A rare superbug detected in a slaughterhouse in Sheung Shui has never before been found among livestock in Hong Kong or Asia, a University of Hong Kong study has confirmed.
The microbiologist who led the study told the South China Morning Post it had raised concerns that pig farmers in Hong Kong or on the mainland were misusing antibiotics to treat their animals, leading to the development of such drug-resistant superbugs.
"It indicates that there may have been widespread use by some farmers of antibiotics to keep their pigs healthy," Ho Pak-leung said. "This is one explanation as to why [the Sheung Shui] pork contains the drug-resistant bug."
Humans can catch the superbug through eating uncooked pork or coming into contact with infected livestock, Ho said.
But the risk of Hongkongers becoming infected remains low - as long as they only consume pork that has been thoroughly cooked, he said.
The superbug, vancomycin-resistant Enterococcus faecium(VRE), was detected in one of 137 batches of pork samples collected in January at a slaughterhouse in Sheung Shui.
Genetic analysis confirmed the bug to be of the sequence type ST6, never before detected in any animal bred for consumption in Asia. Another strain of VRE, ST414, is more common in Hong Kong and causes several deaths a year during hospital outbreaks, Ho said.
VRE infections tend to occur in already debilitated patients, and usually break out within a contaminated institution, such as a hospital. Mortality rates for VRE infections have been calculated at between 40 and 70 per cent. It can be contracted and carried by a healthy person for years without any symptoms, only to attack when the carrier becomes sick or is injured.
The infected pork in Sheung Shui could not be traced because the slaughterhouse gathers animals from both local and mainland farms.
Ho said: "The reason for its occurrence is still unknown. We cannot rule out the possibility that there may be a VRE outbreak in some farms."
A paper detailing the study's findings argued that the mainland, which has a problem with bacteria in livestock that is resistant to conventional antimicrobial treatment, should more strictly regulate and monitor the use of antibiotics by farmers there.