Salmonella + Shigella Flashcards
Salmonella classification (morphology; motility, enzymes, capsule etc)
Salmonella spp are
GN flagellated rod, encapsulated (esp S. typhi has Vi capsule)
Lactose neg + H2S +ve (black colonies)
Which spp of Salmonella are found in cold blooded animals and in the environment?
The non-Sub group I Salmonella enterica spp
Salmonella ___ are the ones that cause GI symptoms in humans and infect people thru contaminated food
Salmonella enterica (Enterica: typhoidal vs non typhoiddal)
Non typhoidal Salmonella typically causes ___ (GI issue) and mainly infects humans through contaminated __
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**
Because Salmonella enteritidis causes a self limited diarrhea, Rx for this infection is ___
Because Salmonella enteritidis causes a self limited diarrhea, Rx for this infection is NO antibiotics
The most common causes of bacterial diarrhea and infection are __ and ___
Salmonella and Campylobacter
Salmonella ___ and ___ cause a systemic syndrome called “typhoid fever”
S typhi and S paratyphi
Typhoid fever is a systemic infection affecting the ___
Typhoid fever is a systemic infection affecting the RES (remember that it affects M-phages which are part of the RES)
T/F: Diarrhea is a prominent feature of typhoid fever
For class: not really
For step: causes pea soup diarrhea
S typhi is found only in humans (specifically in the ___ of asymptomatic carriers) and is contracted via ___
S typhi is found only in humans (specifically in the gallbladder of asymptomatic carriers) and is contracted via ingestion of contaminated food or water
The incubation period of S typhi infection is ___ (days) and presentation includes __
The incubation period of S typhi infection is 5-21 (days) and presentation includes non specific symptoms (headache, malaise, sore throat etc)
S typhi has characteristic ___ on pts abdomen ( hepatosplenomegaly, abdominal tenderness are also common)
S typhi has characteristic red spots on pts abdomen ( hepatosplenomegaly, abdominal tenderness are also common)
Most common cause of death from S typhi infection is __
Which antibiotics are indicated for S typhi infection?
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)
T/F: Salmonella typhi has a vaccine
True. there’s two in fact
Describe the 2 vaccines for S typhi
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)**
What is the presentation of infection with S paratyphi?
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)
Salmonella are ___ (facultative/obligate) intracellular
What is the mechanism of infection?
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**
Salmonella typhi invasion is through the Type III secretion system in two parts:
First is for ___
2nd is for ___
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)
The most important virulence factor in S typhi is the ___
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
The main difference in the host response to S typhi vs NTS infection is ___
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**
Inflammation induced by Salmonella confers a growth advantage over host commensals due to release of __ which allows the bug to scavenge for Fe unregulated
**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
The Salmonella Type 3 secretion systems SP1 and SP2 are for what?
SPI 1 – TTSS required for bacterial uptake
SPI 2 –TTSS required for intracellular survival and immune evasion
Shigella morphology/enzymes/gram stain etc
Shigella: gram negative facultative intracellular rod
Lactose and H2S negative; green colonieson Hektoen agar
The 4 most clinically significant Shigella spp are:
S sonnei
S flexneri
S dysenteriae
S boydii
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
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
Most foodborne outbreaks in the US are ass’d with which Shigella spp?
The transmission of shigella is ___
S flexneri
Fecal - oral (can be sexually transmitted for this reason; resistant strains in men who have sex with men)
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
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
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 ___
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)
2 of the main complications of Shigella are ___ and ___ (type of reactive arthritis in kids)
Severe colitis >> hemorrhage
Reiter’s syndrome (arthritis, urethritis, conjunctivitis)
Describe the pathogenesis of Shigella
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?)
The hallmark of Shigellosis is ___
Invasion of shigella is mediated by __
presence of neutrophilic infiltration
Type 3 secretion system
What would you do to treat/manage Shigella infection?
Maintain hydration
Rx: azithromycin/ciprofloxacin (macrolide or FQ)
(anti-motility agents are NOT indicated)
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 ___
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)
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
E. (Thinking that this is typhoid)
