Antibiotics, Antivirals and Resistance
- Junessa Masaya
- 6 days ago
- 4 min read
HSC Biology | Study Notes
Antibiotics, antivirals and resistance are a key part of NSW Biology Stage 6, Module 7, Infectious Disease. This topic matters because Module 7 specifically requires students to investigate and assess the effectiveness of pharmaceuticals used to control infectious disease, including antibiotics and antivirals. HSC materials also repeatedly link antibiotic use to the growing problem of resistance.
In this lesson
how antibiotics are used to treat bacterial infections
how antivirals are used to treat viral infections
what resistance means
why resistance is a major problem
what responsible use of these drugs involves
What are pharmaceuticals in infectious disease?
In Module 7, pharmaceuticals are drugs used as treatment strategies to help control infectious disease.
The syllabus specifically names:
antibiotics
antivirals
These are not the same thing, and one of the most important exam points is knowing which type of pathogen each one is used against.
Bacterial treatment
Antibiotics are used to treat bacterial infections.
What antibiotics do
Antibiotics work by interfering with important bacterial processes, which can:
inhibit bacterial growth
kill bacteria
reduce the spread of bacterial infection in the body
A 2020 HSC marking guideline states that antibiotics can be used to treat bacterial infections because they can inhibit bacterial growth.
HSC example
A 2021 HSC question describes streptomycin as an antibiotic that interferes with bacterial ribosomes. The question links this to prevention of polypeptide production in bacteria.
Important point
Antibiotics act against bacteria, not viruses.
Viral treatment
Antivirals are used to treat viral infections.
What antivirals do
Antivirals are designed to interfere with stages of viral infection or viral replication.
At syllabus level, the key idea is that:
antibiotics are for bacteria
antivirals are for viruses
The Module 7 syllabus specifically includes assessing the effectiveness of antivirals as treatment strategies for infectious disease.
HSC example
A 2023 HSC question presents a pharmaceutical tested on a viral infection, showing that antivirals are considered separately from antibiotics in treatment questions.
Antibiotics and antivirals compared
Treatment | Main target | Main idea |
Antibiotics | Bacteria | Inhibit bacterial growth or kill bacteria |
Antivirals | Viruses | Interfere with viral infection or replication |
Resistance
Resistance means a pathogen is no longer affected as effectively by a drug that once worked.
Antibiotic resistance
In Module 7, the main resistance idea students need is antibiotic resistance in bacteria.
A 2020 HSC marking guideline states that antibiotic resistance in bacteria is becoming increasingly common and is reducing the effectiveness of many antibiotics.
Why resistance matters
If bacteria become resistant:
treatment becomes less effective
infections may last longer
disease control becomes harder
HSC example
A 2021 HSC marking guideline explains that using antibiotics may eliminate disease quickly, but longer-term use may induce resistance in the bacteria, making the strategy less effective over time.
How resistance affects treatment
Resistance makes it harder to control infectious disease because:
the usual drug may no longer work
another treatment may be needed
disease may spread more easily if treatment fails
This is why antibiotics are powerful but must be used carefully.
Responsible use
Responsible use means using the correct pharmaceutical in the correct situation and not relying on it unnecessarily.
What this involves
At this level, responsible use includes:
using antibiotics for bacterial disease, not viral disease
selecting treatment based on the pathogen involved
recognising that overuse or poor use can increase resistance
combining pharmaceuticals with other control strategies where appropriate
HSC-style support for this idea
A 2019 HSC question on antibiotic discs shows that bacterial treatment should be based on which antibiotic is actually effective against the cultured bacteria.
A 2021 HSC marking guideline also contrasts quick antibiotic treatment with longer-term hygiene strategies, showing that pharmaceuticals are not the only control method and should be used as part of wider disease management.
Why this topic matters in Module 7
This topic is important because Module 7 is about:
treatment
prevention
control of infectious disease
To answer exam questions well, students need to distinguish clearly between:
bacterial disease and viral disease
antibiotics and antivirals
effective treatment and reduced effectiveness due to resistance
Worked example
Exam-style question
Explain why antibiotics are not useful for treating viral infections.
Worked answer
Antibiotics are used to treat bacterial infections because they interfere with bacterial processes such as growth. Viral infections require antivirals instead, because viruses are different pathogens and are not controlled by antibiotics. Using antibiotics when the disease is viral does not target the cause of the infection.
Why this works
This answer:
distinguishes bacteria from viruses
links antibiotics to bacterial treatment
explains why the treatment would be inappropriate
Common mistakes
Saying antibiotics treat all infectious diseases.
Mixing up antibiotics and antivirals.
Forgetting that resistance reduces drug effectiveness.
Writing about resistance without linking it to bacteria or treatment failure.
Treating pharmaceuticals as the only way to control infectious disease.
Quick quiz
What type of pathogen do antibiotics treat?
What type of pathogen do antivirals treat?
What is antibiotic resistance?
Why is resistance a problem in infectious disease control?
What does responsible use of antibiotics involve?
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