Microbiology Nuts & Bolts
  • Home
  • Basic Concepts
    • What is infection?
    • Normal flora
    • Diagnosing infection
  • Microbiology
    • Basic bacterial identification
    • Interpreting bacteriology results
    • Interpreting serology results
  • Infection Control
    • What is infection control?
    • Universal precautions
    • MRSA
    • Clostridium difficile
  • Clinical Scenarios
    • Respiratory infections
    • Urinary infections
    • GI infections >
      • D&V
      • CDAD
    • CNS infections
    • Skin & bone infections
    • Sepsis
  • Antibiotics
    • Antimicrobial Stewardship
    • How antibiotics work
    • How to choose an antibiotic?
    • Reviewing antibiotics
    • Antibiotic resistance
    • Testing antibiotic resistance
    • Penicillin allergy
    • Theraputic Drug Monitoring
  • Guidelines
  • Lectures & Lecture Notes
    • Medical Students
    • Curriculum for the Foundation Program
    • Foundation Year 1
    • Foundation Year 2
    • Other Lectures
  • The Bug Blog
  • Buy the book...
  • NEW Edition Updates
  • Peer Reviews
  • Our Facebook page
  • Want to know more?
  • Contact

What eggs are you hoping for this Easter?

18/4/2019

 
​Yep, it’s coming up to that time of year. All of Microbiology is excited as there is about to be a holiday and eggs are likely to feature in a big way… no not Easter!!! Its holiday time and people will be going to exotic countries and bringing back souvenir parasites and their eggs will be involved in working out what is wrong with them. Yep us Microbiologists’ love eggs, not just the chocolate variety. I don’t know, you lot all have chocolate on the brain :-)
​Most intestinal parasites occur when someone ingests the eggs of a parasite, usually from faecally contaminated soil, which then hatch in the patient’s intestine and the parasite starts causing an infection.
 
Diagnosing intestinal parasite infections is actually quite difficult. There is sometimes a clue in the clinical history such as foreign travel or drinking potentially contaminated water, but most of the time in the UK we only tend to look for parasites when the clinical details say that diarrhoea has been going on for more than 2 weeks. Remember, clinical details are really important and where diarrhoea is concerned it is critical; so include travel history, pets, symptoms (e.g. bloody diarrhoea), contact with other people who are unwell and duration of symptoms.
 
Laboratory diagnosis of intestinal parasites
There is no easy way to say this; to diagnose most intestinal parasites you have to look at poo! Okay, some labs can do molecular tests for common parasites like Giardia lamblia and Cryptosporidium parvum but for most of the others it all comes back to looking at poo.
 
More particularly the laboratory is looking for the eggs of the intestinal parasites in the stool sample because the adult parasite itself is usually attached higher up in the bowel where it is laying eggs into the bowel lumen which are then mixed with faeces and passed.
 
The eggs of parasites are bigger than bacteria but you still need a microscope to see them; parasite eggs are usually >5 micrometres in diameter but sometimes >100 micrometres, whereas bacteria are usually about 1 micrometre. Rather than using x1000 magnification on a microscope, which we use for bacteria, we tend to use x100-400 instead.
 
Before we look for parasites in the stool sample we need to concentrate the sample so that we get as many eggs under the microscope as possible. This is usually done using a kit that filters out as much “organic debris” (yuck) from the sample whilst concentrating smaller particles in sediment at the bottom of the tube (see picture). The sediment is then put on a microscope slide and a cover slip placed on top so that it can be looked at in more detail.
Stool concentration technique
Click for larger image
In order to get the best chance of seeing any parasite eggs in stool it is good practice to look at at least 3 different stool samples before saying they are negative. The stool samples should be as fresh as possible, ideally within an hour of passing; otherwise the eggs may start to break down!
 
Appearance and size really does matter
Once the sample is under the microscope it is then a case of trying to find what looks like an egg and measuring how big it is. In this complicated world, we rely on human methods. Some of the more common eggs are easily recognisable such as Ascaris lumbricoides, Fasciola hepatica and Trichuris trichuria (which I always think looks like a tea tray) but others require an experienced eye to tell them apart. If you are unable to tell them apart by appearance then size matters and measuring them with a graduated eyepiece in the microscope (not a ruler!!) allows you to compare your image to pictures in order to identify what you are seeing.
 
So how many of these do you recognise?
Answers at the bottom...no pun intended!

Okay the last one was chocolate, but you will be glad to know that all of the others, however grim they look, are easily treatable with the right antimicrobial. The trick though is to work out which parasite you are dealing with and for that you really do need to take a close look at poo!

Have a great Easter and remember as far as I know eating Easter eggs is not a risk factor for infection!
Answers
1) Ascaris lumbricoides, 2) ​Entamoeba histolytica, 3) Enterobius vermicularis, 4) Fasciola hepatica, 5) Giardia lamblia, 6) Tinea sp., 7) Trichuris trichuria, 8) fizzy worm Easter egg

Comments are closed.

    RSS Feed

    Blog Author:

    David Garner
    Consultant Microbiologist
    Surrey, UK

    Please DO NOT advertise products and conferences on our website or blog

    Categories

    All
    Antibiotic Resistance
    Antibiotics
    Basic Concepts
    Clinical Scenarios
    Guidelines
    Infection Control
    In The News
    Microbiology

    Archives

    October 2020
    September 2020
    August 2020
    July 2020
    June 2020
    May 2020
    April 2020
    March 2020
    February 2020
    January 2020
    December 2019
    November 2019
    October 2019
    September 2019
    August 2019
    July 2019
    June 2019
    May 2019
    April 2019
    March 2019
    February 2019
    January 2019
    December 2018
    November 2018
    October 2018
    September 2018
    August 2018
    July 2018
    June 2018
    May 2018
    April 2018
    March 2018
    February 2018
    January 2018
    December 2017
    November 2017
    October 2017
    September 2017
    August 2017
    July 2017
    June 2017
    May 2017
    March 2017
    February 2017
    January 2017
    December 2016
    November 2016
    October 2016
    September 2016
    August 2016
    July 2016
    June 2016
    May 2016
    April 2016
    March 2016
    February 2016
    January 2016
    December 2015
    November 2015
    October 2015
    September 2015
    August 2015
    July 2015
    June 2015
    May 2015
    April 2015
    March 2015
    February 2015
    January 2015
    December 2014
    November 2014
    October 2014
    September 2014
    August 2014
    July 2014
    June 2014
    May 2014
    April 2014
    March 2014
    February 2014
    January 2014
    December 2013
    October 2013
    September 2013
    August 2013
    July 2013

    Categories

    All
    Antibiotic Resistance
    Antibiotics
    Basic Concepts
    Clinical Scenarios
    Guidelines
    Infection Control
    In The News
    Microbiology

    RSS Feed

Powered by Create your own unique website with customizable templates.