Describe the mechanisms of action and spectra of coverage for these two preparations.

Povidone-iodine releases free iodine, which enters microbial cells through their cell membranes, causing cell death. Up to 5 minutes of contact time is required for microbial uptake of the free iodine and cell death. It should therefore be allowed to completely dry on the skin surface before starting surgery. The activity of povidone-iodine ends after it has dried. Povidone-iodine is microbicidal for gram-positive and gram-negative bacteria, fungi, viruses, protozoa, and yeasts. At lower concentrations, chlorhexidine gluconate is bacteriostatic, by binding to microbial cell walls with subsequent osmotic disequilibrium. At higher concentrations, it induces precipitation of intracytoplasmic organelles and cell death. Chlorhexidine gluconate is microbicidal for gram-positive and gram-negative bacteria, facultative anaerobes, aerobes, and yeast.