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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Produce Safety and Microbiology Research » Research » Publications at this Location » Publication #333438

Research Project: Molecular Identification and Characterization of Bacterial and Viral Pathogens Associated with Foods

Location: Produce Safety and Microbiology Research

Title: Isolation, genotyping, and antimicrobial resistance of zoonotic shiga toxin-producing escherichia coli

item AMÉZQUITA-LÓPEZ, BIANCA - Autonomous University Of Sinaloa
item SOTO-BELTRÁN, MARCELA - Autonomous University Of Sinaloa
item Lee, Bertram
item Yambao, Jaszemyn
item Quiñones, Beatriz

Submitted to: Journal of Microbiology, Immunology
Publication Type: Review Article
Publication Acceptance Date: 7/11/2017
Publication Date: 7/19/2017
Citation: Amézquita-López, B.A., Soto-Beltrán, M., Lee, B.G., Yambao, J.C., Quinones, B. 2017. Isolation, genotyping, and antimicrobial resistance of zoonotic shiga toxin-producing escherichia coli. Journal of Microbiology, Immunology. 51(4):425-434.

Interpretive Summary: Shiga toxin-producing Escherichia coli (STEC) is an enteric pathogen that has been linked to outbreaks from foodborne and waterborne sources. STECs are known to cause human gastrointestinal illnesses with diverse clinical spectra, ranging from watery and bloody diarrhea to hemorrhagic colitis. In some rare cases, disease symptoms can result in the life-threatening, hemolytic uremic syndrome, and it is thought that Shiga toxins (Stx1 and Stx2) are the key virulence factors contributing to the development of the hemolytic uremic syndrome. Although more than 200 different serotypes of STEC have been isolated, O157:H7 is the serotype that has been most studied since it has been commonly associated with the development of severe human illness. Recent epidemiological studies have revealed other STEC non-O157 serotypes, O26:H11, O45:H2, O103: H11, O111: H8, O121: H19, and O145:H28, to be highly associated with human disease. The objectives of this article are to systematically review the literature documenting methods employed for assessing the phenotypic, genotypic and functional characteristics of STEC O157 and non-O157. In particular, culture and isolation methods, animal reservoirs, routes of transmission, virulence factors, and pathogenicity will be discussed. Additional sections in this review article will also further discuss molecular methods as well as cytotoxicity and/or serological-based methods used to characterize virulence genes expressed by STEC strains. The final sections will examine recent reports, documenting an increase in antimicrobial resistance among STEC O157:H7 and non-O157 strains recovered from food, the environment and animal reservoirs

Technical Abstract: Shiga toxin-producing Escherichia coli (STEC) is an enteric pathogen linked to outbreaks of human gastroenteritis with diverse clinical spectra. Traditional culture and isolation methods, including selective enrichment and differential plating, have enabled the effective recovery of STEC. Ruminants are considered the main reservoir of zoonotic STEC. However, other small domestic ruminants have been implicated as carriers of STEC, and STEC can be also isolated from other mammals, birds, fish, amphibians, mollusks and insects. Following recovery, immunological serotyping of somatic surface antigens (O-antigens) and flagellum (H-antigens) are employed for the classification of the STEC isolates. Molecular genotyping methods, including multiple-locus variable-number tandem repeat analysis, arrays, and whole genome sequencing, can discriminate the isolate virulence profile beyond the serotype level. Virulence profiling is focused on the identification of chromosomal and plasmid genes coding for adhesins, cytotoxins, effectors, and hemolysins to better assess the pathogenic potential of the recovered STEC isolates. Finally, antimicrobial resistance in STEC is a matter of increasing concern. Inappropriate usage of antibiotics for treatment of bacterial infections in humans or for growth promotion in animals have contributed to the increase in antimicrobial resistance in STEC. In summary, this review is aimed at examining culturing and isolation methodologies as well as molecular characterization techniques. Together, this information will provide a better understanding of risks associated with zoonotic STEC and will aid in the development of efficient and targeted intervention strategies.