Travel Associated Illnesses Flashcards
Describe the structure of Vibrios
Gram -
Comma Shaped
Polar Flagellum
How does the DNA of vibrios appear?
2 circular chromosomes
Vibrio pH happy place?
Highly alkali tolerent, but acid sensitive
How do vibrio feel about salinity?
Halotolerant, some halophilic
How are Vibrio cholerae classified?
Capsule, Biotypes, Serotypes
Disease state Vibrio cholerae has what capsule type?
O1 (no capsule)
Disease state Vibrio cholerae has what biotypes?
Classical
El Tor
What serotypes are associated with both biotypes? With One?
Both – Ogawa, Inaba
Only El Tor – O139
What medication is prone to promote Vibrio cholerae growth?
Antacid
Normally 10^6 needed, with AA only 10^3
Vibrio cholerae presents in what part of the body?
Small Intestine
Clinical presentation of Vibrio cholerae infection?
1-4 day incubation
Nausea, Vomiting, 1-2 loose stools
Acute, Profuse diarrhea – “Rice Water Stool”
No Pain, Fever
Describe the “Rice Water Stools” seen in Vibrio cholerae infection.
Contains lots of mucus
10^8 vibrios/mL
No Blood
How does Vibrio cholerae tend to become a fatal disease?
Dehydration and Electrolyte loss
Vibrio cholerae is distributed where?
Around the world in water supplies via copepods
Hosts of Vibrio cholerae?
Only humans
What do we know about chronic Vibrio cholerae?
Very rare
“Cholera Delores”
Explain the pathogenesis of Vibrio cholerae.
Fibriae bind gut epithelium
AB5 Toxin expressed (Toxin/Pilus regulated by riboswitch)
B binds to receptor ganglioside G-m1 of epithelial cells
A-A’s SS bond is reduced
A1 uses NAS to ADP-Ribosylate a Gs Protein
How does ADP-ribosylating a Gs protein influence host function?
Activates adenylyl cyclase
Increased cAMP causes ion secretion into gut
Water follows ions
Relationship between pertussis and cholera?
Similar mechanism
Per. blocks the inhibitor
Cholera locks in active state
Explain how the Vibrio cholerae riboswitch works
The switch weakly blocks the genes for toxin and pilus at low temperatures (ocean). When moved to higher temperatures (stomach), unstable base pairings fall apart, allowing transcription of the toxin and pilus
Most important component of treatment for Vibrio cholerae?
Rehydration and Electrolyte Replacement
An Oral Rehydration Salts (ORS) formula contains…
NaCl (3.5g/L)
KCl (1.5g/L)
NaHCO3 (2.5g/L)
Glucose (20g/L)
What medicinal treatment might be used for Vibrio cholerae?
Doxycycline can limit shedding, but can’t stop the diarrhea
Describe Vibrio cholerae vaccines.
not very effective – about 6 months
Use heat-killed O1 Classical Strain
Few doses available, used in outbreaks
Clinical presentation of Vibrio parahemolyticus
- 12-24 hour incubation
- Nausea, vomiting, watery-bloody diarrhea, maybe gastroenteritis
Where can Vibrio parahemolyticus be found? How is it typically spread?
Worldwide in Oceans
Raw/Undercooked Seafood
Pathogenesis of Vibrio parahemolyticus?
Biofilms
Type 3 and 6 Secretion Systems
Hemolytic/Cytotoxic Enterotoxin
How is Vibrio parahemolyticus treated?
Rehydration and electrolyte replacement
Doxycycline if necessary
Typical origin of Vibrio vulnificus infection?
Infected would from handling contaminated seafood
Bacteremia from eating raw oysters
Symptoms of Vibrio vulnificus infection?
Infected wounds from handling
Within hours, cellulitis and necrosis
Eventual liver damage
50% Fatal
What is cellulitis?
Inflammation of subcutaneous connective tissue
Vibrio vulnificus is always associated with contaminated ________ or _______.
Seawater or Seafood
Vibrio vulnificus has foci in what three US states?
TX
LA
AL
Describe the pathogenesis of Vibrio vulnificus
Antiphagocytotic capsule prevents control
Necrotizing cytotoxin release
What do you do if you suspect a patient has Vibrio vulnificus infection?
Doxycycline immediately
Takes 18 hours to get culture – too late.
Describe the structure of campylobacter
G-
Curved, Helical, or Gul-Winged
Polar Flagella
What oxygen tolerance is campylobacter?
Microaerophile
How can you differentiate different campylobacter species?
Growth temperature
Temperature campylobacter jejuni can grow in?
42C, but not 25C
Clinical presentation of Campylobacter jejuni infection?
Abdominal Pain, Cramps, Fever
Very Bloody Diarrhea (Sometimes Blood Red)
May invade bloodstream and cause enteric fever in IC
Campylobacter jejuni is a disease of what part of the body?
Large Intestine
Secondary concern that may arise 1-4 weeks after Campylobacter jejuni infection?
Guillain-Barre syndrome
What is Guillain-Barre Syndrome?
A demyelinating neural disease
Causes Progressive flaccid paralysis
Causes by molecular mimicry/autoantibodies to G-M1
Campylobacter jejuni is primarily spread through what two methods?
Fecal-Oral Route
Contaminated Poultry and Milk
When do people tend to get Campylobacter jejuni in the US?
Summer
Who is most prone to suffer from Campylobacter jejuni ?
Infants and Young Adults
Top two bacterial causes of gastroenteritis?
Salmonella
Campylobacter jejuni
Campylobacter jejuni pathogenesis?
Inflammatory enterotoxin
Bacteremia indicates invasive potential
How is Campylobacter jejuni treated?
Rehydration therapy
Tetracycline, Quinolones, Clarithromycin if systemic infections
What temperature does Campylobacter fetus grow at?
Grows at 25C, but not at 42C
Clinical presentation of Campylobacter fetus?
Systemic infections, septicemia
How is Campylobacter fetus typically acquired?
Eating contaminated/Undercooked Beef
Who is most susceptible to Campylobacter fetus?
Elderly, Ill, IC
Pathogenesis of Campylobacter fetus?
S-layer protein inhibits complement fixation –> Less Phagocytosis
How is Campylobacter fetus controlled?
Tetracyclines, Macrolides, and Quinolones
Describe the Helicobacter pylori organizm structure.
Gram-
Spirillum (Lazy S)
Oxygen sensitivity of Helicobacter pylori?
Microaerophile
Helicobacter pylori produces huge amounts of ______
Urease
Detectable within minutes-hours
Is Helicobacter pylori infection typically acute or chronic?
Chronic
Helicobacter pylori colonizes where? How?
Gastric Mucosa esp. antrum
via Lewis Blood Group Adhesin
Helicobacter pylori is associates with what two pathologies?
Gastric/Duodenal Ulcers
Gastric Adenocarcinoma
How is Helicobacter pylori detected?
Serological Test
Gram Stain/Culture of Gastric Biopsy
Urea Breath Test
Which test for Helicobacter pylori is most effective?
Urea Breath Test
How does a Urea Breath Test work?
C14 Urea is fed, detection of 14-CO2 in breath indicates urease activity of the stomach
___% of people are Helicobacter pylori carriers
Approx. 50%
Helicobacter pylori infection is most commonly seen in which patients?
Middle-aged and older
What may mask Helicobacter pylori infection?
Long-term proton pump inhibitors seen in GERD patients
Helicobacter pylori is heavily correlated with a particular _____ allele?
TLR1
Describe the pathogenesis of Helicobacter pylori.
- Bind to base of gastric mucosal cells (pH=7.4)
- Bind Lewis Antigen
- Huge amounts of urease buffer pH
- Produce VacA (Vacuolating Toxin)
Helicobacter pylori is especially prevalent in people with Type __ Blood.
O
Lewis Antigen = O Blood group Antigen
How does urease activity buffer pH in the stomach?
Forms NH3 from Urea
Effects of vacuolating toxin (VacA)
- Activated by stomach acid
- binds to lipid rafts of gastric epithelium
- Inserts into cell as selective anion channel
- Extensive vacuolation of epithelial cells and urea release while inhibiting immune response
Ulcer associated strains of Helicobacter pylori also produce what toxin…
Cytotoxin (CagA)
CagA is secreted by…
It has what primary effect? What potential secondary effect?
Type 4 secretion system
Induced apoptosis of host cells
It may be an oncoprotein
Production of VacA and CagA virulence factors of Helicobacter pylori is enhanced by ______.
Salt
How are Helicobacter pylori ulcers treated?
Bismuth subsalicylate
How is Helicobacter pylori infection treated?
Tetracycline (or)
Macrolide+Metronidazole
How is Helicobacter pylori acid treated?
PPI
Why is bicarbonate alone an ineffective treatment for stomach ulcers?
It allos Helicobacter pylori to spread
