Salmonella enterica serovar Typhimurium ompS1 and ompS2 mutants are attenuated for virulence in mice

Abstract

Salmonella enterica serovar Typhimurium mutants with mutations in the ompS1 and ompS2 genes, which code for quiescent porins, were nevertheless highly attenuated for virulence in a mouse model, indicating a role in pathogenesis. Similarly, a strain with a mutation in the gene coding for LeuO, a positive regulator of ompS2, was also attenuated.

FIG. 1.

Sodium dodecyl sulfate-polyacrylamide gel showing outer membrane protein profiles for various S. enterica serovar Typhimurium strains. Lanes: 1, STM14028 (wild type)/pFMtrcleuO (plus 50 μM IPTG [isopropyl-β-d-thiogalactopyranoside]); 2, STMS23 (ΔompS2::Km)/pFMtrcleuO (plus 50 μM IPTG); 3, STM14028 (wild type)/pFMtrc12 (plus 50 μM IPTG); 4, STMR (ΔompR::Km); 5, STMR (ΔompR::Km)/pFM2001 (ompR); 6, STMZ (ΔenvZ::Cm); 7, STMZ (ΔenvZ::Cm)/pROZ (envZ); and 8, STMD (ΔompD::Km).

FIG. 2.

Phenotypes of S. enterica serovar Typhimurium STMS14 (ΔompS1::Km) and STMS23 (ΔompS2::Km) mutant strains. (A) LD₅₀s of S. enterica serovar Typhimurium strains in BALB/c mice after oral infection. The values are the means of three to four independent experiments. The LD₅₀ of the mutant with a deletion of the gene for LeuO, the positive regulator of ompS2, is also shown. (B) CII of mutants upon mixed infection with the wild-type strain in cultured HeLa cells. The CII was calculated by obtaining the ratio between the two strains in the output (intracellular bacteria recovered 3 h after infection) and dividing it by their ratio in the input (initial mixed inoculum). (C) CIP upon mixed infection of the J774.A1 macrophage line with either the STMS14 or the STMS23 mutant and the wild type. The CIP was calculated by obtaining the ratio between the two strains 24 h after infection and dividing it by their ratio 1 h 5 min after infection. For panels B and C, all values are means ± standard deviations of at least two experiments done in triplicate (P < 0.001 by Student's t test).