Nearly everyone has taken antibiotics for treating bacterial infection, but not many of us actually know how antibiotics kill bacteria. This article highlights on the various types of antibiotics and how they work.
Antibiotics are therapeutic medications, formulated for inhibiting growth of bacteria or killing them directly without causing harmful effects to the body. They are included in the list of antimicrobial drugs and medications, along with others such as antifungal and antiviral medications. As the name indicates, antibiotics exclusively target bacterial strains; whereas antifungal and antiviral medicines work against fungi and virus respectively. But, actually how do antibiotics kill bacteria? Varied types of antibiotics work differently and kill selective bacterial strains, which we will discuss in this article.
The first antibiotic ‘penicillin’ was discovered in 1928 from the fungal species Penicillium by the Nobel laureate Sir Alexander Flemming. However, the word ‘antibiotic’ was suggested in 1942 by Selman Abraham Waksman, an American biochemist and microbiologist, while performing research work in organic substances. He was also the eminent scientist, who discovered streptomycin and several other antibiotics. Further advancements in medicinal chemistry led to extraction of antibiotic compounds from living microorganisms as well as synthetic substances.
Coming to the subject of our discussion, ‘how do antibiotics fight infection by killing bacteria’, the mode of treating bacterial infection varies according to the particular class of antibiotic taken for the purpose. Based on the medicine formulation and way of fighting against bacteria, there are two types of antibiotics – bacteriostatic and bactericide. Detailed information on how do these two antibiotics kill bacteria is explained below:
As the name signifies, bacteriostatic antibiotics inhibit bacterial growth, instead of killing them directly. Since the pathogenic bacteria are suppressed, the body’s immune system can easily combat infection. The working mechanism of bacteriostatic antibiotics is to disturb the protein synthesis in disease-causing bacteria. Examples of popularly prescribed bacteriostatic antibiotics are spectinomycin (treat gonorrhea), tetracyclines (generally used for infection), chloramphenicol (for any type of bacterial infection) and macrolides (effective against gram positive bacteria).
In contrary to bacteriostatic type, bactericide (or bacteriocide) antibiotics contain active compounds that directly kill bacteria. They target the outer cell wall, inner cell membrane and essential chemical pathways of the bacterial strains, which are crucial for their survival inside the body. Common examples of bactericidal antibiotics are penicillin (attacks the outer cell wall), polymyxins (target cell membrane) and quinolones (interfere enzyme pathways). Some bacteriocidal substances are used as disinfectants, sterilizers and antiseptics.
Target Specific Antibiotics
Some are effective for fighting against many bacteria, while others are used for killing a specific group. Thus, besides classification according to the mode of action, antibiotics are also classified based on their target specificity. Considering this, the two groups of antibiotics are broad-spectrum type and narrow-spectrum type. The former is effective for killing different types of pathogenic bacteria (e.g. tetracycline, tigecycline and chloramphenicol). Whereas narrow-spectrum antibiotics (e.g. oxazolidinones and glycylcyclines) are recommended for treating a specific class of disease-causing bacteria.
What Causes Antibiotic Resistance?
Prolonged use of antibiotics or their overuse leads to antibiotic resistance. The outcome is development of antibiotic resistant bacteria. Many a times, we end up administering antibiotics for any outbreak of infection, irrespective of which organism is responsible for the symptoms. The most common example is taking antibiotics for viral infection. In such cases, the ingested antibiotics kill useful bacteria and lead to reduction in the probiotic bacterial population.
As a consequence of antibiotic overuse, other invading microbes like virus and fungi get an easy access to the body and cause infection. Let’s take an example; people who have been through antibiotic treatment are at an increased risk of candidiasis or yeast infection. An effective way to avoid such an incidence is to administer antibiotics only under the supervision of a trusted doctor.