Cultural and biochemical characterization of Actinobacillus and Actinobacillus-like species from ram lambs with epididymitis

Cellular, colonial, cultural, and biochemical characteristics of 25 field strains of gram-negative pleomorphic bacilli from rams with epididymitis were compared with Actinobacillus actinomycetemcomitans American Type Culture Collection (ATCC) strain 29522 and Actinobacillus seminis ATCC strain 15768. Three field strains were identified as A. actinomycetemcomitans, 15 as A. seminis, and 2 as Haemophilus agni; however, 5 strains (3 in group A and 2 in group B) were not identified as species in the genera Actinobacillus, Haemophilus, or Pasteurella based on the taxonomic criteria in Bergey's manual of systematic bacteriology. The 5 Actinobacillus-like organisms in groups A and B were predominantly gram-negative coccobacilli and exhibited less pleomorphism than the 2 Actinobacillus species. The colonial morphologies of groups A and B were similar to the 2 Actinobacillus species but were smaller in diameter and had a pale yellow color. Groups A and B, like the actinobacilli, were facultative anaerobic and capnophilic, did not grow on MacConkey agar, and were catalase-positive and oxidase-positive. Group A reduced nitrate but group B did not. The A. seminis strains utilized ornithine, and group A utilized arginine; but group B did not utilize either ornithine or arginine. All strains failed to utilize lysine or tryptophane. All strains produced acid but no gas from glucose, and the utilization of other carbohydrates varied markedly both between and within the 5 groups of bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)     

Production and preliminary characterization of monoclonal antibodies to Actinobacillus sp isolated from epididymitis lesions in a ram

A panel of 55 monoclonal antibodies to an Actinobacillus sp isolate (As8C strain) cultured from the epididymides of an infected ram was produced. Cell lines producing 5 of these antibodies were cloned and expanded by hybridoma tumor production in Balb/c mice. An isotype profile revealed that 1 cloned antibody belonged to the immunoglobulin (Ig) M class and the 4 remaining antibodies belonged to the IgG class. Within the IgG class, 1 clone produced IgG1, 1 clone produced IgG2a, and 2 clones produced IgG2b. Ascites fluid antibody titers from the cloned hybridomas ranged from 6,400 to 51,200, as determined by enzyme-linked immunosorbent assay. Specificity of the antibodies to target As8C antigens could be demonstrated by enzyme-linked immunosorbent assay inhibition. Ascites fluid from 2 clones contained antibodies that agglutinated As8C. Two additional clones produced antibodies capable of only partial agglutination, whereas 1 clone produced antibody that did not agglutinate As8C. The indirect fluorescent antibody test revealed that target antigens for at least 4 of the 5 monoclonal antibodies were most likely located on the bacterial cell surface. Antigens were extracted from As8C, using 5 surface active chemicals. An attempt to immunoprecipitate these antigens in agarose by reacting individual extracts with each of the antibodies was unsuccessful.     

Use of monoclonal antibodies to identify outer membrane antigens of Actinobacillus species

Three monoclonal antibodies (LG17, LG30, and LG33) were used to identify outer membrane antigens of Actinobacillus sp (As8C isolate) cultured from the epididymides of an infected ram lamb. Specificity of the 3 antibodies to As8C antigens was determined by use of bacterial agglutination, the enzyme-linked immunosorbent assay, and the indirect fluorescent antibody test. Results of immunoelectron microscopy confirmed that each antibody was specific for epitopes on As8C outer membrane antigens. Evaluation by use of enzyme-linked immunoelectrotransfer blot indicated that target antigens for LG17 and LG33 antibodies had molecular weights of 10 kilodaltons and 43 kilodaltons, respectively. Multiple-band staining was observed with the LG33 antibody. The target antigen for the LG30 antibody could not be discerned by use of enzyme-linked immunoelectrotransfer blot. For each of the 3 monoclonal antibodies, enzyme-linked immunosorbent assay titers were obtained for Actinobacillus seminis, A actinomycetemcomitans, and 10 field isolates of Actinobacillus spp. Target antigens for LG17 and LG30 antibodies occurred infrequently or were absent on these bacteria. However, the target antigen for the LG33 antibody was shared by Actinobacillus seminis, A actinomycetemcomitans, and the 10 field isolates of Actinobacillus spp, indicating some diversity of outer membrane antigens between isolates.     

Immunoproteomic analyses of outer membrane antigens of Actinobacillus pleuropneumoniae grown under iron-restricted conditions

Actinobacillus pleuropneumoniae, a bacterial pathogen of swine and agent of porcine pneumonia, causes a highly infectious disease of economic importance in the pig industry. Commercial vaccines for A. pleuropneumoniae include whole-cell bacterins and second generation subunit vaccines but they only confer partial protective immunity. Our search for new vaccine candidates identified antigens that are expressed during conditions that mimic infection; the outer membrane (OM) proteome of A. pleuropneumoniae serotype 5b was examined under iron restriction. Quantitative profiling by 2D-DiGE technology revealed that iron restriction induced expression of previously described transferrin binding proteins (TbpA, TbpB) plus four lipoproteins including spermidine/putrescine binding periplasmic protein 1 precursor (PotD2). Immunoproteomic analyses with antisera from na?ve animals and from infected pigs were able to differentiate antigens within the OM proteome that were specifically recognized during A. pleuropneumoniae infection. Immunoblots of iron-restricted profiles detected PotD2, heme-binding protein A (HbpA), and capsule polysaccharide export protein (CpxD) as well as surface antigens TbpA, TbpB, and OmlA. These data identify OM proteins that demonstrate immunogenicity and upregulation under conditions mimicking infection, providing emphasis on lipoproteins as an important class of antigens to exploit for vaccine development for A. pleuropneumoniae.     

Identification and preliminary characterization of a 75-kDa hemin- and hemoglobin-binding outer membrane protein of Actinobacillus pleuropneumoniae serotype 1

The reference strains representing serotypes 1 to 12 of Actinobacillus pleuropneumoniae biotype 1 were examined for their ability to utilize porcine hemoglobin (Hb) or porcine hemin (Hm) as iron sources for growth. In a growth promotion assay, all of the reference strains were able to use porcine Hb, and all strains except 2 were able to use porcine Hm. Using a preliminary characterization procedure with Hm- or Hb-agarose, Hm- and Hb-binding outer membrane proteins (OMPs) of approximately 75 kDa were isolated from A. pleuropneumoniae serotype 1 strain 4074 grown under iron-restricted conditions. Matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) analysis revealed a number of common tryptic peptides between the Hb-agarose- and Hm-agarose-purified 75 kDa OMPs, strongly suggesting that these peptides originate from the same protein. A database search of these peptide sequences revealed identities with proteins from various Gram-negative bacteria, including iron-regulated OMPs, transporter proteins, as well as TonB-dependent receptors. Taken together, our data suggest that A. pleuropneumoniae synthesizes potential Hm- and Hb-binding proteins that could be implicated in the iron uptake from porcine Hb and Hm.     

Molecular characterization of the major outer membrane protein of Haemophilus somnus

The major outer membrane protein (MOMP) of Haemophilus somnus shows antigenic and molecular mass diversity that forms the basis of a preliminary grouping system for H. somnus strains. In this study, the gene encoding MOMP of H. somnus strain 8025 was cloned in three overlapping fragments by PCR techniques, and then sequenced. The gene consists of a 1164-bp open reading frame encoding a deduced 380-amino acid protein with a 19-amino acid signal sequence, giving a mature protein with a calculated molecular mass of 39,913 Da. Significant homology was found between MOMP and porin protein sequences of bacteria in Pasteurellaceae species. When expressed in Escherichia coli, the protein from the MOMP gene directed by the T7 promoter was identical in size (approximately 40 kDa) to native MOMP and reacted with MOMP-specific antibodies. Comparisons of the MOMP gene sequences from six unrelated strains of H. somnus to that of strain 8025 revealed that the genes of three MOMP type 1 strains were highly conserved with that of strain 8025 in length and sequence. However, two MOMP type 3c strains and one MOMP type 3a strain differed markedly from the MOMP of strain 8025 in their 3'-terminal halves. Their deduced MOMP amino acid sequences differed in sequence (3c, 80.5 and 82.7% identity; 3a, 62.4% identity) and in length (3c, 384 and 376; 3a, 316), indicating that the molecular differences are the basis of antigenicity and molecular mass differences of H. somnus MOMP. In the predicted MOMP secondary structure, the variable sequences primarily mapped to putative surface-exposed loops, and a variable and surface-exposed epitope of MOMP-specific antibody was identified in the seventh-largest loop. These findings are useful for understanding the structural and immunological characteristics of H. somnus.     

Immunological characterization of the major outer membrane protein of Haemophilus somnus

Antigens and molecular mass diversity of the Haemophilus somnus major outer membrane protein (MOMP) were investigated. The molecular mass of the MOMP of 53 strains of H. somnus varied from 43 to 33 kDa and four MOMP MAb reactivity patterns were detected in immunoblot analysis and immunodot assay. The molecular mass and MAb reactivity data were used for preliminary grouping of H. somnus strains. Disease strains fell into groups 1 and 3, including two of three Group 3 subgroups, whereas strains from asymptomatic carriers were found in all the four groups and three subgroups. Immunoblot analysis with convalescent phase serum showed strain specific reactivity with MOMPs from three isolates used to reproduce disease in cattle. The reaction with the MOMP was only detectable at dilutions of 1:100 or less, whereas the same convalescent sera showed strong reactivity at dilutions of 1:1000 (or more) with other H. somnus antigens. The data suggest that the bovine immune response to the MOMP during infection is weak and is directed to antigenically variable determinants in a strain-specific manner. This may be important in evaluating the role of the antibody response to MOMPs in protective immunity.     

Characterisation of the outer membrane protein antigens of British field isolates of Moraxella bovis

Outer membranes of a single isolate of Moraxella bovis were prepared and their purity evaluated by a comparison of the iodinated proteins from whole cells and on outer membranes. The protein patterns of the outer membranes of 10 isolates were examined by SDS-polyacrylamide gel electrophoresis, and the antigenic relationship between proteins of different isolates determined by immunoblotting, using antiserum produced against the outer membrane of the single isolate of M. bovis. The overall protein pattern of the different isolates was similar although not identical, but, significantly, only three separate immunogenic proteins were common to all the isolates under examination.     

胸膜肺炎放线杆菌外膜脂蛋白的原核表达及免疫原性分析

以猪传染性胸膜肺炎放线杆菌(APP)血清1型SC-A株基因组DNA为模板,用PCR扩增外膜脂蛋白(OML)基因特异片段,并克隆于pMD18-T中,经酶切及核苷酸序列分析鉴定后,亚克隆于原核表达载体pET-32 a(+),成功构建了重组表达载体pET-mOML。以此转化大肠埃希氏菌BL21(DE3),IPTG诱导表达,SDS-PAGE鉴定,表达的融合蛋白(TRX-mOML)分子质量约为60 ku,表达产物主要以包涵体形式存在,采取非变性电泳方法对蛋白进行纯化,经ELISA检测,重组OML免疫小鼠可产生较高水平的抗OML抗体,这表明重组OML有较好的免疫原性。     

Molecular serotyping and antimicrobial resistance profiles of Actinobacillus pleuropneumoniae isolated from pigs in South Korea

Background: Actinobacillus pleuropneumoniae (APP) causes porcine pleuropneumonia (PP).

Objective: Serotypes and antimicrobial resistance patterns in APP isolates from pigs in Korea were examined.

Methods: Sixty-five APP isolates were genetically serotyped using standard and multiplex PCR (polymerase chain reaction). Antimicrobial susceptibilities were tested using the standardized disk-agar method. PCR was used to detect β-lactam, gentamicin and tetracycline-resistance genes. The random amplified polymorphic DNA (RAPD) patterns were determined by PCR.

Results: Korean pigs predominantly carried APP serotypes 1 and 5. Among 65 isolates, one isolate was sensitive to all 12 antimicrobials tested in this study. Sixty-two isolates was resistant to tetracycline and 53 isolates carried one or five genes including tet(B), tet(A), tet(H), tet(M)/tet(O), tet(C), tet(G) and/or tet(L)-1 markers. Among 64 strains, 9% and 26.6% were resistance to 10 and three or more antimicrobials, respectively. Thirteen different antimicrobial resistance patterns were observed and RAPD analysis revealed a separation of the isolates into two clusters: cluster II (6 strains resistant to 10 antimicrobials) and cluster I (the other 59 strains).

Conclusion: Results show that APP serotypes 1 and 5 are the most common in Korea, and multi-drug resistant strains are prevalent. RAPD analysis demonstrated that six isolates resistant to 10 antimicrobials belonged to the same cluster.     

Serological characterization of Actinobacillus pleuropneumoniae strains isolated from pigs in Quebec.

A total of 3306 isolates of A. pleuropneumoniae originating from lung tissues of pigs that died of acute pleuropneumonia and 140 isolates recovered from tonsils or nasal cavities of apparently healthy pigs from chronically infected herds were serotyped. Various serotyping methods, such as slide agglutination, tube agglutination, ring precipitation, coagglutination, immunodiffusion, indirect hemagglutination and counterimmunoelectrophoresis either alone or in combination were used. The techniques used for serotyping continued to evolve during the last 10 years depending on the problem encountered in serotyping. Antisera prepared in rabbits against formalinized whole cell suspensions of reference strains of A. pleuropneumoniae of serotypes 1 to 12 were employed for serotyping. Serotype 1 was predominant ranging from 55 to 87% from year to year during the last 10 years with an average prevalence of 68%. Serotype 5 was second in prevalence ranging from 9 to 30% with a mean of 23%. Both subtypes of serotype 5 (5a and 5b) were present in Quebec. Serotypes 3, 6, 7, 8, 10 and 12 were isolated in small numbers together accounting for about 9%. Serotypes 4, 9 and 11 were not present. Cross-reactions were observed among isolates of serotypes 3, 6 and 8, and 1, 9 and 11 and were easily differentiated from each other by quantitation of type and group specific antigens by coagglutination and immunodiffusion tests. Serotypes 1, 5 and 7 were isolated most frequently from tonsils of pigs from chronically infected herds. Prevalence of different serotypes in different countries has also been reviewed.     

Characterization of outer membrane protein-enriched extracts from Pasteurella multocida isolated from turkeys

Outer membrane protein (OMP)-enriched extracts of avian strains of Pasteurella multocida were examined by use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Culture medium did not have a significant effect on the OMP profiles of strains of P multocida examined; however, in vivo propagation had an appreciable effect on the OMP profile composition of the reference strain P-1059. Such bacteria, expressed several additional OMP in the 27-kD, 48-kD, 56-kD, 60-kD, 80-kD, and 94-kD molecular mass regions. These OMP were not detected in the electrophorogram of strain P-1059 grown in vitro. The OMP profiles of reference strains of the 16 serotypes of P multocida did not identify any serotype-specific protein markers. Field strains of serotype A:3 had variation in OMP profiles and did not express OMP that all were identical to that expressed by the reference strain P-1059. The live attenuated CU and M9 bacterial vaccine strains expressed strain-specific OMP markers of 48-kD and 45-kD molecular masses, respectively. These strain-specific OMP markers may be used to differentiate these strains from virulent field strains that are of the same serotype and isolated from turkeys that have succumbed to pasteurellosis as a result of vaccine-related reactions or breakdown in immunity.     

维氏气单胞菌JLL-1株外膜蛋白的原核表达及其免疫原性检测

为研究维氏气单胞菌(Aeromonas veronii)外膜蛋白(outer membrane protein,OMP)的免疫原性,本试验对A.veronii的OmpAⅠ基因进行克隆,构建了原核表达质粒pET-30a(+)-OmpAⅠ,并转入大肠杆菌BL21(DE3),将其表达后纯化重组蛋白,利用SDS-PAGE和Western blot分析鉴定。将灭活苗、弗氏佐剂(OmpAⅠ)、纯化蛋白及PBS缓冲液分别免疫鲤鱼后,检测每周各试验组鱼体血清非特异性免疫指标(酸性磷酸酶、碱性磷酸酶、超氧化物歧化酶活力)及特异性IgM抗体水平变化情况,并于加强免疫2周后对鲤鱼进行攻毒保护性试验。结果显示:重组蛋白免疫鲤鱼后能产生明显的免疫反应,保护率在77%以上;受免鲤鱼血清中IgM抗体水平、酸性磷酸酶、碱性磷酸酶及超氧化物歧化酶活力活力较对照组有显著提高。结果表明,重组蛋白OmpAⅠ具有较好的免疫原性和保护作用,为进一步研究外膜蛋白基因工程疫苗的开发奠定基础。     

Phenotypic and genotypic characterization of Actinobacillus suis sensu stricto isolated from a dairy calf

The species of the genus Actinobacillus have so far been associated with specific animal hosts, and A. suis sensu stricto, an opportunistic pathogen of swine, is rarely isolated from ruminants. We describe here the isolation of A. suis sensu stricto from a newborn calf that died on a dairy farm in Japan. Identification of the isolate was performed by phenotypic and genotypic characterization, with the latter consisting of nucleotide sequence analyses of the 16S rRNA gene plus three housekeeping genes, rpoB, infB and recN.     

Improved protection of swine from pleuropneumonia by vaccination with proteinase K-treated outer membrane of Actinobacillus (Haemophilus) pleuropneumoniae

The immunogenic and protective potentials of an outer membrane-enriched fraction (OM) from a serotype 5 strain of Actinobacillus (Haemophilus) pleuropneumoniae (APP) and the same OM degraded with proteinase K or periodate were evaluated in swine. Groups of pigs were vaccinated with two doses of OM, proteinase K-treated OM (P-OM), periodate-treated OM (PI-OM), or placebo vaccine and challenged intranasally with the homologous strain of APP. Results from triplicate experiments indicated that proteinase K treatment of OM resulted in an improved efficacy. This improved efficacy of P-OM vaccine over untreated OM vaccine was evidenced not only by less severe lung lesions in P-OM vaccinated pigs but also by significant reduction (P less than 0.05) in the number of P-OM vaccinated pigs which developed lung lesions upon challenge with APP. Assessment of sera from vaccinated animals by immunoblotting, complement fixation test, or ELISA indicated that the immunogenicity of some but not all protein or carbohydrate components were reduced (or eliminated) by proteinase K and periodate treatments respectively.     

Effects of immunization against two inhibin antigens on daily sperm production and hormone concentrations in ram lambs

The gonadal hormone inhibin regulates daily sperm production (DSP) indirectly through negative feedback control of FSH secretion and may also affect DSP via direct actions within the testis. Studies attempting to increase DSP through the immunization against inhibin have yielded equivocal results. The current study compared 2 inhibin antigens for effects on DSP and hormone secretion. Hampshire ram lambs (BW = 42 +/- 2 kg; age = 113 +/- 3 d) were assigned randomly to 3 groups: 1) control (n = 4); 2) alpha-peptide conjugate (PTC, n = 6); and 3) alpha-subunit (SUB, n = 6). Antigen PTC consisted of an alpha-inhibin, N-terminal, 25-amino acid peptide conjugated to ovalbumin. Antigen SUB was the complete inhibin alpha-subunit. Lambs were immunized on d 0 (June 19, 2006), 18, 38, and 63. Body weight was recorded on immunization days and scrotal circumference on d 63. Blood samples were collected on d 0, 7, 14, 18, 28, 35, 38, 49, 56, 63, and 70. Rams were slaughtered on d 71. Testes were weighed, and parenchyma was obtained for DSP determination. Plasma alpha-inhibin antibody titer and LH, FSH, and testosterone concentrations were measured. alpha-Inhibin antibody titer was first detectable on d 14 in both PTC- and SUB-immunized ram lambs and generally increased thereafter. Mean DSP per gram of testis (DSP/g) was increased (P < 0.01) 26% in PTC- and SUB-immunized ram lambs over that in control ram lambs. Total DSP per ram lamb and testes weight did not differ among the 3 treatment groups. Variation in DSP per ram lamb and testes weight were greater (P = 0.05) in PTC- and SUB-immunized ram lambs than in control ram lambs. Plasma FSH concentrations were similar in PTC- and SUB-immunized ram lambs. Immunization against either alpha-inhibin antigen did not alter LH, testosterone, BW, or scrotal circumference. Findings indicate that 1) the 2 alpha-inhibin antigens increase DSP/g to similar extents; 2) alpha-inhibin antibody may act at least in part through an intratesticular mechanism because DSP/g was increased in some animals without concomitant increases in FSH; and 3) immunization against alpha-inhibin may affect testes weight by actions independent of those that regulate DSP/g.     

Outer membrane protein profiles of Edwardsiella ictaluri from fish.

Outer membrane proteins (OMP) prepared with sodium N-lauroyl sarcocinate (SLS) from 33 Edwardsiella ictaluri isolates from fish were examined by electrophoresis. Twenty-eight isolates from channel catfish (Ictalurus punctatus) had similar OMP profiles. Ten bands (71 kilodaltons [kD] to 19.5 kD) were identified in all isolates from channel catfish. One major 35-kD protein comprised most of the protein content of the outer membrane of isolates from channel catfish. Differences existed among isolates in the amount of protein within minor OMP bands. Edwardsiella ictaluri ATCC 33202 contained larger quantities of the 38.5- and 37-kD proteins than did the other isolates. Outer membrane protein profiles of E ictaluri derived from Bengal danio (Danio devario) and walking catfish (Clarias batrachus) were identical to OMP profiles of isolates from channel catfish. In contrast, OMP profiles from single isolates from green knife fish (Eigemannia virescens) and white catfish (Ictalurus catus) were different. Variations in incubation time, SLS extraction time, SLS extraction number, and in vivo and in vitro passage had no effect on the OMP profile of E ictaluri ATCC 33202. An increase in duration of sample solubilization did affect the OMP profile of E ictaluri ATCC 33202 by decreasing the amount of protein in 52-, 46-, and 43.5-kD bands. Accompanying the decrease were increased staining intensity in the 31.5- and 28.5-kD bands and the appearance of 4 new bands (34, 33, 25.5, and 22.5 kD). Edwardsiella ictaluri, a gram-negative bacterium in the family Enterobacteriaceae, is the cause of enteric septicemia of catfish.(ABSTRACT TRUNCATED AT 250 WORDS)