Microbiology Flashcards
What is considered mild diarrhoea?
3 or few stools per day ( without abdominal or systemic symptoms)
What is considered moderate or severe diarrhoea?
4 or more stools per day associated with [abdominal symptoms (cramps, nausea, vomiting, tenesmus) systemic symptom (fever, malaise, dehydration)].
What is Dysentery?
Passage of frequent , small- volume stools accompanied by blood, mucus, abdominal pain (cramping) and tenesmus. (ineffectual and painful straining at stool.
What are the most common sources of Dysentry?
- Shigella spp.
- Campylobacter spp
- Enteroinvasive Escherichia Coli
- Salmonella enteritidis (?)
- Yersinia enterocolitica (?)
- Antibiotic –associated diarrhoea Clostridium difficile
What type of bacteria is Shigella?
Gram - negative bacilli
What type of Shigella is seen primarily in underdeveloped countries?
Shigella flexneri
“They can’t flex because they’re underdeveloped “
What type of Shigella is the most common in the industrial world ?
Shigella sonnei
Shigella outbreaks normally occur in?
- Homosexuals men
- Under conditions of crowding
- Where personal hygiene is poor, such as in jails, institutions for children, daycare centres, mental hospitals and crowded refugee camps.
What is the infectious dose for Shigella?
10-100 or 100-200 Low infectious dose
What type of cells does the Shigella bacteria adhere and invade?
M cells in Peyer’s patches.
From what type of bacteria is Shiga toxin produced in?
Shigella dyenteriae type 1
What is the Shiga Toxin?
This toxin is a subunit protein composed of one A subunit and five B subunits with binding specificity for a specific microvillus membrane glycolipid receptor
Fill in the blanks. “In relation to the Shiga toxin, The glycolipid receptor for the B subunit are located on __________.”
The villus cells
True or False? The glycolipid receptor for the B subunit are located on the villus cells and NOT the crypt cells, thereby impairing sodium adsorption without affecting chloride secretion and leading to net luminal fluid accumulation.
TRUE!!
What does the A unit for the Shigella Toxin cleaves ?
The A subunit enzymatically cleaves the 28S ribosomal RNA of the 60S ribosomal subunit in eukaryotic cells with resultant inhibition of protein synthesis .
Haemolytic - uremic syndrome , Toxic Megacolon , Disseminated intravascular coagulation (DIC) & Sepsis is associated with which type of Shigella?
Shigella Dysenteriae Type 1
What is Reiter’s syndrome?
It is a post infectious arthropathy-the triad of nongonococcal urethritis, conjunctivitis and arthritis, frequently with mucocutaneous lesions.
What is the culture used for the diagnosis of Shigella?
MacConkey (indicator).
How is the culture presented for Shigella?
Shigella forms a non-lactose fermenting pale coloured or colourless and transparent colonies.
What is the preffered drug of choice to treat Shigella?
Antimicrobial therapy
For cases in which susceptibility is unkown or an ampicillin-resistant strain is isolated, Bactrim is the drug of choice.
What is Food Poisoning?
A non-specific term applied to the syndrome of acute anorexia, nausea and vomiting +/- diarrhoea that is attributed to food intake especially if it afflicts groups of persons. It may or may not be accompanied by fever.
What are chemically - related food poisonings?
- Ackee, mushroom poisoning
- Heavy metals eg. Copper, Zinc, Selenium, Cadmium
- Toxic fish poisoning eg. Shellfish - saxitoxin - clams, oysters - ciguatera - ciguatoxin-snapper - barracuda 4. Chinese Restaurant syndrome –MSG
- Salt petre: methaemoglobinemia
What is the pathophysiology for non- inflammatory diarrhoea from food posoining?
It is caused by action of enterotoxins on the secretory mechanisms of the mucosa of the SI without invasion (watery, no leukocytes)
What is the pathophysiology for inflammatory diarrhoea from food posioning?
It is caused by cytoyoxins on the mucosa leading to invasion & destruction. Colon or distal small bowel involved.
* Diarrhoea bloody with leukocytes.
