[Inhibition of cephalosporinase of enterobacteria by ceftriaxone].

Resistance of ceftriaxone, cefotaxime and cefmenoxime to inactivation by the chromosomal constitutive cephalosporinases of Enterobacter cloacae P99, Morganella morganii GN 1510 and Serratia liquefaciens 132 was determined using high performance liquid chromatography. The inhibitory properties of ceftriaxone against the same cephalosporinases were studied by determining the residual amount of cephalothin used as the substrate. With a 1:50 cephalosporinase-cephalosporin ratio, ceftriaxone was less resistant to hydrolysis than cefotaxime of cefmenoxime but showed stronger inhibitory properties.