Unit 12A: Diseases and Infection
Introduction
I have been offered a chance to do a work experience placement at a clinic which offers an
insight into a career in pharmacy, physiotherapy or nursing. I am required to conduct research
into different types of infectious agents, the causes of non-infectious diseases and the relationship
between disease progression and the effects of this on human health. I will then produce two
separate case studies in relation to the disease processes involved in infectious and non-
infectious diseases.
Infectious diseases
(https://www.medicalnewstoday.com/articles/157973#types)
Bacteria
Bacteria’s Single-celled (unicellular) prokaryotic organism
characteristics Belongs to the Monera kingdom
Typical size ranges between 0.5µm – 1µm.
The composite of the cell wall is a protein-sugar
(polysaccharide) molecule – peptidoglycan
This is zootonic – can spread between animals and humans.
Bacteria’s structure Instead of having a nucleus, bacteria have a loose strand of
DNA (nucleoid or plasmid DNA)
The flagellum allows the bacteria to move around freely
The bacterial capsule’s job is to ensure that the bacteria is safe
from the host’s immune system.
The pili are short-hairs and its main job is to attach itself to
the surfaces that the bacteria wants to infect.
Unlike eukaryotic cells, bacteria have 70s ribosomes which is
smaller than the 80s ribosomes.
Contains cytoplasm – here this is where all of the chemical
reactions take place.
Reproduction Reproduces through the process of binary fission and cytokinesis.
- Firstly, the DNA unravels itself and will then be replicated by
proteins – which have been specialised – replaced them.
- After the DNA and plasmids have been replicated, they will
move to separate sides of the plasma membrane.
- Once this is finished, the cell wall and membrane will start to
break off and form two new identical daughter cells.
- Then, after the division is fully complete, any proteins or
molecules will break up and form inside the new identical
daughter cells.
The bacteria also have 4 main phases it follows during its growth and
reproduction, these being:
- Lag phase – This is a slow stage where there is zero growth of
the bacteria due to the bacterium making the necessary
, preparations for the cell division (e.g., replicating DNA,
synthesising new cell wall materials, etc).
- Log (exponential) phase – This is where the bacteria will then
start to divide and grow and an exponential rate, increasing
the overall number of bacteria. Lots of nutrients is consumed
and waste is produced as the bacteria is performing lots of
metabolic activity due to the cell division taking place.
- Stationary phase – This is when the growth of the bacteria
starts to slow down or plateau as cell division is no longer
taking place, this usually being as the bacteria has run out of
the nutrients it requires to reproduce.
- Death phase – This is the final stage for the binary fission
process and where the number of bacteria cells starts to
plumet as the cells start to die off – usually because of lack of
nutrients, cellular damage and being exposed to toxins.
The length of each phase will depend on the species of bacteria – some
may have a longer lag phase but a shorter log phase or vice versa.
Types of bacteria Has three main shapes: Bacilli (rod-shaped), Cocci (sphere-
shaped) and Spirilli (spiral-shaped).
Bacteria habitats Soil, water, radioactive waste, artic ice and the air
Nutrition Water, proteins, lipids, nucleic acids and low molecular weight
compounds.
Bacterial related disease: Cholera
Cholera is a short-lasting diarrheal illness and is caused by vibrio cholerae bacteria in the
intestine. This can be caught by drink water or eating food that is contaminated with the vibrio
cholerae bacteria.
, Although 32,000 people died of cholera between 1831-1832, cholera is usually a mild illness and
can rarely be life-threating in today’s society.
Cholera affects the small intestines by releasing toxins which will result in the body trying to
remove lots of water – either by urinating or faeces – this results in lots of electrolytes being lost
(calcium, potassium, magnesium, etc).
Cholera
Causes As stated above, Vibrio cholerae bacteria is the cause of cholera. The
bacterium then colonises within the small intestines and from here
starts to secrete toxins (choleragen - CTX), these toxins then supress
the standard immune response, allowing the bacterium to do more
damage to the body overall. Additionally, the toxins then cause Cl-
ions to move into the small intestines, due to osmosis the water will
go from a high concentration to a low concentration and leads to a
large loss in water. This can be spread very quickly in places where
sewage and water aren’t treated correctly. For example, Yemen,
Nigeria, and Bangladesh are places where Cholera rates are high.
The immune response takes place in the small intestines (Peyer’s
patches of the gastrointestinal mucosa) this is the region where
antigen presentation takes place (this just alerts the immune
response that invading pathogens are attacking the body). The
immune response will then make the antigens produce antibodies
which will then proceed to attack the Vibrio cholerae bacteria.
Symptoms - Muscle cramps and shock (due to electrolyte imbalance).
- Watery diarrhoea
- Vomiting
- Thirst
- Insomnia
- Dehydration
Diagnosis Scientists will request for a stool sample; from this they will be able
to isolate the Vibrio cholerae. Quicker tests are available like – stool
dipsticks and darkfield microscopy. The most common method is
the stool dipsticks as it gives the doctor a chance to quickly identify
if the patient has cholera or not in areas where they may not have
enough time for an in-depth diagnostic.
Life cycle The bacteria will first enter the body by aquatic solutions – water is
the most common one. After that the Vibrio cholerae will use
organic pollutants to attain its nutrients and to allow it to breed
more bacteria. The bacteria’s will then take around 2 hours to 5 days
for its incubation process and can kill within hours if it isn’t treated
quickly.
Effects on human body Cholera effects the body by draining it of its water and important
electrolytes, this will lead to the individual to go into shock and
become dehydrated. The lack of water will then result in the kidneys
not being able to carry out is function of filtering the blood due to
there not being lots of water the blood vessels will struggle to stay
open and flow freely, an increased likelihood of the formation of
kidney stones also will appear and this could potentially lead to
kidney infection - with a chance that the kidneys stop functioning all