Tallaght Hospital in Dublin is warning that it is dealing with "a number of cases" of Carbapenem Resistant Enterobacteriaceae (CRE).
CRE are a family of germs that are difficult to treat because they have high levels of resistance to antibiotics.
Healthy people usually do not get CRE infections - they are confined to patients in hospitals, nursing homes, and other healthcare settings.
The majority of patients are CRE carriers and thus experience no symptoms. But in rare cases, this can develop into an infection which can be difficult to treat.
The hospital say all appropriate precautions and screenings are being taken.
Restrictions are being put in place, including one visitor only per adult patient during designated visiting hours.
Children are not permitted to visit in any circumstances - while parents or guardians of paediatric inpatients are allowed to visit as normal, as the paediatric unit is unaffected.
Management say they are anticipating and planning for increasing demand on services in the coming weeks, in line with previous years.
"As such, intending patients are urged to contact their GP in the first instance and, if possible, avoid or delay visiting the emergency department where cases are managed according to priority.
"Regrettably, this means that less urgent cases will experience delays during very busy periods," the hospital says.