Concise Communication Results


We matched85CRPABSI casesto85casepatientswith carbapenem-susceptible P. aeruginosa (CSPA) BSI (from 491 eligible patients) and to 85 uninfected control patients (from 2,046 eligible patients). In total, 255 patients were enrolled. The study population consisted of elderly (69%) and functionally dependent (48%) indi- viduals,7 with high Charlson’s comorbidity indices (5.7 ± 3.1).8


Predictors of CRPA BSI


Most bivariate predictors associated with CRPA BSI, primarily certain demographics and background conditions, were also associated with CSPA BSI (Table 1). The distribution of the infectious syndromes was similar. Acute illness indices were more severe among patients with CRPA infections (Table 1).


Table 1. Selected Bivariable Analyses Comparing Risk Factors Associated With Resistant Case Patients, Susceptible Case Patients, and Uninfected Control Patients (n = 85 patients in each group)


Parameter


Demographics Age (years), mean ± SD Female gender


Background conditions and comorbidities Partially or fully dependent7 Impaired cognition


Permanent residency at a LTCF or direct transfer from another hospital


Ischemic heart disease Diabetes mellitus


Malignancy (in the past or active)


Charlson combined condition score,8 mean±SD


Overall immunosuppressionb


CRPA No. (%)a


CSPA No. (%)a


Uninfected Controls No. (%)a


69.7 ± 16.2 72.7 ± 13.4 66.3 ± 15.97 45 (52.9) 42 (49.4) 37 (43.5) 1.4 (0.8–3.3)


48 (56.5) 43 (50.6) 30 (35.3) 2.5 (1.3–5) 35 (41.2) 27 (31.8) 18 (21.2) 2.5 (1.3–5) 29 (34.1) 14 (16.7) 18 (21.2)


CRPA vs Uninfected CSPA vs Uninfected CRPA vs CSPA OR


OR (95% CI) P Value .17 .22 1.3 (0.7–2.5) 2 (1.0–3.3)


16 (18.8) 19 (22.4) 32 (37.6) 0.4 (0.2–0.8) 27 (31.8) 40 (47.1) 38 (44.7) 0.6 (0.3–1.1) 15 (17.6) 16 (18.8) 14 (16.5) 1.1 (0.5–2.5) 5.3 ± 2.7


6.2 ± 2.9 5.5 ± 3.5 0.77 30 (35.3) 29 (34.1) 14 (16.5) 2.5 (1.4–5)


Exposures to healthcare settings and antibiotics prior to isolation ICU stay in previous 3 mo


Invasive procedure in previous 3 mo Permanent devicesc


Received antibiotics in previous 3 mo


.006 2.0 (1.1–3.3) .005 1.7 (0.8–3.3) .06 0.8 (0.3–1.7)


.006 0.5 (0.2–0.9) .08 1.1 (0.6–2) .84 1.1 (0.5–2.5) 0.11


.005 2.5 (1.3–5) 69 (81.2) 69 (81.2) 15 (17.6) 20 (10–50)


57 (67.1) 49 (57.6) 9 (10.6) 16.7 (7.7–50) <.001 <.001


72 (84.7) 58 (68.2) 16 (18.8) 25 (11.1–50) <0.001


Time from last antibiotics, median d (range) 1.0 (0–38) 3.5 (0–76) 6 (0–76) BLBLIs in preceding 3 months Carbapenems in previous 3 mo


34 (46.6) 33 (49.3) 4 (16) 51 (69.9) 22 (32.8) 2 (8.3)


Severity of illness indices at time of isolation Hypotensiond


Mechanical ventilation


Pitt bacteremia score,10 median (range) Rapidly fatal McCabe score9


10 (5–33) (95%) P Value .005 OR (95% CI) P Value .17 .40 1.1 (0.6–2.0) .65 .04 1.3 (0.7–2.5) .44


.12 1.4 (0.8–2.5) .20 .45 2.5 (1.3–5.0)


.03 .8


.009 .70 0.9 (0.4–2)


0.8 (0.4–1.7) .60 .04 .80 .03


0.5 (0.3–1) .008 1.1 (0.6–2) .90 <.001 1.4 (0.8–2.5) .20


20 (10–50) <.001 1.0 (0.5–2.2) >.99 10 (4.5–20) <.001 2.5 (1.3–5)


72 (84.7) 66 (77.6) 23 (27.1) 14.3 (7.1–33.3) <.001 9.1 (5–20) .02


5 (1.4–14.3) 25 (5–100)


.008 <.001 43 (50.6) 21 (25.3) 12 (14.1) 6.2 (2.9–13.1) <.001 6 (0–13) 4 (0–14) 0 (0–12) 5 (1.2–25) .01


<.001 1.7 (0.7–3.3) .20 .60


5(1.6–16.7) .004 0.9 (0.5-1.7) .03


2 (0.9–4.4)


.007 .80


5.0 (2.5-10) <.001 .08 3.1 (1.6-6) <.001


55 (64.8) 47 (56.6) 11 (12.9) 12.3 (5.7–26.7) <.001 8.3 (3.9–17.9) <.001 1.5 (0.8–2.7) .20 <.001


<.001 58 (68.2) 41 (48.8) 10 (11.8) 16.7 (7.1–33.4) <.001 10.0 (3.3–16.7) <.001 2.5 (1.3–5.0)


.015 .01


Note. Significant associations are highlighted in bold. CRPA, carbapenem-resistant Pseudomonas aeruginosa; CSPA, carbapenem-susceptible P. aeruginosa; OR, odds ratio; CI, confidence


interval; SD, standard deviation; LTCF, long-term care facility. ICU, intensive care unit; BLBLI, β-lactam–β-lactamase inhibitor combination; BSI, blood stream infection. aValid percent: count divided by the total number of valid (ie, nonmissing) observations. bImmunosuppression includes any of the following: neutropenia at culture date (<500 neutrophils/mm3), exposure to glucocorticoids in the previous month, chemotherapy in the previous


3 months, radiotherapy, posttransplantation of any kind, anti-TNF-α (tumor necrosis factor α) therapy in the previous 3 months, or (7) human immunodeficiency virus (HIV) infection. cPermanent devices included tracheostomies, percutaneous endoscopic gastrostomy, pacemakers, central lines, urinary catheters, external orthopedic devices, drains. Not included: internal


stents, prosthetic heart valve, and prosthetic joints. Permanent devices were in place at least 48 hours prior to the isolation. dHypotension was defined as a systolic blood pressure <90 mmHg, or administration of intravenous vasopressors, or an acute drop in systolic blood pressure >30 mmHg and/or diastolic blood pressure >20 mm Hg in the 48 hours preceding the culture time.


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