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Prevention and Treatment of Diseases Caused by Microorganisms

SCIENCE • Form 5 • Chapter 1: Microorganisms

1.3 Prevention and Treatment of Diseases Caused by Microorganisms

Harmful microorganisms that cause diseases are called pathogens. To manage infectious diseases, healthcare relies on two approaches: preventing infection before it occurs and treating diseases after infection.

Learning Objectives

  • Define aseptic techniques and identify the five main aseptic techniques.
  • Explain the process and methods of sterilisation (heat, chemical substances, radiation, high pressure, filter).
  • Compare and contrast the use of boiling, antiseptics, disinfectants, and radiation.
  • Describe the purpose of antibiotics, the causes and dangers of antibiotic resistance, and the relationship between antibiotic concentration and bacterial growth.
  • Identify the pathogens that cause pneumonia, athlete's foot, and shingles, and state the appropriate treatment for each disease.

Summary of Aseptic Techniques and Disease Treatments

Preventive techniques stop pathogens before infection; targeted medicines treat the pathogen after infection.

A diagram comparing prevention and treatment. Prevention shows living tissue matched to antiseptics and non-living surfaces matched to disinfectants. Treatment shows bacterium matched to antibiotic, fungus matched to antifungal, and virus matched to antiviral. PREVENTION TREATMENT Living tissue Antiseptics acriflavine, povidone, 70% IPA Safe for skin and wounds Non-living surfaces Disinfectants bleach, hydrogen peroxide, liquid chlorine Not suitable for skin or wounds Bacterium Antibiotic e.g. penicillin Treats bacterial infections Fungus Antifungal e.g. clotrimazole Treats fungal infections Virus Antiviral e.g. acyclovir Treats viral infections

Short Explanation

What is an aseptic technique?

Aseptic technique is a healthcare procedure carried out to prevent infections caused by pathogens or to remove existing pathogens.

Controlling infectious diseases requires two complementary strategies: prevention and treatment. Aseptic techniques help prevent or eliminate pathogens in line with the phrase "prevention is better than cure". When infections occur, specific medicines such as antibiotics, antifungals, and antivirals are used to treat them based on the causative pathogen.

Five main aseptic techniques. Sterilisation, boiling, use of antiseptics, use of disinfectants, and use of radiation.

Methods of Sterilisation

Sterilisation is the process of killing or eliminating microorganisms from an object or a particular surrounding.

Methods of sterilisation and examples.
Method Example
Heat Autoclave — temperatures above \(130\text{ }^\circ\text{C}\) kill microorganisms and their spores.
Chemical substances Soap.
Radiation Ultraviolet (UV) rays.
High pressure Pressure cooker.
Filter Micron filter — used to filter fine particles and microorganisms measuring \(0.1\text{ }\mu\text{m} - 10\text{ }\mu\text{m}\) from liquids or water.

Boiling

Boiling water at a temperature of \(100\text{ }^\circ\text{C}\) is used to kill vegetative microorganisms on everyday objects such as milk bottles, injection needles, and dental equipment. Boiling does not destroy bacterial spores.

Antiseptics vs Disinfectants

Comparison between antiseptics and disinfectants.
Feature Antiseptic Disinfectant
Application Site Applied directly on living human skin or wounds. Applied on non-living objects (e.g., bed sheets, toilets, swimming pools).
Purpose Prevents pathogenic infections. Kills microorganisms, especially pathogens, on surfaces.
Suitability for Skin Safe for skin and wounds. Not suitable for skin or wounds (can cause tissue damage).
Examples Acriflavine (yellow medicine), povidone, 70% isopropyl alcohol (IPA). Bleach, hydrogen peroxide, liquid chlorine.
Action Acriflavine and povidone kill microorganisms; proflavine blocks/prevents microbial growth; 70% IPA acts as an antiseptic and sterilising agent. Destroys pathogens on inert surfaces.

Radiation

Ionising radiation includes ultraviolet (UV) rays, X-rays, and gamma rays. These rays penetrate microbial cells and destroy them. Ultraviolet rays from UV lamps are used to disinfect operating theatres.

Antibiotics and Antibiotic Resistance

Antibiotic is a medicine used specifically to treat infections caused by bacteria. Antibiotics are not effective against viral infections such as the common cold, cough, or flu.

Antibiotic resistance occurs when bacteria develop the ability to survive exposure to antibiotics designed to kill them, making the medicine ineffective.

Causes of antibiotic resistance:

  • Excessive use of antibiotics.
  • Inaccurate use of antibiotics (e.g., prescribing them for viral infections such as colds, sore throats, and fever).
  • Not completing the full course or not taking antibiotics according to the prescribed schedule.

Danger: Leaves individuals vulnerable to severe, untreatable bacterial infections ("superbugs").

Experiment 1.3 — Action of Antibiotics on Bacteria. The higher the concentration of antibiotic, the lower the growth of bacteria. The area of the clear region (zone of inhibition) increases as the concentration of penicillin increases. The control is a filter paper disc soaked in distilled water (0% antibiotic).

Historical fact. Sir Alexander Fleming discovered the first antibiotic from the fungus Penicillium sp.

Methods of Treating Infectious Diseases

Infectious diseases, causative pathogens and appropriate treatments.
Infectious Disease Causative Pathogen Pathogen Group Treatment Class Example Medicine
Pneumonia Streptococcus pneumoniae Bacterium Antibiotic Penicillin
Athlete's foot Trichophyton rubrum Fungus Antifungal Clotrimazole
Shingles Varicella-zoster Virus Antiviral Acyclovir

Try to Answer First

Answer in your mind, then press "Check Answer".

1

Why is an autoclave more effective at sterilising equipment than boiling water?

Answer: An autoclave reaches temperatures above \(130\text{ }^\circ\text{C}\) under high pressure, which can destroy both microorganisms and their heat-resistant spores, whereas boiling water only reaches \(100\text{ }^\circ\text{C}\) and cannot kill bacterial spores.
2

Can liquid chlorine or bleach be used to clean a cut on human skin? Explain why.

Answer: No. Liquid chlorine and bleach are disinfectants meant only for non-living objects; they are toxic and harsh, causing tissue irritation and damage to skin or open wounds.
3

What class of medicine should a doctor prescribe to a patient suffering from shingles, and why?

Answer: An antiviral (such as acyclovir), because shingles is caused by the Varicella-zoster virus, and viral infections do not respond to antibiotics or antifungals.

Common Mistakes

  • !Taking antibiotics for viral illnesses. Assuming antibiotics cure the common flu, cold, or viral sore throat. Antibiotics only kill bacteria.
  • !Confusing antiseptics and disinfectants. Stating that both can be used interchangeably on open cuts and furniture. Disinfectants are restricted to non-living objects.
  • !Stopping antibiotics prematurely. Halting an antibiotic regimen once symptoms improve rather than finishing the full prescribed course, which allows partially resistant bacteria to survive and multiply.
  • !Assuming boiling water achieves complete sterilisation. Boiling kills vegetative bacteria but fails to destroy bacterial endospores.

Concept Misunderstandings

Misconception

Antibiotic resistance means the human body has become immune to the antibiotic.

Correct Concept

It is the bacterium itself that undergoes changes and develops resistance to the medicine, not the human patient's body.

Misconception

Antiseptics and disinfectants contain the exact same chemical concentrations.

Correct Concept

Disinfectants have higher toxicity and stronger chemical formulations suitable only for inanimate surfaces; antiseptics are specifically formulated to be non-damaging to living human tissues.

Summary

  • Aseptic techniques: Procedures designed to prevent infection by stopping the spread of pathogens (sterilisation, boiling, antiseptics, disinfectants, radiation).
  • Sterilisation: Kills all microorganisms and their spores using autoclaves (\(>130\text{ }^\circ\text{C}\)), high pressure, micron filters (\(0.1\text{ }\mu\text{m} - 10\text{ }\mu\text{m}\)), UV rays, or soap.
  • Antiseptics vs Disinfectants: Antiseptics (e.g., povidone, acriflavine) are applied on living skin/wounds; disinfectants (e.g., bleach, liquid chlorine) are used on non-living objects.
  • Antibiotics: Treat bacterial infections only. Misuse causes antibiotic resistance. Higher concentrations result in wider zones of inhibition (clear regions).
  • Targeted Treatments: Pneumonia (Streptococcus pneumoniae) → Antibiotic (Penicillin); Athlete's foot (Trichophyton rubrum) → Antifungal (Clotrimazole); Shingles (Varicella-zoster) → Antiviral (Acyclovir).

Short Activity

A. Objective Quiz

1 Which of the following methods can destroy both microorganisms and their dormant spores?

2 A patient is diagnosed with athlete's foot caused by the fungus Trichophyton rubrum. Which medication is appropriate for treatment?

B. Fill in the Blanks

3 A temperature above \(130\text{ }^\circ\text{C}\) in an can kill microorganisms and their spores.

 

4 Antibiotic resistance happens when an antibiotic loses its ability to kill .

 

C. Drag and Drop: Match the Condition to Its Treatment

Drag each condition or application to its corresponding treatment substance or aseptic method. On a phone, tap an answer first, then tap a matching box. Tap the Answer Choices area to return a selected item.

Condition or Application
Pneumonia
Shingles
Human skin wound
Hospital operating theatre
Method or Treatment
1 Treated with the antibiotic penicillin
2 Treated with the antiviral acyclovir
3 Cleaned using antiseptics such as acriflavine
4 Disinfected using ultraviolet radiation

C. Match the Condition to Its Treatment

Write the correct condition or application next to each method or treatment.

Method or Treatment Condition or Application
1. Treated with the antibiotic penicillin  
2. Treated with the antiviral acyclovir  
3. Cleaned using antiseptics such as acriflavine  
4. Disinfected using ultraviolet radiation  

Answer choices: Pneumonia • Shingles • Human skin wound • Hospital operating theatre

Keywords

Pathogen Aseptic technique Sterilisation Autoclave Antiseptic Disinfectant Antibiotic Antibiotic resistance Antifungal Antiviral
The views expressed in the notes here are those of the contributor and don’t necessarily represent the views of Pandai.

Prevention and Treatment of Diseases Caused by Microorganisms

SCIENCE • Form 5 • Chapter 1: Microorganisms

1.3 Prevention and Treatment of Diseases Caused by Microorganisms

Harmful microorganisms that cause diseases are called pathogens. To manage infectious diseases, healthcare relies on two approaches: preventing infection before it occurs and treating diseases after infection.

Learning Objectives

  • Define aseptic techniques and identify the five main aseptic techniques.
  • Explain the process and methods of sterilisation (heat, chemical substances, radiation, high pressure, filter).
  • Compare and contrast the use of boiling, antiseptics, disinfectants, and radiation.
  • Describe the purpose of antibiotics, the causes and dangers of antibiotic resistance, and the relationship between antibiotic concentration and bacterial growth.
  • Identify the pathogens that cause pneumonia, athlete's foot, and shingles, and state the appropriate treatment for each disease.

Summary of Aseptic Techniques and Disease Treatments

Preventive techniques stop pathogens before infection; targeted medicines treat the pathogen after infection.

A diagram comparing prevention and treatment. Prevention shows living tissue matched to antiseptics and non-living surfaces matched to disinfectants. Treatment shows bacterium matched to antibiotic, fungus matched to antifungal, and virus matched to antiviral. PREVENTION TREATMENT Living tissue Antiseptics acriflavine, povidone, 70% IPA Safe for skin and wounds Non-living surfaces Disinfectants bleach, hydrogen peroxide, liquid chlorine Not suitable for skin or wounds Bacterium Antibiotic e.g. penicillin Treats bacterial infections Fungus Antifungal e.g. clotrimazole Treats fungal infections Virus Antiviral e.g. acyclovir Treats viral infections

Short Explanation

What is an aseptic technique?

Aseptic technique is a healthcare procedure carried out to prevent infections caused by pathogens or to remove existing pathogens.

Controlling infectious diseases requires two complementary strategies: prevention and treatment. Aseptic techniques help prevent or eliminate pathogens in line with the phrase "prevention is better than cure". When infections occur, specific medicines such as antibiotics, antifungals, and antivirals are used to treat them based on the causative pathogen.

Five main aseptic techniques. Sterilisation, boiling, use of antiseptics, use of disinfectants, and use of radiation.

Methods of Sterilisation

Sterilisation is the process of killing or eliminating microorganisms from an object or a particular surrounding.

Methods of sterilisation and examples.
Method Example
Heat Autoclave — temperatures above \(130\text{ }^\circ\text{C}\) kill microorganisms and their spores.
Chemical substances Soap.
Radiation Ultraviolet (UV) rays.
High pressure Pressure cooker.
Filter Micron filter — used to filter fine particles and microorganisms measuring \(0.1\text{ }\mu\text{m} - 10\text{ }\mu\text{m}\) from liquids or water.

Boiling

Boiling water at a temperature of \(100\text{ }^\circ\text{C}\) is used to kill vegetative microorganisms on everyday objects such as milk bottles, injection needles, and dental equipment. Boiling does not destroy bacterial spores.

Antiseptics vs Disinfectants

Comparison between antiseptics and disinfectants.
Feature Antiseptic Disinfectant
Application Site Applied directly on living human skin or wounds. Applied on non-living objects (e.g., bed sheets, toilets, swimming pools).
Purpose Prevents pathogenic infections. Kills microorganisms, especially pathogens, on surfaces.
Suitability for Skin Safe for skin and wounds. Not suitable for skin or wounds (can cause tissue damage).
Examples Acriflavine (yellow medicine), povidone, 70% isopropyl alcohol (IPA). Bleach, hydrogen peroxide, liquid chlorine.
Action Acriflavine and povidone kill microorganisms; proflavine blocks/prevents microbial growth; 70% IPA acts as an antiseptic and sterilising agent. Destroys pathogens on inert surfaces.

Radiation

Ionising radiation includes ultraviolet (UV) rays, X-rays, and gamma rays. These rays penetrate microbial cells and destroy them. Ultraviolet rays from UV lamps are used to disinfect operating theatres.

Antibiotics and Antibiotic Resistance

Antibiotic is a medicine used specifically to treat infections caused by bacteria. Antibiotics are not effective against viral infections such as the common cold, cough, or flu.

Antibiotic resistance occurs when bacteria develop the ability to survive exposure to antibiotics designed to kill them, making the medicine ineffective.

Causes of antibiotic resistance:

  • Excessive use of antibiotics.
  • Inaccurate use of antibiotics (e.g., prescribing them for viral infections such as colds, sore throats, and fever).
  • Not completing the full course or not taking antibiotics according to the prescribed schedule.

Danger: Leaves individuals vulnerable to severe, untreatable bacterial infections ("superbugs").

Experiment 1.3 — Action of Antibiotics on Bacteria. The higher the concentration of antibiotic, the lower the growth of bacteria. The area of the clear region (zone of inhibition) increases as the concentration of penicillin increases. The control is a filter paper disc soaked in distilled water (0% antibiotic).

Historical fact. Sir Alexander Fleming discovered the first antibiotic from the fungus Penicillium sp.

Methods of Treating Infectious Diseases

Infectious diseases, causative pathogens and appropriate treatments.
Infectious Disease Causative Pathogen Pathogen Group Treatment Class Example Medicine
Pneumonia Streptococcus pneumoniae Bacterium Antibiotic Penicillin
Athlete's foot Trichophyton rubrum Fungus Antifungal Clotrimazole
Shingles Varicella-zoster Virus Antiviral Acyclovir

Try to Answer First

Answer in your mind, then press "Check Answer".

1

Why is an autoclave more effective at sterilising equipment than boiling water?

Answer: An autoclave reaches temperatures above \(130\text{ }^\circ\text{C}\) under high pressure, which can destroy both microorganisms and their heat-resistant spores, whereas boiling water only reaches \(100\text{ }^\circ\text{C}\) and cannot kill bacterial spores.
2

Can liquid chlorine or bleach be used to clean a cut on human skin? Explain why.

Answer: No. Liquid chlorine and bleach are disinfectants meant only for non-living objects; they are toxic and harsh, causing tissue irritation and damage to skin or open wounds.
3

What class of medicine should a doctor prescribe to a patient suffering from shingles, and why?

Answer: An antiviral (such as acyclovir), because shingles is caused by the Varicella-zoster virus, and viral infections do not respond to antibiotics or antifungals.

Common Mistakes

  • !Taking antibiotics for viral illnesses. Assuming antibiotics cure the common flu, cold, or viral sore throat. Antibiotics only kill bacteria.
  • !Confusing antiseptics and disinfectants. Stating that both can be used interchangeably on open cuts and furniture. Disinfectants are restricted to non-living objects.
  • !Stopping antibiotics prematurely. Halting an antibiotic regimen once symptoms improve rather than finishing the full prescribed course, which allows partially resistant bacteria to survive and multiply.
  • !Assuming boiling water achieves complete sterilisation. Boiling kills vegetative bacteria but fails to destroy bacterial endospores.

Concept Misunderstandings

Misconception

Antibiotic resistance means the human body has become immune to the antibiotic.

Correct Concept

It is the bacterium itself that undergoes changes and develops resistance to the medicine, not the human patient's body.

Misconception

Antiseptics and disinfectants contain the exact same chemical concentrations.

Correct Concept

Disinfectants have higher toxicity and stronger chemical formulations suitable only for inanimate surfaces; antiseptics are specifically formulated to be non-damaging to living human tissues.

Summary

  • Aseptic techniques: Procedures designed to prevent infection by stopping the spread of pathogens (sterilisation, boiling, antiseptics, disinfectants, radiation).
  • Sterilisation: Kills all microorganisms and their spores using autoclaves (\(>130\text{ }^\circ\text{C}\)), high pressure, micron filters (\(0.1\text{ }\mu\text{m} - 10\text{ }\mu\text{m}\)), UV rays, or soap.
  • Antiseptics vs Disinfectants: Antiseptics (e.g., povidone, acriflavine) are applied on living skin/wounds; disinfectants (e.g., bleach, liquid chlorine) are used on non-living objects.
  • Antibiotics: Treat bacterial infections only. Misuse causes antibiotic resistance. Higher concentrations result in wider zones of inhibition (clear regions).
  • Targeted Treatments: Pneumonia (Streptococcus pneumoniae) → Antibiotic (Penicillin); Athlete's foot (Trichophyton rubrum) → Antifungal (Clotrimazole); Shingles (Varicella-zoster) → Antiviral (Acyclovir).

Short Activity

A. Objective Quiz

1 Which of the following methods can destroy both microorganisms and their dormant spores?

2 A patient is diagnosed with athlete's foot caused by the fungus Trichophyton rubrum. Which medication is appropriate for treatment?

B. Fill in the Blanks

3 A temperature above \(130\text{ }^\circ\text{C}\) in an can kill microorganisms and their spores.

 

4 Antibiotic resistance happens when an antibiotic loses its ability to kill .

 

C. Drag and Drop: Match the Condition to Its Treatment

Drag each condition or application to its corresponding treatment substance or aseptic method. On a phone, tap an answer first, then tap a matching box. Tap the Answer Choices area to return a selected item.

Condition or Application
Pneumonia
Shingles
Human skin wound
Hospital operating theatre
Method or Treatment
1 Treated with the antibiotic penicillin
2 Treated with the antiviral acyclovir
3 Cleaned using antiseptics such as acriflavine
4 Disinfected using ultraviolet radiation

C. Match the Condition to Its Treatment

Write the correct condition or application next to each method or treatment.

Method or Treatment Condition or Application
1. Treated with the antibiotic penicillin  
2. Treated with the antiviral acyclovir  
3. Cleaned using antiseptics such as acriflavine  
4. Disinfected using ultraviolet radiation  

Answer choices: Pneumonia • Shingles • Human skin wound • Hospital operating theatre

Keywords

Pathogen Aseptic technique Sterilisation Autoclave Antiseptic Disinfectant Antibiotic Antibiotic resistance Antifungal Antiviral
The views expressed in the notes here are those of the contributor and don’t necessarily represent the views of Pandai.
Chapter : Microorganisms
Topic : Prevention and treatment of diseases caused by microorganisms
Form 5 Science
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