Scientists in search of new bug busters


Published on 05/11/2008

By Harold Ayodo

A team of scientists pioneered a study that uses microscopic sensors to find new drugs to fight antibiotic resistance.

The study has proven that the bacteria responsible for difficult-to-treat infections in humans — MRSA and VRE— can be contained, says the lead researcher, Dr Joseph Wafula Ndieyira, a chemistry lecturer at Jomo Kenyatta University of Agriculture and Technology and a fellow at the London Centre for Nanotechnology. The first nano-mechanical study to be used in screening for new drugs was designed by Ndieyira and Dr Rachel McKendry from the London Centre for Nanotechnology.

Dr Joseph Wafula Ndieyira, a chemistry lecturer at Jomo Kenyatta University of Agriculture and Technology. [PHOTO: COURSTESY/STANDARD]

“MRSA (Methicillin-resistant staphylococcus aureus) is resistant to Methicillin and other antibiotics of the penicillin family.

The germ enters the body through abrasions, cuts, wounds, and surgical incisions causing infection.

“Enterococci — bacteria that are normally found in the bowel and vagina of humans — frequently colonise open wounds and skin ulcers,” says Ndieyira. When outside these areas, they can cause infections of the urinary tract, wounds, or bloodstream. Infections caused by Enterococci that are resistant to the antibiotic Vancomycin are called Vancomycin-resistant Enterococci (VRE), and are very difficult to treat.

Antibiotics such as Methicillin and Vancomycin bind to the bacterial cell wall, disrupting it and causing the bacteria to break down. In the past, Penicillin was used to treat staphylococcus infections, but gradually the organism became resistant to most antibiotics except for Methicillin. Overtime, MRSA have become resistant to Methicillin as well, so the antibiotic no longer kills the germ.

The sensors measure how well a drug binds to bacteria and its ability to weaken and destroy the bug.

The silicon-based technology detects minute molecular changes.

Ndieyira says emerging diseases mostly affect poor countries and they are increasing at an alarming rate.

According to the United Kingdom Health Protection Agency, there were about 7,000 cases of MRSA and 1,000 cases of VRE in England last year.

“Introduction of new antibiotics in recent decades has slowed to a trickle but fatal super bugs — drug resistant germs —continue to increase,” Ndieyira says.

The major global health problem drove the scientists to develop the new technology to investigate antibiotics and how they work. Misuse of antibiotics lead to resistance.

“The situation has resulted in the use of newer and more expensive drugs which in turn leads to resistance,” explains Ndieyira.

He cites tuberculosis that was once an easily treated infection but today is multi drug-resistance posing a threat to humans.

Antibiotics are chemotherapeutic agents which breakdown microorganisms like bacteria and fungi.

“Antibiotics have antagonistic properties that prevent growth of the microorganisms,” says Ndieyira.

Journals

They were heavily used during the Second World War to treat wounds and ulcers and have had a profound impact on the quality of life of mankind since

Over 40 websites and several scientific journals in Europe and the Far East have lauded the study.

The scientist say the research involved systematic experiments that provided a new framework for understanding the mode of anti-microbial resistance.

“A follow-up study is in progress to demonstrate how to formulate powerful antibiotics to combat new emerging infections,” Dr Ndieyira says.

Thirteen scientists were involved in the study: Nanomechanical Detection of Antibiotic Mucopeptide Binding in a Model for Superbug Drug Resistance.

Eleven particpated in the intellectual discourse whereas Rachel and Ndieyira designed the experiments.

The sensors – tiny levers no wider than a human hair – were used to examine the process, which takes place when vancomycin binds itself to the surface of the bacteria.

The researchers coated the sensors with the protein — mucopeptides — that make up the bateria cell walls and studied the changes.

They found that when the antibiotic binds to the cell it generates a “surface stress” on the bacteria. The study suggests that the stress contributed to the disruption of the cell walls and the breakdown of the bacteria.
“We compared how Vancomycin interacts with both non-resistant and resistant strains of bacteria,” Dr Ndieyira says.

It was 1,000 times harder for the antibiotic to attach itself to the resistant bacteria than the non-resistant one.

“This left the bug weakened and less able to disrupt the cells’ structure, and therefore therapeutically ineffective,” explains Ndieyira.

The Engineering and Physical Sciences Research Council and the Interdisciplinary Research Centre in Nanotechnology and the Royal Society funded the study.

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