Salmonella (non-typhoidal)
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High Yield Notes
17 pages
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USMLE® Step 1 style questions USMLE
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First Aid
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Diarrhea
Salmonella p. , 142
Fever
Salmonella spp. p. 147
Salmonella typhi p. , 142
Gastroenteritis
Salmonella spp. p. 142
Immune response
Salmonella / Shigella spp. p. 142
Peyer patches p. 369, 381, 392
Salmonella / Shigella invasion p. 142
Salmonella spp.
animal transmission p. 147
bloody diarrhea p. 176
encapsulated bacteria p. 125
food poisoning p. 175
Gram-negative algorithm p. 139
immunodeficient patients p. 116
intracellular organism p. 125
osteomyelitis p. 177
penicillins for p. 185
reactive arthritis p. 475
Shigella spp. vs p. 142
splenic dysfunction p. 96
taxonomy p. 122
TMP-SMX for p. 191
type III secretion system p. 127
Salmonella typhi p. , 142
Shigella spp.
vs Salmonella spp. p. 142
Vaccines p. 109
Salmonella typhi p. , 142
Virulence factors
Salmonella/Shigella p. , 142
Vomiting
Salmonella spp. p. 147
Transcript
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Salmonella is a bacterium belonging to the family Enterobacteriaceae.
There are two main species: Salmonella bongori and Salmonella enterica, and the latter has six subspecies.
One of the subspecies is enterica, which has over 2500 serotypes that can be divided into two main groups based on the clinical symptoms they cause- so typhoidal or non-typhoidal Salmonella.
The non-typhoidal group, can infect humans and animals and cause a variety of disease states.
But, the most common serotype, Salmonella enteritidis, causes intestinal inflammation, called gastroenteritis, or commonly called “food poisoning”.
OK, but generally, Salmonella are encapsulated gram-negative, rod bacteria – meaning, they have a polysaccharide layer outside the cell envelope and look like little red or pink sticks on a gram stain.
They’re facultative intracellular pathogens, meaning they can live both outside or inside of its host’s cells.
And have flagella, making them motile, but don’t form spores.
They’re also facultative anaerobes, so they can undergo respiratory and fermentative metabolism; and they can ferment glucose but not lactose; are oxidase negative, and produce hydrogen sulfide gas.
And while a variety of media can be used to selectively identify Salmonella, among them is Triple Sugar Iron agar which produces a black precipitate when hydrogen sulfide is produced.
Now, once Salmonella is ingested and reaches the distal ileum of the small intestine, it tends to target the epithelial layer of the mucosal lining where it uses surface appendages to adhere to microfold cells, or M-cells.
And these M-cells eat, or phagocytose, the bacteria from the intestinal lumen and spit it out into the underlying Peyer’s patches - a type of mucosal immune tissue that extends into the submucosa.
When encountering non-typhoidal Salmonella, the immune system responds strongly by releasing proinflammatory cytokines that recruit additional immune cells, particularly neutrophils.
This causes inflammation of the small intestines and the colon, called enterocolitis.
Summary
Salmonella is a rod-shaped, gram-negative bacteria of the Enterobacteriaceae family, which is known to cause salmonellosis infection. Non-typhoidal Salmonella (NTS) infections are the most common type of salmonellosis and are caused by several different strains of the bacteria like S. Enteritidis, and S. Newport. NTS infections are foodborne diseases and primarily spread through contaminated food and water. They cause symptoms of food poisoning like fever, diarrhea, abdominal cramps, vomiting, and headache. These symptoms can be severe and may lead to dehydration, sepsis, or even death.