SYDNEY: It's official: misuse of some antibiotics breeds drug-resistant 'superbugs', according to European researchers.
Medical experts have long theorised that misuse of antibiotics could breed superbugs, but a study released today has finally provided concrete evidence. "All of us could see what was happening, but now we have proof," said Stephanie Dancer, a microbiologist at Southern General Hospital in Glasgow, Scotland.
Bacterial diseases that were once easy to treat, such as tuberculosis, gonorrhoea, typhus and pneumonia, are fast evolving into strains that outstrip science's ability to keep up. The new study, reported in the British journal The Lancet, demonstrated that the trend is accelerated when antibiotics are mismatched to the type of bacteria being targeted.
Strep throat and other respiratory infections are caused by strains of Streptoccocus bacteria, but other streptoccoci strains are normal, harmless components of the microbe community of the mouth and throat.
To test the effect of antibiotics on bacteria they are not designed to treat, Surbhi Malhotra-Kumar and a team of microbiologists from Belgium and the Netherlands gave a partial course of either clarithromycin and azithromycin - two antibiotics called macrolides commonly employed in treating respiratory infections like strep throat - to two randomly-selected groups of 74 healthy people.
None of the subjects had the conditions that the antibiotics had been designed to treat - only the normal, harmless strains were present for the antibiotics to act on. A separate 'control' group was given sugar pills to provide a yardstick for any changes observed, and the subjects did not know to which group they had been assigned.
According to the researchers, the results of the study were ironclad. Azithromycin swiftly created large numbers of bacteria that were resistant to macrolides, while clarithromycin encouraged the emergence of a highly resistant form. This form was not only more resistant to macrolides, it also showed greater resistance to three other antibiotics.
The study found that the antibiotics had an enduring effect on the streptococci bacteria - affecting them for more than 180 days. According to the team, the usually harmless bacteria became a potential reservoir of drug-resistant genes for pathogenic strains, as related bacteria can exchange DNA directly through a process called conjugation.
Penicillin is usually the weapon of choice for tackling streptococci when a strain threatens infection, but doctors often resort to macrolides if a patient is allergic to penicillin. The stakes could hardly be higher, said Dancer.
"It is an immense problem ... that is affecting every antimicrobial agent that [science] has been able to find," she said. "We are squandering a precious resource." She pointed the finger in particular at purchases of antibiotics over the counter and the Internet, and urged the launch of a public awareness campaign along the lines of "no drugs for bugs - unless needed."
