Isolation, genotyping and antimicrobial resistance of Shiga toxin-producing Escherichia coli

Abstract

Shiga toxin-producing Escherichia coli (STEC) is an enteric pathogen linked to outbreaks of human gastroenteritis with diverse clinical spectra. In this review, we have examined the currently methodologies and molecular characterization techniques for assessing the phenotypic, genotypic and functional characteristics of STEC O157 and non-O157. In particular, traditional culture and isolation methods, including selective enrichment and differential plating, have enabled the effective recovery of STEC. 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. Important animal reservoirs are cattle and other small domestic ruminants. STEC can also be recovered from other carriers, such as mammals, birds, fish, amphibians, shellfish and insects. Finally, antimicrobial resistance in STEC is a matter of growing concern, supporting the need to monitor the use of these agents by private, public and agricultural sectors. Certain antimicrobials can induce Shiga toxin production and thus promote the onset of severe disease symptoms in humans. Together, this information will provide a better understanding of risks associated with STEC and will aid in the development of efficient and targeted intervention strategies.

Dextran Sulfate Sodium Colitis Facilitates Colonization with Shiga Toxin-Producing Escherichia coli: a Novel Murine Model for the Study of Shiga Toxicosis

“…Oral gavage time points and the dose and duration of DSS treatment used in the DSSϩSTEC model were determined via dose-response pilot experiments exploring DSS concentrations (1.0 to 3.5% [wt/vol]) and duration (DSS for 4 to 5 days with or without low-dose DSS maintenance dosing) to identify conditions that induced mild or moderate, but not severe, colitis. Gram-negative STEC can grow on MacConkey's medium under aerobic conditions, and MacConkey's medium with sorbitol has been used for partial selection of STEC from clinical samples (34). Prior to DSS exposure, bacteria capable of growing on MacConkey's medium were isolated at low abundance from C57BL/6 mouse feces, with 1.8 ϫ 10 5 Ϯ 0.7 ϫ 10 5 CFU/g recovered after overnight aerobic incubation at 37°C.…”

Virulence Characteristics and Antibiotic Resistance Profiles of Shiga Toxin-Producing Escherichia coli Isolates from Diverse Sources

“…The following 17 antibiotics were tested: ampicillin, methicillin, penicillin, vancomycin, erythromycin, clindamycin, ciprofloxacin, chloramphenicol, gentamicin, imipenem, meropenem, streptomycin, tetracycline, kanamycin, nalidixic acid, novobiocin, and tigecycline. E. coli ATCC 25922, which is sensitive to all the drugs, was used as the control strain [6,[36][37][38][39]. The results were used to classify the strains as resistant or susceptible to a specific antibiotic using standard reference values recommended by the CLSI National Committee [35].…”

Occurrence of Escherichia coli carrying Shiga toxin-producing genes in buffaloes on smallholdings in Bangladesh

“…Buffaloes, as a reservoir of STEC, have been reported in many countries in Asia, Europe, and South America [ 8 - 10 ]. In Bangladesh, the occurrence of antimicrobial-resistant STEC in healthy cattle, sheep, and goat on smallholdings has been described previously [ 11 - 13 ]; despite 38% buffalo sampled after the slaughter in an urban area of Bangladesh found STEC positive [ 14 ], buffaloes on smallholdings in rural Bangladesh remain unscreened for the presence of STEC.…”