Four of the 52 patients affected have died, and the hospital believes an antibiotic-resistant strain of the Klebsiella pneumoniae bacteria was the cause of death in at least one case.
The outbreak was discovered this spring but is believed to have begun in the autumn. All of the patients affected had undergone open heart surgery at the Thorax Clinic in Solna.
“We have put in place a range of measures and hope now to have stopped the spread, since we haven’t seen any new cases for two to three weeks,” chief physician Elda Sparrelid told news agency TT.
The hospital has not yet fully ascertained whether the patients died as a result of the outbreak.
“It’s not so easy to conclude as these are patients who were very sick for different reasons, but we do have strong suspicions in at least one case,” she said.
The strain of Klebsiella pneumoniae at Karolinska contains ESBL, an enzyme that can break down antibiotics.
Most of the patients affected have carried the bacteria without suffering unduly, since the bacteria itself does not generally make people sick. If however they need any treatment requiring antibiotics doctors could find that these no longer work.
The hospital has tightened its hygiene procedures since discovering the outbreak earlier this year.
But Elda Sparrelid said staff had not followed all procedures correctly, adding that the hospital was also introducing new routines.
“This relates to everything from staff compliance to the procedures we have for clothing, equipment, keyboards and the cleaning of instruments – everything we have been able to identify. In all we have put in place around 100 measures,” she said.
The hospital has reported the outbreak to the Health and Social Care Inspectorate (IVO).