Tag: tuberculosis

a new antibiotic

tuberculosis

Tuberculosis bacteria

Much ink has been spilled over the lack of new antibiotics and the increase in drug resistant bacteria. But a few weeks ago, there was finally news of a breakthrough. Researchers have finally discovered a new antibiotic, teixobactin.

Teixobactin works by binding lipid precursors of the cell wall. This interference weakens the bacterial cell wall, causing the microbes to leak and die. The drug is only effective against gram-positive bacteria, like Staphylococcus aureus and M. tuberculosis, and it could help combat resistant strains that commonly cause MRSA infections. Teixobactin was active against MRSA infections in mice. It is not effective on gram-negative bacteria, like E. coli.

The method they used to discover the antibiotic is also quite interesting. Compound Interest explains:

We know bacteria produce their own antibacterial compounds, to combat other competing bacteria. However, since 99% of bacteria can’t be grown in lab conditions, this greatly limits the number of these compounds that we can investigate. The method used to discover teixobactin overcomes this, by diluting soil samples, then placing small samples containing single bacterium cells in a device they named an ‘iChip’.

The ‘iChip’ is essentially just a device with a large number of small channels, into which bacteria can be deposited. The channels are then covered with a semi-permeable membrane, which allows environmental factors which influence bacterial cell growth to diffuse across to the bacterium cells. Using this method, the researchers were able to cultivate bacteria which were not previously grown in lab conditions, as once a culture is formed it is easier to entice them to do so. The researchers isolated 25 different antibiotic compounds, of which teixobactin is the most promising.

This is potentially a giant step forward for antibiotics and antibiotic discovery.  For further reading check out the original publication. Also check out coverage by Ed Yong, Science Magazine, and Scientific American.

fighting tuberculosis with rats

Image from NPR. Abdullah Mchumvu trains African giant pouched rats in Morogoro, Tanzania

Tuberculosis still kills 1.4 million people a year, mostly in the developing world. So it is still beneficial to create new diagnostic techniques, especially when they can be used in rural communities. NPR recently reported on a team of scientists who train African giant pouch rats to sniff out the bacterium in patients’ sputum:

The team trains the critters with a Pavlovian click-and-reward approach. When the rats are just a few weeks old, technicians teach the animals to associate a click sound with a small bite of mashed bananas and a special pellet of food. The next step is to link the scent of TB with the reward.

A trained rat can correctly pick out a TB sample about two-thirds of the time, Beyene says. The rate increases to about 80 percent when two or three animals are put on the task.

The rats aren’t as good as a trained pathologist in the U.S. with a microscope, but they get better results than many clinicians working in rural Africa can achieve, Beyene says. “In an African setting, the sensitivity of the microscopy ranges between 30 to 40 percent,” he explains.

So far APOPO only has around 32 rats in their TB program.

Currently the rats are being used to verify positive test results obtained from microscopic samples.

a new tuberculosis vaccine falls short

tuberculosis

Tuberculosis bacteria

A new study of the potential tuberculosis vaccine, modified Vaccinia Ankara virus expressing antigen 85A (MVA85A), has failed in a study of 3000 infants in South Africa. Scientists had hoped it would help improve protection against the infection when used with the current vaccination (BCG). The study was a double-blind, randomised, placebo-controlled trial of healthy infants (aged 4—6 months). The infants were randomly administered BCG with either MVA85A or a placebo of Candida skin test antigen then examined every 3 months for up to 3 years. During the course of the trial, the rates of serious or systemic infection from tuberculosis were similar for the group that received the new vaccine enhancer compared to those given the placebo. The researchers did note that the MVA85A does appear to be safe and that no adverse effects were cause by the antigen itself. This was the first efficacy trial of a tuberculosis vaccine in infants in more than 45 years. More details here at The Lancet [subscription required].

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