Constitutively Expressed phoP Inhibits Mouse‐Virulence of Salmonella typhimurium in an Spv‐Dependent Manner

Abstract

In Salmonella typhimurium, the transcription of several virulence genes including spvB is regulated by the PhoP/PhoQ regulatory system. To further examine the relationship between the PhoP/PhoQ and Spy systems for virulence in mice, we examined a non-polar phoP mutation combined with different virulence plasmid genotypes for effects on virulence of S. typhimurium in the mouse model. PhoP-/Spv+ and PhoP-/ Spv-mutants were not detectably recovered from the spleens of subcutaneously or orally inoculated mice. The phoP gene constitutively expressed from the lacZ promoter of a low copy number vector (phor) only partially complemented the non-polar phoP mutation for mouse-virulence in both the Spy and Spy-backgrounds; both PhoPc strains exhibited virulence equal only to a PhoP)+/Spy-strain. Interestingly, in a PhoP+ background, the phoPc gene reduced splenic infection of the Spy but not Spv-salmonellae after subcutaneous or oral inoculation compared with the PhoP+ parents. Additionally, the phoPc gene in an Spy+ background reduced the net growth of salmonellae in macrophages in vitro; phoPc in an Spy-background was without effect. These data suggest that the constitutive expression of the phoP gene attenuates the virulence of S. typhimurium in mice in an Spy-dependent manner.

Effect of Constitutively Expressed phoP Gene on the Localization of Salmonella typhimurium within Mac‐1 Positive Phagocytes

“…We used three isogenic strains of S. typhimurium SR-11 in this study: Spv-r-the spv genes containing wildtype (X3306) (11,12,21); PhoP"-Spv+ containing phoi" (X3306 pPhoP) (22); and Spv -a deletion of spvRABCD replaced by the tet gene of pBR322 (UFllO) (21,22). Histological analysis was performed as described previously (21).…”

“…2). We previously reported that the constitutive expression of phol" leads to a decrease in the splenic CFU values of the Spv" but not of the Spv S. typhimurium after oral or subcutaneous inoculation of mice (22). In the present study, splenic CFU values at day five after oral inoculation or at day four after subcutaneous inoculation were as follows: Spv ' (oral), log J04.9±0.4 (n=9); PhoP" (oral), log I03.3±0.6 (n=7); Spv Toral), log J02.9±0.9 (n=9); Spv" (subcutaneous), log J07.5±0.3 (n=6); PhoP" (subcutaneous), log J06.0 ± 0.8 (n = 8); and Spv Tsubcutaneous), log J05.2±0.1 (n=9).…”

“…In this report, we demonstrated the difference in the ratios of intracellular localization of salmonellae of the wild-type of S. typhimurium and the wild-type with constitutive expression of the phoP gene from the lacZ promoter of a low copy number vector, pMW1l9, (PhoPC) or the spv-deleted strain of S. typhimurium using confocal laser scanning microscopy (CLSM) to analyze immunostained sections of mouse spleens. We used three isogenic strains of S. typhimurium SR-11 in this study: Spv-r-the spv genes containing wildtype (X3306) (11,12,21); PhoP"-Spv+ containing phoi" (X3306 pPhoP) (22); and Spv -a deletion of spvRABCD replaced by the tet gene of pBR322 (UFllO) (21,22). Histological analysis was performed as described previously (21).…”

In Vitro and in Vivo Stability of Plasmids in Attenuated Salmonella enterica serovar typhimurium Used as a Carrier of DNA Vaccine is Associated with its Replication Origin

“…To observe in vivo transfer of plasmid and immune induction, S. typhimurium harboring plasmid was orally administered [5]. Mice were deprived of drinking water and food for 5-6 h prior to the administration, and fed 30 min after the infection.…”

“…Stocker, Stanford University. S. typhimurium phoPdeficient strainχ3306 phoP {phoP:: aphT ∆Ter} [5] and rpoE-deficient strainχ3306 rpoE {rpoE:: aphT} [10] were derivatives of strain SR-11. All bacteria were routinely grown in Luria-Bertani (LB) broth [1% Bacto tryptone (Difco Laboratories, MI, USA) 0.5% Bacto yeast extract (Difco Laboratories) 1% sodium chloride (Nacalai Tesque, Kyoto, Japan)] or on an LB agar plate at 37°C.…”