Exam2Lec3EntericBacteria Flashcards
Enteric bacteria general details:
Endotoxin (LPS) (more or less)
Motile or non-motile
Facultative anaerobic
Simple nutritional requirements
—Ferment glucose
—Reduce nitrates to nitrites
—Oxidase negative
What is the reservoirs of enteric bacteria
Ubiquitous
Humans
–Normal flora (endogenous)
–Diseases
–Carriers
Animals
Water
Soil
Vegetation
Exogenous portal of entry usually oral
What is used as a public health indicator of fecal contamination of water
Enterobacteriaceae–> e.coli and Coliforms that are only in the bowel
What is the morphology of coliform
gram negative rods
Lactose positive fermentation
What is the single cause of morbidity and mortality in the world
Diarrheal disease
In what population of groups what is the greatest of morbidity and mortality?
small children
Over ___ of children in many parts of ____ ____ die before the age of __, the majority with diarrhea associated illness.
10%, Latin America, 5
What are the two types of gastroenteritis?
Secretory (watery) diarrhea
Inflammatory diarrhea
What is Inflammatory diarrhea
Presence of white blood cells
-Neutrophils
-Mononuclear
Presence or absence of red blood cells
Fever
What bacteria can cause inflammatory diarrhea?
Explain given
Shigella
What is Secretory (watery) diarrhea
Absence of white blood cells
Absence of red blood cells
Watery, large volume
Nausea, vomiting
Afebrile
What bacteria can cause Secretory (watery) diarrhea? Example given
cholera
What is the morphology and the metabolism of E.coli
Gram (-) bacilli
facultative anaerobe
E.coli is classified into ____
serogroups by O, H and K antigen
What does the serogroup O stand for
LPS
What does the serogroup H stand for
flagella
What does the serogroup K stand for
capsule
What is an example of serogroup (EHEC)?
O157:H7
Overview of E.coli pathotypes
Enterotoxigenic (ETEC) – heat stable (ST) or labile (LT) toxin stimulates hypersecretion of fluids in small intestine
Enteropathogenic (EPEC) – adherence and destruction (A/E lesions) of cells, decreased fluid absorption
Enterohemorrhagic (EHEC) – similar to EPEC but with shigatoxin, may progress to HUS
Others (EIEC, EAEC, UPEC)
Most common of e.coli pathotype
EAEC (dont care about)
EHEC ⭐️
Where is ETEC found?
Endemic in developing countries
causes about 1/5th of all diarrheal illness in humans (largely pediatric)
also individuals traveling from developed nations (i.e. traveler’s diarrhea)
ETEC can also be considered ?
traveler’s diarrhea
What is the transmission of ETEC?
fecal oral transmission
What is the symptoms of ETEC
Rapid onset of watery diarrhea from mild to cholera-like
nausea
vomiting
no RBCs or WBCs
What is the Virulence factors of ETEC?
heat-stabile (ST)
heat-labile (LT) toxins
What does ST toxin in ETEC cause
increase cGMP
What does LT toxin in ETEC cause
Increase cAMP
The increase of cGMP and cAMP causes what?
Increase cl- transport out of the cell and water goes with it
How do we treat ETEC?
Symptoms usually resolve without therapy
Where do we find EPEC
Infant diarrhea in underdeveloped countries
What does EPEC do?
EPEC adhere to epithelial cells lining small intestine (A/E lesions)
What are the symptoms of EPEC?
Malabsorption
watery diarrhea
usually without RBCs or WBCs
What does EPEC have to cause disease?
Type III (contact dependent) secretion system
Where is the Type III (contact dependent) secretion system
Location
-Channel spanning both membranes of Gram negative bacteria
-Two components fuse with
eukaryotic cell membrane to form
injection pore (needle-like)
What is the attachment that EPEC can adhere to the host cell called
BfpA
What is the effector that EPEC injects into cell?
TIR
What does TIR act as for EPEC
It acts as a receptor for Intimin (on the outside of EPEC)
what does TIR stand for ?
Translocated intimin receptor
Where is EHEC found
Predominantly in developed nations
What is the reservoir of EHEC
Cattle
Extra fun details of EHEC
Sporadic, usually outbreaks with common source
Forms A/E lesions like EPEC, usually not invasive
What is the usually the source of EHEC
Undercooked beef
What is the most common serotype of EHEC
O157:H7
What are the symptoms of EHEC
Watery diarrhea that may progress to bloody
cramps
fever may be absent
What is the Pathogenesis of EHEC
Forms A/E lesions like EPEC
Shiga toxin released
Inhibits host cell protein synthesis
Cell death
Possible dissemination and damage to kidney (HUS)
What is the Virulence factor of EHEC
Shiga-like toxin
How does the progression of EHEC occur?
-3 Days AFTER ingestion
1. Diarrhea
2. Abdominal Pain
3.Fever
4. Vomiting
-Days 0-6
1. Hemorrhagic colitis (bloody diarrhea)
-Day 7
1. 15% of cases=HUS
2. 85% of cases=Resolution
How is e.coli diagnosis?
Culture on selective and differential medium, MacConkey agar
E.coli are lactose fermenters and would make the agar turn pink
If EHEC suspected then how do we diagnosis ?
sorbitol-MacConkey (SMAC) agar
O157 are sorbitol-
most other E. coli are +
What is the treatment of e.coli
usually supportive, fluid and electrolyte replacement
What is the morphology and the metabolism of V. cholerae
Gram neg curved bacilli, polar flagellum
facultatively anaerobic
Where is V.cholerae found?
Marine environments
infected humans may serve as a reservoir (asymptomatic infection if infecting dose was low)
drinking water supply is main source of transmission
—-fetal oral
fresh seafood
To cause infection of V.cholerae, how much bacteria do we need?
over a million
What are the symptoms of V.cholerae ⭐️
Acute onset of watery stools
rice water stools
Low Fever
Little Pain
What is the VF of V.cholerae? how does it work
Cholera Toxin
Increase cAMP so increase Cl- transport out of cell
Expression of cholera toxin is co-regulated with expression of pilus
what it the fatality rate of cholera if untreated?
60%
Extra fun facts of cholera
Convalescent carrier (asymptomatic or mild) possible
Cases in US Gulf coast states (shellfish)
Epidemic spread in many parts of world
El Tor (O1) survives longer in environment, may cause milder disease
O139 Bengal associated with more recent epidemics
which version of V. cholerae survives longer in environment and cause milder disease
El Tor (O1)
El Tor (O1) in V. cholerae
survives longer in environment and cause milder disease
which version of V. cholerae is associated with more recent epidemics
O139 Bengal
How is V. cholerae diagnosis?
Grows on blood agar
MacConkey
serotyping
Prevention of V. cholerae
Oral vaccine testing by WHO, recommended for outbreak response
What is the treatment of V. cholerae?
Supportive therapy (mainstay):
-IV or oral hydration with electrolyte replacement with small amounts of glucose
Antibiotics (severely ill, moderate to severe dehydration, hospitalized):
-Adults: doxycycline
-Pregnant women/children: erythromycin, azithromycin ⭐️
How is salmonella divided?
S. Typhi and and S. non typhi
What is the reservoir of S. typhi ?
Humans
What is the reservoir of S. non typhi ?
Ubiquitous
Humans, animals, feed, eggs, dairy and water
what is lab results of salmonella species
lactose neg
Motile via flagella
What type of pathogen is Salmonella subsp. typhi
obligate pathogen
what can Salmonella subsp. typhi cause
enteric (typhoid) fever
Septicemia
What is the infectious dose of Salmonella subsp. typhi
~1000 (less than non-typhi)
How is Salmonella subsp. typhi carried
Macrophages ingest & carry organisms via lymph and blood
How is Salmonella non-typhi subsp transmitted
food ingestion
fecal oral
What does Salmonella non-typhi subsp cause
non-blood diarrhea
What is the infectious dose of Salmonella non-typhi subsp
10^6
What it the VF and what does Salmonella non-typhi subsp do
Virulence
—Invasin – attachment & penetration
—Acid tolerance – protects from stomach & phagosome acids
Invade cells lining the lumen
How do we diagnosis salmonella spp
differential growth on XLD agar followed by serotyping
REMEMBER: salmonella is lactose neg
What is the treatment for salmonella
S.typhi: requires treatment
—–fluoroquinolones, cephalosporin, antibiotic susceptibility testing required
S. non typhi: NO ANTIBIOTICS
What is the prevention of Salmonella
S.typhi vaccine: live attenuated bacterium: replicates for a short period of time
What does shigella sp do
Invades colonic mucosa
What is the timeline for shigella sp
1 to 3 day incubation period
Generally subsides in 10 days
What are the VFs in shigella sp
Invasin
-acts on GI cells to phagocytose
-Lyse phagocytic vacuole
-Directs host cell actin (contiguous spread)
Shiga toxin
- inhibits protein synthesis
-Toxin similar to EHEC toxin
-Hemolytic uremic syndrome (HUS)
How is shigella transmitted ?
human disease only (children)
Fecal oral route
What is the infectious dose of shigella
<200 bacteria needed to produce infection (low)
What does shigellosis (bacillary dysentery) cause (symptoms)
cramps
fever
diarrhea
tenesmus–> feeling like you need to poop but do not need to
frequent bloody
small stools
S. dysenteriae can have a ___ mortality rate in young children
high
Diagnosis of Shigellosis
Differential growth on XLD agar
Treatment of shigellosis
Replacement of fluids & electrolytes
Generally self-limiting
Antibiotics indicated in severe cases and may shorten disease
—-Empiric treatment with ciprofloxacin but antibiotic ——-sensitivity tests should be done due to multiple drug resistant strains
Antidiarrheals contraindicated, prolong disease
Antidirrheals are _____ and ____ ____ with shigella
contraindicated, prolong disease
What is the morphology of Campylobacter jejuni
Gram neg bacilli, very thin, curved
Microaerophilic
Polar flagellum or flagella
What is the reservoir for Campylobacter jejuni
animal
what is the transmission of Campylobacter jejuni
Transmission via contaminated food, water
direct contact with carrier animals
What is the infectious dose of Campylobacter jejuni
~1000
Campylobacter jejuni is the ____ common cause of bacterial gastroenteritis in the US
MOST
What is the VF of Campylobacter jejuni
Adhesins
Cytotoxin
Enterotoxin
Organisms multiply in the small intestine, invade the epithelium and produce inflammation (pathogen in humans)
What are the symptoms of Campylobacter jejuni
abdominal cramps
fever
diarrhea with blood and leucocytes (neutrophil)
Enteritis
Bacteremia
What causes Guillain barre syndrome
Campylobacter jejuni
What is Guillain barre syndrome
(neuromuscular paralysis), antibodies to bacterium cross-react with antigens on neural tissue cells
What is the diagnosis of Campylobacter jejuni
Selective growth on selective Campy agar to suppress growth of microflora
5-10% oxygen
42C
2-4 days incubation
Gull wing shaped cells ⭐️
What is the treatment of Campylobacter jejuni
Supportive therapy
—-Fluid and electrolyte replacement
Antibiotic therapy only in severe cases:
—-Erythromycin/azithromycin
—-Ciprofloxacin
Antibiotic susceptibility testing helpful
A 22 year old medical student took a weekend trip to Costa Rica to celebrate the end of finals for GI. The day she returns, she develops watery diarrhea, five to six times a day, with nausea, occasional vomiting, and crampy abdominal pain.
There are no leukocytes on stool exam.
a.Shigella species
b.Campylobacter jejuni
c.EHEC
d. EPEC
e.ETEC
E
A family comes to your office. The father and a six-year old girl are having bloody diarrhea which started last night. The day before they ate out at a fast-food hamburger restaurant.
The little girl is dehydrated, pale and somewhat lethargic. Blood tests show that she is developing renal failure.
a.Salmonella species
b.Vibrio cholerae
c. EHEC
d. EPEC
e.ETEC
c.
Your patient is a 30-year-old woman with nonbloody diarrhea
for the past 14 hours. Which one of the following organisms is
LEAST likely to cause this illness?
(A) Clostridium difficile
(B) Streptococcus pyogenes
(C) Shigella dysenteriae
(D) Salmonella enteritidis
b
Which one of the following bacteria has the LOWEST 50%
infectious dose (ID50)?
(A) Shigella sonnei
(B) Vibrio cholerae
(C) Salmonella typhi
(D) Campylobacter jejuni
a
For which one of the following enteric illnesses is a chronic carrier state MOST likely to develop?
(A) Campylobacter enterocolitis
(B) Shigella enterocolitis
(C) Cholera
(D) Typhoid fever
d
Two hours after a delicious Thanksgiving dinner of barley soup, roast turkey, stuffing, sweet potato, green beans, cranberry sauce, and pumpkin pie topped with whipped cream, the Smith family of four experience vomiting and diarrhea. Which one of the following organisms is MOST likely to cause these symptoms?
(A) Shigella flexneri
(B) Campylobacter jejuni
(C) Staphylococcus aureus
(D) Salmonella enteritidis
c
The pathogenesis of which one of the following organisms is
MOST likely to involve invasion of the intestinal mucosa?
(A) Vibrio cholerae
(B) Shigella sonnei
(C) Enterotoxigenic Escherichia coli
(D) Clostridium botulinum
b
Which one of the following organisms that infects the gastrointestinal tract is the MOST frequent cause of bacteremia?
(A) Shigella flexneri
(B) Campylobacter jejuni
(C) Vibrio cholerae
(D) Salmonella typhi
d
CASE: Your patient is a 50-year-old woman who returned yesterday from a vacation in Peru, where there is an epidemic of cholera. She now
has multiple episodes of diarrhea. Of the following, which one is MOST compatible with cholera?
(A) Watery diarrhea without blood, no polys in the stool, and
growth of curved gram-negative rods in the blood culture
(B) Watery diarrhea without blood, no polys in the stool, and no organisms in the blood culture
(C) Bloody diarrhea, polys in the stool, and growth of curved
gram-negative rods in the blood culture
(D) Bloody diarrhea, polys in the stool, and no organisms in the
blood culture
b
Your patient is a 5-year-old girl with bloody diarrhea and no
vomiting. There is no history of travel outside of San Francisco. Stool culture grows both lactose-positive and lactose-negative colonies on EMB agar. Of the following organisms, which one is MOST likely to be the
cause?
(A) Shigella sonnei
(B) Salmonella typhi
(C) Campylobacter jejuni
(D) Helicobacter pylori
a
CASE: Your patient is a 40-year-old woman with a severe attack of diarrhea that began on the airplane while she was returning from a vacation in the Middle East. She had had multiple episodes of watery, nonbloody diarrhea and little vomiting. She is afebrile. A stool culture
reveals only lactose-fermenting colonies on EMB agar. Of the following, which one is the MOST likely cause?
(A) Shigella sonnei
(B) Helicobacter pylori
(C) Escherichia coli
(D) Pseudomonas aeruginosa
c
CASE: Your patient is a 30-year-old woman who was part of a tour group visiting a Central American country. The day before leaving, several members of the group developed fever, abdominal cramps, and bloody diarrhea. Of the following, which one is the LEAST likely organism to cause this infection?
(A) Shigella dysenteriae
(B) Salmonella enteritidis
(C) Vibrio cholerae
(D) Campylobacter jejuni
c
CASE: Your patient is a 30-year-old woman who was part of a tour group visiting a Central American country. The day before leaving, several members of the group developed fever, abdominal cramps, and bloody diarrhea. Of the following, which one is the LEAST likely organism to cause this infection
UPDATE: A stool culture reveals no lactose-negative colonies on the EMB agar. Which one of the following is the MOST likely organism to cause this infection?
(A) Shigella dysenteriae
(B) Salmonella enteritidis
(C) Vibrio cholerae
(D) Campylobacter jejuni
d
