Tour of microbes - lessons not learned from history

Dealing with the emergence of extensively drug-resistant tuberculosis on the North Queensland border is one of the tours available at this year’s Australian Society for Microbiology meeting.

Cairns-based respiratory physician Dr Stephen Vincent is familiar with the problem of multidrug resistant tuberculosis (MDR TB), now he is preparing to deal with extensively drug resistant tuberculosis (XDR TB) as it emerges on Australia’s border.

This highly lethal, mutated variant of the tuberculosis (TB) bacterium has been confirmed in Papua New Guinea (PNG), with six cases reported to date. One patient, who was brought to Cairns from PNG, recently died.

“Two years ago there were no known cases of XDR TB in PNG,” said Vincent. “Now there is a reservoir of drug-resistant TB on our doorstep.”

Most of the burden of resistant TB appears to fall on poor countries - XDR TB also occurs in countries across Eastern Europe and South East Asia - but there have been some outbreaks in North America as well. New York City had an epidemic of multidrug resistant (MDR) TB in the early 1990s.

Towards untreatable TB

TB is caused by infection with the bacterium Mycobacterium tuberculosis. It is highly contagious and primarily affects the lungs but can also affect other organs in the body, such as the central nervous system, lymphatic system and circulatory system.

The disease was called ‘consumption’ in the past because of the way it consumed an infected person from within, causing a slow death. Treatments for TB became available in the 1950s. Before this people underwent surgery, sanitisation and complete isolation.

Two antibiotics were developed and patients would initially respond well to these drugs but over time they would become ill again. It was then realised that combination treatment was needed to control TB.

“The emergence of resistance to TB began in the 1950s and it was kept under control,” said Vincent. “But due to complacency and lack of government policy, resistance has become worse and today we are heading back to the pre-1950s when TB was untreatable.

 Poor compliance and noncompliance to medications by patients has resulted in TB developing resistance.

“We now have MDR TB, XDR TB and totally drug resistant TB (TDR TB) is not too far away,” said Vincent, adding that to be properly monitored and controlled, TB needs government intervention, public awareness and clinicians with TB expertise.

According to the World Health Organization, up to 4% of TB cases worldwide are resistant to more than one antituberculosis drug.

XDR TB is resistant to the two most potent TB drugs, isoniazid and rifampin, as well as the broad-spectrum antibiotic fluoroquinolone and at least one of three injectable second-line antibiotics (ie, amikacin, kanamycin or capreomycin).

Despite this, XDR TB can be successfully treated in about 50% of affected people. Successful outcomes depend on the extent of the drug resistance, the severity of the disease, whether the patient’s immune system is weakened and adherence to treatment. But TDR-TB is untreatable, which is a major concern.

On our doorstep

Due to poor TB programs, PNG has a high prevalence of MDR- and some cases of XDR-TB.

PNG is only 3 km away from the Queensland border. Just off the tip of Cape York, two Australian islands in the Torres Strait, Saibai and Boigu Islands, separate Cape York Peninsula from PNG. And Vincent said there is a lot of movement between these islands and PNG each year.

“This open border is a concern,” said Vincent. “The Australian Government doesn’t seem to realise the importance of TB. It is giving money to AusAID but PNG needs more basic infrastructure to reduce poverty and tackle the disease at this front.”

The AusAID program is specifically aimed at establishing a TB program in the Western Province of PNG; however, without improving basic infrastructure such as overcrowding, sanitation and adequate food supply, communicable diseases such as TB are unlikely to ever be adequately controlled.

Vincent said the people who live in the islands off West Papua, for example Daru Island (see image), are living in poverty.

“The towns of these islands are overcrowded,” he said. “They do not have adequate housing and there is no sewerage, running water or access to medical care.”

This high population density and the poor sanitary conditions create a perfect environment for TB to propagate, due to the close proximity of infectious cases.

A public health disaster

XDR-TB is expensive to treat. And it has a low cure rate and a high death rate.

“It can cost up to $1 million to treat one person over two years, and this exponentially increases as the resistance increases,” said Vincent.

Treatment involves giving an infected person as many TB medications as possible, which gives them around a 50% chance of surviving. A new drug recently came onto the market for XDR TB, but it is not ideal because it is expensive and has a high mortality rate.

“We are running out of options for treatment,” Vincent said. “And there is a big risk that XDR TB will come into Australia in 5 or 10 years. It’s best to avoid it getting in and to do this we need government support to train people in monitoring the disease.”

For this to happen, a strong and visionary political commitment is needed from the federal and state governments, which Vincent said is not happening. The Queensland Government, for example, has been cost cutting, including making cuts to the public health system. This has resulted in uncertainty about the future of TB services, including monitoring TB.

“We’re trying hard in North Queensland to monitor new cases in the Torres Strait, but to do this we need to maintain trained staff in the PNG/Australia border,” said Vincent, concerned the problem is being ignored.

It will be a public health disaster if XDR TB spreads into the Australian population, although Vincent thinks it is inevitable that this will happen.

“Dealing with this disease needs vision and future planning,” he said. “There is a lack of adequate services and we also need to maintain adequate expertise in TB around the country because this will be needed.

“We need to maintain vigilance at the border and we need government commitment to do this,” he said.

Stephen Vincent is a respiratory physician based in Cairns. He is the current director of Thoracic and Sleep Disorders Unit at Cairns Base Hospital. Following a medical undergraduate degree at Monash University in Melbourne, he completed his respiratory training and spent three years at the Woolcock Institute for Medical Research in Sydney, researching asthma. He moved to Cairns in 1996, where his interest in TB began as one of the TB physicians involved in the Regional TB control Unit which covers the Cape and the Torres Islands. He maintains links with the PNG TB program via a clinical collaborative group and is also a member of the national MDR-TB working group.