单核细胞增生性李斯特菌的增殖和抑制

单核细胞增生性李斯特菌（Listeria Monocytogenes）引起的突发性中毒症是一种很特殊的食物中毒病症。阐述了单增李斯特菌的生长特性，包括营养需求、流行病学和溶血素O的一些研究，同时综述了影响李斯特菌增殖的因素，并介绍了一些对食品中单增李斯特菌的抑制方法。     

猪增生性肠炎的诊治

湘南某猪场1群仔猪爆发了一起以腹泻、拉酱油色稀粪，皮肤苍白为主的疫病，在200头仔猪中发病猪迭152头，发病率迭76％，死亡19头，死亡率占发病猪的12．5％。采取肌肉注射四环素和料中拌入支原净和金霉素治疗，效果良好．1周后疫病完全得到控制。     

猪增生性肠炎的诊治

湖南耒阳市某猪场暴发一起以腹泻、拉酱色稀粪、皮肤苍白为主的疫病,发病率为54.16%,死亡率为13%,经由肌肉注射四环素、林可霉素和料中拌入枝原净、金霉素等治疗,1周后疫病得到完全控制。     

猪增生性肠炎的诊治

湘南某猪场1群仔猪爆发了一起以腹泻、拉酱油色稀粪,皮肤苍白为主的疫病,在200头仔猪中发病猪达152头,发病率达76%,死亡19头,死亡率占发病猪的12.5%。采取肌肉注射四环素和料中拌入支原净和金霉素治疗,效果良好,1周后疫病完全得到控制。     

猪增生性肠炎的防治措施

猪增生性肠炎,又称为猪增生性肠病,是由胞内劳森菌感染引起的一种以保育猪或生长育肥猪出血性、顽固性或间歇性下痢,以回肠和结肠段黏膜呈腺瘤样增生为主要特征的肠道综合症。6²0周龄的生长育成猪较易感,虽然被感染猪死亡率仅有5%20周龄的生长育成猪较易感,虽然被感染猪死亡率仅有5%¹0%,但患猪饲料利用率比正常猪下降17%10%,但患猪饲料利用率比正常猪下降17%⁴0%,被迫淘汰率升高,养殖损失较大。主要有急性型、慢性型、亚临床型,通过流行病学、病原检查、血清检查、临床症状可以将其与一般下痢区分开。提高管理措施,严格引种,加强免疫,消毒,药物预防治疗等可以有效控制此病。早诊断早治疗至关重要。     

镉对鲫淋巴细胞的增殖抑制

镉(Cd2 )以1.25、2.50、3.75 mg/kg腹腔注射染鲫后,用3H-胸腺嘧啶脱氧核苷掺入法(3H-TdR法)和四甲基偶氮唑盐微量酶反应比色法(MTF法)检测鲫淋巴细胞的增殖.结果显示:0～14 d时,1.25 mg/kg组与对照组之间的放射性活度、吸光度均无显著差异;5～10 d时,2.50及3.75 mg/kg组与对照组之间的放射性活度、吸光度差异有显著性,表现为Cd2 浓度愈高,放射性活度及吸光度愈低;10～14 d时,除了3.75 mg/kg组外,其余组放射性活度、吸光度差异均无显著性,并且3.75 mg/kg组与对照组之间的放射性活度、吸光度差异也已缩小.因此低浓度Cd2 不影响鲫淋巴细胞的增殖,高浓度镉则能诱导鲫淋巴细胞增殖抑制.     

猪增生性肠炎的综合防治措施

猪增生性肠炎是指胞内劳森菌侵害生猪,造成回肠、结肠隐窝内肠上皮细胞发生腺瘤样增生的一种肠道传染病。该病会造成生猪生长发育不良、饲料利用率低下,导致出栏时间延迟,严重危害生猪养殖业的健康发展。介绍了猪增生性肠炎的病原学、发病机制、流行病学、临床症状、诊断方法以及综合防治措施,以期为临床上防治该病提供参考。     

猪增生性肠病的诊断与防治

<正>猪增生性肠病(PPE),又称猪增生性肠炎、猪回肠炎(Porcine Ileitis)、猪增生性肠道病、猪肠腺瘤样病、猪增生性出血性肠炎,但目前普遍称之为猪增生性肠病。猪增生性肠病是猪的一种     

猪增生性回肠炎的诊断与防治

<正>猪增生性肠炎是由一种厌氧菌—细胞内劳森氏菌引起的一种接触性传染病,常发生于6～20周龄的生长育成猪,也发生于母猪,被感染的猪群死亡率虽然不高,仅有5%～10%,但由于患     

疑似猪增生性肠炎的诊治

猪增生性肠炎（PPE）是由一种被称为细胞内罗松菌（Lawsonia intracellularis．又译为劳索尼亚氏细胞内寄生菌）的细菌引起的猪的一种常见综合征。不同的文献中又有不同的名称．如坏死性肠炎、增生性出血性肠病、回肠炎、局域性肠炎以及肠腺瘸病等。临床特征表现为间歇性下痢。贫血．皮肤苍白，生长缓慢。本病剖检特征是小肠及回肠粘膜增厚、出血或坏死等。现将一起疑似猪增生性肠炎病例诊治情况介绍如下．     

Pasteurizing Cold Smoked Salmon (Oncorhynchus nerka): Thermal Inactivation Kinetics of Listeria monocytogenes and Listeria innocua

Listeria monocytogenes results in potential food safety concerns in ready-to-eat refrigerated products. Cold-smoked salmon is a food considered to be at high risk for Listeria spp. contamination for which a mild heat treatment or pasteurization step might be helpful to reduce microbial levels. Cold-smoked salmon was inoculated with a cocktail of four strains (L. monocytogenes: ATCC19114, 7644, and 19113, and L. innocua: ATCC51742) and inactivation curves obtained at 58, 60, 62, 64, and 66°C using capillary tube methods. Inactivation results showed typical log linear trends (R² ≥ 0.97). D-values of L. monocytogenes and L. innocua were 0.3 to 14.1 min at 66 to 58°C, with a z-value of 5.2 to 6.5°C and activation energy of 332 to 414 kJ/mol. The nonpathogenic Listeria innocua ATCC51742 had comparable D- and z-values to the three strains of L. monocytogenes and thus can be used for validation of pasteurization processes to control L. monocytogenes in cold-smoked salmon and potentially other ready-to-eat thermolabile food products.     

Incidence,Growth, and Inactivation of Listeria monocytogenes in Cooked and Peeled Cold-Water Shrimp

ABSTRACT

Cooked and peeled cold-water shrimp (Pandalus jordani) naturally contaminated with Listeria monocytogenes were obtained from a processor for a series of studies to determine the level of contamination and growth characteristics of this bacterium in the naturally contaminated product. L. monocytogenes was isolated from every 25-g sample of individually quick frozen (IQF) shrimp that was tested. The level of contamination in each composite sample ranged from 5 to 16 colony forming units (CFU) per 25 g. When individual shrimp taken from the 25-g sample portions were tested separately, samples positive for L. monocytogenes ranged from 1 of 12 to 5 of 15 shrimp tested. The project also evaluated the effectiveness of three methods to inactivate the bacterium: ozone, chlorine dioxide, and steam as possible product reconditioning strategies. Ozone and chlorine dioxide were both found to be ineffective reconditioning treatments for shrimp naturally contaminated with L. monocytogenes. Experiments with steam conducted at the laboratory and later at the shrimp processing plant verified that shrimp contaminated with L. monocytogenes could be safely reconditioned by steam pasteurization. Steam was used successfully to pasteurize several thousand pounds of contaminated shrimp in the processing plant. When the naturally contaminated product was packaged in either oxygen-permeable or impermeable films and stored at 5°C and 10°C, the product was deemed spoiled by sensory evaluation after 9 days of storage, at which time the L. monocytogenes population were 3 × 10⁴ CFU per g. By comparison, when an isolate (strain 4311) from naturally contaminated shrimp was inoculated onto the pasteurized shrimp at a concentration of 12 cells /25g, the L. monocytogenes population reached 3.0 × 10⁸ per g after 9 days of storage. The pasteurization process used in this study would not be effective in inactivation of Clostridium botulinum. Ready-to-eat-shrimp must therefore be stored below 3°C or frozen.     

Possible In-Plant Sources of Contamination of Lobster and Snow Crab by Listeria

Abstract

The present study was undertaken to determine potential sources of Listeria monocytogenes contamination through statistical analysis of L. monocytogenes results from lobster and snow crab samples and Listeria spp. results from environmental swabs. The objectives were (1) to compare crustacean analysis records for relationships between presence/absence of L. monocytogenes and crustacean species, year, total aerobes, staphylococci and fecal coli-form; and (2) to identify sites prone to Listeria spp. contamination. There were no significant differences in L. monocytogenes incidence between lobster and snow crab nor between five consecutive years of survey. Total aerobes and staphylococci counts were significantly associated with incidence of L. monocytogenes; fecal coliform counts were not. On surfaces in contact with the processed product, Listeria spp. were mostly found within crab crushers, drum meat separators, shucking machines, on aprons, gloves, work tables and knives. Higher incidence of Listeria spp. were found on surfaces not in direct contact with the processed product such as truck boxes, foot stools, floors, drains and employee boots and pants.     

利斯特氏病原菌在水产品中的传播

近年,欧洲和北美已多次发生由利斯特氏菌引起爆发性传染病,该菌现已列为食品检查标准中的一种重要病原菌,它多由环境污染引起,具有抗热性和耐冷性,煮沸,冷藏仍能存活,介绍了它的生态环境,传播规律,鉴别方法和预防措施,认为煮沸－冷冻－融化过程为利斯特氏菌的致死过程。     

Antimicrobial Activity of 1% Cetylpyridinium Chloride Against Listeria spp. on Fish

Cetylpyridinium chloride (CPC) was evaluated as an antimicrobial against Listeria monocytogenes (LM) and Listeria innocua (LI) on fish. LI and LM showed the same reduction profile and the same minimum inhibitory and bactericidal concentrations. When CPC was applied to a diced fish matrix, reductions of 3.17–3.26 and 3.07–3.19 log were determined for LI and LM, respectively. Antimicrobial activity of CPC against LI resulted in initial reductions of 2.8–3.1 log in fresh fish fillets, 0.9–1.1 log in smoked fish fillets, and 3.2–3.4 log on fish skin. Effectiveness of CPC against total plate counts on fish skin showed reductions of 2.4–2.9 log.     

Effects of Potassium Lactate and Acetate on Listeria monocytogenes Inhibition,Physicochemical and Sensory Properties of Smoked Catfish Fillets

The objective of this study was to evaluate the effects of liquid and wood smoking with a potassium lactate (PL) and acetate (PA) combination on the quality and inhibition of L. monocytogenes growth in ready-to-eat (RTE) smoked catfish fillets. Catfish fillets were tumbled with PL and PA, and treated with no smoke (NS), wood smoke (WS), liquid smoke 1 (LS1), and liquid smoke 2 (LS2). Wood smoke with antimicrobials (WSWA) showed greater inhibition (p < 0.05) of L. monocytogenes growth than other treatments with the exception of the LS1 treatment with antimicrobials. Consumers preferred (p < 0.05) smoked catfish fillets treated with WS to LS1 with respect to appearance, odor, flavor, texture, and overall acceptability. In conclusion, the use of PL and PA did not have a negative impact on the quality and sensory properties of smoked catfish fillets but had a synergistic effect with wood smoke constituents that inhibited the growth of L. monocytogenes.     

Edible Corn‐zein‐based Coating Incorporated with Nisin or Lemongrass Essential Oil Inhibits Listeria monocytogenes on Cultured Hybrid Striped Bass,Morone chrysops × Morone saxatilis,Fillets During Refrigerated and Frozen Storage

Listeria monocytogenes presents a serious threat to consumer safety because it is resistant to various food storage techniques, including reduced or modified atmosphere packaging, refrigerated storage, and increased salt concentration. Edible coatings incorporated with natural antimicrobials have been suggested to control pathogenic and spoilage bacteria on a variety of meat products. In this study, edible zein‐based coatings incorporated with nisin and lemongrass essential oil (LGEO; 8%) were evaluated for antibacterial action against L. monocytogenes and spoilage organisms on fresh, cultured hybrid striped bass, Morone saxatilis × Morone chrysops, under two storage conditions (refrigerated or frozen) and two packaging types (polyvinyl chloride [PVC] and vacuum packing) over time. Corn‐zein‐based edible coatings were found to be an effective carrier for nisin and LGEO. Fillets coated with nisin showed the largest decrease in L. monocytogenes cell counts in both PVC and vacuum‐packaged samples in both refrigerated and frozen product, while fillets coated with LGEO showed intermediate inhibition of L. monocytogenes cell counts, with the strongest LGEO antibacterial effect being found in frozen product regardless of packaging. Both nisin and LGEO treatments were most effective in PVC‐packaged fillets compared to vacuum‐packaged fillets, but the difference in bacterial loads between packaging methods was minor. Bacterial loads on refrigerated product tended to increase slightly after 5‐d storage regardless of coating treatment or packaging, whereas bacterial loads on frozen product remained stable or decreased with time up to 60 d regardless of coating treatment or packaging. Data from the present study indicate that application of edible coatings incorporated with essential oils not only promotes food product safety but also may satisfy the preferences of consumers.     

Effect of Trisodium Phosphate or Water Dip on the Survival of Salmonella and Listeria monocytogenes Inoculated Catfish Before and After Freezing

Salmonella and Listeria monocytogenes (LM) are occasional contaminants on raw fish. Catfish fillets were artificially contaminated with LM and Salmonella, dipped in a 1.5 % (30 min) trisodium phosphate solution (TSP), and cryogenically frozen. After 3 months frozen storage, Salmonella (2 log), but not LM, was inactivated on the fillets treated with the dip. This indicates that TSP dip followed by cryogenic freezing can be used to control Salmonella, but not LM, on catfish fillets.     

Prevalence and serotyping of Listeria monocytogenes in Portuguese live bivalve molluscs sampled in various steps along the sanitary control process

The prevalence and contamination levels of Listeria monocytogenes were investigated in live bivalve molluscs for human consumption, collected in various steps of the commercial and sanitary circuits in the North of Portugal. Samples of different species were collected per lot before and after depuration treatment in two depuration units and further, when placed in retail markets. Listeria monocytogenes was isolated from 4% of the samples although with very low contamination levels (less than 100 MPN g^?1). None of the environmental (non‐depurated) samples were contaminated with the food‐borne pathogen. The positive samples involved depurated and commercialized samples from two lots, one in each circuit. Two serotypes (1/2a and 3b) were detected among the isolated strains. This study demonstrated the possibility of occurrence of L. monocytogenes contamination of live bivalve molluscs along the sanitary control circuit, including at the retail market level. As L. monocytogenes grows well at refrigerated temperatures and in high salt matrixes such as seafood its presence in these products should not be overlooked.