Doctors at University College Hospital last month found bacteria on the unit that were resistant to antibiotics commonly used to treat infections in very premature babies.
Over six weeks 15 babies were found to be carrying several types of bacteria, 13 of which had bugs resistant to treatment with gentamicin.
Of those nine carried the resistant bacteria on their skin and four had bloodstream infections.
Records of a meeting, passed to the Daily Telegraph, show one baby died from its infection and two others died with the bugs but it is not thought to have been the primary cause of death.