吉林延边地区牛气肿疽病的诊断报告

本研究旨在对吉林省延吉市三道湾镇两位农户饲养的病死黄牛进行快速诊断。本试验采集肝脏、脾脏、心脏、肌肉等组织,通过流行病学调查、临床剖检、显微镜观察、细菌培养观察、生化试验、分子生物学试验及动物试验进行气肿疽病诊断。病死黄牛的肌肉部位触压有捻发音,切面有大量血液和气泡流出,镜检可见两端钝圆、有芽孢的大杆菌,在肝片肉汤培养基中形成上清清朗、底部有松散的白色沉淀,生化试验均呈现气肿疽厌气菌所特有的产酸产气反应,PCR扩增出大小为501 bp的特异性条带。结果表明延边地区两病死黄牛感染了气肿疽病,证明了该地区气肿疽梭菌的存在。本试验首次分离鉴定出气肿疽梭菌延边株,为该地区气肿疽病的诊断和防制提供了重要的参考依据,同时为进一步研究该病的药物防制和免疫防制奠定了重要基础。     

Isolation,Identification and Pathogenicity Research of a Strain of Clostridium perfringens from Goat

A pathogenic bacteria was isolated from a dead goat,and it was identified as goat-pathogenic type A Clostridium perfringens by differential culture,biochemical test,molecular biological technology and animal pathogenicity test.Analysis results of toxin genes showed that this bacteria contained both α and β2 toxin genes.Animal pathogenicity test result showed that this bacteria was highly pathogenic to mice,and the same bacteria was isolated from dead mice as which was isolated from the dead goat,so it was certain that type A Clostridium perfringens was the main pathogenic bacteria which caused the goat dead.The results would provide scientific basis for the treatment and prevention of the disease caused by Clostridium perfringens in this goat farm.     

一株山羊魏氏梭菌的分离鉴定及其致病性研究

本试验从一例病死山羊组织内分离到一株致病性细菌,通过鉴别培养、生化试验、分子生物学试验和动物致病性试验,证明该病原菌为羊致病性A型魏氏梭菌;毒素基因分析结果显示,该菌同时含有α和β2两种毒素基因;动物致病性试验结果表明,该菌对昆明小鼠具有较强的致病性,并从试验致死的昆明小鼠病料中分离到了与病死山羊病原相一致的细菌,从而确定A型魏氏梭菌为引起该山羊死亡的主要病原菌。本试验结果为该羊场魏氏梭菌病的治疗和预防提供了科学依据。     

奶牛产气荚膜梭菌的分离鉴定与药物敏感性分析

本研究旨在对从奶牛内脏、组织病料样品中分离得到产气荚膜梭菌并进行鉴定分型,为后续疫苗研究提供材料,并通过药敏试验筛选出较为敏感的药物以针对性的指导牧场对牛群进行治疗并提出有效的防治隔离建议。2019年山东21家牧场部分奶牛出现腹泻、便血及短期内死亡等现象,对部分死亡奶牛进行剖检,并送检64份内脏、组织病料样品进行CP培养初筛,对初筛阳性菌株用生化鉴定及PCR分型鉴定;以16S rDNA技术对CP菌株进行同源性分析;采用E-test法测定分离菌对7种抗菌药物（红霉素、左氟沙星、利奈唑胺、万古霉素、克林霉素、四环素、利福平）的最低抑菌浓度（micro inhibition concentration,MIC）,筛选出敏感药物。8份样品血琼脂培养基细菌培养出现灰白色菌落,梭菌显色培养基培养为橘红色梭菌典型特征菌落;生化鉴定结果符合产气荚膜梭菌特征;PCR分型结果显示5株为A型、2株C型和1株E型;16S rDNA分析得出8株分离菌与产气荚膜梭菌同源性最高可达100%;8株CP菌株对7种药物敏感,其中2株对克林霉素、利福平更为敏感,3株对红霉素及利奈唑胺敏感,1株对左氟沙星更敏感。对有病牛的2家牧场推荐使用林可酰胺类、利福霉素类及大环内酯类药物进行防治,对牧场防治效果及时追踪,对于没有治疗价值的牛立即扑杀,无害化处理,改善饲养条件,减小饲养密度。     

鸡源高产淀粉酶丁酸梭菌的分离鉴定

为了获得产淀粉酶的丁酸梭菌,本研究从鸡小肠表面黏液中进行丁酸梭菌的分离与筛选,首先对样品进行80℃水浴10 min除去非芽孢菌后,然后接种到TSN培养基进行菌株的分离与筛选。对分离到的菌株进行菌落形态、显微形态初步观察,然后对疑似丁酸梭菌的菌株进行产酸能力和淀粉酶酶活检测,最后对既产酸又高产淀粉酶的菌株进行生理生化鉴定和16S rDNA序列分析。结果表明分离到一株革兰氏阳性厌氧菌C.B1,菌体呈短杆状,能形成圆形或椭圆形芽孢,生理生化结果也符合丁酸梭菌的基本特征,16S rDNA序列长度为1450 bp,与丁酸梭菌的同源性高达99%以上,因此确定该分离菌株为丁酸梭菌,为进一步开发新的微生态制剂奠定了基础。     

腐败梭菌无毒重组α毒素的表达与免疫保护性分析

本研究旨在获得腐败梭菌无毒重组α毒素,并评价其免疫保护性。对已知的腐败梭菌α毒素编码基因进行优化设计和人工合成,获得了缺少第212-222位共11个氨基酸编码序列的基因片段（GCSA_Δ11）。将该基因克隆至原核表达载体pET-30a（+）中进行表达与纯化。利用Western blot方法检测获得的重组α毒素（rCSA_Δ11）与腐败梭菌天然毒素抗血清的反应性,并采用小鼠检测其毒力。随后,以rCSA_Δ11制备疫苗免疫家兔,按照《中华人民共和国兽药典》（2015年版）规定的方法检测家兔血清的中和抗体效价。结果表明,rCSA_Δ11可溶表达比例可达46%,且能与腐败梭菌天然毒素抗血清反应。进一步的试验结果显示,rCSA_Δ11丧失了对小鼠的毒力,0.1 mL的一免兔血清可中和8~12个小鼠最小致死量（MLD）的腐败梭菌天然毒素;二免兔血清可中和32~45个小鼠MLD的腐败梭菌天然毒素。1个家兔MLD的腐败梭菌天然毒素攻毒后,对照组家兔4/4死亡,免疫组家兔得到了100%（4/4）的保护。综上表明,无毒性的rCSA_Δ11保留了良好的免疫保护性,从而为腐败梭菌病基因工程亚单位疫苗的研制提供了重要的试验数据。     

Diagnosis and Treatment of Serotype A Pasteurella multocida Infection in a Dairy Farm

The assay was aimed to clarify the reasons why dairy cattle became ill with the symptoms including fever,breathing difficulty,salivation and subcutaneous emphysema at neck or chest in a dairy cow farm at Hubei province,even part of dairy cows were dead for exhaustion.The disease was diagnosed by laboratory methods,and treatment scheme was proposed.The samples from heart,liver,lung or trachea tissues were collected,then M.bovis and pathogenic bacteria were isolated,respectively.Biochemical characteristics,pathogenicity test and drug sensitivity analysis were performed on the isolated pathogenic bacteria.RNA was extracted from bovine serum,then bovine ephemeral fever virus was identified by RT-PCR.The results showed that nothing grew in PPLO medium,and the isolated bacteria could form indole,but did not ferment glycogen and inositol in the biochemical tests.The isolated pathogenic bacteria was conformed as serotype A P.multocida by PCR while bovine ephemeral fever virus of RT-PCR result was negative.The pathogen could kill mice and the pathogenic bacteria could be isolated from heart blood of the dead mice in pathogenicity test.The isolated bacteria was sensitive to cefoperazone or levofloxacin in drug sensitivity analysis.In conclusion,the disease was diagnosed as bovine serotype A P.multocida infection.Some treatments including choosing sensitive antibiotic drugs based on the drug sensitivity tests,holding sick cattle under quarantine treatment and isolating suspected cattle should be taken.Moreover,some complex measures such as keeping the air flowing,cleaning up in time,improving the management,and preventing stress from congestion,cold and long distance transport were very important to prevent and control serotype A P.multocida infection in dairy cows.     

某牛场奶牛A型多杀性巴氏杆菌的分离鉴定

湖北某奶牛场牛群爆发体温升高、呼吸困难、流涎及颈胸皮下气肿等症状的疾病,部分发病牛衰竭死亡,为确诊牛场牛群发病原因并提出防控方案,本试验采集死亡牛的心脏、肝脏、肺脏及气管组织进行病原菌的分离纯化及PCR鉴定,并对鉴定的病原菌进行生化特性鉴定、致病性试验和药物敏感性分析;同时提取患牛血清RNA,开展牛流行热病毒的RT-PCR鉴定。结果显示,病料在类胸膜肺炎固体培养基上不生长,生化特性鉴定显示能形成靛基质、不发酵肝糖和肌醇;牛流行热病毒RT-PCR扩增阴性;所分离的病原菌经16S rRNA及牛A型多杀性巴氏杆菌特异性引物PCR扩增阳性;致病性试验显示该病原可致死小鼠,且能从死亡小鼠体内分离到感染菌;药敏试验结果显示该病菌对头孢哌酮、左氧氟沙星敏感,其他20种临床常见药物表现耐药。综上所述,该牛场患病牛确诊为牛A型多杀性巴氏杆菌感染,建议根据药敏试验结果选择敏感药物,对患病牛进行隔离治疗,疑似患病牛隔离观察,同时加强通风,及时清理污物并消毒,改善饲养管理,避免拥挤、寒冷及长途运输等应激因素。     

甘肃、宁夏地区奶牛衣原体血清流行病学调查及风险因素分析

本研究旨在查明甘肃与宁夏地区奶牛衣原体的感染情况并分析影响其感染的风险因素。本试验采用间接血凝试验(IHA)方法检测了甘肃榆中(751份)、宁夏青铜峡(450份)和宁夏吴忠(456份)3个地方总计1 657份奶牛血清样品,并应用流行病学调查及统计学方法对影响奶牛衣原体感染的因素进行了分析。流行病学调查结果显示,奶牛衣原体抗体总阳性率为29.33%;应用logistic回归分析评估奶牛衣原体感染的风险因素,结果显示年龄和胎次不是显著风险因素(P>0.05),而地区因素是影响奶牛衣原体感染的风险因素(P<0.05)。奶牛衣原体抗体滴度最高达1:1 024。结果表明,甘肃和宁夏地区奶牛衣原体普遍流行。因此,应当提高对调查地区奶牛衣原体感染的重视,采取适当的综合控制方法和有效的管理措施以防控奶牛衣原体病,以保证奶牛养殖业的经济效益。     

Seroprevalence Investigation and Risk Factors Analysis of Chlamydia Infection in Dairy Cattle in Gansu and Ningxia Areas

The objective of the present investigation was to examine seroprevalence of Chlamydia in dairy cattle in Gansu and Ningxia areas, Northwest China, and to analyze the factors affecting Chlamydia infection in dairy cattle.Indirect hemagglutination assay (IHA) was used to detect antibodies against Chlamydia in 1 657 dairy cattle serum samples from Gansu and Ningxia areas.Epidemiological investigation and statistical methods were used to analyze the data.The results showed that the overall seroprevalence was 29.33%, logistic regression analysis was applied to evaluate the risk factors of Chlamydia infection in dairy cattle, and the results indicated that age and numbers of pregnancy of dairy cattle were not the significant risk factors (P>0.05), and were left out of the final model, however, region was considered as the main risk factor associated with Chlamydia infection (P<0.05).The highest titer was 1:1 024.In conclusion, the results of the present survey indicated the widespread of Chlamydia infection in Gansu and Ningxia areas.In order to ensure the economic benefit of dairy farming, we should pay more attention to Chlamydia infection in dairy cattle, and integrated control strategies and efficient management measures should be implemented to prevent and control Chlamydia infection in dairy cattle.     

Pathological changes in the pericardium and meninges of cattle associated with Clostridium chauvoei

Twenty-nine cases of Clostridium chauvoei infection in cattle were investigated over a two-year period. Fourteen had lesions of myositis only, eight had lesions of both myositis and fibrinous pericarditis, six had lesions of fibrinous pericarditis only and one had lesions of purulent meningitis only. Cl chauvoei was identified in all the lesions using the fluorescent antibody technique.     

芽孢杆菌制剂对断奶仔猪血液和免疫指标的影响

试验针对不同芽孢杆菌复合制剂对断奶仔猪血液学指标、血液生化指标和免疫功能的影响进行了研究。对照组饲喂基础日粮,试验Ⅰ、Ⅱ、Ⅲ、Ⅳ组在基础日粮中分别添加凝结芽孢杆菌+巨大芽孢杆菌、酪酸菌+巨大芽孢杆菌、凝结芽孢杆菌+酪酸菌、凝结芽孢杆菌+酪酸菌+巨大芽孢杆菌复合制剂,添加量0.2%,饲喂43 d。结果表明,各组的血液红细胞数、白细胞数、血小板数和血红蛋白浓度均无显著差异(P>0.05)。各组的血清谷丙转氨酶、总蛋白、白蛋白、尿素氮、肌酐和葡萄糖含量均无显著差异(P>0.05)。试验Ⅰ、Ⅱ组的血清谷草转氨酶含量与对照组差异不显著(P>0.05),但试验Ⅲ、Ⅳ组则显著提高(P<0.05)。试验Ⅰ、Ⅱ、Ⅲ组的血清总胆固醇和甘油三酯含量与对照组差异不显著(P>0.05),但试验Ⅳ组则显著提高(P<0.05)。试验Ⅰ组的血清IgG和IgM含量与对照组差异不显著(P>0.05),但试验Ⅱ、Ⅲ、Ⅳ组则显著提高(P<0.05)。研究结果为芽孢杆菌在养殖业中的应用提供了一定的理论依据和参考价值。     

Effects of Clostridium butyricum on Calcium and Phosphorus Metabolism and Tibia Indexes of Broilers

The effects of Clostridium butyricum on calcium and phosphorus metabolism and tibia indexes in broiler chickens were evaluated in this study.One hundred eighty 1-day-old healthy Arbor Acres broiler chickens were randomly allotted to three groups:the control group,antibiotic group and Clostridium butyricum group with six replicates per group and 10 chickens per replicate.The broilers in control group were fed with the basic diet,while the antibiotic group was fed with 5 mg/kg of flavomycin,75 mg/kg of aureomycin and 20 mg/kg of kitasamycin.Clostridium butyricum group was fed with 2.5×10⁸ CFU/kg Clostridium butyricum in the basic diet for 42 days.The results showed that:Compared with the control group,①the supplementation of Clostridium butyricum did not significantly affect serum calcium and phosphorus level of broilers (P>0.05),and adding antibiotic significantly increased serum calcium level of 21-day-old broilers(P<0.05).②The addition of Clostridium butyricum increased tibia strength at 21-day-old (P<0.05),and phosphorus content of tibia at 42-day-old (P<0.01).③The supplementation of Clostridium butyricum extremely significantly decreased the phosphorus content in feces of 21-day-old broilers (P<0.01),and had no significant difference with ATB group (P>0.05).The supplementation of Clostridium butyricum increased calcium content (P<0.01) and phosphorus content (P<0.05) in feces of 42-day-old broilers.Based on the above results,adding 2.5×10⁸ CFU/kg Clostridium butyricum could improve the tibia development,increase the absorption and utilization of calcium and phosphorus by broilers,and efficiently reduce the calcium and phosphorus excretion of 21-day-old broilers,but not for 42-day-old broilers.     

丁酸梭菌对肉鸡钙磷代谢和胫骨指标的影响

试验通过在基础日粮中添加丁酸梭菌,研究其对肉鸡钙磷代谢和胫骨指标的影响。选择1日龄180只健康AA肉鸡,随机分入3个处理组,每个处理组6个重复,分别为对照组、抗生素组（ATB）和丁酸梭菌组（CB）。对照组饲喂基础日粮,ATB组在基础日粮中添加5 mg/kg黄霉素、75 mg/kg金霉素和20 mg/kg吉他霉素,CB组在基础日粮中添加2.5×10⁸ CFU/kg丁酸梭菌,试验期42 d。结果显示,与对照组相比,①CB组肉鸡血清钙（Ca）、磷（P）含量差异不显著（P>0.05）,21日龄ATB组肉鸡血清钙含量显著提高（P<0.05）;②21日龄CB组肉鸡胫骨强度显著提高（P<0.05）;42日龄CB组肉鸡胫骨磷含量极显著提高（P<0.01）;③21日龄CB组肉鸡排泄物中磷含量极显著降低（P<0.01）,并与ATB组无显著差异;42日龄CB组肉鸡排泄物中钙含量极显著提高（P<0.01）,排泄物中磷含量显著提高（P<0.05）。综合上述结果,在AA肉鸡基础日粮中添加2.5×10⁸ CFU/kg丁酸梭菌有利于改善肉鸡的胫骨发育,改善肉鸡对钙、磷的吸收利用,能有效降低21日龄肉鸡钙、磷排泄量,但并未降低42日龄肉鸡排泄物中钙、磷含量。     

Expression and Protective Efficacy of Clostridium perfringens β toxin Derivative

This study was conducted to obtain the Clostridium perfringens β toxin (CPB) derivative and to evaluate its virulence and immunoprotection. Based on the known sequence, four amino acid mutations, R212E, L268G, Y266A and W275A, were introduced into the gene of Clostridium perfringens CPB. Meanwhile, genes of Th cell and N-terminal of flagellin were added to 5' of the CPB gene, respectively. Then the gene GTF_NCPB_m4 was optimized and synthesized, and was subsequently cloned into the prokaryotic expression vector pET-30a (＋) for expression and purification to get the recombinant protein, rTF_NCPB_m4. Reactivity of rTF_NCPB_m4with antiserum of Clostridium perfringens type C crude toxins was detected by Western blot. Meanwhile, the toxicity of rTF_NCPB_m4 to mice was evaluated. According to the method prescribed in Chinese Veterinary Pharmacopoeia (2015), rabbits were immunized with rTF_NCPB_m4 to prepare antiserum and detect the neutralizing titer against Clostridium perfringens type C crude toxins. Results showed that rTF_NCPB_m4 was presented predominantly in an insoluble form (inclusion bodies), and it could react with the antiserum of Clostridium perfringens type C crude toxins. rTF_NCPB_m4 with an injection volume of 50 μg was still not fatal to mice. Sera from rabbits immunized with rTF_NCPB_m4can neutralize 10-20 mouse minimum lethal doses (MLD) of Clostridium perfringens type C crude toxins after twice immunization. Moreover, rabbits immunized with rTF_NCPB_m4 can fully resist 1 rabbit MLD of Clostridium perfringens type C crude toxins challenge, whereas all of the rabbits died (4/4) in the control groups. These data suggest that rTF_NCPB_m4 is a potential vaccine candidate for the subunit vaccine of Clostridium perfringens type C.     

重组产气荚膜梭菌β毒素突变体的表达与免疫保护性分析

旨在获得产气荚膜梭菌β毒素（CPB）的重组突变体,并评价其毒力及免疫保护性。对已知的产气荚膜梭菌CPB编码基因进行优化设计,同时引入4个氨基酸突变位点,分别是第212位的精氨酸突变为谷氨酸,第268位的亮氨酸突变为甘氨酸,266位的酪氨酸和275位的色氨酸突变为丙氨酸。此外,在该基因5'端添加Th细胞表位（T）和鞭毛蛋白（flagellin）N末端的编码序列,经人工合成获得重组基因片段（GTF_NCPB_m4）。将GTF_NCPB_m4克隆至原核表达载体pET-30a（＋）中进行表达与纯化,获得重组蛋白rTF_NCPB_m4。利用Western blot方法检测rTF_NCPB_m4与C型产气荚膜梭菌毒素抗血清的反应性,并检测rTF_NCPB_m4对小鼠的毒力。随后,以rTF_NCPB_m4免疫家兔,按照《中华人民共和国兽药典》（2015年版）规定的方法检测家兔血清对C型产气荚膜梭菌毒素的中和抗体效价。结果表明,rTF_NCPB_m4主要以包涵体的形式表达且能与C型产气荚膜梭菌毒素抗血清反应。小鼠安全性试验显示,50 μg的rTF_NCPB_m4对小鼠仍无致死性;免疫rTF_NCPB_m4后,每毫升家兔二免抗血清可中和10~20个小鼠最小致死量（MLD）的C型产气荚膜梭菌毒素;1个家兔MLD的C型产气荚膜梭菌毒素攻毒后,对照组家兔4/4死亡,免疫组家兔得到了100%（4/4）的保护。以上结果说明,rTF_NCPB_m4在丧失毒力的同时保留了良好的免疫原性,从而为C型产气荚膜梭菌病基因工程疫苗的研制提供了重要的数据。     

一株丁酸梭菌的分离鉴定及其益生特性研究

本研究探索了丁酸梭菌分离株的益生特性，旨在为其在仔猪日粮中的应用提供理论依据。利用常规方法分离丁酸梭菌并进行纯培养，经生化检测和16S rRNA基因测序，对分离菌株进行鉴定；采用活菌计数法和牛津杯法研究分离株培养上清对3种致病菌的抑制作用、分离株黏附猪小肠上皮细胞（IPEC-J2）的特性及其对致病菌黏附细胞的抑制作用；采用细胞计数法研究分离株对IPEC-J2生长的影响；采用ELISA检测分离株处理细胞后培养上清液中细胞因子水平。结果表明，本研究成功分离到一株丁酸梭菌。与对照组相比，丁酸梭菌培养上清对3种致病菌生长抑制效果均显著（P<0.05）；丁酸梭菌可黏附于IPEC-J2，并且黏附效果最佳的感染复数（MOI）为50，最适处理时长为3 h；丁酸梭菌对3种致病菌黏附IPEC-J2均具有显著抑制作用（P<0.05）；丁酸梭菌MOI为1、10和50时细胞生长正常、形态完好，MOI为100时IPEC-J2生长受到显著抑制，同时出现部分细胞死亡；MOI为1时细胞因子水平无差异，MOI为10、50和100时细胞因子水平均显著增高（P<0.05）。综上所述，本研究分离的一株丁酸梭菌具有较好的益生特性，为其在生产中的应用提供了理论依据。     

Extracellular proteins of Clostridium chauvoei are protective in a mouse model

The anaerobic bacillus Clostridium chauvoei is the causative agent of blackleg, a lethal disease that has an important impact on the sheep and cattle industry worldwide. Immunity to C. chauvoei is considered to be mainly anticellular, and for this reason there is scarce information about the immunogenicity of extracellular proteins. In this work variations in protein profiles, immune response by ELISA and protective capacity of culture supernatants of three C. chauvoei strains, collected at different growth phases, are reported. Sera raised against extracellular antigens also recognised cellular antigens of the same molecular masses. Partially purified cell-free supernatants and those concentrated 10 times by ultrafiltration (C-CFS), obtained at the early stationary phase of growth, induced a strong immunoprotective response, even at low doses, that was more marked for C. chauvoei strain ATCC 10092 (p < or = 0.05). With C-CFS formulations, a clear relationship was observed between IgG titres, protective capacity and concentration of the antigen doses, indicating a specific immune response.     

An outbreak of chronic pneumonia and polyarthritis syndrome caused by Mycoplasma bovis in feedlot bison (Bison bison).

Mycoplasma bovis was identified by a specific lesion, conventional bacterial culture, immunohistochemistry, and polymerase chain reaction in 2 feedlot bison found dead with severe, chronic, caseonecrotic pneumonia; polyarthritis; and laryngitis. On microscopic examination, pulmonary lesions were characterized by prominent, well-defined areas of caseous necrosis and bronchiectasis. Immunohistochemical analysis of lung exhibited staining in bronchiolar epithelium and in random areas of caseous necrosis. On gross examination, the laryngeal lesion observed in 1 animal was typical of changes seen in cases of calf diphtheria. Nasal swabs taken from 6 clinically ill bison from the same feedlot revealed 1 animal shedding M. bovis by the nasal route. No other pathogens were recovered from the pulmonary or laryngeal lesions; however, Mannheimia haemolytica was cultured from the nasal swabs of 2 clinically ill bison, although not from the animal found to be shedding M. bovis. Several other affected bison had swollen joints and exhibited lameness and a reluctance to move. Changes observed in dead and clinically ill bison from this feedlot are similar to what has been described in the literature as chronic pneumonia and polyarthritis syndrome in feedlot cattle caused by M. bovis. Based on the severity of the lesions, and the number of dead and affected animals, bison in a feedlot setting appear to exhibit sensitivity to infection with M. bovis.     

Genetic and functional characterization of the NanA sialidase from Clostridium chauvoei

ABSTRACT: Clostridium chauvoei is the causative agent of blackleg, a wide spread serious infection of cattle and sheep with high mortality. In this study we have analyzed the sialidase activity of the NanA protein of C. chauvoei and cloned the sialidase gene nanA. Sialidase is encoded as a precursor protein of 722 amino acids with a 26 amino acid signal peptide. The mature sialidase has a calculated molecular mass of 81 kDa and contains the carbohydrate binding module 32 (CBM32, or F5/8 type C domain), the sialic acid binding module CBM40 and the enzymatically active sialidase domain found in all pro- and eukaryotic sialidases. Sialidase activity does not require the CBM32 domain. The NanA protein is secreted by C. chauvoei as a dimer. The nanA gene was found to be conserved and sialidase activity was found in C. chauvoei strains isolated over a period of 50 years from various geographical locations. Antiserum directed against a recombinant 40 kDa peptide containing CBM40 and part of the enzymatically active domain of NanA neutralized the secreted sialidase activity of all C. chauvoei strains tested.