Open AccessKlebsiella oxytoca : Resistance to aztreonam by overproduction of the chromosomally encoded β‐lactamase
Author(s) -
Fournier B.,
Arlet G.,
Lagrange P.H.,
Philippon A.
Publication year - 1994
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1994.tb06671.x
Subject(s) - aztreonam , klebsiella oxytoca , microbiology and biotechnology , plasmid , cefotaxime , biology , mutant , ceftazidime , enterobacteriaceae , genetics , gene , bacteria , escherichia coli , antibiotic resistance , antibiotics , imipenem , pseudomonas aeruginosa
Aztreonam‐resistant Klebsiella oxytoca strain SL7811 was selected on agar containing 1 μg of aztreonam per ml from a susceptible strain SL781. The MICs for the resistant mutant towards penicillins, aztreonam and ceftriaxone were much higher, to cefotaxime slightly higher and to ceftazidime unchanged. Synthesis of β‐lactamase was 223‐fold greater in the mutant compared with the susceptible strain. SL781 and its resistant mutant SL7811 produced β‐lactamase with the same isoelectric point and substrate profile. The β‐lactamase genes from SL781 and SL7811 were cloned in plasmid pBGS18 giving pBOF‐1 and pBOF‐4 respectively. The sequences of the two putative promoters indicated two modifications in the resistant plasmid pBOF‐4: a transversion (G → T) in the first base of the − 10 consensus sequence and a deletion of one C residue four base pairs upstream of the − 10 hexamer.