RESUMEN
The effect of ciprofloxacin and two mar RAB inducers on the susceptibility to beta-lactam antibiotics in two AmpC beta-lactamase semi-constitutive producer Citrobacter freundii clinical isolates (the DM 1 and DM 2 strains) was studied. Possible changes in outer membrane protein expression, permeability to cephaloridine, active efflux, and hydrolytic activity of beta-lactamase-crude extracts were evaluated under the influence of ciprofloxacin, sodium salicylate, and 2,4-dinitrophenol. Results were compared with those of the effect of the same three chemicals on a normally beta-lactamase-inducible wild-type C. freundii strain. The three assayed compounds decreased beta-lactamase hydrolysis on cephaloridine in both the two clinical isolates as well as in the wild-type strain. However, only the DM 1 and DM 2 strains showed increased susceptibility to beta-lactams. Sodium salicylate and 2,4-dinitrophenol, but not ciprofloxacin, reduced the expression of a 45-kDa outer membrane protein in the three studied strains, which was accompanied by a 4- to 20-fold diminution in permeability to cephaloridine. In conclusion, two mar RAB inducers and ciprofloxacin induced the Mar phenotype and repressed AmpC beta-lactamase synthesis in the DM 1 and DM 2 clinical isolates.
Asunto(s)
2,4-Dinitrofenol/farmacología , Ciprofloxacina/farmacología , Citrobacter freundii/efectos de los fármacos , Salicilatos/farmacología , beta-Lactamasas/biosíntesis , beta-Lactamas/farmacología , Citrobacter freundii/enzimología , Citrobacter freundii/aislamiento & purificación , Farmacorresistencia Bacteriana , Inducción Enzimática/efectos de los fármacos , Humanos , beta-Lactamasas/metabolismoRESUMEN
The effect of salicylate, a marRAB inducer, on the resistance to beta-lactams was characterized in an AmpC beta-lactamase hyperproducer Morganella morganii clinical isolate (the M1 strain). Results were compared with those of the effect of salicylate in a wild-type M. morganii strain. Salicylate induced a decreased susceptibility to nalidixic acid, norfloxacin and tetracycline and simultaneously increased the susceptibility to beta-lactams apparently due to the repression of AmpC beta-lactamase synthesis in the M1 strain. Likewise, salicylate only repressed 46 kDa outer membrane protein expression in the wild-type strain, since the clinical isolate M1 did not express it.