Influence of bacterial resistance on mortality in intensive care units: a registry study from 2000 to 2013 (IICU Study)

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Summary

Background

Bacterial resistance to antibiotics is a daily concern in intensive care units. However, few data are available concerning the clinical consequences of in-vitro-defined resistance.

Aim

To compare the mortality of patients with nosocomial infections according to bacterial resistance profiles.

Methods

The prospective surveillance registry in 29 French intensive care units (ICUs) participating during the years 2000–2013 was retrospectively analysed. All patients presenting with a nosocomial infection in ICU were included.

Findings

The registry contained 88,000 eligible patients, including 10,001 patients with a nosocomial infection. Among them, 3092 (36.7%) were related to resistant micro-organisms. Gram-negative bacilli exhibited the highest rate of resistance compared to Gram-positive cocci (52.8% vs 48.1%; P < 0.001). In-hospital mortality was higher in cases of patients with antibiotic-resistant infectious agents (51.9% vs 45.5%; P < 0.001), and critical care length of stay was longer (33 ± 26 vs 29 ± 22 days; P < 0.001). These results remained significant after SAPS II matching (P < 0.001) and in the Gram-negative bacilli and Gram-positive cocci subgroups. No difference in mortality was found with respect to origin prior to admission.

Conclusion

Patients with bacterial resistance had higher ICU mortality and increased length of stay, regardless of the bacterial species or origin of the patient.

Introduction

As a cause of multi-organ failure in septic shock, or a precipitating event over the course of severe illness, infection is an independent risk factor of mortality in intensive care units (ICUs) and thus a daily concern. Furthermore, healthcare-associated infections have substantial effects on morbidity and length of hospital stay and represent a major public health issue [1], [2], [3], [4]. Consequently, wide international prevention programmes have been implemented to specifically target these infections [5]. However, despite these efforts, the nosocomial infection incidence seems to be rising [1], [6].

The problem is compounded by bacterial resistance to antibiotics, leading to delays in appropriate antibiotic therapy and raising the question of a possible overmortality [1], [7]. Indeed, ICU patients are not only extremely vulnerable but also the most prone to infections related to resistant bacteria as a result of antibiotic misuse or overuse, long hospitalizations, and the rapid spread of resistant strains from abroad [8], [9], [10], [11], [12]. Improvements in infection management tend to focus on antibiotic resistance, as reflected by recent national campaigns in many countries [13], [14].

Thus, surveillance and control networks have been implemented worldwide, such as the US Centers for Disease Control and Prevention or the Centres de Coordination de la Lutte contre les Infections Nosocomiales (CCLIN) in France. The latter prospectively includes demographic, bacteriological, and clinical data from a wide representative sample of ICUs.

However, only sparse data are available concerning the role of bacterial resistance, and conflicting evidence exists concerning its impact on mortality: a recent literature review reported studies in which resistant bacterial strains were associated with increased mortality and many others in which mortality was independent of antibiotic resistance [15], [16], [17].

Consequently, the aim of this study was to compare the mortality of hospital-acquired infections with respect to bacterial resistance to antibiotics over an extended period of 13 years in 29 French ICUs in the CCLIN Network. We hypothesized that patients with infections with resistant bacteria in ICU are associated with increased mortality rate and longer hospital stays than those with susceptible strains.

Section snippets

Ethics, consent, and permissions

Following institutional review board agreement (Ethics Committee for Research in Anesthesiology and Intensive Care, French Society of Anesthesiology and Intensive Care, 74 rue Raynouard, 75016 Paris, France; Ref. IRB 00010254-2016-119), prospective data were collected from 2000 to 2013 from a database involving 29 French ICUs included in a specific network aimed at studying hospital-acquired infections (Centres de Coordination de la Lutte contre les Infections Nosocomiales Ouest: CCLIN Ouest)

Entire cohort

From 2000 to 2013, data from 87,931 patients were collected, including 10,001 with a hospital-acquired infection. There were 8428 cases with an identified pathogen, 1121 cases without a pathogen being detected, and 428 cases with missing data). The primary patient demographics and characteristics are reported in Table I. Multivariate analysis on the entire population identified SAPS II score (odds ratio: 1.24, 95% confidence interval (CI): 1.20–1.29), immunodepression (1.14; 1.05–1.23), trauma

Discussion

The present study shows that patients with infections are associated with increased mortality in ICU. Among infected patients, Gram-negative bacilli were responsible for a higher mortality and longer survivor-LOS than were Gram-positive cocci. Patients with bacterial resistance were associated with increased mortality and longer ICU survivor-LOS.

Sepsis is a known risk factor for ICU mortality, yet the impact of antibiotic resistance on mortality has been debated [1], [16], [17]. Among

Conflict of interest statement

None declared.

Funding sources

None.

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    This work is dedicated to the late Dr Nadine Garreau.

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