Because of financial cuts no routine cleaning was carried out on Sundays before the outbreak, a conference organised by the Royal College of Physicians of Ireland has heard.
Over 2,000 people at the hospital have come into contact with carbapenemase-producing enterobacteriaceae (CPE) since the bug, which is resistant to most antibiotics, was first identified in mid-2015.
The most at risk from the outbreak were vulnerable patients who were on too many antibiotics that were admitted from nursing homes.
As a result the hospital has had to dramatically increase its cleaning budget, close wards, cancel 700 operations, restrict visiting and test hundreds of patients every week.
Other factors given for contributing to the outbreak were too few staff, overcrowding with high numbers of patients on trolleys, an insufficient number of single rooms and inadequate IT systems.