876. Molecular and Phenotypic Properties of Multi-Drug Resistant Extraintestinal Pathogenic Escherichia coli (ExPEC) from Clinical Samples 
Session: Poster Abstract Session: Bacterial Infections: Pathogenesis and Immunity
Friday, October 9, 2015
Room: Poster Hall

Escherichia coliis a leading cause of extraintestinal infections worldwide. In particular, strains belonging to multi-locus sequence type (MLST) 131 appear to be virulent, occur worldwide, and can harbor multiple antibiotic resistance genes. We sought to investigate the molecular and phenotypic properties of ST-131 clinical isolates from a major referral center in the United States (U.S.). 

Methods: 81 unique MDR E. coliisolates from 76 patients (median age 35: interquartile range, 8 months to 93 years; 74% male) were collected from blood (33%), sterile fluid (2.5%) and tissue (28.5%), respiratory (12%), and wound (24%) samples between July 2010 and August 2014. Isolates were tested for four common STs (131, 95, 73, and 69) by real-time PCR using a 5-plex assay. Whole genome sequencing (WGS) was performed on all isolates using an Illumina MiSeq sequencer. WGS-derived ST data were in agreement with real-time PCR for every isolate, except one ST-12 that was mis-identified as ST-95 by assay.

Results: WGS identified 27 different ST’s, with ST-131 accounting for 34.6%. Other common ST’s included ST-405 (8.6%), ST-648 (7.4%), and ST 1193 (6.2%). ESBL production was similar between ST-131 (53.6%, 95% CI = 35.6, 77.5) and non-ST-131 (62.3%, 95% CI = 42.8, 87.5), and 79.5% of ESBL isolates carried blaCTX-M-15. All isolates were sensitive to amikacin, though resistance to gentamicin and tobramycin ranged from 43.4% to 64.3%. The majority of isolates were resistant to the fluoroquinolones (71.1% and 85.7% ST-131 and non ST-131, respectively). Two isolates were carbapenem-resistant and carried blaOXA-181 with blaCTX-M-27, and blaKPC-2 with blaCTX-M-14, respectively. Phylogenetic analysis of the ST-131 core genomes indicated that strains differed by 7 to 13,977 single nucleotide polymorphisms (SNPs), including two isolates cultured 5 days apart from two patients that differed by just 9 SNPs.

Conclusion: E. coli ST-131 was the dominant lineage identified from invasive, non-urinary isolates in this setting. Resistance rates to common first-line antibiotics were very high. Unlike previous studies, E. coliSTs 95, 73, and 69 were not prevalent in our population, suggesting possible regional variation in ST distribution, and highlighting the importance of WGS for advanced surveillance.

Mackenzie Morgan, MD1, Emil Lesho, D.O., FIDSA2, Paige Waterman, M.D.3, Neil Woodford, PhD4, Michel Doumith, PhD4, Fatma Onmus-Leone, MS2, Ana Ong, BS2, Yoon Kwak, MS2, Rossalyn Maybank, BS2, Lakshmi Appalla, MS2, Erik Snesrud, BS2, Mary Hinkle, M.D.2 and Patrick Mcgann, PhD2, (1)Infectious Disease, Walter Reed National Military Medical Center, Bethesday, MD, (2)Walter Reed Army Institute of Research, Silver Spring, MD, (3)GEIS, Armed Forces Health Surveillance Center, Silver Spring, MD, (4)Public Health England, London, United Kingdom


M. Morgan, None

E. Lesho, None

P. Waterman, None

N. Woodford, None

M. Doumith, None

F. Onmus-Leone, None

A. Ong, None

Y. Kwak, None

R. Maybank, None

L. Appalla, None

E. Snesrud, None

M. Hinkle, None

P. Mcgann, None

Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 7th with the exception of research findings presented at the IDWeek press conferences.