Shares in junior biotech Alchemia rocketed more than 80 per cent yesterday after early tests of its antibiotic compounds gave hope of beating hospital-acquired infections, a problem that costs the US nearly $US5 billion ($6.8 billion) annually.

Alchemia, which floated last year after offering shares to the public at 70 ¢ each, spiked 43 ¢ to a record high of 96 ¢, a gain of 81.1 per cent. The stock later ended up 56.6 per cent at 83 ¢. Alchemia's largest shareholder, Cytopia, rose 9 ¢ to 60 ¢.