Zinc has antimicrobial activity and zinc salts including zinc chloride (ZnCl(2)) 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 ZnCl(2). The bactericidal effectiveness of ZnCl(2) alone (0.5-8 mM) or in combination with PDTC (1 or 10 microM) 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 ZnCl(2) or PDTC alone after 1-h incubation. By contrast, combination of ZnCl(2) and PDTC could achieve a more than 100-fold viability reduction compared with ZnCl(2) or PDTC alone in F. nucleatum and P. gingivalis. Therefore, PDTC greatly enhanced the bactericidal activity of ZnCl(2) 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.