Infection of Mice by Salmonella enterica Serovar Enteritidis Involves Additional Genes That Are Absent in the Genome of Serovar Typhimurium

<jats:title>ABSTRACT</jats:title> <jats:p> <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Salmonella enterica</jats:named-content> serovar Enteritidis causes a systemic, typhoid-like infection in newly hatched poultry and mice. In the present study, a library of 54,000 transposon mutants of <jats:italic>S.</jats:italic> Enteritidis phage type 4 (PT4) strain P125109 was screened for mutants deficient in the <jats:italic>in vivo</jats:italic> colonization of the BALB/c mouse model using a microarray-based negative-selection screening. Mutants in genes known to contribute to systemic infection (e.g., <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Salmonella</jats:named-content> pathogenicity island 2 [SPI-2], <jats:italic>aro</jats:italic> , <jats:italic>rfa</jats:italic> , <jats:italic>rfb</jats:italic> , <jats:italic>phoP</jats:italic> , and <jats:italic>phoQ</jats:italic> ) and enteric infection (e.g., SPI-1 and SPI-5) in this and other <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Salmonella</jats:named-content> serovars displayed colonization defects in our assay. In addition, a strong attenuation was observed for mutants in genes and genomic islands that are not present in <jats:italic>S.</jats:italic> Typhimurium or in most other <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Salmonella</jats:named-content> serovars. These genes include a type I restriction/modification system ( <jats:italic>SEN4290</jats:italic> to <jats:italic>SEN4292</jats:italic> ), the <jats:italic>peg</jats:italic> fimbrial operon ( <jats:italic>SEN2144A</jats:italic> to <jats:italic>SEN2145B</jats:italic> ), a putative pathogenicity island ( <jats:italic>SEN1970 to SEN1999</jats:italic> ), and a type VI secretion system remnant <jats:italic>SEN1001</jats:italic> , encoding a hypothetical protein containing a lysin motif (LysM) domain associated with peptidoglycan binding. Proliferation defects for mutants in these individual genes and in exemplar genes for each of these clusters were confirmed in competitive infections with wild-type <jats:italic>S.</jats:italic> Enteritidis. A Δ <jats:italic>SEN1001</jats:italic> mutant was defective for survival within RAW264.7 murine macrophages <jats:italic>in vitro</jats:italic> . Complementation assays directly linked the <jats:italic>SEN1001</jats:italic> gene to phenotypes observed <jats:italic>in vivo</jats:italic> and <jats:italic>in vitro</jats:italic> . The genes identified here may perform novel virulence functions not characterized in previous <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Salmonella</jats:named-content> models. </jats:p>