The Bugs We Can't Defeat

Jane Hansen | October 08, 2008

ANTIBIOTICS have been thrown at everything, from the most infectious diseases to the slightest cough. As well, in pursuit of higher profits, food producers have used them to fatten up chickens and pigs. As a result, bacteria are becoming immune to a depleted arsenal of the wonder drugs of the 20th century. And the golden era, in terms of controlling and curing illness and death caused by bacteria, is coming to an end.

David Paterson with E. coli at the University of Queensland; he says the bug produces an antibiotic-destroying enzyme.

"I've lived in the days before antibiotics, and they weren't pleasant," recalls Kathleen Calvert, a 71-year-old retired teacher based in Canberra. As a child she suffered dreadful middle-ear infections.

"You just had to endure the pain, wait for an abscess to form and then it would burst, time and time again, and I'm partially deaf in one ear as a result."

Then along came the miracle drug of the 20th century, penicillin, and Calvert finally rid herself of the ailment that had plagued her childhood. Now she is at the other end of the antibiotic golden age, battling a multi-drug-resistant bug she picked up in China.

"I have had a recurring urinary tract infection that flares up every six months, I can't get rid of it," she says of the common ailment that affects millions of women worldwide. For the past few decades, it has been treated by a simple three-day course of oral antibiotics, but those drugs are impotent against the strain Calvert acquired in Beijing.

"I've had four week-long intravenous courses with last-line antibiotics and it keeps coming back. I've felt like typhoid Mary. People avoid you and think they might be contaminated by you," Calvert says.

Sharing a bath towel with Calvert could pass on the infection, theoretically, but the bigger threat is that the rogue bacteria will swap its resistant gene with local bugs, giving birth to a home-grown resistant bug. There is good evidence this is happening.

"Bacteria are really good at having bacterial sex and swap their resistant genes at a rapid rate," says Peter Collignon, head of infectious diseases at Canberra Hospital and microbiologist with the medical school at the Australian National University.

Doctors believe travel to developing countries is one possible reason for the rapid emergence of drug-resistant E.coli and other gut bugs among healthy people who have had no previous contact with the hospital system.

Superbugs, those born and bred in hospital corridors in response to high antibiotic use, have plagued patients for years, but sister versions of these bugs are emerging at a rapid rate in the community, affecting the young and healthy.

"The doomsday scenario of a world without effective antibiotics is already playing out in countries like China," Collignon says. "They don't keep good data and the media is controlled, but people are dying regularly from complications of drug-resistant common bugs like E.coli, and golden staph, and tuberculosis."

Like most organisms, big and small, bacteria have forms of attack and defence, and some produce toxic substances that can kill other bacteria: we call them antibiotics. In response, other bacteria produce enzymes that can neutralise the antibiotics. The same battle is being waged on the human health front because of the overuse of antibiotics. And the resistant bacteria are winning.

Nasty bugs that cause tuberculosis have armed themselves to defy the drugs that cure often fatal ailments. A recent study published in The Medical Journal of Australia proved a multi-drug-resistant strain of tuberculosis, called MDR-TB, is already on our doorstep in the Torres Strait.

Of 60 patients from the Western Province of Papua New Guinea, 15 had MDR-TB and mortality was high. Islands of the Torres Strait are only 5km offshore and villagers visit each other frequently.

"It's a difficult ailment to treat at the best of times, requiring four separate oral antibiotics staggered over six months," says Christopher Coulter, one of the study's authors. "The MDR-TB needs 18 to 24 months of expensive oral and intravenous treatment with last-line drugs. The doomsday scenario is a return to the days where you can't treat it, which is already happening in South Africa."

The report calls for urgent intervention to stop the spread of MDR-TB to the mainland.

Next month, the federal Department of Health and Ageing in conjunction with Queensland Health will co-ordinate the building of a TB laboratory and clinical management project to diagnose and treat MDR-TB in PNG.

The other killer is the community version of resistant golden staph, or methicillin-resistant staphylococcus aureus. Once confined to hospitals, where it kills up to 2000 compromised patients a year, the community version emerged across the world at the same time in the late 1990s.

In Australia, the so-called Queensland strain has a flesh-eating toxin and it is more virulent than the hospital version.

"Not only does the community strain have a Kevlar vest on, it also has this Exocet missile attached that destroys flesh," Collignon says.

To glimpse the hellish world where antibiotics are powerless against such vicious bugs, you just have to walk into Julie Gray's Sydney home. The ashes of her "beautiful, strapping young son" Reis sit in a polished wooden box on the mantelpiece, his precious guitar in a stand nearby.

A year ago this month, Reis had what everyone thought was a bad dose of the flu. The GP gave him antibiotics, but after three days he was taken to hospital.

"I just didn't like the colour of his skin," Gray recalls.

"At the hospital they found his pulse was so low, they had to put him on life support. Before he closed his eyes he asked me, 'Will I be OK, Mum?' I said, 'Of course you will.' But he never woke up. I just never thought a simple bug could kill a healthy 16-year-old who'd never been to hospital in his life." He died from the community version of MRSA: the flesh-eating toxin "just ate his lungs", Gray says, shaking her head in disbelief.

Community-acquired MRSA causes boils and abscesses, but in rare cases it can go to the lungs and kill, Collignon says.

"That is a real worry when one in 10 staph infections are now attributed to community-acquired MRSA," he says.

Now E.coli, the most common germ known to cause infection in humans, also has become drug resistant outside hospitals.

"They can defy almost every antibiotic," says David Paterson, an infectious diseases consultant to the Royal Brisbane & Women's Hospital and a world authority on so-called gram negative bacteria such as E.coli. "The bug produces enzymes called beta lactamase and they physically destroy antibiotics."

The overuse of antibiotics throughout the world has caused the problem, especially in developing countries, where you can buy second and third-generation antibiotics - the so-called last-line antibiotics - over the counter. Farm producers also feed them to chickens and pigs.

"In the US and Brazil, every chicken, before it has even hatched, is injected with a third-generation antibiotic," Collignon says. "The antibiotics aren't in the food, the resistant bugs are. So food, if not washed or cooked properly, can become a source of contamination." Collignon proved his point by culturing his own faeces before and after a recent trip to China. Despite being fastidiously clean, what he ate produced a drug-resistant strain of E.coli on his return.

With the international trade in food, the bugs have spread. In the US in 2006, Paterson, then with the University of Pittsburgh's school of medicine, cultured bacteria from chickens bought in a variety of supermarkets. Most carried the enzyme that makes them drug resistant.

Australia does not import fresh chicken and recent attempts by food producers to do so were quashed. We do, however, import fresh fruit and vegetables.

In a 2007 Australian Quarantine Inspection Service imported food survey, 97 samples were tested for E.coli.

"E.coli was detected in 14 samples, mainly in exotic leaf crops. These leaf crops are usually washed and/or cooked prior to consumption. E.coli was also found in some vegetables: taro, baby corn, asparagus and mushrooms. Again, these vegetables are generally washed and/or cooked prior to consumption. Health authorities in Australia recommend washing and cooking vegetables as a risk-mitigation step for the presence of micro-organisms, including E.coli," the report says.

Food Standards Australia advised at the time that the levels of E.coli found in the products would not seriously affect human health. But they were there nonetheless.

The other big problem is that there is little or no investment in future antibiotics, Collignon says.

"Antibiotics are a bad investment for drug companies. For a start, they are drugs that cure, so it's much better from a drug company's perspective to pour money into drugs that control symptoms for things like diabetes and heart disease, drugs that patients have to take for life," Collignon says.

Says Paterson: "Then you've got doctors like Professor Collignon and myself telling everyone not to take these precious drugs, keep them in reserve unless absolutely necessary." Antibiotics have been the one true miracle drug, stopping people from dying in large numbers. But the miracle is fast fading. Paterson likens the present climate to the heady, hedonistic days of the late 1970s.

"It is like San Francisco and Sydney in the late '70s, when no one gave thought to any controls over what we might do if HIV came along, but when that horrific epidemic happened, for many people it was too late."