Synergistic Antibacterial Activity of a New Quinolone, T-3762, and Human Gamma Globulin Against Intracellular Salmonella

The bactericidal activity of antibacterial agents against intracellular bacteria using aSalmonella-lined macrophage model (TtT/M-87), established from mouse pituitary tumor-associated macrophages, was investigated in this study. Because a virulent strain ofSalmonella enteritidis 116-54 is able to proliferate in phagocytized macrophages, the bactericidal activity against intracellular bacteria can be determined using this model. We found that a new quinolone, T-3762, has strong bactericidal activity against virulentS. enteritidis in macrophages. The bactericidal activity of T-3762 was augmented by the addition of human γ-globulin. The combination of T-3762 and human γ-globulin showed significantly higher bactericidal activity than that of ofloxacin and human γ-globulin. These results suggest that T-3762 can penetrate mammalian cells in an active form and that human γ-globulin may be able to enhance the bactericidal activity of macrophages by opsonization of bacteria with antibody in the γ-globulin fraction.