Production of extended-spectrum β-lactamases and the potential indirect pathogenic role of Prevotella isolates from the cystic fibrosis respiratory microbiota

Abstract Extended-spectrum β -lactamase (ESBL) production and the prevalence of the β -lactamase-encoding gene bla TEM were determined in Prevotella isolates ( n =50) cultured from the respiratory tract of adults and young people with cystic fibrosis (CF). Time-kill studies were used to investigate the concept of passive antibiotic resistance and to ascertain whether a β -lactamase-positive Prevotella isolate can protect a recognised CF pathogen from the action of ceftazidime in vitro. The results indicated that approximately three-quarters (38/50; 76%) of Prevotella isolates produced ESBLs. Isolates positive for ESBL production had higher minimum inhibitory concentrations (MICs) of β -lactam antibiotics compared with isolates negative for production of ESBLs ( P bla TEM gene was detected more frequently in CF Prevotella isolates from paediatric patients compared with isolates from adults ( P =0.002), with sequence analysis demonstrating that 21/22 (95%) partial bla TEM genes detected were identical to bla TEM-116 . Furthermore, a β -lactamase-positive Prevotella isolate protected Pseudomonas aeruginosa from the antimicrobial effects of ceftazidime ( P =0.03). Prevotella isolated from the CF respiratory microbiota produce ESBLs and may influence the pathogenesis of chronic lung infection via indirect methods, including shielding recognised pathogens from the action of ceftazidime.