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PubMed1991

The effect of malnutrition on vaccination against Dermatophilus congolensis infection in ruminants.

Vaccination against Dermatophilus congolensis was carried out in groups of lambs raised on optimal or energy deficient diets. The groups differed significantly in weight, body condition score and plasma total protein and albumin. All animals were then challenged with D. congolensis in a dose response infection model. The vaccine was effective in the well nourished animals, reducing the number of affected lambs in the vaccinated group and the severity of the lesions and increasing the minimum dose required to cause infection. In contrast, all of the vaccinated energy-deficient lambs developed lesions. There was some evidence of vaccine effect in these animals but this was not as marked as that seen in the well nourished lambs. The malnourished lambs, vaccinated and non-vaccinated, took longer to heal than the well nourished groups. Resistance to challenge was not associated with serum antibodies or skin test reactivity to D. congolensis antigens.

Actinomycetales↗
PubMed1990

The effect of recent vaccination on the dose-response to experimental Dermatophilus congolensis infection in rabbits.

Dermatophilus congolensis infection of rabbits was used to investigate the effects of active immunity on epidermal challenge following vaccination. Rabbits (three groups of four) were vaccinated intradermally with live whole-cell preparations of D. congolensis strains SS18C and FD11 (groups SSVAC and FDVAC respectively); a third group (UNVAC) remained as unvaccinated controls. Two weeks after vaccination, separate 1.5-cm2 clipped and ether-swabbed skin sites were inoculated with a 10-fold dilution range (10(7) to 10(1) zoospores per cm2 of skin) of SS18C or FD11. Lesion scores at each site were calculated from the sum of individual scores (0 to 4+) for erythema, oedema and scab formation multiplied by the percentage of the inoculated area affected. A clear dose-response relationship between the size of inoculum and the severity of lesions was seen for both D. congolensis stains in the control group (UNVAC). In the SSVAC and FDVAC groups the lesions were less severe and developed more quickly. The number of zoospores required to cause infection in the vaccinated animals was up to 10,000-fold higher for homologous inoculated sites and 100-fold for heterologous sites. Serological analysis was carried out with an ELISA system. Vaccination and challenge resulted in increases in specific antibody against D. congolensis antigens. Cross-reacting antibody to the heterologous strain of D. congolensis used was demonstrated in both vaccinated groups but did not correlate with equal protection to homologous or heterologous challenge. The dose-response relationship demonstrated by this model enabled semi-quantitative analysis of the effects of vaccination on D. congolensis infective dose and severity of infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomycetales↗
PubMed2003

Genome-based design of a cell-free culture medium for Tropheryma whipplei.

Empirical approaches have guided the development of bacterial cultures. The availability of sequenced genomes now provides opportunities to define culture media for growth of fastidious pathogens with computer modelling of metabolic networks. A key issue is the possibility of growing host-dependent bacteria in cell-free conditions. The sequenced Tropheryma whipplei genome was analysed to identify specific metabolic deficiencies. We used this information to design a comprehensive medium that allowed three established T whipplei strains from culture with human cells and one new strain from a clinical sample to grow axenically. Genomic information can, therefore, provide sufficient clues for designing axenic media for fastidious and uncultured pathogens.

Actinomycetales↗
PubMed2004

Cavitary pneumonia secondary to Tsukamurella in an AIDS patient. First case and a review of the literature.

Tsukamurella is a Gram-positive, variable rod-shaped, weakly acid-alcohol-fast, non motile, aerobic bacterium that belongs to the genus Rhodococcus. Tsukamurella has been reported as a cause of infections in humans with immunosuppression and indwelling foreign bodies. It has also been isolated in one patient with AIDS (Acquired Immunodeficiency Syndrome) as a saprophytic organism. Optimal management of infections secondary to this micro-organism is still uncertain due to the paucity of cases. The combination of a beta-lactam and an aminoglycoside, along with removal of medical devices, appear to be the treatment of choice. We report the case of an AIDS patient who presented with multiple lung cavitary lesions secondary to Tsukamurella. This is the first case reported of Tsukamurella as a pathogenic agent in an AIDS patient. We also propose a successful oral antibiotic regimen with fluoroquinolone and rifampin to treat infections secondary to this uncommon micro-organism.

AIDS-Related Opportunistic Infections↗
PubMed1999

Immune responses to Dermatophilus congolensis infections.

Complex mechanisms underly the establishment of dermatophilosis, an exudative and proliferative skin disease of ruminants. This multicomponent system involves the bacterium Dermatophilus congolensis, transmission by various routes including flies, host genetic factors and immunosuppression by Amblyomma variegatum ticks. Here, Nick Ambrose and colleagues summarize recent evidence for an association between A. variegatum and severe chronic dermatophilosis in cattle. Breed-based differences in resistance to dermatophilosis are probably related to immunity to ticks or resistance to the immunosuppressive effects of ticks. Immunity to dermatophilosis might involve non-classic responses mediated by CD1 antigen presentation and gammadelta T cells. Progress towards vaccination is further complicated by strain-specific acquired immunity to D. congolensis.

Actinomycetales↗
PubMed1997

Dermatophilus congolensis: strain differences in expression of phospholipase activities.

Interactions between Dermatophilus congolensis strains and with other bacteria of known haemolytic activities were used to elucidate the complex nature of haemolytic activities present in various D. congolensis strains. This was further analysed by measuring their specific phospholipase activities against defined substrates by thin layer chromatography. D. congolensis strains demonstrated haemolytic interactions (synergistic or antagonistic) with other D. congolensis strains and also other species of bacteria. Most isolates expressed lyso-phospholipase-D activity, while various strains also expressed sphingomyelinase-D activity, phospholipase-A versus phosphatidylcholines and/or cephalins, phospholipase-D versus phosphatidylcholines or all these activities, under the culture conditions used.

Actinomycetales↗
PubMed1997

Electrophoretic and antigenic characterisation of Dermatophilus congolensis extracellular products.

Dermatophilus congolensis is the causative agent of bovine dermatophilosis and lumpy wool in sheep. Two field isolates of D. congolensis, one each from a cow in Ghana and a sheep in Scotland, were cultured for 24-72 h in a synthetic medium based on RPMI-1640. Culture filtrates were examined by SDS-PAGE and considered to contain extracellular products released by growing hyphae and filaments. Electrophoretic profiles of culture filtrates of the two isolates contained common bands and bands that were unique to each isolate. The composition of extracellular products altered with increasing culture periods indicating that specific products were released at different stages of growth. Culture filtrate prepared in the presence of serine protease and metalloprotease inhibitors contained more and better defined bands than that prepared without protease inhibitors indicating the presence of proteases in culture filtrates. Western blot analysis of extracellular products using a panel of sera showed that the two isolates from different host species and distant geographical locations contained cross-reactive antigens. Natural and experimental infections stimulated antibody responses to antigens in culture filtrates, sera from animals that were disease free but in-contact with dermatophilosis-infected animals also contained antibodies to extracellular antigens. The antigens recognised by most sera had molecular weights of 200 kDa in the bovine isolate, 170 kDa in the ovine isolate and 67, 27 and 52-55 kDa in both isolates. The number of antigenic bands of both isolates was positively correlated with the intensity of challenge and the severity of infection: antibodies in sera from disease-free cattle in Ghana recognised more antigens than sera from disease-free sheep in Scotland and more antigens were recognised by sera from chronically-infected Ghanaian cattle than by sera from experimentally-infected calves and sheep. The latter developed antibodies to antigens of 27 and 24 kDa during the course of infection. The electrophoretic profiles of extracellular products of D. congolensis are less complex than those of other structures of the bacterium yet they exhibit differences between the two isolates. Extracellular products contain antigens recognised by sera from naturally exposed and experimentally-infected animals that may be involved in immunity to D. congolensis or immunopathogenesis of dermatophilosis.

Actinomycetales↗
PubMed1998

Preliminary characterisation of extracellular serine proteases of Dermatophilus congolensis isolates from cattle, sheep and horses.

Dermatophilus congolensis is a filamentous branching actinomycete that causes dermatophilosis, an exudative dermatitis in ruminants. The pathogenesis of this disease is poorly understood and virulence factors of D. congolensis have not been characterised. Culture filtrate (CF) of 14 D. congolensis isolates from cattle, 15 from sheep and four from horses were examined for proteolytic activity using azocasein as a non-specific substrate. The isolates were from a variety of geographical locations. All the isolates examined produced extracellular proteolytic activity. CF from 24 and 48 h cultures and from first and third passages contained proteases. Proteolytic activity was greatest in neutral to alkaline pH (pH 7-10). CF of bovine isolates contained more proteolytic activity than that of ovine isolates. Furthermore, in substrate SDS-PAGE gels containing azocasein the number of proteolytic bands and their molecular weights in CF of bovine, ovine and equine isolates were different, giving distinctive band patterns for isolates from each host species. Three out of four bovine isolates from Antigua gave a fourth band pattern. Bands of equivalent molecular weights to the proteases could not be identified in silver stained SDS-PAGE gels of CF. Serine protease inhibitors had a concentration-dependent inhibitory effect on proteolytic activity in CF and inhibited activity of all proteolytic bands in substrate gels. With the exception of EDTA which had a variable-enhancing effect on activity, inhibitors of other classes of protease had no effect on activity. We conclude that D. congolensis produces a number of extracellular alkaline serine proteases, our results suggest the presence of host-specific variation between isolates and to a lesser extent between isolates from the same host species.

Actinomycetales↗
PubMed1999

A comparison of extracted proteins of isolates of Dermatophilus congolensis by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western blotting.

Antigenic diversity within a collection of 18 isolates of Dermatophilus congolensis from different Continents was examined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and by Western blotting with sera from cattle with clinical dermatophilosis using whole cell extracts obtained by three methods and one extract of extracellular products of D. congolensis. One of the methods involving the release of a lysostaphin-solubilized protein (LSP) of whole cells of D. congolensis revealed a number of discrete and easily-identifiable bands in SDS-PAGE which were found suitable for characterizing protein patterns and was, therefore, subsequently used for a comparative analysis of the proteins of all the D. congolensis isolates. Six electropherotypes (ET) of D. congolensis were identified among the 18 isolates using the protein profiles based on the presence of four protein bands at Molecular weights (MW) 62, 28, 17.4 and 16.4 kDa. The ETs were found among isolates from different animal species and from different sources with ET1 consisting of three bovine and two equine isolates; ET2, two bovine and three ovine isolates; ET3, two bovine isolates; ET4, two bovine isolates; ET5, one bovine and one ovine isolates and ET6, two bovine isolates. Immunoblotting of the extracts of D. congolensis isolates with sera from cattle with clinical dermatophilosis infection demonstrated protein bands of MW ranging from 9 kDa to 188 kDa. Sera from chronic dermatophilosis infection demonstrated a 28 kDa protein which was immunodominant in the LSP extracts of all the 18 isolates of D. congolensis tested while sera from mild infections demonstrated mainly the 62 kDa protein in the same extracts. However, many protein bands were demonstrated in surface membrane (TSMP) and extracellular protein extracts with sera from only mildly infected animals. The protein patterns observed in all isolates of D. congolensis revealed global antigenic similarities and distinct differences among isolates which could not be associated with either geographic, climatic or host factors. Also sera from infected animals from endemic regions of dermatophilosis could not differentiate isolates of D. congolensis. This suggests the possibility that such sera must have come from animals that had been infected by a multitude of D. congolensis strains present in the herd environment and strains an animal could have come across during the 'ritual' annual cross-country migration of the cattle herds.

Actinomycetales↗
PubMed2003

Cloning and sequencing an unknown gene of Tropheryma whipplei and development of two LightCycler PCR assays.

Whipple's disease is a rare infectious illness that can affect any organ system in the body. It is caused by Tropheryma whipplei, a Gram-positive rod-shaped bacterium with a high G + C content, classified within the actinobacteria. For decades, laboratory detection has been based on microscopy and the periodic acid-Schiff (PAS) staining of biopsies. Recently, PCR has become a useful tool to detect T. whipplei DNA in various clinical specimens. However, a positive PCR result does not confirm Whipple's disease as it has been shown that asymptomatic persons can harbor T. whipplei DNA. Since there is not yet much known about the genome of T. whipplei, genome-walking represents a convenient method to determine unknown gene sequences. Starting from a RAPD fragment we have sequenced and cloned an open reading frame (ORF) of 843 bp. Two real-time PCR assays targeting the ORF fragment and the 16S rRNA gene, respectively, were developed. Compared to a conventional 16S rRNA PCR system the ORF LightCycler assay proved to be very specific (100%) but not sufficiently sensitive (62.4%). In contrast, the 16S rRNA LightCycler assay showed a sensitivity of 95.7% and a specificity of 97.8%. Thus, the 16S rRNA gene assay but not that targeting the new ORF is a suitable alternative to conventional PCR methods.

Actinomycetales↗
PubMed2000

Emergent causes of placentitis and abortion.

The clinical signs, laboratory findings, diagnosis, epidemiology, treatment, and prevention and control of two emerging causes of placentitis and abortion in horses are described in this article. Leptospirosis has been reported as a significant cause of fetal loss in horses in Kentucky, Northern Ireland, and England. Most abortions result from infection by serovars kennewicki or bratislava. Nocardioform placentitis has become the most common cause of placentitis in central Kentucky horses. Nocardioform placentitis is associated with infection by unnamed, gram-positive, filamentous, branching bacteria, and is characterized by distinctive changes in the placental membranes.

Abortion, Veterinary↗
PubMed1998

Phospholipase D-neutralization in serodiagnosis of Arcanobacterium haemolyticum and Corynebacterium pseudotuberculosis infections.

Phospholipase D (PLD) neutralization was used to examine sera of humans (n = 40) with a spontaneous infection by Arcanobacterium haemolyticum, sheep and goats (n = 76 and 79 respectively) with a spontaneous infection by Corynebacterium pseudotuberculosis, mice (n = 26) experimentally immunized with PLD from A. haemolyticum (PLD-A) and mice (n = 28) experimentally immunized with PLD from C. pseudotuberculosis (PLD-C). PLD-A and PLD-C were also used as neutralizing antigens. A positive result of neutralization was due to an inhibition of the haemolytic synergism with the equi factor from Rhodococcus equi. The titres of sera neutralizing the homologous PLD were always significantly higher than those neutralizing the heterologous PLD. The proportion of sera that were able to neutralize the homologous PLD in sheep, goats and mice immunized with PLD-A significantly exceeded the proportion of sera that neutralized the heterologous PLD. The antigenic properties of PLD-A and PLD-C were similar but not identical.

Actinomycetales↗
PubMedDate not supplied

Cloning of genes that have environmental and clinical importance from rhodococci and related bacteria.

Generalised and specialised transduction systems were developed for Rhodococcus by means of bacteriophage Q4. The latter was used in conjunction with DNA from an unstable genetic element of R. rhodochrous to construct resistance plasmids which replicate in strains of R. equi, R. erythropolis and R. rhodochrous. One of the plasmids, pDA21, was joined with Erythropolis coli suicide vector pEcoR251 to obtain shuttle plasmids maintained in both rhodococci and E. coli. Conjugation between these rhodococcal strains demonstrated all were interfertile with each other and that some of the determinants for this were located on the unstable genetic element. Plasmids derived from this element, such as pDA21, carried the conjugative and self-incompatibility capacities; deletion analysis revealed that DNA necessary for self-incompatibility overlapped with that for arsenic resistance. Rifampicin is one of the principal chemotherapeutic agents used to treat infections by rhodococci and related organisms. The genes responsible for two types of inactivation have been cloned. The sequence of the R. equi DNA responsible for decomposition of the antibiotic strongly resembled those of monooxygenases acting upon phenolic compounds, consistent with the presence of a naphthalenyl moiety in the rifampicin molecule. Antibiotic resistance conferred by the gene was surprisingly specific to the semisynthetic compounds rifampicin (150-fold increase) and rifapentine (70-fold). Similar specificity was observed with the other inactivation gene cloned, which ribosylates rifampicin at the 23-hydroxyl position. A 60-bp sequence upstream of the monooxygenase and ribosylation genes is strikingly similar suggesting a shared pattern of regulation. Rhodococcal arsenic resistance and azo dye degradation genes have been cloned and characterised.

Actinomycetales↗