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Table 1 Bivariate assessment of characteristics associated with methicillin-resistant Staphylococcus aureus (MRSA) acquisition among cases and controls

From: Colonization with antibiotic-susceptible strains protects against methicillin-resistant Staphylococcus aureus but not vancomycin-resistant enterococci acquisition: a nested case-control study

Variable

Controls a

N (%)

Cases a

N (%)

Odds ratio b

(95% CI)

P-value

Total

248 (100%)

244 (100%)

  

Age

   

0.47

   < 45

40 (16%)

38 (16%)

1.0, reference

 

   45 to < 55

31 (13%)

26 (11%)

0.93 (0.46, 1.88)

 

   55 to < 65

59 (24%)

54 (22%)

1.12 (0.62, 2.04)

 

   65 to < 75

54 (22%)

68 (28%)

1.56 (0.85, 2.85)

 

   75+

64 (26%)

58 (24%)

1.10 (0.60, 2.01)

 

Male gender

146 (59%)

140 (57%)

1.11 (0.77, 1.59)

0.58

Comorbidities

    

   Diabetes mellitus

71 (29%)

70 (29%)

1.07 (0.71, 1.61)

0.76

   End-stage renal disease

12 (5%)

20 (8%)

1.67 (0.79, 3.53)

0.18

   End-stage liver disease

6 (2%)

12 (5%)

2.20 (0.80, 6.08)

0.13

   Solid cancer

63 (25%)

64 (26%)

1.07 (0.67, 1.69)

0.78

   Hematologic malignancy

13 (5%)

9 (4%)

0.71 (0.29, 1.75)

0.46

ICU Type

   

0.26

   Medical

82 (33%)

61 (25%)

0.67 (0.33, 1.35)

 

   Surgical

166 (67%)

183 (75%)

  

ICU admit to negative swab

   

< .0001

   1 day

183 (74%)

82 (34%)

1.0, reference

 

   2 days

50 (20%)

41 (17%)

1.81 (1.11, 2.97)

 

   ≥ 3 days

15 (6%)

121 (50%)

17.82 (9.77, 32.49)

 

Active wound

181 (73%)

193 (79%)

1.20 (0.76, 1.89)

0.43

Active rash

30 (12%)

33 (14%)

1.18 (0.69, 2.02)

0.55

Surgical procedures c

207 (83%)

196 (80%)

0.72 (0.45, 1.17)

0.19

Non-surgical procedures c

    

   Intubation

213 (86%)

238 (98%)

6.09 (2.48, 14.94)

< .0001

   Central line

192 (77%)

214 (88%)

2.10 (1.27, 3.48)

0.004

   Arterial line

226 (91%)

232 (95%)

1.78 (0.84, 3.78)

0.13

   Chest tube

94 (38%)

86 (35%)

0.87 (0.54, 1.40)

0.57

   Surgical drain

108 (44%)

98 (40%)

0.85 (0.57, 1.25)

0.41

Labs c

    

   Albumin < 2

21 (9%)

34 (14%)

1.60 (0.89, 2.88)

0.11

   Creatinine > 2

52 (21%)

68 (28%)

1.54 (0.99, 2.37)

0.05

Colonization pressure

   

0.08

   0

9 (4%)

15 (6%)

1.33 (0.52, 3.38)

 

   1 to < 4

72 (29%)

51 (21%)

0.54 (0.33, 0.90)

 

   4 to < 8

66 (27%)

54 (22%)

0.64 (0.39, 1.05)

 

   8 to < 12

42 (17%)

42 (17%)

0.76 (0.44, 1.33)

 

   12+

59 (24%)

82 (34%)

1.0, reference

 

Sensitive strain carrier d

49 (20%)

30 (12%)

0.55 (0.33, 0.91)

0.02

Antibiotic utilization c

    

   Aminoglycoside

33 (13%)

24 (10%)

0.71 (0.40, 1.26)

0.24

   Clindamycin

20 (8%)

18 (7%)

0.94 (0.48, 1.85)

0.87

   Macrolide

26 (10%)

26 (11%)

1.07 (0.59, 1.93)

0.83

   Fluoroquinolone

146 (59%)

193 (79%)

2.91 (1.91, 4.42)

< .0001

   First generation Cephalosporin

101 (41%)

107 (44%)

0.97 (0.65, 1.46)

0.89

   Second generation Cephalosporin

3 (1%)

6 (2%)

1.93 (0.47, 8.03)

0.36

   Third generation Cephalosporin

72 (29%)

88 (36%)

1.49 (1.01, 2.21)

0.05

   Broad spectrum penicillin

0 (0%)

6 (2%)

  

   Carbapenem

6 (2%)

11 (5%)

2.13 (0.76, 5.96)

0.15

   Anti-MRSA antibiotics e

159 (64%)

182 (75%)

1.92 (1.26, 2.92)

0.002

   Other MRSA antibiotics f

10 (4%)

4 (2%)

0.40 (0.12, 1.31)

0.13

  1. aCases and controls had a negative bilateral nares surveillance swab and no prior history of MRSA upon intensive care unit admission
  2. bAccounted for clustering by intensive care unit ward
  3. cAssessed during the two weeks prior to the initial negative surveillance culture through the period encompassing the subsequent negative or positive surveillance or clinical culture for MRSA
  4. dSensitive strain refers to methicillin-sensitive Staphyloccocus aureus
  5. eAnti-MRSA antibiotics include vancomycin, linezolid, synercid, daptomycin, and tigecycline
  6. fOther MRSA antibiotics include doxycycline, bactrim, and rifampin
  7. CI, confidence interval.
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