Abstract
Salmonella enterica subsp. enterica serovar Abortusequi is a frequently reported pathogen causing abortion in mares. In this study, the preventive and therapeutic effects of phage P(IZ) SAE-01E2 against S Abortusequi in a mouse model of abortion were investigated. Phage P(IZ) SAE-01E2 was stable at different temperatures (4 to 70°C) and pH values (pH 4 to 10) and could lyse the majority of the Salmonella serogroup O:4 and O:9 strains tested (25/28). There was no lysogeny-related, toxin, or antibiotic resistance-related gene in the genome of P(IZ) SAE-01E2. All of these characteristics indicate that P(IZ) SAE-01E2 has the potential for use in phage therapy. In in vivo experiments, 2 × 10(3) CFU/mouse of S Abortusequi ATCC 9842 was sufficient to lead to murine abortion (gestational day 14.5) within 48 h. A single intraperitoneal inoculation of P(IZ) SAE-01E2 (10(8) PFU/mouse, multiplicity of infection = 10(5)) 1 h before or after S Abortusequi challenge provided effective protection to all pregnant mice (10/10). After 24 h of treatment with phage P(IZ) SAE-01E2, the bacterial loads in both the placenta and the uterus of the infected mice were significantly decreased (<10(2) CFU/g) compared to those in the placenta and the uterus of the mice in the control group (>10(6) CFU/g). In addition, the levels of inflammatory cytokines in the placenta and blood of the mice in the phage administration groups were significantly reduced (P < 0.05) compared to those in the placenta and blood of the mice in the control group. Altogether, these findings indicate that P(IZ) SAE-01E2 shows the potential to block abortions induced by S Abortusequi in vivoIMPORTANCES Abortusequi is an important pathogen that can induce abortions in mares. Although S Abortusequi has been well controlled in Europe and the United States due to strict breeding and health policies, it is still widespread in African and Asian countries and has proven difficult to control. In China, abortions caused by S Abortusequi have also been reported in donkeys. So far, there is no commercial vaccine. Thus, exploiting alternative efficient and safe strategies to control S Abortusequi infection is essential. In this study, a new lytic phage, P(IZ) SAE-01E2, infecting S Abortusequi was isolated, and the characteristics of P(IZ) SAE-01E2 indicated that it has the potential for use in phage therapy. A single intraperitoneal inoculation of P(IZ) SAE-01E2 before or after S Abortusequi challenge provided effective protection to all pregnant mice. Thus, P(IZ) SAE-01E2 showed the potential to block abortions induced by S Abortusequi in vivo.