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Shikonin has anticancer, anti-inflammatory, and wound healing activities. Vibrio vulnificusis an important marine foodborne pathogen with a high fatality rate and rapid pathogenesis that can infect humans through ingestion and wounds. In this study, the antibacterial activity and possible antibacterial mechanism of shikonin against V. vulnificuswere investigated. In addition, the ability of shikonin to control V. vulnificusinfection in both pathways was assessed by artificially contaminated oysters and full-thickness excised skin-infected mice. Shikonin treatment can cause abnormal cell membrane function, as evidenced by hyperpolarization of the cell membrane, significant decreased intracellular ATP concentration (p< 0.05), significant increased intracellular reactive oxygen species and malondialdehyde content (p< 0.05), decreased cell membrane integrity, and changes in cell morphology. Shikonin at 40 and 80 μg/mL reduced bacterial numbers in shikonin-contaminated oysters by 3.58 and 2.18 log colony-forming unit (CFU)/mL. Shikonin can promote wound healing in mice infected with V. vulnificusby promoting the formation of granulation tissue, hair follicles, and sebaceous glands, promoting epithelial cell regeneration and epidermal growth factor production. These findings suggest that shikonin has a strong inactivation effect on V. vulnificusand can be used in food production and wound healing to effectively control V. vulnificusand reduce the number of diseases associated with it.

Pseudomonas aeruginosabiofilm formation has been considered to be an important determinant of its pathogenicity in most infections. The antibiofilm activity of trans-cinnamaldehyde (TC) against P. aeruginosawas investigated in this study. Results demonstrated that the minimum inhibitory concentration (MIC) of TC against P. aeruginosawas 0.8 mg/mL, and subinhibitory concentrations (SICs) was 0.2 mg/mL and below. Crystal violet staining showed that TC at 0.05–0.2 mg/mL reduced biofilm biomass in 48 h in a concentration-dependent mode. The formation area of TC-treated biofilms was significantly declined (p< 0.01) on the glass slides observed by light microscopy. Field-emission scanning electron microscopy further demonstrated that TC destroyed the biofilm morphology and structure. Confocal laser scanning microscopic observed the dispersion of biofilms and the reduction of exopolysaccharides after TC treatment stained with concanavalin A (Con-A)-fluorescein isothiocyanate conjugate and Hoechst 33258. Meanwhile, TC caused a significant decrease (p< 0.01) in the component of polysaccharides, proteins, and DNA in extracellular polymeric substance. The swimming and swarming motility and quorum sensing of P. aeruginosawas also found to be significantly inhibited (p< 0.01) by TC at SICs. Furthermore, SICs of TC repressed the several genes transcription associated with biofilm formation as determined by real-time quantitative polymerase chain reaction. Overall, our findings suggest that TC could be applied as natural and safe antibiofilm agent to inhibit the biofilm formation of P. aeruginosa.

Coenzyme Q0(CoQ0) is a natural compound found in Antrodia cinnamomea, which has a variety of biological activities. Here, the antibacterial activity and possible antibacterial mechanism of CoQ0against Escherichia coliwere investigated. The antibacterial effect was evaluated by determining minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values, and by assessing bacterial survival and the effect on the growth of E. coliafter CoQ0treatment in Luria-Bertani (LB) broth. To reveal the antibacterial mechanism of CoQ0, changes in intracellular adenosine triphosphate (ATP) concentration, membrane potential, and bacterial protein content, as well as effects on cell morphology and membrane integrity, were investigated. Both the MICs and MBCs of CoQ0against E. coliwere 0.1 mg/mL. After treatment of E. coli(6.5 log colony-forming units/mL) with 0.1 mg/mL of CoQ0in LB broth for 3 h, the number of viable cells dropped below the detection limit. In addition, CoQ0treatment resulted in the reduction in intracellular ATP concentration, cell membrane hyperpolarization, decreased bacterial protein concentrations, and damage to cell membrane integrity and cellular morphology. These results indicated that CoQ0has effective antibacterial activity against E. coli, suggesting potential applications in food industry safety.

Necrotizing enterocolitis (NEC) is a serious inflammatory intestinal disorder with a high mortality rate, which occurs most commonly in newborn infants. Cronobacter sakazakii, a common contaminant in infant formula, is associated with NEC. However, its role in NEC pathogenesis is unknown, and there are still no effective treatments for NEC. Currently, natural bioactive products have been investigated for their beneficial effects in preventing microbial infection. In this study, a neonatal mouse intestinal inflammation model was used to examine the protective effects of citral (a natural bioactive product) on C. sakazakii-induced intestinal inflammation and damages. It was shown that citral reduced the number of C. sakazakiicells in ileal tissues, and mice treated with citral had a significantly higher body weight than C. sakazakii-infected mice. Citral treatment also ameliorated serious ileal tissue damages, including epithelial sloughing, villous rupture, and enterocyte apoptosis. C. sakazakiiinfection upregulated the messenger RNA transcription levels of several inflammation-associated genes, increased production of IL-6 and TNF-α, and activated the NF-κB and MAPK signaling pathways in ileal tissues. Citral treatment mitigated these inflammatory responses. The apoptotic index and activities of caspase 3, 8, and 9 increased in murine ileum after C. sakazakiiinfection, but citral inhibited both enterocyte apoptosis and activations of these caspase. These findings suggest that citral has protective effects on C. sakazakii-induced intestinal inflammation in newborn mice, and it may play a future role in the management of C. sakazakii-associated infections and diseases.

AbstractPunicalagin, one of the main active compounds in pomegranate peel, has been reported to possess many properties, including antioxidant, antimicrobial, antiviral, and immunosuppressive activities. The aim of this study was to investigate the antibacterial effect of punicalagin against Staphylococcus aureusand possible mode of action. Growth inhibition activity was examined by the agar diffusion method. Then agar dilution method was adopted to determine the minimum inhibitory concentration (MIC). The effects of punicalagin on cell membrane were assessed by measuring potassium efflux. Morphological changes of S. aureuswere assessed by scanning and transmission electron microscopy. Crystal violet assay was applied to investigate antibiofilm activity of punicalagin. Punicalagin exhibited good antistaphylococcal effect with an MIC of 0.25 mg/mL. An increase of potassium efflux was observed when cells were treated with punicalagin at 2 × MIC. Punicalagin induced morphological damages to the cell membrane. Moreover, punicalagin exerted a remarkable inhibitory effect on biofilm formation of S. aureus. These findings suggest that punicalagin has antimicrobial and antibiofilm activities against S. aureusand may have potential application to control S. aureuscontamination in food industry.

Shigella sonnei, the causative agents of bacillary dysentery, remains a significant threat to public health. Litsea cubebaessential oil (LC-EO), one of the natural essential oils, exhibited promising biological activities. In this study, the antibacterial effects and possible mechanisms of LC-EO on S. sonneiand its application in lettuce medium were investigated. The minimum inhibitory concentration (MIC) of LC-EO against S. sonneiATCC 25931 and CMCC 51592 was 4 and 6 μL/mL, respectively. The LC-EO could inhibit the growth of S. sonnei, and decreased S. sonneito undetectable levels with 4 μL/mL for 1 h in Luria-Bertani broth. The antibacterial mechanism indicated that after the treatment of LC-EO, the production of reactive oxygen species and the activity of superoxide dismutase were significantly elevated in S. sonneicells, and eventually led to the lipid oxidation product, the malondialdehyde content that significantly increased. Moreover, LC-EO at 2 MIC could destroy 96.51% of bacterial cell membrane integrity, and made S. sonneicells to appear wrinkled with a rough surface, so that the intracellular adenosine triphosphate leakage was about 0.352–0.030 μmol/L. Finally, the results of application evaluation indicated that the addition of LC-EO at 4 μL/mL in lettuce leaves and 6 μL/mL in lettuce juice could decrease the number of S. sonneito undetectable levels without remarkable influence on the lettuce leaf sensory quality. In summary, LC-EO exerted strong antibacterial activity and has the potential to control S. sonneiin food industry.

AbstractCronobacter sakazakii(formerly Enterobacter sakazakii) is an opportunistic pathogen that causes meningitis, sepsis, and necrotizing enterocolitis in neonates and infants through consumption of contaminated milk-based foods. In this study, the prevalence of C. sakazakiiin 705 retail milk-based infant and baby food samples was investigated in 12 cities in Shaanxi, China, in 2010 and 2012. One hundred and nineteen samples (16.9%) were C. sakazakiipositive. The isolates were further characterized for antimicrobial susceptibility to 14 antibiotics, pulsed-field gel electrophoresis profiles, and presence of the virulence genes. Samples of brand W, Y, A, and G in 2010 and 2012 were C. sakazakiipositive. All isolates recovered in 2010 and 2012 were susceptible to levofloxacin and cefoperazone. In 2012, no isolate was resistant to gentamicin, cefoxitin, chloramphenicol, gatifloxacin, ciprofloxacin, and ceftriaxone. Antibiotic resistance of the isolates was most commonly found to rifampicin, amoxicillin-clavulanic acid, streptomycin, tetracycline, and ampicillin in both 2010 and 2012, except to trimethoprim/sulfamethoxazole in 2012. Pulsed-field gel electrophoresis profiles indicated that C. sakazakiiisolates were genotypically diverse, although these isolates were prevalent in infant and baby foods with the same brand. A total of 34 virulence gene profiles of the C. sakazakiiisolates in 2010 and 2012 were detected. Isolates that co-carried hly-ompX-eitCBAD-iucABCD/iutAgenes in 2012 were significantly (p < 0.05) more prevalent than those in 2010. The results added new epidemiological evidence for the widespread occurrence of C. sakazakiiin retail milk-based infant and baby foods and this should be an indicator of potential health risk for consumers.

AbstractCronobacter sakazakiiis an opportunistic pathogen transmitted by food that affects mainly newborns, infants, and immune-compromised adults. In this study, the antibacterial activity of ferulic acid was tested against C. sakazakiistrains. Minimum inhibitory concentration of ferulic acid against C. sakazakiistrains was determined using the agar dilution method. Changes in intracellular pH, membrane potential and intracellular ATP concentration were measured to elucidate the possible antibacterial mechanism. Moreover, SYTO 9 nucleic acid staining was used to assess the effect of ferulic acid on bacterial membrane integrity. Cell morphology changes were observed under a field emission scanning electron microscope. The minimum inhibitory concentrations of ferulic acid against C. sakazakiistrains ranged from 2.5 to 5.0 mg/mL. Addition of ferulic acid exerted an immediate and sustained inhibition of C. sakazakiiproliferation. Ferulic acid affected the membrane integrity of C. sakazakii, as evidenced by intracellular ATP concentration decrease. Moreover, reduction of intracellular pH and cell membrane hyperpolarization were detected in C. sakazakiiafter exposure to ferulic acid. Reduction of green fluorescence indicated the injury of cell membrane. Electronic microscopy confirmed that cell membrane of C. sakazakiiwas damaged by ferulic acid. Our results demonstrate that ferulic acid has moderate antimicrobial activity against C. sakazakii. It exerts its antimicrobial action partly through causing cell membrane dysfunction and changes in cellular morphology. Considering its antimicrobial properties, together with its well-known nutritional functions, ferulic acid has potential to be developed as a supplement in infant formula or other foods to control C. sakazakii.

AbstractPomegranate rind has been found to inhibit numerous pathogens, mostly attributed to its tannin fraction. The present study was conducted to investigate the quorum sensing (QS) inhibition effect of tannin-rich fraction from pomegranate rind (TFPR) by using an indicator strain Chromobacterium violaceum. Meanwhile, its effect on biofilm formation and motility of Escherichia coliwas evaluated. It was shown that TFPR inhibited QS-regulated violacein pigment production. Biofilm formation and motility of E. coliwere also hindered by TFPR. Transcriptional analysis further showed that TFPR repressed expressions of curli genes (csgBand csgD) and various motility genes (fimA, fimH, flhD, motB, qseB, and qseC). Our findings indicated that TFPR has potential application for controlling E. colicontaminations or biofilms in the food industry.

AbstractThe aim of the study was to survey three foodborne pathogens in kiwifruit orchards as a continuous monitoring program. A total of 193 samples were collected from 11 kiwifruit orchards in Shaanxi province in October 2013. Among the 193 samples, 68 Escherichia coliisolates were recovered, while no Staphylococcus aureusand Salmonellawas recovered. All E. coliisolates were characterized by antimicrobial susceptibility testing, detection of virulence genes, and the ability to produce biofilm formation. The isolates were further examined by random amplified polymorphic DNA (RAPD) analysis. E. coliisolates displayed resistance most frequently to tetracycline (48.5%). Two E. coliisolates (2.9%) were positive for the eaegene (the intimin gene). All E. coliisolates lacked the ability to make biofilm formation. Multilocus sequence typing analysis demonstrated that one isolate in kiwifruit orchards shared the same sequence type with a human clinical isolate. RAPD results showed a close relationship among E. coliisolates from fresh fruit, fallen fruit, soil, air, and irrigation water. This study could provide a further understanding of microbial contamination in kiwifruit orchards based on our previous study and help growers take appropriate measures for prevention.

Abstractβ-Lactamases and extended-spectrum β-lactamases (ESBLs) producing pathogenic bacteria were widely studied previously in China, but were seldom focused on foodborne Salmonella. In this study, an investigation concerning β-lactamases and ESBLs producing Salmonellarecovered from retail raw chickens was performed. Sixty of 699 foodborne Salmonellaisolates were detected as β-lactamases and ESBLs-producing ones that covered 12 Salmonellaserotypes and exhibited different pulsed-field gel electrophoresis genotypes. Forty-four of 60 β-lactamases and ESBLs-producing strains were simultaneously resistant to ampicillin, amoxicillin/clavulanic acid, ceftiofur, ceftriaxone, and cefoxitin. The most commonly detected β-lactamases and ESBLs-encoding gene was blaTEM-1(n=44), followed by blaOXA-1(n=38), blaCMY-2(n=29), blaPSE-1-like(n=1), blaCTX-M-3(n=16), and blaCTX-M-15(n=1), respectively. Fourteen, 24, 21, and 1 isolates were detected simultaneously positive for 1, 2, 3, and 4 of the detected β-lactamases and ESBLs-encoding genes, respectively. A Salmonellastrain simultaneously co-carrying blaTEM-1, blaOXA-1, blaCMY-2, and blaCTX-M-3was first reported in the present study. Amino acid substitution of Trp244Cys/His247Leu was detected in PSE-1, Val218Asp in CMY-2, and Asp242Gly in CTX-M-15 enzymes, respectively. A difference was found among the amino acid sequences of the detected OXA-1, CMY-2, CTX-M, PSE-1, and TEM-1. The results demonstrated that β-lactamases and ESBLs were emerging and prevalent in foodborne Salmonella.

AbstractThe aim of the study was to investigate the prevalence, distribution, and diversity of three foodborne bacteria in kiwifruit orchards and processing plants. Fourteen kiwifruit orchards and two processing plants in Shaanxi province were visited for sampling in 2012. Fruit samples and environmental samples in orchards and plants were taken for isolation of Escherichia coli, Staphylococcus aureus, and Salmonella. All isolates were characterized by antimicrobial susceptibility testing and detection of virulence genes. Selected isolates were further examined by pulsed-field gel electrophoresis (PFGE) analysis. In total, 160 E. coliisolates and 14 S. aureusisolates were recovered from 407 samples from orchards and plants, while no Salmonellawas recovered. E. coliisolates displayed resistance most frequently to streptomycin (65.6%), and S. aureusisolates displayed resistance most frequently to erythromycin (21.4%). Three E. coliisolates (1.9%) were positive for stx2 and two S. aureusisolates (14.3%) were positive for both seband seh. Seventy-seven E. coliisolates and 14 S. aureusisolates were analyzed by PFGE. PFGE results showed that both E. coliand S. aureusisolates were diverse, and blades for slicing during the processing could be an important contamination source. This study could provide useful information for kiwifruit growers and industry to establish proper management practices that help minimize the chance of microbial contamination from farm to table.

AbstractFour hundred sixty-two nalidixic acid– and/or ciprofloxacin-resistant Salmonellaisolates were examined for presence of quinolone-resistance mechanisms. A total of 339 amino acid substitutions were identified in GyrA (204) and ParC (135). Ser83Phe/Asp87Gly (29.4%) were most commonly detected in GyrA in 136 isolates, and to a lesser extent of Asp87Asn (22.8%), Asp87Gly (19.1%), Ser83Phe/Asp87Asn (19.1%), and Ser83Tyr (5.1%). Ser80Arg (97.0%) was detected in ParC in 132 isolates. Simultaneous mutations in GyrA and ParC (n=109) were commonly detected to be Ser83Phe/Asp87Gly(GyrA)-Ser80Arg(ParC) (35.8%), Asp87Asn(GyrA)-Ser80Arg(ParC) (22.9%), and Ser83Phe/Asp87Asn(GyrA)-Ser80Arg(ParC) (21.1%). qnrA, qnrB, qnrS, aac(6′)-Ib, qepA, and oqxAB were detected in 52 (11.3%), 64 (13.9%), 11(2.4%), 107 (23.2%), 6 (1.3%), and 194 (42.0%) of 462 isolates, respectively. Isolates carried more qnr, aac(6′)-Ib, qepA, and oqxAB genes, and amino acid substitution in GyrA and ParC was more resistant to nalidixic acid and fluoroquinolones.

AbstractChlorogenic acid (CA) has been reported to inhibit several pathogens, but the influence of subinhibitory concentrations of CA on virulence expression of pathogens has not been fully elucidated. The aim of this study was to explore the effect of CA on the virulence factor production of Staphylococcus aureus. The minimum inhibitory concentration (MIC) of CA against S. aureuswas determined using a broth microdilution method. Hemolysin assays, coagulase titer assays, adherence to solid-phase fibrinogen assays, Western blot, and real-time reverse transcriptase-polymerase chain reaction were performed to evaluate the effect of subinhibitory concentrations of CA on the virulence factors of S. aureus. MIC of CA against S. aureusATCC29213 was found to be 2.56 mg/mL. At subinhibitory concentrations, CA significantly inhibited the hemolysis and dose-dependently decreased coagulase titer. Reduced binding to fibrinogen and decreased production of SEA were observed with treatment of CA at concentrations ranging from 1/16MIC to 1/2MIC. CA markedly inhibited the expression of hla, sea, and agrgenes in S. aureus. These data demonstrate that the virulence expression of S. aureuscould be reduced by CA and suggest that CA could be potentially developed as a supplemental strategy to control S. aureusinfection and to prevent staphylococcal food poisoning.

AbstractThe aims of this study were to evaluate the occurrence of methicillin-resistant Staphylococcus aureus(MRSA) in retail foods in Shaanxi, China and to investigate antimicrobial resistance and molecular characteristics of these strains. A total of 1979 retail food samples were randomly collected during 2008–2012 from supermarkets and farmers markets and screened for S. aureus, and then S. aureusisolates were further examined to determine whether they were MRSA. MRSA isolates were further characterized by antimicrobial susceptibility test, pulsed-field gel electrophoresis, spatyping, multilocus sequence typing, and SCCmectyping, and were examined for genes encoding enterotoxins, exfoliative toxins, Panton-Valentine leukocidin (pvl), and toxic shock syndrome toxin 1. Among all the samples examined, four (1.4%) raw milk samples, six (2.3%) chicken samples, one (0.6%) pork sample, three (0.6%) ready-to-eat food samples, and three (2.5%) dumpling samples were positive for MRSA. No MRSA isolates were recovered from infant foods. A total of 23 MRSA isolates were recovered from the 17 MRSA-positive samples. Antimicrobial susceptibility tests showed that, among these MRSA isolates, resistance was most frequently observed to penicillin, ampicillin, oxacillin, cefoxitin, and clindamycin (each 100%), followed by erythromycin (95.7%) and clarithromycin (87.0%). The commonly detected toxin genes were pvl, seg, seb, sed, followed by see, sec, and sei. Seven spatypes (t189, t377, t437, t899, t10793, t5762, and a new spatype) and three SCCmectypes (II, IVb, and V) were identified. More than half (52.2%) of the MRSA isolates belonged to ST9, followed by ST88, ST59, ST188, ST72, and ST630. Our findings indicate that MRSA in food could be from both animal and human origin. Although the prevalence is low, the presence of multidrug resistant and enterotoxigenic MRSA strains in foods poses a potential threat to consumers and emphasizes the need for better control of sources of contamination.

AbstractPomegranate rind has been reported to inhibit several foodborne pathogens, and its antimicrobial activity has been attributed mainly to its tannin fraction. This study aimed to investigate the antimicrobial activity of the tannin-rich fraction from pomegranate rind (TFPR) against Listeria monocytogenesand its mechanism of action. The tannin-related components of TFPR were analyzed by high-performance liquid chromatography and liquid chromatography–mass spectrometry, and the minimum inhibitory concentration (MIC) of TFPR was determined using the agar dilution method. Extracellular potassium concentration, the release of cell constituents, intra- and extracellular ATP concentrations, membrane potential, and intracellular pH (pHin) were measured to elucidate a possible antibacterial mechanism. Punicalagin (64.2%, g/g) and ellagic acid (3.1%, g/g) were detected in TFPR, and the MICs of TFPR were determined to be 1.25–5.0 mg/mL for different L. monocytogenesstrains. Treatment with TFPR induced a decrease of the intracellular ATP concentration, an increase of the extracellular concentrations of potassium and ATP, and the release of cell constituents. A reduction of pHinand cell membrane hyperpolarization were observed after treatment. Electron microscopic observations showed that the cell membrane structures of L. monocytogeneswere apparently impaired by TFPR. It is concluded that TFPR could destroy the integrity of the cell membrane of L. monocytogenes, leading to a loss of cell homeostasis. These findings indicate that TFPR has the potential to be used as a food preservative in order to control L. monocytogenescontamination in food and reduce the risk of listeriosis.

AbstractListeria monocytogenesis an important foodborne pathogen of public health concern. A total of 902 retail food samples, including 342 ready-to-eat (RTE) foods, 366 infant foods, and 194 raw chickens were collected randomly in supermarkets and farmers' markets in 12 geographic areas in Shaanxi Province, China and screened for L. monocytogenes. All L. monocytogenesisolates were characterized by antimicrobial susceptibility testing, serotyping, and pulsed-field gel electrophoresis (PFGE). Twenty-seven (3.0%) samples were positive for L. monocytogenes, and 39 L. monocytogenesisolates were recovered from positive samples. Of these L. monocytogenesisolates, 21 isolates (53.8%) showed resistance to at least one antimicrobial. The isolates displayed resistance most frequently to oxacillin (18 isolates, 46.2%), followed by tetracycline (five isolates, 12.8%), erythromycin (four isolates, 10.3%), trimethoprim/sulfamethoxazole (three isolates, 7.7%), chloramphenicol (two isolates, 5.1%), and vancomycin (one isolate, 2.6%). All isolates were sensitive or displayed intermediate resistance to gentamicin, ampicillin, ciprofloxacin, and amikacin. Four serotypes including serotype 1/2b, 4b, 4e, and 1/2a were identified in those foodborne isolates. PFGE analysis demonstrated that some isolates with the same PFGE patterns came from different food sources, and isolates from the same food source tend to cluster closely. Presence of L. monocytogenesof clinically important serotypes in retail foods and their antimicrobial resistance constitute a potential risk for the public. Appropriate measures should be taken by government, industry, and consumers to reduce the risk posed by this ubiquitous pathogen.

AbstractStaphylococcus aureusis commonly present in humans and animals. The aim of this study was to investigate antimicrobial resistance and genetic characteristics of S. aureusfrom food and food animals in Shaanxi Province in China. A total of 332 nasal swabs, breast skin swabs, raw milk, and pork samples were collected from local pig, dairy farms, or local grocery stores and screened for the presence of S. aureus. S. aureusisolates were characterized using antimicrobial susceptibility, pulsed-field gel electrophoresis (PFGE) analysis, and polymerase chain reaction for detecting pvland mecAgenes. Methicillin-resistant S. aureus(MRSA) strains were additionally tested for SCCmectype and exfoliative toxin genes. The prevalence of S. aureuswas 30.6% in pig nasal swabs, 32.5% in pork, 25.7% in cow nasal swabs, 30.8% in cow breast skin swabs, and 29.3% in milk samples. Resistances were common among isolates tested against erythromycin (65.7%), tetracycline (65.7%), ciprofloxacin (52.7%), followed by gentamicin (36.7%), chloramphenicol (23.1%), cefoxitin (8.3%), and oxacillin (7.7%), but no isolate was resistant to vancomycin, amikacin, or cefoperazone. pvlgene was found in the isolates from all types of samples except from cow nasal swabs. Fourteen isolates from pig nasal swabs contained mecAgene and were considered as MRSA. PFGE analysis showed that nasal isolates differed from food isolates, but isolates from the same animal source appeared to cluster closely. The PFGE patterns of MRSA isolates were different from other S. aureusisolates from pig nasal cavity even though they were from the same source. All the MRSA isolates belonged to SCCmectype IVb. No isolates contained exfoliative toxin genes. These findings indicated that S. aureus, including multidrug-resistant S. aureus, are widely spread in food animals and animal-derived foods in Shaanxi Province, China. MRSA isolates from pigs may pose potential health risks for workers in swine farms and the community at large.

Shigella flexneri, a common Gram-negative foodborne pathogen, is widely distributed in fresh-cut fruits and vegetables, unpasteurized milk, and food processing environments. The aims of this study were to evaluate the antibacterial effects of 405-nm light-emitting diode (LED) treatment on S. flexneriand to investigate the possible mechanism. The results showed that LED irradiation (360 min) reduced the number of S. flexneriin phosphate-buffered saline by 3.29 log colony-forming unit (CFU)/mL (initial bacterial count: 6.81 log CFU/mL). The cells in reconstituted infant formula, cells on fresh-cut carrot slices, and biofilm-associated cells on stainless steel surfaces were reduced by 1.83 log CFU/mL, 7.00 log CFU/cm2, and 4.35 log CFU/cm2following LED treatment for 360, 120, and 120 min, respectively. LED treatment damaged both DNA and cell wall of S. flexneriand changed cell morphology and cell membrane permeability. In addition, LED treatment decreased total cell protein concentration of S. flexneri. These results indicated that 405-nm LED treatment effectively controlled S. flexnericontamination of foods and food contact surfaces and that the bacterial inactivation may be the result of damage to multiple cellular components. These findings highlight the potential of LED technology in controlling S. flexneriduring food processing, storage, and preparation.

Antimicrobial resistance (AMR) is a major public health challenge and spreads through humans, animals, and the environment. Many reports show that AMR genes (ARGs) or phenotypes can be transferred from food animals to humans. However, the level and correlation of AMR in different nodes of the poultry meat supply chain are still poorly understood. Herein, 225 Escherichia coliisolates were recovered from chilled chicken samples from markets (123) and chicken fecal samples from farms (102) in Zhejiang Province, China. The dominant sequence types (STs) were ST155 (8.89%), ST48 (7.56%), and ST10 (7.11%), which are common in chicken and fecal samples. Antimicrobial susceptibility testing (AST) analysis showed that the E. coliisolates from fecal samples and retail chickens were resistant to ampicillin (61.77% and 63.42%, respectively) and trimethoprim (56.87% and 52.85%). Moreover, 36.59% of the E. coliisolates from chilled chickens and 39.22% of the isolates from fecal samples were resistant to three or more antimicrobial agents. A total of 59 ARGs were identified in sequenced E. coligenomes, including the mcr-1gene involved in colistin resistance. The E. colifrom farms and markets could be clustered in the same branch according to core single nucleotide polymorphisms. In addition, toxin genes astAand hlyEwere also predicted in 86.5% (32/37) and 13.5% (5/37) of the above genomes, respectively. Taken together, these findings demonstrated that E. coliisolates from markets and farms showed similar AMR patterns, suggesting that E. colistrains in markets may originate from farms.