Estimation of most probable number of Salmonella in retail samples of minced pork

The number of salmonellae in 174 samples of minced pork was determined by the Most Probable Number (MPN) method in two separate laboratories. The material examined was taken from a collection of samples which were Salmonella positive in an earlier study. The MPN estimation was carried out using portions of original samples which had been divided (2 x 100 g) before the initial examination and which had been deep frozen and stored for 1 to 14 weeks at -18 degrees C until re-examination. Of the 174 samples initially positive for Salmonella, 131 (75.3%) were positive on re-examination using pre-enrichment in buffered peptone water (BPW) and selective enrichment in Rappaport-Vassiliadis medium (RV) and in tetrathionate medium according to Muller-Kauffmann (MK). The majority of the samples gave Salmonella counts below 1000/100 g (96.7% at lab. A and 97.3% at lab. B). Comparison of the results from both laboratories showed good agreement in the distribution pattern of the frequencies within the MPN classes, but agreement between the same sample pair was poor (r = 0.23). RV medium proved to be superior to the MK medium.     

A risk characterization model of Salmonella Typhimurium in Irish fresh pork sausages

A second-order simulation model was built to estimate the risk of Salmonella Typhimurium associated with the consumption of Irish fresh pork sausages. To select appropriate hazard characterization models, an initial appraisal of the current dose-response models was conducted. The cooking modality of grilling was associated with a higher mean risk of infection per serving (1.399 × 10^? 6; 95% CI: 7.54 × 10^? 7–2.65 × 10^? 6) than frying (6.246 × 10^? 7, 95% CI: 2.78 × 10^? 7–1.17 × 10^? 6). When the risk was extrapolated over the consumption in a year period, the mean risk of infection increased considerably to 8.541 × 10^? 5 with an expected number of infections and illnesses of 184.3 (95% CI: 26–664) and 17 (95% CI: 2–63), respectively. Results highlighted the importance of consumer education, as scenario analysis predicted that, for the current level of Salmonella in pork sausage, decreasing the product's cold storage by approximately 8 h and cooking for an additional half minute can reduce the current risk level by ～ 50%.     

Prevalence and antimicrobial susceptibility of Salmonella isolated from a variety of raw meat sausages in Gaborone (Botswana) retail stores

The objective of the study was to provide baseline data on the prevalence and antimicrobial susceptibility of Salmonella in different types of raw meat sausages directly accessible to the consumers in Gaborone, Botswana. A total of 300 raw sausages comprising 79 beef, 78 pork, 72 chicken, and 71 mutton samples were concurrently analyzed for the presence of Salmonella using a conventional culture method and a validated PCR method. The PCR assay results were in full concordance with those of the conventional culture method for the detection of Salmonella. Sixty-five (21.7%) of 300 samples were positive for Salmonella by both the conventional culture method and PCR assay. Even though more chicken samples contained Salmonella than did any other sausage type, the difference in the presence of Salmonella among the four sausages types was not significant. Eleven serotypes were identified, and Salmonella enterica subsp. salamae II was most prevalent in all the sausage types. Beef sausages generally had higher mesophilic bacterial counts than did the other three sausage types. However, higher microbial counts were not reflective of the presence of salmonellae. Susceptibility of the Salmonella enterica serotypes to 20 antimicrobial agents was determined, and Salmonella Muenchen was resistant to the widest array of agents and was mostly isolated from chicken sausages. Regardless of the meat of origin, all 65 Salmonella isolates were resistant to at least four antimicrobial agents: amikacin, gentamicin, cefuroxime, and tombramycin. This resistance profile group was the most common in all four sausage types, comprising 90% of all Salmonella isolates from beef, 71% from pork, 63% from mutton, and 35% from chicken. These results suggest that raw sausages pose a risk of transmitting multidrug-resistant Salmonella isolates to consumers.     

Prevalence of Salmonella on raw poultry at retail markets in China

Data regarding Salmonella on raw poultry are very limited in China. The objective of this study was to determine the prevalence of Salmonella on raw poultry at the retail level in six provinces and two national cities in China. Whole chicken carcasses (n = 1,152) were collected from three types of retail markets (large, small, and wet). All samples were analyzed for the presence of Salmonella by using the U.S. Department of Agriculture, Food Safety Inspection Service method. Of 1,152 chicken samples, overall Salmonella prevalence was 52.2%. The highest prevalence was observed in Guangxi Province (65.3%), next in Guangdong Province (64.6%), and then in Beijing (63.9%), Shaanxi Province (50.7%), Henan Province (47.9%), Shanghai (44.4%), and Fujian Province (42.4%), and lowest prevalence was observed in Sichuan Province (38.9%). Salmonella prevalence was significantly different among the six provinces and two national cities. Salmonella prevalence was highest in the wet markets (54.4%) compared with the large markets (50.3%) and the small markets (52.1%), but differences were not significant (P > 0.05). Good manufacturing practices, good agricultural practices, and hazard analysis critical control point systems for Salmonella control in poultry production at the farm, processing, and retail level should be implemented.     

Prevalence of Salmonella on retail broiler chicken meat carcasses in Colombia

A cross-sectional study was performed to estimate the prevalence of Salmonella on retail market chicken carcasses in Colombia. A total of 1,003 broiler chicken carcasses from 23 departments (one city per department) were collected via a stratified sampling method. Carcass rinses were tested for the presence of Salmonella by conventional culture methods. Salmonella strains were isolated from 27 % of the carcasses sampled. Logistic regression analysis was used to determine potential risk factors for Salmonella contamination associated with the chicken production system (conventional versus free-range), storage condition (chilled versus frozen), retail store type (supermarket, independent, and wet market), poultry company (integrated company versus nonintegrated company), and socioeconomic stratum. Chickens from a nonintegrated poultry company were associated with a significantly (P < 0.05) greater risk of Salmonella contamination (odds ratio, 2.0) than were chickens from an integrated company. Chilled chickens had a significantly (P < 0.05) higher risk of Salmonella contamination (odds ratio, 4.3) than did frozen chicken carcasses.     

Prevalence and genotypes of Toxoplasma gondii in pork from retail meat stores in Eastern China

Pork is known as one of the most important sources of Toxoplasma gondii infection in China. In the present study, 416 fresh pork samples were collected from different locations of Anhui province, Eastern China. Tissue fluid ELISA was conducted to detect the antibodies to T. gondii. Real-time PCR and bioassay were performed to identify the presence of T. gondii DNA and viable parasites, respectively. Seventy-five out of 416 samples (18.03%) demonstrated real-time PCR positive reaction and 42 out of 416 samples (10.1%) showed tissue fluid ELISA positive reaction. One isolate (Tgpkfx171) was obtained through bioassay in mice from 14 samples that demonstrated both PCR and ELISA positive reaction. The isolate and seven positive DNA samples were genotyped using 9 PCR-RFLP markers including SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico. Among these, only the isolate and two positive DNA samples were genotyped with complete data for all loci, belonging to ToxoDB#9 (Chinese 1) and ToxoDB#213, respectively. This is the first report of the prevalence and genetic typing of T. gondii from pork in retail meat stores in China. The present results provide an accurate picture of the risk of exposure to T. gondii in retail pork in China.     

Antibiotic resistance profiles of Salmonella serovars isolated from retail pork and chicken meat in North Vietnam

The spread of antibiotic resistance via meat poses a serious public health concerns. During 2007-2009, a total of 586 retail meat samples (318 pork and 268 chicken meats) were collected from three provinces (Bac Ninh, Ha Noi and Ha Tay) of North Vietnam to determine the prevalence of Salmonella. Isolates were characterized by serotyping and antibiotic susceptibility testing. Approximately 39.6% (n=126) of pork and 42.9% (n=115) of chicken samples were Salmonella-positive, and 14 Salmonella serovars were identified. Anatum (15.8%) was the most common serovar, followed by Infantis (13.3%), Emek (10.4%), Derby and Rissen (9.5%), Typhimurium (9.1%), Reading (7.5%) and London (6.2%). The isolation frequency of serovars Enteritidis, Albany, Hadar, Weltevreden, Newport and Blockey ranged from 1.2%-5.8%. Resistance to at least one antibiotic agent was detected in 78.4% of isolates (n=189) and the most frequent resistance were to tetracycline (58.5%), sulphonamides (58.1%), streptomycin (47.3%), ampicillin (39.8%), chloramphenicol (37.3%), trimethoprim (34.0%) and nalidixic acid (27.8%). No Salmonella isolates were resistant to ceftazidime. Chicken isolates had higher resistance to antibiotic agents than pork isolates (P<0.05). It showed that 159 Salmonella isolates belong to the 14 serovars were multidrug resistant (MDR) and 50 MDR patterns were found. This study indicated that Salmonella serovars isolated from retail meat samples were resistant to multiple antibiotics and this resistance was widespread among different serovars. The widespread resistance may have arisen from misuse or overuse of antibiotics during animal husbandry in North Vietnam.     

Meat mixture detection in Iberian pork sausages

Five homogenized meat mixture treatments of Iberian (I) and/or Standard (S) pork were set up. Each treatment was analyzed by NIRS as a fresh product (N=75) and as dry-cured sausage (N=75). Spectra acquisition was carried out using DA 7000 equipment (Perten Instruments), obtaining a total of 750 spectra. Several absorption peaks and bands were selected as the most representative for homogenized dry-cured and fresh sausages. Discriminant analysis and mixture prediction equations were carried out based on the spectral data gathered. The best results using discriminant models were for fresh products, with 98.3% (calibration) and 60% (validation) correct classification. For dry-cured sausages 91.7% (calibration) and 80% (validation) of the samples were correctly classified. Models developed using mixture prediction equations showed SECV=4.7, r(2)=0.98 (calibration) and 73.3% of validation set were correctly classified for the fresh product. These values for dry-cured sausages were SECV=5.9, r(2)=0.99 (calibration) and 93.3% correctly classified for validation.     

低温猪肉火腿肠降盐工艺探究

为探究低温猪肉火腿肠的有效降盐工艺,在加工过程中,对腌制前的肉糜进行超高压处理,而后采用优化低盐腌制配方腌制,以感官评分、质构特性、肉糜乳化稳定性、色差、凝胶保水性、蒸煮损失及风味物质分析等为考察指标,确定降盐工艺参数。优化得到的工艺条件为:腌制前肉糜的超高压条件为200 MPa保压10 min,低盐腌制配方为0. 12%Na Cl,1%KCl,1%乳酸钾,1%抗坏血酸钙,0. 9%L-赖氨酸,0. 9%L-精氨酸,0. 25%生姜粉。该工艺中的低盐优化配方将产品中的钠含量降至118 mg/100 g,符合国标关于低盐声称的标准(≤120mg/100g),超高压处理有效促进低盐凝胶体系的构建,弥补低盐对产品品质的不良影响,2种工艺结合使用,使最终产品具有良好的品质。     

杨凌及周边地区零售分割鸡肉中沙门菌污染状况及耐药和分型特征研究

目的研究陕西杨凌及周边地区零售分割鸡肉中沙门菌的污染状况及其药敏性、血清型和基于脉冲场凝胶电泳(PFGE)的基因型,为预警食源性沙门菌疾病暴发提供数据基础。方法采用GB 4789.4—2010《食品安全国家标准食品微生物学检验沙门氏菌检验》对陕西杨凌及周边地区采集的188份零售分割鸡肉中沙门菌进行分离和鉴定,并进行血清学分型。采用PFGE方法确定沙门菌DNA酶切电泳图谱,使用BioNumerics软件聚类分析电泳结果,确定沙门菌基因型。结果 188份零售分割鸡肉中共有34份(18.1%)样品检出沙门菌,农贸市场样品沙门菌检出率(24.6%,29/118)高于超市(7.1%,5/70)。鸡腿、鸡爪、鸡脖和鸡肝样品中沙门菌检出率高于鸡肠和鸡胗。34株沙门菌中共检出10种血清型,其中科瓦利斯沙门菌最为流行,高于德尔卑沙门菌和鼠伤寒沙门菌等,差异有统计学意义(P0.05)。分离株均对磺胺异噁唑、氯霉素、头孢噻呋和环丙沙星耐药,对甲氧苄啶/磺胺甲噁唑、萘啶酮酸、四环素、链霉素、氨苄西林和阿莫西林/克拉维酸的耐药率均在50%以上。34株沙门菌PFGE分型后可被分为11个簇,同一血清型菌株基本聚于同一大簇,同一时间、从相同市场采集的不同样品,其分离株PFGE型相似度均较高,表明分割鸡肉在加工或销售过程可能存在交叉污染。农贸市场分离菌株基因型多样性比较丰富。结论杨凌及周边地区零售分割鸡肉存在沙门菌污染,沙门菌血清型和基因型多样化,耐药菌株比例较高。     

Prevalence, antibiotic resistance, and molecular characterization of Salmonella serovars in retail meat products

The prevalence of Salmonella was determined in chicken meat (n = 26), beef (n = 49), and pork (n = 56) collected from wholesale markets, retail stores, and traditional markets in Seoul, South Korea, in 2009. Antibiotic resistance was assessed, and the molecular subtypes of Salmonella isolates were ascertained using an automated repetitive sequence-based PCR (rep-PCR) system (DiversiLab). A total of 18 Salmonella strains were isolated from 17 of 131 samples: 16 strains from each of 16 samples and 2 strains from the same pork sample. The prevalence of Salmonella from the retail meats was 2.0% in beef, 8.9% in pork, and 42.3% in chicken meat. Among 10 different serotypes, Salmonella enterica Panama was recovered from a beef sample, and Salmonella London and Salmonella Montevideo were the predominant serotypes from pork and chicken meat, respectively. The highest antibiotic resistance observed was to erythromycin (100%) followed by streptomycin (22.2%) and tetracycline and chloramphenicol (16.7%). Of the 18 isolates, 5 (27.8%) were resistant to two or more antibiotics, and 1 isolate from chicken meat was resistant to eight antibiotics, including cephalosporins. Differentiation between all of the Salmonella isolates except between Salmonella Montevideo and Salmonella London was successfully performed with the automated rep-PCR system, indicating that it can be added to the toolbox for source tracking of foodborne pathogens associated with outbreaks.     

Prevalence of Campylobacter and Salmonella in raw chicken on retail sale in the republic of Ireland

To assess the current risks to consumers from Campylobacter and Salmonella in raw chicken products sold in the Republic of Ireland, a retail survey was undertaken to define their prevalence. Samples (n = 510) were analyzed using protocols based on ISO 10272-1:2006 and ISO 6579:2002. Processor codes on pack labels showed that 67% of samples were produced in the Republic of Ireland and 25% in the United Kingdom. Salmonella was present in 5.1% of samples, but the eight serovars found caused less than 7% of human salmonellosis reported in the Republic of Ireland. The results suggest that on-farm controls to limit Salmonella infection of broilers have been successful and that in Ireland raw chicken is not a significant cause of salmonellosis in humans. The overall prevalence of Campylobacter spp. was 84.3%. Isolation by the ISO method found 52.7% of samples to be positive, but overgrowth by contaminants was frequently evident. Therefore, in addition to enrichment, an homogenized sample was plated directly onto modified charcoal cefoperazone deoxycholate agar, and this detected a further 31.6%. Speciation of isolates (n = 426) determined that 67% were Campylobacter jejuni and 32% were Campylobacter coli. These species are the most common cause of campylobacteriosis in man. The results indicate that there is a need for poultry producers to introduce interventions to minimize the exposure of consumers in the Republic of Ireland to Campylobacter spp., as has been successfully done for Salmonella.     

Characterization of the Arcobacter contamination on Belgian pork carcasses and raw retail pork

In the present study, the occurrence of Arcobacter was assessed at four sites on 169 porcine carcasses (foreleg, chest, pelvis and ham) at different stages of slaughter and 47 pork products at retail. Carcass swab samples were enriched in Arcobacter broth containing 5-fluorouracil, amphotericine B, cefoperazone, novobiocine and trimethoprim as selective supplement. After microaerobic incubation, arcobacters were isolated using Arcobacter selective agar plates, containing the selective supplement described above. Some carcass samples and all pork samples were also examined quantitatively. All 862 isolates were identified by a species-specific m-PCR-assay and 182 isolates were further characterized by ERIC-PCR. Arcobacters were isolated from one or more sampling places on 96.4% of the carcasses, with the foreleg and the chest area as the two most contaminated sites. Furthermore, A. cryaerophilus was the most common species. Chilling decreased the number of positive carcasses, but did not eliminate all arcobacters. Direct isolation revealed that only a few carcasses were contaminated with arcobacters on foreleg and/or chest at levels higher than 10(2 )cfu/100 cm(2). Characterization demonstrated a large heterogeneity among the isolates, with ten genotypes present on more then one site per carcass. Fourteen genotypes were simultaneously present on carcasses from different herds slaughtered on the same day, which may indicate cross-contamination. Arcobacters were present in 21% of the pork samples taken at retail, but contamination levels did not exceed 100 cfu per gram. Characterization of the A. butzleri and A. cryaerophilus isolates indicated an additional contamination during processing at retail.     

Prevalence of Salmonella spp. and Listeria monocytogenes at small-scale spanish factories producing traditional fermented sausages

The manufacturing of fermented sausages is subject to natural contamination processes that can potentially carry foodborne pathogens along the process chain and result in contamination of the final product. The aim of this study was to evaluate the occurrence of Salmonella spp. and Listeria monocytogenes at different sampling points during the manufacturing process of fuet, a type of traditional fermented sausage, at 10 small-scale Spanish factories. The presence of both pathogens was studied in the raw materials (19 casings and 19 meat batters), the final products (19 fermented sausages), and the factory equipment (12 mincing, 12 mixing, and 19 stuffing machines, 19 cutting tables, 11 knives, and 12 cold rooms) by using classical microbiological techniques and real-time PCR. Salmonella was not detected in the equipment analyzed or in the final products, but it was detected in the raw materials (23.7% of samples). L. monocytogenes showed higher incidence than Salmonella and was detected in the equipment (11.8% of samples), the raw materials (28.9%), and the final products (15.8%), confirming its ubiquity throughout the manufacturing process of fermented sausages. Five factories were further investigated to study the changes in the distribution of pathogens in the fuet production process over a period of either 2 or 3 years. There was considerable variation in the incidence of both pathogens at different sampling periods, and there was no relation between seasonal variations or geographic location of the factories.     

Centralized bulk pre-packaging of pork retail cuts

The performance of a commercial bulk pre-packaging system was compared to a laboratory system in terms of quality attributes such as microbiology, colour, odour, and acceptability of PVC-overwrapped pork retail cuts. A similar retail shelf life of 3 days was achieved after either 0, 7, or 14 days bulk storage with both packaging systems. The colour of the samples from both systems was pale to normal during the trial. After 14 days storage the samples from both systems were still acceptable and had a fresh meat odour. The results show that the commercial system (Cryovac GFII, Darex Africa (Pty) Ltd, Kemptonpark RSA) may be applied successfully for 100% CO₂ bulk packaging of PVC-overwrapped pork retail cuts.     

Quality characteristics of Chinese sausages made from PSE pork

Chinese sausages made from normal and different levels of PSE pork (100% Normal, 50%Normal+50% PSE and 100% PSE) were vacuum-packaged and stored at 4 °C for 45 days. The composition, processing yield, pH value, thiobarbituric acid (TBA) value, water activity, lactic acid bacteria counts and sensory properties of the meat products were evaluated. PSE pork loins had lower pH value, water holding capacity, moisture, fat and myofibrillar proteins content, but higher L^* value, drip loss and protein content than normal pork. Sausages made from 100% PSE pork had lower pH value, processing yield, moisture and fat content, but higher protein content than those of the 100% Normal and the 50% Normal+50% PSE treatments. Water activity was higher in the 100% PSE treatment than in other treatments. No differences in lactic acid bacterial counts among these treatments were observed. The pH values and water activity of the meat samples decreased, while lactic acid bacterial counts increased with storage time. TBA values among these treatments were not significantly different; however, the increase% of TBA values was higher for the 100% PSE treatment. TBA values of all treatments remained relatively low during storage. Chinese sausages made with 50–100% PSE pork had lower sensory texture, flavor and overall acceptability scores than the control samples, but were of acceptable quality.     

海藻酸钠-钙作为猪背膘替代物在萨拉米发酵香肠中的应用

以市售萨拉米发酵香肠为对照组,考察了海藻酸钠-钙盐作为猪背膘替代物分别以30％、50％、70％的比例替代猪背膘对发酵香肠含水量、pH、脂肪含量、重量损失、质构、色泽、风味以及感官品质的影响.结果表明:随着替代率的增加,香肠含水量增加;pH降低(70％除外);脂肪含量降低;重量损失增加;硬度和咀嚼性降低,弹性和内聚性变化不明显(70％除外);色差值△E增大;由香辛料产生的挥发性物质相对含量增加,由脂肪氧化或分解产生的挥发性物质减少,但总体差异性不明显;感官评价得分降低,但在总体可接受性上,替代组香肠都能引起人们较强的食欲.最终得出猪背膘最佳替代率为50％及以下比率.     

生猪肉中沙门氏菌的分离与鉴定

目的建立一套高效的沙门氏菌分离和鉴定方法,同时对本地区生猪肉中沙门氏菌的污染情况做初步评估。方法分别从本地区屠宰场、农贸市场和超市各采集10份生猪肉样品,共计30份。然后对采集的样品进行选择性培养,初步筛选疑似菌株,通过对疑似菌株进一步进行生理生化鉴定、16S rDNA基因序列的比对并构建系统发育树,最终确认沙门氏菌。结果研究表明在采集的30份样品中共获得1株疑似菌株,并通过一系列试验鉴定为沙门氏菌,同时表明该地区生猪肉中沙门氏菌的检出率为3.3%。结论该研究为丰富沙门氏菌数据库资料和流行病学的研究提供一定的理论依据,同时为进一步对该地区肉及肉制品中沙门氏菌的风险评估奠定基础。