Enzyme teaches bacteria to resist drugs

The drug-resistant strain is widely seen as a product of the overprescription of antibiotics around the world. (David Harrison)

The drug-resistant strain is widely seen as a product of the overprescription of antibiotics around the world. (David Harrison)

The drug-resistant strain is widely seen as a product of the overprescription of antibiotics around the world.

The invaders are bacteria that produce an enzyme called New Delhi metallo-beta-lactamese-1, or NDM-1. The level of hysteria and exclamation marks is slowly growing in headlines, but it has not reached the levels during the swine flu outbreak. Five people have died since the first case in August last year.

It is thought to have originated on the subcontinent in 2009, with the first fatality occurring in 2010. A Belgian man had a car crash while he was in Pakistan, and contracted an infection when he was being treated in hospital. He died soon after.

Professor Adriano Duse, an expert in controlling infections and head of the clinical microbiology and infectious diseases department at the University of the Witwatersrand, said the bacteria that produce NDM-1 are concerning. "They are very resistant to antibiotics, making infections caused by them difficult to treat."

Teaching, or encoding, bacteria to be resistant to antibiotics is where the NDM-1 enzyme does its most damage. And the one that it is best at teaching is Klebsiella pneumoniae. This lives in the large bowel and causes fever, chills and causes thick mucus to build up in the lungs.

So when someone goes to hospital with a disease or injury, it springs into action. Where normally the patient would be given a course of antibiotics to help their white blood cells to fight the infection, these stop that process. And without the extra help the condition they were originally admitted for is more likely to kill them.

In healthy people it can lie dormant in the bowel, doing nothing. But when people's immune systems are low it is at its most potent. The saving grace is that they do not affect the community at large, said Duse. Rather they target those with "serious underlying illnesses that need to undergo hospitalisation", he said.

Possibility of further spread
Therefore, the key to fight them is through hygienic infection control in hospitals. All the cases in South Africa have been at hospitals, and all in Gauteng. The national institute for communicable diseases has issued warnings for people working in hospitals.

Straight after the first case, the department of health announced it would monitor the outbreak and do more research to see what could be done to stop it. It also concluded that "the possibility of further spread is limited".

As part of this, Duse said, an in-depth investigation is trying to find the source of the bacteria so it can be defeated.

Dr Joseph Rahimian, an infectious disease specialist in the United States, also blamed the over-use of antibiotics when talking about a similar outbreak there.

"If other people are using unnecessary antibiotics, they are promoting the development of resistance, which might affect you even though you didn't do anything."

Research in the New England Journal of Medicine pinpoints the rate of reproduction of bacteria as the biggest problem for a cure. Because they create a new generation every few minutes, they have great scope to evolve and find their way around new antibiotics. At the same time these antibiotics take years to go from concept to testing before being approved.

NDM-1 has also been found in a cat in the United States.

Sipho Kings


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