Re-sensitization of imipenem-resistant Pseudomonas aeruginosa and restoration of cephalosporins susceptibility in Enterobacteriaceae by recombinant Esterase B

Sphingobium sp. SM42 Esterase B (EstB) is an enzyme with a dual function in degrading dibutyl phthalate and catalyzing the cleavage of the C-S bond in C3-sidechains of the dihydrothiazine ring of cephalosporins, generating more active beta-lactam derivatives. Global prokaryotic genome analysis revealed the existence of a gene identical to estB in Pseudomonas aeruginosa strain PS1 suggesting a horizontal gene transfer event involving estB. To investigate the effect of ectopic expression of EstB in the periplasm of P. aeruginosa and several Enterobacteriaceae on antibiotic susceptibility levels, plasmid, pEstB, carrying a recombinant EstB fused with the signal peptide from Escherichia coli outer membrane protein A (OmpA) for periplasmic localization was constructed. The expression of EstB in the periplasm of P. aeruginosa and the Enterobacteriaceae: E. coli, Klebsiella pneumoniae, and Salmonella enterica serovar Typhi, increased susceptibility to carbapenems and cephalosporins. EstB reversed the imipenem resistance of P. aeruginosa Delta mexS and restored the changes in susceptibility to cephalosporins conferred by the downregulation of the outer membrane proteins, OmpK35 and OmpK36, in K. pneumoniae Delta ramR-ompK36 to wild-type level. The introduction of EstB to the periplasmic space of Gram-negative bacteria can increase carbapenem and cephalosporin susceptibility.