amoxicillin & clavulanic acid
Amoxicillin & clavulanic acid is a combination antibiotic.
Antibiotics are used to treat bacterial infections, and using combination therapy can help to increase the effectiveness of the medicine as well as prevent the development of antibiotic resistance.
Bacteria
Recall that bacteria are microscopic, single-celled organisms. They are prokaryotic. Some bacteria are helpful while and others cause disease.
They have genetic material (DNA) inside the cytoplasm of the cell. Many have cell walls or capsules that protect them from harsh environments like stomach acid. Ribosomes read DNA and use this to make proteins. Proteins are used in growth and replication.
Examples:
Yersinia pestis - causes Black Plague
Escherichia coli - causes diarrhoea
Mycobacterium tuberculosis - causes tuberculosis
Amoxicillin
Amoxicillin is a β-lactam antibiotic. This means that it contains a β-lactam ring (shown in pink in the diagram to the left) in its chemical structure. This ring works against bacteria by inhibiting (preventing) bacteria from making cell walls. Without a cell wall, bacteria cannot survive.
Penicillin was the first β-lactam antibiotic discovered. It was discovered by accident, by Alexander Fleming in 1928. It has saved countless lives since this time.
However, over time, some bacteria have evolved to be able to fight back.
A number of bacteria can now make an enzyme (a protein that catalyses chemical reactions inside the body) called β-lactamase. This enzyme breads down the β-lactam ring in antibiotics through a reaction called hydrolysis. This destroys the antibiotic activity of these drugs. You may have heard of this - it is known as antibiotic resistance.
Clavulanic Acid
Clavulanic acid is able to bind to the β-lactamase enzyme like glue, and stop it from working. Medicines that stop β-lactamase from working are called β-lactamase inhibitors. To combat antibiotic resistance, amoxicillin is taken in combination with the β-lactamase inhibitor, clavulanic acid. Clavulanic acid lets amoxicillin get on with its job of inhibiting bacterial cell walls.
Can you spot the β-lactam ring in clavulanic acid?
Clavulanic acid is also a naturally occurring molecule. It is made by the bacteria Streptomyces clavuligerus. Inter-bacterial and fungal-bacterial warfare have been productive places for scientists to identify and isolate helpful medicines in the past.
Can you think of why amoxicillin might not harm human cells?
Amoxicillin & clavulanic acid combinations are particularly helpful against bacteria that secrete β-lactamase.
Bacteria that have evolved to secrete β-lactamase include:
Methicillin-resistant Staphylococcus aureus (MRSA) - causes skin infections, in particular at open wounds.
Salmonella - causes salmonellosis, an infection spread through the consumption of contaminated meat.
Escherichia coli (E. coli) - one of many possible causes food poisoning.
Did you know: many species of E. coli don't actually harm us. In fact, they are naturally found in your gut microbiome and are essential for your health!
Mycobacterium tuberculosis - causes tuberculosis.
