Bactericidal activity of micromolar N-chlorotaurine: Evidence for its antimicrobial function in the human defense system

N-Chlorotaurine, the main representative of long-lived oxidants found in th e supernatant of stimulated granulocytes, has been investigated systematica lly with regard to its antibacterial activity at different physiological co ncentrations for the first time. N-Chlorotaurine (12.5 to 50 mu M) demonstr ated a bactericidal effect i.e., a 2 to 4 log(10) reduction in viable count s, after incubation at 37 degrees C for 6 to 9 h at pH 7.0, which effect wa s significantly enhanced in an acidic milieu (at pH 5.0), with a 3 to log(1 0) reduction after 2 to 3 h. Moreover, bacteria were attenuated after being incubated in N-chlorotaurine for a sublethal time, as demonstrated with th e mouse peritonitis model. The supernatant of stimulated granulocytes exhib ited similar activity. Transmission electron microscopy revealed changes in the bacterial cell membrane and cytoplasmic disintegration with both react ing systems, even in the case of a mere attenuation. The results of this st udy suggest a significant bactericidal function of N-chlorotaurine and othe r chloramines during inflammation.