北京市顺义区零售鸡胴体中弯曲菌分布与分子特征研究

目的研究北京市顺义区鸡胴体中弯曲菌分布和分子特征,为顺义区弯曲菌防控提供科学依据。方法采集批发市场和零售店鸡胴体60份,采用滤膜法分离培养弯曲菌,对分离菌株进行多位点序列分型分析并构建最小生成树。结果鸡胴体中弯曲菌检出率为75.0%(45/60),空肠弯曲菌与结肠弯曲菌占比分别为38.0%(19/50)和62.0%(31/50)。批发市场和零售店弯曲菌检出率分别为86.0%(37/43)和47.1%(8/17),差异有统计学意义(χ~2=9.877,P0.05);5～7月空肠弯曲菌检出率分别为10.0%(2/20)、40.0%(8/20)和45.0%(9/20),差异有统计学意义(χ~2=6.624,P0.05)。19株空肠弯曲菌共分为13个ST型;28株结肠弯曲菌共分为16个ST型。空肠弯曲菌耐药率前五位由高至低依次为四环素(100.0%,19/19)、萘啶酸(100.0%,19/19)、环丙沙星(94.7%,18/19)、氟苯尼考(57.9%,11/19)、庆大霉素(36.8%,7/19);结肠弯曲菌耐药率前五位由高至低依次为萘啶酸(100.0%,31/31)、环丙沙星(100.0%,31/31)、四环素(93.5%, 29/31)、链霉素(93.5%, 29/31)、庆大霉素(83.9%,26/31)。空肠弯曲菌和结肠弯曲菌多重耐药率分别为68.4%(13/19)和93.5%(29/31)。结论北京市顺义区市场零售鸡胴体中弯曲菌污染水平较高,结肠弯曲菌为污染的优势菌种。批发市场鸡胴体污染弯曲菌的情况比零售店严重。     

Occurrence of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella and Campylobacter spp. on beef carcasses in Northern Ireland

A survey of beef carcasses was conducted in all 10 European community approved abattoirs in Northern Ireland to determine the incidence of Escherichia coli O157:H7. Analyses were based on excised samples of neck meat taken less than 48 h post-kill. Overall, 780 carcasses were sampled and all were negative for E. coli O157:H7. A sub-set of samples was analysed for the presence of Listeria monocytogenes (n=200), Salmonella (n=200) and Campylobacter spp.(n=100). L. monocytogenes was not detected but Listeria innocua was found on five carcasses and Listeria seeligeri on one. Three carcasses carried salmonellas; Salmonella Mbandaka was found on two and Salmonella Thompson on one. Campylobacter spp. were not detected on any carcasses. The results indicate that very few beef carcasses in Northern Ireland appear to carry any of the four pathogens sought, and this may help explain the low incidence of E. coli O157:H7 in the Northern Ireland human population, relative to the rest of the UK.     

Incidence of Salmonella, Campylobacter jejuni, Campylobacter coli, and Listeria monocytogenes in poultry carcasses and different types of poultry products for sale on the Belgian retail market.

From January 1997 to May 1998, 772 samples of poultry carcasses and poultry products for sale on the retail market in Belgium were analyzed for the presence of Salmonella spp., Salmonella Enteritidis, Campylobacter jejuni, C. coli, and Listeria monocytogenes per 100 cm2 or 25 g. Poultry samples were contaminated with Salmonella (36.5%), C. jejuni and C. coli (28.5%), and L. monocytogenes (38.2%). In about 12.3% of the poultry samples, the L. monocytogenes contamination level exceeded 1 CFU per g or cm2. Significant differences in pathogen contamination rates of poultry products were noticed between the poultry products originating from Belgian, French, and U.K. abattoirs. Poultry products derived from broiler chickens running free in pine woods until slaughtering age (12 to 13 weeks) had a significantly (P < 0.05) lower contamination rate of Salmonella than poultry products from enclosed broilers slaughtered at the age of 6 to 8 weeks. A significantly (P < 0.05) lower pathogen contamination rate was noted for Salmonella, C. jejuni, and C. coli for poultry cuts without skin compared to poultry cuts with skin on. An increase in pathogen contamination rate was noticed during cutting and further processing. To diminish C. jejuni, C. coli, Salmonella, and L. monocytogenes contamination rates, hygienic rules of slaughter and meat processing must be rigorously observed. At the moment, zero tolerance for these pathogens is not feasible, and there is a need to establish criteria allowing these pathogens to be present at reasonable levels in the examined poultry samples.     

Campylobacter, Salmonella, Listeria monocytogenes, verotoxigenic Escherichia coli, and Escherichia coli prevalence, enumeration, and subtypes on retail chicken breasts with and without skin

This study examined the prevalence, counts, and subtypes of Campylobacter, Salmonella, Listeria monocytogenes, verotoxigenic Escherichia coli (VTEC), and E. coli on raw retail chicken breast with the skin on versus the skin off. From January to December 2007, 187 raw skin-on chicken breasts and 131 skin-off chicken breasts were collected from randomly selected retail grocery stores in the Region of Waterloo, Ontario, Canada. Campylobacter isolates were recovered from a higher proportion of the skin-off chicken breasts, 55 (42%) of 131, than of the skin-on chicken breasts tested, 55 (29%) of 187 (P = 0.023). There was no difference in the proportion of Salmonella isolates recovered from the two meat types (P = 0.715): 40 (31%) of 131 skin-off chicken breasts versus 61 (33%) of 187 skin-on chicken breasts. L. monocytogenes isolates were recovered from a statistically lower proportion of the skin-off chicken breasts, 15 (15%) of 99, than of the skin-on chicken breasts, 64 (34%) of 187 (P = 0.001). There was no difference in the proportion of E. coli isolates recovered from the skin-off chicken breasts, 33 (33%) of 99, than from the skin-on chicken breasts, 77 (41%) of 187 (P = 0.204). VTEC was detected on a single skin-off chicken breast. Campylobacter jejuni was the most frequent species isolated on both types of chicken meat: skin-on, 48 (87%) of 55, and skin-off, 51 (94%) of 54. Salmonella serotypes Kentucky and Heidelberg and L. monocytogenes serotype 1/2a were the most frequently detected serotypes from both skin-off and skin-on chicken breasts. Although there appeared to be a trend toward higher enumeration values of these pathogens and E. coli on the skin-on chicken, the differences did not exceed 1 log. This study suggested that skin-off chicken breast may represent a higher risk of consumer exposure to Campylobacter, a similar risk for Salmonella, VTEC, and E. coli, and a lower risk for L. monocytogenes than skin-on chicken breast.     

Contamination of carcasses with Salmonella during poultry slaughter

Successively slaughtered poultry flocks were sampled for Salmonella to study the relationship between gastrointestinal colonization of the birds and contamination of the carcasses after slaughter. Samples from 56 broiler flocks and 16 spent layer and breeder flocks were collected in six slaughterhouses. Salmonella isolates were serotyped and further characterized by pulsed-field gel electrophoresis (PFGE). Although only 7 (13%) broiler flocks were colonized with Salmonella at slaughter, carcasses of 31 (55%) broiler flocks were contaminated after slaughter. Concerning the layer and breeder flocks, 11 (69%) flocks were colonized in the gastrointestinal tract, but after slaughter, carcasses of all flocks were contaminated. The Salmonella status determined at the farm did not always correlate to the status at slaughter. On the other hand, the slaughter of Salmonella-colonized flocks did not always result in the contamination of the carcasses with the same PFGE types isolated from the gastrointestinal tract. When only uncolonized flocks were slaughtered, the carcasses of flocks were on some occasions still contaminated with Salmonella. This indicates possible cross-contamination from the slaughter equipment or transport crates. These observations show that it is difficult to reach the benefits of logistic slaughter in commercial poultry slaughterhouses.     

Antibacterial activities of phenolic benzaldehydes and benzoic acids against Campylobacter jejuni, Escherichia coli, Listeria monocytogenes, and Salmonella enterica

We evaluated the bactericidal activities of 35 benzaldehydes, 34 benzoic acids, and 1 benzoic acid methyl ester against Campylobacter jejuni, Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica when these compounds were substituted on the benzene ring with 0, 1, 2, or 3 hydroxy (OH) and/or methoxy (OCH3) groups in a pH 7.0 buffer. Dose-response plots were used to determine the percentage of the sample that induced a 50% decrease in CFU after 60 min (BA50). Of the 70 compounds tested, 24 were found to be active against all four pathogens, and additional 4, 10, and 12 were found to be active against three, two, and one of the pathogens, respectively. C. jejuni was approximately 100 times as sensitive as the other three pathogens. The 10 compounds that were most active against the four pathogens (with average BA50 values ranging from 0.026 to 0.166) and are candidates for studies of activity in foods or for disinfections were 2,4,6-trihydroxybenzaldehyde, 2,5-dihydroxybenzaldehyde, 2,3,4-trihydroxybenzaldehyde, 2-hydroxy-5-methoxybenzaldehyde, 2,3-dihydroxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 4-hydroxy-2,6-dimethoxybenzaldehyde, 2,5-dihydroxybenzaldehyde, 2,4-dihydroxybenzaldehyde. and 2-hydroxybenzaldehyde. Comparison of the chemical structures of the test compounds and their activities revealed that (i) the aldehyde (CHO) group was more active than the carboxyl (COOH) group whether or not OH groups were present; (ii) compounds were most active with trisubstituted OH > disubstituted OH > monosubstituted OH; (iii) for disubstituted derivatives, 2-OH enhanced activities were exhibited by benzaldehyde but not by benzoic acid; (iv) compounds were more active with OH than with OCH3, irrespective of the position of substitution on the benzene ring; (v) compounds with mixed OH and OCH3 groups exhibited variable results, i.e., in some cases OCH3 groups enhanced activity and in other cases they did not; (vi) methoxybenzoic acids were largely inactive; and (vii) gallic acid was 20 times as active against S. enterica at pH 7.0 as it was at pH 3.7, suggesting that the ionization of its OH groups may enhance bactericidal activity.     

Inactivation kinetics of Listeria monocytogenes,Salmonella enterica serovar Typhimurium,and Campylobacter jejuni in ready-to-eat sliced ham using UV-C irradiation

To investigate the applicability of UV-C irradiation on the inactivation of foodborne pathogenic bacteria in ready-to-eat sliced ham, UV-C treatment was evaluated. Irradiation dose required for 90% reduction of the populations of Listeria monocytogenes, Salmonella enterica serovar Typhimurium, and Campylobacter jejuni were determined to be 2.48, 2.39, and 2.18 J/m². Ready-to-eat sliced hams were inoculated with the pathogens and irradiated with UV-C light of 1000, 2000, 4000, 6000, and 8000 J/m². Microbiological data indicated that foodborne pathogen populations significantly (p < 0.05) decreased with increasing UV-C irradiation. In particular, UV-C irradiation at 8000 J/m² reduced the populations of L. monocytogenes, S. Typhimurium, and C. jejuni in the ham by 2.74, 2.02, and 1.72 log CFU/g. The results indicate that UV-C irradiation can be used as a microbial inactivation method for ready-to-eat sliced ham, and inactivation kinetics of the foodborne pathogens fit the Weibull model better than the first-order kinetics model.     

Contamination patterns of Listeria monocytogenes in cold-smoked pork processing

Contamination patterns of Listeria monocytogenes were studied in a cold-smoked pork processing plant to identify the sources and possible reasons for the contamination. Environmental sampling combined with pulsed-field gel electrophoresis (PFGE) subtyping and serotyping were applied to investigate the genetic diversity of L. monocytogenes in the plant environment and ready-to-eat (RTE) cold-smoked pork products. A total of 183 samples were collected for contamination analyses, including samples of the product at different stages during manufacture (n = 136) and environmental samples (n = 47) in 2009. L. monocytogenes isolates, previously recovered from 73 RTE cold-smoked pork samples and collected from the same meat processing plant in 2004, were included in this study. The brining machine and personnel working with brining procedures were the most contaminated places with L. monocytogenes. The overall prevalence of L. monocytogenes in raw pork (18%) increased to 60% after the brining injections. The brining machine harbored six different PFGE types belonging to serotypes 1/2a, 1/2c, 4b, and 4d, which were found on the feeding teeth, smooth surfaces, and spaces of the machine, thus potentially facilitating dissemination of L. monocytogenes contamination. Two PFGE types (2 and 8) belonging to serotypes 1/2a and 1/2c were recovered from RTE cold-smoked pork collected in 2004, and from surfaces of the brining machine sampled in 2009, and may indicate the presence of persistent L. monocytogenes strains in the plant. Due to poor hygiene design, removal of the brining machine from the production of cold-smoked meat products should be considered to reduce L. monocytogenes contamination in the finished products.     

Nonaplex real-time PCR detection of Listeria monocytogenes, Campylobacter, Salmonella and enteropathogene E. coli after universal enrichment in food samples

A universal cultivation media for Listeria monocytogenes, Salmonella and enteropathogenic Escherichia coli in conjunction with a highly efficient nonaplex PCR for the determination of L. monocytogenes, Campylobacter, Salmonella and enteropathogenic E. coli was developed and compared to classical microbiological assays. The achieved detection limit was at 2 colony-forming units per g for all analytes. The method allows screening of food samples within 24 h and is partly automatable. A ring trial showed that it can be easily established in other laboratories showing its robustness. The presented method yields results similar to the classical ISO methods based on cultivation.     

Comparison of recovery methods for freeze-injured Listeria monocytogenes,Salmonella Typhimurium,and Campylobacter coli in cell suspensions and associated with pork surfaces

Cells injured as a result of freezing, heating, and acidification treatments may not grow during conventional microbiological procedures owing to the presence of selective agents, compounds, or dyes in the media, impairing the cell's ability to repair itself and grow. Injured cells can be recovered by combining selective and nonselective media into a single system. With such combinations, the diffusion of the selective compounds or dyes is controlled, allowing for the resuscitation of injured cells of interest while also inhibiting the growth of undesirable background microflora. In this study, Listeria monocytogenes, Salmonella Typhimurium, and Campylobacter coli suspended in buffer or associated with pork surfaces were subjected to a freeze-thaw cycle (-15 degrees C for 24 h, 4 degrees C for 4 h). Following treatments, freeze-injured cells were plated on appropriate media for the overlay (OV), thin agar layer (TAL), and Lutri plate (LP) recovery methods. The levels of L. monocytogenes and Salmonella Typhimurium recovered from cell suspensions and pork surfaces by the TAL, OV, and LP methods following freeze treatments were not statistically different (P > 0.05) from recovery levels associated with nonselective media. Conversely, levels of pathogens on selective media were significantly reduced compared with those for the other methods employed. The TAL method's recovery of C. coli was not significantly different from that achieved with the nonselective media. Overall, the results presented in this study demonstrate that the TAL method not only was easier to perform, but also allowed improved isolation of single colonies for further characterization. This study may provide researchers with better methods to determine the effectiveness of industry-employed chilling processes in reducing pathogenic bacteria associated with red meat surfaces.     

Occurrence of Campylobacter and Listeria monocytogenes in a poultry processing plant

The occurrence of Campylobacter and Listeria monocytogenes was studied in 645 samples from surfaces, water, and poultry products (chicken carcasses, chicken parts, viscera, and spoils) in a poultry processing plant in southern Brazil. The automated mini-VIDAS system was used to detect the presence of Campylobacter and L. monocytogenes on the samples. The positive samples were confirmed by conventional methods. Campylobacter and L. monocytogenes were found in 16.6 and 35.6% of the analyzed samples, respectively. The sampling points with the highest Campylobacter incidence were intestine (63.3%, 19 of 30 samples), gallbladder (46.7%, 14 of 30), carcasses before evisceration (33.33%, 10 of 30), and carcasses after plucking (30%, 9 of 30). For L. monocytogenes, the majority of positive samples were from frozen breast (100%, 15 of 15 samples), frozen wing (93.3%, 14 of 15), fresh breast (83.3%, 25 of 30), fresh wing (80%, 24 of 30), skin of breast and leg (76.7%, 23 of 30), frozen leg (60%, 9 of 15), and fresh leg (50%, 15 of 30).     

Quantitative detection of Campylobacter jejuni on fresh chicken carcasses by real-time PCR.

Campylobacter jejuni infection is a significant cause of foodborne gastroenteritis worldwide. Consumption and handling of poultry products is believed to be the primary risk factor for campylobacteriosis. Risk assessments require quantitative data, and C. jejuni is enumerated usually by direct plating, which sometimes allows growth of non-Campylobacter bacteria. The objective of the present study was to develop a quantitative real-time PCR method (q-PCR) for enumerating C. jejuni in chicken rinse without a culturing step. The procedure to obtain the template for the PCR assay involved (i) filtration of 10 ml of chicken rinse, (ii) centrifugation of the sample, and (iii) total DNA extraction from the pellet obtained using a commercial DNA extraction kit. The detection limit of the method was comparable to that for plating 100 microl of chicken rinse on modified charcoal cefoperazone deoxycholate agar, and the detection limit could be further improved 10-fold by concentrating the DNA eluate by ethanol precipitation. A close correlation for spiked chicken rinse was obtained for the results of the quantitative real-time PCR method and direct plating (r = 0.99). The coefficient of correlation for the methods was 0.87 when samples from chicken carcasses on the slaughter line were analyzed, whereas a lower correlation (r = 0.76) was obtained when samples from retail carcasses were analyzed. Greater variation in the proportion of dead and/or viable but not culturable Campylobacter types in the retail samples may explain the decreased correlation between the methods. Overall, the new method is simple and fast and the results obtained are closely correlated with those for direct plating for samples containing a low proportion of dead Campylobacter cells.     

Quantitative detection of Campylobacter jejuni on fresh chicken carcasses by real-time PCR.

Campylobacter jejuni infection is a significant cause of foodborne gastroenteritis worldwide. Consumption and handling of poultry products is believed to be the primary risk factor for campylobacteriosis. Risk assessments require quantitative data, and C. jejuni is enumerated usually by direct plating, which sometimes allows growth of non-Campylobacter bacteria. The objective of the present study was to develop a quantitative real-time PCR method (q-PCR) for enumerating C. jejuni in chicken rinse without a culturing step. The procedure to obtain the template for the PCR assay involved (i) filtration of 10 ml of chicken rinse, (ii) centrifugation of the sample, and (iii) total DNA extraction from the pellet obtained using a commercial DNA extraction kit. The detection limit of the method was comparable to that for plating 100 microl of chicken rinse on modified charcoal cefoperazone deoxycholate agar, and the detection limit could be further improved 10-fold by concentrating the DNA eluate by ethanol precipitation. A close correlation for spiked chicken rinse was obtained for the results of the quantitative real-time PCR method and direct plating (r = 0.99). The coefficient of correlation for the methods was 0.87 when samples from chicken carcasses on the slaughter line were analyzed, whereas a lower correlation (r = 0.76) was obtained when samples from retail carcasses were analyzed. Greater variation in the proportion of dead and/or viable but not culturable Campylobacter types in the retail samples may explain the decreased correlation between the methods. Overall, the new method is simple and fast and the results obtained are closely correlated with those for direct plating for samples containing a low proportion of dead Campylobacter cells.     

Listeria monocytogenes, Yersinia enterocolitica, and Salmonella in dairy plant environments.

In order to determine the presence of the three environmental pathogens in dairy plants, six milk and four ice cream plants in a three state area were sampled. A total of 353 environmental samples were taken over three replications. Bacterial counts were performed on the environmental samples for chi-square analysis. Salmonella spp. were not isolated from any of the environmental samples. Yersinia enterocolitica was isolated from 6.8% of the environmental samples. Listeria monocytogenes was isolated from 6.5% of the environmental samples. Listeria spp. other than L. monocytogenes were isolated from 9.3% of the environmental samples. The presence of Y. enterocolitica was significantly related to high bacterial counts for six microbiological tests. The presence of L. monocytogenes was not related to high bacterial counts.     

D and z Values of Salmonella, Listeria innocua, and Listeria monocytogenes in Fully Cooked Poultry Products

: The D and z values of Salmonella, Listeria innocua, and Listeria monocytogenes were obtained for different ready‐to‐eat poultry products, including chicken, turkey, and duck. The D values of Salmonella, L. innocua, and L. monocytogenes were 151.5 to 0.1 min at 55 to 70°C, and the z values of Salmonella, L. innocua, and L. monocytogenes were 4.9 to 7.0 °C. Significant differences were found for the heat resistance of Salmonella, L. innocua, and L. monocytogenes among turkey, duck, and chicken products, indicating that the kinetic values of a certain pathogen in a specific product should be used for determining process lethality in fully cooked and vacuum‐packaged poultry products during post‐cook heat treatments.     

Prevalence of Listeria monocytogenes and Salmonella in ready-to-eat food in Catalonia, Spain

Listeria monocytogenes and Salmonella are pathogenic bacteria that can contaminate food products during or after processing. Ready-to-eat (RTE) food does not undergo any treatment to ensure its safety before consumption, and therefore risk of foodborne disease must be considered if these pathogens are present in the food. To evaluate the prevalence of these pathogens in RTE food, 140 RTE fish product samples, 501 RTE meat product samples, 462 RTE dairy samples, and 123 RTE dishes and desserts, providing a total of 1,226 samples, were collected from retail stores and food industry and analyzed for the presence of L. monocytogenes. A total of 1,379 samples consisting of 187 RTE fish products and 569 RTE meat products, 484 RTE dairy products, and 139 RTE dishes and desserts were collected and analyzed for the presence of Salmonella. L. monocytogenes was isolated from 20% of frozen Atlantic bonito small pies, 7.9% of smoked salmon samples, 11.1% of the pork luncheon meat samples, 6.2% of frozen chicken croquettes, 16.9% of cured dried sausage samples, 12.5% of cooked ham samples, and 20% of cooked turkey breast samples. L. monocytogenes was also found to be present in 1.3% of fresh salty cheese samples and 15.1% of frozen cannelloni samples. Salmonella was isolated from 1.2% of smoked salmon samples, 1.5% of frozen chicken croquettes, 2% of cooked ham samples, and 11.1% of cured dried sausage samples. Overall, occurrence of these pathogens in RTE foods was similar to that previously reported in the literature.     

Simultaneous detection of Listeria monocytogenes and Salmonella by multiplex PCR in cooked ham

A multiplex PCR (m-PCR) assay with an internal amplification control (IAC) was developed for the simultaneous detection of Salmonella spp. and Listeria monocytogenes through invA and prfA genes, respectively. To ensure the detection of the pathogens in cooked ham, samples were enriched in both buffered peptone-water and Half Fraser broth. Subsequently, equal volumes of enrichment broths were mixed and DNA purification was performed prior to m-PCR reaction, saving considerable time and effort. The m-PCR also proved to be very useful as a simple and ready-to-go method for simultaneous confirmation of presumptive L. monocytogenes and Salmonella spp. colonies directly from agar plates without any DNA extraction steps.     

Incidence and susceptibility to antimicrobial agents of Listeria spp. and Listeria monocytogenes isolated from poultry carcasses in Porto,Portugal

The occurrence of Listeria spp. and Listeria monocytogenes in 63 samples of Portuguese poultry carcasses obtained from two local butcher shops and one canteen in the city of Porto, Portugal, and the susceptibility of these bacteria to antimicrobial agents allowed for use in human or animal therapeutics were evaluated. All poultry samples were contaminated with Listeria spp., and L. monocytogenes was isolated from 41% (26 of 63) of the samples. Other Listeria species, including L. innocua, L. welshimeri, and L. seeligeri, were also isolated from poultry samples. A multiplex polymerase chain reaction method was used for the identification of all of the Listeria isolates; this method showed total conformity with the conventional method of biochemical identification and proved to be more reliable, faster, and less arduous. In addition, high percentages of Listeria spp. (84%) and L. monocytogenes (73%) isolates were found to be resistant to one or more antimicrobial agents of different groups, and 12 different resistance profiles were recorded. The frequency of the resistance of L. monocytogenes isolates to enrofloxacin and clindamycin is notable. The results of this study suggest a high incidence of L. monocytogenes on Portuguese poultry products available for consumers and indicate that poultry could be a potential vehicle of foodborne infections due to strains of L. monocytogenes that are resistant to antimicrobial agents.