News Release

Health-care-acquired infections greatly increase risk of dying in intensive care, but additional impact of antimicrobial resistance is small

Peer-Reviewed Publication

The Lancet_DELETED

Critically ill patients with bloodstream infections and pneumonia face a greatly increased risk of dying, but resistance to the most common antimicrobial agents has only a small additional effect on patient outcome, according to a Europe-wide study that analysed health-care-associated infections in more than 500 intensive care units (ICUs) in ten countries. These findings, published Online First in The Lancet Infectious Diseases, also report similar length of stay in ICUs for patients infected with resistant and sensitive microorganisms.

Intensive care patients are particularly vulnerable to picking up infections in hospital because of their poor health—up to 10% acquire a severe infection such as pneumonia or bloodstream infection. But whether infections directly worsen outcomes for patients, or if patients with infections are just more severely ill than those without infections is unclear. Additionally, widespread use of antibiotics and high prevalence of antimicrobial resistance put patients at high risk of infection with resistant pathogens. What resistance adds to the risk of infection is also unclear.

In this study, an international team led by Marie-Laurence Lambert from the Scientific Institute of Public Health, Brussels, Belgium, assessed the effect of infections and antimicrobial resistance on outcomes for patients with bloodstream infections and pneumonia caused by four of the most common microorganisms (StaphylococcuS aureus, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa) in ICUs.

The researchers examined data for 119 699 patients staying for more than 2 days in 537 ICUs in ten European countries between January 2005 and December 2008. They evaluated the associations between different infection sites, microorganisms, resistance status, and risk of death and extended length of stay in ICUs, with adjustment for patients' characteristics and timing of infection. For every infection, outcomes between patients exposed were compared with those who were unexposed (the rest of the cohort).

Overall estimates (combining all four microorganisms), suggest that infection with pneumonia doubles the likelihood of death, and bloodstream infections treble the risk. Having pneumonia also increases length of stay in ICUs.

Importantly, the presence of resistance to common antimicrobial agents was estimated to have just a small additional effect on patient outcome, increasing the likelihood of death by a further 20%. Antimicrobial resistance did not significantly increase the length of stay in ICUs*.

Interestingly, findings also showed that P aeruginosa rather than S aureus cause the greatest burden of health-care-related infections in ICUs because of the high pathogenicity of both its sensitive and resistant strains.

The authors conclude: "Common patterns of antibiotic resistance made only a small contribution to the overall effect of these infections…Prevention of health-care-related infections needs to be reasserted and emphasised as an absolute priority."

In a Comment, Jean-Louis Vincent from Erasme University Hospital, Brussels, Belgium says: "Microbial resistance does matter, and the results of this study should not discourage attempts to control multidrug-resistant bacteria (MRB)."

He cautions: "MRBs continue to be a threat, and one that will probably become more prevalent in the future. Present antibiotics have restricted effectiveness against resistant infections, and there are few new products in the development pipeline. We urgently need new antibiotics to be able to appropriately manage patients with such infections."

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Professor Jean-Louis Vincent, Erasme University Hospital, Brussels, Belgium. T) +32 2 555 3380 E) jlvincen@ulb.ac.be

For full Article and Comment, see: http://press.thelancet.com/tlidhcai.pdf

Notes to Editors: * The authors recognize that the results do not necessarily apply to more severe patterns of resistance causing virtually untreatable infections, which are still rare and for that reason do not have (at the moment) a significant public health impact.

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