Studies on the sub-mic of β-lactam Antibiotics: III. Bactericidal activity in elderly serum

Abstract

We studied the activity of β-lactam antibiotics at a sub-minimum inhibitory concentration (sub-MIC) in elderly serum. Mixtures containing serum (60 μl), antibiotic solution (10 μl) and bacterial suspension (10 μl) were incubated for 4 h at 37°C. The colony forming unit (CFU) was determined to evaluate bactericidal activity. Bactericidal activity in elderly serum was similar to that in normal serum against Proteus mirabilis T-250, Pseudomonas aeruginosa and Staphylococcus aureus. However, stronger bactericidal activity against P. mirabilis T-277 and weaker against Escherichia coli and Klebsiella pneumoniae were observed in elderly serum. Bactericidal activity in elderly serum was Iheat-labile, and lysozyme was thought to play some role in its augmentation. Piperacillin, cefoperazone and cefbuperazone showed bactericidal or bacteriostatic activity in nutrient broth, normal serum and elderly serum at a concentration of 1/4 MIC. While carbenicillin, cefazolinand cefmetazole slightly inhibit ed the growth of bacteria in nutrient broth, they showed hardly any bactericidal activity in normal and elderly serum. © 1988, Japanese Society of Chemotherapy. All rights reserved.