation of the prevalent clones to the CF lungs over time, we identified a gradual loss of virulence factors that could be associated with the high amounts of DSF produced by the evolved isolates. Further, a decreased mutation rate was observed in the late isolates. The role of all these adaptations over time remains to be elucidated from a clinical perspective, probably focusing on the damage they can cause to CF lungs.