Iron acquisition pathways and colonization of the inflamed intestine by Salmonella enterica serovar Typhimurium.

Salmonella enterica serotype Typhimurium is able to expand in the lumen of the inflamed intestine through mechanisms that have not been fully resolved. Here we utilized streptomycin-pretreated mice and dextran sodium sulfate (DSS)-treated mice to investigate how pathways for S. Typhimurium iron acquisition contribute to pathogen expansion in the inflamed intestine. Competitive infection with an iron uptake-proficient S. Typhimurium strain and mutant strains lacking tonB feoB, feoB, tonB or iroN in streptomycin pretreated mice demonstrated that ferric iron uptake requiring IroN and TonB conferred a fitness advantage during growth in the inflamed intestine. However, the fitness advantage conferred by ferrous iron uptake mechanisms was independent of inflammation and was only apparent in models where the normal microbiota composition had been disrupted by antibiotic treatment.

Encapsulated Brucella ovis Lacking a Putative ATP-Binding Cassette Transporter (ΔabcBA) Protects against Wild Type Brucella ovis in Rams.

This study aimed to evaluate protection induced by the vaccine candidate B. ovis ΔabcBA against experimental challenge with wild type B. ovis in rams. Rams were subcutaneously immunized with B. ovis ΔabcBA encapsulated with sterile alginate or with the non encapsulated vaccine strain. Serum, urine, and semen samples were collected during two months after immunization. The rams were then challenged with wild type B. ovis (ATCC25840), and the results were compared to non immunized and experimentally challenged rams. Immunization, particularly with encapsulated B. ovis ΔabcBA, prevented infection, secretion of wild type B. ovis in the semen and urine, shedding of neutrophils in the semen, and the development of clinical changes, gross and microscopic lesions induced by the wild type B. ovis reference strain. Collectively, our data indicates that the B. ovis ΔabcBA strain is an exceptionally good vaccine strain for preventing brucellosis caused by B. ovis infection in rams.

Protection Provided by an Encapsulated Live Attenuated ΔabcBA Strain of Brucella ovis against Experimental Challenge in a Murine Model.

This study aimed to evaluate the Brucella ovis ΔabcBA strain as a vaccine candidate in the murine model. BALB/c mice were subcutaneously or intraperitoneally immunized with a single dose or three doses of the B. ovis ΔabcBA strain and then were challenged with wild-type B. ovis. Single or multiple immunizations provided only mild protection, with significantly smaller numbers of wild-type B. ovis CFU in the livers of immunized mice but not in the spleens. Encapsulation of B. ovis ΔabcBA significantly improved protection against experimental challenges in both BALB/c and C57BL/6 mice. Furthermore, immunization with encapsulated B. ovis ΔabcBA markedly prevented lesions in the spleens and livers of experimentally challenged mice. These results demonstrated that the encapsulated B. ovis ΔabcBA strain confers protection to mice; therefore, this strain has potential as a vaccine candidate for rams.

Brucella ovis lacking a species-specific putative ATP-binding cassette transporter is attenuated but immunogenic in rams.

Ovine brucellosis caused by Brucella ovis is considered one of the most important reproductive diseases of rams worldwide. This study aimed to characterize the kinetics of infection of a ΔabcAB B. ovis mutant strain in rams. Twelve 1-year-old crossbred rams were used. Six rams were challenged with 2 mL of a suspension containing 1.2×10(9) CFU/mL of B. ovis strain ATCC25840 (wild type) by intraprepucial inoculation and additional 50 µL in each conjunctival sac of a suspension containing 1.2×10(10) CFU/mL of the same strain. The other six rams were challenged with an equivalent number of CFU of the mutant strain ΔabcAB B. ovis through the same routes. Serum samples for serology and semen and urine samples for bacteriologic culture and PCR were collected weekly during 24 weeks. At 24 weeks post infection, tissue samples were collected for bacteriologic culture and PCR. All rams inoculated with wild type or the ΔabcAB strain seroconverted at the fourth week post infection, remaining positive up to the 16th week post infection. PCR and bacteriology demonstrated that only rams inoculated with the wild type strain shed the organism in semen and urine. Lymphocytes from rams inoculated with wild type or ΔabcAB B. ovis had significantly higher proliferation in response to B. ovis antigens when compared with unstimulated controls. Tissue bacteriology and PCR detected B. ovis in all rams challenged with the wild type strain, whereas only one ΔabcAB-infected ram had a positive iliac lymph node sample by PCR.