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. 2020 Mar 25:8:92.
doi: 10.3389/fpubh.2020.00092. eCollection 2020.

Prevalence of Antibiotic Resistome in Ready-to-Eat Salad

Shu-Yi-Dan Zhou  1   2 , Meng-Yun Wei  1   2 , Madeline Giles  3 , Roy Neilson  3 , Fei Zheng  1   2 , Qi Zhang  4 , Yong-Guan Zhu  1   2   5 , Xiao-Ru Yang  1   5
Affiliations

Prevalence of Antibiotic Resistome in Ready-to-Eat Salad

Shu-Yi-Dan Zhou et al. Front Public Health. .

Abstract

Ready-to-eat salad harbors microorganisms that may carry various antibiotic resistance genes (ARGs). However, few studies have focused on the prevalence of ARGs on salad, thus underestimating the risk of ARGs transferring from salad to consumers. In this small-scale study, high-throughput quantitative PCR was used to explore the presence, prevalence and abundance of ARGs associated with serving salad sourced from two restaurant types, fast-food chain and independent casual dining. A total of 156 unique ARGs and nine mobile genetic elements (MGEs) were detected on the salad items assessed. The abundance of ARGs and MGEs were significantly higher in independent casual dining than fast-food chain restaurants. Absolute copies of ARGs in salad were 1.34 × 107 to 2.71 × 108 and 1.90 × 108 to 4.87 × 108 copies per g salad in fast-food and casual dining restaurants, respectively. Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes were the dominant bacterial phyla detected from salad samples. Pseudomonas, Acinetobacter, Exiguobacterium, Weissella, Enterobacter, Leuconostoc, Pantoea, Serratia, Erwinia, and Ewingella were the 10 most dominant bacterial genera found in salad samples. A significant positive correlation between ARGs and MGEs was detected. These results integrate knowledge about the ARGs in ready-to-eat salad and highlight the potential impact of ARGs transfer to consumers.

Keywords: antibiotic resistance genes (ARGs); high-throughput quantitative PCR; human health; ready-to-eat food; salad.

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Figures

Figure 1
Figure 1
Number of ARGs and MGEs detected in fast-food chain (CR) and casual dining restaurants (SR) (A). Percentage of antibiotic resistance mechanisms detected in ARGs and MGEs from fast-food chain (CR) and casual dining (SR) restaurants (B). Normalized abundance of ARGs in fast-food chain (CR) and casual dining (SR) restaurants (C). CR1-CR5 and SR1-SR5 are sample codes pertaining to the samples of salad collected from each restaurant type.
Figure 2
Figure 2
Percentage of ARGs and MGEs based on the overall abundance of ARGs and MGEs in each sample (A). Non-metric Multidimensional scaling (NMDS) analysis of ARGs from all samples (B). The two-dimensional stress was 0.083. Different colors and shapes represent the different samples.
Figure 3
Figure 3
Normalized abundance of transposase and integron from sampled fast-food chain (CR) and casual dining (SR) restaurants.
Figure 4
Figure 4
Ordinary least-squares (OLS) analysis between ARGs and MGEs among the samples from fast-food chain and casual dining restaurants.
Figure 5
Figure 5
Composition of the 10 most prevalent bacterial genera detected from all samples. Data were depicted by Circos software. Length of the bars (sites) represent the percentage of the respective genus from each sample. Length of the bars (genus) represents the percentage the sample contributes to the proportion of each bacterial genus.
See this image and copyright information in PMC

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