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Biomedical subjects

I B Marsh

Publications and source records attributed to I B Marsh.

17 recordsLinked to original sources
PubMed2006

Genomic diversity in Mycobacterium avium: single nucleotide polymorphisms between the S and C strains of M. avium subsp. paratuberculosis and with M. a. avium.

Following identification of large genomic polymorphisms in a previous study, a polymerase chain reaction and sequencing strategy was used to identify single nucleotide polymorphisms (SNPs) in 25 genes in the sheep (S) and cattle (C) strains of Mycobacterium avium subsp. paratuberculosis (M. a. paratuberculosis) and between M. a. paratuberculosis and M. a. avium. From 12,117 bp of sequence representing 26 loci across 25 genes, 11 SNPs were identified between the S and C strains in eight genes: hsp65, sodA, dnaA, dnaN, recF, gyrB, inhA, and pks8. An in silico comparison of these M. a. paratuberculosis sequences and the M. a. avium 104 genome revealed 86 SNPs, which corresponded well with similar studies of SNPs in the M. avium complex.

Animals↗
PubMed2005

Deletion of an mmpL gene and multiple associated genes from the genome of the S strain of Mycobacterium avium subsp. paratuberculosis identified by representational difference analysis and in silico analysis.

Mycobacterium avium subsp. paratuberculosis (M. a. paratuberculosis) can be divided into two major strains, sheep (S) and cattle (C), based on cultural requirements, host specificity, degree of clumping of cells in suspension and minor genomic differences including copy number of insertion elements and point mutations. Representational difference analysis (RDA) with S strain as driver and C strain as tester was used to identify unique genomic regions. Three sequences (RDA1, RDA3 and RDA4) were identified. RDA1 (229bp) contained a single base difference between S and C strains. RDA4 (163bp) was an artefact. RDA3 (206bp) was similar to several sequences in the incomplete genome sequences of M. avium subsp. paratuberculosis K10 and M. avium subsp. avium 104. In silico analysis led to the identification of a deletion that may be as large as 17kb in the sheep strain of M. a. paratuberculosis. PCR analysis of this region confirmed the deletion of 11,584bp that included 10 genes (MAP1734 to MAP1743c) of the M. a. paratuberculosis K10 genome. This included the loss of mmpL5 and mmpS5 genes and homologues of the M. tuberculosis genes: Rv2002 (fabG3), Rv2017c (lipW), Rv3132c (devS), Rv2032 (acg) and the conserved hypothetical genes Rv2005c and Rv2026c. PCR reactions designed to detect the single nucleotide polymorphism in RDA1 and the deletion in the mmpL region can be used to distinguish these strains. MmpL genes, found in M. tuberculosis and other mycobacteria are part of the resistance-nodulation-division (RND) family but contain domains unique to mycobacteria thought to play a role in cell wall biogenesis, virulence and other phenotypic characteristics. Absence of mmpL5 in the S strain of M. a. paratuberculosis is unlikely to account for the difference in clumping in suspension but may explain the difference in cultural requirements and host specificity compared to the C strain but the impact of the remainder of the deletion is yet to be ascertained.

Base Sequence↗
PubMed2003

Strabismus surgery: adjustable sutures-good for all?

AIMS: The role of adjustable sutures in strabismus surgery has mainly been limited to conditions like dysthyroid restrictive myopathy, blow-out fractures of orbit, aberrant regeneration of nerves, and certain other long-standing and complicated squints. In this clinical study, an attempt has been made to analyse the efficacy of adjustable sutures in squint surgery as a routine procedure. We also studied patients' acceptability and satisfaction following this procedure and analysed various factors that may influence the surgical outcome (age, sex, previous surgeries, injections of botulinum toxin, etc). METHODS: A total number of 443 patients, aged between 13 and 78 years, who underwent strabismus surgery in our department, from January 1996 to January 2000, were included in this study. Of these patients, 141 had surgery with adjustable sutures and 302 patients without adjustable sutures. Surgical results were followed up for a period ranging from 12 to 50 months. The main outcome measure was a need for a reoperation in the two groups. In addition, we also studied patients' satisfaction with regard to final cosmetic appearance or relief of diplopia; percentage change in angle of deviation in two groups, and influence of various factors such as age, sex, previous surgeries, and injection of botulinum toxin on the final surgical outcome. The results were statistically analysed using Levene's test for equality of variances, t-test for equality of means, and statistical significance of the results was analysed by calculating P-values. RESULTS: In total, 8.51% of the patients in the adjustable group and 27.15% in the nonadjustable group needed a reoperation. Surgical results were found to be significantly better in patients who had adjustable sutures in comparison to those who did not have adjustable sutures (P<0.005). Patients' satisfaction and percentage change in angle of deviation was also much higher in adjustable sutures group. Age, sex, number of previous surgeries, previous injections of botulinum toxin, and type and amount of deviation had no statistically significant influence on the surgical outcome. CONCLUSIONS: Strabismus surgery with adjustable sutures has a statistically significant better, final result than surgery without adjustable sutures. Patients' satisfaction and percentage change in angle of deviation is also much higher in the adjustable sutures group. As age, sex, number of previous surgeries, previous injections of botulinum toxin, and type and amount of deviation do not influence the final outcome, this type of surgery can be performed in virtually all types of patients.

Adolescent↗
PubMed2003

Isolation of Mycobacterium avium subsp paratuberculosis from environmental samples collected from farms before and after destocking sheep with paratuberculosis.

OBJECTIVE: To determine whether Mycobacterium avium subsp paratuberculosis could be isolated from soil-pasture, faecal, water and sediment samples on farms before and after removal of sheep with paratuberculosis. A feasibility study and subsequent field survey. PROCEDURE: First the analytical sensitivity of radiometric culture of the organism from two types of soil was determined relative to faeces. Then soil-pasture, faecal, water and sediment samples were collected for culture from a range of sites from 6 farms with paratuberculosis affected sheep and goats. Similar samples were collected from 20 farms at least 9 months after removal of infected stock. RESULTS: The analytical sensitivity of culture of M a paratuberculosis from soil samples was 2 orders of magnitude less than that from faeces, and environmental samples required longer incubation periods to yield significant growth in radiometric culture (BACTEC) medium. However, the organism was recovered from approximately 20% of 163 soil-pasture, water and sediment samples from 6 properties with clinically-affected animals with paratuberculosis. The positive samples were from a range of topographic sites, including open exposed and dry areas, however, low lying areas tended to have larger numbers of organisms. When the same sites were sampled again about 5 months later, only 1 was culture positive, and none were culture positive > 12 months later. Of 17 water and dam sediment samples collected from farm 6, which had long-standing high prevalence OJD infection, only one water sample and one sediment from the same dam were culture positive. None of the 5 water samples from the other farms were culture positive. Of 96 water samples, 90 sediment samples and 93 soil samples from farms that had been destocked of infected sheep/goats for 9 to 24 months, one sediment sample from a farm in Victoria (destocked for 12 months) and two sediment samples from a farm in New South Wales (10, 19 months) were culture positive. Recontamination from cattle or water could not be excluded as a cause of the positive cultures from the second farm. CONCLUSION: M a paratuberculosis can be detected by radiometric culture in environmental samples from farms grazed by sheep or goats with paratuberculosis. There is a relatively low likelihood of recovery of the organism from water samples from such farms, and at 5 or more months after removing stock with paratuberculosis the likelihood of positive cultures from environmental samples is very low. Although the analytical sensitivity of culture from environmental samples is less than that from faeces, surveys of environmental sites are nevertheless feasible. However, improved culture methods are needed for critical surveys and to study the movement and fate of the organism in the environment.

Animals↗
PubMed2002

Rapid differentiation of Australian, European and American ranaviruses based on variation in major capsid protein gene sequence.

Epizootic haematopoietic necrosis virus (EHNV), Bohle iridovirus (BIV) and Wamena virus (WV) cause serious diseases in fish, amphibians and snakes, respectively but are restricted to Australasia. European catfish virus (ECV) and sheatfish virus (ESV) have caused epizootics in fish on farms in continental Europe. Currently there are no simple or readily available methods to distinguish these viruses, which are in the Iridoviridae. They are culturally, morphologically and antigenically very similar to Frog Virus 3 (FV3), the type species in Ranavirus in this family and Gutapo virus (GV), another amphibian ranavirus from America. The diseases caused by EHNV, ESV and ECV are so serious that they are internationally notifiable. Tests to distinguish these viruses are desirable to ensure that disease occurrences do not unnecessarily restrict trade in aquaculture products. The gene encoding the major capsid protein from two EHNV isolates from different fish species (Perca fluviatilis and Oncorhynchus mykiss) and one BIV isolate were sequenced and the data and deduced amino acid sequences were compared with those from FV3 and other iridoviruses. The sequences for the two EHNV isolates were identical, confirming suggestions from existing partial MCP sequence that the same type of EHNV infects wild redfin perch and farmed rainbow trout. Differences in restriction endonuclease patterns of specific PCR products were predicted and confirmed between EHNV, BIV, and WV and provided a basis for rapid differentiation of these viruses from each other and from ESV/ECV and FV3/GV. These simple and rapid tests to distinguish important ranaviruses from the regions of Europe, Australia and America will help regulatory authorities assess the need for disease control responses in the event of occurrence of ranavirus infection in aquaculture species.

Americas↗
PubMed2001

Progress towards a rapid polymerase chain reaction diagnostic test for the identification of Mycobacterium avium subsp. paratuberculosis in faeces.

Hybridization-capture polymerase chain reaction (HC-PCR), a nucleic acid sequence capture technique, was evaluated on faecal samples pooled from 50 sheep and individual faecal samples as a rapid diagnostic test for Mycobacterium avium subsp. paratuberculosis, the causative agent of Johne's disease. The status of each of the faecal samples was determined by radiometric culture. A simpler direct-PCR technique was evaluated on the same samples and was found to be more sensitive than HC-PCR. The lack of sensitivity of HC-PCR was neither due to location nor length of capture probe on IS 900 nor deterioration of the probe but was associated with inefficiencies in liquid phase hybridization and solid phase magnetic bead capture. Direct-PCR using primers from the 5' region of IS 900 was evaluated in a blind trial on 502 pooled faecal samples which were concurrently examined by culture. Twenty-one (64%) of the 33 culture positive pools were detected by direct PCR, representing 11 (79%) of the 14 farms with infected sheep. Direct-PCR was also more sensitive than immunomagnetic bead capture-PCR. Using individual faecal samples, 74% of culture positive samples were detected with direct-PCR compared to 44% with immunomagnetic bead capture-PCR. Direct-PCR from faeces can be used as a rapid means of screening pooled faecal samples for flock diagnosis of Johne's disease in sheep.

Animals↗
PubMed2001

Typing of IS 1311 polymorphisms confirms that bison (Bison bison) with paratuberculosis in Montana are infected with a strain of Mycobacterium avium subsp. paratuberculosis distinct from that occurring in cattle and other domesticated livestock.

Isolates of Mycobacterium avium subsp. paratuberculosis from nine bison (Bison bison) from Montana, United States of America, were compared with those from other species from the United States of America. All 16 isolates had a novel IS 1311 genotype in which all copies of the element possessed a thymidine-cytosine nucleotide variation at base position 223. Isolates from bison were termed B strain. Thirteen isolates from cattle and goats were polymorphic at this locus, a status previously recognised in isolates from cattle which are termed C strains. Differences in cultural phenotype between B and C strains which were noted upon primary isolation did not manifest upon subculture to Herrold's egg yolk medium or modified Middlebrook 7H10 agar. Rapid differentiation of these strains from each other and from S strains from sheep is possible using polymerase chain reaction and restriction endonuclease analysis. The epidemiology of paratuberculosis in bison in Montana appears to be distinct from that in cattle and other farmed livestock investigated thus far.

Animals↗
PubMed2000

Comparative sensitivity of various faecal culture methods and ELISA in dairy cattle herds with endemic Johne's disease.

In three New South Wales dairy cattle herds with endemic Johne's disease, prevalence rates by faecal culture were determined to be 12, 18 and 22%, respectively. Whole herd faecal culture was shown to detect markedly more infected cattle than whole herd testing by the EMAI absorbed ELISA, particularly in the two herds with greatest prevalence. In the three study herds, five methods for whole herd faecal culture were compared in each. These included two methods based on primary culture on Herrold's egg yolk medium with mycobactin J (HEYM): (1) conventional decontamination with sedimentation and primary culture on HEYM; (2) Whitlock decontamination and culture on HEYM. The remaining three methods were based on radiometric (BACTEC) culture: (3) decontamination and filtration to BACTEC medium; (4) modified Whitlock decontamination to BACTEC medium and (5) Whitlock decontamination to BACTEC medium. For BACTEC cultures, two methods were compared as confirmatory tests for Mycobacterium paratuberculosis: mycobactin dependence on conventional subculture to HEYM and IS900 PCR analysis of radiometric media. Among 179 cattle tested simultaneously by all five culture methods, 38 cattle were confirmed to be shedding M. paratuberculosis. In identifying shedder cattle, method 5 was the most sensitive, followed by methods 2, 4, 1, and 3 was the least sensitive. The number of BACTEC cultures confirmed by mycobactin dependence or PCR was similar.

Animals↗
PubMed1998

Inferior oblique syndrome: an under-recognised complication of strabismus surgery.

PURPOSE: To show the predictive factors that would indicate the possibility of inferior oblique inclusion when considering surgery on a previously operated lateral rectus muscle. We also aim to highlight the importance of freeing any inferior oblique attachment to the lateral rectus muscle during either a resection or a recession procedure. METHODS: A retrospective review was undertaken of 39 patients who had previously had horizontal muscle surgery. Pre- and postoperative ocular position and rotations were compared. Using the hypothesis that a vertical element to the strabismus or a deficiency of vertical ocular rotation may result from inclusion of inferior oblique fibres during lateral rectus surgery, we compared the groups using the Fisher Exact two-tailed test. RESULTS: Eight of the 39 patients were identified as having inferior oblique inclusion. Six were found to have a vertical deviation in the primary position and 6 a deficiency of vertical rotation. CONCLUSION: A vertical deviation or a deficiency of vertical rotation are significant predictors of inferior oblique inclusion into the lateral rectus insertion. Re-operation to free the inferior oblique fibres often fails to reduce the vertical deviation, and hence there is a need for careful dissection of the inferior oblique during the primary surgery.

Humans↗
PubMed1993

Is post-cataract mydriasis necessary?

We report the results of a randomised prospective trial of post-operative cyclopentolate in patients who had uncomplicated endocapsular cataract extraction. We found no significant difference in visual acuity, intraocular lens centration or pupil area achieved after dilatation with tropicamide. There was a marked increase in the incidence of posterior synechiae in the group receiving cyclopentolate (33% vs. 13%).

Aged↗
PubMed1987

Traumatic myopia; an ultrasonographic and clinical study.

Three patients with transient myopia following blunt injury are described with the aid of serial ultrasonography. The cause of refractive change is an increase in the anteroposterior thickness of the crystalline lens, which probably results from oedema of the ciliary body.

Adolescent↗