Potentiation of bacterial killing activity of zinc chloride by pyrrolidine dithiocarbamate

Zinc has antimicrobial activity and zinc salts including zinc chloride (ZnCl₂) have been used for the control of oral malodor. In this study, we hypothesized that pyrrolidine dithiocarbamate (PDTC), a zinc ionophore, may enhance antimicrobial efficacy of ZnCl₂. The bactericidal effectiveness of ZnCl₂ alone (0.5–8 mM) or in combination with PDTC (1 or 10 μM) was evaluated by in vitro short (1 h) time-killing assays against Fusobacterium nucleatum and Porphyromonas gingivalis. Only a slight viability decrease was observed with ZnCl₂ or PDTC alone after 1-h incubation. By contrast, combination of ZnCl₂ and PDTC could achieve a more than 100-fold viability reduction compared with ZnCl₂ or PDTC alone in F. nucleatum and P. gingivalis. Therefore, PDTC greatly enhanced the bactericidal activity of ZnCl₂ against the oral malodor-producing bacteria. These results suggest that use of PDTC may be useful for enhancing bactericidal activity of antimalodor regimens of zinc salts.