Bactericidal and Fungicidal Activity of N -Chlorotaurine Is Enhanced in Cystic Fibrosis Sputum Medium

Lung infections with multiresistant pathogens are a major problem among patients suffering from cystic fibrosis (CF). -Chlorotaurine (NCT), a microbicidal active chlorine compound with no development of resistance, is well tolerated upon inhalation. The aim of this study was to investigate the bactericidal and fungicidal activity of NCT in artificial sputum medium (ASM), which mimics the composition of CF mucus. The medium was inoculated with bacteria ( , including some methicillin-resistant [MRSA] strains, , and ) or spores of fungi ( , , , , , , , , , and sp.), to final concentrations of 10 to 10 CFU/ml. NCT was added at 37°C, and time-kill assays were performed. At a concentration of 1% (10 mg/ml, 55 mM) NCT, bacteria and spores were killed within 10 min and 15 min, respectively, to the detection limit of 10 CFU/ml (reduction of 5 to 6 log units). Reductions of 2 log units were still achieved with 0.1% (bacteria) and 0.3% (fungi) NCT, largely within 10 to 30 min. Measurements by means of iodometric titration showed oxidizing activity for 1, 30, 60, and >60 min at concentrations of 0.1%, 0.3%, 0.5%, and 1.0% NCT, respectively, which matches the killing test results. NCT demonstrated broad-spectrum microbicidal activity in the milieu of CF mucus at concentrations ideal for clinical use. The microbicidal activity of NCT in ASM was even stronger than that in buffer solution; this was particularly pronounced for fungi. This finding can be explained largely by the formation, through transhalogenation, of monochloramine, which rapidly penetrates pathogens.