Infections have many origins, such as pneumonia (bacterial), the common cold (viral), athlete’s foot (fungal), and giardiasis (parasitic), to name just a few. The body prevents and fights these infections through its complex immune system. When infections are too strong for the immune system to overcome them, physicians typically prescribe medications. This article will focus on one type of these medications, antibiotics (also called anti-bacterials). We’ll look at how they work, their limitations, how to use them safely, and the newest advances in these important infection-fighting medicines.

Bacteria are microorganisms, meaning that they are life forms. The word ‘antibiotic’ breaks down into: ‘anti’ (against) and ‘biotic’ (life). Antibiotics act to inhibit the growth of, or kill, microorganisms, preventing their spread and multiplication. The first – and still most common – antibiotics come from fungi (e.g., penicillin) and specifically fight bacteria. Before the development of antibiotics for widespread use, about 70 years ago, there was a high mortality rate from bacterial infections, such as tuberculosis, pneumonia, and sexually transmitted contagions.

Today, many forms of antibiotics exist to treat several different types of infections, including parasitic infections and some fungal infections. However, antibiotics do not work on viruses because viruses are not living organisms and so are ‘not alive’. Unlike living organisms with their own cells, viruses are segments of DNA (or RNA) that inject themselves into living cells, forcing those cells to do the work of reproducing more of the viral DNA.

This is why your physician will not prescribe an antibiotic for the common cold or flu. When we are sick, we often don’t know the full nature of the infection that is attacking our bodies. We just feel bad. This can be confusing because, for example, while a cold virus attacks our body, our immune system is working extra hard and we become vulnerable to developing other types of infections, such as pneumonia or strep throat, which are bacterial infections and usually treated with antibiotics.


Scientists have found evidence that humans may have used antibiotic agents against disease as far back as 2,000 years ago. In 1928, Dr. Alexander Fleming returned to his lab following a vacation to find that a type of fungus called penicillium had contaminated one of the petri dishes containing a bacterium he had been studying (staphylococci). The bacteria all around the fungal mould had died. Fleming then analyzed the mould and found that it produced a chemical substance that killed bacteria, which he named penicillin. Several other scientists ran with that initial discovery, refining the process and applying it to medicine as a mass-produced medication. There are now dozens of types of penicillins as well as numerous other chemical classes of antibiotics.


Bacteria: Friends and Foes

Bacteria are single-celled microorganisms (microbes). The human body hosts trillions of microbes, with an estimated 10,000 bacterial species living in and on the surface of our bodies. No two people – not even twins – have identical combinations of bacteria (microbiomes), which begin to develop at birth, particularly if we were born through the microbe-rich birth canal.

For a long time, scientists focussed only on infection-causing (pathogenic) bacteria and thought that non-pathogenic bacteria were, at best, unimportant. However, microbial cells outnumber our human cells by about ten to one and scientists are now beginning to understand that they play a significant role in our wellness, especially within the immune and digestive systems. In digestion, for example, there are bacteria that feed on foods that we cannot digest with our human cells alone. The waste products of these bacteria are nutrients for our human systems. Some of these non-pathogenic bacteria also engage in constant battle with pathogenic bacteria, helping to maintain a healthy microbiome, keeping the numbers of ‘bad’ bacteria to a minimal level.

Probiotics refer to live microorganisms thought to have beneficial effects, and popular knowledge of this has led to a surge in probiotic use; however, other bacteria have harmful effects, especially when they overpopulate specific areas of our bodies. Infection with pathogenic bacteria can happen following an injury, when common external bacteria enter the human body through the bloodstream, or by contamination with unfriendly microorganisms that produce toxic by-products, as in many cases of food poisoning.


How Antibiotics Work

Antibiotics work by disrupting bacterial cells in several ways, such as inhibiting the bacterium’s ability to build its cell wall, blocking its reproduction, or interfering with its ability to store and use energy. Antibiotics do not usually affect human cells, which is why we can ingest them safely for use as a medicine. However, like all medicines, some people may react or have side-effects from antibiotics as well. Some antibiotics attack a wide range of bacteria (broad-spectrum antibiotics), while researchers develop others to only attack specific pathogenic strains (narrow-spectrum antibiotics). There are antibiotics that work only against bacteria that need oxygen (aerobic) and others that work against bacteria that live in the absence of oxygen (anaerobic).

When you swallow an antibiotic pill or liquid, it enters your digestive tract and is absorbed into the blood stream just as nutrients are from food. From there, it circulates throughout the body, soon reaching its target area, where pathogenic bacteria are causing an infection. In some situations, such as when an infection is especially severe, physicians might administer antibiotics via injection intravenously, directly into the bloodstream. With certain skin infections, the most effective way to get the antibiotic to the pathogenic organisms quickly is to apply it directly to the infection as a topical cream or ointment. This limits the body’s exposure to the drug to a small area when there is no need for it to be circulating in the bloodstream.

Your physician chooses a particular antibiotic and its route of administration based on a number of factors, such as the exact type and extent of infection. It is sometimes necessary to have a specimen analyzed at the laboratory to determine the exact species and strain of bacteria causing the infection. Your physician might also prescribe antibiotics before bowel surgery or another medical procedure that comes with a high risk of bacterial infection, which is a preventative (prophylactic) use of antibiotics.

One of the common side-effects from taking antibiotics is loose bowel movements (diarrhea), as the antibiotic disrupts the normal, healthy bacteria in your gut that are keeping you regular. Your physician might recommend the use of probiotics following antibiotic treatment to help your body re-populate healthy strains of bacteria. If you find blood or mucus in your stool, or experience severe abdominal pain or cramping, you should follow up with your physician immediately to assess if there may be a secondary infection, such as C. difficile. (See page 11.) When one antibiotic fails to eradicate an infection, your physician may have to move on to less conventional drugs, which might be more expensive or associated with more serious side-effects. Physicians reserve these antibiotics for use in specific situations and circumstances only, to avoid the development of antibiotic resistance.


Antibiotic Resistance and Superbugs

Antibiotics alter the course of life-threatening infections, decreasing mortality and loss of organs or limbs. However, each time a person uses an antibiotic for treatment, the chances of developing resistant bacterial strains increase, and these might eventually develop into superbugs. The term ‘superbug’ refers to any microorganisms that have become resistant to treatment with common anti-infective agents that were previously effective against them. Although superbugs have been more of an issue in hospitals, there are increasing outbreaks within community environments. The best thing you can do is to take your antibiotic medication exactly as your physician has instructed – the correct dose and for the complete duration of the prescription, even if you are feeling better midway through treatment. This is very important. Stopping your antibiotic treatment midway through the course, or taking only a portion of the doses, even though symptoms of the infection have disappeared, dramatically increases the risk of developing resistance by bacteria.

Scientists have determined the crucial concentration of a particular antibiotic in the body to kill an infection, but if you don’t reach that level of antibiotic circulating in the body, then this can create an environment in which only the weakest pathogenic cells die while the stronger, more resistant, bacteria remain, multiply, and mutate (become resistant). As the mutant bacteria passes on to others, it could become increasingly difficult to find an antibiotic to work against it. This can also happen if you do not take the entire course of medication as prescribed, where low levels of the pathogenic bacteria still exist, allowing the bacteria to either re-infect you and/or become resistant. Researchers are continually developing new antibiotic medications to fight these emerging superbugs. See page 11 for information on a new narrow-spectrum antibiotic, Dificid™, which targets C. difficile bacteria specifically, while preserving healthy strains of bacteria. In addition to this evolving research, patients play an extremely important role in preventing the development of new or stronger superbugs, simply by taking their medication as prescribed.


Key Messages

  • Most antibiotics treat bacterial infections, and some antibiotics treat certain parasitic or fungal infections. Antibiotics NEVER work against viral infections. (There are anti-viral medications and/or vaccines available for some types of viral infections.)
  • Always take antibiotics exactly as your physician prescribes and finish the full course of medication (unless you are having a serious adverse reaction and check with your physician). Never take someone else’s prescribed antibiotic or an antibiotic your physician prescribed to you for a previous ailment that you didn’t finish.
  • Superbugs are an increasing problem, especially in hospital environments, and everyone has a role to play in decreasing their development.


This Versus That

Antibiotics (e.g. penicillin) are selective antimicrobial drugs that only attack bacterial microbes, killing them or blocking their reproduction. Disinfectants (e.g., bleach) are non-selective antimicrobial agents that will attack many types of microorganisms, which is why they cannot be used in our bodies and can damage human cells.
Bactericidal agents kill bacteria by either interfering with the replication of the bacterium’s cell wall and/or contents. Bacteriostatic agentsstop bacteria from multiplying or interfere with protein synthesis but do not necessarily kill the bacterium.
Broad-spectrum antibiotics (e.g., penicillins, aminoglycosides, cephalosporins, sulfonamides) work against a wide range of bacterial infections. Narrow-spectrum antibiotics (e.g., macrolides, vancomycin, fidaxomicin) are only effective against a few types of pathogenic bacteria.
Aerobic bacterial infections, such as the bacterium that causes strep throat, survives in areas of the body exposed to oxygen. Penicillins and other types of antibiotics fight these infections. Anaerobic bacterial infections (e.g., gangrene, tetanus, and botulism) involve deep tissues or organs where there is no oxygen, such as the gastrointestinal tract or beneath significant wounds. Specialized antibiotics such as metronidazole or clindamycin, among numerous others, are effective against them.


New Non-Toxic Disinfectant

A group of researchers from Université de Saint-Boniface (USB) in Manitoba has proven the effectiveness of a disinfectant that could revolutionize the fight against superbugs in the hospital system.

[i] The chemical disinfectants hospitals currently use work by controlling or preventing the spread of bacterial spores and those that attach to surfaces are difficult to destroy. This new disinfectant, Akwaton, is able to destroy Bacillus subtilis spores (suspended in water and attached to stainless steel or glass surfaces) at very dilute concentrations, after treatment for just 90-seconds. It is also effective against strains of Methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli). This poses a significant breakthrough because most other disinfectants require a high concentration in order to be as effective, which is often harmful to humans.

Alan Low, BSc (Pharm), PharmD, RPh, ACPR, FCSHP, CCD
First published in the Inside Tract® newsletter issue 184 – 2012
1. Canadian Health Reference Guide. New Weapon against C. difficile: significant scientific breakthrough at Université de Saint-Boniface. Available at Accessed 2012-09-30.