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Multidrug-resistant Acinetobacter baumannii susceptible only to colistin outbreak in a cardiac surgical intensive care unit

Objectives

Gram-negative bacilli including multidrug-resistant Acinetobacter baumannii (MDR-AB) are responsible for severe ICU-acquired infections, mainly pneumonia and bacteraemia. The aim of this study was to determine the incidence and mortality of this multiresistant strain of Acinetobacter in patients undergoing cardiac surgery, to elucidate the effectiveness of treatment with colistin and to identify whether additional measures were able to prevent and control the dissemination of MDR-AB isolates in our institution.

Methods

A total of 1,451 patients attended the surgical ICU (SICU) after cardiovascular surgery from 1 September 2005 to 31 August 2006. We reviewed the prophylactic measures of the SICU and tried to identify epidemiological links between MDR-AB-infected patients. We implemented a two-scale multiple program. Scale 1 included classical infection control measures (that is, strict contact and droplet isolation, surveillance of throat, nasal and anal flora for MDR pathogens on all patients transferred from other hospitals, separate nursing staff for each infected or colonized case and strict antibiotic policy), while Scale 2 referred to geographic isolation of MDR-AB cases with exclusive medical and nursing personnel, use of separate supplies and facilities and intense environmental surveillance.

Results

Fifteen patients were infected by MDR-AB, of which 13 presented respiratory tract infection, one suffered deep surgical site infection and bacteraemia and one from catheter-related infection. They were all treated with intravenous and aerolized colistin in combination with rifampicin or ampicillin and sulbactam. Despite significant 'in vitro' activity of colistin against this virulent organism and its acceptable safety profile, results were discouraging as only 13% survived. In fact, cure or clinical improvement was observed only in four patients (27%) while 11 patients (73%) developed sepsis and multiple organ failure.

Scale 1 measures were implemented for the whole 12-month period while Scale 2 for two separate 3-week periods. Following this infection control strategy we achieved intermittent eradication of the pathogen during a 12-month period with continuous function of the SICU.

Conclusion

Increasing prevalence of MDR-AB in ICU patients demands installation of strict screening and contact precautions. Due to significant mortality of MDR-AB-infected patients, additional measurements like geographic isolation of all positive cases, exclusive medical and nursing personnel, use of separate supplies and facilities and intense environmental surveillance is highly recommended.

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Papadopoulos, K., Tasouli, A., Douka, E. et al. Multidrug-resistant Acinetobacter baumannii susceptible only to colistin outbreak in a cardiac surgical intensive care unit. Crit Care 11, P99 (2007). https://doi.org/10.1186/cc5259

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Keywords

  • Colistin
  • Sulbactam
  • Infection Control Measure
  • Nursing Personnel
  • Acceptable Safety Profile