248. Continuing Rise in MICs for Colistin in Multi-drug Resistant Gram Negative Bacteria in Community Hospitals
Session: Poster Abstract Session: Antimicrobial Susceptibility and Resistance
Friday, October 21, 2011
Room: Poster Hall B1
  • McDonough _Rise in MICs posterCOLISTIN 2011_09_12_11 vFINAL.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 20 month period in conjunction with an increase in colistin utilization .  We now report on the subsequent 12 months experience.

    Methods: MDRGNB susceptibilities colistin based on E test results tested at two New Jersey community hospitals from 8/2008 to 3/2010 (T1)  and from 4/2010 to 5/2010 (T2) were compared.  Records were retrospectively reviewed. Isolates were tested against colistin if they were resistant to all but one other class of antibiotics (excluding colistin). Date of isolation, source site, and MIC to colistin and other antibiotics were noted for each organism. Colistin utilization was obtained from pharmacy records for both study periods.

    Results: 200 isolates met study criteria during T1 and  83 during T2. 4% of organisms from T1 and 12% from T2 had MICs > than 2mcg/mL. Tigecycline and gentamycin were the other antibiotics most commonly reported as sensitive. The mean MIC for sensitive organisms during T1 was 0.5 and increased to 1 for T2. There was no increase in colistin utilization between the two study periods.

    Conclusion: In a community hospital setting, a trend towards increasing MICs to colistin was found between study periods. There was an increase in the number of resistant organisms isolated as well as a rise in the mean MIC of sensitive organisms during the second study period. Though overall isolation of organisms with MIC > than 2mcg/mL was still low at 12%, there were 3x as many resistant organisms during T2 than T1.  Clinicians should be aware of increasing colistin MICs among MDRGNR in community hospitals.

    Subject Category: A. Antimicrobial agents and Resistance

    Kevin McDonough, BS, PharmD , MPA, East Orange General Hospital, East Orange, NJ; Cardinal Hlth. Pharm. Services, East Orange, NJ, Bhavna Desai, MT, St Mary's Hospital, Passaic, NJ, Josefa Deguino, MT, Microbiology, East Orange General Hospital, East Orange, NJ and Diana Finkel, DO, St. Mary's Hospital, Fair Lawn, NJ


    K. McDonough, None

    B. Desai, None

    J. Deguino, None

    D. Finkel, None

    Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.