• Posted on February 22, 2013 7:45 pm
    By Chris
    Pathogenic E. coli unstained microscopic sample

    Today’s Diary Entry is sponsored by Spikes World

    The end of my second week back in my second semester of vet school and today is a killer. Animal Nutrition started at 8am and I am solidly in lectures and practicals until around 5:30pm today. The highlight of the day has to be a guest lecture by an emergency vet in Surrey on emergency fluid therapy.

    So animal nutrition today was looking at the determination of dry matter in animal feed. Basically the first step in understanding the nutritional value of a food is understanding just how much of it is nutrients and how much just plain water (which whilst important has little nutritional value). This is done by weighing and then heating the sample in a furnace until there remains no water, and then storing the sample in a desiccator whilst cooling to prevent the re-absorption of moisture. The sample is then weighed again and the difference in weight is the water content which is then used to calculate the dry matter of the feed.

    Then time for microbiology (well special bacteriology) and this week we spent it looking at Escherichia coli which is one of the most common bacteria. Most people have levels of E. coli existing as mutualist in the intestinal tract however if they get the chance they will cause disease. In fact there are two different types of E. coli strains, those that are pathogenic and those that are not pathogenic. Whilst being common the severity of some of the strains is horrifying, recently the strain E. coli 0157:H7 has emerged as a food borne, zoonotic pathogenic strain that causes the hemorrhagic colitis-haemolytic uraemic syndrome (aka causes the breakdown of blood vessels and tissues). This strain has a high mortality (death rate) with just between 10 – 100 of the bacteria required to be infectious. Anyways in the lab we are running standard protocols to gain proficiency in the identification of bacteria for later on in practice. The most basic of these is simply preparing a unstained sample for examination under the microscope which allows the observation of motility as many bacteria are killed by staining methods. This is a pathogenic strain of E. coli unstained under the microscope, these small rods are bacteria which are actually moving around…

    Pathogenic E. coli unstained microscopic sampleA stained sample was then prepared using the Gram Staining technique which allows basic identification of gram postive (which stain blue) and gram negative bacteria (which stain red).

    Gram Negative pathogenic strain of E. coli under the microscopeAnyways onto my last lecture of the day, the take home message was that even though fluids are commonly used they are still classed as drugs and if used incorrectly are lethal. Basically the fluid that makes up the body is either stored in the blood vessels, or outside of the blood vessels in and around cells. There are two situations with fluid loss, haemorrhage with fluid lost just from blood vessels, or dehydration where fluid is lost from across the entire body. Now obviously there is more fluid in the body than just in the blood so losing fluid just from the blood is life threatening whereas dehydration whilst needing treatment is not life threatening. On that note I will leave you for this week.

    This evening I am leaving for Budapest for the weekend, one of the benefits of attending a international university is making friends in many different countries and I’ve a friend going home to Hungary this weekend. I want to visit the Budapest Zoo, and the Aquarium to give me a jump start on my diseases of fish module for this semester (as well as to take a weekend away from dorms!).

    Posted in categories: Vet School Diary
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