British physician Sir Alexander Fleming discovered in 1928 that bacteria did not grow in the presence of Penicillium mold. It took more than a decade, until the end of the Second World War, before penicillin emerged as the first antibiotic to be used widely.

Penicillin was soon followed by other antibiotics, opening up a whole new era of lifesaving medical treatments. Medical science not only used antibiotics to treat diseases, but also to unlock opportunities for surgical procedures that would be too risky without antibiotics to deal with the higher risk of infection. For example, organ transplants require suppression of the immune system but rely on antibiotics to fight off infections.

From 1945 until the late 1980s, new antimicrobial agents were developed faster than bacteria developed resistance. Through the 1950s and 1960s, new classes of antibiotics were developed. But in the '80s and '90s research produced no new classes, but rather improvement within classes.

By the end of the 20th century after only fifty years of use, some antibiotics were no longer able to vanquish some bacteria. There are strains of Staphylococcus aureus (the so-called "Staph" infection) and Pseudomonas aeruginosa, found so far only in Japan, that are resistant to all established antibacterial agents.

Highly virulent and increasingly antimicrobial-resistant pathogens such as Staph have become major sources of hospital-acquired infections. Seniors residences are another danger zone for antimicrobial-resistant infections, sometimes with fatal effects.

The first MRSA (methicillin-resistant Staphylococcus aureus) was reported in Ontario in 1981. Outbreaks have been reported since across the country.

Some bacterial infections are treatable only with Vancomycin the last antibiotic line of defence in the armoury of medical science.

While research continues and new therapies are discovered every year, all new drugs will eventually face the inevitable resistance that bacteria will acquire.