The Salmonella pathogenicity island 1 and Salmonella pathogenicity island 2 type III secretion systems play a major role in pathogenesis of systemic disease and gastrointestinal tract colonization of Salmonella enterica serovar Typhimurium in the chicken.

Salmonella enterica serovar Typhimurium infection of chickens is a major public and animal health problem. In young chicks, S. Typhimurium infection results in severe systemic infection; in older chicks, infection results in prolonged gastrointestinal tract colonization. Here we determined the role of the Salmonella pathogenicity island 1 (SPI-1) and Salmonella pathogenicity island 2 (SPI-2) type III secretion systems in systemic infection and gastrointestinal tract colonization of the chicken though experimental infection of chicks with a S. Typhimurium strain with mutations in the genes encoding the secretion system machinery of SPI-1 (spaS) and SPI-2 (ssaU) that prevent secretion of effector proteins. In 1-day-old chicks, mutation of SPI-2 lead to a decrease in both systemic bacterial numbers and pathology, although no difference in gastrointestinal numbers was observed. Mutation of SPI-1 had little effect in 1-day old chicks. In 1-week-old animals the SPI-2 mutants could not be detected systemically and colonized the gastrointestinal tract only in low numbers in comparison with the parent strain, and was cleared in 1 week. The SPI-1 mutant showed greatly reduced levels of systemic infection, and colonized the gastrointestinal tract at a lower level than the parent strain. The findings show that the SPI-2 type III secretion system is required for systemic S. Typhimurium infection in both infection models, and that it plays a significant role in gastrointestinal colonization. The SPI-1 system is involved in both systemic infection and gastrointestinal colonization, but does not appear absolutely essential for either infection process.

Jones MA ，Hulme SD ，Barrow PA ，Wigley P ... -  《AVIAN PATHOLOGY》

Salmonella enterica serovar Enteritidis colonization of the chicken caecum requires the HilA regulatory protein.

Invasion of Salmonella into intestinal epithelial cells is believed to be essential for the pathogenesis of Salmonella infections. Invasion is mediated by genes located on the Salmonella pathogenicity Island I (SPI-1), which are needed for assembling a type three secretion system, that mediates injection of bacterial proteins into the cytosol of epithelial cells, resulting in cytoskeletal rearrangements and as a consequence invasion. HilA is the key regulator of the Salmonella Pathogenicity Island I. To assess the role of hilA in colonization of gut and internal organs in poultry, animals were infected with 10(8) CFU of a delta hilA mutant of S. Enteritidis and its parent strain at day of hatch. Very low numbers of delta hilA mutant strain were able to colonize the internal organs shortly after infection, but they were not eliminated from internal organs at 4 weeks post-infection. At that time, the colonization level of the wild type bacteria in internal organs was decreased to the same low level compared with delta hilA mutant strain bacteria. Shedding of the delta hilA mutant strain and colonization of the caeca was seriously decreased relative to the parent strain starting from Day 5 post-infection. At 4 weeks post-infection, the delta hilA mutant strain was more or less eliminated from the chicken gut, while the parent strain was still shed to a high level and colonized the caeca to a high extent (more than 10(7) CFU/g). It is concluded that hilA is involved in long-term shedding and colonization of S. Enteritidis in the chicken caeca.

Bohez L ，Ducatelle R ，Pasmans F ，Botteldoorn N ，Haesebrouck F ，Van Immerseel F ... -  《VETERINARY MICROBIOLOGY》

Salmonella enterica serovar Pullorum requires the Salmonella pathogenicity island 2 type III secretion system for virulence and carriage in the chicken.

Functional mutations were made in the type III secretion systems encoded by Salmonella pathogenicity island 1 (SPI 1) and Salmonella pathogenicity island 2 (SPI 2) of Salmonella enterica serovar Pullorum, the cause of pullorum disease in poultry. Their role in cell invasion in vitro, and in virulence in vivo was determined. The SPI 1 mutant showed decreased invasiveness for chicken cells but was capable of causing disease in orally infected 1-day-old chicks, although it showed some reduction in virulence. The SPI 2 mutant showed no reduction in invasiveness, but was fully attenuated for virulence in 1-day-old chicks, and was not detected following oral infection in 1-week-old chickens. Following intravenous infection, the SPI 2 mutant was also attenuated and cleared more rapidly than the parent strain. This indicates that S. Pullorum requires SPI 2 for virulence and persistence but SPI 1 appears to contribute to, but is not essential for, the virulence of S. Pullorum.

Wigley P ，Jones MA ，Barrow PA 《AVIAN PATHOLOGY》

TolC but not AcrB is essential for multidrug-resistant Salmonella enterica serotype Typhimurium colonization of chicks.

To study the role of the multidrug efflux system AcrAB-TolC in resistance of multidrug-resistant Salmonella enterica serotype Typhimurium (S. Typhimurium) phage type DT104 and DT204 strains to detergents and bile salts. To evaluate the importance of the inner membrane transporter AcrB and the outer membrane component TolC of this efflux system in the colonization of two multidrug-resistant S. Typhimurium DT104 and one DT204 strain in chicks. acrB and tolC mutants of multidrug-resistant S. Typhimurium DT104 and DT204 strains were constructed by insertional inactivation of the acrB gene and deletion of the tolC gene. MICs of detergent and bile salts were determined for the wild-type strains, the acrB and the tolC mutant strains, in presence and in absence of the efflux pump inhibitor Phe-Arg beta-naphthylamide. The effect of sodium choleate on the in vitro growth of these strains was also evaluated. The LD50s of the strains were measured in a day-old chicken model, inoculated with several doses (1 x 10(3) to 1 x 10(8) cfu) by the oral route, for 7 days post-inoculation. The colonization levels were assessed at the sublethal dose 7 days post-inoculation by determining the number of cfu of Salmonella in the faeces, caecum, spleen and liver. The decrease in resistance levels to bile salts was 64- to 256-fold higher for the tolC mutants than for the acrB mutants relative to those of the parental strains. Addition of choleate in culture medium did not affect the growth of the wild-type strains or that of the acrB mutants, but inhibited completely the growth of the tolC mutants. The LD50s were 1.0 x 10(6) and 1.2 x 10(7) cfu for one wild-type S. Typhimurium DT104 strain and the acrB mutant, respectively, and were >1.0 x 10(8) for the tolC mutants or the S. Typhimurium DT204 strains. In contrast to the acrB mutants, the tolC mutants were unable to colonize the caecum, spleen and liver after 1 week of infection. Moreover, in most chicks, no intestinal excretion was detected for the tolC mutants. The colonization levels of the acrB mutants were not significantly different from those of the wild-type strains. TolC but not AcrB appears to be essential for multidrug-resistant S. Typhimurium DT104 and DT204 colonization of chicks, which is in accordance with their respective roles in resistance to detergents and bile salts. Therefore, TolC could be a better target than AcrB for the development of efflux pump inhibitors.

Baucheron S ，Mouline C ，Praud K ，Chaslus-Dancla E ，Cloeckaert A ... -  《JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY》

The Contribution of Eimeria Coinfection and Intestinal Inflammation to Cecal Colonization and Systemic Spread of Salmonella Typhimurium Deficient in Tetrathionate Reductase or Type III Secretion Systems Salmonella Pathogenicity Island 1 or 2.

Intestinal inflammation may provide a growth advantage for and enhance its systemic spread in chickens. triggers intestinal inflammation in the host by using type III secretion systems (T3SS) and produces the inflammatory end product tetrathionate. In mice, tetrathionate respiration confers a growth advantage for Typhimurium over the competitive microbiome in the inflamed intestine. Coccidia also promote intestinal inflammation and enhance intestinal growth and systemic spread in chickens. The objective of this study was to evaluate the contribution of inflammation, induced by spp. or Typhimurium, to colonization and dissemination in chickens. In addition, the fitness costs associated with defects in tetrathionate reductase and T3SS associated with Pathogenicity Island 1 or 2 (SPI-1 or SPI-2) were evaluated in competition experiments with wild-type strain, with or without coinfection. One-day-old specific-pathogen-free chickens were orally inoculated with a sham inoculum or with 4 × 10 oocysts cocktail of , , , and . At 6 days of age, birds were orally administered a 1:1 ratio of Typhimurium wild-type and mutant deficient in tetrathionate reductase, SPI-1, or SPI-2 (10 colony forming units/bird). Ceca, livers, and drumsticks were collected at 3, 7, 14, and 42 days after infection, for bacteriology. Intestinal inflammation was scored by histology. Significantly higher intestinal inflammation was observed in challenge groups compared with the control. However, there were no significant differences in intestinal inflammation scores between groups coinfected with both spp. and Typhimurium and birds infected with alone, and coinfection did not increase prevalence or abundance. Contrary to mouse studies, tetrathionate reductase did not enhance Typhimurium cecal colonization or systemic spread in chickens. SPI-1 and SPI-2 played a significant role in dissemination and cecal colonization in chickens, respectively.

Rimet CS ，Maurer JJ ，Berghaus RD ，Jordan BJ ，da Silva LHA ，Stabler LJ ，Johnson KK ，Tensa LR ，Segovia KM ，França MS ... -  《-》