An antibiotic is any substance that harms or kills a microorganism. The most important thing to know about antibiotics is what they will not do – and that is antibiotics do not harm viruses. The overwhelming majority of antibiotics are manufactured from substances of natural origin, isolated from bacteria and fungi (molds). There are a few antibiotics that are completely synthetic – made from scratch in the laboratory – and a few that are a hybrid of natural and synthetic components.

When first discovered in the early part of the twentieth century, antibiotics were touted as a miracle cure – and they were. Once commercial methods to mass-produce penicillin for human use were developed in 1941, bacterial infections that were fatal before the turn of the century were tamed to mere inconveniences.

Sadly, too much of a good thing has reduced this miracle power. The misuse, over-prescription, and abuse of antibiotics have allowed antibiotic-resistant strains of bacteria to develop and once again threaten health and life. According to US News Online, even back in the 1940s, scientists knew that the more an antibiotic is used, the quicker it becomes useless.

When antibiotics were first introduced, infections caused by bacteria were quickly and easily treated. However, even though most bacteria exposed to an antibiotic are killed, some bacteria may be able to resist treatment, mutate, and gain strength. The fittest (and most resistant) survive and pass these survival traits on to their offspring. With continued use of the antibiotic, the resistant bugs proliferate.

Today, only one or two antibiotics, or antibacterial agents remain that have any effect in the fight against some of these dangerous bacteria. Hospitals, community homes, and other places where vulnerable groups of people dwell, face the challenges of dealing with these resistant bugs. Interestingly, bacteria that have become resistant to one antibiotic also seem to find it easier to build resistance to others.


Global Concerns

In Canada there is strict control over issuance of antibiotics, but in some other countries of the world antibiotics are available without a prescription and this can lead to improper usage that has an effect on the rest of the world. Because most people in poor countries have limited access to doctors and hospitals, self-medication with antibiotics purchased from unlicensed vendors is extremely common. The vendors’ drugs, which are often counterfeited or expired, frequently contain some degree of active antibiotic, but not enough to have a full therapeutic effect.

In developing countries, even licensed hospitals may inadvertently distribute sub-potent drugs. Surplus drugs donated to under-funded healthcare facilities by well-meaning aid groups often turn out to have lost most of their effectiveness. These drugs are then distributed without potency testing. For example, about half of the drugs donated during the height of the Kosovo refugee crisis were found to be unusable.

These sub-potent levels of drugs can be the fastest route to the development of antibiotic resistance, since they leave only the most strongly resistant bacteria alive to proliferate without competition from more susceptible bacteria.

Helping to curb resistance in poorer countries would be not only altruistic, but also prudent. It is a global problem, because the prevalence of air travel means that resistant bacteria developed in one country can easily take up residence in another.


Hope for the Future

In the early years, new antibiotics were developed faster than bacteria developed resistance to them, but the bacteria have quickly caught up. In the 1950s and 60s, many new classes of antibiotics were discovered but during the 1980s and 90s, scientists only managed to make improvements within classes.

However, as reported in mid-September 2000, at an infectious diseases meeting in Toronto, a new class of antibiotic is currently being explored. Frontline antibiotics currently of choice are called macrolides (e.g. erythromycin) that work by gumming up the bacteria’s ability to make new proteins. Some bacteria elude the medicine by quickly pumping it out before it does any harm and thus become “resistant” to the antibiotic. Bacteria are also growing resistant to backup antibiotics known as quinolones.

The new antibiotic class, ketolides, that are derived from macrolides are sufficiently chemically different so the bacteria resistant to macrolides are not able to spit them out in the same way. Two companies producing different varieties of this new class of antibiotic – not yet available on the market – are Aventis Pharmaceuticals (Ketek) and Abbott Pharmaceuticals (ABT-773). Although about 2,500 patients have been treated with these medications, additional early stage clinical trials (human testing) are being done to measure the safety of the ketolides.

An advantage of ketolides is that treatment duration seems to be shorter, lasting only five days, rather than the current 7 – 10 days for macrolides. The assumption is that bacteria may be less likely to develop resistance during this shorter use duration.

There is also another new group of drugs. Quinupristin/dalfopristin is the first parenteral streptogramin antibacterial agent and is a semisynthetic pristinamycin. It is an IV product on the market in the US and may be available in Canada soon. These were made to treat the multi-drug resistant gram-positive infections occurring in hospital or resulting from overuse of antibiotics.

Another group of antibiotics that are in the process of soon being released out on to the market is the group called the oxazolidinones of which the first agent that is soon to be out is linezolid. This drug is aimed at treating multi-drug resistant gram-positive bacteria and is an oral agent. Linezolid is already available in the US, released in April of this year under the name Zyvox®.

In addition, a new form of antibiotic that disrupts cells is being studied. Two drugs in this category are called daptomycin and Y333328. Both of these are still in the early stages of development and are being studied in resistant type bacteria. However, being a drug that disrupts bacterial cell membranes, it may also have adverse effects on human cell membranes. These drugs are being studied in the injectable form for now.



While bacteria continue to adapt to our attacks against them, scientists are striving to stay one step ahead. The outcome of the race depends on a number of factors.

To do your part in helping to reduce the number of bacteria becoming resistant to treatment, when taking a prescribed antibiotic, it is very important to follow all instructions from your physician and pharmacist, to the letter. While at the proper dosage most antibiotics will not hurt us, there can sometimes be harmful side effects – so any adverse reactions should be immediately reported to your doctor.

Without over-reacting, we need to be careful in our use of antibiotics. The two most common misuse and abuse of antibiotics are:

Physicians prescribing inappropriate and indiscriminate antibiotic use, including prescribing antibiotics for viral infections, and

Patients not taking antibiotics as instructed, particularly not finishing the entire prescribed dosage. It is important to note that patients are likely to feel better after a few days of antibiotic treatment as bacteria count is reduced, but the full duration of treatment is required to fully eradicate the infection and be sure there are not any active bacteria left behind.

Thanks to Dr. Alan Low, BSc(Pharm) PharmD and Adil Saleh, BSc(Pharm), R,PEBC for their input.
First published in the Inside Tract® newsletter issue 122 – November/December 2000