Concept Map Creation On Intracellular Pathogens (Salmonella And Typhoid Fever) populate the concept map with terms from the lecture PowerPoint and draw/lab

populate the concept map with terms from the lecture PowerPoint and draw/label any connections between terms.

1/30/22

1

BIOL 315: Salmonella and
Typhoid fever

Dr. Sean Murray

Western Blot

Typhoid Fever

Typhoid Fever
•  Salmonella Typhi: only infects humans
•  CDC estimates 21 million cases per year world wide

with 200,000 deaths
•  400 cases per year in USA (most traveled to developing

countries)

Gastroenteritis
•  Salmonella Typhimurium: broad host range
•  CDC estimates 6.5 million cases a year in USA

with ~9,000 deaths from gastroenteritis
•  1/3 of all gastroenteritis infections caused by

Salmonella
•  CDC: 15 Salmonella infections per 100,000

people in USA

Typhoid Fever
•  Salmonella Typhi
•  Fecally contaminated food/water
•  1-4 weeks post-ingestion for symptoms
•  Multiply in spleen, liver
•  High fever, chills, convulsions, delirium, and

anorexia for 2-3 weeks
•  Pass from liver to gall bladder to intestine,

where it may ulcerate the intestinal mucosa
(fatal)

•  Treatment: antibiotics

1/30/22

2

Typhoid Mary, early 1900s

•  Salmonella can persist in the gall
bladder, and may be shed in feces

•  Chef Typhoid Mary was a carrier
•  She infected many people as she

worked at hotels, restaurants, hospitals
•  Arrested twice, spent the rest of her life

in prison after the second arrest

Gastroenteritis

•  Salmonella Typhimurium
•  Contaminated poultry/eggs

–  Caesar salad, raw eggs
•  Nausea, vomiting 6-24 hours post ingestion
•  Followed by abdominal pain, diarrhea, fever
•  Symptoms last 1 week
•  Shed Salmonella in feces for up to 3 months
•  1-3% of people shed for 1 year
•  If enters bloodstream, septic shock (rare)
•  Antibiotics not normally prescribed

Species infected by Salmonella

•  Humans (Typhi)
•  Humans, mice, cows, most mammals,

C. elegans (Typhimurium)

Salmonella Invasion of intestinal epithelium

1/30/22

3

TIIISS injects proteins into mammalian
cells that are NOT normally phagocytic to

induce phagocytosis of bacterium

Galan and Wolf-Watz, Nature, 2006

Type III-secretion system (TIIISS)

Galan and Wolf-Watz, Nature, 2006

Secretion protein complex is sequentially assembled
starting with the inner membrane, outer membrane,

periplasm, and finally the extracellular domains

Galan and Wolf-Watz, Nature, 2006

Invasion of intestinal epithelium

1/30/22

4

Holden, Traffic, 2002

Invading
macrophages

Paul (Ed.), Fundamental Immunology, 2003

Holden, Traffic, 2002

Salmonella
Containing
Vacuoles

Holden, Traffic, 2002

Salmonella Pathogenicity Islands SPI-1 and SPI-2
encode two different TIIISS that were horizontally
acquired (different GC content than chromosome);

pSLT is self-transmissible
pSLT

Spi-1
Spi-2

Salmonella
chromosome

Genome = chromosome plus plasmid

How does Salmonella adapt to
being inside or outside host cells?

In bacterial
membrane:

In bacterial
cytoplasm:

PhoQ

PhoP

(sensor)

(transcription factor)

1/30/22

5

PhoQ is activated by molecular signals inside host cell

PhoP becomes activated inside macrophages: Activated
PhoP represses the transcription of SPI-1 TIIISS prg

genes(PhoP-repressed genes); shuts off SPI-1 TIIISS so
SPI-2 TIIISS can protect Salmonella containing vacuoles

Galan and Wolf-Watz, Nature, 2006

Salmonella virulence factors

•  PhoQ/PhoP, SPI-1 TIIISS, SPI-2 TIIISS
•  Salmonella also contains a virulence

plasmid called pSLT
•  SPI-1 TIIISS is needed for invasion but

not persistence
•  SPI-2 TIIISS, pSLT, and PhoP/Q are

required for persistence (most important
factors for causing disease)

Summary virulence factors

•  SPI-1 TIIISS is needed for oral invasion,
but is not needed if Salmonella injected
directly into the bloodstream

•  SPI-2 TIIISS, PhoP/Q, and pSLT are
needed for survival within host cells
– They protect Salmonella containing

vacuoles

SPI-1 TIIISS
Induces membrane
ruffling, entry

SPI-2 TIIISS,
PhoQ/PhoP,
pSLT proteins
Protect
Salmonella-
Containing
Vacuoles

Adadpted from Paul (Ed.), Fundamental Immunology, 2003

Looking for this or a Similar Assignment? Click below to Place your Order