Impact of Multiresistance of Gram-negative Bacteria in Bloodstream Infection on Mortality Rates and Length of Stay

Background: Bloodstream infections (BSI) with gram-negative bacteria (GNB) are one of the most serious infections in the hospital setting, a situation compounded by the increasing antibiotic resistance of gram-negative bacteria causing BSI. The aim of the study was to assess the impact of antibiotic multiresistance of GNB in BSI on mortality rates and length of stay (LOS). Materials and Methods: The setting was the University Hospital Aachen, a 1,500-bed tertiary-care hospital with over 100 ICU beds providing maximal medical care in all disciplines. We performed a 5-year hospital-wide matched cohort study (January 1996 to February 2001) in which 71 cases and 99 controls were enrolled. Matching criteria were sex, age and GNB isolated in blood cultures. Multiresistance was defined as resistance against at least two different classes of antibiotics such as penicillins (+ β -lactamase-inhibitor), third-generation cephalosporins, fluoroquinolones or carbapenems. Results: BSI were mainly nosocomially acquired, and cases of BSI with multiresistant bacteria were associated with a higher mortality (p = 0.0418) and a prolonged LOS in the intensive care unit (ICU) (p = 0.0049). Risk factors for BSI with multiresistant GNB were antibiotic treatment (p = 0.0191) and mechanical ventilation (p = 0.0283). Conclusion: Multiresistance of GNB causing BSI was associated with higher mortality rates and longer LOS in ICU. The initial antibiotic therapy was significantly more often inadequate and might have had an impact on overall mortality. Thus, an effective strategy to administer an appropriate initial empirical antibiotic therapy, especially in patients with risk factors, must be sought. Moreover, the overall usage of antimicrobials must be limited and infection control guidelines should be followed to reduce the emergence and transmission of multiresistant GNB.