Salmonella is a leading cause of foodborne disease worldwide and ready-to-eat (RTE) foods are regarded as a major source of infection and outbreak. In recent years, the consumption of Chinese RTE ...foods has raised markedly with the pace of life increasing. However, the prevalence of Salmonella in these foods in China and its potential risk to public health has not been well determined and evaluated. This study was undertaken to investigate the prevalence of Salmonella in Chinese retail RTE food products and to determine serotype distribution, antimicrobial resistance, virulence, and genetic diversity of recovered Salmonella isolates. Out of the 539 RTE food products collected and tested from July 2011 to May 2014, 19 (3.5%) were positive for Salmonella. The contamination levels of Salmonella were mostly in the range of 0.3–10 most probable number (MPN)/g, with one sample exceeding 110 MPN/g. Among the 50 isolates identified, 37 isolates (74.0%) were resistant to at least one antimicrobial, while 21 isolates (42.0%) were resistant to more than three antimicrobials. High rates of resistance were observed for tetracycline (56.0%), ampicillin (38.0%), and streptomycin (34.0%). PCR analysis of 15 virulence genes showed that the avrA, ssaQ, mgtC, siiD, sopB, and bcfC genes were detected in all 50 isolates, whereas the genes located on plasmid and prophage varied significantly among the isolates. Ten distinct serovars were identified and S. Derby, S. Meleagridis, S. Enteritidis, and S. Senftenberg were the most prevalent serovars. A total of 11 sequence types by multilocus sequence typing and 20 profiles by pulsed-field gel electrophoresis were generated for the 20 selected isolates and the combination of these two methods presented a better knowledge of genetic diversity of Salmonella isolates. The study provided a systematical surveillance on prevalence of Salmonella in Chinese RTE foods and indicates its potential risk to public health.
•High prevalence of Salmonella contamination in ready-to-eat foods was determined.•S. Derby, S. Enteritidis, S. Meleagridis were the predominant serovars recovered.•Salmonella isolates showed a high prevalence of antibiotic resistance.•Salmonella isolates exhibited a wide range of pathogenicity determinants.•The combination of MLST and PFGE presented a better knowledge of genetic diversity.
is causing listeriosis, a rare but severe foodborne infection. Listeriosis affects pregnant women, newborns, older adults, and immunocompromised individuals. Ready-to-eat (RTE) foods are the most ...common sources of transmission of the pathogen This study explored the virulence factors and antibiotic resistance in
strains isolated from ready-to-eat (RTE) foods through
and
testing by whole-genome sequencing (WGS). The overall positivity of
in RTE food samples was 3.1% and 14 strains were isolated.
ST8, ST2763, ST1, ST3, ST5, ST7, ST9, ST14, ST193, and ST451 sequence types were identified by average nucleotide identity, ribosomal multilocus sequence typing (rMLST), and core genome MLST. Seven isolates had serotype 1/2a, five 1/2b, one 4b, and one 1/2c. Three strains exhibited
resistance to ampicillin and 100% of the strains carried the
,
,
,
,
, and
resistance genes. In addition, the
,
, and
genes were detected, which conferred resistance to stress and disinfectants. All strains harbored
,
, and
genes almost thirty-two the showed the
, and
genes. One isolate exhibited a type 11 premature stop codon (PMSC) in the
gene and another isolate a new mutation (deletion of A in position 819). The Inc18(rep25), Inc18(rep26), and N1011A plasmids and MGEs were found in nine isolates. Ten isolates showed CAS-Type II-B systems; in addition, Anti-CRISPR AcrIIA1 and AcrIIA3 phage-associated systems were detected in three genomes. These virulence and antibiotic resistance traits in the strains isolated in the RTE foods indicate a potential public health risk for consumers.
The Listeriamonocytogenes diversity throughout deboning, compressing and slicing of Spanish dry-cured ham processing among and within 6 production plants after cleaning and disinfection in two ...different seasons (autumn/winter and spring/summer) was evaluated in this work. L. monocytogenes isolates (n = 66), collected from deboning area (72.7%) and compressing and slicing areas (27.3%), were serotyped as 1/2b (65.1%), 1/2a (27.3%), 1/2c (6.1%) and 4b (1.5%) by PCR-based methods. The typing of the 66 isolates of L. monocytogenes by PFGE using the ApaI and SgsI enzymes revealed a high diversity with 52 pulsotypes and showed cross-contamination within each plant. The frequency of isolation of L. monocytogenes was higher in spring/summer than in autumn/winter. Although L. monocytogenes was not detected in any of the analyzed dry-cured ham samples, the presence of some pulsotypes and cross-contamination in the different industries suppose a hazard of contamination by this pathogen during deboning and slicing of dry-cured ham. The use of molecular typing techniques, such as PCR-based methods and PFGE characterization, could be used to trace the sources, distribution and routes of L. monocytogenes contamination throughout deboning and slicing of dry-cured ham.
•L. monocytogenes prevalence in dry-cured ham deboning and slicing areas was 9.16%.•Most of the L. monocytogenes in deboning and slicing areas were serotyped as 1/2b.•The frequency of L. monocytogenes was higher in spring/summer than in autumn/winter.•Cross-contamination between deboning, compressing and slicing areas was detected.
•Antioxidants improve the brightness of roasted shrimp after sterilization.•Antioxidants reduce the free radical content of roasted shrimp after sterilization.•Antioxidant-treated roasted shrimp have ...lower myofibrillar porosity.•Antioxidants reduce water loss in roasted shrimp after sterilization.•The degree of oxidation was negatively correlated with edible quality.
Sterilization is essential for ready-to-eat foods; however, it tends to degrade the quality of the product. To explore the role of antioxidants in regulating the edible quality of roasted Pacific white shrimp after sterilization, color changes, degree of oxidation, microstructure and quality of roasted shrimp treated with tea polyphenols, phytic acid, rosemary extract, and d-sodium erythorbate were investigated. Tea polyphenol-treated roasted shrimp had the lowest Maillard intermediate products and browning strength after sterilization; phytic acid significantly reduced carbonyl content and TBARS value; rosemary extract exhibited the lowest level of free radicals, while d-sodium erythorbate preserved a relatively intact myofibrillar structure. Correlation analysis revealed a negative correlation between the degree of oxidation and the edible quality of roasted shrimp after sterilization. Therefore, the addition of antioxidants inhibited oxidation and improved the quality of roasted shrimp, and different antioxidants had diverse effects on the quality improvement of roasted shrimp after thermal sterilization.
Farmyard manure and slurry (FYM&S) and anaerobic digestate are potentially valuable soil conditioners providing important nutrients for plant development and growth. However, these organic ...fertilisers may pose a microbial health risk to humans. A quantitative microbial risk assessment (QMRA) model was developed to investigate the potential human exposure to pathogens following the application of FYM&S and digestate to agricultural land. The farm-to-fork probabilistic model investigated the fate of microbial indicators (total coliforms and enterococci) and foodborne pathogens in the soil with potential contamination of ready-to-eat salads (RTEs) at the point of human consumption. The processes examined included pathogen inactivation during mesophilic anaerobic digestion (M-AD), post-AD pasteurisation, storage, dilution while spreading, decay in soil, post-harvest washing processes, and finally, the potential growth of the pathogen during refrigeration/storage at the retail level in the Irish context. The QMRA highlighted a very low annual probability of risk (Pannual) due to Clostridium perfringens, norovirus, and Salmonella Newport across all scenarios. Mycobacterium avium may result in a very high mean Pannual for the application of raw FYM&S, while Cryptosporidium parvum and pathogenic E. coli showed high Pannual, and Listeria monocytogenes displayed moderate Pannual for raw FYM&S application. The use of AD reduces this risk; however, pasteurisation reduces the Pannual to an even greater extent posing a very low risk. An overall sensitivity analysis revealed that mesophilic-AD's inactivation effect is the most sensitive parameter of the QMRA, followed by storage and the decay on the field (all negatively correlated to risk estimate). The information generated from this model can help to inform guidelines for policymakers on the maximum permissible indicator or pathogen contamination levels in the digestate. The QMRA can also provide the AD industry with a safety assessment of pathogenic organisms resulting from the digestion of FYM&S.
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•Residual pathogens may remain after mesophilic Anaerobic Digestion (AD).•Potential risk from ingestion of pathogens contaminating ready-to-eat salads is investigated.•There is a potential risk (infection/illness) of foodborne pathogens via ready-to-eat salads.•Mesophilic-AD's inactivation, storage, and decay on the field are the most sensitive parameters.•Post-AD pasteurisation was found to significantly help protect food safety.
Although rates of listeriosis are low in comparison to other foodborne pathogenic illness, listeriosis poses a significant risk to human health as the invasive form can have a mortality rate as high ...as 30%. Food processors, especially those who produce ready-to-eat (RTE) products, need to be vigilant against Listeria monocytogenes, the causative pathogen of listeriosis, and as such, the occurrence of L. monocytogenes in food and in the food processing environment needs to be carefully monitored. To examine the prevalence and patterns of contamination in food processing facilities in Ireland, 48 food processors submitted 8 samples every 2 months from March 2013 to March 2014 to be analyzed for L. monocytogenes. No positive samples were detected at 38% of the processing facilities tested. Isolates found at the remaining 62% of facilities were characterized by serotyping and Pulsed Field Gel Electrophoresis (PFGE). A general L. monocytogenes prevalence of 4.6% was seen in all samples analyzed with similar rates seen in food and environmental samples. Differences in prevalence were seen across different food processors, food sectors, sampling months etc. and PFGE analysis allowed for the examination of contamination patterns and for the identification of several persistent strains. Seven of the food processing facilities tested showed contamination with persistent strains and evidence of bacterial transfer from the processing environment to food (the same pulsotype found in both) was seen in four of the food processing facilities tested.
Infections by methicillin-resistant
(MRSA) are gradually increasing in the community. In this study, we investigated a total of 162 food samples including 112 ready-to-eat (RTE) foods and 40 ...processed raw meat and fish samples collected from retail vendors in Dhaka, Bangladesh and determined the occurrence of toxigenic
and MRSA. Around 22% of samples were positive for
, RTE foods being more positive (23%) than the processed raw meat/fish samples (18%). Among 35
isolates, 74% were resistant to erythromycin, 49% to ciprofloxacin and around 30% to oxacillin and cefoxitin. Around 37% of isolates were resistant to ≥3 classes of antibiotics and 26% of isolates (
= 9) were identified as MRSA. Majority of the isolates were positive for enterotoxin genes (74%), followed by
gene (71%), toxic shock syndrome toxin (
) gene (17%) and exfoliative toxin genes (11%). Multi locus sequence typing (MLST) of 9 MRSA isolates identified four different types such as ST80 (
= 3), ST6 (
= 2), ST239 (
= 2) and ST361 (
= 2).
typing of MRSA isolates revealed seven different types including t1198 (
= 2), t315 (
= 2), t037 (
= 1), t275 (
= 1), t304 (
= 1), t8731 (
= 1) and t10546 (
= 1). To our knowledge, this is the first report entailing baseline data on the occurrence of MRSA in RTE foods in Dhaka highlighting a potential public health risk to street food consumers.
The presence of multi-drug resistant (MDR) bacteria in ready-to-eat foods comprises a threat for public health due to their ability to acquire and transfer antibiotic-resistant determinants that ...could settle in the microbiome of the human digestive tract. In this study,
Enterococcus faecium
UC7251 isolated from a fermented dry sausage was characterized phenotypically and genotypically to hold resistance to multiple antibiotics including aminoglycosides, macrolides, β-lactams, and tetracyclines. We further investigated this strain following a hybrid sequencing and assembly approach (short and long reads) and determined the presence of various mobile genetic elements (MGEs) responsible of horizontal gene transfer (HGT). On the chromosome of UC7251, we found one integrative and conjugative element (ICE) and a conjugative transposon Tn
916
-carrying tetracycline resistance. UC7251 carries two plasmids: one small plasmid harboring a rolling circle replication and one MDR megaplasmid. The latter was identified as mobilizable and containing a putative integrative and conjugative element-like region, prophage sequences, insertion sequences, heavy-metal resistance genes, and several antimicrobial resistance (AMR) genes, confirming the phenotypic resistance characteristics. The transmissibility potential of AMR markers was observed through mating experiments, where Tn
916
-carried tetracycline resistance was transferred at intra- and inter-species levels. This work highlights the significance of constant monitoring of products of animal origin, especially RTE foodstuffs, to stimulate the development of novel strategies in the race for constraining the spread of antibiotic resistance.
Staphylococcus aureus, particularly methicillin-resistant S.aureus (MRSA), is a life-threatening pathogen in humans, and its presence in food is a public health concern. MRSA has been identified in ...foods in China, but little information is available regarding MRSA in ready-to-eat (RTE) foods. We aimed to investigate the prevalence of S. aureus and MRSA in Chinese retail RTE foods. All isolated S. aureus were tested for antimicrobial susceptibility, and MRSA isolates were further characterized by multilocus sequence typing (MLST) and staphylococcal cassette chromosome mec (SCCmec) typing. Of the 550 RTE foods collected from 2011 to 2014, 69 (12.5%) were positive for S. aureus. Contamination levels were mostly in the range of 0.3-10 most probable number (MPN)/g, with five samples exceeding 10 MPN/g. Of the 69 S. aureus isolates, seven were identified as MRSA by cefoxitin disc diffusion test. Six isolates were mecA-positive, while no mecC-positive isolates were identified. In total, 75.8% (47/62) of the methicillin-susceptible S. aureus isolates and all of the MRSA isolates were resistant to three or more antibiotics. Amongst the MRSA isolates, four were identified as community-acquired strains (ST59-MRSA-IVa (n = 2), ST338-MRSA-V, ST1-MRSA-V), while one was a livestock-associated strain (ST9, harboring an unreported SCCmec type 2C2). One novel sequence type was identified (ST3239), the SCCmec gene of which could not be typed. Overall, our findings showed that Chinese retail RTE foods are likely vehicles for transmission of multidrug-resistant S. aureus and MRSA lineages. This is a serious public health risk and highlights the need to implement good hygiene practices.
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