List of Common Antibiotics & Types

What are Antibiotics?

Antibiotics are a group of medicine that helps to fight infections. They target bacterial species and effectively treat infections. Antibiotics play a major role in modern medicine.

In the olden days, before modern medicine came into existence, dyes, molds and heavy metals were used to treat infections. However, these olden days practices could not benefit for a long time, and so antibiotics were used to treat various infections.

According to the World Health Organisation (WHO), antibiotics are compounds that are used to treat and prevent bacterial infections.

The antibiotics function by inhibiting cell reproduction, destroying bacterial cells, or altering a necessary cellular function within the cell.

The antibiotics work with two terms— minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The minimum inhibitory concentration is the lowest concentration of the antibiotic that inhibits the growth of bacteria at 24 hours.

Minimum bacteriocidal concentration is the concentration of the antibiotic that can reduce the bacterial density by 1000 folds at 24 hours.

However, antibiotics are not used to treat certain ear infections in children, sore throat and chest infections. When a person is affected by a viral infection, a strong class of antibiotics will be prescribed by the doctor to treat such infections.

Types of Antibiotics

Some of the common types of antibiotics are listed below

Penicillins

Penicillins are used to treat various infections, and it is a beta-lactam antibiotic. It is widely used against bacterial species like gram-positive cocci, gram-positive rods and gram-negative cocci.

Certain gram-negative bacteria have become resistant to penicillin. So, a combination of penicillin and gentamicin or streptomycin is used. The later generations of penicillin have become broad-spectrum and are effective against gram-negative bacteria.

Tetracyclines

Tetracyclines are broad-spectrum antibiotics that are used to treat various bacterial infections. These antibiotics inhibit protein synthesis. When there is no synthesis of protein, it can lead to irregular cell functioning, and the cells will not be able to replicate, which can lead to cell death.

This process of growth inhibition is called bacteriostatic. However, the bacterial species have developed a resistance to tetracyclines, according to data published in an NCBI article.

The administration of tetracyclines is commonly done through the oral route. However, there are intramuscular and intravenous routes of administration.

Tetracyclines are used both for humans and animals. The common uses of tetracyclines are listed below.

• To prevent malarial infection.
• For the treatment of anthrax.
• For the treatment of eye infections, gastrointestinal tract infections, respiratory tract infections and certain skin infections.
• Tetracyclines are used as a growth promoter in animals.

Cephalosporins

Cephalosporins are beta-lactam antibiotics that are used to treat gram-positive and gram-negative bacterial infections. Cephalosporins are used to treat skin infections, meningitis and other bacterial-resistant infections.

According to NCBI data, the first-generation cephalosporins are said to be effective against most gram-positive cocci bacteria and some gram-negative bacterial species like E.Coli.

Second-generation cephalosporins are effective against influenza and Bacteroides species. Third-generation cephalosporins are less effective in most gram-positive bacteria but are effective against Enterobacteriaceae, Neisseria spp., and H. influenza. The fourth-generation cephalosporins are effective against the same species as the third-generation cephalosporins.

Quinolones

Quinolones are a group of bacteriocidal antibiotics that directly kills bacterial cells. These antibiotics act on the type II topoisomerases, type IV topoisomerases and DNA gyrase, which inhibits their function and converts them into toxic enzymes.

These toxic enzymes produce permanent double-stranded breaks in the chromosomes of the bacterial cells. The DNA topoisomerase is essential for normal physiological functions of the bacteria like DNA replication, recombination and transcription.

The DNA gyrase and topoisomerase IV create a break in the bacterial chromosome, which leads to the fragmentation of the bacterial chromosome. The DNA strands break, and this break will reduce the cell’s ability to repair the damaged DNA, which leads to cell death.

Quinolones are mostly administered through intravenous and oral routes. Oral administration is rapidly absorbed in the gastrointestinal tract and also has high bioavailability. However, quinolones are widely distributed throughout the body. They find it difficult to penetrate into the cerebrospinal fluid.

Lincomycins

Lincomycins is an antibiotic that is used to treat severe bacterial infections. These antibiotics are prescribed when the penicillins do not work effectively. Lincomycins can be used alone or in combination with other antibiotics depending on the degree of infection.

Lincomycins are also called as Lincocin, and they belong to the class of drugs named Lincosamide. Lincomycins are derived from Streptomyces lincolnensis through the process of natural fermentation.

These antibiotics are active against the gram-positive cocci and bacilli and gram-negative cocci. Lincomycins should be taken with only a doctor’s prescription as they can produce hypersensitive reactions.

Macrolides

Macrolides are compounds that contain lactone rings with attached deoxy sugars. These macrolides have antifungal or antibiotic properties and play a major role in pharmaceutical antimicrobial therapy.

Some classes of macrolides like azithromycin, erythromycin and clarithromycin are common antibiotics used to treat sinusitis, pneumonia, tonsillitis and pharyngitis.

According to NCBI data, the Food and Drug Administration (FDA) has approved the use of macrolides for uncomplicated skin infections in paediatric patients.

Macrolides class of drugs are usually used to treat sexually transmitted diseases like chlamydial and gonococcal infections.

Recent research published in NCBI stated that macrolides maintenance therapy has shown to reduce the severity of the symptoms and improve the quality of life.

Sulfonamides

Sulfonamides are synthetic medicine that contains a chemical group called sulfonamide and also called as sulfa drugs.

Sulfonamides exhibit bacteriostatic activity and also interfere with the synthesis of folic acid in bacteria. Folic acid is essential for the formation of nucleic acids. Sulfonamides interfere in the process of DNA and RNA formation, which inhibits cell formation and replication.

The human body absorbs folic acid through the diet. However, bacteria should synthesise their own folic acid, and this class of antibiotics can interfere in the process and kills the bacteria.

Glycopeptides

Glycopeptides are a type of antibiotic that is used to treat gram-positive bacterial and enterococcal infections. These infections may be resistant to other classes of antibiotics, so glyco peptides may be prescribed.

Glycopeptides inhibit the synthesis of the cell wall of the bacteria by attaching themselves to the cell wall. The bacterial cells will not be able to multiply as the glyco peptides possess a bacteriocidal capacity.

Glycopeptides are effective against gram-positive bacteria. However, gram-negative bacteria can be resistant to these antibiotics. Glycopeptides are administered intravenously in cases of severe infection, and oral administration is effective when the infection is local, like digestive tract infections.  

Aminoglycosides

Aminoglycosides are broad-spectrum antibiotics derived from actinomycetes. These antibiotics are available as naturally derived compounds or as semi-synthetic antibiotics. Aminoglycosides were the first antibiotics that were introduced for routine use in clinical sectors.

In the early days, aminoglycosides are widely used as first-line agents in antimicrobial chemotherapy. However, aminoglycosides were later replaced with cephalosporins, fluoroquinolones and carbapenems.

Aminoglycosides, in combination with other antibiotics, are said to improve the efficacy of the class and dosing of the antibiotics.

Aminoglycosides are antibiotics that inhibit protein synthesis and are isolated from Streptomyces griseus. The antibiotic is active against gram-positive and gram-negative organisms.

Carbapenems

Carbapenems are antibiotics that are broad-spectrum and have good efficacy against gram-positive and gram-negative bacteria. These antibiotics are used when patients are severely ill and are suspected of having been infected with antibiotic-resistant bacteria.

However, these life-saving drugs are at risk due to multidrug-resistant pathogens. Carbapenems enter the gram-positive bacteria through the outer-membrane proteins called porins.

As a result, the peptidoglycan weakens, which causes the cells to burst due to osmotic pressure. Carbapenems are used in combination with other antimicrobials to treat life-threatening infections.

List of common Antibiotics

Antibiotics play a major role in our life. We might have taken antibiotics more than once in our life to treat certain infections. Antibiotics are used in various treatments like throat pain, ear infections and urinary tract infections. Some of the common antibiotics that are used regularly are listed below.

Phenoxymethylpenicillin

Phenoxymethylpenicillin is a class of penicillin antibiotics to treat bacterial infections like chest pain, ear infections and skin infections.  

It is commonly administered to patients affected with sickle cell disease to avoid frequent infections. It is also administered for patients who have undergone splenectomy—a condition of spleen removal due to major injury or other causes.

Phenoxymethylpenicillin is not an over-the-counter drug and is only available with a prescription. These antibiotics come in tablet and liquid forms.

The antibiotics are administered to patients four times a day, and they will start to feel good in a few days.  

Diarrhoea and tiredness are the common side effects of these antibiotics. However, they will resolve on their own.

Dicloxacillin

Dicloxacillin is a class of antibiotics used to treat bacterial infections that belongs to the second-generation penicillin antibiotics. These antibiotics are used to treat infections caused by penicillinase-resistant staphylococci.  

Dicloxacillin usually comes in tablet form, which can be taken through the mouth. The length and dosage of the tablet will depend on the infection type and severity.  

Like penicillin antibiotics, dicloxacillin binds to the bacterial enzymes that are responsible for synthesising the bacterial wall. However, these antibiotics will not work for cold, flu and other viral infections.

Amoxicillin works like penicillin

These combination antibiotics are used to treat urinary tract infections, lung infections, and ear and sinus infections that are caused by bacterial species.

Amoxicillin works like penicillin and stops the growth of bacteria, which eventually leads to death. When clavulanic acid is used in combination with amoxicillin, it prevents the bacteria from destroying the amoxicillin.

These combination antibiotics are commonly available as tablets, chewable tablets, suspension liquid taken by mouth and long-acting tablets.

The long-lasting tablet should be swallowed and must not be chewed or crushed. The other doses that are in tablet form can be swallowed with water.

Ampicillin

Ampicillin is used in the management and treatment of bacterial infections, which belongs to penicillin antibiotics. Ampicillin is effective against bacterial species like E. coli, S. pneumoniae, H. influenzae and S. aureus.

According to NCBI data, ampicillin has an effective minimum inhibitory concentration against E. coli, Staphylococcus aureus, Streptococcus pneumoniae and Hemophilus influenzae with a minimum inhibitory concentration of 4 mg/L, 0.6-1 mg/L, 0.03-0.06 and 0.25 mg/L respectively.

The mode of action takes place in two steps. In the first step, the drug will bind to membrane-bound penicillin-binding proteins and inactivates the function.

In the second stage, these bound receptors will cause certain physiological effects, which break the peptidoglycan cell wall in a hypotonic environment which leads to death.

Ampicillin can be administered orally, intravenously and intramuscularly. To avoid bacterial resistance to the drug, FDA has recommended prescribing the drug when the particular bacterial infection is confirmed.

Nafcillin

Nafcillin belongs to the second generation of penicillin antibiotics. Nafcillin is used to treat staphylococci infections that are moderate to severe. These antibiotics are effective against penicillinase-producing bacteria.

The recommended dose for an adult is 1 or 2 grams per vial, depending on the severity of the infection. In some cases, there can certainly be side effects like nausea, skin rashes, diarrhoea, headache and fatigue.

Oxacillin

Oxacillin is a penicillin antibiotic that treats bacterial infections. They are commonly used to treat various staphylococcus infections.

These antibiotics bind to the proteins in the bacterial cell wall and inhibit the last stage of bacterial wall synthesis, which leads to cell lysis by an enzyme called autolysins.

Oxacillin is commonly used for certain illnesses like meningitis, pneumonia, joint pain and skin or soft tissue infections.

Penicillin V

Penicillin V is the enhanced antibiotic of the original penicillin. Penicillin V is commonly used to treat ear infections, scarlet fever and mouth and throat infections.

Penicillin V is available in tablet and liquid form, which can be administered orally. The penicillin V antibiotic should be taken till the course is completed, even though you have recovered or are feeling better.  

Penicillin G

Penicillin G is used to treat gram-positive bacteria. It can be administered intramuscularly and intravenously since these classes of antibiotics have poor oral absorption rates.

Penicillin G can sometimes cause side effects like nausea, vomiting, pain and swelling, diarrhoea, muscle or joint pain and stomach pain.

Taking Antibiotics

Antibiotics are commonly taken to treat bacterial infections. Antibiotics should not be self-prescribed, and the course should be completed even if you feel better.

There are no broad-spectrum antibiotics that can handle a sure wide range of bacterial infections. There are specific antibiotics for a specific type of infection. Antibiotics are not effective against any viral infections.

When to use antibiotics?

Antibiotics work on bacterial infections like  

• Strep throat,
• Urinary tract infection and
• Whooping cough.

So, antibiotics can be effective against such health illnesses and treat them.

When not to use antibiotics?

Antibiotics do not work for viral infections. So, when you use such medications, the bacteria can become resistant to these drugs. When the bacterial species become resistant, they will no longer respond to such drugs.

These antibiotics can also cause side effects. So, it is recommended to consume antibiotics when a doctor prescribes them.

When to see a doctor?

Consult a doctor when your illness has not been cured even though you have taken the prescribed medicine. At the same time, do not force your doctor to prescribe you antibiotics.  

Flu infections are common during the monsoon seasons. There are chances of you contracting a highly infectious flu. So, if you contract any infection during these seasons, consult your doctor immediately.  

Conclusion

Antibiotics are used to treat bacterial infections and should not be taken on their own without a doctor’s prescription. There are chances of these bacterial species becoming resistant to these antibiotics.

Sometimes antibiotics can cause adverse side effects. These side effects can indicate that there is an abuse of antibiotics. These antibiotics are an effective tool to control and inhibit the growth of highly infectious bacteria. So, use these medicines wisely.

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