BACKGROUND: Food-associated antibiotic-resistant bacteria can cause infections that may critically impact human health. The objectives of this study were to determine the microbial contamination level of green leafy vegetables and their antibiotic resistance pattern.
METHODS: Sixty-three samples of leafy vegetables were collected from Dammam Central Fruit and Vegetables Market from January to June 2023. The vegetables included lettuce (Lactuca sativa), parsley (Petroselinum crispum), and watercress (Nasturtium officinale). Samples were tested by standard microbiological techniques for identification and antibiotic susceptibility testing.
RESULTS: Eight types of bacteria belonging to six different genera were detected. Enterobacteriaceae family was represented by four genera: Klebsiella, Proteus, Morganella, and Enterobacter. The other two genera were Pseudomonas and Aeromonas. Enterobacter cloacae was the most abundant organism, followed by Pseudomonas putida and Aeromonas sobria. On the other hand, Morganella morganii, Aeromonas hydrophila, and Proteus mirabilis were the least abundant. The three vegetable types had different levels of bacterial contamination. All isolated organisms were sensitive to penicillin, cephalosporin, aminoglycoside, and fluoroquinolone. However, Klebsiella oxytoca, M. morganii, and K. pneumonia showed resistance to ampicillin. A. hydrophila, Morganella morganii, and E. cloacae showed resistance to amoxicillin. M. morganii and E. cloacae were found to be resistant to cefalotin. Moreover, A. hydrophila, M. morganii, and E. cloacae were resistant to cefoxitin. Again, A. hydrophila was found to be resistant to imipenem. Only M. morganii was resistant to Ciprofloxacin. Two isolates, P. mirabilis and M. morganii were resistant to tigecycline. Another two, M. morganii and P. mirabilis were resistant to Nitrofurantoin. Only M. morganii was found to be resistant to trimethoprim.
CONCLUSIONS: This study aligns with the broad consensus in the literature about the significance of bacterial contamination in vegetables and the public health implications. The unique focus on antibiotic resistance patterns adds an essential dimension to the existing body of knowledge.

Stemphylium leaf spot can result in significant losses to spinach seed, processing, and fresh market crops. Stemphylium isolates (n = 1,775) collected from 2000 to 2022 from spinach seed, leaves, and seed crop stem residues were used to assess the diversity of species associated with spinach. Eleven Stemphylium species were identified based on cmdA sequences: S. vesicarium (63.6% of isolates), S. beticola (48.9%), S. amaranthi (5.1%), S. eturmiunum (4.5%), S. astragali (4.0%), S. simmonsii (3.4%), and S. lucomagnoense, S. drummondii, S. gracilariae, S. lycopersici, and S. chrysanthemicola (each 0.6 to 1.7%). Only isolates of S. beticola, S. drummondii, and S. vesicarium were pathogenic to spinach. The incidence of spinach seed on which Stemphylium was observed ranged from 2.5 to 73.5% per seed lot, with S. vesicarium and S. beticola predominant. However, only 60.7 and 62.3% of isolates tested for these two species were pathogenic to spinach, respectively. Therefore, the incidence of Stemphylium species on spinach seed may not reflect accurately the risk of a seed lot carrying pathogenic isolates. Fused MAT1-1 and MAT1-2 genes were detected in isolates of S. vesicarium, but only MAT1-1 was detected in S. beticola isolates, which corroborates previous studies that have proposed the two species to be self-fertile. The duration of ascospore dispersal of S. beticola and S. vesicarium from spinach seed crop stem residues in western Washington, the primary region of spinach seed production in the USA, occurred from mid-winter to late spring or early fall, potentially serving as inoculum for the next season\'s spinach seed crops. Growers should incorporate residues into the soil after harvest to reduce inoculum production of these pathogens on spinach seed crop residues.

Consuming leafy vegetables with excessive thiophanate-methyl (TM) residue poses serious risks to human health. To realize rapidly and sensitively detecting TM in leafy vegetables, we developed a fluorescent probe based on zeolitic imidazolate framework-8-modified carbon dots using Hami melon as the green precursor (HM-CDs@ZIF-8). Meanwhile, the mechanism of HM-CDs@ZIF-8 for detecting TM was investigated and explained. The results of the performance tests showed that the prepared HM-CDs@ZIF-8 exhibited high sensitivity, excellent selectivity, robust anti-interference capability, reliable reproducibility and repeatability, and long-term stability. After optimization experiments, the fluorescence intensity of HM-CDs@ZIF-8 showed a strong linear correlation with the concentration of TM (0.00171-3.4239 mol/L) with a detection limit of 2.025 μmol/L. The HM-CDs@ZIF-8 was successfully applied to determine TM in spiked leafy vegetables with satisfactory recoveries of 96-105%. The relative standard deviations were in the range of 0.26-2.55%. The sensor has a promising application for detecting TM in leafy vegetables.

BACKGROUND: The first step in the contamination of leafy vegetables by human pathogens is their attachment to the leaf surface. The success of this is influenced strongly by the physical and chemical characteristics of the surface itself (number and size of stomata, presence of trichomes and veins, epicuticular waxes, hydrophobicity, etc.). This study evaluated the attachment of Salmonella enterica to 30 baby-leaf salads and tested whether the differences found among them were related to the following leaf traits: hydrophobicity, roughness, and epicuticular waxes.
RESULTS: Differences in susceptibility to contamination by S. enterica were found between the 30 baby-leaf salads investigated. The lowest attachment was found in wild lettuce (Lactuca serriola L.) and lamb\'s lettuce \'Trophy F1\' (Valerianella locusta [L.] Laterr.), with values of 1.63 ± 0.39 Log(CFU/cm2) and 1.79 ± 0.54 Log(CFU/cm2), respectively. Attachment was correlated with hydrophobicity (measured as contact angle) (r = -0.39) and epicuticular waxes (r = -0.81) but not with roughness (r = 0.24). The most important wax components for attachment were alcohols and, in particular, the three-dimensional (3D) wax crystals of C26 alcohol, but fatty acids probably also had a role. Both these compounds increased hydrophobicity. The presence of thymol, whose antimicrobial properties are well known, was found in lamb\'s lettuce.
CONCLUSIONS: The findings of this study can help to predict and control the attachment and contamination of leafy salads by enterobacteria. They also provide useful information for breeding programs aiming to develop cultivars that are less susceptible to human pathogens, enhancing the food safety of vegetables. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

In the U.S., baby spinach is mostly produced in Arizona (AZ) and California (CA). Characterizing the impact of growing region on the bacterial quality of baby spinach can inform quality management practices in industry. Between December 2021 and December 2022, baby spinach was sampled after harvest and packaging for microbiological testing, including shelf-life testing of packaged samples that were stored at 4°C. Samples were tested to (i) determine bacterial concentration, and (ii) obtain and identify bacterial isolates. Packaged samples from the Salinas, CA, area (n = 13), compared to those from the Yuma, AZ, area (n = 9), had a significantly higher bacterial concentration, on average, by 0.78 log10 CFU/g (P < 0.01, based on aerobic, mesophilic plate count data) or 0.67 log10 CFU/g (P < 0.01, based on psychrotolerant plate count data); the bacterial concentrations of harvest samples from the Yuma and Salinas areas were not significantly different. Our data also support that an increase in preharvest temperature is significantly associated with an increase in the bacterial concentration on harvested and packaged spinach. A Fisher\'s exact test and linear discriminant analysis (effect size), respectively, demonstrated that (i) the genera of 2,186 bacterial isolates were associated (P < 0.01) with growing region and (ii) Pseudomonas spp. and Exiguobacterium spp. were enriched in spinach from the Yuma and Salinas areas, respectively. Our findings provide preliminary evidence that growing region and preharvest temperature may impact the bacterial quality of spinach and thus could inform more targeted strategies to manage produce quality.
OBJECTIVE: In the U.S., most spinach is produced in Arizona (AZ) and California (CA) seasonally; typically, spinach is cultivated in the Yuma, AZ, area during the winter and in the Salinas, CA, area during the summer. As the bacterial quality of baby spinach can influence consumer acceptance of the product, it is important to assess whether the bacterial quality of baby spinach can vary between spinach-growing regions. The findings of this study provide insights that could be used to support region-specific quality management strategies for baby spinach. Our results also highlight the value of further evaluating the impact of growing region and preharvest temperature on the bacterial quality of different produce commodities.

BACKGROUND: Lettuce holds a prominent position in the year-round supply of vegetables, offering a rich array of health-beneficial substances, such as dietary fiber, phenolic compounds, lactucopicrin and lactucin. As such, its flavor has garnered increasing attention. Balancing the enhancement of beneficial compounds with the reduction of undesirable taste is a key focus of scientific research. To investigate short-term management to improve the nutritional quality and flavor of lettuce, combinations of different light intensities (200, 500 and 800 μm ol m-2 s-1) and temperatures (10 and 22 °C) were applied separately to \'Lollo Rosso\' and \'Little Butter Lettuce\' for 7 days before harvest.
RESULTS: The results obtained showed that increasing light intensity at low temperatures decreased nitrate content and increased soluble sugar, soluble protein, anthocyanin and phenolic compound content. In the case of lettuce flavor, the bitterness-related metabolites such as lactucin and lactucopicrin were reduced with high light intensity at a low temperature of 10 °C. With this combination, the fructose and glucose contents increased, significantly improving lettuce flavor.
CONCLUSIONS: Higher light intensity combined with low temperature for 7 days before harvest effectively improved the nutritional quality and flavor of lettuce, suggesting its great potential for use in horticultural practices. © 2024 Society of Chemical Industry.

Leafy plants are commonly consumed as vegetables in India due to their high nutrient and vitamin content. This study, conducted in Ambagarh Chowki (India), investigated the accumulation potential of 52 elements (including Al, As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Ho, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, P, Pb, Pr, Rb, Sb, Sc, Se, Sm, Sn, Sr, Tb, Te, Th, Ti, Tl, Tm, U, V, W, Y, Yb, and Zn) in seven leafy vegetable species, namely Amaranthus tricolor L., Corchorus olitorius L., Cordia myxa L., Hibiscus sabdariffa L., Ipomoea batatas (L.) Lam., Moringa oleifera Lam., and Spinacia oleracea L. Technique: Inductively coupled plasma mass spectrometry (ICP-MS) was employed for analysis. The maximum concentrations of elements such as Al, Ba, Be, Bi, Cd, Co, Cr, Fe, Ga, Ge, Li, Mn, Ni, Pb, Sb, Th, Tl, U, V, W, and REEs were observed in S. oleracea leaves, indicating their highest accumulation potential. In contrast, the maximum concentrations of As were found in H. sabdariffa leaves; Ca and Si in M. oleifera leaves; Mg, Sr, and Mo in A. tricolor leaves; and P, K, Cu, and Zn in C. myxa leaves, respectively. Twenty-one elements (Cr, Cd, Pb, Ni, Co, V, Cu, Zn, Fe, Mn, Th, Sb, Ba, Be, Li, Sr, Tl, U, Se, Sn, and REEs) exceeded permissible limits set by the WHO. The elevated hazard index values indicated significant non-carcinogenic effects. The sources of these elements could be attributed to a combination of geological factors and agricultural practices. This study highlights the need for further investigation into the potential health implications of consuming these vegetables in the aforementioned region.

Heavy metal contamination in leafy vegetables poses significant health risks, highlighting the urgent need for stringent monitoring and intervention measures to ensure food safety and mitigate potential adverse effects on public health. This study investigates the levels of heavy metals, including cadmium (Cd), chromium (Cr), nickel (Ni), lead (Pb), zinc (Zn), and copper (Cu), in locally grown and commercially available leafy vegetables, comparing them to the safety limits established by WHO/FAO. The results revealed that levels of Cd, Cr, Ni, and Pb in the vegetables exceeded WHO/FAO limits, while Zn and Cu remained within permissible bounds. Marketed vegetables exhibited higher metal concentrations than those from nearby farms. For Cu (0.114-0.289 mg/kg) and Zn (0.005-0.574 mg/kg), the daily intake of metals (DIM) was below the dietary intake (DI) and upper limit (UL). Cd\'s DIM (0.031-0.062 mg/kg) remained below the UL but exceeded the DI. Marketed kale and mint surpassed both DI and UL limits for Ni, while local produce only exceeded the DI. All vegetables had DIM below the DI, except for mint and kale. For Pb, every vegetable exceeded DI limits, with market samples contributing significantly. Cr\'s DIM ranged from 0.028 to 1.335 mg/kg, for which no set maximum daily intake exists. The health risk index (HRI) values for Zn, Cd, Cu, Ni, and Pb suggested potential health risks associated with leafy greens, while Cr\'s HRI was below 1. The study underscores the need for stringent monitoring and intervention measures to mitigate the health risks posed by heavy metal contamination in leafy vegetables. These findings suggest that consuming these leafy greens may put consumers at considerable risk for health problems related to Cd, Cu, Ni, Pb, and Zn exposure.

Green leafy vegetables are essential for a balanced diet, providing vital nutrients for overall well-being. However, concerns arise due to contamination with toxic substances, such as arsenic, posing risks to food safety and human health. This study analyzes inorganic (iAs), monomethyl (MMA), and dimethyl arsenic (DMA) in specific leafy vegetables (Amaranthus tricolor L., Corchorus olitorius L., Cordia myxa L., Hibiscus sabdariffa L., Ipomoea batatas (L.) Lam., Moringa oleifera Lam., and Spinacia oleracea L.) grown in the heavily polluted Ambagarh Chouki region, Chhattisgarh, India. Concentrations of DMA, MMA, and iAs ranged from 0 to 155, 0 to 7, and 131 to 3579 mg·kg-1, respectively. The health quotient (HQ) for iAs ranged between 0.37 and 3.78, with an average value of 2.58 ± 1.08.

Nitrate is prevalent in environment and present in foods of plant origin as part of nitrogen cycle. It is now one of the most pervasive and persistent contaminants in animal food chain. Present work is focussed on development of a novel green nanosensor using corn silk extract for nitrate detection in leafy vegetables (Spinacia oleracea, Amaranthus viridis and Amaranthus cruentus). The green reduced graphene oxide (rGO) and a nanocomposite (G-Fe3O4@rGO) was synthesized for the first-time using corn silk extract and used for fabrication of the nanosensor. Various characterization techniques were used to expose the optical, crystallographic and surface morphology details of the nanosubstrates. Electrochemical studies of the fabricated nanosensor were conducted using the electrochemical impedance spectroscopy (EIS) technique. The performance of NiR/G-Fe3O4@rGO/ITO green nanosensor was the best, in terms of the electrochemical performance parameters among different fabricated nanosensors in the study. The developed green nanosensor demonstrated high sensitivity of 122.1 Ohm/log(mg/L)/cm2 and lower limit of detection 0.076 mg/L for detection of nitrate in leafy vegetables. The green nanosensor exhibited higher recovery rates (>86%) and high precision in nitrate detection in leafy vegetables (RSD <5.2%). Validation studies were conducted with HPLC technique also. The results of green nanosensor were found in good agreement with HPLC studies (p < 0.05) highlighting the market acceptability with usefulness and effectiveness of the nanosensor for food quality and safety evaluation.