Reports that many victims died within a day of showing symptoms have also added to the disquiet.

Hong Kong's Health Authority late on Tuesday said a butcher at a leading supermarket chain had become the fourth person to become infected with the bacterium in the territory since the outbreak in China was first reported in June.

The pig scare comes amid reports of a bird flu virus hitting parts of China, Russia, Mongolia and Kazakhstan. The H5N1 strain has killed more than 50 people across Asia, most in Vietnam, and led to the culling of some 140 million birds.

"Streptococcus suis is not a very resistant bacterium -- we can normally kill it by penicillin. But the government has suggested using much stronger antibiotics... Maybe the bacterium has mutated to a more resistant strain," microbiology professor Li Mingyuan, of Sichuan University, told the South China Morning Post recently.

The pig and bird diseases have raised questions about the over-aggressive use of antibiotics in animals as well as humans. Bacteria have a will to survive and react to frequent and improper use of antibiotics by becoming resistant.

Experts in Hong Kong say bacterial resistance must be tackled quickly.

ANTIBIOTICS USELESS AGAINST VIRUSES

"Penicillin can be used in New Zealand and America to kill bacteria like Streptococcus pneumoniae (a major cause of pneumonia). But in Hong Kong, resistance is so bad that even if penicillin works for you, you will have use take higher doses or you have to use other antibiotics," said Raymond Mak, a pharmacist at the Queen Mary Hospital in Hong Kong.

"Streptococcus pneumoniae is not only resistant to penicillin, its resistance to quinolones is becoming worse," he told Reuters in an interview, referring to a class of powerful antibiotics.

Scientists blame bacterial resistance in Hong Kong to improper and overprescription by doctors, many of whom readily dispense antibiotics to patients who may just have colds or the flu -- for which antibiotics are totally useless as they can't fight viruses.

Antibiotics are also readily available over the counter.

"Bacteria are just living things, they want to live. If you put a lot of pressure using particular antibiotics, they will become resistant and continue to live. They will mutate, use all means to get around it," said microbiology professor Margaret Ip at the Prince of Wales Hospital in Hong Kong.

Many doctors also prescribe antibiotics that cover a wide range of bacteria without doing proper lab tests.

The scientists say such practices must be stopped or mankind will face a shrinking pool of antibiotics that work.

William Chui, pharmacology honorary associate professor at the University of Hong Kong, warned: "We haven't got enough antibiotics to choose from because their shelf lives are getting shorter. Before, it took 20 years. Now a drug faces resistance in 10 or even five years.