Clinical outcomes of health-care-associated infections and antimicrobial resistance in patients admitted to European intensive-care units: a cohort study.
BACKGROUND
Patients admitted to intensive-care units are at high risk of health-care-associated infections, and many are caused by antimicrobial-resistant pathogens. We aimed to assess excess mortality and length of stay in intensive-care units from bloodstream infections and pneumonia.


METHODS
We analysed data collected prospectively from intensive-care units that reported according to the European standard protocol for surveillance of health-care-associated infections. We focused on the most frequent causative microorganisms. Resistance was defined as resistance to ceftazidime (Acinetobacter baumannii or Pseudomonas aeruginosa), third-generation cephalosporins (Escherichia coli), and oxacillin (Staphylococcus aureus). We defined 20 different exposures according to infection site, microorganism, and resistance status. For every exposure, we compared outcomes between patients exposed and unexposed by use of time-dependent regression modelling. We adjusted results for patients' characteristics and time-dependency of the exposure.


RESULTS
We obtained data for 119 699 patients who were admitted for more than 2 days to 537 intensive-care units in ten countries between Jan 1, 2005, and Dec 31, 2008. Excess risk of death (hazard ratio) for pneumonia in the fully adjusted model ranged from 1·7 (95% CI 1·4-1·9) for drug-sensitive S aureus to 3·5 (2·9-4·2) for drug-resistant P aeruginosa. For bloodstream infections, the excess risk ranged from 2·1 (1·6-2·6) for drug-sensitive S aureus to 4·0 (2·7-5·8) for drug-resistant P aeruginosa. Risk of death associated with antimicrobial resistance (ie, additional risk of death to that of the infection) was 1·2 (1·1-1·4) for pneumonia and 1·2 (0·9-1·5) for bloodstream infections for a combination of all four microorganisms, and was highest for S aureus (pneumonia 1·3 [1·0-1·6], bloodstream infections 1·6 [1·1-2·3]). Antimicrobial resistance did not significantly increase length of stay; the hazard ratio for discharge, dead or alive, for sensitive microorganisms compared with resistant microorganisms (all four combined) was 1·05 (0·97-1·13) for pneumonia and 1·02 (0·98-1·17) for bloodstream infections. P aeruginosa had the highest burden of health-care-acquired infections because of its high prevalence and pathogenicity of both its drug-sensitive and drug-resistant strains.


CONCLUSIONS
Health-care-associated bloodstream infections and pneumonia greatly increase mortality and pneumonia increase length of stay in intensive-care units; the additional effect of the most common antimicrobial resistance patterns is comparatively low.


BACKGROUND
European Commission (DG Sanco).
Public Health and Surveillance Department, Scientific Institute for Public Health, Brussels, Belgium. mlambert@wiv-isp.be
Marie-Laurence
ML
Lambert
Carl
C
Suetens
Anne
A
Savey
Mercedes
M
Palomar
Michael
M
Hiesmayr
Ingrid
I
Morales
Antonella
A
Agodi
Uwe
U
Frank
Karl
K
Mertens
Martin
M
Schumacher
Martin
M
Wolkewitz
D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D016470:Bacteremia / Q000188:drug therapy / Q000382:microbiology* / Q000401:mortality; D001419:Bacteria / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification; D015331:Cohort Studies; D003428:Cross Infection / Q000188:drug therapy / Q000382:microbiology* / Q000401:mortality; D024881:Drug Resistance, Bacterial; D005060:Europe; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D018410:Pneumonia, Bacterial / Q000188:drug therapy / Q000382:microbiology* / Q000401:mortality; D016896:Treatment Outcome
D000900:Anti-Bacterial Agents