The testing technique was capable of detecting any sub-types of the H5N1 strain, said Professor Yong Poovorawan, of Chulalongkorn's Faculty of Medicine, who led the development team.

"This means it could be used anywhere in the world to see if the virus is resistant to oseltamivir or not, and in time to save patients' lives," he said.

Moreover, the testing technique was also developed to be used with a conventional biomolecular testing laboratory in areas where the advanced type was not available.

It had been found that a significant difference between the H5N1 virus, which was oseltamivir resistant, was the change of amino acid at position 274 of the N1 subtype, Yong said.

The new testing method was developed based on this finding, using both Real-Time Polymerase Chain Reaction (RT-PCR) and Conventional PCR. The former takes between two to four hours to know the results, whereas the latter takes approximately eight hours to tell whether the virus is resistant to the drug or not.

Chulalongkorn researchers had tested the technique on both human and animal specimens and whether both were resistant to oseltamivir. The human specimen of the world's first case of oseltamivir resistance in Vietnam was taken for testing in Thailand.

In October last year, a 14-year-old Vietnamese girl infected with the bird flu virus become the first patient to show resistance to oseltamivir when laboratory tests showed the drug had failed to combat the virus in her body.

In December last year, Vietnam detected oseltamivir resistance in three out of eight patients, said Yong, adding the patients died as a result of doctors discovering too late that the virus could outsmart the anti-viral Tamiflu - or oseltamivir.

"That inspired us to begin studying and to develop a sophisticated testing technique that gives the results fast enough for doctors to save patients' lives," Yong said.

The only substitute for oseltamivir is Zanamivir, which is not as convenient to use as it can only be administered through the nostrils or via intravenous injection, unlike oseltamivir, which is taken orally.

The study results prove the accuracy and efficiency of the drug resistance test. The test using RT-PCR is expected to appear in the Journal of Virological Methods next week and the test using Conventional PCR in Emerging Infectious Diseases in December.

The mortality rate of bird flu in humans was as high as 60 per cent, Yong said.

In Thailand, the Public Health Ministry has plans to stockpile 100 tablets of oseltamivir, which could be useless if the virus became resistant to the drug, he said.

Yong said the resistance factor had yet to be detected. However, this did not mean it did not exist. "The more the drug is used, the higher the chance of the virus becoming resistant to it," he said.

Arthit Khwankhom

The Nation