Genetic Diversity and Antibiotic Resistance Patterns of Staphylococcus Aureus Isolated from Leaf Vegetables in Korea

Antibiotic Resistance Genes and Microbiota in Brassica oleracea var. acephala Cultivated in South Korea: Potential for Resistance Transmission

Antimicrobial resistance (AMR) poses a critical global public health challenge. This study investigates the microbiome of Brassica oleracea var. acephala (kale) to evaluate the role of food production systems, particularly plant-derived foods, in AMR dissemination. Using 16S rRNA gene sequencing and metagenomic shotgun sequencing, we analyzed microbial diversity and antimicrobial resistance genes (ARGs) in kale samples. Results showed significant regional differences in microbiota composition and ARG distribution, with traditional fertilizer use linked to higher ARG prevalence in coliform bacteria compared to farms using other fertilization methods. Additionally, we confirmed ARG transfer potential by Klebsiella pneumoniae within coliform populations. Storage conditions notably affected microbial dynamics, with higher temperatures promoting K. pneumoniae growth in washed samples. These findings revealed the importance of AMR research in plant-derived foods and highlight the need for improved agricultural practices to mitigate the risks associated with high ARG abundance in coliform bacteria.

Methicillin-Resistant Staphylococcus aureus (MRSA) in Different Food Groups and Drinking Water

Methicillin-resistant Staphylococcus aureus (MRSA) has been included by the World Health Organization in its list of "priority pathogens" because of its widespread prevalence and the severity of the infections it causes. The role of food in infections caused by MRSA is unknown, although strains of this microorganism have been detected in various items for human consumption. In order to gain an overview of any possible role of food in MRSA infections, a review was undertaken of studies published between January 2001 and February 2024 relating to MRSA. These comprised research that focused on fish and shellfish, eggs and egg products, foods of vegetable origin, other foodstuffs (e.g., honey or edible insects), and drinking water. In most of these investigations, no prior enrichment was carried out when isolating strains. Three principal methods were used to confirm the presence of MRSA, namely amplification of the mecA gene by PCR, amplification of the mecA and the mecC genes by PCR, and disc diffusion techniques testing susceptibility to cefoxitin (30 μg) and oxacillin (1 μg). The great diversity of methods used for the determination of MRSA in foods and water makes comparison between these research works difficult. The prevalence of MRSA varied according to the food type considered, ranging between 0.0% and 100% (average 11.7 ± 20.3%) for fish and shellfish samples, between 0.0% and 11.0% (average 1.2 ± 3.5%) for egg and egg products, between 0.0% and 20.8% (average 2.5 ± 6.8%) for foods of vegetable origin, between 0.6% and 29.5% (average 28.2 ± 30.3%) for other foodstuffs, and between 0.0% and 36.7% (average 17.0 ± 14.0%) for drinking water.

Prevalence, antibiotic resistance and molecular characterization of Staphylococcus aureus in ready-to-eat fruits and vegetables in Shanghai, China

Staphylococcus aureus (S. aureus) is one of the foodborne pathogens. This study aimed to investigate the prevalence of S. aureus in ready-to-eat (RTE) fruits and vegetables in Shanghai, China. We evaluated antibiotic resistance patterns and genetic diversity of isolates through whole genome sequencing. Our findings demonstrated that out of 143 market samples, 47 (32.87%) tested positive for S. aureus, with the prevalence rates ranging from 10% to 57.14% among 12 types of RTE fruits and vegetables. Most isolates were resistant to trimethoprim-sulphamethoxazole, oxacillin, and ampicillin. We identified a total of 15 antibiotic resistance genes associated with resistance to 6 antibiotics, such as fosfomycin, fluoroquinolone, and β-lactam. Adhesion genes and enterotoxin genes, including icaA, icaB, icaC, set, seg, and sec, were also identified. Seven multi-locus sequence types (MLST) were detected, two of which were novel (ST7208 and ST7986). Notably, ST705-t529 (34.04%) and ST6-t701 (27.79%) represented the predominant types of S. aureus. Furthermore, three of the isolates were confirmed to be methicillin-resistant S. aureus by mecA genes. Taken together, our results highlight the high prevalence of S. aureus in RTE fruits and vegetables, posing a potential threat to food safety, particularly due to its high level of antibiotic resistance.

Commonly Consumed Vegetables as a Potential Source of Multidrug-Resistant and β-Lactamase-Producing Bacteria in Debre Berhan Town, Ethiopia

Background

Recently, antibiotic resistance of bacteria contained in foods such as vegetables has become a public health problem. In Ethiopia, the diversity of bacterial contamination and level of antibiotic resistance in vegetables are poorly understood. Local analysis of vegetable contamination and its contribution to the spread of antibiotic resistance are therefore essential for One Health interventions. Therefore, the aim of this study was to investigate the level of bacterial contamination of commonly consumed vegetables and their antimicrobial resistance patterns.

Methods

A cross-sectional research was conducted in Debre Berhan town from February to August 2022. Questionnaires were used to collect data on sociodemographic variables, hygiene practices, and market hygiene. Six carefully selected vegetables (30 each, 180 in total) were purchased at a local market. Bacterial isolation and identification, multidrug-resistant (MDR) screening and confirmation, extended-spectrum β-lactamase (ESBL) screening and confirmation, and antibiotic susceptibility tests were performed using standard operating procedure. The data were analysed statistically using SPSS software version 25.

Results

The contamination rate of vegetables was 119 (66.1%). Of the 176 bacteria isolates, E. coli (26.1%; 46/176), S. aureus (18.8%; 176), S. epidermidis (10.8%; 19/176), Klebsiella spp. (9.1%; 16/179) and Acinetobacter spp. (6.8%; 12/176) were the most frequently detected isolates. Of the 180 samples tested, (66.1%; 119/180) were contaminated with at least one type of bacteria. Lettuce (22.7%; 40/176), spinach (18.6%; 33/176), and cabbage (19.2%; 32/176) were the most contaminated vegetables. Of the 176 bacteria isolates, (64.8%; 114/176) were MDR, and (18.5%; 23/124) isolates were ESBL producers. The kind of vegetables, vendor/seller finger-nail status, medium of display, market type, and not cleaned before to display were all significantly associated with bacterial contamination.

Conclusion

This study found that commonly consumed vegetables are contaminated with antibiotic-resistant bacteria. Vegetables were also notable for the incidence of multidrug-resistant, extended β-lactamase-resistant, and methicillin-resistant bacterial isolates. Therefore, we urge local health authorities to develop and implement effective control strategies to reduce vegetable contamination.

An overview on endophytic bacterial diversity habitat in vegetables and fruits

Nowadays, scientific research revolution is going on in many areas, and the human health is one of them. However, in the earlier studies, it was observed that most of the people health in the world affects by consumptions of contaminated food which is dangerous for human health and country economy. Recent studies showed that the fresh vegetables and fruits are the major habitat for endophytic bacterial communities. Salmonella and Escherichia coli both are the very common bacteria founds in fresh vegetables and fruits. Generally, many people eat vegetables and fruits without cooking (in the form of salad). The continued assumption of such food increases the health risk factor for foodborne diseases. So, from the last decades, many researchers working to understand about the relationship of endophytic microbes with plants either isolated bacteria are pathogenic or nonpathogenic. Moreover, most of the endophytes were identified by using 16S rRNA sequencing method. Hence, this review elaborates on the differences and similarities between nonpathogenic and pathogenic endophytes in terms of host plant response, colonization strategy, and genome content. Furthermore, it is emphasized on the environmental effects and biotic interactions within plant microbiota that influence pathogenesis and the pathogenesis.

Modelling the growth of Staphylococcus aureus on cooked broccoli under isothermal conditions

In this study, we developed predictive models describing the growth of Staphylococcus aureus on cooked broccoli florets. A pool of 3.5 log CFU/g of five S. aureus strains were inoculated on 10 g broccoli portions. The samples were then stored at 10, 20, 30 and 37 °C, and colonies were enumerated at different time intervals. Baranyi and Roberts model was fitted to the data using a Bayesian Adaptive Markov Chain Monte Carlo for estimation of the growth parameters. S. aureus showed low growth at 10 °C on broccoli samples and at 20-37 °C interval, Baranyi and Roberts model fitted well to the experimental data (R²>0.97). Estimated growth parameters were correlated with the possibility of toxin production and indicate the potential presence of these biological hazards on contaminated broccoli after heat treatment. Additionally, linear regression was performed for growth rate as storage temperature function. This secondary model followed a linear tendency with R²=0.997 and was compared with two tertiary models (ComBase Predictor and Pathogen Modeling Program) and literature data, demonstrating similar growth rate values of both. These results can be helpful for food services and managers to establish food safety standards for S. aureus growth on cooked broccoli.

Myzus persicae (Hemiptera: Aphididae) infestation increases the risk of bacterial contamination and alters nutritional content in storage Chinese cabbage

BACKGROUND

Aphids are common insect pests that feed on and excrete feces/honeydew on storage vegetables, especially in the temperate region of the northern hemisphere. The honeydew of aphids is an excellent growth medium for microorganisms. To explore the effects of aphid infestation on the risk of microbial contamination and food safety: (i) the bacterial diversity and community in aphid honeydew were investigated; (ii) the nutritional components of the cabbage were analyzed; and (iii) safety was evaluated.

RESULTS

The results showed that the dominant bacteria in storage Chinese cabbage under different exposure times belonged to the phylum Proteobacteria, family Enterobacteriaceae. The richness of Enterobacteriaceae increased from 36.35% (1 day) to 39.70% (5 days) and to 50.74% (10 days) as the exposure time increased. Serratia was the genus with the highest abundance (23.38% for 1 day, 30.56% for 5 days and 37.85% for 10 days). The abundance of pathways associated with Staphylococcus aureus infection and Shigellosis increased significantly after prolonged storage. In addition, when the aphid density increased from 0 to 100 per 250 g of Chinese cabbage leaves, the protein content in Chinese cabbage decreased significantly, whereas the reducing sugar content increased significantly.

CONCLUSION

These results demonstrate that the honeydew excreted by the green peach aphid Myzus persicae (Sulzer) on storage Chinese cabbage can serve as a medium for some foodborne disease pathogens. The present study may provide both a theoretical and practical basis for vegetable storage to reduce the risk of foodborne pathogen infection and to maintain the balance of nutrients. © 2020 Society of Chemical Industry.

Identification of antimicrobial resistant bacteria from plant-based food products imported into Canada

The role of plant-based foods in the epidemiology of antimicrobial resistance has been inadequately studied. In this investigation, resistant organisms from vegetables, fruits and spices imported into Canada were identified and characterized. A total of 143 products imported from primarily Asian and African countries were purchased from international markets in Saskatoon, Saskatchewan. Samples were selectively cultured for bacterial species where resistance is known to be emerging. The proportions of samples positive for each organism were as follows: E. coli (n = 13, 9.1%), Salmonella spp. (n = 2, 1.4%), ESBL producing Enterobacter spp. (n = 2, 1.4%) and K. pneumoniae (n = 2, 1.4%), S. aureus (n = 7, 4.9%) and Enterococcus spp. (n = 66, 46.2%). Antimicrobial minimum inhibitory concentrations were determined by broth micro-dilution and agar-dilution. Based on the susceptibility of each organism, isolates were screened for resistance genes (β-lactamases and plasmid mediated quinolones resistance determinants) by PCR. Extended-spectrum β-lactamase producing Enterobacteriaceae and methicillin resistant S. aureus (MRSA) were identified from 6/143 (4.2%) and 2/143 (1.4%) of samples respectively. The qnrB, qnrS and aac(6')-Ib-cr plasmid mediated quinolone resistance determinants were identified in 2/143 (1.4%) of samples tested. None of the Enterobacteriaceae isolates were resistant to meropenem or colistin. Similarly, all Enterococcus isolates remained susceptible to ampicillin, penicillin and vancomycin. Finding multi-drug resistant bacteria which are frequently isolated from human infections is concerning, although the contribution of the global food trade to the dissemination of resistance remains cryptic. These results suggest that imported plant-based foods may be an underappreciated source of clinically relevant resistant organisms. Further study is required to address these gaps in our understanding of the epidemiology of resistance, and the magnitude of the risk posed to human health by these organisms.

Exploring the persistence and spreading of antibiotic resistance from manure to biocompost, soils and vegetables

The main avenue in which antibiotic resistance enters soils is through the application of livestock manure. However, whether antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) persist and spread to vegetables with the application of manure and manure products is still unclear. This study assessed seven kinds of cultured ARB, 221 ARGs subtypes and three transposon genes in the vegetable production chain (from manure to biocompost, soils and vegetables). Results showed that at least 80% of ARB, ARGs and transposon genes were removed after aerobic composting. However, aerobic composting did not reduce the diversity of ARGs in pig and chicken manure. A total of 19 ARGs subtypes still persisted during aerobic composting. Compared to the temperature-thermophilic stage, the number of bacteria resistant to erythromycin, the relative abundance of ARGs and IS613 increased 1.7-4.9 times at the temperature-decreasing stage. Direct application of biocompost introduced 11 ARGs subtypes to pakchoi, but these ARGs did not present in biocompost-amended soil. A transposon gene tnpA was also detected in the biocompost-amended soil, but surprisingly was found in the control vegetable. This demonstrated that the transposon gene is intrinsic in pakchoi. Bacterial community analysis and network analysis revealed that a specific genus Terrisporobacter carrying tetO, tetW ermB and tnpA persisted in the vegetable production chain, which may generate a potential risk in the following production. Our study illuminates the persistence and spreading of antibiotic resistance in the vegetable production chain which could help manage the ecological risks arising from antibiotic resistance in manure sources.

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

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.

Purification and Characterization of Pasteuricin Produced by Staphylococcus pasteuri RSP-1 and Active against Multidrug-Resistant Staphylococcus aureus

Staphylococcus aureus is an important pathogen implicated in various diseases, including staphylococcal food poisoning. Bacteriocins are considered safe and effective antimicrobial substances for the prevention of the growth of pathogenic bacteria. In this article, we describe the purification and characterization of pasteuricin, a novel bacteriocin produced by Staphylococcus pasteuri RSP-1. A cell-free supernatant of S. pasteuri RSP-1 exerted strong antimicrobial activity against staphylococci, including methicillin-resistant S. aureus (MRSA), and gram-positive bacteria. The loss of antimicrobial activity upon treatment with proteolytic enzymes confirmed the proteinaceous nature of pasteuricin. A rapid and pronounced bactericidal effect of pasteuricin was confirmed by a live-dead bacterial viability assay. To our knowledge, pasteuricin is the first reported S. pasteuri bacteriocin that inhibits S. aureus. Because pasteuricin is characterized by strong antimicrobial activity and high stability, it has potential as an alternative antimicrobial agent to antibiotics.

Prevalence and Characterization of Staphylococcus aureus Isolated From Retail Vegetables in China

Staphylococcus aureus is a pathogen associated with serious community and hospital-acquired diseases. The aim of this study was to investigate the prevalence of S. aureus from retail vegetables in China and then characterized S. aureus isolates by antibiotic resistance, staphylococcal enterotoxin genes, spa-typing and multi-locus sequence typing. Of 419 retail vegetable samples from 39 cities in China during 2011-2016, 24 (5.73%) samples were positive for S. aureus and the geometric mean was 3.85 MPN/g. The prevalence of S. aureus was highest in lettuce (13/84, 15.48%) followed by tomato (7/110, 6.36%), caraway (2/87, 2.30%), and cucumber (2/128, 1.56%), whereas other vegetables were free of S. aureus. A total of 30 isolates were analyzed. For antibiotics susceptibility test, most isolates (93.3%) were resistant to ampicillin and penicillin, whereas all isolates were susceptible to linezolid, trimethoprim/sulphamethoxazole 1:19, nitrofurantoin, rifampicin, and teicoplanin. All isolates (30/30, 100%) were resistant or intermediate resistant to more than three tested antibiotics, including 9 isolates (30%) were resisted more than 10 antibiotics. Five isolates were resistant to cefoxitin and carried mecA genes which confirmed as MRSA. Of the 18 investigated SE genes, the sem gene was the most frequently detected (86.7%) followed by the sec (83.3%), sep (70.0%), seg (56.7%), sel (53.3%), seh (50.0%), seq (50.0%), sej (46.7%), seb (36.7%), sen (36.7%), and ser (33.3%) genes were harbored by more than one third of the isolates, whereas the seo and seu were detected in only 6.75% of the isolates. MLST and spa typing observed high genetic diversity in S. aureus isolated from retail vegetable in China. ST59-t437 was the predominant types (3/5, 60%) of MRSA isolates, whereas ST188-t189 was the predominant types (7/25, 28%) of MSSA isolates. Our study reflects that the retail vegetable in China could be contaminated with S. aureus but the levels of S. aureus were not very excessive. In addition, these isolates had virulence potential, most of them were enterotoxigenic and multiple antimicrobial resistance, should be draw public attention. These data have signification implications for epidemiological and public health studies of this pathogen.

Enterotoxigenicity and Antimicrobial Resistance of Staphylococcus aureus Isolated from Retail Food in China

Staphylococcus aureus is one of the most common causes of zoonotic agent in the world, which are attributable to the contamination of food with enterotoxins. In this study, a total of 1,150 S. aureus isolates were cultured from 27,000 retail foods items from 203 cities of 24 provinces in China in 2015 and were test for antimicrobial susceptibility. Additionally, the role of the genes responsible for the staphylococcal enterotoxins (SEA to SEE), methicillin resistance (mecA) and the toxigenic capabilities were also assessed. The results showed that 4.3% retail foods were contaminated with S. aureus, and 7.9% retail foods isolates were mecA positive. Some 97.6% of S. aureus isolates were resistant to at least one antimicrobial compound, and 57.5% of these were multi drug resistant (MDR). Resistance to penicillin (83.7%, 963/1,150), was common, followed by linezolid (67.7%, 778/1,150) and erythromycin (52.1%, 599/1,150). The isolates cultured from raw meats showed high levels of resistant to tetracycline (42.8%), ciprofloxacin (17.4%), and chloramphenicol (12.0%) and expressed a MDR phenotype (62.4%). A total of 29.7% S. aureus isolates harbored the classical SEs genes (sea, seb, sec, and sed). The sea and seb genes were the most frequent SEs genes detected. Of note, 22% of the SEs genes positive S. aureus harbored two or three SEs genes, and 16 isolates were confirmed with the capacity to simultaneously produce two or three enterotoxin types. Moreover, nearly 50% of the MRSA isolates were positive for at least one SE gene in this study. Therefore, it is important to monitor the antimicrobial susceptibility and enterotoxigenicity of MDR S. aureus and MRSA in the food chain and to use these data to develop food safety measures, designed to reduce the contamination and transmission of this bacterium.