1429. Rise in MICs for Colistin in Multi-drug Resistant Gram Negative Bacteria in Community Hospitals
Session: Poster Abstract Session: Epidemiology of Multiple Drug-Resistant Gram Negative Rods
Saturday, October 20, 2012
Room: SDCC Poster Hall F-H
  • IDSA Poster 2012.pdf (1.7 MB)
  • Background: The increase in multi-drug resistant gram negative bacteria (MDRGNB) in our institutions has led to increased utilization of colistin. Concern exists that MDRGNB susceptibility decreases with increasing colistin exposure. Previously we reported an increase in minimum inhibitory concentration (MICs) of MDRGNB to colistin by E test (bioMerieux,Durham,NC) over a 36 month period in conjunction with an increase in the mean MIC of sensitive organisms from 0.5 mcg/ml to 1mcg/ml .  We now report on the subsequent 8 months experience at 2 community hospitals.

    Methods: MDRGNB susceptibilities colistin based on E test results tested from 8/08 to 7/09 (T1) , 8/09 to 7/10 (T2), 8/10 to 7/11 (T3) and 8/11 to 4/12 (T4) were compared. Isolates that were resistant to all but one other class of antibiotics (excluding colistin) were tested for colisten susceptibility. Date of isolation, source site, and MIC to colistin and other antibiotics were recorded. Colistin utilization was obtained from pharmacy records for both study periods.

    Results: Approximately 339 isolates met study criteria over the 44 month period and were included in the analysis. The two most prevalent organisms were Acinetobacter baumanii  (n=148) and Klebsiella pneumoniae (n=164) . Percentage of Acinetobacter baumanii  organisms with an MIC <2mcg/ml for T1 (100%),T2 (93%), T3 (93%),T4 (94%) . Percentage Klebsiella pneumoniae with an MIC<2mcg/ml for T1 (99%), T2 (84%), T3 (70%), T4 (48%). Sensitivity to tigecycline and gentamycin predominated among these isolates.. Colistin utilization increased by 58% between T1 and T4 study periods

    Conclusion: In a community hospital setting, increasing MICs among MDRGNB were observed over four study periods . During the most recent study period (T4) there was a decrease in the percentage of organisms with an MIC less than 2mcg/mL. Increasing MICs were more commonly seen among K. pneumoniae isolates, whereas MICs among A. baumanii remained steady.  Clinicians should be aware of increasing colistin MICs among MDRGNR in community hospitals with increasing colisten utilization.

    Kevin McDonough, BS, PharmD , MPA, East Orange General Hospital, East Orange, NJ; Cardinal Hlth. Pharm. Services, East Orange, NJ, Gerry Somera, BSMP, Lab, East Orange General Hospital, East Orange, NJ, Bhavna Desai, BS, MT(ASCP), CIC, St Mary's Hospital, Passaic, NJ and Diana Finkel, DO, St. Mary's Hospital, Passaic, NJ


    K. McDonough, None

    G. Somera, None

    B. Desai, None

    D. Finkel, None

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