Restriction of third-generation cephalosporins plus infection control measures ended recurrent outbreaks of multi-resistant Acinetobacter baumannii in an Australian hospital

Abstract

In 1992, an outbreak of multi-resistant Acinetobacter baumannii (MRAB) occurred in the intensive care unit (ICU) of Royal Perth Hospital (RPH), spreading to the orthopaedic surgery wards in 1992 and to the spinal unit in 1994. Objectives: this report describes the recurrent outbreaks of MRAB that occurred in RPH from 1992 to 1998, and interventions used to control the outbreaks. Methods: from 1992 to 1995, infection control measures used at RPH to control multi-resistant bacteria were applied: isolation of patient carriers (in a separate isolation unit, when possible), screening of patient contacts, staff hand antisepsis after attending isolated carriers and daily disinfection of source isolation rooms (intervention 1). In 1995, these measures were augmented on the outbreak wards by staff hand antisepsis after attending every patient (MRAB carriers and non-carriers) (intervention 2), daily disinfection of the whole ward (intervention 3) and daily whole-body antisepsis of carriers (intervention 4). After July 1996, most MRAB isolates were typed by pulsed-field gel electrophoresis. After August 1996, approximately half the spinal unit inpatients were screened for MRAB on admission and at discharge. After April 1997, all spinal unit inpatients were screened monthly during their stay in hospital. In 1997, third-generation cephalosporins (cefotaxime, ceftriaxone and ceftazidime) were restricted on the orthopaedic and spinal units (intervention 5). Results: intervention 1 appeared to slowly stop each outbreak but did not prevent recurrences and the number of new carriers per annum trebled from 1993 to 1995. The addition of interventions 2, 3 and 4 almost eliminated MRAB from the ICU and reduced the number of new carriers per annum on the orthopaedic wards but did not alter the number of new carriers per annum on the spinal unit; outbreaks continued to recur on the orthopaedic and spinal units. Typing distinguished single-strain outbreaks from sporadic strains. Intervention 5 resulted in cessation of the outbreaks, which have not recurred for 2 years. Conclusions

• Infection control measures, even when augmented with additional antisepsis and disinfection, were insufficient to prevent
• recurrent MRAB outbreaks.
• Typing of MRAB was of value in detecting and controlling single-strain outbreaks.
• MRAB was most difficult to control in the spinal unit and surveillance was needed to detect new carriers early, in order to avert large outbreaks.
• MRAB was more difficult to control than methicillin-resistant Staphylococcus aureus.
• Following restriction of third-generation cephalosporins, the marked reduction in the use of infection control measures for MRAB has reduced costs and extra work for staff.