Salmonella

Salmonella species are motile, non-lactose fermenting, hydrogen sulfide-producing gram-negative rods belonging to the Enterobacteriaceae family. The genus includes over 2,500 serotypes, with S. enteritidis and S. typhimurium causing most gastroenteritis cases, while S. typhi and S. paratyphi cause typhoid fever. Pathogenesis involves invasion of intestinal epithelial cells through M cells in Peyer's patches, leading to inflammatory diarrhea. Virulence factors include Type III secretion systems, flagella for motility, and capsular antigens. Clinical presentations range from self-limited gastroenteritis (fever, cramping, bloody diarrhea) to life-threatening typhoid fever with rose spots, hepatosplenomegaly, and potential complications like intestinal perforation. Diagnosis involves stool culture, blood culture for systemic disease, and serologic testing (Widal test for typhoid, though not highly specific). Treatment includes supportive care for gastroenteritis, while typhoid fever requires antibiotics (fluoroquinolones, azithromycin, or ceftriaxone). Prevention focuses on food safety, proper sanitation, and typhoid vaccination for travelers to endemic areas.