Gram stain: negative Cell shape: bacillus Arrangement: Oxygen requirements: facultative anaerobe Motility: most are motile Other: This genus actually is considered to contain only one species but there are over 2,000 serotypes, many with their own names...and ALL considered pathogenic to some degree! Non-lactose fermenter, Simmon's citrate positive, H2S production positive.
Habitat: insects, reptiles (there is a 90% carriage rate for pets), birds, cows, humans.
Pathogenicity: Causes "salmonellosis" - one of the most common forms of foodborne illness with approx. 2,000,000 cases in the US each year. Pass through stomach to colon and lower small intestine; penetrate mucosa and pass to underlying tissues causing inflammatory response. This response leads to increased fluid secretion and decreased absorption causing diarrhea, abdominal pain, nausea, vomiting, moderate fever.
The most virulent serotype (S. typhi) causes typhoid fever. This serotype is spread ONLY through feces of humans. High fever, headache, diarrhea in 2nd and 3rd weeks. Recovered patients may become chronic carriers harboring pathogen in gall bladder (Typhoid Mary).
Diagnosis is isolation of bacteria from patient's fecal material.
Transmission: fecal-oral route or contaminated food products: eggs and poultry, milk, Brewer's yeast, protein supplements.
Salmonella spp.
