Feline leprosy: two different clinical syndromes

Feline leprosy refers to a condition in which cats develop granulomas of the subcutis and skin in association with intracellular acid-fast bacilli that do not grow on routine laboratory media. In this study, the definition was extended to include cases not cultured, but in which the polymerase chain reaction (PCR) identified amplicons characteristic of mycobacteria. Tissue specimens from 13 such cases from eastern Australia were obtained between 1988 and 2000. This cohort of cats could be divided into two groups on the basis of the patients' age, histology of lesions, clinical course and the sequence of 16S rRNA PCR amplicons. One group consisted of four young cats (less than 4 years) which initially developed localised nodular disease affecting the limbs. Lesions progressed rapidly and sometimes ulcerated. Sparse to moderate numbers of acid-fast bacilli were identified using cytology and/or histology, typically in areas of caseous necrosis and surrounded by pyogranulomatous inflammation. Organisms did not stain with haematoxylin and ranged from 2 to 6 microm (usually 2 to 4 microm). Mycobacterium lepraemurium was diagnosed in two cases based on the sequence of a 446 bp fragment encompassing the V2 and V3 hypervariable regions of the 16S rRNA gene a different sequence was obtained from one additional case, while no PCR product could be obtained from the remaining case. The clinical course was considered aggressive, with a tendency towards local spread, recurrence following surgery and development of widespread lesions over several weeks. The cats resided in suburban or rural environments. A second group consisted of nine old cats (greater than 9 years) with generalised skin involvement, multibacillary histology and a slowly progressive clinical course. Seven cats initially had localised disease which subsequently became widespread, while two cats allegedly had generalised disease from the outset. Disease progression was protracted (compared to the first group of cats), typically taking months to years, and skin nodules did not ulcerate. Microscopically, lesions consisted of sheets of epithelioid cells containing large to enormous numbers of acid-fast bacilli 2 to 8 microm (mostly 4 to 6 microm) which stained also with haematoxylin. A single unique sequence spanning a 557 bp fragment of the 16S rRNA gene was identified in six of seven cases in which it was attempted. Formalin-fixed paraffin-embedded material was utilised by one laboratory, while fresh tissue was used in another. The same unique sequence was identified despite the use of different primers and PCR methodologies in the two laboratories. A very slow, pure growth of a mycobacteria species was observed on Lowenstein-Jensen medium (supplemented with iron) and semi-solid agar in one of three cases in which culture was attempted at a reference laboratory. Affected cats were domicile in rural or semi-rural environments. These infections could generally be cured using two or three of rifampicin (10-15 mg/kg once a day), clofazimine (25 to 50 mg once a day or 50 mg every other day) and clarithromycin (62.5 mg per cat every 12 h). These findings suggest that feline leprosy comprises two different clinical syndromes, one tending to occur in young cats and caused typically by M lepraemurium and another in old cats caused by a single novel mycobacterial species.

Detection of Mycobacterium bovis in bovine clinical specimens using real-time fluorescence and fluorescence resonance energy transfer probe rapid-cycle PCR

Nucleic acid sequence capture extraction was coupled with LightCycler PCR amplification and product detection using real-time fluorescence for rapid, definitive detection of Mycobacterium bovis in lymph node specimens from 38 cattle with bovine tuberculosis lesions. PCR amplification of sequence-captured DNA using both a conventional heating block thermocycler and a LightCycler thermocycler was compared with culture and histopathological analyses. Conventional PCR enabled detection of 26 of 28 culture-positive specimens (93%) in approximately 9 h, and the LightCycler PCR detected 20 of 28 culture-positive specimens (71%) in only 30 min. Specific confirmation of Mycobacterium tuberculosis complex DNA was achieved by LightCycler PCR amplification using Syb Green 1 and an M. tuberculosis complex-specific Cy5-labeled fluorescence resonance energy transfer probe. The system described here enabled rapid and specific laboratory confirmation of bovine tuberculosis, and this is the first report of the detection of M. bovis in tissues using LightCycler PCR. The fluorescence technology used in the study has potential to allow development of a high-throughput molecular diagnostic test for bovine tuberculosis.

Treatment of canine leproid granuloma syndrome: preliminary findings in seven dogs

OBJECTIVE

To determine effective treatment strategies for patients with refractory canine leproid granuloma syndrome.

DESIGN

Multi-institutional retrospective/prospective case series using client-owned dogs.

PROCEDURE

Seven dogs (four Boxers, one Dobermann, one Bullmastiff and one Bullmastiff cross-bred; ages 3 to 11 years) with leproid granulomas were treated successfully using a variety of treatment regimens. These cases were recruited because: lesions were either widely distributed over the dog; progressive, despite routine therapy, or were associated with particularly disfiguring lesions. The treatment regimen evolved during the course of the clinical study.

RESULTS

Combination therapy using rifampicin (5 to 15 mg/kg p.o., every 24 h) and clarithromycin (8 to 24 mg/kg p.o. daily; dose divided every 8 or every 12 h) was used most frequently and proved to be effective and free from side effects. Total daily doses of clarithromycin in excess of 14 mg/kg were considered optimal and long treatment courses, in the order of 1 to 3 months, were used. Combination therapy using rifampicin (25 mg/kg; that is, higher than the recommended dose) and clofazimine was effective in one case, but resulted in hepatotoxicity. A topical formulation of clofazimine in petroleum jelly was used as an adjunct to oral rifampicin and doxycycline in another patient treated successfully.

CONCLUSION

Based on our evolving clinical experience, a combination of rifampicin (10 to 15 mg/kg p.o., every 24 h) and clarithromycin (15 to 25 mg/kg p.o. total daily dose; given divided every 8 to 12 h) is currently recommended for treating severe or refractory cases of canine leproid granuloma syndrome. Treatment should be continued (typically for 4 to 8 weeks) until lesions are substantially reduced in size and ideally until lesions have resolved completely. A topical formulation, containing clofazimine in petroleum jelly may be used as an adjunct to systemic drug therapy. Further work is required to determine the most cost effective treatment regimen for this condition.

On a time-domain representation of the Kramers-Kronig dispersion relations

The development of Kramers-Kronig dispersion relations is typically carried out in the frequency domain. An alternative approach known as the time-causal theory develops dispersion relations for media with attenuation obeying a frequency power law through analysis in the time domain [T. L. Szabo, J. Acoust. Soc. Am. 96, 491-500 (1994)]. Although both approaches predict identical dispersion relations, it is perceived that these two approaches are distinct from each other. It is shown, however, that the time-causal theory is in essence a time-domain formulation of the Kramers-Kronig dispersion relations for the special case of media with attenuation obeying a frequency power law. Additionally, it is shown that time-domain representations of the Kramers-Kronig dispersion relations are available for a broader class of media than simply those with power law attenuation. The time-causal theory and the Kramers-Kronig dispersion relations can be viewed as two complementary, yet equivalent, approaches to the study of dispersion.

Kramers-Kronig relations applied to finite bandwidth data from suspensions of encapsulated microbubbles

In this work, the Kramers-Kronig (K-K) relations are applied to experimental data of resonant nature by limiting the interval of integration to the measurement spectrum. The data are from suspensions of encapsulated microbubbles (Albunex) and have the characteristics of an ultrasonic notch filter. The goal is to test the consistency of this dispersion and attenuation data with the Kramers-Kronig relations in a strict manner, without any parameters from outside the experimental bandwidth entering in to the calculations. In the course of reaching the goal, the artifacts associated with the truncation of the integrals are identified and it is shown how their impacts on the results can be minimized. The problem is first approached analytically by performing the Kramers-Kronig calculations over a restricted spectral band on a specific Hilbert transform pair (Lorentzian curves). The resulting closed-form solutions illustrate the type of artifacts that can occur due to truncation and also show that accurate results can be achieved. Next, both twice-subtracted and lower-order Kramers-Kronig relations are applied directly to the attenuation and dispersion data from the encapsulated microbubbles. Only parameters from within the experimental attenuation coefficient and phase velocity data sets are used. The twice-subtracted K-K relations produced accurate estimates for both the attenuation coefficient and dispersion across all 12 data sets. Lower-order Kramers-Kronig relations also produced good results over the finite spectrum for most of the data. In 2 of the 12 cases, the twice-subtracted relations tracked the data markedly better than the lower-order predictions. These calculations demonstrate that truncation artifacts do not overwhelm the causal link between the phase velocity and the attenuation coefficient for finite bandwidth calculations. This work provides experimental evidence supporting the validity of the subtracted forms of the acoustic K-K relations between the phase velocity and attenuation coefficient.

Mycobacterium genavense infection in two aged ferrets with conjunctival lesions

Mycobacterium genavense infection was diagnosed in two adult ferrets. Disseminated mycobacteriosis was diagnosed in a castrated 5-year-old sable ferret with generalised peripheral lymph node enlargement and a proliferative lesion of the conjunctiva of the nictitating membrane. The diagnosis was based on characteristic cytology and sequence analysis of the 16S rRNA gene amplified using the polymerase chain reaction from fresh biopsy material. Therapy with rifampicin, clofazimine and clarithromycin probably cured the infection. An entire 4-year-old female ferret with conjunctival swelling, serous ocular discharge and swelling of the subcutaneous tissues of the nasal bridge was diagnosed as having M genavense infection on the basis of typical cytology, histopathology and sequence analysis of 16S rRNA amplicons from formalin-fixed paraffin-embedded tissue. This patient was treated successfully using rifampicin. Both ferrets subsequently died as a result of other disease conditions, 10 and 4 months following initiation of therapy, respectively. This is the first report documenting M genavense as a cause of disseminated mycobacterial disease in ferrets. Conjunctival involvement may be a feature of disseminated mycobacteriosis in the ferret. The possibility that these infections were the consequence of a ferret retrovirus infection should be considered further.

Broadband time-domain reflectometry measurement of attenuation and phase velocity in highly attenuating suspensions with application to the ultrasound contrast medium Albunex

We describe a technique for broadband measurements of the attenuation coefficient and phase velocity of highly attenuating liquid suspensions. To validate the technique we apply it to the ultrasound contrast agent Albunex at concentrations ranging from 0.69 x 10(6) particles/mL to 364 x 10(6) particles/mL. These longitudinal wave measurements were performed on Albunex suspensions maintained at 37 degrees C in a special time-domain reflectometer designed and constructed in our laboratory. The frequency-dependent attenuation coefficients and phase velocities obtained in the reflectometer are compared to broadband through-transmission measurements of these same quantities, which were also performed in our laboratory. Although comparison data between the two techniques are only available at lower concentrations, the agreement is quite good and serves to validate the methods described in this paper.

On the applicability of Kramers-Kronig relations for ultrasonic attenuation obeying a frequency power law

In the recent literature concern has been raised regarding the validity of Kramers-Kronig relations for media with ultrasonic attenuation obeying a frequency power law. It is demonstrated, however, that the Kramers-Kronig dispersion relations for application to these types of media are available. The developed dispersion relations are compared with measurements on several liquids, and agreement is found to better than 1 m/s over the experimentally available bandwidth. A discussion regarding the validity of these dispersion relations, in particular how the dispersion relations relate to the so-called Paley-Wiener conditions, forms the conclusion.

Simultaneous detection and strain differentiation of Mycobacterium bovis directly from bovine tissue specimens by spoligotyping

Culture of Mycobacterium bovis is used routinely to support field diagnosis of bovine tuberculosis; however, this method is slow. Rapid detection and strain-typing of M. bovis directly from 37 lesioned bovine lymph node specimens was performed by the polymerase chain reaction (PCR) based method, spoligotyping. Mycobacterial DNA was extracted from the specimens using a nucleic acid sequence capture technique. Two sets of specimens were tested, the first set comprising 16 decontaminated tissue homogenates from lesioned lymph node specimens which had been processed for BACTEC culture and a second set of 21 non-decontaminated lesioned lymph node specimens. Both sets of specimens had been frozen before analysis. Sequence capture PCR enabled detection and strain-typing of M. bovis directly from 15 of the 16 decontaminated homogenates and all 21 of the non-decontaminated tissues. Four spoligotype (ST) patterns were obtained from each set; ST1, ST2, ST3 and ST16 were detected in the decontaminated specimens and ST1, ST2, ST11 and ST14 in the non-decontaminated specimens. For both sets of specimens, ST1 was the predominant strain type detected. ST patterns obtained from the BACTEC cultures of the decontaminated specimens were in agreement with those obtained directly from the tissue. The sensitivity of detection by sequence capture-PCR compared very favourably with that of BACTEC culture. ST patterns were obtained directly from tissues of 34 of the 35 culture positive specimens and the two culture negative specimens. DNA extraction from the 21 non-decontaminated specimens involved an initial stomaching treatment. An assessment of sequence capture on both liquid alone and liquid and tissue homogenate combined, following stomaching, indicated that PCR was less successful on the liquid component alone.

Identification by 16S rRNA gene analyses of a potential novel mycobacterial species as an etiological agent of canine leproid granuloma syndrome

PCR amplifications of the 16S rRNA gene were performed on 46 specimens obtained from 43 dogs with canine leproid granuloma syndrome to help determine its etiology. Sequence capture PCR was applied to 37 paraffin-embedded specimens from 37 dogs, and nested PCR was attempted on DNA from 9 fresh tissue specimens derived from 3 of the 37 aforementioned dogs and from an additional 6 dogs. Molecular analyses of the paraffin-embedded tissues and fresh tissue specimen analyses were performed at separate institutions. PCR products with identical sequences over a 350-bp region encompassing variable regions 2 and 3 of the 16S rRNA gene were obtained from 4 of 37 paraffin-embedded specimens and from all 9 specimens of fresh tissue originating from 12 of the 43 dogs. Identical sequences were determined from amplicons obtained from paraffin-embedded and fresh specimens from one dog. The consensus DNA sequence, amplified from paraffin-embedded tissue and represented by GenBank accession no. AF144747, shared highest nucleotide identity (99.4% over 519 bp) with mycobacterial strain IWGMT 90413 but did not correspond exactly to any EMBL or GenBank database sequence. With a probe derived from the V2 region of the novel canine sequence, reverse cross blot hybridization identified an additional four paraffin-embedded specimens containing the same novel sequence. In total, molecular methodologies identified the proposed novel mycobacterial sequence in 16 of 43 dogs with canine leproid granuloma syndrome, indicating that the species represented by this sequence may be the principal etiological agent of canine leproid granuloma syndrome.

Effects of transducer frequency and output power on the ultrasonographic contrast produced by Optison using fundamental and harmonic imaging techniques

This in vivo study demonstrated the effects of transducer frequency and output power on the sonographic contrast produced by Optison during continuous ultrasonographic imaging in both fundamental and harmonic modes. During fundamental imaging, Optison produced greater contrast intensity while imaging at higher transducer frequencies. However, in the harmonic mode, lower imaging frequencies caused Optison to produce more intense myocardial enhancement. Regardless of imaging mode, increases in transducer output power caused decreases in both contrast intensity and contrast duration produced by Optison. Proper selection of transducer frequency and output power will help optimize the quality and duration of contrast produced by Optison during continuous ultrasonographic imaging.

Broadband measurement of the scattering-to-attenuation ratio for Albunex at 37 degrees C

The attenuation coefficient and backscatter coefficient of Albunex were measured over a wide range of concentrations and frequencies (at a temperature of 37 degrees C), and were used to calculate the scattering-to-attenuation ratio (STAR) value. Each of these quantities exhibited concentration dependence in agreement with predictions from simple scattering theory: the backscatter coefficient grew linearly with concentration, the power of the transmitted signal decreased exponentially with concentration due to attenuation, and the STAR was independent of concentration scaling. Because of the markedly differing concentration dependence, it is necessary to consider all of these quantities (not just the STAR value alone) when evaluating and comparing the potential efficacy of ultrasonic contrast agents.

Targeting and ultrasound imaging of microbubble-based contrast agents

Preparation and characterization of targeted microbubbles (ultrasound contrast agents) is described. Specific ligands were attached to the microbubble shell, and ligand-coated microbubbles were selectively attached to various targets, using either an avidin biotin model system or an antigen-antibody system for targeting to live activated endothelial cells. Firm attachment of microbubbles to the target was achieved. Forces necessary to detach microbubbles from the target were estimated to exceed dozens of pN. Microbubbles were bound to the target even in the rapidly moving stream of the aqueous medium. Down to 20 ng of the ultrasound contrast material on the target surface could be detected by the ultrasound imaging with a commercial medical imaging system. At high bubble density on the target surface, strong ultrasound image attenuation was observed.

Disseminated Mycobacterium genavense infection in a FIV-positive cat

An 8-year-old FIV-positive Australian cat was presented with coughing, periocular alopecia, pyrexia and inappetence. Skin scrapings demonstrated Demodex cati mites. Antibiotics were administered and it was treated successfully for periocular demodectic mange, but the cat continued to exhibit respiratory signs and lose weight. Further investigation revealed an ascarid infection and active chronic inflammation of undetected cause affecting the lower airways. Repetitive treatment with pyrantel failed to eradicate the ascarid infection. The cat became cachectic and developed moist ulcerative dermatitis of the neck, severe non-regenerative anaemia, leucopenia and thrombocytopenia. Necropsy and histopathology revealed mycobacteriosis affecting skin, lungs, spleen, lymph nodes, liver and kidney. Attempted culture of frozen tissues at a mycobacteria reference laboratory was unsuccessful. Paraffin-embedded, formalin-fixed tissue was retrieved and examined using PCR to amplify part of the 16S rRNA gene. A diagnosis of disseminated Mycobacterium genavense infection was made based on the presence of acid fast bacteria in many tissues and partial sequence of the 16S rRNA gene. Although M genavense has been identified previously as a cause of disseminated disease in AIDS patients, this is the first report of infection in a cat. It was suspected that the demodecosis, recurrent ascarid infections and disseminated M genavense infection resulted from an immune deficiency syndrome consequent to longstanding FIV infection.

Direct video-microscopic observation of the dynamic effects of medical ultrasound on ultrasound contrast microspheres

RATIONALE AND OBJECTIVES

Ultrasound can cause destruction of microbubble contrast agents used to enhance medical ultrasound imaging. This study sought to characterize the dynamics of this interaction by direct visual observation of microbubbles during insonification in vitro by a medical ultrasound imaging system.

METHODS

Video microscopy was used to observe air-filled sonicated albumin microspheres adsorbed to a solid support during insonation.

RESULTS

Deflation was not observed at lowest transmit power settings. At higher intensities, gas left the microparticle gradually, apparently dissolving into the surrounding medium. Deflation was slower for higher microsphere surface densities. Intermittent ultrasound imaging (0.5 Hz refresh rate) caused slower deflation than continuous imaging (33 Hz).

CONCLUSIONS

Higher concentrations of microbubbles, lower ultrasound transmit power settings, and intermittent imaging each can reduce the rate of destruction of microspheres resulting from medical ultrasound insonation.

Broadband measurements of phase velocity in Albunex suspensions

The phase velocities in suspensions of Albunex, an ultrasound contrast agent, are determined using the technique of broadband phase spectroscopy. In these suspensions, phase velocities were measured as a function of Albunex concentration in Isoton II (buffered saline). The dispersion over the measurement bandwidth (1-15 MHz) grew with increasing Albunex concentration, exhibiting a 221-m/s change (17% increase) in phase velocity between 1.0 and 3.8 MHz at the highest concentration reported (32 microL Albunex/8 mL Isoton). The dispersion behavior of the Albunex suspensions is described using a model of encapsulated gas bubbles. The influence of the dispersion in Albunex on broadband pulses is discussed, as well as the potential impact this dispersion may have on the formation of ultrasonic images of the heart.

Rapid diagnosis and strain differentiation of Mycobacterium bovis in radiometric culture by spoligotyping

An assessment of spoligotyping for rapid detection and strain typing of Mycobacterium bovis isolates in radiometric culture was made. Spoligotyping was applied to BACTEC 12B broth cultures of 54 lesioned bovine lymph node specimens from 44 herds in Northern Ireland. A nucleic acid sequence capture technique was performed on BACTEC cultures at growth index points of approximately (approximately) 60, approximately 200, and 999. Definitive spoligotype patterns were obtained for 90.4% and 94.2% of all 52 BACTEC culture-positives at growth indexes approximately 60 and approximately 200, respectively. Within 10 days, definitive spoligotype patterns were obtained for 84.6% of the culture-positives. This technique, therefore, allowed earlier and more accurate diagnosis of M. bovis than traditional methodologies, as well as simultaneous strain differentiation. Application of this molecular tool to BACTEC cultures would be a significant advance in bovine tuberculosis eradication programmes. Seven distinct spoligotype patterns were identified in this study, 2 of which (ST21 and ST25), had not been identified previously in cattle from Northern Ireland. Two spoligotype patterns (ST1 and ST2) accounted for 80.7% of the culture-positives. These were found to have widespread geographic distribution, whereas 1 spoligotype pattern (ST14) had limited geographical distribution.

Spacer oligotyping of Mycobacterium bovis isolates compared to typing by restriction fragment length polymorphism using PGRS, DR and IS6110 probes

Ninety-two Mycobacterium bovis isolates from cattle, deer and badgers in Northern Ireland and the Republic of Ireland were genotyped by spacer-oligotyping (spoligotyping) and 67 of these were analysed by restriction fragment length polymorphism (RFLP). RFLP analysis was performed using three DNA probes, PGRS, DR and IS6110. Forty-seven of the M. bovis isolates were from 45 different sources; these were typed using both RFLP and spoligotyping. These 47 isolates could be differentiated into 24 different RFLP types and 15 distinct spoligotypes. Although RFLP was found to be more discriminatory compared to the present spoligotyping technique, spoligotyping was able to differentiate 21 RFLP type 'ACA' isolates into three different patterns. The remaining 45 M. bovis isolates were from a small case study, involving infected cattle, deer and badgers from the same geographic region. All these isolates were analysed by spoligotyping and a selection of 20 isolates were RFLP typed. All the isolates in the case study had the same spoligotype pattern with the exception of one cervine isolate. Similarly all the isolates typed by RFLP had the same pattern. Consequently, the predominant strain in the case study was not host restricted. The consistency between the results obtained using the two techniques indicates the potential value of both techniques for epidemiological studies. Spoligotyping was found to be a much more rapid technique and easier to perform, requiring less sophisticated computer software for strain typing. Spoligotyping results were more readily documented and analysed and the technique was also more suitable than RFLP analysis for large-scale screening studies.

Development of mycobacterial species-specific DNA probes by subtraction hybridization

Subtraction hybridization was used to identify sequences of Mycobacterium bovis DNA which might be of diagnostic value. Genomic DNA from Mycobacterium avium, isolated commonly from cattle and whose tuberculin is used in the comparative intradermal tuberculin test, was subtracted from M. bovis genomic DNA. A novel sequence, of 131 bp, which appears to be Mycobacterium tuberculosis complex-specific was identified. The specificity of this sequence was stringently tested by a probe and polymerase chain reaction (PCR) assay. Nucleotide identity determination and sequence comparisons revealed that the 131-bp sequence is located directly upstream of a potential isocitrate dehydrogenase (IDH) coding gene and may be of diagnostic value, enabling differentiation of M. tuberculosis complex mycobacteria from other mycobacterial species.

Determination of the etiology of presumptive feline leprosy by 16S rRNA gene analysis

PCR-amplified 16S rRNA gene sequences were obtained directly from tissue specimens from eight cats with presumptive feline leprosy. Acid-fast bacilli were observed in sections from all eight specimens, but culture for mycobacteria was successful for one specimen only. Analysis of the V2 variable region of each 16S rRNA PCR product identified a sequence with 100% nucleotide identity to the sequences of Mycobacterium lepraemurium, Mycobacterium avium, and Mycobacterium paratuberculosis in four of the specimens from cats with feline leprosy. Separate M. paratuberculosis- and M. avium-specific PCR amplifications of the four specimens were negative, thus substantiating the identification of M. lepraemurium in these specimens from cats with feline leprosy. Further sequence analysis of the V3 variable region of one of the four specimens provided conclusive evidence of the presence of M. lepraemurium. This is the first report of the definitive identification of M. lepraemurium in cats with feline leprosy by molecular biology-based analyses. M. avium, which is rarely reported in cats, and Mycobacterium chitae, a reported nonpathogenic, rapidly growing mycobacterial species found in the environment, were identified in the specimen from which acid-fast bacilli were cultured. Two of the specimens from cats were infected with a potentially novel species of mycobacteria which had a 16S rRNA gene sequence sharing the closest nucleotide sequence identity with that of Mycobacterium malmoense. Molecular biology-based analyses provided for the accurate and rapid diagnosis of mycobacterial infections in cats and circumvented the problems of culture and misdiagnosis of feline leprosy associated with traditional methods.

Targeting of ultrasound contrast material. An in vitro feasibility study

PURPOSE

It would be beneficial to design a targetable microbubble ultrasound contrast agent that would selectively bind to the areas of interest in the body and enhance the target organ in the ultrasound examination.

MATERIAL AND METHODS

We have studied the feasibility of targeting in a model system. We used avidin and biotin as a model ligand-receptor pair. Avidin was adsorbed on the surface of polystyrene, and biotin derivative was attached to microbubble shells. After removal of unincorporated biotin from the microbubbles, they were allowed to come in contact with avidin-coated or albumin-coated plastic. Unbound bubbles were washed by a stream of water.

RESULTS

Binding of microbubbles to the surface occurred selectively in the areas where avidin layer was deposited. Binding of microbubbles to avidin layer was dependent on the amount of biotin incorporated in the microbubble shell. Presence of free biotin blocked targeting completely. Acoustic studies were performed using a custom-built ultrasound measurement apparatus and an ultrasound medical imaging system. Microbubble-coated areas of the plastic dish were clearly visualized with ultrasound imaging. A strong backscattered signal was obtained for microbubble surface densities as low as 3%.

CONCLUSION

Microbubbles have been selectively targeted via a ligand-receptor system in vitro. Firm binding of microbubbles to avidin-coated surface has been achieved. Microbubbles deposited on the target were visualized with ultrasound imaging systems.

Differentiation of Mycobacterium bovis isolates from animals by DNA typing

The insertion sequence IS6110 and the direct repeat (DR) specific to tuberculosis complex mycobacteria and the highly repeated DNA sequence, the polymorphic GC-rich repeat sequence (PGRS), were systematically used to identify restriction fragment length polymorphisms (RFLPs) within 210 isolates of Mycobacterium bovis. The isolates were primarily of bovine origin, but isolates from badgers, feral deer, sheep, humans, and a pig were included. The RFLP probes IS6110, DR, and PGRS individually identified 17, 18, and 18 different RFLP types, respectively, but in combination these probes identified a total of 39 different M. bovis RFLP types. The recommendations (J. D. A. van Embden, M. D. Cave, J. T. Crawford, J. W. Dale, K. D. Eisenach, B. Gicquel, P. W. M. Hermans, C. Martin, R. McAdam, T. M. Shinnick, and P. M. Small, J. Clin. Microbiol. 31:406-409, 1993) for a standardized RFLP analysis for M. tuberculosis were adapted to facilitate gel documentation, image analysis, and construction of a database of RFLP types. In the present study the same M. bovis RFLP types were evident in the various animal species included, indicating that the strains were not host restricted. Application of these techniques to defined field studies should help elucidate more accurately aspects of the epidemiology of bovine tuberculosis in different countries.

Vaccination of the badger (Meles meles) against Mycobacterium bovis

This review summarizes current knowledge relating to the potential development of a vaccine against Mycobacterium bovis (M. bovis) for use in badgers. The serious economic loss incurred from bovine tuberculosis in Ireland is highlighted. The problems presented to national bovine tuberculosis eradication programmes by wildlife reservoirs of M bovis, in particular the badger and the brushtail possum, are outlined. Badger and possum ecology and the epidemiology of M. bovis infection in these species are compared in relation to control strategies. Current information regarding the immune responses of badgers and possums to M. bovis infection is presented. Vaccine types, carrier and adjuvant systems, available vaccines for human and animal tuberculosis and delivery to wildlife species are described. The feasibility of vaccinating badgers against M. bovis infection and the possible options for a vaccination strategy are discussed.