NHS Greater Glasgow and Clyde has launched an investigation after the microorganisms were discovered at the Royal Hospital for Children.
Concerns have been raised for the safety of those with “compromised” immunity, with three children being treated for infections which may be linked to the issue.
Dr Teresa Inkster, infection control doctor, said: “It’s not unusual for children in this type of ward to suffer infections but we are carrying out tests to determine whether these bacteria are linked to any of the three patients.
“However, we can confirm none of the three patients are giving any cause for concern as a consequence of their infection.”
The source of the bacteria is as yet unknown but the hospital has sought advice from Health Protection Scotland, Health Facilities Scotland and Scottish Water.
Alternatives to tap water supplies have been brought in for paediatric patients in wards 2A, 2B, 3C and the hospital’s intensive care unit.
The health board has also given out oral antibiotics due to the low immune system of these patients.
Sterilised water is being supplied for drinking and bottled water for brushing teeth.