Dear Dr. B: What is a bacterium? What are the common bacteria which cause illnesses in humans?
Answer: A bacterium (bacteria is the plural of bacterium) is a very small, single-celled microorganism that can reproduce rapidly. A bacterium has no nucleus. Bacteria come in many shapes including spheres, rods and spirals. They are the most abundant living organisms on earth, and are found in all living things and in all of the earth’s environments.
Bacteria usually live off other organisms. A bacterium is a completely self-contained and self-reproducing unit. A virus, on the other hand, cannot reproduce without a living host.
Most bacteria are considered harmless. Many are beneficial to humans. A small percentage of bacteria, which are harmful, feed on the tissues of the human body and excrete toxins and acids afterwards which causes bacterial infection. Most viruses, on the other hand, serve no beneficial purpose. Their mission in life is to create more viruses in order to assure survival of the strain
Here are some examples of common illnesses caused by bacteria.
The most important human pathogens among the Gram-positive cocci are Staphylococcus aureus which causes skin and soft tissue infections and toxic shock syndrome. Pharyngitis is caused by Streptococcus pyogenes, neonatal meningitis is caused by Streptococcus agalactiae, pneumonia is caused by Streptococci pneumoniae and Enterococcus faecalis causes urinary tract infection.
Meningitis and gonorrhea is caused by the Gram-negative cocci called Neisseria. Gram-positive bacilli cause meningitis, pneumonia, soft tissue infections, brain abscess and diphtheria. There are many other groups of bacteria including the Gram-negative bacilli, the Enterobacteriaceae and others which cause variety of illnesses in humans.
The dawn of bacteriology started with Louis Pasteur (1822-1895). He was interested in the process of fermentation. He proved that fermentation was caused by bacteria or fungi. According to Illustrated History of Surgery, Pasteur studied fermentation of wine and beer and invented the process of pasteurization, which became very important in the dairy industry. He also found a vaccine against anthrax (an illness caused by bacteria).
Pasteur was not a doctor. He was a chemist and became professor of chemistry at the Sorborne in Paris. He also discovered bacteria called staphylococci and streptococci and explained their toxic effects. Pasteur also produced a vaccine against rabies (a viral disease), at that time thought to be incurable disease.
Robert Koch (1843-1910) along with Pasteur is credited with launching the first golden age of bacteriology. Koch was one of the first professors of hygiene and bacteriology in Berlin. Koch had developed an apparatus for keeping bacteria alive under the microscope. He discovered the bacteria which causes tuberculosis and cholera. Koch won the Nobel Prize in 1905.
Diseases caused by bacteria are many. We continue to fight the battle against the continuous onslaught from bacteria by developing different varieties of vaccines, medications and antibiotics. But bacteria have ability to change in order to survive treatment. This is called antibiotic resistance and this phenomenon is a growing concern among the health care providers. Overuse and inappropriate use of antibiotics result in bacteria developing resistance.
Our battle against bacteria will never be over. Just like viruses, they keep one step ahead of the game. We should continue to be vigilant in washing our hands and keeping our bodies and environment clean and healthy.
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