Outpatient services at the Colonial War Memorial Hospial in Suva have also been diverted to nearby health centres.
The Ministry of Health says acinetobacter baumanii bacteria were found in six patients during routine testing last weekend.
The hospital's acting superintendent, James Fong, told the Fiji Times that preventive measures were activated as soon as the bacterium was discovered.
He says the paediatrics unit has been moved to a different part of the hospital, and the infected children are in a stable condition, isolated in the intensive care unit.
