Microbiology Lab – Medlab science

Here are a few photos collected from different labs during our parasitology sessions; super interesting ! 

Plasmodium falciparum – varied cycle stages present

Cat dissection (Not actually part of our lab but it was lying around)

Another one of Plasmodium falciparum with more stages

Ancylostoma duodenale – hookworm

Pediculus humanus – lice

Sarcoptes scabiei – causes scabies

Pediculosis pubis – causes the std crabs


Amoebae – Entamoeba histolytica

Hi guys, its been a long time since I did a post on any organisms (will also try to get a post up on Transfusion soon). I’ve decided to do a post on amoeba’s since we just learnt them today and they’re fresh on my mind 🙂

Amoeba’s are a class of Protozoa. Protozoa are unicellular, eukaryotic organisms. Their cytoplasm is composed of an outer layer and an inner layer. The outer layer is called the ectoplasm and is gel like whereas the inner layer (endoplasm) is more liquid like.One species in particular Entamoeba histolytica (E. histolytica) is a human pathogen.

Entamoeba histolytica / dispar

Morphologically speaking, E. histolytica and E. dispar are very similar and cannot be distinguished so I have categorised them together. However, E. dispar is not pathogenic to humans.

E. histolytica causes amoebiasis and has a higher incidence in tropical areas but infections are distributed worldwide. Around 10% of the entire world is infected with this organism and guess what, its estimated that for every person infected, there are another 10-20 more people that are asymptomatic carriers (that’s a whoooole lotta people) !

Infections are usually associated with poor sanitation and developing areas. Humans are the reservoir host and can transmit infections to other humans and animals (dogs, cats, pigs, primates). They are transmitted mainly via the faecal-oral route, especially from asymptomatic individuals and food handlers that contain cysts. Other possible transmission methods is venereal (sexual transmission). The organism can reside harmlessly within the large intestine but they can colonize and penetrate the intestinal tissue, resulting in ulcers. They can then metastasize to other organs.

Life Cycle

There is no intermediate host and infection occurs by ingesting a mature cyst. The cyst is resistant to environmental conditions and act as the reproducing and transmitting agent. The cyst becomes active when it reaches the lower small intestine as the pH is more neutral / alkaline compared to the stomach. One amoeba containing 4 cystic nuclei emerges, undergoes mitosis and gives rise to 8 small uninucleated metacystic trophozoites. They mature as they reach the large intestine and usually colonize at the caecum where conditions are favourable.When the trophozoites are in the intestinal lumen, they begin the path of passing out of the body. If this passage is not rapid (stool is formed), only cysts will be seen in the stool during diagnosis. If the passage is rapid (stool is diarrhoeal), then trophozoites will be seen as they haven’t begun forming into cysts yet.

Clinical Significance

Intestinal disease with a variable incubation period (few days – weeks – months). People that are asymptomatic do not show occult bleeding in their stools but do excrete cysts (no tissue invasion). E. histolytica can cause amoebic dysentery – which is acute diarrhoea with ulcers on the mucosal surface of the colon. The ulcers are flask shaped, with a narrow opening and ballooned area below the surface that is filled with pus. Symptoms are:

  • lower abdominal pain
  • frequent bowel movements
  • tenesmus
  • fever
  • dehydration
  • electrolyte imbalance
  • and in severe cases, blood diarrhoea

Patient’s can also present with amoebic colitis – the chronic form which has similar symptoms but with alternating periods of constipation over a long course. If the infection metastasizes, the most common organ that is next affected is the liver. This results in amoebic abscesses in the liver and symptoms include right abdominal pain, fever, sweating, weakness, weight loss, cough, haepatomegaly and jaundice may also be present. Cutaneous lesions can also be affected (i.e. the skin around the anus), which is especially seen in toddler’s when the stool may be in contact with the skin for longer periods of time. The other form of disease is amoeboma – a growth of granulomatous tissue which results in a large local lesion in the bowel that resembles carcinoma.

Below are some photos I took during my lab today of Amoebae. However they aren’t E. histolytica and are non-pathogenic. With the exception of Giardia lamblia which is a flagellate and can cause Giardiasis.


Giardia lamblia



Entamoeba coli – trophozoite



Iodamoeba butschlii – cyst




Micro Lab

Below are just some photos I took last week when reading some of the results for 4 unknown organisms. I didn’t manage to take a photo of the yeast cells under the light microscope because I couldn’t align my camera to the optical eye piece 😦

We will be discussing our choice of tests and what organisms they were tomorrow, eek! Wish me luck, I already know I got one incorrect.

For those of you that noticed that a antimicrobial plate is missing for Unknown A, it’s because that was a yeast (I’m suspecting Candida based on my results) so there was no need to perform any antimicrobial resistance as it is of course, not a bacteria. The zone of no growth is measured with a ruler and there are set measurements for each specific antibiotic and its concentration that determine if an organism is susceptible or not, even though there is a clearing it needs to be of a certain diameter so its important to measure accurately!


Unknown C Antimicrobial plate


Unknown D Antimicrobial plate


Unknown B Antimicrobial plate


Positive Citrate


Oxidative Glucose (left tube is anaerobic and right is aerobic)


Aspergillus species

The Aspergillus genus is an opportunistic fungi that often presents in immunocompromised people. They have limited virulence but can cause local or disseminated disease. Examples of immunocompromised people are patients that receive irradiation, organ transplants, broad spectrum antibiotics, surgery, immunological disorders or chronic infections. Opportunistic fungi are usually ubiquitous in nature or part of our normal flora, making them hard to avoid.

The four species most commonly pathogenic worldwide are Aspergillus fumigatus complex, Aspergillus niger complex, Aspergillus flavus complex and Aspergillus terreus complex.

They are filamentous, thermally monomorphic and saprophytic moulds found widely in the environment. Their conidia are easily spread and affect humans by inhalation of their spores.

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Legionella species

Hi guys! I have an interesting organism today 🙂

The organism I will be doing a post on today is quite famous in the microbial world because of its history. I don’t usually mention the history of the organism’s in my post but I will briefly mention it here. During an American Legion convention in Philadelphia in 1976, 200 people contracted a severe multi-system disease that included pneumonia. Off the 200 affected, 29 people eventually died from this disease. It was later found to be caused by Legionella pneumophila (L. pneumophila) which resided in the hotel’s air conditioning system.

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