Vibrios Flashcards
State the family that vibrios belong to
vibrionaceae
state the general characteristics of
vibrios; this includes: (gram stain, shape, motility,capsule,sporation,aerobicity and main antigeris)
Gram negative
comma or curved shape
Highly motile (one polar flagellum)
no spores
no capsule
facultative anaerobes
Has antigen O and H
what media does vibrios grow in?
MacConkey’s agar
Thiosulfate citrate Bile salts Sucrose (TCBS)
Halophilic and halophobic vibrios?
V.cholera- not halophilic
Others-halophilic
State pathogenic strains of vibrios.
V. cholerae
V. parahaemolyticus
V. vulnificus
Describe epidemiology of vibrios. (reservoir and environment boosters i.e. sailinity and temp)
Reservoir: Chitinous shellfish and humans(asymptomatic carriers)
Survives in saline and warm water (10-30 degrees)
Main mode of transmission of cholera.
Sewage contaminated water.
Which serotypes cause pathology very easily?
O1
O139
How is V.cholera transmitted? (means of contamination etc)
Inadequate sewage treatment
Lack of water treatment
Improperly cooked shellfis
Wash fruits/vegetables with untreated water
Describe pathogenesis of V.cholera.
• Bacteria adheres to the epithelia cells of gastric intestinal mucosa via pilli
• survive the acidic conditions of the human stomach
• Production of proteases (mucinase) which dissolves protective glycoprotein coating cells
• High motility
• Ability to produce an enterotoxin-cholera toxin (CT)
Describe mode of action of cholera toxin.
Inactivates GTPase function of GPCR in intestinal cells.
- Cholera toxin modifies Gs protein using its A subunit – It attaches a chemical group (ADP-ribose) to the Gsα subunit of the G-protein.
- G-protein gets stuck “on” – This prevents the G-protein from turning itself off, so it keeps activating adenylate cyclase.
- Too much cAMP is produced – Adenylate cyclase makes too much cAMP, which sends strong signals inside the cells
- Water floods into the intestine – cAMP forces Cl⁻ (chloride) channels to stay open, pulling Na⁺ and water into the intestine, causing severe diarrhea.
Symtpoms of V.cholera?
Abrupt onset of vomotting and life-threatening watery diarrhoea.
Rice water stool; odourless,colourless and has mucus
Risk groups of V.cholera?
Children
Elderly
Blood group: O then B,A and AB (in that order)
Visible symptoms of V.cholera
Decreased skin turgor
Sunken eyes and cheeks
Almost no urine production
Dry mucous membranes
Appearance of vibrio on TCBS?
V.cholera- green colonies
V.parahemolyticus- yellow colonies
Treatment (not antibiotics)?
IV rehydration
Oral rehydration
Antibiotics against V.cholera?
Tetracycline
Doxycycline
