Salmonella enterica
One-Sentence Definition
Salmonella enterica is a Gram-negative Enterobacterales pathogen encompassing typhoidal serovars (enteric fever) and thousands of non-typhoidal serovars causing gastroenteritis and invasive disease, structured by virulence Genomic Islands (SPI).
Taxonomy & Morphology
- Gram-negative bacillus; usually motile; lactose non-fermenter
- Serotyping by O (LPS) and H (flagellar) antigens — increasingly predicted from WGS
- Major pathovars: Typhi/Paratyphi vs non-typhoidal Salmonella (NTS: Typhimurium, Enteritidis, …)
Virulence Highlights
- SPI-1 — invasion of intestinal epithelium
- SPI-2 — intracellular survival in macrophages
- Additional SPIs, prophages, and plasmids modify host range and resistance
- Vi capsule in Typhi
Clinical Syndromes
- NTS: foodborne gastroenteritis; bacteremia in immunocompromised / infants
- Typhoid/paratyphoid: prolonged fever, systemic illness
- Focal infections (osteomyelitis, endovascular) possible
Diagnosis
- Stool/blood culture; selective media
- Serotyping or WGS-based serotype prediction
- AST for invasive/typhoidal cases — resistance rising globally
Treatment Notes (conceptual)
- Uncomplicated NTS gastroenteritis: often supportive (antibiotics can prolong carriage)
- Invasive / typhoidal: directed therapy; watch MDR/XDR typhoid epidemiology
AMR
- MDR plasmids historically (ACSSuT patterns); extensively drug-resistant Typhi clones with plasmid + chromosomal resistance
- Fluoroquinolone resistance via gyrase/topoisomerase mutations
- Links to Integrons and Plasmid ecology in agriculture/One Health (One Health)
Genomics & Computational Notes
- Classic model for Genomic Islands and Prophage Detection and Annotation
- Outbreak typing: cgMLST / SNP pipelines in PulseNet-style networks
- Recombination moderate; still use careful phylogenomics (Phylogenomics and Outbreak Typing)
Related Notes
- Escherichia coli · Horizontal Gene Transfer · Gastrointestinal Infections · MOC - Diseases by System
- MOCs: MOC - Bacteriology · MOC - Public Health & Epidemiology · MOC - Bioinformatics in Microbiology
Active Recall
- SPI-1 vs SPI-2 — invasion vs intracellular survival?
- When are antibiotics indicated for NTS diarrhea?
- Why is WGS replacing classic serotyping in reference labs?