Ciprofloxacin inhibition of cefoxitin betalactamase induction in an Enterobacter cloacae strain.

The betalactamase activity of an Enterobacter cloacae strain was measured using subinhibitory concentrations of cefoxitin and ciprofloxacin respectively as enzyme inducer and induction inhibitor. Cultures of this strain were also exposed to different ceftriaxone concentrations either alone or in the presence of cefoxitin and/or ciprofloxacin. Ciprofloxacin at subinhibitory concentrations does not interfere with ceftriaxone's activity and is capable of neutralizing the antagonistic effect of cefoxitin on ceftriaxone. The enzyme assay and MS-2 System demonstrate ciprofloxacin's partial suppression of cefoxitin betalactamase induction in the E. cloacae strain tested.