Annual incidence, prevalence and transmission characteristics of Streptococcus agalactiae in Danish dairy herds

Contagious mastitis pathogens continue to pose an economic threat to the dairy industry. An understanding of their frequency and transmission dynamics is central to evaluating the effectiveness of control programmes. The objectives of this study were twofold: (1) to estimate the annual herd-level incidence rates and apparent prevalences of Streptococcus agalactiae (S. agalactiae) in the population of Danish dairy cattle herds over a 10-year period from 2000 to 2009 inclusive and (2) to estimate the herd-level entry and exit rates (demographic parameters), the transmission parameter, β, and recovery rate for S. agalactiae infection. Data covering the specified period, on bacteriological culture of all bulk tank milk samples collected annually as part of the mandatory Danish S. agalactiae surveillance scheme, were extracted from the Danish Cattle Database and subsequently analysed. There was an increasing trend in both the incidence and prevalence of S. agalactiae over the study period. Per 100 herd-years the value of β was 54.1 (95% confidence interval [CI] 46.0-63.7); entry rate 0.3 (95% CI 0.2-0.4); infection-related exit rate 7.1 (95% CI 5.6-8.9); non-infection related exit rate 9.2 (95% CI 7.4-11.5) and recovery rate 40.0 (95% CI 36.8-43.5). This study demonstrates a need to tighten the current controls against S. agalactiae in order to lower its incidence.     

鱼类无乳链球菌病

无乳链球菌亦称为B组链球菌,是一种在自然界广泛存在的革兰阳性菌,是人类的重要病原之一,也是鱼类的重要病原菌。近年来,无乳链球菌成为鱼类链球菌病的主要病原之一,鱼类感染无乳链球菌的常见临床症状包括眼球突出、腹部肿胀、脊骨弯曲、鳍条基部出血等,发病率和死亡率高,常造成严重的经济损失,危害着水产养殖业的健康发展。论文对鱼类无乳链球菌病的研究进行了总结,对鱼类无乳链球菌病病原、致病机理进行综述,介绍了鱼类无乳链球菌病常见的诊断方法,以及现阶段针对鱼类无乳链球菌病的疫苗开发情况,旨在进一步丰富、完善鱼类无乳链球菌病的研究资料,为更好的防治鱼类无乳链球菌病提供参考。     

Monoclonal antibodies produced to Streptococcus agalactiae

Two monoclonal antibodies produced against Streptococcus agalactiae were studied for their specificity and sensitivity. Both reacted strongly in the enzyme-linked immunosorbent assay and indirect fluorescent antibody test with S agalactiae, but did not react with other gram-positive organisms frequently found in test herds in Mississippi. A procedure for using monoclonal antibodies in the detection of S agalactiae-infected milk samples is proposed.     

Streptococcus agalactiae mastitis: a review.

Streptococcus agalactiae continues to be a major cause of subclinical mastitis in dairy cattle and a source of economic loss for the industry. Veterinarians are often asked to provide information on herd level control and eradication of S. agalactiae mastitis. This review collects and collates relevant publications on the subject. The literature search was conducted in 1993 on the Agricola database. Articles related to S. agalactiae epidemiology, pathogen identification techniques, milk quality consequences, and control, prevention, and therapy were included. Streptococcus agalactiae is an oblique parasite of the bovine mammary gland and is susceptible to treatment with a variety of antibiotics. Despite this fact, where state or provincial census data are available, herd prevalence levels range from 11% (Alberta, 1991) to 47% (Vermont, 1985). Infection with S. agalactiae is associated with elevated somatic cell count and total bacteria count and a decrease in the quantity and quality of milk products produced. Bulk tank milk culture has, using traditional milk culture techniques, had a low sensitivity for identifying S. agalactiae at the herd level. New culture methods, using selective media and large inocula, have substantially improved the sensitivity of bulk tank culture. Efficacy of therapy on individual cows remains high. Protocols for therapy of all infected animals in a herd are generally successful in eradicating the pathogen from the herd, especially if they are followed up with good udder hygiene techniques.     

Research Progress on Fish Streptococcus agalactiae Disease

Streptococcus agalactiae is common zoonotic bacteria,which cause neonatal pneumonia,meningitis,septicemia and mastitis in dairy cows.In recent years,it was also be isolated from aquatic animals frequently.Especially since 2007,diseases caused by the bacteria outbreak in Guangdong,Hainan,Fujian,Guangxi and other tilapia aquaculture areas and had a serious threat to the healthy development of tilapia aquaculture in china.In this paper, research progresses on fish Streptococcus agalactiae disease were reviewed.The etiology,epidemiology,symptoms,pathological changes,virulence factors (capsular polysaccharide,CAMP factor,Sip,protein alpha,C5a peptidase) and prevention and control were included in the review,which would provide references for the fish Streptococcus agalactiae disease prevention and control.     

鱼类无乳链球菌病的研究进展

无乳链球菌是常见的人兽共患病原菌,常导致新生儿肺炎、脑膜炎、败血症及奶牛乳腺炎。近年来,在水生动物体内也频繁分离到该菌,尤其是自2007年以来,该菌每年都在中国广东、海南、福建、广西等罗非鱼主要养殖区暴发流行,严重威胁着罗非鱼养殖业的健康发展。作者综述了当前国内外对鱼类无乳链球菌病的病原学、流行病学、症状、病理变化、毒力因子（荚膜多糖、CAMP因子、表面免疫原性蛋白、α蛋白、C5a肽酶）和防控等方面的研究进展,以期为中国鱼类无乳链球菌病的防控提供参考。     

Molecular characterization of Streptococcus agalactiae and Streptococcus uberis isolates from bovine milk

Streptococci are one among the major mastitis pathogens which have a considerable impact on cow health, milk quality, and productivity. The aim of the present study was to investigate the occurrence and virulence characteristics of streptococci from bovine milk and to assess the molecular epidemiology and population structure of the Indian isolates using multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). Out of a total of 209 bovine composite milk samples screened from four herds (A–D), 30 Streptococcus spp. were isolated from 29 milk samples. Among the 30 isolates, species-specific PCR and partial 16S rRNA gene sequence analysis identified 17 Streptococcus agalactiae arising from herd A and 13 Streptococcus uberis comprising of 5, 7, and 1 isolates from herds B, C, and D respectively. PCR based screening for virulence genes revealed the presence of the cfb and the pavA genes in 17 and 1 S. agalactiae isolates, respectively. Similarly, in S. uberis isolates, cfu gene was present in six isolates from herd C, the pau A/skc gene in all the isolates from herds B, C, and D, whereas the sua gene was present in four isolates from herd B and the only isolate from herd D. On MLST analysis, all the S. agalactiae isolates were found to be of a novel sequence type (ST), ST-483, reported for the first time and is a single locus variant of the predicted subgroup founder ST-310, while the S. uberis isolates were found to be of three novel sequence types, namely ST-439, ST-474, and ST-475, all reported for the first time. ST-474 was a double locus variant of three different STs of global clonal complex ST-143 considered to be associated with clinical and subclinical mastitis, but ST-439 and ST-475 were singletons. Unique sequence types identified for both S. agalactiae and S. uberis were found to be herd specific. On PFGE analysis, identical or closely related restriction patterns for S. agalactiae ST-483 and S. uberis ST-439 in herds A and B respectively, but an unrelated restriction pattern for S. uberis ST-474 and ST-475 isolates from herds D and C respectively, were obtained. This signifies that the isolates of particular ST may exhibit related PFGE patterns suggesting detection of a faster molecular clock by PFGE than MLST. Since all the isolates of both the species belonged to novel sequence types, their epidemiological significance in global context could not be ascertained, however, evidence suggests that they have uniquely evolved in Indian conditions. Further research would be useful for understanding the role of these pathogens in bovine sub-clinical mastitis and implementing effective control strategies in India.     

Intramammary infections in a dairy herd with a low incidence of Streptococcus agalactiae and Staphylococcus aureus infections.

In a dairy herd with a low incidence of intrammary infections due to Streptococcus agalactiae and Staphylococcus aureus, clinical mastitis remained a serious problem despite good control of nonclinical mastitis through postmilking teat disinfection and antibiotic therapy of known infected quarters at the end of lactation. During the 2-year study, the incidence of clinical mastitis was 0.88 cases/cow-year; 32.2% were caused by streptococcal species other than Str agalactiae and 33.5% by gram-negative organisms. Among all new infections detected, 54.1% were caused by streptococcal species other than Str agalactiae and 25.7% by gram-negative bacteria. Among new infections, 41.6% occurred during the nonlactating period or within a few days of calving. Incidence of clinical mastitis was highest in the 1st month of lactation. Among 84 gram-negative infections, 42.8% were caused by Klebsiella pneumoniae, 20.2% by Escherichia coli, and 23.8% by Enterobacter spp. Among the many serotypes of K pneumoniae and E coli, none was predominant.     

无乳链球菌及其血清型的PCR方法鉴定

无乳链球菌(S.agalactiae)是引起奶牛乳房炎和新生儿期侵袭性感染(包括败血症、肺炎和脑膜炎)的重要病原菌.为快速准确地鉴定S.agalactiae及其血清型,本研究对22株从国内不同地区分离的牛源链球菌进行生化鉴定以及针对S.agalactiae保守基因sip进行PCR鉴定,并采用多重PCR技术扩增sip基因阳性菌株的cps基因进行血清分型.结果显示,PCR扩增sip基因阳性17株,其中15株生化试验与PCR结果一致;多重PCR扩增cps基因显示,其中Ia型4株、Ⅱ型11株、Ⅲ型2株.本研究为鉴定S.agalactiae及其血清型提供了参考.     

A novel family of fibrinogen-binding proteins in Streptococcus agalactiae

Streptococcus agalactiae is a contagious pathogen in bovine mastitis. It is also one of the leading causes to neonatal pneumonia, sepsis and meningitis in Europe and North America. Although extracellular bacterial proteins that interact with host structures are putative vaccine components, so far only a few receptins have been identified and characterised from this organism. The aim of the present study was to identify fibrinogen-binding receptins from a shotgun phage display library constructed from the bovine type strain CCUG 4208. A novel extracellular receptin was identified after selecting the library against bovine fibrinogen. This protein is a member of a family of at least three proteins that share the fibrinogen-binding region as well as the N-terminal signal sequence, whereas the intervening region varies in size and has almost no sequence similarity. Proteins of this family are present also in human isolates of S. agalactiae, although binding to human fibrinogen has not been detected.     

无乳链球菌致病因子的研究进展

无乳链球菌是人和动物的主要致病菌之一,该菌可引起人和动物的脑膜炎、肺炎、败血症等疾病。目前已发现的无乳链球菌主要致病因子包括荚膜多糖、溶血素、透明质酸酶、环磷酸腺苷(CAMP)因子、超氧化物歧化酶和丝氨酸/苏氨酸蛋白激酶等。作者就上述几类致病因子进行综述,介绍了近年来国内外无乳链球菌的致病性及致病机理等方面的一些研究进展。     

奶牛乳腺炎无乳链球菌的分离鉴定

无乳链球菌是比较常见的导致奶牛乳腺炎的病原菌,该菌也是山羊、绵羊慢性乳房炎的病原菌之一,也能引起婴儿败血症、脑膜炎和肺炎等。人医临床上对该菌以B群链球菌相称。试验从内蒙古呼和浩特市周边5个牛场中患有乳房炎的病牛中采集120份乳样,通过分菌培养、形态学观察、生化试验,鉴定出14株无乳链球菌,同时对这14株菌进行了药物敏感试验、动物致病性试验等。试验结果发现,所分离到的无乳链球菌对青霉素类、氨基糖苷类药物高度敏感,对磺胺类、氟哌酸、喹诺酮类药物中度敏感。动物致病性试验对小鼠的致死率达到80%以上。