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

Abstract

Lung infections with multiresistant pathogens are a major problem among patients suffering from cystic fibrosis (CF). N-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 in vitro bactericidal and fungicidal activity of NCT in artificial sputum medium (ASM), which mimics the composition of CF mucus. The medium was inoculated with bacteria (Staphylococcus aureus, including some methicillin-resistant S. aureus [MRSA] strains, Pseudomonas aeruginosa, and Escherichia coli) or spores of fungi (Aspergillus fumigatus, Aspergillus terreus, Candida albicans, Scedosporium apiospermum, Scedosporium boydii, Lomentospora prolificans, Scedosporium aurantiacum, Scedosporium minutisporum, Exophiala dermatitidis, and Geotrichum sp.), to final concentrations of 10 7 to 10 8 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 2 CFU/ml (reduction of 5 to 6 log 10 units). Reductions of 2 log 10 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 Ͼ60 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.

N-Chlorotaurine, a Promising Future Candidate for Topical Therapy of Fungal Infections

“…A reduction by 2 log 10 was still achieved by 0.1 and 0.3% NCT for bacteria and fungi, respectively, largely within 10–30 min. Measurements by means of iodometric titration showed oxidizing activity over 1, 30, 60, and >60 min at a concentration of 0.1, 0.3, 0.5, and 1.0% NCT, respectively, which matched the killing tests [ 67 ].…”

“…Since inhaled NCT appears to be well tolerated, acute and chronic lung diseases, e.g., chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF), may become indications of interest. Therefore, we tested its bactericidal and fungicidal activity in artificial sputum medium (ASM; artificial CF-medium containing egg yolk emulsion, mucin type II from porcine stomach, salmon sperm-DNA, amino acids, diethylenetriamine penta-acetic acid, sodium chloride and potassium chloride [ 66 ]), mimicking the composition of cystic fibrosis mucus [ 67 ].…”

“…The medium was inoculated with bacteria ( S. aureus including some MRSA strains, P. aeruginosa , Escherichia coli ) or spores of fungi ( A. fumigatus , Aspergillus terreus , C. albicans , S. apiospermum , S. boydii , L. prolificans , Scedosporium aurantiacum , Scedosporium minutisporum , Exophiala dermatitidis , Geotrichum candidum ), and NCT was added at 37 °C. At a concentration of 1% (55 mM) NCT, bacteria and spores (10 7 –10 8 cfu/ml each) were killed within 10 and 15 min to the detection limit of 10 2 cfu/ml (reduction by 5–6 log 10 ) [ 67 ]. A reduction by 2 log 10 was still achieved by 0.1 and 0.3% NCT for bacteria and fungi, respectively, largely within 10–30 min.…”

“…NCT demonstrated broad-spectrum microbicidal activity in the milieu of CF mucus at concentrations ideal for clinical use. Microbicidal activity of NCT in ASM was even stronger than in buffer solution, particularly pronounced with fungi [ 67 ]. This can clearly be seen in Table 1 , where the integral method was used to reliably transform killing curves into one value [ 68 ].…”

Recent Advances in the Treatment of Scedosporiosis and Fusariosis

“…Individuals suffering from near-drowning events in water are also at risk of disease, which may be associated with central nervous system (CNS) involvement [ 19 ]. Species of Scedosporium , including S. boydii , S. apiospermum , and S. aurantiacum are among the most commonly recovered molds from respiratory secretions of patients with chronic pulmonary diseases such as cystic fibrosis (CF) and may lead to invasive disease [ 4 , 7 , 20 , 21 ].…”