All babies transferred to other units from two hospitals in Northern Ireland where four infants died are to be screened for the killer infection, public health authorities said.
Neonatal rooms across the province are to be checked for babies moved during the last two months.
All taps and connected pipework in the neonatal room at Belfast's Royal Jubilee Maternity Hospital are to be removed as experts try to eradicate all traces of the pseudomonas bacteria.
The outbreaks there and at Altnagelvin Hospital in Londonderry have been linked to the taps.
Three newborns died in the Royal this month and one late last year in Altnagelvin.
Public Health Agency (PHA) assistant director Dr Lorraine Doherty said: "All the babies transferred from Altnagelvin or the Royal since the 14th of November, we are asking for them to be screened.
"We believe it probably affects most of the neonatal units across Northern Ireland."
Health chiefs said infants who had since been discharged from hospital did not need to be screened because the bacterium usually affects those who are ill and vulnerable.
One baby continues to be treated at the Royal for pneumonia amid as yet unconfirmed fears that it has also contracted the potentially deadly infection.
Two infants who had no signs of the bacterium when they were sent from the Royal to Antrim and Craigavon area hospitals have now been found to be carrying it on their skin.
A total of three babies died in the Royal's neonatal unit and one baby recovered but later died from an unrelated cause, the PHA said.
An outbreak of a different strain of pseudomonas in Londonderry's Altnagelvin Hospital last month, which claimed the life of one baby, was also linked to the water system in its neonatal facilities.
Chief medical officer Dr Michael McBride wrote to other trusts alerting them of the danger after the death.
Health Minister Edwin Poots said yesterday that special ultra- violet technology may be installed in the region's hospitals in a bid to prevent further outbreaks.
Pseudomonas can cause infections in the chest, blood and urinary tract.
The neonatal unit at the Royal, which was emptied in the wake of the outbreak, has undergone a deep clean.
Dr Doherty added that the situation across Northern Ireland was being reviewed by health estate managers to consider whether taps or other infrastructure needed to be removed.
The babies in Antrim and Craigavon were transferred on Friday evening as the Royal was being cleaned. The baby in Craigavon has been discharged and the baby in Antrim is in isolation.
The PHA was asked why the Royal's taps were not checked after the death in Altnagelvin, despite the fact that a baby was transferred to the Royal from the Londonderry hospital.
Dr Doherty said: "The baby does not pose a risk to the taps in the Royal, there was no evidence of pseudomonas contamination of the taps in the Royal, there was no evidence of a wider issue.
"When you had a baby that was transferred from Altnagelvin to the Royal, staff in the Royal were made aware of this baby.
"If we determined that there was a wider issue with taps of course we would look at taps."
There were three cases of pseudomonas in the outbreak at Altnagelvin in December last year, resulting in the death of one baby.
Of the other two babies, one recovered, while the second was transferred to the Royal.
Mr Poots said yesterday that of three other babies (apart from the one with pneumonia) believed to have contracted the infection at the Royal, two have recovered and continue to receive neonatal care, while the third initially recovered but subsequently died of unrelated causes.
The minister said seven other babies were found to be carrying traces of the bacteria, for example on their skin, but had shown no signs that they had contracted the infection.