Evaluation of interspecies plasmid transfer and comparison with hospital epidemiology data

Authors

• RA Weingarten
• CA Hardiman
• AJ Mathers
• JP Dekker
• S Conlan
• TN Palmore
• JA Segre
• KM Frank

Abstract

Objective: Carbapenem-producing organisms have spread worldwide and cause significant morbidity. Horizontal gene transfer of carbapenemases may play a role in this spread. Given that conjugation is influenced by a number of factors, we sought to perform a systematic analysis of blaKPC encoding plasmid transfer into multiple species using hospital isolates. Methods: Plasmids were isolated from patient donor strains from the NIH and University of Virginia and a subset were tagged with GFP and electroporated into a K. pneumoniae patient isolate cured of its blaKPC plasmid. Broth and filter matings were performed, and transconjugants were isolated on selective media. Plasmids tested included those found in multiple species during hospital surveillance. Results: Transfer frequency was dependent on the recipient, temperature, substratum, and the specific plasmid. pKPC-47e was extremely attenuated in conjugation efficiency across all conditions tested compared to pKpQIL. In vitro studies showed a low conjugation efficiency for pKPC_UVA01 into recipient strains that readily accepted pKpQIL, despite its presence in multiple clinical strains. Conclusions: The efficiency of conjugation into patient Enterobacteriaceae isolates and a common lab cloning E. coli strain ranged widely from 10-2 CFU transconjugants/CFU recipients to undetectable, without a clear correlation with the pattern of spread suggested during two hospital outbreaks. In vitro models may not faithfully predict plasmid mobilization until we better understand the most important variables that affect conjugation efficiency. Additional studies will be valuable in assessing the role of conjugation in the worldwide spread of resistance.

Scientific Focus Area: Microbiology and Infectious Diseases

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