Week 4 - Gram Negative Bacilli Flashcards
Pseudomonas aeroginosa can form a ___________ in cystic fibrosis patients
biofilm
E. coli 0157:H7 can be detected using what type of agar?
Chromogenic agar
What Gram negative bacilli has a carrier state where people are infected but not sick? In which part of the body does the bacteria stay and continuously produce toxins?
Salmonella Typhi
Gallbladder
What condition of the intestine is essential for the growth of Salmonella?
Intestinal inflammation
What gram negative bacilli has an ID50 of 10?
Shigella has an infectious dose of 10 microorganisms
What gram negative bacilli causes rice water stools and what is the disease called?
Vibrio cholerae- Cholera
What two gram negative bacilli are medically important for individuals with Cystic Fibrosis?
Pseudomonas aeroginosa
Burkholderia spp.
Pneumonia that is likely to be untreatable with antibiotics might be caused by a gram negative bacilli called?
Legionella
Would E. coli infections be treated with penicillin? Why or why not?
No - they are a gram negative bacteria and since penicillins target the peptidoglycan production in gram POSITIVE bacteria, this antibiotic would not be very effective.
Why is urethritis (infection of the urethra) frequently preliminary to further infections of the urinary tract?
Bacteria can ascend the urinary tract and cause infections further up, for example the bladder, ureters and kidneys
Why is E. coli the most common cause of cystitis, especially in females?
The female anatomy means the urethra is closer to the anus where E. coli is commensal, than males.
What are 4 examples of pathogenic strains of E. coli discovered during this unit?
ETEC - Enterotoxigenic E. coli.
EIEC - Enteroinvasive E. coli.
EPEC - Enteropathogenic E. coli.
EHEC - Enterohemorrhagic E. coli (aka 0157:H7)
If you adequately cook food contaminated with ETEC, would you be able to safely eat it?
No - the toxin that ETEC produces is heat stable.
During an infection of EIEC, where do these bacteria multiply?
Inside the intestinal epithelial cells.
What does EPEC do to the intestinal epithelial cells?
Destroys the brush border microvilli.
What is 0157:H7 and what toxin does it produce?
EHEC - Enterohemorrhagic E. coli - releases shiga-like toxin (as in Shigella)
Which food is most likely associated with Salmonella spp?
Chicken / eggs
What toxins are produced by Salmonella that induce illness?
- Enterotoxin - affects the enteric system
- Cytotoxin - affects cells
In which organ of the body does Salmonella Typhi exist in carriers?
The gallbladder
What does Salmonella do to the M cells of the intestinal tract?
Causes membrane ruffle, enters the cell and multiplies inside. Occasionally can go on to enter lymphatic system and bloodstream.
What does Salmonella do to cause an inflamed gut and why?
Uses a Type III secretion system
What disease does Shigella cause and what causes this?
Dysentery - through Shiga exotoxins.
How does Shigella avoid immune defences after multiplying inside the M cell of intestinal tract?
Invades neighbouring cells.
What does Shigella infection do to the intestinal epithelial cells?
Abscess forms
What colour are Salmonella colonies on XLD agar?
What colour are Shigella colonies on XLD agar?
Salmonella - black colonies
Shigella - clear red colonies
What are the symptoms of cholera infection and what happens because of this symptoms?
Massive fluid loss
Rice water stools
Leads to hypovolemia and can cause shock and death.
What disease can Proteus mirabilis cause?
Urinary Tract Infections
What does Klebsiella spp look like on MAC and why?
Goopy slimy pink colonies. Pink because they ferment lactose and slimy because they are motile - they swarm the plate.
What would the benefit be of bacteria having exotoxins?
To kill off competing bacteria - make a niche.
In an AB exotoxin, which part binds and which part is responsible for the toxic effect?
A - toxogenic
B - binding subunit.
What is LPS?
Lipopolysaccharide - an endotoxin in Gram negative cell walls. Lipid
What temperature does Campylobacter jejuni best grow at?
43 deg celcius
What enzyme does Helicobacter pylori produce to be able to live in the stomach acid?
Urease - hydrolyses ammonia and provides a local alkaline environment to survive in an acidic environment. A urease breath test can indicate a possible H. pylori infection.
