Multidrug resistant Escherichia coli from fresh produce sold by street vendors in South African informal settlements

ABSTRACT

The aim of this study was to assess the prevalence of commensal and pathogenic Escherichia coli on informally sold fresh produce in South Africa, who harbour and express antimicrobial resistance genes and therefore pose indirect risks to public health. The majority (85.71%) of E. coli isolates from spinach, apples, carrots, cabbage and tomatoes, were multidrug resistant (MDR). Resistance to Aminoglycoside (94.81%), Cephalosporin (93.51%), Penicillin (93.51%) and Chloramphenicol (87.01%) antibiotic classes were most prevalent. Antibiotic resistance genes detected included bla_TEM (89.29%), tetA (82.14%), tetB (53.57%), tetL (46.43%), sulI (41.07%), sulII (51.79%), aadA1a (58.93%) and strAB (51.79%). A single isolate was found to harbour eae virulence factor. Moreover, E. coli isolates were grouped into the intra-intestinal infectious phylogenetic group E (28.57%), the rare group C (26.79%), the generalist group B1 (21.43%) and the human commensal group A (16.07%). Presence of MDR E. coli represents a transmission route and significant human health risk.

KEYWORDS:

• Antimicrobial resistance
• antimicrobial resistance genes
• phylogenetic grouping
• diarrheagenic virulence genes

Acknowledgements

The financial assistance of the Department of Science and Innovation (DSI) – National Research Foundation (NRF) Centre of Excellence in Food Security who funded this research under the Food Safety Programme’s ‘Safe Food for the Food Insecure’ project (Project 160301 and 160302). This work is based on the research supported in part by the NRF of South Africa (Grant specific unique reference number (UID). 74426). Opinions expressed and conclusions arrived at, are those of the authors and are not necessarily to be attributed to the NRF. The Water Research Commission (WRC) funded project ‘Measurement of water pollution determining the sources and changes of microbial contamination and impact on food safety from farming to retail level for fresh vegetables’ (WRC Project No K5/2706/4, WRC Knowledge Review 2017/18) and the Partnerships for Enhanced Engagement in Research (PEER) a USAID/DSI funded project ‘Characterizing and tracking of antimicrobial resistance in the water-plant-food public health interface’ (Grant no. 48) are also acknowledged. Authors would like to acknowledge the DSI-NRF Centre of Excellence in Food Security and PEER for financial assistance. The authors would like to acknowledge Ms L. Richter and Ms Z. Zulu for laboratory assistance, Mr M. Jongman, Mrs A. Lombard and Mrs D. Muller for logistical support and Dr J. Gokul for editorial support. Additionally, the support of Ms Liesl Morey from the Agricultural Research Council of South Africa’s Biometry Unit is hereby acknowledged with sample design and statistical analysis.

Disclosure of interest

The authors declare no conflict of interest.

Data availability statement

The data that support the findings of this study are available from the corresponding author, S. Duvenage, upon reasonable request.

Additional information

Funding

This work was supported by the Department of Science and Innovation – National Research Foundation Centre of Excellence in Food Security [Project 160301 and 160302]; USAID Partnerships for Enhanced Engagement in Research (PEER) [Grant no. 48]; Water Research Commission [WRC Project No K5/2706/4]; National Research Foundation of South Africa [Grant specific unique reference number 74426].