183. Molecular analysis of colistin resistance among Klebsiella pneumoniae producing KPC (Kp-KPC): heterogeneity of genetic mechanisms
Session: Poster Abstract Session: Diagnostics: Bacteriology, Sequencing, and Resistance
Thursday, October 27, 2016
Room: Poster Hall
Background: Carbapenem-resistant Kp-KPC mainly belonging to clonal complex 258 (CC258) are challenging pathogens due to the limited treatment options and high mortality rates. Colistin is among the few agents that retain activity against Kp-KPC. Studies examining the mechanism of colistin resistance among Kp-KPC are infrequent in the US. We evaluated the molecular basis of colistin resistance in strains collected as part of CRaCKle, the Consortium on Resistance against Carbapenems in Klebsiella pneumoniae. We hypothesized that alterations in the mgrBlocus would be the primary mechanism for resistance.

Methods: Isolates included were collected from December 2011 to October / 2014 in CRaCKle, a prospective, multi-center, observational study in the Great Lakes Region of the US. Hospitalized patients were included only once at the time of their first culture positive for a Kp-KPC isolate. Isolates found to be colistin resistant by broth macrodilution (BMD) were studied. To determine the genetic basis of the colR phenotype among these Kp-KPCs, the mgrB locus and the plasmid-mediated mcr-1gene were queried in a subgroup using PCR amplification. Products were sequenced using a commercial facility.

Results: We tested 264 isolates in our lab using BMD. BMD demonstrated MICs of >2 mg/L in 41 non replicated isolates. None of the queried isolates with MICs > 2 mg/L to colistin carried mcr-1. The genetic changes found in the mgrBlocus included deletion of the gene, point mutations leading to truncated products, and insertional inactivation by ISKpn26 (10 of 21 colR Kp-KPC isolates) (Figure 1).

Conclusion:

We show that US isolates collected as part of CRaCKLE possess heterogeneity of resistance mechanism leading to the colR phenotype. In this collection of isolates we found insertional inactivation of mgrB, which seems to be a frequent feature in ST258 strains. Surprisingly, we found several isolates possessing WT mgrB, suggesting that other mechanism may be present.

Laura J Rojas, MSc1, Steven Marshall, MS2, Eric Cober, MD3, Sandra S. Richter, MD4, Federico Perez, MD5, Robert Salata, MD6, Robert Kalayjian, MD7, Richard R. Watkins, MD, MS, FACP8, Yohei Doi, MD, PhD9, Keith S. Kaye, MD, MPH10, Scott Evans, PhD, MS11, Vance Fowler, MD12, David Van Duin, MD, PhD13 and Robert A. Bonomo, MD1, (1)Pharmacology, Molecular Biology, and Microbiology, Case Western Reserve University, Cleveland, OH, (2)Research Service, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH, (3)Department of Infectious Diseases, Cleveland Clinic, Cleveland, OH, (4)Department of Laboratory Medicine, Cleveland Clinic, Cleveland, OH, (5)Louis Stokes Cleveland VA M, Cleveland, OH, (6)University Hospitals Case Medical Center, Cleveland, OH, (7)Department of Medicine, MetroHealth Medical Center, Cleveland, OH, (8)Infectious Diseases, Akron General Medical Center, Akron, OH, (9)Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA, (10)Detroit Medical Center, Detroit, MI, (11)Department of Biostatistics and the Center for Biostatistics in AIDS Research, Harvard School of Public Health, Boston, MA, (12)Duke University, Durham, NC, (13)Division of Infectious Diseases, University of North Carolina, Chapel Hill, NC

Disclosures:

L. J. Rojas, None

S. Marshall, None

E. Cober, None

S. S. Richter, bioMerieux: Research funding , Research support
Nanosphere: Research funding , Research support
BD Diagnostics: Research Funding , Research support
Roche: Research funding , Research support
Biofire: Research funding , Research support
OpGen: Research funding , Research support

F. Perez, Pfizer: Grant Investigator , Grant recipient
Actavis: Consultant , Consulting fee

R. Salata, None

R. Kalayjian, None

R. R. Watkins, None

Y. Doi, None

K. S. Kaye, None

S. Evans, None

V. Fowler, Pfizer: Consultant and Grant Investigator , Consulting fee and Research grant
Novartis: Consultant , Consulting fee
Galderma: Consultant , Consulting fee
Novadigm: Consultant , Consulting fee
Durata: Consultant , Consulting fee
Debiopharm: Consultant , Consulting fee
Genentech: Consultant , Consulting fee
Achaogen: Consultant , Consulting fee
Affinium: Consultant , Consulting fee
Medicines Co: Consultant , Consulting fee
Cerexa: Consultant and Grant Investigator , Consulting fee and Grant recipient
Tetraphase: Consultant , Consulting fee
Trius: Consultant , Consulting fee
MedImmune: Consultant and Grant Investigator , Consulting fee and Grant recipient
Bayer: Consultant , Consulting fee
Theravance: Grant Investigator and Scientific Advisor , Research grant
Cubist/Merck: Consultant and Grant Investigator , Consulting fee and Research grant
Basilea: Consultant , Consulting fee
Affinergy: Consultant and Grant Investigator , Consulting fee and Research support
Janssen: Consultant , Consulting fee
Actavis/Forest/Cerexa: Grant Investigator , Grant recipient
Advanced Liquid Logics: Grant Investigator , Research support
Novartis: Consultant , Consulting fee
Medical Biosurfaces: Grant Investigator , Research support
Locus: Grant Investigator , Research support
Contrafect: Grant Investigator , Grant recipient
Karius: Grant Investigator , Grant recipient
Green Cross: Consultant , Speaker honorarium

D. Van Duin, None

R. A. Bonomo, Merck: Grant Investigator and Scientific Advisor , Consulting fee and Research grant
Actavis: Invited Speaker , Speaker honorarium
Allergan: Grant Investigator , Research grant
Wockhardt: Grant Investigator , Research grant
GlaxoSmithKline: Grant Investigator , Research grant
AstraZeneca: Grant Investigator , Research grant

Findings in the abstracts are embargoed until 12:01 a.m. CDT, Wednesday Oct. 26th with the exception of research findings presented at the IDWeek press conferences.