Salmonella + Shigella

Question 1

Salmonella classification (morphology; motility, enzymes, capsule etc)

Answer 1

Salmonella spp are

GN flagellated rod, encapsulated (esp S. typhi has Vi capsule)

Lactose neg + H2S +ve (black colonies)

Question 2

Which spp of Salmonella are found in cold blooded animals and in the environment?

Answer 2

The non-Sub group I Salmonella enterica spp

Question 3

Salmonella ___ are the ones that cause GI symptoms in humans and infect people thru contaminated food

Answer 3

Salmonella enterica (Enterica: typhoidal vs non typhoiddal)

Question 4

Non typhoidal Salmonella typically causes ___ (GI issue) and mainly infects humans through contaminated __

Answer 4

Non typhoidal Salmonella typically causes diarrhea (inflammatory) (GI issue) and mainly infects humans through contaminated poultry

recall the chicken in the Sketchy video

**Presentation: with watery diarrhea, abdominal pain, fever; blood, pus and mucus in stool**

Question 5

Because Salmonella enteritidis causes a self limited diarrhea, Rx for this infection is ___

Answer 5

Because Salmonella enteritidis causes a self limited diarrhea, Rx for this infection is NO antibiotics

Question 6

The most common causes of bacterial diarrhea and infection are __ and ___

Answer 6

Salmonella and Campylobacter

Question 7

Salmonella ___ and ___ cause a systemic syndrome called “typhoid fever”

Answer 7

S typhi and S paratyphi

Question 8

Typhoid fever is a systemic infection affecting the ___

Answer 8

Typhoid fever is a systemic infection affecting the RES (remember that it affects M-phages which are part of the RES)

Question 9

T/F: Diarrhea is a prominent feature of typhoid fever

Answer 9

For class: not really

For step: causes pea soup diarrhea

Question 10

S typhi is found only in humans (specifically in the ___ of asymptomatic carriers) and is contracted via ___

Answer 10

S typhi is found only in humans (specifically in the gallbladder of asymptomatic carriers) and is contracted via ingestion of contaminated food or water

Question 11

The incubation period of S typhi infection is ___ (days) and presentation includes __

Answer 11

The incubation period of S typhi infection is 5-21 (days) and presentation includes non specific symptoms (headache, malaise, sore throat etc)

Question 12

S typhi has characteristic ___ on pts abdomen ( hepatosplenomegaly, abdominal tenderness are also common)

Answer 12

S typhi has characteristic red spots on pts abdomen ( hepatosplenomegaly, abdominal tenderness are also common)

Question 13

Most common cause of death from S typhi infection is __

Which antibiotics are indicated for S typhi infection?

Answer 13

Most common cause of death from S typhi infection is intestinal hemorrhage and perforation

Antibiotics indicated for S typhi infection: ceftriaxone

(think of the typhi seagull wielding 3 axes)

Question 14

T/F: Salmonella typhi has a vaccine

Answer 14

True. there’s two in fact

Question 15

Describe the 2 vaccines for S typhi

Answer 15

Oal live attenuated Ty21a (thank you I’m 21)

Vi polysaccharide (taken from the bug’s capsule)

**know that there aren;t any vaccines for kids less than 2 yoa)**

Question 16

What is the presentation of infection with S paratyphi?

Answer 16

S paratyphi is, for all intents and purposes, exactly the same as typhi (the same way MAC is essentially TB except MAC is not transmissible)

Question 17

Salmonella are ___ (facultative/obligate) intracellular

What is the mechanism of infection?

Answer 17

Invasive and facultatively intracellular (recall the m=phage cages in the sketchy videos)

Mechanism of infection: Type III secretion system

**Note that NTS invades and stays in the cells. Typhi goes further thru the lymphatics**

Question 18

Salmonella typhi invasion is through the Type III secretion system in two parts:

First is for ___

2nd is for ___

Answer 18

Salmonella invasion:

Via type 3 secretion system (first part is the bug being able to enter into the host cell, the second part is that once the bug is inside the cell, it is contained in a vacuole, then it activates another Type III secretion system whose job is to promote the bug’s survival inside the host cell)

Question 19

The most important virulence factor in S typhi is the ___

Answer 19

The most important virulence factor in S typhi is the Vi capsule

**S typhi’s capsule allows Typhi to evade TLR4 and 5 binding because the LPS is kind of hidden/covered by the capsule**

Others:

Altered flagellin gene regulation: Evasion of TLR5

Genome degradation

Question 20

The main difference in the host response to S typhi vs NTS infection is ___

Answer 20

The main difference in the host response to S typhi vs NTS infection is inflammation

**Main difference between Salmonella typhi and NTS is that NTS are the guys that elicit a huge inflammatory response (hence the inflammatory diarrhea) whereas Typhi doesn’t do that and that’s how it spreads through the body**

Question 21

Inflammation induced by Salmonella confers a growth advantage over host commensals due to release of __ which allows the bug to scavenge for Fe unregulated

Answer 21

**salmochelin**

Enterobactins are bacterial proteins that aid in the bugs getting iron – note that enterobactin is released by normal gut flora

After exposure to Salmonella, the human host immune cells secrete IL22 that elicits the release of Lipocalin 2 from intestinal cells

Lipocalin 2 binds to enterobactin (and basically stops the gut flora them from scavenging for iron >> regulated growth

Salmonella produces Salmochelin (like salmonella just chillin and invading the host like its nothing) which is NOT bound by lipocalin 2, so the bugs can get all the iron and keep it moving

Question 22

The Salmonella Type 3 secretion systems SP1 and SP2 are for what?

Answer 22

SPI 1 – TTSS required for bacterial uptake

SPI 2 –TTSS required for intracellular survival and immune evasion

Question 23

Shigella morphology/enzymes/gram stain etc

Answer 23

Shigella: gram negative facultative intracellular rod

Lactose and H2S negative; green colonieson Hektoen agar

Question 24

The 4 most clinically significant Shigella spp are:

Answer 24

S sonnei

S flexneri

S dysenteriae

S boydii

Question 25

A common disease caused by S sonnei + S flexneri is ___

___ is the one that has Shiga toxin and causes dysentery so it is the most dangerous

Answer 25

A common disease caused by S sonnei + S flexneri is traveler’s diarrhea

S dysenteriae is the one that has Shiga toxin and causes dysentery so it is the most dangerous

Question 26

Most foodborne outbreaks in the US are ass’d with which Shigella spp?

The transmission of shigella is ___

Answer 26

S flexneri

Fecal - oral (can be sexually transmitted for this reason; resistant strains in men who have sex with men)

Question 27

Unlike Salmonella (which is acid labile) that requires high doses of bug to cause disease, Shigella (which is acid ___) requires a ___ amount of bug to cause disease

Answer 27

Unlike Salmonella (which is acid labile) that requires high doses of bug to cause disease, Shigella (which is acid stable) requires only a small amount of bug to cause disease

Question 28

Shigella presents in two phases, the early phase which is characterized by the usual fever, malaise and abd cramping and ___ diarrhea, and the late phase which is aka as ___

Answer 28

Shigella presents in two phases, the early phase (within 24hrs) which is characterized by the usual fever, malaise and abd cramping and watery diarrhea, and the late phase (2 - 7 days) which is aka as dysentery (bloody and mucousy diarrhea + fecal leukocytes on microscopy)

Question 29

2 of the main complications of Shigella are ___ and ___ (type of reactive arthritis in kids)

Answer 29

Severe colitis >> hemorrhage

Reiter’s syndrome (arthritis, urethritis, conjunctivitis)

Question 30

Describe the pathogenesis of Shigella

Answer 30

Shigella gets taken up by the M cells of the gut and quickly enters and leaves the macrophages closely ass’d with the M cells (the bug hijacks the cell’s actin cytoskeleton and propels itself out of the macrophage – lysing it – and infecting other cells)

This results in induction of a strong inflammatory response

Hallmark of shigellosis is presence of neutrophilic infiltration (while the WBC are extravasating, the nasty little bug can actually seep thru and get into the gut via paracellular transport – remember from functional systems?)

Question 31

The hallmark of Shigellosis is ___

Invasion of shigella is mediated by __

Answer 31

presence of neutrophilic infiltration

Type 3 secretion system

Question 32

What would you do to treat/manage Shigella infection?

Answer 32

Maintain hydration

Rx: azithromycin/ciprofloxacin (macrolide or FQ)

(anti-motility agents are NOT indicated)

Question 33

Shigella dysenteriae is especially virulent due to the __ that cleaves the 28S ribosomla rRNA

A key complication that can arise from S dysenteriae infection is ___

Answer 33

Shigella dysenteriae is especially virulent due to the Shiga toxin that cleaves the 28S ribosomal rRNA

**note that Sketchy says 60S**

A key complication that can arise from S dysenteriae infection is hemolytic uremia syndrome (remember the plates - thrombocytopenia; the bursting red balloons - RBC lysis >> anemia; the whip shaped like a glomerulus - renal failure)

Question 34

A traveler returning from SE Asia presents with fever, chills, and generally very ill feeling for the past 3 days. Minimal diarrhea is reported. What is your course of action?

A.Ask about their vaccination history

B.Perform stool culture

C.Treat with antibiotics after checking susceptibility

D.Maintain hydration

E.All of the above

Answer 34

E. (Thinking that this is typhoid)