Start | Browse by Day | Author Index | Personal Scheduler

P2-16 Genetic Characterization of Plasmids in O157:H7 and Non-O157:H7 Shiga Toxin-producing Escherichia coli Isolated from Humans and Foods

Tuesday, August 5, 2014
Exhibit Hall D (Indiana Convention Center)
Rajesh Nayak, U.S. Food and Drug Administration, Jefferson, AR
Joanna Deck, U.S. Food and Drug Administration, Jefferson, AR
Steven Foley, U.S. Food and Drug Administration, Jefferson, AR
Rossina Stefanova, Arkansas Public Health Laboratories, Little Rock, AR
Kimberly Musser, New York Public Health Laboratories, Albany, NY
Introduction: Shiga toxin-producing Escherichia coli (STEC) are responsible for several food and human borne outbreaks worldwide.  In the US, O157-STECs cause approximately 90% of hemolytic uremic syndrome (HUS) cases, while ~30% of humans infected with non-O157:H7 STEC develop HUS and hemorrhagic colitis.

Purpose: This study evaluated the Shiga toxins, plasmid profiles and incompatibility groups in STECs.

Methods: 72 STECs (13 O157:H7 and 59 non-O157:H7) from humans and foods were analyzed.  Non-O157:H7 STEC variants included O8:H8, O103, O121, O123, O174, O45, O69, O5, O8, O80, O165, O111 and O26.  A PCR-based replicon typing scheme was used to detect the presence of IncA/C, B/O, Frep, FIA, FIB, FIC, FIIA, HI1, HI2, I1, K/B, L/M, N, P, T, W, X, and Y. Additionally, Shiga toxin genes (stx1 and stx2) were detected in these isolates using PCR and ELISA.

Results: Data indicated that ~60% of the isolates harbored either the stx1 or stx2 gene and 40% harbored both genes. Both genes remained undetected in only one isolate (EC O26). Nearly 30% of O157:H7 isolates carried 1 to 3 plasmids (~0.2 to 100 kb), while 93% of the non-O157:H7 isolates carried 1 to 11 plasmids (~0.25 to 165 kb). Replicon typing data indicated that IncFIB plasmids were detected in 92% of O157:H7 and 76% of non-O157:H7 STEC isolates, while 40% of non-O157:H7 STEC isolates carried IncB/O plasmids.  Plasmids for IncB/O, IncFIC, IncP and IncFIA were detected in 8 to 16% of O157:H7 STEC isolates, while IncP, IncK/B, IncI1 and HI2 plasmids were identified in 3 to 7% in non-O157:H7 STEC isolates.  Interestingly, only one clinical isolate, EC O111, carried IncX, IncN and IncL/M plasmids. 

Significance: STECs harboring plasmids have a greater propensity to cause infections and spread diseases in humans because of the ability these plasmids to encode for multiple virulence, antimicrobial resistance and transfer-associated genes.

Back to: Poster Session - Pathogens, Epidemiology, Novel Laboratory Methods, Food Defense, Communication Outreach and Education, General Microbiology, Dairy and Other Food Commodities, Food Toxicology
<< Previous Abstract | Next Abstract >>