Horizontal Transfer of Carbapenemase-Encoding Plasmids and Comparison with Hospital Epidemiology Data.
Carbapenemase-producing organisms have spread worldwide, and infections with these bacteria cause significant morbidity. Horizontal transfer of plasmids carrying genes that encode carbapenemases plays an important role in the spread of multidrug-resistant Gram-negative bacteria. Here we investigate parameters regulating conjugation using an Escherichia coli laboratory strain that lacks plasmids or restriction enzyme modification systems as a recipient and also using patient isolates as donors and recipients. Because conjugation is tightly regulated, we performed a systematic analysis of the transfer of Klebsiella pneumoniae carbapenemase (blaKPC)-encoding plasmids into multiple strains under different environmental conditions to investigate critical variables. We used four blaKPC-carrying plasmids isolated from patient strains obtained from two hospitals: pKpQIL and pKPC-47e from the National Institutes of Health, and pKPC_UVA01 and pKPC_UVA02 from the University of Virginia. Plasmid transfer frequency differed substantially between different donor and recipient pairs, and the frequency was influenced by plasmid content, temperature, and substrate, in addition to donor and recipient strain. pKPC-47e was attenuated in conjugation efficiency across all conditions tested. Despite its presence in multiple clinical species, pKPC_UVA01 had lower conjugation efficiencies than pKpQIL into recipient strains. The conjugation frequency of these plasmids into K. pneumoniae and E. coli patient isolates ranged widely without a clear correlation with clinical epidemiological data. Our results highlight the importance of each variable examined in these controlled experiments. The in vitro models did not reliably predict plasmid mobilization observed in a patient population, indicating that further studies are needed to understand the most important variables affecting horizontal transfer in vivo.
National Institutes of Health Clinical Center, Bethesda, Maryland, USA.
C A
CA
Hardiman
National Institutes of Health Clinical Center, Bethesda, Maryland, USA.
R A
RA
Weingarten
National Human Genome Research Institute, Bethesda, Maryland, USA.
S
0000-0001-6848-3465
S
Conlan
National Institutes of Health Clinical Center, Bethesda, Maryland, USA.
P
P
Khil
National Institutes of Health Clinical Center, Bethesda, Maryland, USA.
J P
JP
Dekker
University of Virginia Health System, Charlottesville, Virginia, USA.
A J
AJ
Mathers
Modernizing Medical Microbiology Consortium, Nuffield Department of Clinical Medicine, John Radcliffe Hospital, Oxford University, Oxford, United Kingdom.
A E
AE
Sheppard
National Human Genome Research Institute, Bethesda, Maryland, USA.
J A
JA
Segre
National Institutes of Health Clinical Center, Bethesda, Maryland, USA karen.frank@nih.gov.
K M
KM
Frank
D001426:Bacterial Proteins / Q000235:genetics*; D003428:Cross Infection / Q000235:genetics / Q000382:microbiology; D004926:Escherichia coli / Q000235:genetics; D004927:Escherichia coli Infections / Q000235:genetics; D022761:Gene Transfer, Horizontal / Q000235:genetics*; D006761:Hospitals; D006801:Humans; D007710:Klebsiella Infections / Q000235:genetics / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000235:genetics; D058885:Multilocus Sequence Typing / Q000379:methods; D010957:Plasmids / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics*
D001426:Bacterial Proteins; D001618:beta-Lactamases; C063912:carbapenemase