Iron acquisition by Cryptococcus neoformans.

Iron is an essential element for the growth and metabolism of microbial cells. Most pathogenic microbes elaborate powerful iron chelating agents (siderophores) to mobilize iron from ferric ligands. The pathogenic yeast, Cryptococcus neoformans has not been found to produce siderophores and its mechanism of iron acquisition is unknown.

A changing pattern of susceptibility of Xanthomonas maltophilia to antimicrobial agents: implications for therapy.

The in vitro susceptibilities of 130 Xanthomonas maltophilia isolates to 12 antibiotics--trimethoprim-sulfamethoxazole, minocycline, ticarcillin-clavulanate, ceftazidime, cefoperazone, cefoperazone-sulbactam, imipenem, ciprofloxacin, and the investigational quinolones PD 117558, PD 117596, PD 127391, and sparfloxacin--were determined by a microtiter broth dilution technique. Other than the investigational quinolones, the most active antibiotics were minocycline, trimethoprim-sulfamethoxazole, and ticarcillin-clavulanate, in order. However, the first two were not bactericidal, while about half of the isolates exhibited intermediate susceptibility to ticarcillin-clavulanate.

Regulation of cryptococcal capsular polysaccharide by iron.

Iron is tightly controlled in mammalian tissues and regulates virulence factors in various pathogenic organisms. The influence of Fe availability upon production of cryptococcal capsular polysaccharide was studied. Polysaccharide, measured as cell-bound glucuronyl residues, increased more than threefold as available Fe in the culture medium was varied from repletion to tight sequestration and depletion in five incremental steps.