Tag: bacteria

Posted in Science & Nature

History Of The Earth

Posted on by Jinavie

The Earth has been around for a good 4.6 billion years. Let us compress the long time from the Earth’s birth to today (2012) into one year to put everything in perspective.

The Earth’s history starts on January 1, 00:00:00. The Earth is a hard sphere, barren as any other planet. Incessant wind and rain erode away the barren mountains and tectonic forces create new ones. Nothing much happens for the next three months. Then, around the start of April, life begins in the form of bacteria. Over the course of the next few months, the bacteria divide and mutate, slowly forming new life forms that are multicellular. However, all life on Earth are still in the oceans.

Life on land only starts in the end of November, when plants begin to settle on land. Plants expertly take the abundant carbon dioxide in the atmosphere and convert it into oxygen. By early December, the oceans are teeming with fish, some of which adapt to living on land by developing lungs. These become the first amphibians. Insects also populate the land and become one of the most diverse types of life.

In December 12, reptiles evolve and the land is ruled by dinosaurs, but only for 9 days until they are wiped off the face of the Earth by a meteorite on December 20. Mammals quickly take the niche left by dinosaurs, populating the entire world. Even at this late time, there are no signs of humans.

December 31, humans have still not arrived on Earth. They only appear around 8pm, where the first hominids venture on to the plains of Africa. At 10pm, the Ice Age begins and the Earth is covered by a thick white sheet of ice. The ice comes and goes three more times. At 11:59pm, human civilisation begins as cities begin to rise. 22 seconds before the end of the year, the Egyptians build their pyramids. More monuments arise within seconds. At 11:59:47pm, Jesus teaches the people to love one another, until he is killed a millisecond later. In the last second of the year (about 150 years), humanity: has two major world wars, take to the skies, create the nuclear bomb that can wipe out all life on Earth and even step foot on the Moon.

We may like to think that we have made a significant impact in the history of the Earth, but we have only existed for an infinitesimally small fraction of the history. We are but a dot on the grand scheme of natural history.

Posted in Psychology & Medicine

Tetanus

Posted on by Jinavie

Tetanus is an infectious disease caused by a soil-borne bacteria called Clostridium tetani. Patients are often infected soil entering the blood through deep wounds, such as a cut. The bacteria produces a toxin called tetanospasmin which leads to the characteristic symptoms of tetanus involving muscle.

The term tetanus actually refers to a state where skeletal muscle remains contracted and cannot relax due to maximum signalling from the nervous system. Tetanus is associated with some distinct symptoms involving tetanised muscles.

Tetanus starts in the face in the form of lockjaw (jaw clamps shut and cannot be opened) and sardonic risus sardonicus. Risus sardonicus, also known as sardonic grin, is a contorted, malicious-looking smile that is caused by spasms of muscles in the face. A good portrayal of the grin is seen in the Joker’s face from the Batman comic book series.
The disease then progresses to cause stiff neck, spasming of chest and leg muscles and difficulty swallowing. 

A dramatic symptom is opisthotonos, where the patient experiences extremely painful contractions of back muscles causing them to arch their back against their will. Along with lockjaw and risus sardonicus, it is a characteristic sign of tetanus and has been known for centuries. Before it was attributed to tetanus, people used to think the person was possessed by a demon due to the agonised screams and involuntary spasming of the body.

The disease is especially devastating in infants and can be spread to the fetus within the womb. This is because babies do not have a developed passive immune system that can combat the infection. Neonatal tetanus carries a mortality rate of over 90% and is responsible for 15% of all neonatal deaths.

Tetanus is a preventable disease through immunisation. Immunisation is done by injecting an inactive form of the toxin (i.e. cannot cause disease), inducing a reaction by the immune system. This essentially “teaches” the immune system to defend the body against tetanus. By completing a course of three doses and receiving occasional booster shots throughout life, tetanus can be prevented. Pregnant women must be immunised against tetanus to prevent neonatal tetanus (the babies receive scheduled immunisations soon after birth too).

This is one example of how immunisation can effectively prevent fatal diseases in a population.

Posted in Psychology & Medicine

Superbug

Posted on by Jinavie

Frequently on the media, the word “superbug” is used as if it were the new Black Death or the coming apocalypse. What is a superbug and why is it so feared?
Superbug is the colloquial nickname for drug-resistant bacteria. For example, one of the most famous superbugs is MRSA (methicillin-resistant Staphylococcus aureus). This strain S. aureus, a common bacteria found on skin and inside the nose, is resistant to a powerful antibiotic called methicillin and thus very hard to treat. Unfortunately, MRSA is most commonly contracted in hospital settings as patients are vulnerable to infections (e.g. after surgery) and hospitals are perfect breeding grounds for superbugs.

The cause of a “normal” bacteria turning into a superbug is due to the incorrect use of antibiotics. When antibiotics are used, they wipe out a significant portion of the bacterial population but fail to kill all of them in the first attack. The surviving bacteria are the more adapted ones that are able to withstand the harsh environment for a little longer. If the patient stops taking the antibiotics and the bacteria remains, these “drug-resistant” bacteria multiply to create a second infection that is resistant to the drug that was used previously. In fact, this is a classic example of natural selection in motion, except that the environmental change is man-made.
This is the reason why doctors are reluctant to prescribe antibiotics for diseases such as the common cold or viral diseases, as the risk of developing superbugs is greater than the benefit (which is zero in viral diseases as they do nothing) of the treatment. It is also why a course of antibiotics must be finished even if the patient is feeling well, so that even the surviving bacteria are eventually killed.

To show the potential risk of superbugs, the case of VRSA can be taken into consideration. When MRSA was first discovered, doctors found it very difficult to treat but luckily they had a secret weapon – vancomycin, one of the most powerful antibiotics known to mankind. However, they soon found that S. aureus and natural selection easily overcame this through a new strain called VRSA – vancomycin-resistant S. aureus. Here was a bacteria that could overcome the greatest weapon man had against bacteria, all because people were taking more antibiotics than needed and not taking the full course prescribed.

Thus, one of the growing problems of modern medicine is the development of new drugs so that we can make a comeback in the arms race against bacteria.