Mmt. Perez et al., Decreased production of AmpC-type beta-lactamases associated with the development of resistance to quinolones in Citrobacter freundii strains, MICROB DR R, 5(4), 1999, pp. 235-240
The effect of fluoroquinolones in Citrobacter freundii strains that results
in a decreased expression of cephalosporin-hydrolysing beta-lactamases was
studied. Resistance to broad-spectrum cephalosporins and penicillins in tw
o C, freundii clinical isolates was associated with moderate production of
chromosomal AmpC-type-beta-lactamase in addition to changes in the outer me
mbrane proteins profile with respect to wild-type C. freundii strains. Ten
quinolone-resistant mutants were derived from the two clinical isolates usi
ng increasing fluoroquinolone concentrations. The level of susceptibility t
o cephalosporins and meropenem of these 10 mutants was increased and was as
sociated with a 3.6-32% diminution in the hydrolyzing activity of their per
iplasmic extracts containing beta-lactamases on cephaloridine as compared w
ith those from their parent strains, Susceptibility to cephalosporins and m
eropenem, as well as the expression of chromosomal AmpC-type-beta-lactamase
in C, freundii strains, was influenced by the exposure to quinolones.