nitrocefin and Hemolysis

A series of substituted di-indolglyoxylamido-spermine analogues were prepared and evaluated for intrinsic antimicrobial properties and the ability to enhance antibiotic action. As a compound class, intrinsic activity was typically observed towards Gram-positive bacteria and the fungus Cryptococcus neoformans, with notable exceptions being the 5-bromo- and 6-chloro-indole analogues which also exhibited modest activity (MIC 34-50 μM) towards the Gram-negative bacteria Escherichia coli and Klebsiella pneumoniae. Several analogues enhanced the activity of doxycycline towards the Gram-negative bacteria Pseudomonas aeruginosa, E. coli, K. pneumoniae and Acinetobacter baumannii. Of particular note was the identification of five antibiotic enhancing analogues (5-Br, 7-F, 5-Me, 7-Me, 7-OMe) which also exhibited low to no cytotoxicity and red blood cell haemolytic properties. The mechanisms of action of the 5-Br and 7-F analogues were attributed to the ability to disrupt the integrity of, and depolarize, bacterial membranes.

Topics: Anti-Bacterial Agents; Cell Line; Cell Membrane Permeability; Cell Survival; Cephalosporins; Gram-Negative Bacteria; Hemolysis; Humans; Hydrolysis; Indoles; Microbial Sensitivity Tests; Signal Transduction; Spermine

Eugenol, the principal chemical component of clove oil from Eugenia aromatica has been long known for its analgesic, local anesthetic, anti-inflammatory, and antibacterial effects. The interaction of the eugenol with ten different hydrophobic and hydrophilic antibiotics was studied against five different Gram negative bacteria. The MIC of the combination was found to decrease by a factor of 5-1000 with respect to their individual MIC. This synergy is because of the membrane damaging nature of eugenol, where 1mM of its concentration is able to damage nearly 50% of the bacterial membrane. Eugenol was also able to enhance the activities of lysozyme, Triton X-100 and SDS in damaging the bacterial cell membrane. The hydrophilic antibiotics such as vancomycin and beta-lactam antibiotics which have a marginal activity on these gram negative bacteria exhibit an enhanced antibacterial activity when pretreated with eugenol. Reduced usage of antibiotics could be employed as a treatment strategy to slow down the onset of antibiotic resistance as well as decrease its toxicity. Experiments performed with human blood cells indicated that the concentration of eugenol used for the combination studies were below its cytotoxic values. Pharmacodynamic studies of the combinations need to be performed to decide on the effective dosage.

Topics: Anti-Infective Agents; Bacteriolysis; Cell Membrane; Cephalosporins; Drug Synergism; Enterobacteriaceae; Eugenol; Hemolysis; Hydrophobic and Hydrophilic Interactions; Indicators and Reagents; Microbial Sensitivity Tests; Pseudomonas aeruginosa; Syzygium