Antibiotics 101: How It Works, Types, Benefits & More

Medically reviewed by Nikhil Kapoor, BS Pharm
Fact checked by Victor Cheung

What is Antibiotics?

Antibiotic refers to any substance that inhibits the growth and replication of a bacterium or kills it outright. Antibiotics are a type of antimicrobial designed to target bacterial infections within (or on) the body. This characteristic makes antibiotics slightly different from the other main kinds of antimicrobials widely used today, such as:

  • Antiseptics (skin disinfectant) – used to sterilise surfaces of living tissue when the risk of infection is high, such as during surgery.
  • Disinfectants – non-selective antimicrobials that kill a wide range of microorganisms including bacteria. They are used on non-living surfaces, for example in hospitals as well as at home in the kitchen and bathroom.

The fact is bacteria are not the only microbes that can be harmful to us. Fungi and viruses can also be a danger to humans. They are targeted by antifungals and antivirals. Antibiotics on the other hand, only refer specifically to substances that target bacteria. Antibiotics, antifungals, antivirals and chemicals such as antiseptics or anything that inhibits or kills microbial cells are collectively known as antimicrobial.

Almost all antibiotics used today are produced in laboratories, but they are often based on compounds found in nature by science experts. Some microbes, for example, produce substances to specifically kill other nearby bacteria in order to gain an advantage when competing for food, water or other limited resources. Other microbes only produce antibiotics in the laboratory.

Antibiotic Production

The production of antibiotics involves an industrial process of fermentation. The source microorganism is grown in large containers (100,000 – 150,000 liters or more) filled with a liquid growth medium. Microorganisms used in fermentation are often genetically modified from its original form to yield the maximum amounts of antibiotics.

Throughout the process, oxygen concentration, temperature, pH, and nutrient levels must be kept at an optimal level while closely monitored and adjusted whenever necessary. As antibiotics are secondary metabolites, the population size must be controlled very carefully to ensure that maximum yield is obtained before the cells die. Once the process is complete, the antibiotic must be extracted and purified to a crystalline product. This is simpler to achieve if the antibiotic is soluble in organic solvent or else, it must first be removed by ion exchange, adsorption, or chemical precipitation.

Antibiotics Function

The principle governing the use of antibiotics is to ensure that the patient receives just the right one. The target bacterium should be sensitive to antibiotics and it needs to be of a high enough concentration to be effective without causing side effects for a sufficient length of time to ensure that the infection is totally eradicated.

Antibiotics vary in their range of action. Some are highly specific. Others, such as the tetracyclines, act against a broad spectrum of different bacteria. These are particularly useful in fighting against mixed infections and in treating infections when time does not permit sensitivity tests. While some antibiotics, such as the semisynthetic penicillins and the quinolones can be taken orally, others must be given by intramuscular or intravenous injection.

Types of antibiotics

Although there are hundreds of different types of antibiotics, most of them can be classified into six groups.

  1. Penicillins (ie: penicillin, flucloxacillin, amoxicillin, co-amoxiclav and phenoxymethylpenicillin) – widely used to treat a variety of infections such as skin infections, chest infections and urinary tract infections
  2. Cephalosporins (ie: cephalexin) – used to treat a wide range of infections including more serious infections, such as septicaemia and meningitis
  3. Aminoglycosides (ie: gentamicin and tobramycin) – specifically used in hospitals only to treat very serious illnesses such as septicaemia. This is due to their serious side effects such as hearing loss and kidney damage. They are usually given by injection but may also be given as drops for some ear or eye infections
  4. Tetracyclines (ie: tetracycline, doxycycline and lymecycline) – are commonly used to treat acne and a skin condition called rosacea but also effective for treatment of a wide range of infections
  5. Macrolides (ie: azithromycin, erythromycin and clarithromycin) – are effective in lung and chest infections treatment as well as an alternative for people with a penicillin allergy, or to treat penicillin-resistant strains of bacteria
  6. Fluoroquinolones (ie: ciprofloxacin and levofloxacin) – are broad-spectrum antibiotics that were once used to treat a wide range of infections, especially respiratory and urinary tract infections. But these antibiotics are no longer used routinely due to their risk of serious side effects

Other antibiotics include chloramphenicol (used for eye and ear infections), trimethoprim (used for urinary tract infections) and fusidic acid (used for skin and eye infections), and nitrofurantoin.

Why Antibiotics Cause Side Effects

Human body is naturally filled with millions of bacteria. Most of them are harmless. In fact, many are actually beneficial or necessary for health and general processes, for instance, the stomach bacteria that help us digest food properly.

Although antibiotics can kill bacteria effectively, they cannot always differentiate between good bacteria and bad bacteria. This means they may damage bacteria that we actually need. Our body will be unable to operate properly while allowing the foreign bacteria to take over our organ systems.

Common Side Effects of Antibiotics

Some of the most common side effects of antibiotics include:

Upset stomach – Many antibiotics such as penicillins, cephalosporins, macrolides, and fluoroquinolone antibiotics can cause an upset stomach or other general gastrointestinal problems. Symptoms include nausea, vomiting, diarrhea and stomach cramps

Photosensitivity – Certain antibiotics, like tetracycline, can make us more sensitive to light. This can make the skin more susceptible to sunburn and the eyes may become more sensitive to natural light.

Fever – Fever as a side effect is common for many medications, not just antibiotics. Fever can also happen as part of an allergic reaction. They are more common with sulfonamides, cephalexin, beta lactams, and minocycline, but can also happen with any antibiotic.

Tooth discoloration – Antibiotics such as doxycycline and tetracycline may cause permanent tooth staining. This is generally more common in children younger than eight years old. Women who take antibiotics while pregnant may also stain the teeth of their developing child. It is best for them to avoid these types of antibiotics.

Fungal infections – Due to their ability to kill off lots of healthy, protective bacteria in our body, antibiotics can cause certain fungal infections such as thrush. Thrush often appears as white, painful patches in the mouth and on the tongue. Antibiotics can also cause vaginal yeast infections with symptoms such as itchiness, pain, and general discomfort along with a fluid discharge. Do seek advice from a doctor when experiencing these symptoms.

Interactions with other medications – Certain types of antibiotics that may affect the effectiveness of other medications you are taking. For example, the antibiotic rifampin can affect the effectiveness of the birth control pill

Serious Antibiotics Side Effects

The side effects of antibiotics are usually not very serious and should subside once you finish the course. In some rare cases, the side-effects become more serious depending on your reaction to them and your personal health.

Just like with any other medication, there are possible risks of allergic reactions with antibiotics. Allergic reactions to antibiotics can be relatively mild, but some can be very serious and require immediate medical attention.

Our body will react almost immediately after taking antibiotics that we are allergic to. Most allergic reactions manifest in the form of hives, trouble breathing as well as swelling in the tongue and throat. If you have a severe allergic reaction to an antibiotic, known as ‘anaphylaxis’ your life could be in danger. If you develop these symptoms you should seek medical advice immediately.

Another type of allergic reaction that can occur with antibiotics is Stevens-Johnson syndrome. This serious illness will affect your mucus membranes and skin. It is most common with sulfamethoxazole and beta-lactam antibiotics. Stevens-Johnson syndrome starts out with flu-like symptoms, including sore throat and fever and can progress to a painful rash that quickly spreads and causes blisters. This may be followed by the top layer of your skin shedding.

Other symptoms of Stevens-Johnson syndrome include skin pain, hives, coughing, swelling in the tongue or face as well as pain in the throat and mouth. Stop taking the antibiotic immediately and seek medical advice straight away if you are experiencing any of these symptoms

In rare cases, antibiotics can cause changes to our blood. For instance, some antibiotics can reduce the number of white cells in the blood (leukopenia). This will lead to a weakened immune system and a higher chance of infections. Some antibiotics may cause low levels of platelets in your blood (thrombocytopenia). Platelets are needed for you body to form clots if you cut yourself. Not having enough platelets can slow down your blood clotting and cause problems with bruising and bleeding.

Some antibiotic medications, usually fluoroquinolone antibiotics such as ciprofloxacin, may also irritate or inflame the tendons. Tendons are the thick tissues that connect your muscles to your bones. Continued irritation can potentially lead to tendonitis or a ruptured tendon. This is more common in people who:

  • Suffer from existing kidney failure
  • Have undergone a lung, heart, or kidney transplant
  • Experienced past problems in their tendons
  • Age of 60 years and older
  • Take steroids

In the rarest cases, antibiotics can cause low blood pressure, irregular heartbeat, and other cardiovascular problems. These side-effects have been linked to erythromycin and some types of fluoroquinolone antibiotics.

What’s important to consider when taking antibiotics?

Antibiotics should be taken as prescribed by the doctor. Even after the symptoms of the illness subside, not all of the germs might have been killed. Remaining bacteria may cause the illness to start up again.

Do not keep, consume or give away to other people any of the remaining tablets. Leftover medication can be disposed of in the normal garbage or dropped off at some pharmacies although they are not obligated to accept opened medicine. Never dispose of medication by pouring it down the drain or flushing it down the toilet as it can be bad for the environment and contributes to bacterial resistance.

Medications can only work properly if they are used correctly. It is very important to know the following things when taking antibiotics:

Can the tablets be crushed into smaller pieces to make them easier to swallow?

Doing this can stop some medications from working properly.

What food can you take antibiotics with?

Antibiotics are best taken with water. Taking them together with alcohol, fruit juices and dairy products such as milk, butter, yogurt or cheese can affect the absorption process. Wait for about three hours before eating or drinking any dairy products. Grapefruit juice and dietary supplements containing minerals like calcium may also dampen the effect of antibiotics.

When should you take antibiotics?

Some antibiotics are always meant to be taken at the same time of day, while others are meant to be taken before, with or after a meal. If you are supposed to take the medicine three times a day, for example, it usually needs to be taken at set times so that the effect is spread out evenly over the course of the day. You could remember the regular times of 6 am, 2 pm and 10 pm for an antibiotic that needs to be taken every eight hours, for instance.

Can you take antibiotics together with other medications?

It is important to tell your doctor if you take other medications too as antibiotics are able to interact with other medications for instance, blood thinners and antacids. Some antibiotics can make birth control pills less effective.

You can find detailed information on the use of a specific antibiotic in the package insert. If you are not sure about what is important to consider when taking the antibiotic, you can ask your doctor or pharmacist.

Antibiotic Resistance

There is just one particular issue that has plagued antibiotic therapy from right from the beginning is the resistance that bacteria can develop to the drugs. Even though an antibiotic may kill virtually all the bacteria causing a disease in a patient, a few bacteria that are genetically less vulnerable to the effects of the drug may still survive. These bacterias would reproduce or transfer their resistance to others of their species through gene exchange processes. With their more vulnerable competitors killed and reduced in numbers by antibiotics, these resistant strains proliferate. As a result, antibiotics that are customarily used for treatment of bacterial infections in humans are no longer effective. The indiscriminate and inexact use of antibiotics encourages the spread of such bacterial resistance.

Researchers are continually working to discover new antibiotics as a means of overcoming antibiotic resistance. Some potentially effective compounds that have been discovered include certain bacterial toxins and antimicrobial peptides. Novel treatment strategies, such as combining synergistic antibiotics to boost the killing of bacteria, are also under investigation. It may be possible to introduce compounds into bacterial populations that effectively resensitize the bacteria to existing antibiotic drugs.

Potential side effects aside, the benefits of antibiotics far outweigh the risks. If you have symptoms of an infection and think you need antibiotics, you should go and talk to your doctor or simply get antibiotics online from a professionally trained and certified doctor. Alternatively, you can contact Homage today and they will help point you towards the right direction.

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