Reduction of Listeria monocytogenes in cold‐smoked salmon by bacteriophage P100, nisin and lauric arginate,singly or in combinations

Three GRAS antimicrobials including, lauric arginate (LAE), bacteriophage P100 (phage P100) and bacteriocin nisin, were evaluated either singly or in combinations for the reduction of initial load of Listeria monocytogenes in cold‐smoked salmon (CSS). The stability of phage P100 in the presence of LAE (200 ppm) and nisin (500 ppm) or at 10× and 100× of these concentrations was determined at 4 °C or 30 °C for 24 h in a broth model. Phage P100 was found to be highly stable in the presence of these antimicrobial agents as plaque‐forming units (PFU) did not vary between control and antimicrobial‐treated phage. The survival of L. monocytogenes in the presence of phage P100, nisin and LAE showed remarkable reduction within 24 h both at 4 °C or 30 °C in broth. Treatment of CSS containing 3.5 log CFU cm^?2 L. monocytogenes with phage P100 (10⁸ PFU mL^?1), nisin (500 ppm) and LAE (200 ppm) showed strong listericidal action and reduced the L. monocytogenes by 2–3 log CFU cm^?2 after 24 h. Among the combined treatments, phage P100 + LAE or nisin + LAE exhibited the most listericidal action in which L. monocytogenes cells were reduced to undetectable level within 24 h in CSS.     

Efficacies of Garlic and L. sakei in Wine‐Based Marinades for Controlling Listeria monocytogenes and Salmonella spp. in Chouriço de Vinho,a Dry Sausage Made from Wine‐Marinated Pork

Chouriço de vinho is made from roughly minced (10 to 30 mm) pork and fat, seasoned with a marinade made from wine, salt, garlic, and other facultative seasonings used according to the recipe of each producer. The batter is maintained at 4 to 7 ºC for 24 to 48 h. It is then stuffed into natural thin pork gut, cold smoked and matured at a low temperature for 1 to 4 wk. The effect of garlic used in wine‐based marinade and a starter culture of indigenous Lactobacillus sakei on the behavior of Listeria monocytogenes and Salmonella spp. in the processing of chouriço was investigated. The garlic (as powder and fresh juice) was found to contribute (P < 0.05) to the control of both pathogens in broth. Garlic dose, as tested within the usual limits used for seasoning, did not impact the reduction of pathogens. Garlic‐wine‐based marinade and a starter culture of indigenous L. sakei contribute to controlling L. monocytogenes and Salmonella spp. in the processing of chouriço. Their presence was responsible for the loss of viability of L. monocytogenes and Salmonella spp. following 5 d of drying, even sooner than situations where no garlic was used. The results of the present work show that the use of a wine‐based marinade with garlic has an important role in ensuring the safety of the product.     

Effect of Product Dimensions and Surface Browning Method on Salmonella Contamination in Frozen,Surface‐Browned,Breaded Chicken Products Treated with Antimicrobials

Not‐ready‐to‐eat breaded chicken products formulated with antimicrobial ingredients were tested for the effect of sample dimensions, surface browning method and final internal sample temperature on inoculated Salmonella populations. Fresh chicken breast meat portions (5 × 5 × 5 cm), inoculated with Salmonella (7‐strain mixture; 5 log CFU/g), were mixed with (5% v/w total moisture enhancement) (i) distilled water (control), (ii) caprylic acid (CAA; 0.0625%) and carvacrol (CAR; 0.075%), (iii) CAA (0.25%) and ε‐polylysine (POL; 0.5%), (iv) CAR (0.15%) and POL (0.5%), or (v) CAA (0.0625%), CAR (0.075%) and POL (0.5%). Sodium chloride (1.2%) and sodium tripolyphosphate (0.3%) were added to all treatments. The mixtures were then ground and formed into 9 × 5 × 3 cm (150 g) or 9 × 2.5 × 2 cm (50 g) portions. The products were breaded, browned in (i) an oven (208 °C, 15 min) or (ii) deep fryer (190 °C, 15 s), packaged, and stored at –20 °C (8 d). Overall, maximum internal temperatures of 62.4 ± 4.0 °C (9 × 2.5 × 2 cm) and 46.0 ± 3.0 °C (9 × 5 × 3 cm) were reached in oven‐browned samples, and 35.0 ± 1.1 °C (9 × 2.5 × 2 cm) and 31.7 ± 2.6 °C (9 × 5 × 3 cm) in fryer‐browned samples. Irrespective of formulation treatment, total (after frozen storage) reductions of Salmonella were greater (P < 0.05) for 9 × 2.5 × 2 cm oven‐browned samples (3.8 to at least 4.6 log CFU/g) than for 9 × 5 × 3 cm oven‐browned samples (0.7 to 2.5 log CFU/g). Product dimensions did not (P ≥ 0.05) affect Salmonella reductions (0.6 to 2.8 log CFU/g) in fryer‐browned samples. All antimicrobial treatments reduced Salmonella to undetectable levels (<0.3 log CFU/g) in oven‐browned 9 × 2.5 × 2 cm samples. Overall, the data may be useful for the selection of antimicrobials, product dimensions, and surface browning methods for reducing Salmonella contamination.     

Effect of carvacrol and thymol on Salmonella spp. biofilms on polypropylene

The present study evaluated the effects of carvacrol and thymol against Salmonella spp. biofilm on polypropylene. The efficacy of the compounds was assessed by quantifying Salmonella spp. cells during and after biofilm formation on polypropylene and performing scanning electron microscopy. During biofilm formation, carvacrol and thymol, at subinhibitory concentrations, reduced bacterial counts about 1–2 log, while established Salmonella spp. biofilms were reduced about 1–5 log by carvacrol and thymol, at MIC or 2× MIC. The greatest reduction in carvacrol‐treated biofilms, about 5 log, was observed with 156 and 312 μg mL^?1 (MIC and 2× MIC) in established Salmonella Typhimurium ATCC 14028 biofilms. Thymol showed the greatest reduction, about 4 log, at 624 μg mL^?1 (2× MIC) against mature Salmonella Enteritidis biofilm. Carvacrol and thymol reduced the number of Salmonella spp. cells on polypropylene, suggesting their potential for the control of Salmonella spp. biofilms.     

Effect of nisin‐producing Lactococcus lactis starter cultures on the inhibition of two pathogens in ripened cheeses

The effect of Lactococcus lactis nisin‐producing strains, isolated from Italian fermented foods, on the survival of two foodborne pathogens namely Listeria monocytogenes and Staphylococcus aureus was investigated in experimental cheese production. One of the three Lactobacillus lactis nisin innoculated as starters, Lactobacillus lactis 41FL1 lowered S. aureus count by 1.73 log colony‐forming units (cfu)/g within the first 3 days, reaching the highest reduction, 3.54 log cfu/g, by the end of ripening period of 60 days. There was no effect on L. monocytogenes. The application of L. lactis 41FL1 as bioprotective culture in controlling S. aureus shows considerable promise.     

Effects of fermentation conditions on the potential anti‐hypertensive peptides released from yogurt fermented by Lactobacillus helveticus and Flavourzyme®

This study investigates the effects of fermentation conditions on the production of angiotensin‐converting enzyme inhibitory (ACE‐I) peptides in yogurt by Lactobacillus helveticus 881315 (L. helveticus) in the presence or absence of Flavourzyme^®, which is derived from a mould, Aspergillus oryzae and used for protein hydrolysis in various industrial applications. Optimal conditions for peptides with the highest ACE‐I activity were 4% (v/w) inoculum size for 8 h without Flavourzyme^® supplementation, and 1% inoculum size for 12 h when combined with Flavourzyme^®. The yogurt fermented by L. helveticus resulted in IC₅₀ values (concentration of inhibitor required to inhibit 50% of ACE activity under the assayed conditions) of 1.47 ± 0.04 and 16.91 ± 0.25 mg mL^?1 with and without Flavourzyme^® respectively. Seven fractions of ACE‐I peptides from the yogurt incorporated with L. helveticus and Flavourzyme^® were separated using the preparative high‐performance liquid chromatography. Fraction (F3) showed the highest ACE‐I activity with an IC₅₀ of 35.75 ± 5.48 μg mL^?1. This study indicates that yogurt may be a valuable source of ACE‐I peptides, which may explain the outcomes observed in the experimental and clinical studies and foresee the application of fermented milk proteins into functional foods or dietary supplements.     

Development of vacuum‐dried probiotic milk powder with Bacillus coagulans

The present study explored the possibilities of using Bacillus coagulans as a probiotic culture in vacuum‐dried milk powder. The operational drying temperature at 63 ± 2 °C under 0.7 kg/cm² pressure emerged as the best temperature at which to prepare dried milk powder within 4.5 h with a mean (±SEM) Bacillus coagulans B37 spore count of 8.78 ± 0.03 log cfu/g and moisture content of 4.82 ± 0.12%. The total spore counts in vacuum‐dried milk powder did not change (P > 0.10) at storage temperatures of 7 °C, 37 °C or 45 °C over a three‐month period.     

Modelling the cross‐contamination of Listeria monocytogenes in pork during bowl chopping

This study has developed a predictive model for the cross‐contamination of pork by Listeria monocytogenes during bowl chopping. The transfer rates of L. monocytogenes were measured in sixteen chopping scenarios based on practical work. Meanwhile, contaminated bowl chopper was cleaned with either a dry rag (DR), warm water (WW) or 70% ethanol + water (EW), respectively. It was showed that significant differences (P < 0.05) were observed among the three cleaning methods on the reduction of L. monocytogenes, the greatest log reduction being achieved by EW. Moreover, the model introduced by a previous study, predicting cross‐contamination of L. monocytogenes during meat slicing, was improved and validated in this study. Verification results showed that the improved model was acceptable for predicting L. monocytogenes cross‐contamination during pork chopping with coefficients of determination (R² > 0.82), accuracy factors (A_f < 1.44), bias factors (B_f < 1.42), and root mean square error (RMSE < 0.99). Furthermore, the modified model might provide an effective tool for assessing the risk of the cross‐contamination of meat products.     

Interaction of β‐casein with (−)‐epigallocatechin‐3‐gallate assayed by fluorescence quenching: effect of thermal processing temperature

The interactions between the flavan‐3‐ol (?)‐epigallocatechin‐3‐gallate (EGCG) and bovine β‐casein in phosphate‐buffered saline (PBS) of pH 6.5 subjected to thermal processing at various temperatures (25–100 °C) were investigated using fluorescence quenching. The results indicated that different temperatures had different effects on the structural changes and EGCG‐binding ability of β‐casein. At temperatures below 60 °C, the β‐casein–EGCG interaction changed little (P > 0.05) with increasing temperature. At temperatures above 80 °C, native assemblies of β‐casein in solution dissociated into individual β‐casein molecules and unfolded, as demonstrated by a red shift of the maximum fluorescence emission wavelength (λ_max) of up to 8.8 nm. The highest quenching constant (K_q) and the number of binding sites (n) were 0.92 (±0.01) × 10¹³ m ^?1 s^?1 and 0.73 (±0.02) (100 °C), respectively. These results provide insight into the potential of interactions between β‐casein–EGCG that may modulate bioactivity or bioavailability to be altered during thermal process.     

Biofilm Formation of O157 and Non‐O157 Shiga Toxin‐Producing Escherichia coli and Multidrug‐Resistant and Susceptible Salmonella Typhimurium and Newport and Their Inactivation by Sanitizers

This study compared biofilm formation by 7 serogroups of pathogenic Escherichia coli and 2 or 3 phenotypes of Salmonella (susceptible, multidrug‐resistant [MDR], and/or multidrug resistant with ampC gene [MDR‐AmpC]). One‐week mature biofilms were also exposed to water, quaternary ammonium compound‐based (QAC), and acid‐based (AB) sanitizers. Seven groups (strain mixture) of above‐mentioned pathogens were separately spot‐inoculated onto stainless steel coupons surfaces for target inoculation of 2 log CFU/cm², then stored statically, partially submerged in 10% nonsterilized meat homogenate at 4, 15, and 25 °C. Biofilm cells were enumerated on days 0, 1, 4, and 7 following submersion in 30 mL for 1 min in water, QAC, and AB. Counts on inoculation day ranged from 1.6 ± 0.4 to 2.4 ± 0.6 log CFU/cm² and changed to 1.2 ± 0.8 to 1.9 ± 0.8 on day 7 at 4 °C with no appreciable difference among the 7 pathogen groups. After treatment with QAC and AB on day 7, counts were reduced (P < 0.05) to less than 0.7 ± 0.6 and 1.2 ± 0.5, respectively, with similar trends among pathogens. Biofilm formation at higher temperatures was more enhanced; E. coli O157:H7, as an example, increased (P < 0.05) from 1.4 ± 0.6 and 2.0 ± 0.3 on day 0 to 4.8 ± 0.6 and 6.5 ± 0.2 on day 7 at 15 and 25 °C, respectively. As compared to 4 °C, after sanitation, more survivors were observed for 15 and 25 °C treatments with no appreciable differences among pathogens. Overall, we observed similar patterns of growth and susceptibility to QAC and AB sanitizers of the 7 tested pathogen groups with enhanced biofilm formation capability and higher numbers of treatment survivors at higher temperatures.     

Production of bioactive proteins and peptides from the diatom Nitzschia laevis and comparison of their in vitro antioxidant activities with those from Spirulina platensis and Chlorella vulgaris

This research focuses on green production of bioactive proteins and hydrolysates from Nitzschia. A comparison of antioxidant activities was established between protein extracts and hydrolysates from Nitzschia and two other well‐known microalgae, chlorella and spirulina. Protein hydrolysates from these microalgae were produced using Alcalase^®, Flavourzyme^® and Trypsin. The hydrolysis process enhanced the antioxidant activities in general, especially those obtained using Alcalase^®. Nitzschia showed the highest (P < 0.05) total phenolic content/reducing capacity (2.4 ± 0.02 mg GAE/100 g) after 90 min of hydrolysis with Alcalase^®. The ABTS [2,2′‐Azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid)] radical scavenging activity (66.77 ± 0.00%) was highest (P < 0.05) after 120 min of hydrolysis, but DPPH (2,2‐Diphenyl‐1‐picrylhydrazyl radical) was low (29.59 ± 0.02%). A correlation between ABTS activity and total phenolic contents was the highest (P < 0.05) for protein hydrolysates from all three organisms using Alcalase^®, but superoxide anion radical scavenging activity was intermediate for Nitzschia. Therefore, Nitzschia protein hydrolysates have the potential to be used as antioxidants.     

Thermo‐rheological and functional properties of gamma‐irradiated wholewheat flour

The effects of different doses (0, 0.5, 1, 2.5, 5 and 10 kGy) of gamma irradiation on the thermal, rheological and functional properties of the wholewheat flour were evaluated. Water and oil absorption capacity of the flour increased from 85.92% to 91.44% and 1.10 to 1.91 g g^?1 of flour, respectively, with increase in irradiation dose. The dough development time decreased with dose from 4.0 to 3.0 min. The transition temperatures (T_o, T_p and T_c) decreased as the dose increased; enthalpy of gelatinisation (?H) decreased from 5.18 to 4.27 J g^?1 with dose. The flow behaviour showed a shear‐thinning behaviour, and the hysteresis area decreased with dose. The structural recovery decreased with dose. FTIR did not show formation of any new chemical groups.     

Radiation sensitivity of planktonic and biofilm‐associated Shigella spp. and Aeromonas spp. on food and food‐contact surfaces

Although ionising radiation has been shown to kill human pathogens Shigella spp. and Aeromonas spp. on various food products, there is lack of information regarding the relative efficacy of gamma radiation against their free‐living planktonic and biofilm‐associated cells. The radiation sensitivity (D₁₀ values) of planktonic, glass‐ and carrot‐associated biofilm cells of Shigella spp. and Aeromonas spp. was determined by forming biofilms on sterile glass and carrot surfaces, incubated at 37 °C (Shigella spp.) and 30 °C (Aeromonas spp.) for 48 h. No significant difference in the D₁₀ values of planktonic and glass‐associated biofilm cells of Shigella spp. and Aeromonas spp. was observed. However, significant increase in the D₁₀ values of carrot‐associated biofilm cells as compared to planktonic and glass‐associated biofilm cells of Shigella spp. and A. hydrophila A331 was observed, whereas A. salmonicida Y567 showed insignificant difference. SEM analysis further validated the formation of biofilm on the carrot and glass surfaces. The antimicrobial effectiveness of ionising radiation against both Shigella spp. and Aeromonas spp. is affected by growth form, strain and nature of attachment surface.     

High bacterial contamination of pig tonsils at slaughter

Food-borne zoonoses have a major health impact in industrial countries. Campylobacter spp., Salmonella enterica, Yersinia enterocolitica and Listeria monocytogenes are high-risk food-borne zoonotic hazards in finishing pigs. The objectives of this work were (1) to study the isolation rate of pathogenic Y. enterocolitica, Salmonella spp., Campylobacter spp. and L. monocytogenes in the tonsils and feces and (2) to determine the number of mesophilic aerobic bacteria (MAB) and Escherichia coli in the tonsils of fattening pigs at slaughter. The samples, which were collected from one slaughterhouse on five occasions, originated from 50 pigs and 15 farms. The number of MAB varied from 6.40 to 7.82 log₁₀ CFU/g and E. coli from 4.38 to 6.53 log₁₀ CFU/g. Additionally, 31 (62%) of the tonsils were colonized with Y. enterocolitica and 16 (32%) with L. monocytogenes. Campylobacter spp. were more frequently excreted in feces and only 3 (6%) of the pigs carried Campylobacter spp. in the tonsils. No Salmonella spp. were isolated. The pig tonsils were shown to be colonized with a high number of bacteria including E. coli, which is the most important indicator for fecal contamination, and with Y. enterocolitica and L. monocytogenes, which are important food-borne pathogens. This study demonstrates that the tonsils are highly contaminated with micro-organisms and can be a very important source of contamination in the slaughterhouse.     

Untersuchungen zum mikrobiellen und viralen Kontaminationsstatus von Garnelen aus Aquakultur

In der vorliegenden Untersuchung wurden 111 Proben roher, aus Drittl?ndern importierter Garnelen aus Aquakultur auf bakterielle Erreger und auf humanpathogene Viren untersucht. Die Garnelen stammten bis auf acht lateinamerikanische Proben aus Südostasien. Am h?ufigsten waren Proben aus Bangladesh vertreten (n=40). Das Untersuchungsspektrum umfasste die Ermittlung des aeroben mesophilen Gesamtkeimgehalts, die quantitative Untersuchung auf Escherichia coli und Staphylococcus aureus und den qualitativen Nachweis von Salmonella spp., Vibrio spp. und Listeria monocytogenes. Der Nachweis des humanpathogenen Rotavirus, des Norovirus und des Hepatitis A-Virus erfolgten jeweils mittels einer nested RT-PCR. Bei den untersuchten Proben wurden Gesamtkeimgehalte von 4,8×10² bis 1,3×10⁹ KbE/g ermittelt. Davon hatten vierzehn Proben (12,6%) einen aeroben mesophilen Gesamtkeimgehalt >10⁷ KbE/g. In einer Probe konnte Escherichia coli mit einer Keimzahl von 1,9×10³ KbE/g isoliert werden. In 16 Proben wurde Staphylococcus aureus nachgewiesen. Aus keiner der Garnelenproben lie? sich Listeria monocytogenes isolieren. Salmonella spp. war in acht der untersuchten Proben nachweisbar. Das am h?ufigsten isolierte Serovar war Salmonella Weltevreden.     

Microbiological quality of fresh fruit and vegetable products in Catalonia (Spain) using normalised plate‐counting methods and real time polymerase chain reaction (QPCR)

BACKGROUND: Commercially available fruits and raw and ready‐to‐eat vegetables (n = 445) were examined for aerobic, coliform, and yeast and mould counts using normalised methods. Listeria spp., Listeria monocytogenes and Salmonella spp. were detected by real time polymerase chain reaction (QPCR) after enrichment. RESULTS: Aerobic plate counts ranged from < 10 to > 10⁹ colony‐forming units (CFU) g^?1, with the lowest and highest counts recorded for fruits and sprouts respectively. The highest incidence level of coliforms was found in ready‐to‐eat vegetables, with up to 65.7% of samples containing from 5 to 9 log₁₀CFU g^?1. Yeasts and moulds showed their highest incidence level between 5 and 6 log₁₀ CFU g^?1, with an overall range from < 2 to 9 log₁₀ CFU g^?1. Salmonella spp., Listeria spp. and L. monocytogenes were detected in 0.67, 2.7 and 0.9% respectively of the total samples examined. CONCLUSION: The samples analysed can be gathered into two main groups, one showing low microbial counts (fruits) and a second group (raw whole leaves and roots and packed ready‐to‐eat vegetables) with higher microbial contamination. Although incidence levels of pathogenic bacteria reported here are in the lower range of those reported elsewhere, positive detections highlight the importance of good hygienic measures throughout the whole food chain. Copyright © 2007 Society of Chemical Industry     

Antibacterial effects of chitosan coating containing Mentha aquatica L. essence against Escherichia coli,Staphylococcus aureus and Listeria monocytogenes in Iranian white cheese

The effect of a chitosan coating and Mentha aquatica L. essence on Iranian white cheese was investigated. Results showed 100% inhibition of Escherichia coli growth using 1.5% essence after 10 days. After 15 days of incubation, the Staphylococcus aureus population was reduced by 44.2%, 70.0%, and 88.5% using 0.5, 1.0 and 1.5% essence, respectively. After 15 days, Listeria monocytogenes growth was inhibited by 63.84%, 70.12%, and 85.9% using 0.5, 1.0, and 1.5% essence, respectively. Inhibition zone diameter studies also confirmed the antibacterial effects of applied coating against all the above‐mentioned bacteria in Iranian white cheese.     

Untersuchungen zum mikrobiellen und viralen Kontaminationsstatus von Garnelen aus Aquakultur

Zusammenfassung: In der vorliegenden Untersuchung wurden 111 Proben roher, aus Drittl?ndern importierter Garnelen aus Aquakultur auf bakterielle Erreger und auf humanpathogene Viren untersucht. Die Garnelen stammten bis auf acht lateinamerikanische Proben aus Südostasien. Am h?ufigsten waren Proben aus Bangladesh vertreten (n=40). Das Untersuchungsspektrum umfasste die Ermittlung des aeroben mesophilen Gesamtkeimgehalts, die quantitative Untersuchung auf Escherichia coli und Staphylococcus aureus und den qualitativen Nachweis von Salmonella spp., Vibrio spp. und Listeria monocytogenes. Der Nachweis des humanpathogenen Rotavirus, des Norovirus und des Hepatitis A-Virus erfolgten jeweils mittels einer nested RT-PCR. Bei den untersuchten Proben wurden Gesamtkeimgehalte von 4,8×10² bis 1,3×10⁹ KbE/g ermittelt. Davon hatten vierzehn Proben (12,6%) einen aeroben mesophilen Gesamtkeimgehalt >10⁷ KbE/g. In einer Probe konnte Escherichia coli mit einer Keimzahl von 1,9×10³ KbE/g isoliert werden. In 16 Proben wurde Staphylococcus aureus nachgewiesen. Aus keiner der Garnelenproben lie? sich Listeria monocytogenes isolieren. Salmonella spp. war in acht der untersuchten Proben nachweisbar. Das am h?ufigsten isolierte Serovar war Salmonella Weltevreden. Vibrio spp. konnte mit 60 Isolaten in 49 Proben (44%) nachgewiesen werden. Am h?ufigsten wurde Vibrio cholerae non-O1 non-O139 isoliert (n=34). Aus 14 Proben konnte Vibrio parahaemolyticus isoliert werden und in fünf Proben konnte Vibrio vulnificusnachgewiesen werden. Erstmals konnte Norovirus in Garnelen nachgewiesen werden. 21 (18,9%) der untersuchten Proben waren positiv. Sowohl Rotavirus als auch Hepatitis A-Virus konnten hingegen nicht nachgewiesen werden.

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In this study 111 samples of raw imported aqua-cultured shrimps have been examined for bacterial pathogens and for pathogen viruses. The samples originated from South-East Asia except for eight Latin-American samples. Most samples were taken from Bangladesh (n=40). The bacteriological quality of these samples was analysed in terms of aerobic plate count, Escherichia coli, Staphylococcus aureus, Salmonella spp., Listeria monocytogenes and Vibrio species. Rotavirus, norovirus and hepatitis A-Virus were detected by using a nested RT-PCR. The aerobic plate count was found to be in a range between 4,8×10² to 1,3×10⁹ cfu/g. Fourteen samples (12,6%) showed an aerobic plate count >10⁷ cfu/g. One sample was found to be contaminated with Escherichia coli at a level of 1,9×10³ cfu/g. Staphylococcus aureus was isolated from sixteen samples. Listeria monocytogenes was not detected in any of the shrimp samples examined. Salmonella spp. was found in eight samples. Salmonella Weltevreden was the most frequently isolated serovar. Forty-nine shrimp samples (44%) were positive for Vibrio spp. and 60 Vibrio-isolates could be extracted. Vibrio cholerae non- O1 non-O139 was isolated in 34 samples as the most frequent species. 14 samples contained Vibrio parahaemolyticus, Vibrio vulnificus was present in five samples. For the first time Norovirus could be detected in shrimps. 21 (18,9%) of all examined samples were positive. However, both rotavirus and hepatitis A-virus could not be detected.

Eingegangen: 21. November 2007     

Antioxidant activity in HepG2 cells,immunomodulatory effects in RAW 264.7 cells and absorption characteristics in Caco‐2 cells of the peptide fraction isolated from Dendrobium aphyllum

DA‐P, fraction of peptides with a molecular weight <1 kDa isolated from Dendrobium aphyllum, was analysed in three types of cell lines to verify its bioactivity and absorptivity. The cellular antioxidant activity of DA‐P in HepG2 cells was used and results revealed an EC50 of 2.88 ± 0.143 mg mL^?1 and a CAA unit of 63.46 ± 2.11 μm QE/100 g peptides. DA‐P treatment enhanced the secretion of cytokines in RAW 264.7 cells. After demonstrating the presence of tight junctions in Caco‐2 monolayers, the absorption was 25.57% ± 0.016% and 19.7% ± 0.012% from different sides. The relatively high absorption indicated that the antioxidant‐relevant immune functions of DA‐P had a greater possibility to be absorbed by Caco‐2 cells. Free amino acids and LC‐MS/MS analysis indicated the degradation and expulsion of components after the absorption of DA‐P, and Ser‐Ser‐Arg was able to come across the monolayers.     

Comparison of antimicrobial resistance in Salmonella and Campylobacter isolated from turkeys in the Midwest USA

The current study was carried out to determine the antimicrobial resistance profiles and evaluate some molecular characteristics of a set of Salmonella and Campylobacter isolates recovered from production line turkeys in the Midwest region of the United States. A total of 94 birds identified as being positive for both Salmonella and Campylobacter spp. were selected for study. All Salmonella isolates were examined for antimicrobial resistance using the methods employed in the National Antimicrobial Resistance Monitoring System (NARMS). Campylobacter isolates were subjected to similar analysis using the Etest^®. In addition, polymerase chain reaction (PCR) was carried out to determine the presence of the antimicrobial resistance associated genes, integrase (int1), class 1 integrons (Salmonella and Campylobacter) and a multidrug efflux pump (Campylobacter spp.). Results from the study showed that the Salmonella and Campylobacter isolates examined displayed resistance to a number of antimicrobials, with Salmonella and Campylobacter isolates being resistant to at least three antimicrobials while some isolates showed resistances to 6 or 8 different antimicrobials. In addition, 68.1% of the Salmonella isolates tested were found to be positive for the class I integrase gene (int1), 28.7% possessed a 1000 bp gene cassette and 17% possessed an 800 bp gene cassette. All Campylobacter isolates were negative for int1, but 36.2% tested positive for the Campylobacter multidrug efflux pump (CmeB). A considerable number of Salmonella and Campylobacter isolates tested displayed varying degrees of antimicrobial resistance as well as the presence of some factors associated with the carriage and persistence of antimicrobial resistance. Similarities in the types of antimicrobial resistance observed in Campylobacter and Salmonella strains was evident. The results of this study suggest that prescribing practice at the farm level may be a factor in promoting antimicrobial resistance in more than one species of organism. Such practices may, therefore, contribute to the potential health risk for consumers should micro-organisms carrying multiple antimicrobial resistances enter the food chain. This study may be one of the first to report on the incidence of the multidrug efflux pump (CmeB) in Campylobacters recovered from processed turkeys. The antimicrobial resistance and molecular characteristics of Salmonella and Campylobacter is discussed.