1403. Sensitivity of Multidrug-Resistant Gram-Negative Organism Surveillance Testing in the Intensive Care Unit
Session: Poster Abstract Session: Epidemiology of Multiple Drug-Resistant Gram Negative Rods
Saturday, October 20, 2012
Room: SDCC Poster Hall F-H
  • Slide1.PNG (416.3 kB)
  • Background: Identification of inpatients colonized with multidrug-resistant (MDR) Gram-negative bacteria (GNB) is important for infection control. Little is known about the sensitivity of routine surveillance for MDR GNBs among adult inpatients.

    Methods: We determined the sensitivity of routine surveillance testing for MDR GNB in the Intensive Care Units (ICU) of 4 affiliated study hospitals over 2.5 years. Once a month, every ICU patient was tested for MDR GNB-colonization with swabs of the throat, axillae, and perirectal area. Microbiological databases were used to identify patients with a positive clinical culture for MDR GNB. The proportion of patients with a positive clinical culture for MDR GNB who had a positive surveillance test was calculated. Chi-square test was used to compare proportions.

    Results: There were 100 instances in which a patient who had undergone a surveillance test had a positive clinical culture for a unique MDR GNB. The sensitivity of the surveillance test for detecting the same MDR GNB which grew in clinical culture was 41% (95% CI, 31%-51%). The sensitivity for detecting any MDR GNB (not necessarily the same MDR GNB in clinical culture) was 56% (95% CI, 46%-66%). Sensitivity varied according to length of time from clinical culture (Table). Sensitivity did not significantly vary based on organism in clinical culture. Treatment with any of the following antibiotics within the 30 days prior to the surveillance test decreased its sensitivity: carbapenems (34% vs. 53%, p=0.05), quinolones (36% vs. 59%, p=0.02), and tigecycline (20% vs. 52%, p=0.05).

    Conclusion: Surveillance tests performed before clinical culture predict a notable number of positive clinical cultures for MDR GNB. Treatment with certain antibiotics decreases the sensitivity of the test.

    Table: Sensitivity of Surveillance Test for MDR GNB Based on Length of Time from Positive Clinical Culture

    Timing of Surveillance Test in Relation to Positive Clinical Culture for MDR GNB

    % MDR GNB Detected on Surveillance Test (95% CI)

    >365 Days Prior

    43% (10-82%)

    91-365 Days Prior

    19% (6-38%)

    31-90 Days Prior

    53% (27-79%)

    1-30 Days Prior

    58% (37-77%)

    0-30 Days After

    62% (45-78%)

    31-90 Days After

    79% (49-95%)

    91-365 Days After

    69% (39-91%)

    >365 Days After

    40% (16-68%)

    Jessica P. Ridgway, MD1, Lance R. Peterson, MD2, Richard Thomson Jr., PhD2, Becky A. Miller, MD2, Marc-Oliver Wright, MT(ASCP), MS, CIC 2 and Ari Robicsek, MD2, (1)University of Chicago, Chicago, IL, (2)NorthShore University HealthSystem, Evanston, IL


    J. P. Ridgway, None

    L. R. Peterson, None

    R. Thomson Jr., None

    B. A. Miller, None

    M. O. Wright, None

    A. Robicsek, None

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