Publications
| A Poly-Clonal DHA-1 Outbreak Involving Klebsiella pneumoniae and Escherichia coli in a Toronto Community Hospital |
Authors: B. M. WILLEY, D. BOYD, D. FAWCETT, N. GILLANI, J. PETO, K. PIKE, O. IMAS, M. LUM, C. LAROCQUE, I. DAVIS, M. MULVEY, A. MCGEER;
Mount Sinai Hosp., Toronto, Canada, Natl. Microbiol. Lab., Winnipeg, Canada, Centenary Hosp., Toronto, Canada.
Background: During a survey for Class A ESBL in a chronic care ward, a cluster of ciprofloxacin- and oxyimino-β-lactam-resistant (bla-R) K. pneumoniae (KP) with an inducible Class C β-lactamase (ind-C) phenotype was identified. Further screening found new patients (pts) who were co-colonized with ind-C E. coli (EC).
Method: Laboratory records were reviewed back to 2001 for potential ind-C strains. KP and EC from clinical specimens and rectal swabs cultured to MacConkey agar with 2mg/L cefpodoxime (POD) were identified by Vitek. Phenotypic prediction of bla-R genotype was by Disk Diffusion Test with POD, ceftazdime, ceftriaxone and aztreonam placed 15mm from clavulanate and cefoxitin disks, with observation for blunted D-zones typical of ind-C. All ind-C strains were typed by XbaI PFGE and select strains sequenced for bla-R genes.
Results: From Jan-May 2006, 16 pts from 1 ward were identified with ind-C KP; 6 (37.5%) also carried ind-C EC; 1 pt was bacteremic, the rest colonized. One of these pts had carried ind-C KP and EC intermittently since 2002. This pt’s 2002 roommate had been colonized with the same ind-C KP and EC strains (by PFGE) since 2001. The ind-C KP and ind-C EC from this pt in 2001 and 2002 were highly related to 13/16 KP and 2/6 EC from 2006. 3 cases in the 2006 cluster carried distinct ind-C KP and 4 carried distinct ind-C EC. Sequencing confirmed blaDHA-1 in the 2001 KP, and in 6 KP and 1 EC from 2006. PCR found orf513 in the initial 2001 KP, suggesting that DHA-1 may be located in a class 1 integron.
Conclusions: Both the ind-C KP and EC were persistent colonizers (>4 yrs) in one pt, resulting in transmission to multiple pts and a bacteremic infection in 2006. The blaDHA-1 apparently transferred in vivo from the initial KP or EC to multiple unrelated KP and EC. To our knowledge, this is the first poly-clonal DHA-1 outbreak to be reported in North America.
Presented At:
46th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy, San Francisco, CA, 9/27/2006.
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1999 Microbiology Department, Mount Sinai Hospital, Toronto, ON, Canada.
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