Tonsillitis, pneumonia, cystitis, school sores and conjunctivitis all have one thing in common - they are all
caused by bacteria. Bacteria are not all bad. They are essential for the production of many foods, from wine and
beer to mature cheese and yoghurt.
Bacteria are microscopic single celled organisms that are between 0.3 and 10 microns in length. A thousand
microns make one millimetre, or a micron is 0.0000001 of a metre. Bacteria are everywhere in the environment in
extraordinarily vast numbers. Every gram of soil contains between 1,000,000,000 and 20,000,000,000 bacteria, as
well as 10,000,000 to 50,000,000 fungi, about 20,000 algae and 100 to 1000 protozoa and other single celled
organisms. Amazingly, eight out of every ten cells in our bodies is actually a bacterium, and there are between 500
and 1000 different types of bacteria in a person’s body at any time. That means that we are more a bacteria than a
human. The ratios of these bacteria vary from one person to another, and can be as identifying as a fingerprint. It is
obvious that humans evolved with these bacteria and could not survive without them.
Human life would be impossible without bacteria as they are essential for our digestive systems, the
manufacture of some essential vitamins, and the good symbiotic bacteria even fight of the pathogenic ones.
Sometimes the beneficial bacteria multiply excessively or move to different areas of the body where they become
pathogenic (harmful). For example, the Escherichia coli bacterium is very common, and usually harmless in the gut,
but in the bladder it can cause a urinary infection. Other bacteria (eg. Mycobacterium tuberculosis that cause
tuberculosis) are always pathogenic.
Pathogenic bacteria can penetrate into healthy tissues, and start multiplying into vast numbers. When they do
this they damage the tissue that they are infecting, causing it to break down into pus. Because of the damage they
cause, the involved area becomes red, swollen, hot and painful. The waste products of the damaged tissue, along
with the bacteria, spread into the blood stream, and this stimulates the brain to raise the body temperature in order
to fight off the infection. Thus a fever develops.
The body is invaded by millions of pathogenic bacteria every day, but very few ever cause problems because
the body’s defence mechanisms destroy the majority of the invading organisms. The white blood cells are the main
line of defence against infection. They rapidly recognise an unwanted bacteria, and large numbers move to the
area involved to engulf the bacteria and destroy them. It is only when these defences are overwhelmed that a
noticeable infection develops.
Hundreds of bacteria are known to microbiologists (the doctors and scientists who study them), but only a few
dozen cause significant infections in mankind. All these bacteria have specific names and can be identified under a
microscope by experts who can tell them apart as easily as most of us can identify different breeds of dogs.
Every species of bacteria (and fungi, but not viruses) has two names - a family name (eg: Staphylococcus)
which uses a capital initial letter and comes first, and a specific species name (eg: aureus) that uses a lower case
initial letter and comes second. The golden staph bacteria which causes many serious throat infections is thus
called Staphylococcus aureus but may be abbreviated to S.aureus.
When an infection occurs, the patient usually consults a doctor because of the symptoms. If the infection is
bacterial, the appropriate antibiotics can be given to destroy the invading bacteria. Because different types of
bacteria favour different parts of the body and lead to different symptoms, a doctor can make an educated guess
about the antibiotic to use. When there is any doubt, a sample or swab is sent to a laboratory for expert analysis so
that the precise organism can be identified, together with the appropriate antibiotic to kill it.
Many bacteria, particularly those in the gut, are beneficial to the normal functioning of the body. They can aid
digestion, and prevent infections caused by fungi (eg. thrush) and sometimes viruses. Unfortunately, antibiotics can
kill off these good bacteria too, and so common side effects of the use of antibiotics are diarrhoea, and fungal
infections of the mouth and vagina.
The most common bacteria that attack humans, and the diseases they cause, or organs they attack, are listed
below.
BACTERIA DISEASE OR PLACE OF INFECTION
Bacillus Anthrax, tuberculosis.
Bacteroides Pelvic organs.
Bordetella pertussis Whooping cough.
Brucella abortus Brucellosis.
Chlamydia tracholatis Venereal disease, pelvic organs, eye.
Clostridium perfringens Gas gangrene, pseudomembranous colitis.
Clostridium tetani Tetanus.
Corynebacterium diphtheriae Diphtheria.
Escherichia coli Urine, gut, Fallopian tubes, peritonitis.
Haemophilus influenzae Ear, meningitis, sinusitis, epiglottitis.
Helicobacter pylori Peptic ulcers.
Klebsiella pneumoniae Lungs, urine.
Kingella kingae Mouth, throat, joints, bone
Legionella pneumophilia Lungs.
Moraxella Nose, ears, eye, lungs.
Mycobacterium leprae Leprosy.
Mycobacterium tuberculosis Tuberculosis.
Mycoplasma pneumoniae Lungs.
Neisseria gonorrhoea Gonorrhoea, pelvic organs.
Neisseria meningitidis Meningitis.
Proteus Urine, ear.
Pseudomonas aeruginosa Urine, ear, lungs, heart.
Salmonella typhi Typhoid fever.
Shigella dysenteriae Gut infections.
Staphylococcus aureus Lungs, throat, sinusitis, ear, skin, eye, gut, meningitis, heart,
bone, joints.
Streptococcus pneumoniae Throat, ear, sinusitis, lungs, eye, joints.
Streptococcus pyogenes Sinuses, ear, throat, skin.
Streptococcus viridans Heart.
Treponema pallidum Syphilis.
Vibrio cholerae Cholera.
Yersinia pestis Plague.
As a side curiosity, sharks never catch bacterial infections, and medical scientists are still trying to work out why.
See also FEVER; FUNGI; VIRUS
caused by bacteria. Bacteria are not all bad. They are essential for the production of many foods, from wine and
beer to mature cheese and yoghurt.
Bacteria are microscopic single celled organisms that are between 0.3 and 10 microns in length. A thousand
microns make one millimetre, or a micron is 0.0000001 of a metre. Bacteria are everywhere in the environment in
extraordinarily vast numbers. Every gram of soil contains between 1,000,000,000 and 20,000,000,000 bacteria, as
well as 10,000,000 to 50,000,000 fungi, about 20,000 algae and 100 to 1000 protozoa and other single celled
organisms. Amazingly, eight out of every ten cells in our bodies is actually a bacterium, and there are between 500
and 1000 different types of bacteria in a person’s body at any time. That means that we are more a bacteria than a
human. The ratios of these bacteria vary from one person to another, and can be as identifying as a fingerprint. It is
obvious that humans evolved with these bacteria and could not survive without them.
Human life would be impossible without bacteria as they are essential for our digestive systems, the
manufacture of some essential vitamins, and the good symbiotic bacteria even fight of the pathogenic ones.
Sometimes the beneficial bacteria multiply excessively or move to different areas of the body where they become
pathogenic (harmful). For example, the Escherichia coli bacterium is very common, and usually harmless in the gut,
but in the bladder it can cause a urinary infection. Other bacteria (eg. Mycobacterium tuberculosis that cause
tuberculosis) are always pathogenic.
Pathogenic bacteria can penetrate into healthy tissues, and start multiplying into vast numbers. When they do
this they damage the tissue that they are infecting, causing it to break down into pus. Because of the damage they
cause, the involved area becomes red, swollen, hot and painful. The waste products of the damaged tissue, along
with the bacteria, spread into the blood stream, and this stimulates the brain to raise the body temperature in order
to fight off the infection. Thus a fever develops.
The body is invaded by millions of pathogenic bacteria every day, but very few ever cause problems because
the body’s defence mechanisms destroy the majority of the invading organisms. The white blood cells are the main
line of defence against infection. They rapidly recognise an unwanted bacteria, and large numbers move to the
area involved to engulf the bacteria and destroy them. It is only when these defences are overwhelmed that a
noticeable infection develops.
Hundreds of bacteria are known to microbiologists (the doctors and scientists who study them), but only a few
dozen cause significant infections in mankind. All these bacteria have specific names and can be identified under a
microscope by experts who can tell them apart as easily as most of us can identify different breeds of dogs.
Every species of bacteria (and fungi, but not viruses) has two names - a family name (eg: Staphylococcus)
which uses a capital initial letter and comes first, and a specific species name (eg: aureus) that uses a lower case
initial letter and comes second. The golden staph bacteria which causes many serious throat infections is thus
called Staphylococcus aureus but may be abbreviated to S.aureus.
When an infection occurs, the patient usually consults a doctor because of the symptoms. If the infection is
bacterial, the appropriate antibiotics can be given to destroy the invading bacteria. Because different types of
bacteria favour different parts of the body and lead to different symptoms, a doctor can make an educated guess
about the antibiotic to use. When there is any doubt, a sample or swab is sent to a laboratory for expert analysis so
that the precise organism can be identified, together with the appropriate antibiotic to kill it.
Many bacteria, particularly those in the gut, are beneficial to the normal functioning of the body. They can aid
digestion, and prevent infections caused by fungi (eg. thrush) and sometimes viruses. Unfortunately, antibiotics can
kill off these good bacteria too, and so common side effects of the use of antibiotics are diarrhoea, and fungal
infections of the mouth and vagina.
The most common bacteria that attack humans, and the diseases they cause, or organs they attack, are listed
below.
BACTERIA DISEASE OR PLACE OF INFECTION
Bacillus Anthrax, tuberculosis.
Bacteroides Pelvic organs.
Bordetella pertussis Whooping cough.
Brucella abortus Brucellosis.
Chlamydia tracholatis Venereal disease, pelvic organs, eye.
Clostridium perfringens Gas gangrene, pseudomembranous colitis.
Clostridium tetani Tetanus.
Corynebacterium diphtheriae Diphtheria.
Escherichia coli Urine, gut, Fallopian tubes, peritonitis.
Haemophilus influenzae Ear, meningitis, sinusitis, epiglottitis.
Helicobacter pylori Peptic ulcers.
Klebsiella pneumoniae Lungs, urine.
Kingella kingae Mouth, throat, joints, bone
Legionella pneumophilia Lungs.
Moraxella Nose, ears, eye, lungs.
Mycobacterium leprae Leprosy.
Mycobacterium tuberculosis Tuberculosis.
Mycoplasma pneumoniae Lungs.
Neisseria gonorrhoea Gonorrhoea, pelvic organs.
Neisseria meningitidis Meningitis.
Proteus Urine, ear.
Pseudomonas aeruginosa Urine, ear, lungs, heart.
Salmonella typhi Typhoid fever.
Shigella dysenteriae Gut infections.
Staphylococcus aureus Lungs, throat, sinusitis, ear, skin, eye, gut, meningitis, heart,
bone, joints.
Streptococcus pneumoniae Throat, ear, sinusitis, lungs, eye, joints.
Streptococcus pyogenes Sinuses, ear, throat, skin.
Streptococcus viridans Heart.
Treponema pallidum Syphilis.
Vibrio cholerae Cholera.
Yersinia pestis Plague.
As a side curiosity, sharks never catch bacterial infections, and medical scientists are still trying to work out why.
See also FEVER; FUNGI; VIRUS
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