Pathogens and Diseases.

University Degree Medicine and Dentistry

Pathogens and Diseases (IB Biology)

I. The Nature of Disease

1. Definitions

a. Disease is a medical condition in humans: a condition that results in medically significant symptoms in a human. Every disease has certain characteristic effects on the body called symptoms and signs.

b. Non-Infectious Disease are caused by microscopic organisms that invade the body, but does not communicated(spread) from person to person and do not have, or are not known to involve, infectious agents.

c. Infectious diseases are caused by microscopic organisms that invade the body and can spread from one person to another.

d. Pathogens are the microorganisms which enters the body causes disease (eg. bacteria or virus).

2. Types of Pathogens

3. Six ways in which pathogens are transmitted and gain entry into the body:

Contact—when an infected person touches an uninfected person, the pathogen can enter through the skin.
Cuts—Pathogen enters the body where the skin is cut by contaminated object.
Droplets—when an infected person coughs or sneezes, their droplet contains pathogens which will transmit the disease if breathed by an uninfected person.
Food or water— pathogens in contaminated foot and or water can enter the body through the soft gut wall.
Sexual intercourse—sexually transmitted disease gain entry through the soft mucous membranes of the penis and vagina.
Insects—blood sucking insects inject their mouthparts through the skin, and can transmit pathogens that they sucked from an infected person

4. Report on human bacterial disease: Bacterial Pneumonia

a. Cause

There are several causes to pneumonia including viruses, bacteria, mycoplasmas (small, free-living particles with characteristics of both bacteria and viruses), and fungi. Infection with the Streptococcus pneumoniae bacterium, also called pneumococcus, is the most common cause of bacterial pneumonia.

Streptococcus Bacteria

This scanning electron micrograph shows disease-causing Streptococcus bacteria, commonly found in the human mouth, throat, respiratory tract, bloodstream, and wounds. Often airborne in hospitals, schools, and other public places, Streptococcus bacteria are responsible for infections such as strep throat, scarlet fever, and some types of ...

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4. Report on human bacterial disease: Bacterial Pneumonia

a. Cause

Streptococcus Bacteria

b. Transmission

Since pneumonia is a disease which attacks the human ventilation system, it is most commonly spread through sneeze and or cough droplets. The droplets from coughing or sneezing from people who has been infected by pneumonia contain bacteria (pathogens). Another person can be infected easily if they breathe in the droplets, because then the bacteria would have enter the lungs and starts to grow and divide there.

c. Effects (Symptoms)

Pneumonia causes inflammation of one or both lungs. In people with pneumonia, air sacs in the lungs fill with fluid, preventing oxygen from reaching blood cells and nourishing the other cells of the body. In bacterial pneumonia, the usual symptoms include a shaking chill followed by a fever of about 40°C (104°F), pain in the chest while breathing, a cough, and blood-streaked sputum.

In bronchopneumonia, the inflammation occurs in scattered patches in the tissue around the ends of the bronchioles, the smallest air tubes in the lungs. In lobar pneumonia, the inflammation is widespread and involves an entire lobe of the lung. In the United States about 5 million cases of pneumonia are reported each year and about 63,500 people die from the disease.

5. Antibiotics

Antibiotics are agent that destroys bacteria: a substance that is able to kill or inactivate bacteria in the body. Antibiotics are derived from microorganisms, especially fungi, or are synthetically produced.

a. Antibiotics are commonly prescribed with to help the body to fight bacterial diseases. Antibiotics such as has been used to treat bacterial pneumonia.

b. Antibiotics are useless against viruses because virus does not carry out the process of growth and reproduction themselves. They rely on host cells to carry out the process for them. Thus it is not possible to block these processes without also harming the host cells, and therefore viruses cannot be treated by antibiotics.

II. Defense against Infectious Disease: Non Specific Immunity & Specific Immunity

6. Non-specific and specific immunity

Non Specific immunity is a quick-response system, which is present from birth. It is very effective against a wide range of pathogens and foreign substances, and it always gives the same type of response.

Specific immunity is an immunity system which is effective against specific pathogens, but reacts slowly. This includes cells and protein within the blood and lymph, which attack, disarm, destroy and remove foreign bodies.

7. Barriers to infection (features of the human body which prevent micro-organism from entering the body)

IB Biology: Pathogens and Diseases

22 March 2004