Bactericidal activity of the organo-tellurium compound AS101 against Enterobacter cloacae

Objectives: The antibacterial effect of the organo-tellurium compound AS101 on the Gram-negative bacterium Enterobacter cloacae is shown in this study for the first time. Methods: The antimicrobial effect of the drug was shown by inhibition of growth, by inhibition of biofilm for-mation and by its ability to penetrate the bacterial cell and to cause damage and ultrastructural changes. Results: AS101 was found to be a bactericidal drug with MICs and MBCs of 9.4 mg/L. It inhibits bacterial growth and causes a six orders of magnitude decrease in viability in a protein-rich medium, but not in a protein-poorer medium, unless 2-mercaptoethanol is added. Subinhibitory concentrations inhibit motility and biofilm forma-tion. AS101 enters the bacterium through its porins and causes bacterial damage to Na+/K+ pumps and leakage of potassium, phosphorous and sulphur. Ultrastructural changes within the bacterial cell and on its surface demonstrate an incomplete surface with a concavity in the centre that looks like a hole from which aggregates are liberated as well as cell lysis. Conclusions: AS101 has antibacterial activity, which may be useful against E. cloacae and other species of Enterobacteriaceae as a substitute for current antibiotics that have become ineffective due to increasing bac-terial resistance