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31.
有关猪肺炎支原体感染诊断方法和流行病学的最新观点 总被引：1，自引：0，他引：1
猪肺炎支原体是猪地方性肺炎(Enzootic Pneumonia,EP)的主要病原体,本病是一种主要影响肥育猪的慢性呼吸道疾病.尽管人们在控制猪肺炎支原体感染及其带来的不利影响上花费了大量的精力,但是猪地方性肺炎仍继续给全球养猪生产造成重大的经济损失.猪肺炎支原体通常是通过引进亚临床型感染的动物而侵入猪群的,或通过短距离的空气传播发生感染,但后一种情况较少.一旦侵入猪群,猪肺炎支原体可通过与受感染的母猪直接接触而将病原体传给后代或在同圈猪只之间进行传播.用于诊断猪肺炎支原体感染的"黄金标准"技术--细菌学培养非常费劲,通常很少使用.酶联免疫吸附试验和聚合酶链式反应检测方法以及以屠宰场监测或田间剖解为形式的死后检查,是用于调查猪肺炎支原体是否参与了猪呼吸道疾病的最常用技术.这些技术已被用来监测受猪地方性肺炎影响的猪群猪肺炎支原体的临床型和亚临床型感染猪群、免疫猪群或非免疫猪群以及处于不同的生产条件和管理条件下的猪群的发生情况.猪场水平上的猪地方性肺炎临床过程差异以及猪肺炎支原体疫苗接种效果的差异表明,猪肺炎支原体的不同田间分离株的传播和毒力特性存在差异.本文综述了猪肺炎支原体感染的流行病学最新知识,包括其传播、感染和血清转化动力学,并且还比较了用来监测猪地方性肺炎的各种流行病学方法. 相似文献
32.
Characterization of the in vitro adhesion of Actinobacillus pleuropneumoniae to swine alveolar epithelial cells 总被引：5，自引：0，他引：5
Van Overbeke I Chiers K Charlier G Vandenberghe I Van Beeumen J Ducatelle R Haesebrouck F 《Veterinary microbiology》2002,88(1):59-74
Actinobacillus pleuropneumoniae biovar 1 serotypes 2, 5a, 9 and 10 strains were tested for their ability to adhere to alveolar epithelial cells in culture. For the serotypes 5a, 9 and 10 strains, optimal adherence was observed after growth of bacterial cells in a NAD-restricted medium (0.001% NAD). This condition was also associated with the expression of a 55 kDa outer membrane protein (OMP) and of fimbriae. For the serotype 2 strain, adherence and expression of fimbriae and a 55 kDa OMP was less influenced by the growth conditions. The N-terminal amino acid sequence of the 55 kDa OMP had no homology with any known sequence, suggesting that it is an as yet unknown protein. Adherence capabilities were significantly reduced following treatment of the bacteria with proteolytic enzymes or heat. These findings suggest that proteins are involved in adhesion. The hydrophobic bond-breaking agent tetramethylurea was unable to inhibit the adherence of A. pleuropneumoniae to alveolar epithelial cells. Treatment of the bacteria with sodium metaperiodate resulted in lower adhesion scores for the serotypes 2 and 9 strains but the inhibition of adhesion was clearly lower than after treatment with proteolytic enzymes. This indicates that, besides proteins, carbohydrates might also be involved in adhesion of A. pleuropneumoniae to alveolar epithelial cells. The finding that inhibition of adhesion was very high when bacteria were treated with a combination of sodium metaperiodate and pronase also suggests that more than one adhesin is involved. 相似文献
33.
Boyen F Pasmans F Van Immerseel F Morgan E Botteldoorn N Heyndrickx M Volf J Favoreel H Hernalsteens JP Ducatelle R Haesebrouck F 《Veterinary microbiology》2008,128(3-4):364-373
Virulence genes regulated by the SsrA/B system are indispensable for systemic disease in BALB/c mice. The role of this regulating system in the pathogenesis of Salmonella Typhimurium infections in pigs is not documented. In the present study, the interactions of Salmonella Typhimurium and an ssrA/B mutant were compared in vitro and in vivo. The ssrA/B mutant strain displayed decreased Salmonella Pathogenicity Island 2 (SPI-2) expression levels, showed a replication defect in mouse macrophages and was attenuated in a mouse model after oral inoculation. Using real time qRT-PCR and a porcine ileal loop model, it was shown that the ssrA/B mutant strain was not significantly attenuated in overall virulence and SPI-1 expression in specific. Flowcytometric analysis demonstrated that the ssrA/B mutant strain was defective in intracellular replication in porcine macrophages. After oral inoculation of piglets with the wild type strain or the ssrA/B mutant strain, the animals of both groups excreted Salmonella and were colonized by Salmonella to the same extent. In an intravenous mixed infection model, the ssrA/B mutant strain was defective in the colonization of several internal organs. These results suggest that the ssrA/B gene of Salmonella Typhimurium plays a limited role in the persistent intestinal colonization of pigs. 相似文献
34.
Van Deun K Pasmans F Ducatelle R Flahou B Vissenberg K Martel A Van den Broeck W Van Immerseel F Haesebrouck F 《Veterinary microbiology》2008,130(3-4):285-297
Although poultry meat is now recognized as the main source of Campylobacter jejuni gastroenteritis, little is known about the strategy used by the bacterium to colonize the chicken intestinal tract. In this study, the mechanism of C. jejuni colonization in chickens was studied using four human and four poultry isolates of C. jejuni. The C. jejuni strains were able to invade chicken primary cecal epithelial crypt cells in a predominantly microtubule-dependent way (five out of eight strains). Invasion of cecal epithelial cells was not accompanied by necrosis or apoptosis in the cell cultures, nor by intestinal inflammation in a cecal loop model. C. jejuni from human origin displayed a similar invasive profile compared to the poultry isolates. Invasiveness of the strains in vitro correlated with the magnitude of spleen colonization in C. jejuni inoculated chicks. The C. jejuni bacteria that invaded the epithelial cells were not able to proliferate intracellularly, but quickly evaded from the cells. In contrast, the C. jejuni strains were capable of replication in chicken intestinal mucus. These findings suggest a novel colonization mechanism by escaping rapid mucosal clearance through short-term epithelial invasion and evasion, combined with fast replication in the mucus. 相似文献
35.
Quantification of the spread of Mycoplasma hyopneumoniae in nursery pigs using transmission experiments 总被引：1，自引：0，他引：1
Meyns T Maes D Dewulf J Vicca J Haesebrouck F de Kruif A 《Preventive veterinary medicine》2004,66(1-4):265-275
Mycoplasma hyopneumoniae (M. hyopneumoniae) is present in almost all swine herds worldwide, but transmission of the pathogen through herds is not yet fully clarified. The aim of this study, performed in 2003, was to investigate and to quantify the transmission of M. hyopneumoniae under experimental conditions by means of an adjusted reproduction ratio (Rn). This Rn-value, calculated according to the final size method, expresses the mean number of secondary infections due to one typical infectious piglet during the nursery period. The period lasted from 4 to 10 weeks of age, corresponding with the nursery period used in most European production systems. Additionally, a comparison was made between transmissions of highly virulent and low virulent isolates.
Forty-eight weaned piglets, free of M. hyopneumoniae, were housed in six separate pens. During 6 weeks, two animals experimentally infected with M. hyopneumoniae were housed together with six susceptible piglets. At the end of the study, the number of contact-infected animals was determined by the use of nPCR on bronchoalveolar lavage fluid. The Rn-values of the highly virulent and the low virulent isolates were estimated to be 1.47 (0.68–5.38) and 0.85 (0.33–3.39), respectively. No significant difference between the groups was found (P = 0.53). The overall Rn was estimated to be 1.16 (0.94–4.08). Under the present experimental conditions, the transmission of M. hyopneumoniae, assessed for the first time by a reproduction ratio, shows that one piglet infected before weaning will infect on average one penmate during the nursery phase. 相似文献
36.
Leen Timbermont Lina De Smet Filip Van Nieuwerburgh Valeria R Parreira Gonzalez Van Driessche Freddy Haesebrouck Richard Ducatelle John Prescott Dieter Deforce Bart Devreese Filip Van Immerseel 《Veterinary research》2014,45(1):40
Necrotic enteritis in broiler chickens is associated with netB positive Clostridium perfringens type A strains. It is known that C. perfringens strains isolated from outbreaks of necrotic enteritis are more capable of secreting factors inhibiting growth of other C. perfringens strains than strains isolated from the gut of healthy chickens. This characteristic could lead to extensive and selective presence of a strain that contains the genetic make-up enabling to secrete toxins that cause gut lesions. This report describes the discovery, purification, characterization and recombinant expression of a novel bacteriocin, referred to as perfrin, produced by a necrotic enteritis-associated netB-positive C. perfringens strain. Perfrin is a 11.5 kDa C-terminal fragment of a 22.9 kDa protein and showed no sequence homology to any currently known bacteriocin. The 11.5 kDa fragment can be cloned into Escherichia coli, and expression yielded an active peptide. PCR detection of the gene showed its presence in 10 netB-positive C. perfringens strains of broiler origin, and not in other C. perfringens strains tested (isolated from broilers, cattle, sheep, pigs, and humans). Perfrin and NetB are not located on the same genetic element since NetB is plasmid-encoded and perfrin is not. The bacteriocin has bactericidal activity over a wide pH-range but is thermolabile and sensitive to proteolytic digestion (trypsin, proteinase K). C. perfringens bacteriocins, such as perfrin, can be considered as an additional factor involved in the pathogenesis of necrotic enteritis in broilers. 相似文献
37.
González-Agüero M Cifuentes-Esquivel N Ibañez-Carrasco F Gudenschwager O Campos-Vargas R Defilippi BG 《Journal of agricultural and food chemistry》2011,59(24):13295-13299
Cherimoyas (Annona cherimola), like other subtropical/tropical fruits, are susceptible to damage from exposure to temperatures between 0 and 5 °C (chilling injury, CI), which may affect fruit quality. To increase our understanding of the molecular mechanisms involved in the CI response, a forward suppression subtractive hybridization (SSH) cDNA library was constructed. In this work, we obtained 75 genes that could potentially be involved in the CI response. The CI induced activation of genes that are involved in a range of metabolic pathways, such as primary metabolism, transport, and endomembrane traffic, among others. We also characterized the expression of 12 selected genes in different A. cherimola tissues by polymerase chain reaction (PCR), and we confirmed the differential expression of a subset in CI fruits by real-time quantitative PCR (qPCR). The expression of six A. cherimola genes: annexin (AcAnex), UDP-glucose pyrophosphorylase (AcUGP), syntaxin of plants 71 (AcSyp71), 1-aminocyclopropane-1-carboxylic-acid synthase (AcACS), ubiquitin carrier-like protein (AcUCP), and enolase (AcEnol), was up-regulated after cold storage for 12 days at 0 °C. These results imply that selected genes could be related to the development of internal browning observed in cherimoyas after exposure to CI conditions. The information generated in this study provides new clues that may aid in understanding the cherimoya ripening process. 相似文献
38.
Tom Meyns Jan Van Steelant Emily Rolly Jeroen Dewulf Freddy Haesebrouck Dominiek Maes 《Veterinary journal (London, England : 1997)》2011,187(3):388-392
A cross-sectional study was conducted to identify herd-level factors that may influence the prevalence and severity of macroscopically visible pulmonary lesions in pigs at slaughter. Data were collected following abattoir inspection of 50 randomly-selected batches of 6335 pigs and by interviewing the producers. Macroscopic lung lesions were identified and scored semi-quantitatively in ?80 pigs/herd and the prevalence of pleuritis and pneumonia was 20.76% and 23.85%, respectively. Following multivariable analysis, the seroprevalence of Actinobacillus pleuropneumoniae (P < 0.001) and Mycoplasma hyopneumoniae (P = 0.018) and the number of pigs/nursery pen (P = 0.023) were positively associated, whereas average weaning age was negatively associated (P = 0.001) with the pleuritis score. Risk factors associated with a higher prevalence of pneumonia were the presence of pleuritis (P = 0.001) and the frequent purchasing of pigs (P = 0.020). The findings of this study indicate that the prevalence of pleuritis and pneumonia remains high in Belgium and management factors are central to disease control. 相似文献
39.
Chiers K Donné E Van Overbeke I Ducatelle R Haesebrouck F 《Veterinary microbiology》2002,85(4):343-352
Many farrow-to-finish herds are endemically infected with Actinobacillus pleuropneumoniae. In order to control the disease efficiently, a better knowledge of the ages at which pigs become infected is necessary. Furthermore, no information is available concerning the influence of maternally derived antibodies on the colonization of the upper respiratory tract. Therefore, A. pleuropneumoniae infection patterns were studied in five farrow-to-finish pig herds (A-E) with a history of pleuropneumonia. A longitudinal study was carried out in herds A and B. In these herds, piglets from sows carrying A. pleuropneumoniae in their noses or tonsils were sampled. Nasal and tonsillar swabs as well as sera, were collected from these animals at the age of 4, 8, 12, 16 (herds A and B) and 23 weeks (herd B). At these ages other pigs from the same sows were euthanized. The lungs were macroscopically examined and samples from nose, tonsils and lungs were collected at necropsy. A cross-sectional study was performed in herds C-E. In these herds nasal and tonsillar swabs, as well as sera, were taken from 10 animals of 4, 8, 12 and 16 weeks of age. Lung, nasal and tonsillar samples were tested for the presence of A. pleuropneumoniae by routine bacteriology and PCR with mixed bacterial cultures. The sera were examined for the presence of Apx toxin neutralizing antibodies. In herd A, A. pleuropneumoniae serotype 2 and 10 strains were isolated, whereas serotype 2, 3, 5b and 8 strains were demonstrated in herd B. In most herds, A. pleuropneumoniae was detected in mixed bacterial cultures of tonsillar and/or nasal samples by PCR from the age of 4 weeks onwards. Colonization of the lungs and development of lung lesions was observed in 12- and 16-week-old animals of herd A and 23-week-old animals of herd B. In most herds, high antibody titres were detected in 4-week-old piglets. These titres decreased during the first 12 weeks of age, but thereafter, increased. It was concluded that PCR with mixed bacterial cultures from tonsillar swabs is a valuable tool for the detection of infected animals. It was also concluded that colonization of tonsils and nasal mucosae can occur in the presence of maternally derived antibodies. Infection of the upper respiratory tract without lung involvement did not result in development of Apx toxin neutralizing antibodies. Therefore, such serological assays cannot be used for the detection of subclinically infected animals. 相似文献
40.