Comparison of Three Molecular Subtyping Methods among O157 and Non-O157 Shiga Toxin-Producing Escherichia coli Isolates from Japanese Cattle

Study of the transfer of Shiga toxin-producing Escherichia coli during the slaughter of cattle using molecular typing combined with epidemiologic data

Investigation on the distribution and biological characteristics of Shiga-toxin producing Escherichia coli (STEC) during beef processing is essential for in-plant critical control points and food safety risk assessment. Serogroups and subtypes of stx genes of STEC strains isolated from beef processing lines were first investigated. Identification to cross-contamination among different sampling sites was further conducted by combining multilocus sequence typing (MLST) with the previous distribution and characterization data. The PCR-positive rate for STEC in 435 samples from two slaughter plants in China was 14.3% and the isolation rate for the 62 PCR positive and the entire set of 435 samples were 26% and 3.68% respectively. The existence of serotype O157:H7 (33%) and serogroups O121 (42%) and O26 (21%) as well as the high detection rate of high pathogenic gene stx2a (68%) in these serogroups indicated potential risk to the safety of beef. Traceability analysis showed that hide plays a critical role in cross-contamination between feces, lairage pens and post-washing carcasses from a molecular perspective. Intervening measures revolves around de-hiding should be involved in the in-plant safety control policy according to the tracing analysis.

Subtyping β-lactamase-producing Escherichia coli strains isolated from patients with UTI by MLVA and PFGE methods

OBJECTIVES

Strain subtyping is an important epidemiological tool to trace contamination, determine clonal relationships between different strains, and the cause of outbreaks. Current subtyping methods, however, yield less than optimal subtype discrimination. Pulsed-field gel electrophoresis is the gold standard method for Escherichia coli and Multiple-Locus Variable-number tandem repeat Analysis is a rapid PCR-based method. The purpose of this study was to evaluate MLVA and PFGE methods for subtyping β -lactamase-producing E. coli strains isolated from urinary tract infections.

MATERIALS AND METHODS

Overall, 230 E. coli isolates from patients with urinary tract infections were examined for antimicrobial susceptibility testing. 10-loci and 7-loci MLVA and PFGE methods were used for molecular typing of β -lactamase-producing E. coli isolates.

RESULTS

Out of 230 isolates, 130 (56.5%) β -lactamase-producing E. coli isolates were found in this study. The diversity indices of the VNTR loci showed an average diversity of 0.48 and 0.54 for 7-loci and 10-loci MLVA, respectively. The discriminatory power of PFGE showed a value of 0.87. The discordance between the methods was high.

CONCLUSION

Our study showed that PFGE is more discriminatory than MVLA. MLVA is a PCR- based method and can generate unmistakable data, in contrast to PFGE. Optimization of polymorphic VNTR is essential to improve the discriminatory power of MLVA based on geographical region.

Whole-Genome Phylogenetic Analysis Reveals a Wide Diversity of Non-O157 STEC Isolated From Ground Beef and Cattle Feces

Shiga toxin-producing Escherichia coli (STEC) causes foodborne outbreaks that can lead to complications such as hemolytic uremic syndrome. Their main reservoir is cattle, and ground beef has been frequently associated with disease and outbreaks. In this study, we attempted to understand the genetic relationship among STEC isolated in Chile from different sources, their relationship to STEC from the rest of the world, and to identify molecular markers of Chilean STEC. We sequenced 62 STEC isolated in Chile using MiSeq Illumina. In silico typing was determined using tools of the Center Genomic Epidemiology, Denmark University (CGE/DTU). Genomes of our local STEC collection were compared with 113 STEC isolated worldwide through a core genome MLST (cgMLST) approach, and we also searched for distinct genes to be used as molecular markers of Chilean isolates. Genomes in our local collection were grouped based on serogroup and sequence type, and clusters were formed within local STEC. In the worldwide STEC analysis, Chilean STEC did not cluster with genomes of the rest of the world suggesting that they are not phylogenetically related to previously described STEC. The pangenome of our STEC collection was 11,650 genes, but we did not identify distinct molecular markers of local STEC. Our results showed that there may be local emerging STEC with unique features, nevertheless, no molecular markers were detected. Therefore, there might be elements such as a syntenic organization that might explain differential clustering detected between local and worldwide STEC.

Characterization and molecular subtyping of Shiga toxin-producing Escherichia coli strains in provincial abattoirs from the Province of Buenos Aires, Argentina, during 2016-2018

We characterized Shiga toxin-producing Escherichia coli (STEC) O157 (n = 20) and non-O157 (n = 68) isolated from carcasses (n = 54), the environment (n = 20), head meat (n = 3) and viscera washing and chilling water (n = 11) in provincial abattoirs before and after implementing improvement actions. The strains were tested for eae, saa, ehxA and fliC_H7 genes. Variants stx₁ and stx₂ were also determined. Pulsed-field gel electrophoresis (PFGE) was carried out with restriction enzymes XbaI and BlnI. All twenty O157 STEC strains [H7; H21; HNM] carried genes rfb_O157 and ehxA; 90.0 % were positive for eae and 15.0 % were negative for fliC_H7 and positive for saa. Results of PFGE showed 17 XbaI patterns, of which 14 were unique and three formed clusters. From the 68 non-O157 STEC strains, 66.2 %, 55.9 % and 2.9 % were positive for ehxA, saa and eae genes, respectively. Fifty-three XbaI patterns were obtained (49 unique and four forming clusters). Cross-contamination between products and between the environment and products was confirmed in all abattoirs. While the proposed improvements reduced the risk of contamination, Good Hygiene Practices and Good Manufacturing Practices should be implemented in provincial abattoirs, stressing the importance of having a uniform national food safety standard.