P2-55 Isolation and Characterization of Shiga Toxin-producing Escherichia coli in Ground Beef from Santiago, Chile

Tuesday, July 11, 2017
Exhibit Hall (Tampa Convention Center)
Daniel Rivera , INTA, University of Chile , Santiago , Chile
Maria Fernanda Jimenez , INTA, University of Chile , Santiago , Chile
Leonela Diaz , INTA, University of Chile , Santiago , Chile
Paola Antivero , INTA, University of Chile , Santiago , Chile
Paola Navarrete , INTA, University of Chile , Santiago , Chile
Angelica Reyes-Jara , INTA, University of Chile , Santiago , Chile
Magaly Toro , INTA, University of Chile , Santiago , Chile
Introduction: Shiga toxin-producing Escherichia coli (STEC) is a pathogen causing sporadic diarrhea, foodborne outbreaks and complications such as hemorrhagic colitis and hemolytic uremic syndrome. The disease is associated with eating or manipulating raw or insufficiently cooked ground beef. In Chile, we lack information on isolation rates and characteristics of STEC present in ground beef.

Purpose: To isolate and characterize STEC from ground beef obtained in Santiago, Chile.

Methods: We collected 430 ground beef samples from retail butcher shops and grocery stores in Santiago, Chile in 2016. After enrichment, samples were screened for Shigatoxin genes (stx1 and stx2). Isolated colonies were confirmed as STEC through PCR (E. coli, stx1, stx2.), and biochemical characteristics (hemolysin and β-glucoronidase production, tellurite resistance, sorbitol fermentation) were investigated. Also, virulence genes for intimin (eae) and hemolysin (hlyA) were detected through PCR, besides serogroup identification for O26, O45, O103, O111, O121, O145 (big six) and O157.

Results: STEC was detected in 9.3% (40 of 430) of samples, and 65 STEC isolates were obtained. Most of the positive samples (55%; 18 of 40) were obtained from butcher shops. Isolates carried only stx1 (22%), only stx2, (56%) or both Shigatoxin genes (22%). The hlyA gene was detected in 29% of isolates, while eae was not detected. None of the isolates was identified as serogroup O157 or big six. Almost all isolates (98%) fermented sorbitol and produced β-glucoronidase, and 70% produced α-hemolisyn. Conversely, only 4% were resistant to tellurite.

Significance: Ground beef being sold in Santiago, Chile carries STEC and may represent a risk for consumers. More studies are required to investigate the battery of virulence determinants that may be present in these bacterial population and to assess pathogenic potential. Isolation medium containing potassium tellurite may not be suitable to recover all STEC from food samples since only a few isolates were resistant to the agent.