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Category: Food Microbiology; Applied and Industrial Microbiology
Salmonella Species † , Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555818463/9781555816261_Chap10-1.gif /docserver/preview/fulltext/10.1128/9781555818463/9781555816261_Chap10-2.gifAbstract:
In recent years, the rapid advance of DNA/RNA sequencing technology has made whole-genomic sequencing a very promising tool in the investigation of foodborne outbreaks, as it can be used to assess the population structure of highly clonal, outbreak-related pathogens at a single-base resolution and can help identify temporal, geographical, and evolutionary origins of outbreaks. A study using a whole-genome single nucleotide polymorphism-based assay has demonstrated its discriminatory power by being able to distinguish between outbreak-related and non-outbreak-related cases that were associated with a multistate Salmonella Montevideo outbreak originating from salami made with contaminated red and black peppers. The resistance and survival of foodborne salmonellae to inactivation processes and hostile environments are often the reasons underlying many food-associated Salmonella outbreaks. The resistance that salmonellae demonstrate to heat, chemical sanitizers or preservatives, low pH, and water activity (aw) ultimately plays an important role in causing human disease. Enteric fever is a serious human disease associated with Salmonella Typhi and Salmonella Paratyphi, which are mainly transmitted from human to human via the fecal-oral route and are particularly well adapted for invasion and survival within host tissues. Antibiotic resistance in Salmonella spp. has been reported since the early 1960s, when most of the reported resistance was to a single antibiotic. Salmonella spp. continue to be a leading cause of foodborne illness. The situation has persisted because of the widespread occurrence of salmonellae in the natural environment and their prevalence in many sectors of the global food chain.
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Genetic map of Salmonella enterica virulence loci. Genomic islands are depicted on the chromosome relative to their position to housekeeping genes or specific tRNA. All 10 SPIs including SPI-6 through -10, which are only present in Salmonella serovars associated with enteric fever, are illustrated as circles with S. Typhi genomic islands attached to the map via arrows with dotted lines. Prophage genomes are also included in the map and are designated by “lollipop” symbols. Squares denote adhesions/fimbrial operons. More-detailed genetic organization of SPI1-5 is given in Figure 10.2 . doi:10.1128/9781555818463.ch10f1
Genetic map of Salmonella enterica virulence loci. Genomic islands are depicted on the chromosome relative to their position to housekeeping genes or specific tRNA. All 10 SPIs including SPI-6 through -10, which are only present in Salmonella serovars associated with enteric fever, are illustrated as circles with S. Typhi genomic islands attached to the map via arrows with dotted lines. Prophage genomes are also included in the map and are designated by “lollipop” symbols. Squares denote adhesions/fimbrial operons. More-detailed genetic organization of SPI1-5 is given in Figure 10.2 . doi:10.1128/9781555818463.ch10f1
Genetic organization of virulence genes present in SPI-1 through -5 and virulence plasmid. The genes and their organization into operons are shown with arrows demarcating operons and direction of transcription. The known functions of genes are depicted in this illustration with shading or pattern designating its function as described in the key below the schemas. Those genes with no known function are shown with white foreground. Type III effectors are bacterial proteins injected to host cell cytoplasm via T3SS. doi:10.1128/9781555818463.ch10f2
Genetic organization of virulence genes present in SPI-1 through -5 and virulence plasmid. The genes and their organization into operons are shown with arrows demarcating operons and direction of transcription. The known functions of genes are depicted in this illustration with shading or pattern designating its function as described in the key below the schemas. Those genes with no known function are shown with white foreground. Type III effectors are bacterial proteins injected to host cell cytoplasm via T3SS. doi:10.1128/9781555818463.ch10f2
Complex needle and base structure of the T3SS in Salmonella. (A) Transmission electron microscope image of the T3SS needle complex in S. Typhimurium. (B) A cut-away view and description of individual substructures of the needle complex. OR, outer ring; IR, inner ring. Bar = 10 nm. (Adapted from reference 191 .) doi:10.1128/9781555818463.ch10f3
Complex needle and base structure of the T3SS in Salmonella. (A) Transmission electron microscope image of the T3SS needle complex in S. Typhimurium. (B) A cut-away view and description of individual substructures of the needle complex. OR, outer ring; IR, inner ring. Bar = 10 nm. (Adapted from reference 191 .) doi:10.1128/9781555818463.ch10f3
Taxonomical schemes for Salmonella spp.
Taxonomical schemes for Salmonella spp.
Species within the Salmonella genus a
Physiological limits for the growth of Salmonella spp. in foods and bacteriological media
Physiological limits for the growth of Salmonella spp. in foods and bacteriological media
Examples of major foodborne outbreaks of human salmonellosis from dairy products
Examples of major foodborne outbreaks of human salmonellosis from dairy products
Examples of major foodborne outbreaks of human salmonellosis from fruits and vegetables
Examples of major foodborne outbreaks of human salmonellosis from fruits and vegetables
Examples of major foodborne outbreaks of human salmonellosis from meats and meat products
Examples of major foodborne outbreaks of human salmonellosis from meats and meat products
Examples of major foodborne outbreaks of human salmonellosis from fish and fish products
Examples of major foodborne outbreaks of human salmonellosis from fish and fish products
Examples of major foodborne outbreaks of human salmonellosis from eggs and egg products
Examples of major foodborne outbreaks of human salmonellosis from eggs and egg products
Examples of major foodborne outbreaks of human salmonellosis from other products
Examples of major foodborne outbreaks of human salmonellosis from other products
Human infectious doses of Salmonella a