Through-package fat determination in commercial samples of mayonnaise and salad dressing using time-domain nuclear magnetic resonance spectroscopy and chemometrics

Although fat is an essential component in the human diet, the consumption of food with high fat content has been the major cause of obesity. Here we are demonstrating that time-domain nuclear magnetic resonance (TD-NMR) decays, obtained by Carr–Purcell–Meiboom–Gill (CPMG) pulse sequence, can be used to predict the total fat content in sealed packages of commercial food emulsions, such as mayonnaise and salad dressing that may contain more than 50% of fat. The PLS model of the CPMG decays shows high linear correlation (>0.9) and low root mean square errors (RMSE) for cross-validation and validation data. Therefore, this procedure can be used to predict the total fat content in food emulsion after packaging, to detect problems in the manufacturing process or fraud. In addition, the TD-NMR instrument and the proposed methods can also be adapted for using at the end of the food chain (store) to measure the fat content in consumer packaged goods.     

Antimicrobial action and effects on beef quality attributes of a gaseous ozone treatment at refrigeration temperatures

The effects of gaseous ozone treatment at refrigeration temperatures, on microbial counts (total aerobic mesophilic heterotrophic microorganisms and inoculated Escherichia coli) in culture media and in beef samples were analyzed. The influence of ozone on beef quality properties such as surface color and rancidity was measured.The effect of gaseous ozone (154 × 10^?6 kg m^?3) in culture media inoculated with E. coli after 3- or 24-h treatment at 0° and 4 °C caused a total inactivation of this microorganism.For beef samples treated with the same gaseous ozone concentration, the highest microbial inhibition was observed at 0 °C and after 24-h exposure, producing a decrease of 0.7 and 2.0 log₁₀ cycles in E. coli and total aerobic mesophilic heterotrophic microorganism counts respectively; however, both the surface color and lipid oxidation of these beef samples were unacceptable. Shorter exposure times (3 h) to the tested ozone concentration at both temperatures (0–4 °C), reduced 0.5 log₁₀ cycles the counts of total aerobic mesophilic heterotrophic microorganisms and 0.6–1.0 log₁₀ cycles the counts of E. coli, without changing the color or producing rancidity in beef.     

Detection of verocytotoxin-producing Escherichia coli (VTEC) in minced beef and raw milk by colony blot hybridization

Verocytotoxin-producing Escherichia coli (VTEC) are foodborne pathogens that cause outbreaks linked to consumption of meat and raw milk. In this note the authors report results obtained from a survey conducted on minced beef and raw bovine milk samples using a Multiplex PCR (M-PCR) for the detection of eae, stx₁, stx₂ and hlyA genes as a screening step followed by a colony blot hybridization (CBH) technique for the isolation of the VTEC. Of 100 minced beef and 123 raw milk samples, 13 (13%) and 7 (5.7%) were positive in the M-PCR and among these 9 and 3 strains were isolated using CBH, respectively. All isolates showed the presence of the stx₂ gene, single or in association with the other investigated genes. None of the isolates belonged to the O157, O26, O91, O103, O111 and O145 serogroups. The study showed that the use of M-PCR for the screening of samples coupled with a sensitive and specific detection technique, could improve the possibility of detection of VTEC strains in foods. Moreover, the presence of VTEC in minced beef and in raw milk confirms their important role as putative vehicles of infection to humans. Stringent control of these foodstuffs is essential for food safety purposes.     

Development of a controlling method for Escherichia coli O157:H7 and Salmonella spp. in fresh market beef by using polylysine and modified atmosphere packaging

Escherichia coli O157:H7 and Salmonella spp. often contaminate fresh beef. In Japan, an E coli outbreak caused by raw beef made 181 people ill and 5 individuals dead in 2011. Responding to this outbreak, an effective sterilization method for fresh beef is expected to be developed. In this study, ε-polylysine combined with CO₂-packaging method was examined for controlling these pathogens in fresh beef. At an incubation temperature of 4 °C, approximately 4.3 log and 2.4 log reduction in bacterial numbers were observed after 7-day incubation for E. coli O157:H7 and Salmonella, respectively, in ε-polylysine-added beef. When effectiveness of CO₂-packaging combined with ε-polylysine was investigated, CO₂ did not have additional inhibiting effect on bacterial growth compared to only-ε-polylysine-treated samples when incubated at 4 °C. However, effectiveness of CO₂ was observed when incubated at 10 °C where approximately 2.9 log and 4.4 log reduction in E. coli cell numbers were observed in only-ε-polylysine-treated samples and polylysine- and CO₂-treated group, respectively, and approximately 1.7 log and 3.5 log reduction in Salmonella cell numbers were observed in only-ε-polylysine-treated samples and polylysine and CO₂-treated group, respectively. This study confirmed that ε-polylysine or ε-polylysine combined with CO₂ packaging are effective in preventing foodborne diseases caused by raw beef.     

A comparison of Raman and FT-IR spectroscopy for the prediction of meat spoilage

In this study, time series spectroscopic, microbiological and sensory analysis data were obtained from minced beef samples stored under different packaging conditions (aerobic and modified atmosphere packaging) at 5 °C. These data were analyzed using machine learning and evolutionary computing methods, including partial least square regression (PLS-R), genetic programming (GP), genetic algorithm (GA), artificial neural networks (ANNs) and support vector machines regression (SVR) including different kernel functions [i.e. linear (SVR_L), polynomial (SVR_P), radial basis (RBF) (SVR_R) and sigmoid functions (SVR_S)]. Models predictive of the microbiological load and sensory assessment were calculated using these methods and the relative performance compared. In general, it was observed that for both FT-IR and Raman calibration models, better predictions were obtained for TVC, LAB and Enterobacteriaceae, whilst the FT-IR models performed in general slightly better in predicting the microbial counts compared to the Raman models. Additionally, regarding the predictions of the microbial counts the multivariate methods (SVM, PLS) that had similar performances gave better predictions compared to the evolutionary ones (GA-GP, GA-ANN, GP). On the other hand, the GA-GP model performed better from the others in predicting the sensory scores using the FT-IR data, whilst the GA-ANN model performed better in predicting the sensory scores using the Raman data. The results of this study demonstrate for the first time that Raman spectroscopy as well as FT-IR spectroscopy can be used reliably and accurately for the rapid assessment of meat spoilage.     

Relaxation models for analyzing NMR T2 spectra of O/W and W/O/W emulsions

Abstract

This study aimed at comprehending the transversal relaxation time(T₂) spectra and relaxation mechanism for O/W and W/O/W emulsions in NMR CPMG experiment. The T₂ relaxation model for O/W and W/O/W emulsions was established respectively. T₂ spectra of O/W emulsions with different water content and W/O/W emulsions with settling time in demulsification were analyzed based the relaxation models. The results show that the T₂ spectra characteristics of emulsions in NMR CPMG experiment are consistent with the prediction of relaxation models, which indicated that relaxation models were practical and contribute to the analysis of T₂ spectra for emulsions. Those study laid a foundation for analyzing the characters of single or double emulsions basing T₂ spectra.     

Detection of Escherichia coli O157:H7 in ground beef using immunomagnetic separation and multiplex PCR

In the study 251 fresh ground beef samples sold in Ankara were analyzed to evaluate the prevalence of Escherichia coli O157:H7 by immunomagnetic separation (IMS) based cultivation technique. Virulence factors of the isolates were determined by multiplex PCR. Nineteen (7.6%) of 251 ground beef samples were found as contaminated with E. coli O157. By PCR analyse in two of the isolates fliC_h7 gene was detected and identified as E. coli O157:H7. According to the multiplex PCR one of the isolate has all stx₁, stx₂, eaeA, hly and fliC_h7 genes and the other has stx₁, eaeA, hly and fliC_h7 genes.     

Incidence of Listeria monocytogenes in beef,pork, raw-dried and raw-smoked sausages in Bulgaria

For a 5-years period (2002–2007) 786 samples (505 samples of beef, pork, minced beef, minced pork and 281 samples of raw-dry and raw-smoked sausages) were analyzed. From beef and pork 39 strains Listeria monocytogenes (7.7%), three strains Listeria ivanovii (0.6%), 23 strains Listeria innocua (4.6%) and four strains Listeria welshimeri (0.8%) were obtained. L. monocytogenes were isolated in 28 samples (10.0%), L. ivanovii, L. innocua and L. welshimeri – in 0.7%, 4.3% and 0.7%, respectively, from investigated raw-dried and raw-smoked sausages.     

Effects of gamma irradiation on trans fatty acid composition in ground beef

The present study was conducted to evaluate the combined effects of irradiation (0, 1, 3, 5 and 7 kGy) of ground beef on fatty and trans fatty acids. Irradiation of ground beef was performed by gamma rays from a ⁶⁰Co source. Irradiated ground beef samples had higher concentrations of total trans fatty acids than the control samples. Irradiated ground beef samples with 7 kGy had the highest total trans fatty acids, total monounsaturated and total unsaturated fatty acids than the other samples. In this study results showed an increase in trans fatty acids related to the increase on irradiation dose in ground beef and irradiation dose changed fatty acids composition especially trans fatty acids in ground beef.     

Mathematical modeling and growth kinetics of Clostridium sporogenes in cooked beef

Clostridium sporogenes PA 3679 is a common surrogate for proteolytic Clostridium botulinum for thermal process development and validation. However, little information is available concerning the growth kinetics of C. sporogenes in food. Therefore, the objective of this study was to investigate the growth kinetics of C. sporogenes in cooked beef under different temperature conditions.Ground beef samples, inoculated with C. sporogenes spores, were incubated at temperatures between 8 and 47 °C to examine the growth of this microorganism. Two primary models (Huang and Baranyi models) were used to analyze the growth data. The Ratkowsky square-root model was used as the secondary model to evaluate the effect of temperature on bacterial growth rate and lag time. The USDA IPMP 2013, a free data analysis tool for predictive microbiology, was used in data analysis.No growth of C. sporogenes was observed at temperatures below 15 °C for up to 25 days. At temperatures between 20 and 47 °C, C. sporogenes grew in cooked beef. The growth curves could be analyzed by both Huang and Baranyi models. The root mean squared error (RMSE) was 0.375 for the Huang model, and 0.441 for the Baranyi model with a global h₀ of 10.46. The nominal minimum growth temperature (T₀) estimated from the Huang model was 15.5 °C, which was 12.7 °C for the Baranyi model. The maximum growth temperature was 48.0 and 48.3 °C for the Baranyi and Huang models, respectively. The lag times and specific growth rates of C. sporogenes observed in this study were reasonably close to the data reported in the literature for C. botulinum under comparable conditions, suggesting that C. sporogenes may be used as a potential surrogate for evaluating the growth of C. botulinum in cooked meats during cooling. However, a direct comparison of growth kinetics between the two microorganisms is needed to confirm the suitability of C. sporogenes as a surrogate of C. botulinum.     

Preventive effect of tannic acid in combination with modified atmospheric packaging on the quality losses of the refrigerated ground beef

Chemical, microbiological and sensorial changes of ground beef treated without and with tannic acid (200 mg/kg) and stored in air and under modified atmosphere packaging (MAP) (80%O₂/20%CO₂ or 10%O₂/20%CO₂/70%N₂) were monitored during 15 days of storage at 4 °C. During the storage, samples treated with tannic acid and kept under all packaging conditions contained lower peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS) with coincidental lower non-haem iron content, compared with non-treated counterparts (P < 0.05). The sample packed in high oxygen MAP treated without and with tannic acid had the higher oxymyoglobin and a^* values and received the higher likeness scores for colour, whereas the samples stored in air and under low oxygen MAP showed the lower values, regardless of tannic acid treatment. After 15 days of storage, myosin heavy chain (MHC) and actin of all tannic acid treated samples underwent less degradation than those without tannic acid treatment for all packaging conditions. Degradation of MHC was more pronounced in samples kept under MAP with high oxygen. Psychrophilic bacterial count (PBC) of all tannic acid treated samples was lower, compared with that of non-treated samples (P < 0.05), irrespective of packaging condition. Therefore, tannic acid treated samples stored under high oxygen MAP could maintain the red colour and retard lipid oxidation and microbial growth of ground beef during refrigerated storage.     

Effects of mild and pasteurizing heat treatments on survival of generic and verotoxigenic Escherichia coli from beef enrichment cultures

At many North American beef packing plants, hot water washes and pasteurizing treatments are used to clean and decontaminate carcasses. The aim of this study was to determine whether reduction in numbers of total Escherichia coli found on beef could be regarded as indicative of the reduction in numbers of verotoxigenic E. coli (VTEC) resulting from the same heat treatment. Swab samples were collected from hide-on beef carcasses and were enriched for E. coli in E. coli broth supplemented with novobiocin. Suspensions containing cells in the stationary phase were mixed with equal volumes of meat juice medium and the mixtures were not heated or were heated at temperatures between 55 and 70 °C. All preparations were treated with deoxycholate and propidium monoazide (PMA), then DNA was extracted. Real-time PCR was performed using primers targeting the uidA gene for total E. coli, the stx₁ and stx₂ genes for VTEC, and the eae gene for O157. For samples that were not subjected to heat treatment, cycle threshold (Ct) values were from 13.53 to 17.93 for uidA, 17.94 to 26.77 for stx₁, 21.57 to 29.36 for stx₂, and 23.53 to 28.31 for eae. Ct values for all genes were higher for heat treated than for not treated portions of samples. Differences between Ct values for not treated and heat treated portions of each sample were 5.06–7.57 for uidA, 4.35 to 7.03 for stx₁, 4.49 to 7.12 for stx₂ and 4.75 to 6.77 for eae. Differences between the increases of Ct values for pairs of genes in the sample were 0.32–0.83 for uidA and stx₁, 0.19–0.57 for uidA and stx₂ and 0.31–0.80 for uidA and eae. The maximum change in the ratio of Ct values for uidA and stx₁, stx₂ or eae as a result of heating corresponded to a change of 0.3 log units, which is less than the 0.5 log units generally considered to be microbiologically significant. Therefore, the findings indicate that reductions as a result of mild or pasteurizing heat treatments of total E. coli populations derived from beef can be regarded as indicative of the reductions in sub-populations of O157-VTEC and total VTEC resulting from the treatments.     

Occurrence of aflatoxin M1 in white cheese samples from Tehran, Iran

This study was undertaken to determine the occurrence of aflatoxin M₁ (AFM₁) in 50 white cheese samples from 2 dairy factories in summer 2008 and winter 2009. Enzyme-linked immunosorbent assay (ELISA) method was used for analysis of the samples. Aflatoxin M₁ was found in 60% of the cheese samples, ranging from 40.9 to 374 ng/kg. Toxin levels in 6% of the samples exceeded the Iranian national standard limit i.e. 200 ng/kg. Considering seasonal variability, mean concentration of AFM₁ in the samples collected in winter was significantly (P < 0.03) higher than those collected in summer. Therefore, high occurrence of AFM₁ in cheese samples could be a potential hazard for public health.     

Prevalence,molecular identification and antimicrobial resistance profile of Salmonella serovars isolated from retail beef products in Mansoura,Egypt

The present study was undertaken to determine the prevalence of Salmonella in 270 raw meat samples (90 each of fresh beef, ground beef, and beef burger) purchased on nine occasions from various supermarkets and butchers' shops in Mansoura city, Egypt. Using conventional biochemical identification, Salmonella species were recovered from 23.3% (21/90), 20% (18/90), and 12.2% (11/90) of fresh beef, ground beef and beef burger samples, respectively with an overall prevalence of 18.5% (50/270) among all the meat products examined. Higher prevalence were obtained based on molecular identification, by detecting gyrB and invA genes, which verified the presence of Salmonella species in 30.0% (27/90), 26.7% (24/90), and 16.7% (15/90) of fresh beef, ground beef, and beef burger samples, respectively with an overall prevalence of 24.4% (66/270) among all the meat products tested. Of the 2635 presumptive colonies tested, 228 were biochemically identified as Salmonella, while 272 were molecularly identified as Salmonella, which were all positive for the enterotoxin (stn) virulent gene. Of the 272 serologically tested strains, 266 were serologically identified into six Salmonella serovars, while 6 strains were untypable. Salmonella Typhimurium and Salmonella Enteritidis were the most prevalent serovars with an incidence of 38.2% (104/272) and 34.6% (94/272), respectively. The other four serovars identified were Salmonella Haifa, Salmonella Muenster, Salmonella Virchow, and Salmonella Anatum were detected at lower prevalences of 11% (30/272), 7.4% (20/272), 4% (11/272) and 2.6% (7/272), respectively. Interestingly, the antimicrobial susceptibility testing indicated that all of the 100 Salmonella serovars tested were multidrug resistant (resistant to three or more antibiotics). Our findings demonstrated that the retail beef products tested were widely contaminated with multidrug-resistant Salmonella and such contamination may constitute a major public health concern.     

Stable isotope ratio and elemental composition parameters in combination with discriminant analysis classification model to assign country of origin to commercial vegetables – A preliminary study

Recently, increased public attention has been paid to the geographical authentication of food, including vegetables, which are considered to be one of the major health-promoting components in a balanced diet. The purpose of the present study was to investigate the suitability of the use of isotopic compositions of light elements (δ¹³C, δ¹⁵N, δ¹⁸O, δ³⁴S) in combination with multi-elemental fingerprinting (P, S, Cl, K, Ca, Mn, Fe, Zn, Br, Rb, Sr) to provide rapid, robust and inexpensive screening methods for distinguishing lettuce, sweet pepper, and tomato samples according to their given country of origin (i.e., Slovenia, Austria, Spain, Morocco, Italy, Greece), and thus ensuring their traceability in terms of their authenticity. The classification efficiency of the proposed multivariate statistical models using supervised pattern-recognition analysis, namely multivariate discriminant analysis, was sufficient for rapid and robust screening purpose. The predictions of the suggested discriminant analysis models per kind using cross-validation leave-one-out were 86.2%, 71.1% and 74.4% for lettuce, sweet pepper and tomato, respectively. The first use of the proposed methodology on vegetable samples on European and Mediterranean scales provides a valuable and necessary contribution to the development and implementation of a new national surveillance system that can be used to trace the geographical origins of vegetables.     

Occurrence and factors associated with the presence of aflatoxin M1 in breast milk samples of nursing mothers in central Mexico

Aflatoxin M₁ (AFM₁) is the main mycotoxin frequently found in milk and dairy products. Exposure of infants to AFM₁ is of great health public concern because of its toxic and carcinogenic properties. The aim of this study was to determine the occurrence, levels and factors associated with the presence of aflatoxin M₁ in breast milk samples of nursing mothers in central Mexico. A total of 112 samples were collected and analyzed by a competitive-ELISA assay during January–August 2014. A Semi-Quantitative Food Frequency Questionnaire was used to determine weekly intake of food groups. Results showed that 89% of breast milk samples contained AFM₁ in a range of 3.01–34.24 ng/L. AFM₁ mean level was significantly higher (P < 0.05) in winter (12.78 ng/L) and spring (12.09 ng/L) than summer (7.91 ng/L). It was also detected that 7% of samples exceeded the European Community regulation (25 ng/L) for milk infant formula. The presence of aflatoxin M₁ was significantly associated (P < 0.05) to consumption of egg, cola drink and sunflower oil. The high occurrence and noticeable levels of AFM₁ detected, as well as the mean AFM₁ estimated daily intake (2.35 ng/kg b.w./day) suggested, for the first time, that breast-fed infants in the central region of Mexico, may be exposed to significant levels of this toxin through mother's breast milk.     

Conducting inferential statistics for low microbial counts in foods using the Poisson-gamma regression

Mixed Poisson distributions have been shown to be able to represent low microbial counts more efficiently than the lognormal distribution because of its greater flexibility to model microbial clustering even when data consist of a large proportion of zero counts. The objective of this study was to develop an alternative modelling framework for low microbial counts based on heterogeneous Poisson regressions. As an illustration, Poisson-gamma regression models were used to assess the effect of chilling on the concentration of total coliforms from beef carcasses (n = 600) sampled at eight large Irish abattoirs. Three Poisson-gamma and three zero-modified (hurdle and zero-inflated) models were appraised with a series of random-effects variants in order to extract any variability in microbial mean concentration, dispersion and/or proportion of zero counts. Models were compared and validated in their ability to predict the coliforms counts on carcasses after chilling. In all five test batches, the hurdle Poisson-gamma distributions predicted the observed post-chill counts closer than the Poisson-gamma distributions. This is justified by the better capacity of the hurdle model to represent a higher proportion of zero counts, which were in fact observed in the post-chill batches. Thus, with a coded variable (pre-chill/post-chill) as treatment, and extracting the significant variability of batches nested in abattoirs for the coliforms mean concentration (σ²_u = 2.68), the dispersion measure (σ²_v = 2.39) and the probability of zero counts (σ²_w = 0.89), the validated hurdle Poisson-gamma model confirmed that chilling has a decreasing effect on the viability of coliforms from beef carcasses, and that the concentration is reduced by an average (pre-chill to post-chill) factor of 2.2 (95% CI: 2.15–2.24) at batch level. The model also indicated that chilling increases the odds of producing a zero count from a carcass swab in about 13.5 times, and that the higher the coliforms concentration in a batch, the weaker the effect that chilling has to reduce such contamination on the beef carcasses.     

A study on the occurrence of aflatoxin M1 in Iranian Feta cheese

This study was undertaken to determine the presence and levels of aflatoxin M₁ (AFM₁) in cheeses produced by different plants in the province of Tehran. For this purpose, a total of 80 cheese samples analyzed, and thin layer chromatography (TLC) was used to determine the presence and levels of AFM₁.AFM₁ was found in 82.5% of 80 of the cheese samples examined. The range of contamination levels varied among different months. AFM₁ in May, August, November, February samples ranged from 0.17 to 1.30, 0.15 to 2.41, 0.16 to 1.11, and 0.19 to 2.05 μg/kg, respectively, while the mean values were 0.41, 0.35, 0.36, and 0.52 μg/kg, respectively.The highest mean concentration of aflatoxin M₁ (AFM₁) was registered in February samples (0.52 μg/kg). The lowest mean concentration of aflatoxin M₁ was registered in August samples (0.35 μg/kg).Statistical evaluation showed that there were not significant differences (P > 0.05) between the concentrations of AFM₁ of cheese samples taken in May and August with November and February. In other words, AFM₁ contents of cheese samples taken in November and August were not lower than cheese samples taken in May and February. Almost 60.6% of the contaminated samples exceeded the maximum acceptable levels (0.25 μg/kg) that accepted by some of the countries such as Turkey.It was therefore concluded that, high occurrence of AFM₁ in cheese samples were considered to be possible hazards for human health.     

Seasonal study of aflatoxin M1 contamination in milk of four dairy species in Yazd,Iran

This survey was conducted to determine the occurrence of aflatoxin M₁ (AFM₁) in samples of raw milk obtained from cow, sheep, goat, and camel herds in Yazd province during different seasons. Aflatoxin M₁ was analyzed using the competitive enzyme-linked immunosorbent assay technique for screening and high-performance liquid chromatography with fluorescence detection for confirmatory purposes. The detection rates of AFM₁ in cow, sheep, goat, and camel milk samples were 46.5%, 21.6%, 20.1%, and 4.03%, respectively. Levels of the toxin in 15.4% of cow milk, 11.5% of sheep milk, and 9.15% of goat milk samples exceeded the legal limit (0.050 μg/kg) recommended by the Institute of Standards and Industrial Research of Iran; while none of the camel milk samples exceeded the legal limit. The occurrence and levels of AFM₁ in cow milk samples from industrial dairy farms was significantly lower (P ≤ 0.05) than those from traditional ones. Seasonal variations influenced the occurrence and levels of AFM₁ in cow, sheep, and goat milk; however, no statistically significant seasonal effect was found for camel milk. This study indicates a high occurrence of AFM₁ in cow milk especially those obtained from traditional dairy farms. Therefore, more supervision is required on these farms; and traditional dairy farms should be gradually replaced by industrial ones.     

Prevalence and characterization of Escherichia coli O157:H7 from samples along the production line in Chinese beef-processing plants

This work investigated the prevalence of Escherichia coli O157:H7 and the antibiotic susceptibility, genetic diversity and virulence genes of isolated strains from four beef slaughter plants in China. A total of 510 samples (feces, hide, carcasses and raw meat) were tested for E. coli O157:H7 using enrichment, immunomagnetic separation, and plating on selective media. The prevalence of E. coli O157:H7 in the feces, hide, pre-evisceration carcass, post-evisceration carcass, post-washing carcass, chilled carcass, and raw meat samples was 1.43%, 1.43%, 0%, 0%, 0%, 1.25%, and 0%, respectively. Multiplex PCR assays were used for serotype confirmation and virulence gene detection. stx₂, eaeA and EHEC-hlyA genes were present in all six of the strains, and the stx₁ gene was not present. Fluorescence amplified fragment length polymorphism (FAFLP) was used to determine the genetic diversity of E. coli O157:H7 and revealed a high similarity between the strains isolated from feces and those isolated from carcasses. None of the isolated strains were found to be resistant to sixteen commonly used antimicrobial agents. The results of this study indicate that although E. coli O157:H7 contamination in the Chinese beef industry is sporadic and not as common as reported in other counties, all of the isolates contained three major virulence genes, presenting a high risk of disease for humans. The current research provides baseline information on E. coli O157:H7 prevalence and character profiles in Chinese beef-processing plants that can be used for future studies.