Unraveling the Role of Vegetables in Spreading Antimicrobial-Resistant Bacteria: A Need for Quantitative Risk Assessment

Abstract

In recent years, vegetables gain consumer attraction due to their reputation of being healthy in combination with low energy density. However, since fresh produce is often eaten raw, it may also be a source for foodborne illness. The presence of antibiotic-resistant bacteria might pose a particular risk to the consumer. Therefore, this review aims to present the current state of knowledge concerning the exposure of humans to antibiotic-resistant bacteria via food of plant origin for quantitative risk assessment purposes. The review provides a critical overview of available information on hazard identification and characterization, exposure assessment, and risk prevention with special respect to potential sources of contamination and infection chains. Several comprehensive studies are accessible regarding major antimicrobial-resistant foodborne pathogens (e.g., Salmonella spp., Listeria spp., Bacillus cereus, Campylobacter spp., Escherichia coli) and other bacteria (e.g., further Enterobacteriaceae, Pseudomonas spp., Gram-positive cocci). These studies revealed vegetables to be a potential—although rare—vector for extended-spectrum beta-lactamase-producing Enterobacteriaceae, mcr1-positive E. coli, colistin- and carbapenem-resistant Pseudomonas aeruginosa, linezolid-resistant enterococci and staphylococci, and vancomycin-resistant enterococci. Even if this provides first clues for assessing the risk related to vegetable-borne antimicrobial-resistant bacteria, the literature research reveals important knowledge gaps affecting almost every part of risk assessment and management. Especially, the need for (comparable) quantitative data as well as data on possible contamination sources other than irrigation water, organic fertilizer, and soil becomes obvious. Most crucially, dose–response studies would be needed to convert a theoretical “risk” (e.g., related to antimicrobial-resistant commensals and opportunistic pathogens) into a quantitative risk estimate.

Occurrence, Phenotypic and Molecular Characterization of Extended-Spectrum- and AmpC- β-Lactamase Producing Enterobacteriaceae Isolated From Selected Commercial Spinach Supply Chains in South Africa

“…This highlights the potential role that the agricultural environment may have as a reservoir of MDR opportunistic pathogens in fresh produce production. However, the importance of not only assessing the agricultural environment as a possible source of antimicrobial contamination in fresh produce, but also the processing and distribution steps were discussed in a recent review (Hölzel et al, 2018). Accordingly, all ESBL-producing isolates from spinach (n = 18) in the second production scenario of this study were isolated from produce during processing and retail (distribution), of which 94.4% showed a MDR phenotype.…”

Prevalence of Antibiotic Resistome in Ready-to-Eat Salad

“…Multiple pathways of potential contamination between farm to fork exist for ready-to-eat salad products (6)(7)(8)(9). Consequently, the potential risk of ARGs transferring from raw vegetables to consumers is viable (10)(11)(12). The application of antibiotics in livestock production and subsequent use of livestock manure as an organic fertilizer in vegetable production is common practice to promote the health and growth of livestock and vegetable yields (13,14).…”

The Hydric Environment: A Hub for Clinically Relevant Carbapenemase Encoding Genes

“…While, urbanization of human habitats is on the rise, rural hydric environments are also impacted by animal husbandry and farming activities [ 19 ]. Then, humans could be exposed to Carbapenemase Producing Bacteria (CPB) including CPE, contained in aquatic environment, either directly during recreational activities, after flood episodes, or simply by drinking tap water [ 20 , 21 , 22 ], and either indirectly by foodborne transmission (re-use of treated wastewater for agricultural and livestock activities) [ 23 , 24 ]. Therefore, mixes between aquatic environmental communities and bacterial communities from human beings are consequently bidirectional and aquatic ecosystems constitute a hub for CPB.…”