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Table 4 Risk factors for P. aeruginosa acquisition in the ICU (n = 126)

From: Pseudomonas aeruginosa acquisition on an intensive care unit: relationship between antibiotic selective pressure and patients' environment

  Univariate analysis Multivariate analysis
Risk factor OR (95% CI) P OR (95% CI) P
SAPS II     
   ≥43 (vs. <43) 2.54 (0.89 to 7.24) 0.08 *  
Age     
   ≥70 years (vs. <70) 4.61 (1.67 to 12.72) 0.14 *  
Nasogastric tube     
   Equal to or more than nine cumulated days since admission (vs. less than nine days) 7.66 (2.88 to 20.36) <0.0001 7.72 (2.32 to 25.70) 0.001
Antibiotic treatment not active against P. aeruginosa     
   More than three days (vs. zero to two days) 2 (0.76 to 5.27) 0.16 ***  
Antibiotic treatment active against P. aeruginosa**     
   per cumulated day since admission 1.02 (0.95 to 1.10) 0.54 ****  
Previous patient-induced environmental pressure     
   Equal to or more than one colonized patient on the same ward on the previous day (vs. zero) 4.91 (1.47 to 16.39) 0.01 ***  
   Equal to or more than one colonized patient on the ICU on the previous day (vs. zero) 1.14 (0.27 to 4.90) 0.86 ****  
Previous tap water-induced environmental pressure     
   Equal to or more than one colonized tap water on the same ward on the previous day (vs. zero) 2.37 (0.96 to 5.89) 0.06 $  
   Equal to or more than one colonized tap water on the ICU on the previous day (vs. zero) 3.79 (1.26 to 11.44) 0.02 1.99 (0.67 to 5.88) 0.21
   Equal to or more than one colonized tap water in shared rooms on the previous day (vs. zero) 4.63 (1.37 to 15.65) 0.01 3.07 (0.93 to 10.16) 0.07
Interaction between previous patient-induced environmental pressure and inactive antibiotics:     0.03$$
   If equal to or more than three days of inactive antibiotics    1  
- no colonized patient on the same ward on the previous day    10.26 (1.83 to 57.43) 0.01
- equal to or more than one colonized patient on the same ward on the previous day     
   If zero to two days of inactive antibiotics     
- no colonized patient on the same ward on the previous day    1  
- equal to or more than one colonized patient on the same ward on the previous day    1.00 (0.26 to 3.87) 0.99
  1. *Factors removed by stepwise forward procedure.
  2. **Log-linearity was assumed for this factor.
  3. ***Factors included in the interaction.
  4. ****Not statistically eligible by univariate analysis (P > 0.20).
  5. $Not included in multivariate analysis for colinearity with tap water in the ICU.
  6. $$P for overall interaction.