What is an antibiotic?
Antibiotics are powerful medications that treat certain infections, and can save lives when used properly. They either stop bacteria from reproducing or destroy them.
Before bacteria can multiply and cause symptoms, the immune system can typically kill them. White blood cells (WBCs) attack harmful bacteria — even if symptoms occur, the immune system can usually cope and fend off the infection.
However, sometimes the number of harmful bacteria is excessive, and the immune system cannot clear them all. Antibiotics are useful in this scenario.
The first antibiotic was penicillin. Penicillin-based antibiotics, such as amoxicillin are still available to treat a variety of infections and have been in use for many years.
Back to the question what is an antibiotic – and how do you use them?’
Which antibiotic should you have?
This is a difficult question to answer. Why?
- The antibiotic that a doctor chooses depends on what they think is wrong with you
- It also depends on how ill you are. For example, if you are very ill, you may need to go into hospital for intravenous (IV) antibiotics, some of which are only available in that form
- Different antibiotics are favoured in different countries
- Which antibiotic was effective last time, if you have had a similar infection before.
Here are some antibiotics that may be needed for different illnesses.
Examples of antibiotics – and what they are used for
1. Aminoglycosides – e.g. Gentamicin
Tends to only be used in hospital to treat very serious illnesses such as sepsis, as they can cause serious side effects, including hearing loss and kidney damage. They are usually given by injection, but may be given as drops for some ear or eye infections.
2. Carbapenems – e.g. Ertapenem and Meropenem
They are a subclass of antibiotics called beta-lactam antibiotics (antibiotics that have a chemical structure called a beta-lactam ring).
Carbapenems are broad-spectrum antibiotics. That is, they are effective against many types of bacteria, including bacteria that are resistant to many other antibiotics. Carbapenems must be given by injection.
3. Cephalosporins – e.g. Cephalexin
They are used to treat a wide range of infections, but some are also effective for treating more serious infections, such as sepsis and meningitis.
4. Fluoroquinolones – e.g. Ciprofloxacin (‘Cipro’)
They are broad-spectrum antibiotics that were once used to treat a wide range of infections, especially respiratory and urinary tract infections. These antibiotics are no longer used routinely because of the risk of serious side effects.
5. Lincosamides – e.g. Clindamycin
They are used to treat bacterial infections such as pelvic inflammatory disease, abdominal infections, abscesses and acne.
Lincosamides have this structure
6. Macrolides – e.g. Erythromycin
Can be particularly useful for treating lung infections, or as an alternative for people with a penicillin allergy, or to treat penicillin-resistant strains of bacteria.
7. Penicillins – e.g. Benzylpenicillin, amoxicillin, flucloxacillin
Skin, chest and urinary tract infections.
Amoxicillin/clavulanic acid (beta-lactams with increased activity)
This is a form of penicillin, used for sinus infections, urine infections, skin infections, joint infections and some dental infections. It is also given before some surgical operations, to prevent an infection from developing.
8. Rifamycins – e.g. Rifampin (rifampicin)
They are antibiotics that work by suppressing the bacteria’s production of genetic material. As a result, the bacteria die. They are used in combination with other antibiotics to treat tuberculosis and infections related to tuberculosis.
9. Sulphonamides – e.g. ‘Septrin’ (Sulfamethoxazole, in combination with trimethoprim)
They are a class of antibiotics that are effective against many infections. Some sulphonamides are applied directly to the skin (topically) to treat burns and skin, vaginal, and eye infections. They work by preventing bacteria from producing a form of folic acid they need to grow and multiply.
10. Tetracyclines – e.g. Tetracycline and Doxycycline
They can be used to treat a wide range of infections, but are commonly used to treat acne and a skin condition called rosacea.
How do you use antibiotics?
- Take antibiotics only if you need them.
- Take them exactly as your doctor tells you, and they have been prescribed.
- Do not share your antibiotics with others, or take antibiotics prescribed for someone else.
- Do not save them for later (another infection in the future).
- Discard tablets correctly.
Medications can only work properly if they are used correctly.
What are the side effects of antibiotics?
Anytime antibiotics are used, they can cause side effects. Common side effects range from minor to very severe health problems and can include:
- Rash
- Nausea, vomiting and diarrhoea
- Yeast infections (like Candida that can cause vagina thrush)
- C. diff infection
- Antibiotic-resistant infections.
More serious side effects
- C. diff infection, which causes diarrhoea that can lead to severe colon damage and death
- Severe and life-threatening allergic reactions
Call your doctor if you develop any side effects while taking your antibiotic.
Antibiotic resistance
Bacteria, like all living organisms, evolve (change) over time in response to environmental challenges. Because of the widespread use and misuse of antibiotics (when antibiotics are not taken as prescribed), bacteria are constantly exposed to these drugs. Although many bacteria die when exposed to antibiotics, if antibiotics are not taken appropriately, some bacteria survive and develop resistance to the drugs’ effects.
For example, 50 years ago, Staphylococcus aureus (a common cause of skin infections) was very sensitive to penicillin. But over time, strains of this bacteria developed an enzyme able to break down penicillin, making the drug ineffective.
Researchers responded by developing a form of penicillin that the enzyme could not break down, but after a few years, the bacteria adapted and became resistant to this modified penicillin. Other bacteria have also developed resistance to antibiotics.
Summary
We have described what is an antibiotic – and what they are for. We hope you understand them better now.
Other resources
10 most common antibiotics
3 most common antibiotics
Antibiotics: 10 questions and answers
How to use antibiotics: 10 do’s and don’ts
