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Biomedical subjects

J C Low

Publications and source records attributed to J C Low.

At least 19 recordsLinked to original sources
PubMed1999

Characterisation of Listeria ivanovii isolates from the UK using pulsed-field gel electrophoresis.

Forty-three Listeria ivanovii isolates were collected in the UK between 1991 and 1997 from: 35 animal infections; two human infections; five foods; and one environmental source. A further two type strains of L. ivanovii (subsp. ivanovii and subsp. londoniensis) were obtained from a culture collection. These bacteria were characterised by conventional phenotypic methods and by pulsed-field gel electrophoresis (PFGE) using ApaI and SmaI. Forty-two of the isolates from the UK were identified as L. ivanovii subsp. ivanovii and the remaining culture as L. ivanovii subsp. londoniensis. Six and four PFGE profiles were obtained using ApaI and SmaI digestion respectively; six composite profiles were obtained combining the results for both enzymes. The PFGE profile of the UK L. ivanovii subsp. londoniensis (isolated from processed shrimps) was similar to the type strain of this subspecies and differed from all of the L. ivanovii subsp. ivanovii tested. The majority of isolates (38 out of 45) belonged to one profile showing that the UK population of this bacterium is much less genetically diverse than similar studies have shown for Listeria monocytogenes.

Animals↗
PubMed1998

PCR methods and plasmid profile analysis for characterisation of Histophilus ovis strains.

The value of polymerase chain reaction (PCR)-based DNA fingerprinting and plasmid profile analysis for differentiation of Histophilus ovis isolates was assessed. Nineteen isolates of H. ovis were typed by PCR-ribotyping, repetitive extragenic palindromic element (REP)-PCR and enterobacterial repetitive intergenic consensus (ERIC)-PCR. These methods distinguished five types by PCR-ribotyping, 11 types by REP-PCR and seven types by ERIC-PCR. The ribotyping method produced a relatively simple pattern and a small number of distinct types and was useful for differentiation of H. ovis from the phenotypically similar organism, Haemophilus somnus. REP- and ERIC-PCR both produced complex banding patterns, but increased the discrimination between strains. Plasmids were found in 12 of the 19 isolates and there were four different plasmid profiles. A combination of the PCR methods and plasmid profile analysis provided a high resolution typing method for H. ovis.

Animals↗
PubMed1998

Specific PCR primers from the 16S-23S rRNA spacer region for the rapid detection and identification of Actinobacillus seminis.

Actinobacillus seminis is a common cause of ovine epididymitis and ram infertility. The ability to detect and identify this organism promptly is important commercially for the quality control of ram semen samples. Actinobacillus seminis is a fastidious and slow-growing bacterium and primary isolation and presumptive identification can be difficult and time-consuming. In this study, two ribosomal operons, termed rrnA and rrnB, have been characterized in the A. seminis genome, and these contain one and two tRNAs, respectively, in the spacer region between the 16S and 23S rRNA genes. Species-specific primers for A. seminis were developed from the sequence of the spacer region of rrnB for the identification and detection of A. seminis by PCR. The PCR assay was specific for A. seminis and gave no amplification products with phenotypically similar organisms such as Histophilus ovis. Storage solution used to preserve semen for long-term storage was found to inhibit the PCR. Therefore, for diagnostic purposes, the assay would best be performed after primary isolation or perhaps on fresh semen prior to storage if obvious contamination is indicated.

Actinobacillus↗
PubMed1998

PCR methods for rapid identification and characterization of Actinobacillus seminis strains.

Twenty-four isolates of Actinobacillus seminis were typed by PCR ribotyping, repetitive extragenic palindromic element (REP)-based PCR, and enterobacterial repetitive intergenic consensus (ERIC)-based PCR. Five types were distinguished by REP-PCR, and nine types were distinguished by ERIC-PCR. PCR ribotyping produced the simplest pattern and could be useful for identification of A. seminis and for its differentiation from related species. REP- and ERIC-PCR could be used for strain differentiation in epidemiological studies of A. seminis.

Actinobacillus↗
PubMed1997

Comparison of five tests for the detection of antibodies against chlamydial (enzootic) abortion of ewes.

Five tests for antibodies against chlamydial (enzootic) abortion of ewes were compared using 255 sera from experimentally (group 1) or naturally (group 2) infected animals, flocks free of the disease (group 3) and individual animals testing positively by the complement fixation test but from flocks with no evidence of chlamydial abortion (group 4). Sera from five specific pathogen-free lambs vaccinated with two different subtypes of Chlamydia pecorum were also included (group 5). All tests used some form of processed culture of C psitiaci as antigen. Specificities, established with group 3 and 4 sera, ranged between 96 per cent (ELISA using lipopolysaccharide antigen) and 59 per cent (Immunocomb). Reactions with group 5 sera suggested that the cause of false positive results in the field might be cross-reactive antibodies against the arthritogenic subtype of C pecorum. Sensitivities, established with groups 1 and 2 sera, ranged between 81 per cent (Immunocomb) and 51 per cent (ELISA using solubilised protein antigen). The minimum sample sizes required to be 95 per cent certain of detecting at least five seropositives in two infected flocks (combined data) were 15 to 48, dependent on the test applied. The Western blot test, applied to a proportion of samples, yielded no false positives with group 3 sera but 31.7 per cent with group 4 sera. Thus, none of the tests in this comparison emerged as sufficiently satisfactory in all respects, suggesting that further improvements in chlamydial serology must come through the use of non-native antigens or in the form of a competitive ELISA.

Abortion, Septic↗
PubMed1997

A review of Listeria monocytogenes and listeriosis.

Following the initial isolation and description in 1926 Listeria monocytogenes has been shown to be of world-wide prevalence and is associated with serious disease in a wide variety of animals, including man. Our knowledge of this bacterial pathogen and the various forms of listeriosis that it causes has until recently been extremely limited, but recent advances in taxonomy, isolation methods, bacterial typing, molecular biology and cell biology have extended our knowledge. It is an exquisitely adaptable environmental bacterium capable of existing both as an animal pathogen and plant saprophyte with a powerful array of regulated virulence factors. Most cases of listeriosis arise from the ingestion of contaminated food and in the UK the disease is particularly common in ruminants fed on silage. Although a number of forms of listeriosis are easily recognized, such as encephalitis, abortion and septicaemia, the epidemiological aspects and pathogenesis of infection in ruminants remain poorly understood. The invasion of peripheral nerve cells and rapid entry into the brain is postulated as a unique characteristic of its virulence, but relevant and practical disease models are still required to investigate this phenomenon. This review offers an up to date introduction to the organism with a description of virulence determinants, typing systems and a detailed account of listeriosis in animals. Experimental and field papers are reviewed and further sections deal with the diagnosis, treatment and control of listeriosis in animals. A final part gives an overview of listeriosis in man.

Animal Diseases↗
PubMed1997

Antimicrobial resistance of Salmonella enterica typhimurium DT104 isolates and investigation of strains with transferable apramycin resistance.

An examination of salmonella isolates collected by the Scottish Agricultural College Veterinary Services Division from April 1994 to May 1995 was conducted to determine the extent to which Salmonella enterica serotype Typhimurium phage type 104 (DT104) occurred and to investigate the antimicrobial resistance patterns of isolates. Typhimurium DT104 was the predominant salmonella and was isolated from nine species of animal. All isolates of this phage type possessed resistance to at least one antimicrobial and 98% of the isolates were resistant to multiple antimicrobials with R-type ACTSp the predominant resistance pattern. Various other resistance patterns were identified and transferable resistance to the veterinary aminoglycoside antimicrobial apramycin was demonstrated in three strains. A retrospective study for gentamicin resistance in isolates from the Scottish Salmonella Reference Laboratory collection revealed a human isolate of Typhimurium DT104 resistant to gentamicin but sensitive to apramycin and a bovine isolate with apramycin and gentamicin resistance.

Animals↗
PubMed1996

Voltage dependency of light-evoked on-off transient amacrine cell responses in carp retina.

The voltage dependency of the ON and the OFF components of transient amacrine cell responses was studied using two-electrode voltage-clamp and current-clamp techniques in the isolated retina of the carp. The two independent approaches gave similar data. When cells were voltage clamped near their resting potentials, both response components were associated with transient inward currents. Hyperpolarization increased response size (current or voltage) whilst depolarization decreased it. Response reversal, or a tendency for it, occurred at membrane potentials significantly more positive than the resting level with some quantitative variability. These data support the view that the ON-OFF depolarizations represent basically excitatory postsynaptic potentials and that the transience of the responses cannot mainly be due to any voltage-dependent conductance.

Animals↗
PubMed1996

Concurrent bovine viral diarrhoea virus and Salmonella typhimurium DT104 infection in a group of pregnant dairy heifers.

Two days after being imported into the United Kingdom one of a group of 30 pregnant dairy heifers showed clinical signs of bovine viral diarrhoea virus (BVDV) infection and subsequently died. Before it died the heifer was BVDV antigen-positive and antibody-negative. The gross post mortem findings were suggestive of mucosal disease but in addition to noncytopathic BVD virus, Salmonella typhimurium DT104 was cultured from tissues and gut contents. The other heifers were screened for S typhimurium by culturing faeces, and serology showed that 13 (45 per cent) of the group seroconverted to BVDV in the three weeks between samplings and the remainder were seropositive, indicating previous exposure. During this period four heifers showed clinical signs of acute BVDV infection but recovered uneventfully. Four animals (14 per cent) were positive for S typhimurium DT104 on faecal culture, and three of these excretors concurrently seroconverted to BVDV. Of the 29 heifers remaining in the group, one aborted in late gestation, 26 bore live calves and two delivered stillborn calves. Pre-colostral blood samples from the calves showed that their dams' pre-existing antibody titres correlated well with in utero fetal protection. In non-immune dams, exposure to BVDV between 69 and 120 days of gestation led to the birth of live persistently viraemic calves. Infection between 120 and 140 days of gestation led to the birth of live calves with evidence of congenital damage to the central nervous system, and infection later than 140 days of gestation led to the birth of live, normal calves with high pre-colostral antibody titres to BVDV. One calf which sucked colostrum was antibody and virus antigen-positive when sampled at 12 hours old but regular blood sampling failed to detect viraemia again until the calf was seven weeks old when it became persistently viraemic.

Animals↗
PubMed1996

Sulphur-induced polioencephalomalacia in lambs.

An outbreak of polioencephalomalacia affected 16 of 46 Swaledale lambs and five of 25 Scottish blackface lambs 15 to 32 days after they were introduced to an ad libitum concentrate ration containing 0.43 per cent sulphur. The clinical signs were acute and included depression central blindness and head-pressing, but no hyperaesthesia, nystagmus, dorsiflexion of the neck or opisthotonos were observed. Treatment of the affected lambs with vitamin B1, dexamethasone and antibiotics was associated with a prolonged recovery period, though no further cases were identified after vitamin B1 had been given parenterally to all the lambs at risk.

Animal Feed↗
PubMed1995

Prevalence of Actinobacillus seminis in the semen of rams in the United Kingdom.

A survey was conducted to establish the prevalence of Actinobacillus seminis in ovine semen and the possible importance of the organism as a cause of ram infertility. A seminis was isolated from three of 16 infertile rams and the infected animals had lesions of the genital tract and produced poor quality semen. A seminis was also isolated from two of 96 fertile rams used as donors of semen for artificial insemination programmes. The strains of A seminis could be identified on the basis of their API ZYM profiles. The results suggest that in the United Kingdom A seminis should be considered as a common cause of infertility in rams.

Actinobacillus↗
PubMed1995

Development and evaluation of an indirect ELISA to detect antibodies to abortion strains of Chlamydia psittaci in sheep sera.

A novel indirect enzyme-linked immunosorbent assay (ELISA) for antibodies against abortion strains of Chlamydia psittaci (C. psittaci) has been developed. The antigen used was chlamydial elementary bodies treated sequentially with N-lauroyl sarcosine and n-octyl-beta-D-glucopyranoside and finally solubilized with N-lauroyl sarcosine and dithiothreitol. Treating the antigen with sodium periodate after coating of the plates increased the specificity for antibodies to abortion strains. The test was evaluated initially with sera from experimentally infected sheep and an uninfected control group. These sheep were monitored for lambing performance and infection status. When used in conjunction with the indirect micro-immunofluorescence test (MIF), the ELISA was able to identify as negative all twenty-five sera from ewes that had no typical placental lesions and identified as positive twenty of twenty-one sera from infected ewes that had either typical placental lesions or had been found positive by isolation of chlamydia in cell culture. The combination of ELISA and MIF was also able to discriminate correctly groups of sera from six flocks with a history of infection from four known uninfected flocks.

Abortion, Veterinary↗