New technique helps scientists isolate resistant TB bacteria

Scientists have come up with a new way of picking out parts of the tuberculosis-causing bacteria that resist treatment.

Using a new technique known as fluorescence dilution, a team of South African scientists found that they can identify, isolate and target the persistent bacteria.

The fluorescent dilution uses two glowing proteins to label the resistant bacteria.

One protein tracks live bacteria while the other measures its growth.

The method is applied to identify and isolate individual bacteria for study.

According to the scientists at Stellenbosch University in South Africa and Imperial College, London, the technique, which is similar to using “micro-tweezers” to physically pick out the slow-growing bacteria from the rest, enabled them to find the hard-to-identify persistent bacteria.

ISOLATING THE BACTERIA

“We were able to do this by applying the same approach that has been used to isolate the bacteria that causes food poisoning, salmonella,” said TB researchers Jomien Mouton and Samantha Sampson in an article on theconversation.com.

This involves subjecting the bacteria to conditions that come closest to those found in the body as opposed to conditions in the laboratory.

“Using this technique, we found that when bacteria entered a specific type of white blood cell, a population of non-growing or slowly-growing persistent bacteria appeared.

“White blood cells play a critical role in defending the body against invading bacteria. In the laboratory, we use them to mimic the environment found in the body,” they added.

The emergence of drug-resistant tuberculosis has significantly complicated global efforts to fight the scourge of the disease.

Each year, more than nine million people are infected with TB and another 1.5 million die.

Globally, around five per cent of TB cases are thought to have resistance to the two most effective drugs.

This translates into 480,000 cases worldwide – and 190,000 deaths from this form of TB every year.

TB CASES DROP 40PC

In Kenya, the number of TB cases has dropped by 40 per cent, but the Ministry of Health acknowledges that more still needs to be done in testing if the country is to eliminate the disease.

TB is highly contagious and is caused by bacteria called mycobacterium tuberculosis, which attacks the lung and can also damage other parts of the body.

It is spread through inhaling tiny droplets from the coughs or sneezes of an infected person.

Most TB treatments target bacteria that actively grow in the body.

“But a very important subset of bacteria is able to survive treatment. These are known as persistent bacteria,” explained the researchers at the Centre for Tuberculosis at Stellenbosch University.

Drug-resistant TB occurs when the bacteria becomes resistant to one of the common TB drugs, rifampicin.

DEVASTATING EFFECTS

Dr Mouton added that though the persistent bacteria only represent a very small proportion of the bacteria that causes TB, failing to get rid of them can have devastating consequences.

They are responsible for lengthy drug treatment, and could contribute to drug resistance. They therefore should also be the target of TB therapies.

“The challenge with these persistent bacteria is that they are very difficult to isolate. This makes it difficult to study them and therefore difficult to develop drugs to kill them,” the scientists added.

New World Health Organisation (WHO) recommendations aim to speed up detection and improve treatment outcomes for multidrug-resistant tuberculosis (MDR-TB) through the use of a rapid diagnostic test and a shorter, cheaper treatment regimen.

At less than $1000 per patient (Sh100,000), the new treatment regimen can be completed in 9–12 months, compared with the conventional treatment regimens, which take 18–24 months and cost $2,400 (Sh240,000) for the medicines alone.

“The shorter regimen is recommended for patients diagnosed with uncomplicated MDR-TB, for example those individuals whose MDR-TB is not resistant to the most important drugs used to treat MDR-TB, known as “second-line drugs”.

“It is also recommended for individuals who have not yet been treated with second-line drugs,” says a statement from the WHO.