Chromosomal beta-lactamase is packaged into membrane vesicles and secreted from Pseudomonas aeruginosa

Membrane vesicles were isolated from one β-lactam-sensitive and three β-lactam-resistant Pseudomonas aeruginosa clinical isolates from patients with cystic fibrosis. The presence of the chromosomally encoded β-lactamase in the membrane vesicles was shown by electron microscopy and enzymatic studies. This is the first report of extracellular secretion of β-lactamase in P. aeruginosa and it seems that the enzyme is packaged into membrane vesicles.