A method of treating cancer includes administering a dose of a chemotherapy agent in combination with a dose of a composition consisting essentially of attenuated Salmonella typhimurium. The dose of the chemotherapy agent is lower than a maximum effective dose of the chemotherapy agent. The combination provides a synergistic reduction in tumor burden when compared to the reduction in tumor burden provided by administration of an equivalent dose of the chemotherapy agent without the composition consisting essentially of attenuated Salmonella typhimurium.