What Microbiology is all about
The study of germs
There are 4 categories of microbes:
VirusesBacteriaYeast/FungiParasites
Viruses are the smallest microbes
They are too small to be seen with a light microscope and can only be seen with electron microscopes. Their size range is 20-300 nmThey are not capable of metabolic activity, Must infect a living cell to reproduce. Therefore they are not “Alive”They can exist outside of a living environment for a limited amount of time
This is a picture of a human immunodeficiency virus (HIV)
Most viruses can be grown in Tissue Culture
A tissue culture is a bottle with a single layer of cells growing on the inside of the bottleVirus is added to the bottleThe virus infects the cells, turning them into virus factoriesThe cell fills with virus, then explodes, releasing the virus which can be harvested
Some viruses can only be grown in fertilized eggs
Influenza virus is one of these
Some virus caused diseases are:
Common coldsInfluenzaAIDSHepatitis A, B, C, and DRabiesMeasles and mumpsSmallpoxHerpes viruses (Rubella, Herpes simplex I and II)
Influenza can cause major epidemicsIn 1918 there was an influenza pandemic that killed 50 million people. One fifth of the world’s population was infected
Last winter the world faced a new influenza epidemic
This new epidemic was the re-emergence of H1N1 virusTo prepare for the new epidemic laboratories began making H1N1 vaccine as soon as the virus was identified, in order to have the vaccine ready when the winter flu season hit. Influenza still remains a serious disease
AIDS-Acute Immunodeficiency Disease syndrome
HIV, the virus that causes AIDS is a new virusIt emerged in the 1970 from Africa where it had been a virus in monkeysInitially it was found in gay men, Haitians and IV drug users
Smallpox, measles, and polio caused their own epidemics
Smallpox caused epidemics around the world until a vaccine was discovered by Edward Jenner in 1798In 1980 the WHO officially declared the whole world to be free of smallpox
Both Measles and Smallpox were used as biological weapons
These diseases wiped out native populations coming into contact with them for the first time. Both were used as biological weapons against Native Americans during the settlement of North America. Infected blankets and other goods were given to the susceptible populations and wiped them out.
Polio caused epidemics during the 20th century until the first vaccine was discovered in 1952
Polio caused paralysis or even death.The disease was spread by person to person contact like the common cold.The Salk vaccine discovered by Jonas Salk in 1952, it was made from killed virusThe Sabin vaccine made with live attenuated virus was discovered in 1958 and supplanted the killed virus Salk Vaccine.Today polio is almost unknown, even in 3rd world countries.
Some polio patients were paralyzed from the neck down and spent the rest of their lives in iron lungs
Some viruses can only be grown in embryonic eggs
This is how influenza virus is grown
At the present time we only have anti-viral medicines for a few diseases.
Vaccines are available for many deadly diseasesThere are anti-viral agents that can shorten the amount of time you are ill, for example, Tamiflu for influenzaThere is a regimen of agents that control but do not kill the AIDS virus
Bacteria can be equally deadly
Bacteria are visible with a light microscope. They are a few micrometers longThey are prokaryotic cells. This means that they do not have a nucleus but their nuclear material is distributed throughout the organism.They come in various shapes; rods, spheres and corkscrews.Most bacteria can be grown on agar
A few bacterial diseases are:
Plague Yersinia pestisStaph infections including methocyllin resistant staph Staphlococcus aureusStrep throat Streptococcus pyrogenesGonorrhea Neisseria gonorrheae Syphilis Treponema pallidumLeprosy Mycobacterium lepraeTuberculosis Mycobacterium tuberculis
The plague killed one third of the people in Europe during the mid 14th century
Thought to have been brought to Europe by Ghengis Khan and his hordeSpread by the fleas from black (roof) ratsAn infected flea would bite a rat, the rat would become infected and ill. Infected fleas would leave the dying rat and bite the inhabitants of the house.Death in humans would occur within x number of hours. As the disease spread, it modified so that there was human to human spread.
How plague spread
Syphilis was brought to the old world from the new world by Columbus and the explorers who came after him
The first outbreak in Europe occurred during the War of Naples in 1494When this disease first came to Europe it caused disfiguring lesions all over the face of victims, and they often died within 3 to 4 months.The disease has become less virulent in the 5 centuries since then, and now causes a chronic disease that can be treated, but if untreated, will not kill the patient for 20 to 50 years.
Syphilis has 3 stages, the first stage is infectious and the 3rd (and final) stage is neurological
Famous people who had Syphilis:
Napoleon Bonaparte, King Henry VIII of England, Karin Blixin (wrote Out of Africa) Vincent Van Gogh, Al Capone, Paul Gauguin, Tsar Ivan the Terrible, Oscar Wilde, Leo Tolstoy, Fredrick Nietzche and the captain of the Pinta (one of Columbus’s boats)
An image of Treponema pallidum: this bacterium is called a spirochete.
Most bacteria can be grown on agar plates
This picture demonstrates several different bacteria growing on blood agarYou can see white colonies, some green colonies and some that clear the agar. These are all different organisms
Most bacteria can be seen through a light microscope
This is what staph bacteria look like with a light microscope.
Bacteria come in different shapes
They may be rod shapedThey can be round and grown in clustersThey can be round and grow in long chainsThey may be corkscrew shaped like the spirochete that causes syphilis
Images of rod shaped bacteria and bacteria in chains
Most bacteria are susceptible to antibiotics, which have been available since the 1940s
Antibiotic: anti means against, biotic means life. Early antibiotics were made from molds that killed bacteriaIn 1928 Alexander Fleming discovered that the mold penicillium would kill staphlococcusModern antibiotics are no longer made from molds but are discovered in laboratories.
This is what Alexander Fleming saw when he discovered penicillin
Yeast/fungal diseases
Yeast and Fungal diseases range from:Annoying and commonplace like ringworm, athletes foot and yeast infectionsTo deadly difficult to treat diseases such as Histoplasmosis, Cryptococcosis and Coccidiomycosis
Yeast and fungi are eukaryotic cells
They contain a nucleusAnd a cell wall like plants doThey belong in the Fungi kingdom which is separate from the kingdoms of plants, animals, and bacteria
Pictures of a budding yeast and of a fungus
Yeast and fungi can be cultured much like bacteria
Minor fungal diseases such as ringworm and fungal nail infections
Life threatening yeast/fungal infections
Fighting fungal infections
There are anti-fungal drugsMost are toxicMost fungal infections take a long time to treatThe failure rate for anti-fungal drugs is high
The fourth group of microbes is parasites
There are protozoans, one cells animals such as amoebae which cause diseases as diverse as dysentery and malaria
Malaria is an amoebic disease carried by mosquitoes
One million people die from it each year mostly children under the age of 5There are 250 million cases per yearMost of the cases are in sub-Saharan Africa3.3 billion people live where malaria is a threat
Helminths are worms and flukes
Helminthic diseases includeTapeworms such as fish, pork and beef tapewormsFlukes of the blood, liver and lungs
Roundworms like hookworms and pinworms
The size range of parasites
Amoeba 10-20 micrometersRoundworms 0.5mm to 1 cmFlukes 5mm to several cmTapeworms 1mm to 15 m (50 feet)
There are both anti amoebic and anti helminthic drugs,but there is not treatment for all amoebic or helminthic diseases.
Normal Flora
All living organisms have viruses, bacteria, yeast/fungi and parasites living on them and in themIn a healthy organism these microbes are beneficialThe normal flora varies from organism to organism
Normal flora varies according to the site and the organism
Not all humans have the same floraIt varies according to where you live and what you are exposed toIt varies according to the part of the body. Organisms that live on your skin are different from those in your mouth or in your intestines.
Some parts of your body are sterile—without normal flora
BloodBrainsMusclebones
The End
