8 min readPathway sheet1-mark MCQ or assertion-reason on penicillin or resistance, a 2 or 3-mark question on the discovery of penicillin or why antibiotics must be used carefully

Antibiotics: production and judicious use

Antibiotics are chemicals made by microbes that kill or slow the growth of disease-causing microbes. Misuse breeds resistant bacteria, so use them only as prescribed.

AntibioticA chemical produced by some microbes that kills or retards the growth of other, disease-causing microbes

First antibioticPenicillin, from the mould Penicillium notatum, discovered by chance by Alexander Fleming

Nobel Prize 1945Alexander Fleming, Ernest Chain and Howard Florey

Diseases now treatablePlague, whooping cough (kali khansi), diphtheria (gal ghotu), leprosy (kusht rog)

What 'antibiotic' means

Anti means 'against' and bio means 'life', so antibiotic means 'against life', meaning against the disease-causing microbes. For people, antibiotics are really 'pro life'. They are among the most significant discoveries of the twentieth century and have made deadly diseases such as plague, whooping cough, diphtheria and leprosy treatable.

The discovery of penicillin

1
Alexander Fleming was working with Staphylococci bacteria.
2★
He saw a mould growing in one of his unwashed culture plates; around the mould, Staphylococci could not grow.
3
He found that this was due to a chemical made by the mould, and named it penicillin after the mould Penicillium notatum.
4
Ernest Chain and Howard Florey later established its full potential as an effective antibiotic.
5
Penicillin was widely used to treat soldiers wounded in World War II. Fleming, Chain and Florey won the Nobel Prize in 1945. Other antibiotics were later purified from other microbes.

★ key step

How antibiotics are produced (extra: your textbook does not give these steps)

A high-yielding strain of the microbe (a mould such as Penicillium, or a bacterium) is selected.
It is grown on a large scale in fermentors under sterile, controlled conditions of temperature, pH, aeration and nutrients.
The antibiotic released into the medium is separated, purified and tested before it is made into tablets, capsules or injections.

When do antibiotics help? (extra, not in your textbook)

Bacterial infectionsAntibiotics work against bacteria, for example in typhoid or bacterial pneumonia, when a doctor prescribes them.

Viral infectionsAntibiotics do not work against viruses, so they do not cure the common cold, flu or dengue. Taking them for these only helps resistance spread.

Judicious use of antibiotics (extra: your textbook does not list these points)

Take antibiotics only when prescribed by a doctor; never buy them over the counter for self-medication.
Complete the full course, even if you feel better early. Stopping halfway lets the tougher bacteria survive and multiply.
Do not use leftover antibiotics or share them with others.
Overuse acts as natural selection: resistant bacteria survive and spread in months or years, making infections harder to treat.
Prevent infections in the first place with hygiene, safe water and vaccination.

In real life

Antibiotic-resistant infections are a growing worry in Indian hospitals. Asking the chemist for an antibiotic for a cold or viral fever does not help you and makes future infections harder to treat for everyone.

Exam angle

2 marks: “Who discovered penicillin, and how? Name the organism that produces it.” Alexander Fleming noticed that Staphylococci could not grow around a mould in an unwashed culture plate; the mould made a chemical he named penicillin. Organism: Penicillium notatum.

3 marks: “What are antibiotics? Why should they be used judiciously?” Chemicals made by some microbes that kill or retard the growth of disease-causing microbes. Misuse (self-medication, incomplete course, use for viral infections) selects resistant bacteria, making antibiotics ineffective; so use only as prescribed and complete the course.

Remember it

Fleming's Plate, Penicillium's Fate: a dirty dish gave the first antibiotic. Finish the course, or the bugs grow worse.