The nomenclature has changed over the years and the

The nomenclature has changed over the years and the current one is as follows:
The genus Salmonella consists of two species, each containing multiple serovars. The two species are S.
enterica and S. bongori . S. enterica subspecies are differentiated on the basis of biochemical traits and
genomic relatedness. For example, we say S. enterica serovar Typhimurium and S. enterica serovar
Enteriditis. The Salmonella genus contains over 2,541 serovars!!!
Salmonella infections of man:
1. Enterocolitis (caused by many serotypes of S. enterica )
2. Enteric fever (known as typhoid and paratyphoid) caused by S. enterica serovar Typhi and S.
enterica serovar Paratyphi
1.1.1 Enterocolitis (Gastroenteritis)
Pathogenesis - Severity of infection and disease influenced by:
- dose of ingested organisms (a minimum of 10 5 is usually required for symptomatic infection)

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- state of host; highest incidence in young (<5 years), elderly, and in individuals with
predisposing conditions such as malnutrition, impaired immunity, underlying infection
- virulence of infecting strain
Short incubation period (6-48 h; usually 8-12 h); multiplication in the mucosa of small intestine and colon,
leading to inflammation with mononuclear response.
Clinical: - nausea, vomiting, profuse diarrhoea, abdominal pain
- fever (38-39 o C), chills, headache, myalgia
- recovery within 2-3 days
- septicemia, rare complication in susceptible hosts
Laboratory diagnosis: stool culture
Epidemiology:
- infection by ingestion of food or drink contaminated by poor handling practices
- animal products (poultry, eggs, meat, milk) and animals are major sources
- person to person spread may occur (e.g., in nurseries)
- most cases occur at home; institutional cases (e.g., nursing homes, schools rank second
- many cases undiagnosed and unreported
Treatment
Antimicrobials are not recommended in uncomplicated Salmonella enterocolitis. Antibiotic treatment
may prolong excretion of organisms in the stool and does not shorten the illness.
1.1.2 Enteric Fever (Typhoid and paratyphoid)
S. enterica serovar Typhi causes typhoid fever
S. enterica serovar Paratyphi causes paratyphoid fever

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Enteric fever is a severe generalized infection whose principal feature is multiplication in the lymphoid tissue.
Invasion of intestinal epithelium is followed by multiplication in mesenteric lymph nodes and entry into blood
stream. Hyperplasia and necrosis of intestinal lymphoid tissue (Peyer's patches) may lead to ulceration,
haemorrhage or perforation resulting in peritonitis, abscesses, etc. In untreated cases mortality is about 10%;
survivors usually become (1) convalescent carriers excreting bacteria for up to 3 months or (2) chronic carriers
(1-2% of cases) lasting over 6 months and occasionally lifelong.
Laboratory diagnosis is based on isolation of the organism from blood (1st week), stool and urine (2nd-3rd
week).