HC21: Essential microorganisms

Clinical symptoms

One microorganism can cause 1, 2, 3 or many more clinical symptoms.

Vibrio cholera

The bacteria vibrio cholerae is a curved gram-negative bacteria that causes cholera. Cholera is an epidemic in many countries, mainly where hygiene is a problem. The bacterium has several characteristics:

• Is a vibrio → is curved
• Has a flagellum → makes rapid movements possible

The bacterium is spread by drinking contaminated water or direct contact between people. Not everyone who is a carrier becomes sick, but people with acid-inhibitors, elderly and children are more susceptible.

It is a non-invasive micro-organism → it doesn't cause inflammation or fever. There is no host response involved, but it does produce a cholera toxin. It is a toxin-mediated disease, which causes hyperactivity of the cell → pumps which pump water and elektrolytes out of the cell are activated:

1. The cholera toxin can bind to the membrane of the villi via a G-protein
2. cAMP is activated irreversibly in the cell
3. cAMP leads to an active secretion of kalium, natrium, chloride, bicarbonate and water → results in a watery diarrhea
   • This is called rice water stool

The pumps can pump up to 15 L a day. This can cause dehydration and a low blood pressure, especially among children.

Taenia saginata

The taenia species is a species of tapeworms in the bowel. Humans are the definitive host. The worms make eggs, which can be eaten by cows, causing the taenia to reproduce. Cows are the intermediary host → when a person eats raw cow meat, they can become infected.  Another taenia species is taenia solium.

Legionella pneumophila

The legionella bacterium is a gram-negative bacterium that is very small. Legionella pneumophila can lead to 2 diseases:

• Pneumonia
  • If someone is T-cell immunocompromised
• Pontiac fever

Legionella survives in the cell → it needs help from T-cells to be destroyed

The legionella bacteria thrive in warm water → they mainly reside in man-made water systems like air conditioning, saunas, showers and hot tubs. Transmission goes via air particles → aeriosoles. One person cannot infect another with it.

Treponema pallidum

The bacteria treponema pallidum can cause Syphilis. The bacteria is gram-negative and is mainly spread via genital or oral mucosal contact. The disease comes in phases:

1. Ulcer on the genital organs (or somewhere else)
2. The ulcer disappears for a while
3. Fever and skin rash
4. The symptoms disappear again
5. Gumma (a swelling)
   • This only happens in a few cases
   • Can also occur in the brain

Treponema pallidum came to Europe for the first time after Columbus returned from the Americas. It usually is diagnosed with serology.

Schistosoma

Schistosoma is a worm that lives in the water, mainly in Africa. Humans are definitive hosts, snails are intermediate hosts. People are exposed to it by being in infected water:

1. The worm enters the body via the skin and causes swimmers itch
2. The worm migrates and starts to look for a pleasant place to live → goes through the lungs
   • This can cause coughing
   • When the worm starts to migrate, it is called Katayama syndrome
3. The worm goes to the veins and liver to mature
4. The worm starts to lay eggs, which get stuck in the tissue of the bowel or bladder
5. When the worms are mature, they create granulomata in the third stadium which makes it possible for the worms to be released on the other side of the tissue

Borrelia burgdorferi

One clinical presentation can be caused by many different microorganisms. Lyme disease is characterized by painless, non-itching spots, with a red border and non-red inside → erythema migrans.

The disease is caused by Borrelia burgdorferi → bacteria which are carried by ticks. The tick needs to days to fill itself with human blood → only when the tick becomes engorged with blood, the bacteria comes to the mouth part of the tick and can be transmitted. Lyme disease has several stadia:

1. First stadium: erythema migrans
2. Second stadium: meningitis, arthritis and carditis
3. Third stadium: neuro(psycho)logical symptoms

Streptococci and staphylococci

A red, swollen and warm arm can be caused by 2 bacteria:

• Streptococcus pyogenes
  • A gram-positive coccus
  • The cause in case the lymphatic pathway is red
• Staphylococcus aureus
  • The cause in case there is a swelling

These infections usually are caused by something being wrong with the barrier.

Multiple symptoms

Several microorganisms can cause to many different symptoms and diseases:

• Enterovirus
• Staphylococcus aureus
• Streptococcus pyogenes
• Escherichia coli
• M. tuberculosis

Multiple microorganisms

There are symptoms which can be caused by multiple microorganisms.

Mononucleosis:

If a patient has mononucleosis, there are 4 possibilities:

• Epstein-Barr virus
• Cytomegalo Virus (CMV)
• Toxoplasma protozoa
• HIV

These microorganisms give the same symptoms: fever, lymphadinitis and lymphocytosis

Pneumonia:

Another example is pneumonia, which can be caused by:

• Viruses
  • Influenza virus
    • Causes irregular of interstitial pneumonia
  • RSV
    • Causes irregular of interstitial pneumonia
• Bacteria
  • S. pneumoniae
    • Has a polysaccharide capsule as a virulence factor
    • Causes lobar pneumonia
  • Mycoplasma
    • Causes irregular of interstitial pneumonia
  • M. tuberculosis
    • Causes a cavity or cyst
  • Legionella
    • Causes lobar pneumonia
• Fungi
  • Aspergillus
    • Causes a cavity or cyst
• Several worms
  • • Causes a cavity or cyst