Doctors warn antibiotics overused

The era of antibiotics is only seven decades old. Yet the growth of bacteria resistant to these miracle drugs is escalating to a point that worries doctors. In Hong Kong, penicillin resistance in bacteria is as high as 80 per cent. In the United States, it’s 41 per cent.

In Canada, the resistance rate is 21 per cent according to Dr. Donald Low, the head of the microbiology departments at the University of Toronto and Mount Sinai Hospital.

Problem with us forever
He’s a member of the National Information Program on Antibiotics, a group of eight medical associations, supported by the Pfizer drug company. NIPA began a campaign in 1996 to educate the public and physicians about the danger of inappropriate use of antibiotics.

“This is a problem that’s going to be with us forever. It doesn’t matter if we come out with another new drug tomorrow. Unless we use these drugs appropriately, what wll do is accelerate the problem. If we use the drugs right, we could prolong the time before we see resistance and possibly even prevent it,” says Dr. Low.

The chairman for the NIPA program is Dr. Ronald Grossman, chief of medicine at the Credit Valley Hospital in Mississauga, Ontario. He says there are several reasons for the rapid increase in aggressive bacteria resistant to antibiotics.

Reasons for resistance
“First of all, there’s no doubt that antibiotics have been overused. Most surveys would suggest that about 50 per cent of prescribing is inappropriate. There are a number of different reasons for this,” he says.

  • These include a demand by patients for prescription drugs and doctors complying.

“Patients get acutely ill. And they believe that antibiotics are capable of fixing anything. And the vast majority of antibiotics are prescribed for viral illnesses, for which there are no benefits from antibiotics,” says Dr. Grossman.

“We physicians don’t have good rapid diagnostic testing to be able to differentiate a bacterial from a viral infection. So in many instances what happens is that because of uncertainty on the physician’s part, this leads to prescribing antibiotics.”

Next page: More reasons for resistance

More reasons for resistance
  • The overuse of antibiotics is compounded by inappropriate use.

“Many patients start taking their antibiotics, and the moment they start feeling better, they stop. And so they only partly treat an infection. And we know that if you underdose an infection, that sets up the situation for bacterial resistance to emerge,” says Dr. Grossman.

He says patients should finish off any prescription.

  • The other issue is storing the drug for future use.

“Patients use their unfinished prescriptions again when they feel sick-practising medicine without a license. Or worse, they share the antibiotic with somebody else in the family,” says Dr. Grossman.

He says this is a neat set up for the development of antibiotic resistance-“too many drugs chasing too few infections and patients not taking their drugs appropriately leads to trouble.”

Could affect anyone
He says as resistance rises in the population, anybody can be affected by these tough bacteria. Even people who’ve never used an antibiotic could be infected with a resistant strain.

“An example would be tuberculosis. If you were in an airplane and the person beside you was coming from Russia, where the prevalence of antibiotic resistant TB is quite high, and that person coughed in your face, you could get that antibiotic resistant strain of TB. You’re not protected,” says Dr. Grossman.

In the fight against antibiotic resistant bacteria, no country is an island, says Dr. Low.

“With international travel, there’s no question that the penicillin resistance emerged in North America in the 1980’s because of importation of strains from Spain and South Africa into the United States. Then it was amplified and got to the resistance stage.”

Dr. Low says more people coming into contact, through travel, in daycare, nursing homes and hospitals, allows for bacteria to spread more easily. In this exchange, there are always a few bacteria with the right genes to be immune to an antibiotic. These bacteria can then multiply, unchecked.

Next page: Most potent antibiotic

Most potent antibiotic
There are about 10 different classes of antibiotics, and within each class, a group of drugs. The penicillin class, for example, would include penicillin V, penicillin VK, ampicillin and amoxycillin, plus others.

One of the most potent antibiotics is vancomycin. It’s restricted for use against bacteria resistant to other antibiotics. These bacteria are most often found in hospitals.

Increasingly, amplification has led to cases where enterococci bacteria, commonly found in the human gut, are resistant to vancomycin.

“Our first VRE (vancomycin resistant enterococci) outbreak in Mount Sinai resulted from a patient coming back from a clinic in Cleveland who jumped the queue. He went down there for a procedure, got an infection, and came back here to get over his infection. By the time we detected what it was, it had been transmitted to six or seven other patients,” says Dr. Low.

Handling resistant cases
Earlier this year, the hospital shut down its emergency department and isolated one floor of the hospital to contain another outbreak of VRE.

And at the end of February, the Lakeshore General Hospital in Pointe Claire, Quebec, had to isolate more than one-quarter of its patients after six patients were found infected with a bacteria resistant to another common antibiotic, methicillin.

MRSA (methicillin resistant staph aureus bacteria) is the most common infection problem in hospitals. For these cases, vancomycin is the standard treatment.

That’s why an outbreak of VRE is so worrisome for hospitals. Right now, it’s the antibiotic of last resort.

Nation-wide monitoring
Dr. Low is part of a group doing nation-wide monitoring of antibiotic resistance through testing of samples at a central laboratory.

This monitoring has revealed a four times increase of antibiotic resistant bacteria in hospitals in since 1996.

However, outside hospitals, in the general community, resistance has leveled off. Dr. Low says public and physician awareness about the proper use of antibiotics is an important part of controlling growing resistance.

He says we cannot afford to be complacent and expect science to come up with a new miracle antibiotic.

No new antibiotics
“If you look in the last 20 years, we really haven’t had any new classes of antibiotics introduced. We’ve had derivations of older antibiotics. And you can be sure companies are searching databases, and genomics is looking at new targets in bacteria.”

“This looks like a very powerful tool. But not one drug has come to fruition from that program. We’re back to the old ways. You look in the soil for a bacterium that produced something that inhibits other bacteria. It’s a long process,” he says.

Dr. Grossman sees some encouraging signs. People are using fewer antibiotics. Prescriptions are down almost 10 per cent since 1996. He says that’s important, because the evidence shows that if total usage of antibiotics goes down, the development of antibiotic resistant bacteria slows down.

He says the message for doctors and patients is pretty basic: “Antibiotics should be prescribed when necessary, but only when necessary. When they are prescribed, we want people to take them as prescribed.”