Erysipelothrix rhusiopathiae

Erysipelothrix rhusiopathiae is a facultative, non-spore-forming, non-acid-fast, small, Gram-positive bacillus. The organism was first established as a human pathogen late in the nineteenth century. Three forms of human disease have been recognised since then. These include a localised cutaneous lesion form, erysipeloid, a generalised cutaneous form and a septicaemic form often associated with endocarditis. The organism is ubiquitous and able to persist for a long period of time in the environment, including marine locations. It is a pathogen or a commensal in a wide variety of wild and domestic animals, birds and fish. Swine erysipelas caused by E. rhusiopathiae is the disease of greatest prevalence and economic importance. Diseases in other animals include erysipelas of farmed turkeys, chickens, ducks and emus, and polyarthritis in sheep and lambs. Infection due to E. rhusiopathiae in humans is occupationally related, principally occurring as a result of contact with contaminated animals, their products or wastes, or soil. Erysipeloid is the most common form of infections in humans. While it has been suggested that the incidence of human infection could be declining due to technological advances in animal industries, infection still occurs in specific environments. Additionally, infection by the organism is possibly under-diagnosed due to the resemblance it bears to other infections, and problems encountered in isolation and identification. Various virulence factors have been suggested as being involved in the pathogenicity of E. rhusiopathiae. The presence of a hyaluronidase and neuraminidase has been recognised, and it was shown that neuraminidase plays a significant role in bacterial attachment and subsequent invasion into host cells. The role of hyaluronidase in the disease process is controversial. The presence of a heat labile capsule has been reported as important in virulence. Control of animal disease by sound husbandry, herd management, good sanitation and immunization procedures is recommended.     

Neuraminidase production by Erysipelothrix rhusiopathiae

In order to characterise neuraminidase activity by Erysipelothrix, 85 isolates of Erysipelothrix spp. from a variety of sources including human clinical, marine and terrestrial animals, and the environment were investigated for neuraminidase production. Neuraminidase activity was detected by a peanut lectin haemagglutination method. The effects of media, incubation conditions and pH on the production and activity of neuraminidase were also investigated. Enzyme activity was detected only in the supernatants of the isolates of Erysipelothrix rhusiopathiae which had been incubated in cooked meat broth and Todd Hewitt broth supplemented with horse serum after 16 and 36 h incubation at 37 degrees C. The maximum titres were reached at 40 h in cooked meat broth and 56 h in Todd Hewitt broth supplemented with horse serum. All 58 isolates and the type strain (ATCC 19414) of E. rhusiopathiae produced detectable neuraminidase activity with titres between 10 and 320. The optimal pH for the enzyme activity varied among the isolates with a pH between 6.0 and 7.0 covering the highest enzyme activity of the most. There was no statistically significant difference in the level of neuraminidase activity between isolates from different sources (p > 0.05). Neuraminidase activity was not detected in the non-pathogenic Erysipelothrix spp. such as E. tonsillarum. Neuraminidase was detected only in E. rhusiopathiae suggesting its possible role as a virulence factor. Enzyme production and activity were medium and pH dependent. The peanut lectin haemagglutination assay is a simple, rapid and sensitive method and is particularly useful for the analysis of multiple samples.     

Erysipelothrix rhusiopathiae bacteremia in a horse

Erysipelothrix rhusiopathiae serotype 5 was isolated from blood obtained antemortem from a horse with presenting problems of laminitis, uveitis, acute blindness, localized ventral edema and depression. The patient failed to respond to therapy and died 96 hours after the onset of clinical signs. Cultures of the lung postmortem yielded Erysipelothrix rhusiopathiae serotype 5, Beta-hemolytic Streptococcus sp., Escherichia coli, Proteus sp., and Klebsiella sp.     

Two new serotypes of Erysipelothrix rhusiopathiae.

Among a group of 16 argentine strains of Erysipelothrix rhusiopathiae 2 new serotypes have been found. Typing was performed by means of the agar gel diffusion test. Extracts produced by autoclaving the organisms for 1 hour at 120 degrees C were used as antigen. Antisera against all known types were produced in rabbits. Extracts produced from the two strains in question (Ba?o 36 and Ba?o 107) did not react with any of the knwon type antisera. Antisera against the two strains did not react with extracts of any of the known type strains, but only with extract of their homologous strains. The two new types were designated Type 21 (Ba?o 36) and Type 22 (Ba?o 107).     

Computerized comparison of the protein compositions of Erysipelothrix rhusiopathiae and Erysipelothrix tonsillarum strains

Protein profiles of six Erysipelothrix rhusiopathiae strains, five Erysipelothrix tonsillarum strains and three Erysipelothrix strains of uncertain taxonomic position were studied by sodium dodecyl sulphate-polyactylamide gel electrophoresis (SDS-PAGE). In a computerized comparison of the protein patterns of the strains, the level of similarity between the strains was determined. The SDS-PAGE protein bands were divided into 14 groups based on molecular weight. The relative distribution of proteins within these groups was used to characterize the strains. These distribution patterns were analysed by computing Pearson's correlation coefficient between strains, and by cluster analysis based on Euclidean distances and the unweighted pair-group method of arithmetic averages (UPGMA). The geometric mean of the similarities calculated by Pearson's correlation coefficient was 0.980 +/- 0.018 between the E. rhusiopathiae strains and 0.979 +/- 0.013 for E. tonsillarum strains. The value was 0.932 +/- 0.036 between the strains belonging to different species. However, a threshold value applicable for identification of a given strain to a species could not be established. Of the three strains of uncertain taxonomic position, the strains designated Rotzunge and Iszap 4 had a protein composition more similar to that of E. tonsillarum than to that of the E. rhusiopathiae type strain. The strain designated Pécs 56, which may be a member of a new species according to literature data, gave inconsistent results by the two methods used. The computerized evaluation method developed here is suitable for the comparison of the protein composition of the strains and for the construction of the protein similarity tree by cluster analysis.     

红斑丹毒丝菌的分离鉴定及药敏试验

为确定引起广东潮州某猪场后备母猪发病的病原,采用自制的含马血清的牛心浸汁替代琼脂培养基,从送检的肝脏组织病料中分离到菌落形态一致的1株细菌,根据其菌落形态特征、革兰染色观察、生化特性和16SrDNA序列分析,最终鉴定为红斑丹毒丝菌,将其命名为CZ1。CZ1对31种常用抗菌药物的药敏试验结果显示,该菌对青霉素类和头孢菌素类、四环素类、呋喃类、大部分氨基糖苷类、大环内酯类、喹诺酮类均敏感;对磺胺类药物、利福平和氟罗沙星耐药。对菌株CZ1和实验室早前分离的韶关株SG7分别进行小鼠LD50测定,测得CZ1株和SG7株的LD50分别为1.02×10^4 CFU/mL和7.3×10^3 CFU/mL,表明CZ1株的毒力弱于韶关分离株SG7株。用大鼠分别制备抗CZ1株和SG7株高免血清,血清玻片凝集试验显示,抗CZ1株和SG7株高免血清均能与自身菌株新鲜培养物发生强的凝集反应。交互凝集试验显示,抗CZ1株高免血清能与SG7株新鲜培养物发生强的凝集反应,抗SG7株高免血清能与CZ1株新鲜培养物发生强的凝集反应,表明此次潮州分离株CZ1与SG7株很有可能属于同一种血清型分离株。而2种抗血清均不与现有疫苗株GC42发生凝集反应,提示猪丹毒病的病原血清型可能发生了变化。     

种鸭源猪丹毒丝菌分离及血清学调查

从发生生产性能异常的2个种鸭群中分离到2株革兰阳性丝状菌,经16S rRNA基因序列分析鉴定为猪丹毒丝菌。采用多重PCR对分离株编码表面保护性抗原(spa)基因进行扩增,分别获得大小约1 000 bp和900 bp的片段,判定为spaC型和spaB型。毒力检测结果表明,2个分离株对小鼠的半数致死量(LD50)分别为103CFU/0.2 mL和≤102CFU/0.2 mL。药敏试验结果表明,分离株对青霉素类和大部分头孢菌素类抗生素敏感,对氨基糖苷类等药物具有明显的抗性。为进一步了解猪丹毒丝菌对鸭群的感染情况,本研究采用生长凝集试验对来源于3个不同鸭场的种鸭群进行血清学调查,结果,抗丹毒丝菌抗体阳性率(抗体效价≥16)分别为82%、35%和20%,表明鸭群中广泛存在猪丹毒丝菌感染。     

猪丹毒杆菌的分离鉴定及其SpaA基因的遗传变异分析

为确定导致福建某猪场猪只发病的病原,从病猪心、肺中分离并纯化细菌,根据其形态特征、培养特性、生化试验及PCR鉴定,确定为猪丹毒杆菌。SpaA基因测序结果表明该分离菌在第609位点处出现了由胸腺嘧啶突变为鸟嘌呤,对应的氨基酸是由甲硫氨酸突变为异亮氨酸。致病性试验结果表明,2．1×10^8CFU／mL的菌液10倍稀释后,感染28日龄健康昆明小鼠,该分离菌对28日龄健康小鼠的半数致死量为2．1×10^3.5CFu／mL,死亡小鼠的剖解病变表现为心肌有白色坏死点,肝脏实变、坏死,肺出血和脾脏梗死等,并分离出与感染菌株形态特征完全一致的菌落。药敏试验结果显示,该分离菌株对青霉素、红霉素、氨苄青霉素、强力霉素、先锋霉素、阿奇霉素等较为敏感。     

1株猪丹毒杆菌的分离与鉴定

为确定导致安徽和县某猪场猪只发病的病原,从该猪场送检病料(心、肺、脾、肝)中分离并纯化细菌,根据其形态特征、PCR鉴定及生化试验结果,确诊为猪丹毒杆菌。spa A基因序列分析结果显示该菌与猪丹毒杆菌G4T10(Gen Bank登录号:KF150604.1)有99%的同源性。全自动生化反应报告该菌为丹毒丝菌的概率高达95%。小鼠攻毒试验表明,试验组小鼠在腹股沟皮下注射该菌后,4 d内全部死亡;死亡小鼠剖检可见全身败血性出血,各脏器均有病变,从死亡小鼠的血液、心、肝、脾、肺等组织中分离到与该感染菌株形态特征完全一致的细菌。药敏试验结果表明,该菌对β-内酰胺类和大环内酯类抗生素敏感,对链霉素、卡那霉素、四环素、多西环素、林可霉素和磺胺异恶唑耐受。