Survival of Listeria monocytogenes and Escherichia coli O157:H7 during sauerkraut fermentation

Sauerkraut was produced from shredded cabbage, as is typical in the United States, and from whole head cabbages, which is a traditional process in parts of Eastern Europe. The sauerkraut was inoculated with five strain mixtures of Escherichia coli O157:H7 and Listeria monocytogenes, and the populations of these bacteria, as well as lactic acid bacteria, pH, and titratable acidity, were monitored over the course of fermentation. Fermentation variables were temperature (18 and 22 degrees C) and salt concentration (1.8, 2.25, and 3%). For most of the analyses, the type of cabbage processing was a significant factor, although within cabbage type, neither salt nor fermentation temperature had significant effects. The final pH of the whole-head sauerkraut was lower than the shredded sauerkraut, but the titratable acidity was significantly higher in the shredded sauerkraut. E. coli O157:H7 and L. monocytogenes persisted in the brines for most of the fermentation, although at the end of the fermentations (15 days for shredded, 28 days for whole head), neither pathogen had detectable populations. E. coli populations decreased more rapidly in the shredded sauerkraut even though the pH was higher because of the higher total acidity in the shredded sauerkraut. Acid-tolerant strains of E. coli and L. monocytogenes were isolated from both shredded and whole-head sauerkraut at different salt concentrations and temperatures after 15 days of fermentation and could be detected at 35 days in the wholehead sauerkraut.     

Elimination of Escherichia coli O 157 : H7 and Listeria monocytogenes from raw beef sausage by gamma-irradiation

The effectiveness of low gamma-irradiation doses in the destruction of Escherichia coli O 157 : H7 and Listeria monocytogenes in raw beef sausages was investigated. Raw samples of fresh manufactured beef sausage were subjected to gamma-irradiation at doses of 0, 1, 2, and 3 kGy. Then samples were cold-stored (4 +/- 1 degrees C) for 12 days and the effects of irradiation and storage on the counts of these harmful bacteria were studied. Moreover, the effects of irradiation and storage on the percentages of free fatty acids (FFAs) in lipids, on the p-anisidine values of lipids, solubility of sarcoplasmic and myofibrilar proteins, and water-holding capacity (WHC) were also determined. The results showed that gamma-irradiation at 1 and 2 kGy significantly reduced the counts of E. coli O 157 : H7 and L. monocytogenes, while 3 kGy dose effectively eliminated these bacteria by more than 4 log and 3 log units, respectively, and could keep their counts below the detection level during storage. Gamma-irradiation had no significant effects on the percentages of FFAs in lipids, solubility of sarcoplasmic and myofibrilar proteins, and WHC of samples, while it significantly increased the p-anisidine value of lipids. During storage, significant increases in the percentages of FFAs and p-anisidine values were observed for lipids of irradiated and nonirradiated sausages, while the solubility of sarcoplasmic and myofibrilar proteins showed no significant changes. Moreover, samples of irradiated and nonirradiated sausages showed significant decreases in their WHC during the first 6 days of storage at 4 +/- 1 degrees C, then showed no significant changes. Finally, gamma-irradiation at a dose of 3 kGy appeared to be sufficient to improve the microbiological safety of raw beef sausages without adverse effects on their chemical properties.     

Survival of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella in juice concentrates

The survival of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella was studied in apple, orange, pineapple, and white grape juice concentrates and banana puree. Pouches of juice concentrate or puree were inoculated with pathogens at a level > or = 10(3) CFU/g and stored at -23 degrees C (-10 degrees F). Pathogen survival was monitored at 6 and 24 h, once a week for four consecutive weeks, and biweekly thereafter until 12 weeks. When pathogens were not detectable by direct plating, samples were enriched in universal preenrichment broth for 72 h and plated on selective media. Results showed that E. coli O157:H7, L. monocytogenes, and Salmonella were recoverable from all five concentrates through 12 weeks of storage at -23 degrees C.     

Survival of Escherichia coli O157:H7 in dry sausage fermented by probiotic lactic acid bacteria

Probiotic Lactobacillus rhamnosus GG, L rhamnosus E‐97800, L rhamnosus LC‐705 and commercial Pediococcus pentosaceus were studied for their ability to inhibit the growth of Escherichia coli O157:H7 in dry sausage. The strains were able to produce technologically high‐quality dry sausage. The number of E coli O157:H7 decreased from approximately 5 to approximately 2 log cfu g⁻¹ It was concluded that the above‐mentioned strains and the commercial culture were equally effective in inhibiting E coli O157:H7. © 2000 Society of Chemical Industry     

Effects on Escherichia coli O157:H7 and meat starter cultures of bovine lactoferrin in broth and microencapsulated lactoferrin in dry sausage batters

The effects of lactoferrin (LF) alone or with various chelating agents on the growth of 5 strains of Escherichia coli O157:H7 and 7 meat starter cultures were evaluated. E.coli O157:H7 and starter cultures were grown at 13 or 26 degrees C in Lauria (LB) or All Purpose Tween (APT) broths, respectively, with both broths being supplemented with 2.9% NaCl. LF alone prevented the growth of E. coli O157:H7 strains 0627 and 0628 but other strains grew. The antimicrobial effectiveness of LF was enhanced by EDTA but LF alone did not affect the growth of meat starter cultures in broth. However, when LF plus EDTA and sodium bicarbonate (SB) were used the growth of all meat starter cultures except Lactobacillus curvatus was reduced. During dry sausage manufacture with L. curvatus and Staphylococcus carnosus starter cultures the effects of LF, unencapsulated or microencapsulated in paste-like and dried powder forms, in sausage batters with or without EDTA and SB, on the viability of E. coli O157:H7 were examined. The reduction of E. coli O157:H7 during sausage manufacture was significantly enhanced (p<0.05) by all LF treatments. The largest reduction (4.2 log units) was obtained with unencapsulated LF. However, some of the apparent reduction in E.coli O157:H7 numbers with all treatments was due to cell injury rather than lethality, since significantly greater numbers were recovered on APT agar overlaid with the selective medium cefixime-tellurite Sorbitol McConkey agar (ct-SMAC) than on ct-SMAC alone. The narrow spectrum of LF activity and induction of injury rather than inactivation of E. coli O157:H7 limit the effectiveness of this agent against the pathogen in fermented meats.     

Survival and growth of Listeria monocytogenes and enterohemorrhagic Escherichia coli O157:H7 in minimally processed artichokes

The ability of Listeria monocytogenes and Escherichia coli O157:H7 inoculated by immersion (at 4.6 and 5.5 log CFU/ g, respectively) to survive on artichokes during various stages of preparation was determined. Peeling, cutting, and disinfecting operations (immersion in 50 ppm of a free chlorine solution at 4 degrees C for 5 min) reduced populations of L. monocytogenes and E. coli O157:H7 by only 1.6 and 0.8 log units, respectively. An organic acid rinse (0.02% citric acid and 0.2% ascorbic acid) was more effective than a tap water rinse in removing these pathogens. Given the possibility of both pathogens being present on artichokes at the packaging stage, their behavior during the storage of minimally processed artichokes was investigated. For this purpose, batches of artichokes inoculated with L. monocytogenes or E. coli O157:H7 (at 5.5 and 5.2 log CFU/g, respectively) were packaged in P-Plus film bags and stored at 4 degrees C for 16 days. During this period, the equilibrium atmosphere composition and natural background microflora (mesophiles, psychrotrophs, anaerobes, and fecal coliforms) were also analyzed. For the two studied pathogens, the inoculum did not have any effect on the final atmospheric composition (10% O2, 13% CO2) or on the survival of the natural background microflora of the artichokes. L. monocytogenes was able to survive during the entire storage period in the inoculated batches, while the E. coli O157:H7 level increased by 1.5 log units in the inoculated batch during the storage period. The modified atmosphere was unable to control the behavior of either pathogen.     

Survival of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes on inoculated walnut kernels during storage

The survival of single strains or cocktails of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes was evaluated on walnut kernels. Kernels were separately inoculated with an aqueous preparation of the pathogens at 3 to 10 log CFU/g, dried for 7 days, and then stored at 23°C for 3 weeks to more than 1 year. A rapid decrease of 1 to greater than 4 log CFU/g was observed as the inoculum dried. In some cases, the time of storage at 23°C did not influence bacterial levels, and in other cases the calculated rates of decline for Salmonella (0.05 to 0.35 log CFU/g per month) and E. coli O157:H7 (0.21 to 0.86 log CFU/g per month) overlapped and were both lower than the range of calculated declines for L. monocytogenes (1.1 to 1.3 log CFU/g per month). In a separate study, kernels were inoculated with Salmonella Enteritidis PT 30 at 4.2 log CFU/g, dried (final level, 1.9 log CFU/g), and stored at -20, 4, and 23°C for 1 year. Salmonella Enteritidis PT 30 declined at a rate of 0.10 log CFU/g per month at 23°C; storage time did not significantly affect levels on kernels stored at -20 or 4°C. These results indicate the long-term viability of Salmonella, E. coli O157:H7, and L. monocytogenes on walnut kernels and support inclusion of these organisms in hazard assessments.     

Predicting survival of Escherichia coli O157:H7 in dry fermented sausage using artificial neural networks

The Canadian Food Inspection Agency required the meat industry to ensure Escherichia coli O157:H7 does not survive (experiences > or = 5 log CFU/g reduction) in dry fermented sausage (salami) during processing after a series of foodborne illness outbreaks resulting from this pathogenic bacterium occurred. The industry is in need of an effective technique like predictive modeling for estimating bacterial viability, because traditional microbiological enumeration is a time-consuming and laborious method. The accuracy and speed of artificial neural networks (ANNs) for this purpose is an attractive alternative (developed from predictive microbiology), especially for on-line processing in industry. Data from a study of interactive effects of different levels of pH, water activity, and the concentrations of allyl isothiocyanate at various times during sausage manufacture in reducing numbers of E. coli O157:H7 were collected. Data were used to develop predictive models using a general regression neural network (GRNN), a form of ANN, and a statistical linear polynomial regression technique. Both models were compared for their predictive error, using various statistical indices. GRNN predictions for training and test data sets had less serious errors when compared with the statistical model predictions. GRNN models were better and slightly better for training and test sets, respectively, than was the statistical model. Also, GRNN accurately predicted the level of allyl isothiocyanate required, ensuring a 5-log reduction, when an appropriate production set was created by interpolation. Because they are simple to generate, fast, and accurate, ANN models may be of value for industrial use in dry fermented sausage manufacture to reduce the hazard associated with E. coli O157:H7 in fresh beef and permit production of consistently safe products from this raw material.     

Survival of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in cranberry juice concentrates at different oBrix levels

Survival of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes was evaluated in cranberry juice concentrates to determine if a 5-log reduction could be achieved without any other treatment. Inactivation at 0 degrees C in concentrates with different oBrix levels was determined for a five-strain composite of the individual pathogens in two physiological states. In concentrates at 18 to 46 oBrix (pH 2.2 to 2.5), all three pathogens (stationary-phase or acid-adapted cells) showed at least a 5-log reduction after a 6- or 24-h incubation. At 14 oBrix (pH 2.5), a reduction greater than 5 log was obtained for L. monocytogenes and Salmonella after up to 24 h of incubation, but for E. coli O157:H7, 96 h of incubation was needed to consistently obtain a reduction greater than 5 log. All three pathogens in the stationary phase survived longer than in the acid-adapted phase under the same conditions. The most resistant was stationary-phase E. coli O157:H7, and the most sensitive was acid-adapted L. monocytogenes. The rate of pathogen destruction increased with increasing oBrix level of the juice concentrate, which suggests that concentrated acids and/orsome intrinsic compounds may play an important role in the bactericidal effects of cranberry juice concentrates.     

Simultaneous detection of Escherichia coli O157:H7, Listeria monocytogenes and Salmonella strains by real-time PCR

A protocol enabling simultaneous detection of Escherichia coli O157:H7, Listeria monocytogenes and Salmonella strains was devised and evaluated using artificially contaminated fresh produce. Association of Official Analytical Chemists (AOAC)-approved polymerase chain reaction (PCR) detection methods for three human pathogens were modified to enable simultaneous and real-time detection with high throughput capability. The method includes a melting-curve analysis of PCR products, which serves as confirmatory test. The modified protocol successfully detected all three pathogens when fresh produce was washed with artificially contaminated water containing E. coli O157:H7 and S. typhimurium down to the predicted level of 1 to 10 cells/ml and L. monocytogenes at 1000 cells/ml. The ability to monitor several pathogens simultaneously will save time and increase our ability to assure food safety.     

Survival of Escherichia coli O157:H7, Salmonella enteritidis, Staphylococcus aureus, and Listeria monocytogenes in Kimchi

The survival of gram-positive and gram-negative foodborne pathogens in both commercial and laboratory-prepared kimchi (a traditional fermented food widely consumed in Japan) was investigated. It was found that Escherichia coli O157:H7, Salmonella Enteritidis, Staphylococcus aureus, and Listeria monocytogenes could survive in both commercial and laboratory-prepared kimchi inoculated with these pathogens and incubated at 10 degrees C for 7 days. However, when incubation was prolonged, the S. aureus level decreased rapidly from the initial inoculum level to the minimum detectable level within 12 days, whereas Salmonella Enteritidis and L. monocytogenes took 16 days to reach similar levels in commercial kimchi. On the other hand, E. coli O157:H7 remained at high levels throughout the incubation period. For laboratory-prepared kimchi, the S. aureus level decreased rapidly from the initial inoculum level to the minimum detectable level within 12 days, and L. monocytogenes took 20 days to reach a similar level. E. coli O157:H7 and Salmonella Enteritidis remained at high levels throughout the incubation period. The results of this study suggest that the contamination of kimchi with E. coli O157:H7, Salmonella Enteritidis, S. aureus, or L. monocytogenes at any stage of production or marketing could pose a potential risk.     

Survival ofEscherichia coliO157:H7,Listeria monocytogenesandSalmonella kentuckyin Norwegian fermented,dry sausage

Raw, newly produced sausages containing a mixed starter culture of lactobacilli and micrococci were each inoculated at separate locations (using a syringe) with low (10³–10⁴cfu) and high (10⁵–10⁷cfu) numbers of eitherEscherichia coliO157:H7, Listeria monocytogenes orSalmonella kentucky. Three identically prepared sausages were analysed at each sampling day during fermentation, maturation and storage at 4 and 20°C. In the low-inoculum samples, growth was observed initially (2 days) during fermentation forE. coliO157:H7 (3log₈increase in cfu) andL. monocytogenes(five-fold increase in cfu) but not forS. kentuckywhich decreased below the detection limit (150cfu sample^–1). None of the pathogens was detected after 5.5 months, neither at 4 nor 20°C. In the high-inoculum samples there was a decrease during fermentation and maturation for all the pathogens. After 5.5-months storage at 4°C, there was only about 90% reduction of the original inoculate ofL. monocytogenes, whereasE. coliO157:H7 survived at a low number (500cfu sample^–1) andS. kentuckydisappeared below the detection limit. After 5.5-months storage at 20°C, all the pathogens had disappeared below the detection limit. These results indicate that, from a safety point of view, it may be better to store these kinds of sausages at room temperature than in the cold, provided that the sensory qualities are retained and that similar results are obtained with other food pathogens.     

Growth and survival of Escherichia coli O157:H7 and Listeria monocytogenes in egg products held at different temperatures

Growth and survival of Escherichia coli O157:H7 and Listeria monocytogenes in steamed eggs and scrambled eggs held at different temperatures (5, 18, 22, 37, 55, and 60 degrees C) were investigated in the present study. Among the holding temperatures tested, both pathogens multiplied best at 37 degrees C followed by 22, 18, and 5 degrees C. In general, E. coli O157:H7 grew better in the egg products than L. monocytogenes did at all the storage temperatures tested except at 5 degrees C. E. coli O157:H7 did not grow in steamed eggs and scrambled eggs held at 5 degrees C. L. monocytogenes showed a slight population increase of approximately 0.6 to 0.9 log CFU/g in these egg products at the end of the 36-h storage period at 5 degrees C. The population of both pathogens detected in the egg products was affected by the initial population, holding temperature, and length of the holding period. It was also noted that L. monocytogenes was more susceptible than E. coli O157:H7 in steamed eggs held at 60 degrees C. After holding at 60 degrees C for 1 h, no detectable viable cells of L. monocytogenes with a population reduction of 5.4 log CFU/g was observed in steamed eggs, whereas a lower population reduction of only approximately 0.5 log CFU/ml was noted for E. coli O157:H7.     

Inactivation of Listeria monocytogenes and Escherichia coli O157:H7 biofilms by micelle-encapsulated eugenol and carvacrol

Carvacrol and eugenol were encapsulated in micellar nonionic surfactant solutions to increase active component concentrations in the aqueous phase and used to treat two strains of Listeria monocytogenes (Scott A and 101) and two strains of Escherichia coli O157:H7 (4388 and 43895) grown as biofilms in a Centers for Disease Control and Prevention reactor. L. monocytogenes biofilms were grown in two different growth media, 1:20 TSB and Modified Welshimer's broth (MWB), while E. coli O157:H7 was grown in M9. In general, L. monocytogenes strains were more resistant to both micelle-encapsulated antimicrobials than E. coli O157:H7 strains. The two antimicrobials were equally effective against both strains of E. coli O157:H7, decreasing viable counts by 3.5 to 4.8 log CFU/cm(2) within 20 min. For both bacteria, most of the bactericidal activity took place in the first 10 min of antimicrobial exposure. Biofilm morphology and viability were assessed by the BacLight RedoxSensor CTC Vitality kit and confocal scanning laser microscopy, revealing an increasing number of dead cells when biofilms were treated with sufficiently high concentrations of carvacrol- or eugenol-loaded micelles. This study demonstrates the effectiveness of the application of surfactant-encapsulated essential oil components on two pathogen biofilm formers such as E. coli O157:H7 and L. monocytogenes grown on stainless steel coupons.     

Effectiveness of two cooking systems in destroying Escherichia coli O157:H7 and Listeria monocytogenes in ground beef patties

A rapid, high-temperature double-sided grilling-broiling (DGB) system was compared to a single-sided broiling (SSB) system for cooking of foodservice ground beef patties to reduce microbial numbers and maintain textural quality. Patties (110 g) containing either Escherichia coli O157:H7 or Listeria monocytogenes (10(6-7) CFU/g) were cooked to target internal temperatures of 60 or 68 degrees C on each cooking system and immediately removed from the grills without the additional holding time at 60 or 68 degrees C that is recommended for foodservice cooking of ground beef patties. Actual final internal temperature attained, position on the grill, degree of doneness, cooking time, after-cook weight, texture characteristics, and bacterial counts of the patties were monitored. The DGB reduced E. coli O157:H7 and L. monocytogenes populations in ground beef patties by 5.7 log10 and 5.4 log10 CFU/g, respectively, when cooked to a target temperature of 60 degrees C (actual final internal temperature of 71.2 degrees C) and by 6.1 log10 and 5.6 log10 CFU/g, respectively, when cooked to a target temperature of 68 degrees C (actual final internal temperature of 75.8 degree C). The SSB reduced E. coli O157:H7 and L. monocytogenes populations by 1.3 log10 and 1.8 log10 CFU/g, respectively, when cooked to a target temperature of 60 degrees C (actual final internal temperature of 62.7 degrees C) and by 2.9 log10 and 3.6 log10 CFU/g, respectively, when cooked to a target temperature of 68 degrees C (actual final internal temperature of 69.3 degrees C). The DGB system effected a higher, more rapid temperature increase in patties cooked to either target temperature compared to the SSB system. This higher temperature was more effective in destroying pathogens in beef patties. Texture analyses determined that patties cooked on the DGB system had significantly higher values for springiness, adhesiveness, and product height as compared to the SSB system, and patties cooked on either system had significantly higher hardness, gumminess, chewiness, and product height values at the target temperature of 68 degrees C as compared to 60 degrees C.     

Antimicrobial efficacy of eugenol microemulsions in milk against Listeria monocytogenes and Escherichia coli O157:H7

The antimicrobial activity of eugenol microemulsions (eugenol encapsulated in surfactant micelles) in ultrahigh-temperature pasteurized milk containing different percentages of milk fat (0, 2, and 4%) was investigated. Antimicrobial microemulsions were prepared from a 5% (wt) aqueous surfactant solution (Surfynol 485W) with 0.5% (wt) eugenol. Two strains each of Listeria monocytogenes and Escherichia coli O157:H7 previously shown to be the least and most resistant to the microemulsion in microbiological media were used to inoculate sterile milk (10(4) CFU/ml). Samples were withdrawn and plated at 0, 1, 3, 6, 12, and 24 h for enumeration. Microemulsions completely prevented growth of L. monocytogenes for up to 48 h in skim milk and reduced both strains of E. coli O157:H7 to less than detectable levels in less than 1 h. Similarly, in 2% fat milk, eugenol-Surfynol combinations reduced both strains of E. coli O157:H7 to less than detectable levels in less than 1 h but only increased the lag phase of both strains of L. monocytogenes. In full-fat milk (4% fat), microemulsions inhibited growth of the least resistant strains of L. monocytogenes and E. coli but were ineffective against the two resistant strains. Unencapsulated eugenol was slightly more or as inhibitory as microemulsions against target pathogens. Results were attributed to diffusional mass transport of antimicrobials from microemulsions to the macroemulsion (milk). Results suggest that food composition, especially fat level, may affect the efficiency of targeting of foodborne pathogens with surfactant-encapsulated antimicrobials.     

Survival and growth of Listeria monocytogenes and Escherichia coli O157:H7 in ready-to-eat iceberg lettuce washed in warm chlorinated water

Cut iceberg lettuce inoculated with Escherichia coli O157:H7 and Listeria monocytogenes before and after washing for 3 min in cold (4 degrees C) and warm (47 degrees C) water containing 100 mg/liter total chlorine was stored at I and 10 degrees C in oxygen-permeable film packages (6,000 to 8,000 cc/m2/24 h). Cold chlorinated water was detrimental to the survival of E. coli O157: H7 and L. monocytogenes at both storage temperatures. In contrast, washing in warm chlorinated water favored the growth of both pathogens in lettuce stored at 10 degrees C. There was no evidence of a relationship between the magnitude of spoilage microflora and the fate of either bacterium.     

Inhibition of Escherichia coli O157:H7 in ripening dry fermented sausage by ground yellow mustard

Compounds generated by the enzymatic hydrolysis of glucosinolates naturally present in mustard powder are potently bactericidal against Escherichia coli O157:H7. Because E. coli O157:H7 can survive the dry fermented sausage manufacturing process, 2, 4, and 6% (wt/wt) nondeheated (hot) mustard powder or 6% (wt/wt) deheated (cold) mustard powder were added to dry sausage batter inoculated with E. coli O157:H7 at about 7 log CFU/g to evaluate the antimicrobial effectiveness of the powders. Reductions in E. coli O157:H7 populations, changes in pH and water activity (aw), effects on starter culture (Pediococcus pentosaceus and Staphylococcus carnosus) populations, and effects of mustard powder on sausage texture (shear) were monitored during ripening. Nondeheated mustard powder at 2, 4, and 6% in dry sausage (0.90 aw) resulted in significant reductions in E. coli O157:H7 (P < 0.05) of 3.4, 4.4, and 6.9 log CFU/g, respectively, within 30 days of drying. During fermentation and drying, mustard powder did not affect P. pentosaceus and S. carnosus activity in any of the treatments. Extension of drying to 36 and 48 days reduced E. coli O157:H7 by >5 log CFU/g in the 4 and 2% mustard powder treatments, respectively. The 6% deheated mustard powder treatment provided the most rapid reductions of E. coli O157:H7 (yielding <0.20 log CFU/g after 24 days) by an unknown mechanism and was the least detrimental (P < 0.05) to sausage texture.     

Optimization of rapid detection of Escherichia coli O157:H7 and Listeria monocytogenes by PCR and application to field test

For rapid detection of Escherichia coli O157:H7 and Listeria monocytogenes, simple methods for sample preparation and PCR were established and applied to a field test. To improve specificity, primer sets LP43-LP44 and C(+)-D(-) were selected for E. coli O157:H7 and L. monocytogenes, respectively. Through centrifugation and partial heat treatment after enrichment, E. coli O157:H7 and L. monocytogenes were detected at 1 initial CFU without genomic DNA extraction in the culture and with artificially inoculated food samples including milk, chicken, ham, and pork. Based on the optimized PCR method, a feasibility test was carried out using randomly collected field samples. To remove false positives and false negatives, a PCR method using several primer sets, including the optimized primer set, and a standard culture method were used. With the PCR detection and standard culture methods, two pork samples were positive for L. monocytogenes after enrichment, indications that the PCR assay could be effectively used for rapid, sensitive, and species-specific detection of foodborne pathogens.     

Survival of acid-adapted or non-adapted Salmonella Enteritidis, Listeria monocytogenes and Escherichia coli O157:H7, in traditional Greek salads

The fate of three pathogens Salmonella Enteritidis, Listeria monocytogenes and Escherichia coli O157:H7 that were inoculated in fish roe salad and aubergine salad with or without preservatives after being adapted in acid environment or not, was determined. The salads were stored at 10  ° C and the pathogens population was counted at regular intervals. Parameters (lag time, death rates calculated with Baranyi equation) were used to compare the behaviour of the pathogens. In the absence of preservatives the pathogens survived during the 15 days of storage. A 1 log reduction was observed for Listeria and 2 logs reduction for Salmonella and E. coli in both salads. In most cases, acid adaptation decreased the death rate even in the presence of preservatives. The addition of sorbic and benzoic acid in the salads increased the death rate of the pathogens during storage significantly and they were not detected at 7–10 days for Salmonella , 8–12 days for Listeria and 5 days for E. coli . It is concluded that a well-studied combination of hurdles is appropriate to ensure safety of home-made traditional salads free of preservatives.