PubMed · 5818929
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K Shibata, T Hanai, K Yoshida, M Ashikari, M Fujii. 1969. [Peritonitis].. https://pubmed.ncbi.nlm.nih.gov/5818929/
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First- and second-derivative spectrophotometry, with a zero-crossing technique of measurement, has been used for the quantitation of two-component mixtures of cephaloridine and cephalothin Na, which are cephalosporins with closely overlapping spectral bands. Beer's Law is followed for up to 28 and 36 micrograms/mL of cephaloridine in the first- and second-derivative modes, respectively, and up to 36 micrograms/mL of cephalothin Na in both modes. Detection limits at the 0.05 level of significance were calculated to be 0.13 and 0.37 micrograms/mL of cephaloridine and cephalothin Na, respectively, in the first-derivative mode, and 0.25 and 0.29 micrograms/mL, respectively, in the second-derivative mode. The recovery of these antibiotics in mixtures of injectable dosage forms is also reported.
Three Pseudomonas aeruginosa strains which constitutively produced chromosomal (Id, or Sabath and Abraham) beta-lactamase in large amounts were resistant to latamoxef (moxalactam) MICs, 128-256 mg/l). Their beta-lactamase-basal mutants, which produced 1200-18,000-fold less enzyme, were latamoxef-sensitive (MICs, 4-16 mg/l), suggesting that the enzyme caused the resistance of the parent organisms. Latamoxef was a feeble substrate of the enzyme (kcat less than 0.5/min) but reacted to form a stable complex that lacked catalytic activity against benzylpenicillin. The complex was isolated by gel filtration and was shown to be stable to isoelectric focusing, suggesting a covalent link between the enzyme and latamoxef. During incubation the complex underwent a slow breakdown, regenerating active enzyme. This breakdown obeyed first-order kinetics, and the half-life of the inactivated form was 19 +/- 1 min at 37 degrees C. Binding of antibiotic molecules in this complex may contribute to the latamoxef-resistance observed in the beta-lactamase-derepressed strains. This 'covalent trapping' should be distinguished from the 'non-covalent trapping' proposed elsewhere as a general mechanism of beta-lactamase-mediated resistance to reversibly-bound weak-substrate beta-lactams.
The effect of antibody on the reversible deactivation of the beta-lactamase (penicillin amino-beta-lactamhydrolase, EC 3.5.2.6) from Staphylococcus aureus has been studied using quinacillin and cephaloridine as substrates. The latter has been shown to exhibit the characteristics of an A-type substrate Citri, N., Samuni, A. and Zyk, N. (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 1048-1052) and reversibly to lower the activity of the enzyme towards benzylpenicillin in a manner analogous to quinacillin. Both divalent and monovalent antibodies reduce the activity of the lactamase to 60% of the native value in the absence of substrate. The reduction by monovalent antibody is slow (t1/2 approximately equal to 25 min). Both divalent and monovalent antibodies modify the time-course of reversible deactivation independently of being added before or subsequent to deactivation by substrate. The full recovery of activity is delayed in the case of quinacillin and accelerated for cephaloridine. The activity against benzylpenicillin in the deactivated states is unaffected. These effects are shown to reflect the changed rates of hydrolysis of the two substrates in the presence of antibody. The effect of antibody is mediated by minor conformational change. Continuous assays for following the hydrolysis of quinacillin and cephaloridine by optical rotation are reported.