Genetic analysis of pathogen-specific intramammary infections in dairy cows

Mastitis is one of the most common diseases in dairy cattle, causing severe economic losses to dairy farmers. Mastitis usually occurs due to intramammary infection (IMI) caused by a variety of pathogenic bacteria. Although good progress has been made in understanding genetics of pathogen-specific clinical mastitis, studies involving genetic analysis of pathogen-specific IMI are scarce. The overall objective of this study was, therefore, to assess genetic variation of overall and pathogen-specific IMI in nonclinical primiparous and multiparous cows using bacterial culture. Data and milk samples were collected over a 2-yr interval as part of the Canadian Bovine Mastitis Research Network. The final data set contained records of 46,900 quarter milk samples from 3,382 clinically healthy primiparous and multiparous Holstein cows from 84 dairy herds. For the genetic analysis, we considered the following 7 traits: overall IMI, non-aureus staphylococci (NAS) IMI, contagious pathogen IMI, environmental pathogen IMI, major pathogen IMI, minor pathogen IMI and somatic cell score (SCS). Data were analyzed at the quarter level using a threshold-probit model via Gibbs sampling in BLUPF90. Prevalence of IMI traits at the quarter level in multiparous cow from 0 to 400 DIM ranged from 6.8 to 45.5%. Posterior mean of quarter heritability estimates (on the underlying scale, posterior SD in brackets) of overall IMI and pathogen-specific IMI traits ranged from 0.017 to 0.073 (±0.009 to 0.030). Weak to strong genetic correlations [ranging from 0.18 to 0.97 (±0.01 to 0.29)] among pathogen-specific IMI traits and with overall IMI indicated that not all of these traits were genetically similar. Weak to moderate Spearman rank correlations between estimated breeding values for overall IMI and pathogen-specific IMI traits (from 0.31 to 0.87) indicated possible substantial reranking of sires. The percentage of daughters with IMI caused by various pathogen groups ranged from 13 to 80% and from 38 to 94% for the best (10% decile) and worst sires (90% decile) according to their IMI trait-specific estimated breeding values, respectively. Pathogen-specific IMI traits and overall IMI had weak to moderate positive genetic correlations [ranging from 0.11 to 0.81 (±0.11 to 0.22)] with SCS. Therefore, selection for lower SCS will improve resistance to IMI. However, based on the observed weak to moderate rank correlations (0.04 to 0.47) between pathogen-specific IMI traits and SCS, selection for lower SCC will not improve resistance to IMI from every pathogen-specific IMI group in the same manner. Therefore, despite low heritability estimates, there was sizeable genetic variation for pathogen-specific IMI traits, indicating that long-term direct genetic selection for pathogen-specific IMI can improve pathogen-specific IMI resistance.     

基于随机森林算法的食源性致病菌拉曼光谱识别

药品食品的安全问题一直是人们关注的重点。相比于传统的食源性致病菌光谱检测方法,拉曼光谱法具有检测范围广、检测灵活、光谱特征突出等特点。本文以常见的食源性致病菌为研究对象,利用拉曼光谱仪采集了11种食源性致病菌样品的132个拉曼光谱数据,提出了一种基于主成分分析和随机森林算法的分类模型。实验结果表明,主成分分析结合随机森林算法的分类模型可以将食源性致病菌区分开,且分类准确度可达到91.36%。     

自然发酵黄豆酱的微生物安全性的分析

对从11份农家和7份市场上销售的自然发酵黄豆酱样品进行了微生物的安全性检验和部分理化指标的测定,检验的项目包括细菌落总数、芽孢杆菌总数、大肠杆菌、沙门氏菌、志贺氏菌、腊样芽孢杆菌、金黄色葡萄球菌和肉毒梭菌。实验结果表明,所分析样品中菌落总数超过10^4个/g的样品有89％,腊样芽孢杆菌的检出率为30％,但含量不高,豆酱中的细菌总数除了与生产环境有关外,与产品的水分活度的相关性很大。     

The detection of foodborne pathogens by the polymerase chain reaction (PCR)

Nucleic acid probes are being used increasingly in the food industry. These can be relatively insensitive but a new technique for amplification of a target sequence of nucleic acid has the potential of being rapid, sensitive and specific. The method, termed polymerase chain reaction or PCR, utilises a thermostable DNA polymerase from the bacterium Thermus aquaticus. Following thermal denaturation of double stranded DNA, small oligonucleotides, termed primers, are annealed to the single strands of DNA and these determine the starting point for replication of the DNA by the polymerase enzyme. Applications for food microbiology are being researched but problems have been encountered due to the complex nature of many foodstuffs.     

190例脓胸患者病原菌分布及耐药性分析

目的 整理脓胸患者胸膜腔渗出液病原菌分布及药物耐药性状况的流行病学资料,以指导临床合理选用抗生素.方法 收集341例脓胸患者190份胸膜腔渗出液标本,对分离出的病原菌菌种鉴定和药物敏感试验结果进行分析.结果 190份标本中,共分离出40种、92株病原菌,多为条件致病菌,其中G-菌占45.65%、G＋菌占44.57%、真菌占9.78%、厌氧菌占5.43%,对常见抗生素敏感性低,病原菌呈多耐药性.结论 感染脓胸的主要致病菌菌种广泛,常见药物敏感性不高、呈多耐药,临床医生需根据药敏结果合理选用抗生素.     

Microbes, mating, and morality: Individual differences in three functional domains of disgust.

What is the function of disgust? Whereas traditional models have suggested that disgust serves to protect the self or neutralize reminders of our animal nature, an evolutionary perspective suggests that disgust functions to solve 3 qualitatively different adaptive problems related to pathogen avoidance, mate choice, and social interaction. The authors investigated this 3-domain model of disgust across 4 studies and examined how sensitivity to these functional domains relates to individual differences in other psychological constructs. Consistent with their predictions, factor analyses demonstrated that disgust sensitivity partitions into domains related to pathogens, sexuality, and morality. Further, sensitivity to the 3 domains showed predictable differentiation based on sex, perceived vulnerability to disease, psychopathic tendencies, and Big 5 personality traits. In exploring these 3 domains of disgust, the authors introduce a new measure of disgust sensitivity. Appreciation of the functional heterogeneity of disgust has important implications for research on individual differences in disgust sensitivity, emotion, clinical impairments, and neuroscience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vaccine-induced pathogen strain replacement: what are the mechanisms?

Host immune systems impose natural selection on pathogen populations, which respond by evolving different antigenic signatures. Like many evolutionary processes, pathogen evolution reflects an interaction between different levels of selection; pathogens can win in between-strain competition by taking over individual hosts (within-host level) or by infecting more hosts (population level). Vaccination, which intensifies and modifies selection by protecting hosts against one or more pathogen strains, can drive the emergence of new dominant pathogen strains-a phenomenon called vaccine-induced pathogen strain replacement. Here, we review reports of increased incidence of subdominant variants after vaccination campaigns and extend the current model for pathogen strain replacement, which assumes that pathogen strain replacement occurs only through the differential effectiveness of vaccines against different pathogen strains. Based on a recent theoretical study, we suggest a broader range of possible mechanisms, some of which allow pathogen strain replacement even when vaccines are perfect-that is, they protect all vaccinated individuals completely against all pathogen strains. We draw an analogy with ecological and evolutionary explanations for competitive dominance and coexistence that allow for tradeoffs between different competitive and life-history traits.     

The public health significance of Aeromonas spp. in foods

There is now evidence that some strains of Aeromonas species are enteropathogens. Such strains possess virulence properties, such as the ability to produce enterotoxins, cytotoxins, haemolysins and/or the ability to invade epithelial cells. Strains with these properties are common contaminants of drinking water and a wide range of foods. Contact or consumption of contaminated water, especially in summer, is a major risk factor in Aeromonas-associated gastroenteritis. Aeromonas-contaminated foods may also be vehicles of infection. Given the properties of strains that have been described in foods it has been suggested that food-borne illness could result not only from colonization and in vivo expression of virulence factors, but possibly also by intoxication following ingestion of foods that have been stored for a period of time, even under refrigeration. This paper reviews what is known about Aeromonas spp. in foods, their expression of virulence determinants, particularly at refrigeration temperatures, and the questions remaining to be answered to evaluate the risk they pose, so that an appropriate public health response can be determined.