Diseases and Infections
A.P1 Explain the characteristics of the five main types of pathogens and a disease caused by each.
What are the main features of bacteria, why are they useful to infection, how can you tell if a
substance
is a bacteria, what is the life cycle of bacteria
Structure of Bacteria
A class of single-celled microorganisms known as bacteria occasionally dwell in colonies. A
bacterium is a prokaryote because it lacks a nucleus and has genetic material that is loosely
packed in the cytoplasm. The DNA typically consists of one ring-shaped chromosome and one
or more plasmids, which are likewise made up of genetic material. Bacteria have the ability to
swap plasmids. This is known as conjugation which allows them to recombine. This permits for
the continual emergence of novel bacterial strains. Typically, bacteria are so tiny that they must
be observed under a microscope. The internal structure of the bacteria consists of cytoplasm
and DNA. There is a cell membrane also present to surround the cytoplasm. The cell membrane
is then surrounded by a capsule that is composed of
peptidoglycan. Some species of bacteria also have
protrusions on the outside of the cell that are
referred to as flagella or pili which help the
prokaryote to move.
Size & Reproduction
The majority of bacteria use binary fission to spread.
Conceptually, this is a straightforward procedure; a
cell only needs to double in size before splitting in
half. A bacteria must split at the proper time and
location, and it must give each offspring a full copy of
its vital genetic material in order to continue to be
viable and competitive. Under favourable conditions,
bacteria are able to reproduce every 20 minutes.
Bacteria have an average length of 0.2-2.0 micrometres in diameter. However, depending on
the species and type of bacteria the size can vary by increasing to approximately 1 and 10
micrometres. For example, E.coli bacteria can have a size range between 1.1 and 1.5
micrometres whereas B. Anthracis can have a diameter ranging from 1 and 2 micrometres.
Bacteria present different shapes and sizes with several distinctive physical features to cope
and adapt to their surrounding external conditions. The shapes of the bacteria are used to
distinguish the several types of bacteria to implicate them into a systematic classification.
There are some structures of bacteria that are shaped as spheres in different arrangements
such as being encapsulated or being arranged in a chain-like shape. These are known as coccus
and streptococci. Others such as bacilli are rod-shaped and spirits are spiral wound shaped.
P2 Explain the causes of non-infectious diseases in humans
, Tuberculosis (Environmental)
A person contracts tuberculosis (TB) by breathing in microscopic droplets from an infected
person's cough or sneeze. Although it mostly affects the lungs, it can also have an impact on the
stomach (abdomen), glands, bones, and nervous system. Although TB has the potential to be a
serious infection, the correct drugs can cure it.
Causes of TB
A bacterial infection caused TB. The most contagious form of TB, known as pulmonary TB,
normally only spreads after prolonged contact with an infected person. In the majority of
healthy individuals, the immune system, the body's natural defence against infection and
disease, destroys the bacteria and there are no symptoms. Even when the immune system is
unable to eradicate the bacteria, it can sometimes stop it from spreading throughout the body.
Although you won't experience any symptoms, the microorganisms will still be present in your
body, this is known as “Latent TB”. Latent tuberculosis patients are not contagious. The
infection can spread to the lungs or other parts of the body if the immune system is unable to
eradicate it or keep it under control, and symptoms will appear within a few weeks or months,
this is known as “Active TB”. Latent tuberculosis may
subsequently become active TB, especially if your
immune system is compromised.
Symptoms of TB
● Cough that lasts longer than 3 weeks that may
produce bleeding phlegm
● Weight loss
● Night sweats
● Fever
● Exhaustion
● Lack of appetite
● Swelling that doesn’t do down for weeks
Diagnosis of TB & the Effects on the Human Body
A common test for latent TB is the Mantoux test. It entails injecting PPD tuberculin into the
skin of your forearm in a very little quantity. Also known as the tuberculin skin test (TST).
Your skin will be sensitive to PPD tuberculin if you have a latent TB infection, and usually 48 to
72 hours after the test, a little, firm red bump will appear at the injection site. To determine
whether you have active TB disease, you might need a chest X-ray if you get a very strong skin
reaction. The Mantoux test won't cause your skin to react if you don't have a latent infection.
Yet because TB might take a while to manifest, you might need to undergo another screening in
the future. The Mantoux test may cause a slight skin reaction if you've received the BCG
vaccine. This does not imply that you have latent TB in all cases. Although TB usually affects
the lungs, it can also have an impact on the brain, kidneys, or spine. If TB patients do not receive
treatment, they risk dying.
Life Cycle of TB Pathogen