Genome-wide fitness analysis identifies genes required for in vitro growth and macrophage infection by African and global epidemic pathovariants of Salmonella enterica Enteritidis

Abstract

Salmonella enterica Enteritidis is the second most common serovar associated with invasive non-typhoidal Salmonella (iNTS) disease in sub-Saharan Africa. Previously, genomic and phylogenetic characterization of S . enterica Enteritidis isolates from the human bloodstream led to the discovery of the Central/Eastern African clade (CEAC) and West African clade, which were distinct from the gastroenteritis-associated global epidemic clade (GEC). The African S . enterica Enteritidis clades have unique genetic signatures that include genomic degradation, novel prophage repertoires and multi-drug resistance, but the molecular basis for the enhanced propensity of African S . enterica Enteritidis to cause bloodstream infection is poorly understood. We used transposon insertion sequencing (TIS) to identify the genetic determinants of the GEC representative strain P125109 and the CEAC representative strain D7795 for growth in three in vitro conditions (LB or minimal NonSPI2 and InSPI2 growth media), and for survival and replication in RAW 264.7 murine macrophages. We identified 207 in vitro-required genes that were common to both S . enterica Enteritidis strains and also required by S . enterica Typhimurium, S . enterica Typhi and Escherichia coli , and 63 genes that were only required by individual S . enterica Enteritidis strains. Similar types of genes were required by both P125109 and D7795 for optimal growth in particular media. Screening the transposon libraries during macrophage infection identified 177 P125109 and 201 D7795 genes that contribute to bacterial survival and replication in mammalian cells. The majority of these genes have proven roles in Salmonella virulence. Our analysis uncovered candidate strain-specific macrophage fitness genes that could encode novel Salmonella virulence factors.

Modulation ofSalmonellavirulence by a novel SPI-2 injectisome effector that interacts with the dystrophin-associated protein complex

“…t.thurston@imperial.ac.uk. Thompson [10] Gallinarum [7] Weltevreden [7] Derby [6] Paratyphi A [6] Muenchen [5] Schwarzengrund [5] Kentucky [4] Mbandaka [4] Oranienburg [4] Stanleyville [4] Albany [3] Bovismorbificans [3] Others [139] Enteritidis [126] Typhi [113] Typhimurium [92] "I 1,4, [5],12:i:-" [46] Heidelberg [35] Newport [31] Anatum [29] Bareilly [24] Montevideo [21] Indiana [20] Senftenberg [20] Agona [16] Saintpaul [13] Adjame [11] Dublin [10] Infantis [10] Salmonella serovars 5000 (D)…”

“…SseM_5 [50] SseM_6_pseudo [40] SseM_7 [24] SseM_8 [20] SseM_9 [18] SseM_10 [14] SseM_11_pseudo [14] SseM_12 [13] SseM_13 [12] SseM_14 [11] SseM_15 [10] SseM_16 [10] SseM_17 [8] SseM_18 [8] SseM_19_pseudo [7] SseM_20 [7] SseM_21_pseudo [7] SseM_22 [7] SseM_23 [7] SseM_24 [6] SseM_25_pseudo [6] SseM_26 [6] SseM_27_pseudo [5] SseM_28 [5] SseM_29 [4] SseM_30 [4] Others [81] Missing [2] SseM variants…”

“…The associated gatekeeper complex, comprising SsaL, SsaM and SpiC, enables the injectisome to secrete the translocon proteins SseBCD while preventing the premature translocation of effectors; once the translocon pore is formed on the SCV membrane, the neutral pH of host cell cytosol is sensed and the signal is transduced into the bacterial cytosol to disassociate the gatekeeper complex from the export gate component SsaV to allow translocation of effectors [4][5][6]. Approximately 28 such effectors are translocated into host cells [7,8]; collectively these enable bacterial replication in host cells and suppress both innate and adaptive immune responses [1,[9][10][11].…”

A One-Pot Convenient RPA-CRISPR-Based Assay for Salmonella enterica Serovar Indiana Detection

“…Salmonella , a widely recognized foodborne pathogen with a global reach, represents a primary instigator of foodborne illness outbreaks, posing significant threats to human health and resulting in substantial economic ramifications annually [ 1 , 2 ]. The prevalence of Salmonella infections remains staggering, with over 93.8 million cases reported each year, accompanied by approximately 155,000 related fatalities [ 3 ].…”

Modulation of Salmonella virulence by a novel SPI-2 injectisome effector that interacts with the dystrophin-associated protein complex

“…The associated gatekeeper complex, comprising SsaL, SsaM, and SpiC, enables the injectisome to secrete the translocon protein SseBCD while preventing the premature translocation of effectors; once the translocon pore is formed on the SCV membrane, the neutral pH of host cell cytosol is sensed, and the signal is transduced into the bacterial cytosol to disassociate the gatekeeper complex from the export gate component SsaV to allow the translocation of effectors ( 4 – 6 ). Approximately 28 such effectors are translocated into host cells ( 7 , 8 ); collectively, these enable bacterial replication in host cells and suppress both innate and adaptive immune responses ( 1 , 9 – 11 ).…”