Effects of sodium salicylate(Sal) and acetylsalicylate(AcSal), which are known to increase the susceptibility of Klebsiella pneumoniae to aminoglycosides, on the susceptibility of Klebsiella pneumoniae to cephalosporins such as cephalexin,
cefamandole,
cefoperazone and moxalactam were investigated.
@EN 1. On double-diffusion test, antimicrobial activity of cepholosporins was significantly inhibited by both Sal(3M, 30μl) disks. The inhibitory zone diameters produced by cephalothin and cefamandole disks on the plates containing Sal or AcSal
decreased as the concentration of the salicylates increased In a dose-dependent manner.
2. Minimal inhibitory concentrations(MICs) and minimal bactericidal concentrations(MBCs) of the test antibiotics in the media containing dither Sal(5mM) or AcSal(2.5mM) were measured. The MICs and MBCs of amikacin and gentamicin decreased twofold
to
fourfold. On the other hand. Those of cephalexin, cefamandole. cefoperazone and moxalactam increased twofold eightfold.
3. The outer membrane proteins were harvested form the organism cultured in the medium containing 5mM of Sal and analysed by electrophoresis. The intensity of the protein band of about 35.5kDa., which is supposed to be OmpF which is known to be
involved
in the transport of cephalosporins, decreased significantly.
These results suggested that salicylates increase the resistance of Klebsiella pneumoniae to cephalosporins by decreasing the transport of the drugs as a result of the inhibition of the production of OmpF.
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