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Microbiological safety of spinach throughout commercial supply chains in Gauteng Province, South Africa and characterisation of isolated multidrug resistant Escherichia coli

Microbiological safety of spinach throughout commercial supply chains in Gauteng Province, South Africa and characterisation of isolated multidrug resistant Escherichia coli

Richter, Loandi, Du Plessis, Erika. M., Duvenage, Stacey ORCID: 0000-0002-5984-1491 and Korsten, Lise (2021) Microbiological safety of spinach throughout commercial supply chains in Gauteng Province, South Africa and characterisation of isolated multidrug resistant Escherichia coli. Journal of Applied Microbiology. ISSN 1364-5072 (Print), 1365-2672 (Online) (In Press)

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Abstract

Aim:
To investigate the microbiological quality, potential human foodborne pathogen presence, and to phenotypically (antimicrobial resistance profiles) and genotypically (DNA fingerprinting and diarrheagenic gene presence) characterise Escherichia coli isolated throughout commercial spinach production systems from farm-to-sale.

Methods and Results:
Samples (n=288) were collected from two commercial supply chains using either river or borehole water for irrigation. Escherichia coli was enumerated throughout the chain where river water was directly used for overhead irrigation at levels between 0.00-3.22 log CFU.g-1. Mean Enterobacteriaceae and coliform counts of spinach ranged between 3.33-6.57 log CFU.g-1 and 3.33-6.64 log CFU.g-1, respectively. Following enrichment, isolation and MALDI-TOF identification, E. coli was isolated from 22.57% (n=65/288) of all samples, Salmonella spp. from 3% (n=9/288) of all samples, specifically river and irrigation water samples on one farm, and no Listeria monocytogenes was detected throughout the study. Of the 80 characterised E. coli isolates, one harboured the stx2 virulence gene, while 43.75% (n=35) were multidrug resistant. This included 26.30% multidrug resistant E. coli isolates from production scenario one, where river water was used for irrigation, and 17.50% from the second production scenario that used borehole water for irrigation. Overall, a greater percentage of resistance phenotypes were from water E. coli isolates (52.50%), than isolates from spinach (37.50%). Escherichia coli isolates from spinach and irrigation water clustered together at high similarity values (>90%) using ERIC-PCR analysis.

Conclusions:
The results from this study provide valuable background information regarding the presence of multidrug resistant environmental E. coli throughout spinach production from farm, during processing and up to retail. Furthermore, the similarity of MDR E. coli isolates demonstrated transfer from irrigation water to spinach in both scenarios, reiterating that irrigation water for vegetables consumed raw, should comply with standardised microbiological safety guidelines.

Significance and Impact of Study:
Multidrug resistant E. coli presence throughout spinach production emphasises the necessity of increased surveillance of antimicrobial resistance in fresh produce and the production environment within a One Health paradigm to develop antimicrobial resistance mitigation strategies.

Item Type: Article
Uncontrolled Keywords: antimicrobial resistance, fresh produce, irrigation water, food safety
Subjects: Q Science > QR Microbiology
R Medicine > RV Botanic, Thomsonian, and eclectic medicine
Faculty / Department / Research Group: Faculty of Engineering & Science
Faculty of Engineering & Science > Natural Resources Institute
Faculty of Engineering & Science > Natural Resources Institute > Food & Markets Department
Last Modified: 27 Aug 2021 15:28
Selected for GREAT 2016: None
Selected for GREAT 2017: None
Selected for GREAT 2018: None
Selected for GREAT 2019: None
Selected for REF2021: None
URI: http://gala.gre.ac.uk/id/eprint/33605

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