The parents of the first baby to die in the pseudomonas outbreak have told the BBC they believe he may have survived if the Western Health Trust had strictly followed hygiene guidelines on managing the infection.
Gavin Burke and his partner Caoimhe's baby, Caolan, who was premature and seriously ill, died in December 2011.
He was being cared for at Altnagelvin Hospital, Londonderry. An interim report found that heavy growths of the bacteria were found in a tap in the intensive care unit.
The report, published before Easter, looked into the outbreak in which a total of four babies died - one at Altnagelvin and three others in the Royal Jubiliee Maternity Hospital, Belfast.
The report said at least three alerts or circulars were sent by the Department of Health to NI trusts on how to manage pseudomonas. The first was sent in September 2010.
In July 2011 in another alert, trusts were also advised to perform regular water sampling tests and to remove any taps no longer used.
However, the report said that months after that second alert was issued, a tap at the back of the Derry neo-natal unit was found to have a heavy growth of the bacteria. This was found in swabs taken from the sink on 13 December 2011.
Mr Burke said if the trust was following the guidelines this bacteria should never have formed. Or if it had - it should have been caught in the early stages.
"What I don't understand is that the trust was told to check the sinks and the taps, all of the water systems. But the swabs say that there was a thick growth of the infection. That takes time to develop.
"This sink was in the place where my son was being cared for. It's just awful, he was fighting enough without having to fight off that as well."
The report found that pseudomonas was first detected in the unit following tests on a different baby who showed signs of being infected on 26 November. Those test results were confirmed two days later.
While that baby was transferred to the Royal Jubilee Maternity neo-natal unit for another condition, other babies continued to be cared for in Altnagelvin's neo-natal unit.
One of them, Caolan Campbell, tested positive for the infection on 8 December. That is 12 days after the trust first became aware they had a case in the hospital.
The couple said if these critical care areas were being properly checked, the bacteria should have been detected a lot sooner.
While Gavin acknowledges his son was very ill he said it was the hospital's responsibility to provide the best environment for him to try and get better.
"As a parent of a very sick child, I should have been told that my son was in an area where a child was infected with pseudomonas. In fact, Caolan wasn't even born when that first baby got sick.
"I also think there was a delay in testing my son for the infection. Just how long did it take for the staff to realise my child was at risk of contracting the infection - if they'd acted sooner, might he have survived? Caoimhe and I will never know. "
The review team, led by Professor Pat Troop, also highlighted that the trust said the part of the unit which housed the contaminated sink was rarely used.
The couple and their solicitor, Walter Hegarty, contest this. According to statistics provided by the health trust, the unit was working to capacity.
"I know that the first wee baby who got sick was nursed in that area close to the tap - then my son was moved into it. If they had been checking the taps and sinks, they would have known about the infection and Caolan would not have been moved in there."
The 2011 circular sent from the Department of Health also requested that trust chief executives provide a written statement that all checks were being complied with. The Derry couple want to see a copy of that statement.
A spokesperson for the Western Health and Social Care Trust said it understood that the questions Caolan Campbell's family were asking were among issues that would be examined in Professor Troop's final report at the end of May 2012.
"The trust is participating fully in this review and will not comment further until Professor Troop's second report is published", the spokesperson added.