Relationship between immunosuppression and intensive care unit-acquired multidrug-resistant bacteria: a case-control study.
OBJECTIVE
To determine the relationship between immunosuppression and intensive care unit (ICU)-acquired multidrug-resistant (MDR) bacteria.


METHODS
Retrospective case-control study based on prospectively collected data.


METHODS
A 30-bed medical and surgical ICU.


METHODS
All patients hospitalized >48 hrs in the ICU were eligible during a 2-yr period.


METHODS
Immunosuppression was defined as active solid or hematologic malignancy, leucopenia, or chronic immunosuppressive treatment. MDR bacteria were defined as methicillin-resistant Staphylococcus aureus, ceftazidime- or imipenem-resistant Pseudomonas aeruginosa, Acinetobacter baumannii, Stenotrophomonas maltophilia, and extending spectrum beta-lactamase producing Gram-negative bacilli. MDR bacteria screening (nasal, anal, and axilla swabs and tracheal aspirate in intubated patients) was performed at ICU admission and weekly. Only MDR bacteria isolated >48 hrs after ICU admission were taken into account; duplicates were excluded. Isolation measures were applied in all patients at ICU admission, in patients with MDR bacteria, and in patients with immunosuppression. Immunosuppressed patients (cases) were matched (1:1) with immunocompetent patients (controls) according to all the following criteria: age +/-5 yrs, Simplified Acute Physiology Score II +/-5, duration of ICU stay +/-3 days, and category of admission (medical/surgical). Risk factors for ICU-acquired MDR bacteria were determined using univariate and multivariate analyses.


RESULTS
Of 1,065 eligible patients, nine patients were excluded for absence of MDR bacteria screening at ICU admission. One hundred thirty-three (12%) patients were immunosuppressed, and 128 (96%) of them were successfully matched. Mean time between ICU admission and first ICU-acquired MDR bacteria was 12 +/- 9 days. Incidence of MDR bacteria was significantly higher in cases than in controls (22 vs. 12 MDR bacteria/1000 ICU days, p = .004). However, immunosuppression was not independently associated with ICU-acquired MDR bacteria.Multivariate analysis identified prior antibiotic treatment and antibiotic treatment in the ICU as risk factors for ICU-acquired MDR bacteria (odds ratio [95% confidence interval] = 1.9 [1-3.6], p = .003; 11 [1.4-83], p = .02; respectively).


CONCLUSIONS
Immunosuppression is not independently associated with ICU-acquired MDR bacteria. However, infection control measures used in our ICU may have influenced this result.
Nseir
Saad
S
Intensive Care Unit, Calmette Hospital, University Hospital of Lille, France. s-nseir@chru-lille.fr
Di Pompeo
Christophe
C
Diarra
Maimouna
M
Brisson
Hélène
H
Tissier
Stéphanie
S
Boulo
Marie
M
Durocher
Alain
A
D000900:Anti-Bacterial Agents / Q000009:adverse effects*; D001424:Bacterial Infections / Q000209:etiology*; D016022:Case-Control Studies; D003428:Cross Infection / Q000209:etiology* / Q000382:microbiology; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D006801:Humans; D007165:Immunosuppression Therapy / Q000009:adverse effects*; D017053:Infection Control; D007362:Intensive Care Units; D007902:Length of Stay; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009369:Neoplasms / Q000150:complications; D012121:Respiration, Artificial / Q000009:adverse effects; D012189:Retrospective Studies; D012307:Risk Factors
D000900:Anti-Bacterial Agents