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Biomedical subjects

C W Blackburn

Publications and source records attributed to C W Blackburn.

15 recordsLinked to original sources
PubMed2000

Modifications to methods for the enumeration and detection of injured Escherichia coli O157:H7 in foods.

Reliable methods are required for the detection and enumeration of potentially injured E. coli O157 in food in the presence of outnumbering competing bacteria. Selective agents can prevent or inhibit the recovery and subsequent multiplication of injured cells and direct inoculation, either into selective enrichment broths or onto selective agar plates is still used in many methods for E. coli O157 detection and enumeration. When compared with tryptone soya agar (TSA), sorbitol MacConkey agar (SMAC) was shown to underestimate the concentration of viable E. coli O157:H7 subjected to low pH and high NaCl concentration. Using a resuscitation stage on TSA followed by membrane transfer to SMAC improved recovery to levels obtained on TSA. The membrane method was used to monitor the numbers of artificially contaminated E. coli O157:H7 during the fermentation of a meat product and demonstrated better survival when compared to counts on SMAC. Six rapid methods for the detection of E. coli O157 in food (BAX E. coli O157, Reveal 8 E. coli O157-H7 screening test, VIP EHEC, VIDAS E. coli O157 (ECO), EHEC-Tek and Tecra E. coli O157 visual immunoassay), were evaluated using beetburgers, parsley and fermented meat artificially contaminated with injured cells. Methods using direct selective enrichment, with or without an elevated incubation temperature gave false-negative results. The incorporation of a non-selective pre-enrichment medium improved the detection rates of these assays by up to ten fold.

Colony Count, Microbial↗
PubMed1997

Development of thermal inactivation models for Salmonella enteritidis and Escherichia coli O157:H7 with temperature, pH and NaCl as controlling factors.

The thermal inactivation of Salmonella enteritidis phage type 4 and Escherichia coli O157:H7 as affected by temperature (54.5-64.5 degrees C), pH (4.2-9.6 with HCl or NaOH) and NaCl concentration (0.5-8.5% w/w) was studied. Cell suspensions in modified tryptone soya broth were heated in a submerged-coil heating apparatus and survivors were enumerated on tryptone soya agar incubated aerobically. For most thermal inactivation data there was a logarithmic decrease in the viable cell concentration over the initial 4-6 log10 reduction and D-values were fitted. In some cases, tailing of the survivor curves was observed with cells surviving longer than the D-values predicted. Models describing the effect of temperature, pH and NaCl concentration on the thermal inactivation of S. enteritidis and E. coli O157:H7 were produced. For both organisms, predicted z-values of 4.6-7.0 C degrees were obtained depending on conditions, with larger z-values at higher levels of NaCl. Optimum survival occurred between pH 5 and pH 7 and increasing acidity or alkalinity caused a decrease in the predicted D-values. At equivalent pH, acetic acid and lactic acid (at 0.5, 1 and 2% w/w) generally had a similar, or increased, lethal effect compared with HCl, whereas in most cases citric acid had a less lethal effect. For E. coli O157:H7, increasing NaCl concentration had a protective effect up to the maximum tested (8.5% w/w), while for S. enteritidis optimal survival at a NaCl concentration of 5-7% w/w was predicted. The models were validated in foods by comparing predictions with published data. Most (80%) of the predicted D-values from the S. enteritidis model were within the 95% confidence interval (within 2.45-fold of the published data) for different Salmonella serotypes in whole egg, egg albumen, egg yolk, beef and milk. Most (93%) of the predicted D-values from the E. coli O157:H7 model were larger than the limited published data for this organism in meat, poultry, milk and apple juice with 42% within the 95% confidence interval (within 2.05-fold of the published data). The D-value models were incorporated into Version 1, and subsequent versions, of the predictive microbiology software program, Food MicroModel.

Acetic Acid↗
PubMed1996

Evaluation of Petrifilm methods for enumeration of aerobic flora and coliforms in a wide range of foods.

Petrifilm is a ready-to-use alternative to traditional microbial enumeration methods. The Petrifilm Aerobic Count Plate (ACP) and Coliform Count Plate (CCP) were compared with standard methods for the enumeration of the aerobic mesophilic flora and coliform bacteria in 91 foods covering a wide range of different food commodities. There was good correlation between the Petrifilm ACP and the standard aerobic colony count method (r = 0.989) and between the Petrifilm CCP and the standard Violet Red Bile Agar plating method (r = 0.872). In both cases, the Petrifilm methods had a better repeatability than the standard methods. The Petrifilm ACP and CCP were shown to be practical and accurate alternatives to standard enumeration methods in a wide range of foods, with benefits of saving time, labour and incubator space.

Bacteria, Aerobic↗
PubMed1994

Modelling the growth, survival and death of microorganisms in foods: the UK food micromodel approach.

Techniques for the development of mathematical models in the area of predictive microbiology have greatly improved recently, allowing better and more accurate descriptions of microbial responses to particular environmental conditions, thus enabling predictions of those responses to be made with greater confidence. Recognising the potential value of applying these techniques in the food industry, the Ministry of Agriculture, Fisheries and Food (MAFF) initiated a nationally coordinated five-year programme of research into the growth and survival of microorganisms in foods, with the aim of developing a computerised Predictive Microbiology Database in the UK. This initiative has resulted in the systematic generation of data, through protocols which ensure consistency of methodology, so that data in the database are truly comparable and compatible, and lead to reliable predictive models. The approaches taken by scientists involved in this programme are described and the various stages in the development of mathematical models summarized. It is hoped that this initiative and others being developed in the USA, Australia, Canada and other countries, will encourage a more integrated approach to food safety which will influence all stages of food production and, eventually, result in the development of an International Predictive Microbiology Database.

Bacteria↗
PubMed1994

Evaluation of the Vitek Immunodiagnostic Assay System (VIDAS) for the detection of Salmonella in foods.

A Salmonella Assay using the Vitek Immunodiagnostic Assay System (VIDAS) was compared with a conventional cultural method (CCM) for the detection of salmonellas in 141 samples of artificially and naturally contaminated foods. There was an overall agreement of 92.9% between the methods. The productivity of the VIDAS Salmonella Assay (VSA) was not improved using an alternative enrichment protocol for the detection of Salmonella in 12 raw meat samples. The sensitivity and specificity of the VSA was assessed using pure cultures of salmonellas and non-salmonellas. The detection limit was 1.8 x 10(6) salmonellas ml-1 in M-broth and some Citrobacter freundii strains gave false-positive results. Using an immunomagnetic separation (IMS) technique and an abbreviated cultural enrichment, the VSA results could be obtained a day earlier than the standard VSA method.

Bacteriological Techniques↗
PubMed1992

Experiences in lingual nerve repair.

An account is given of the experience gained through the exploration of 23 lingual nerves injured during third molar surgery, including a description of the findings in each case and the repair methods used. Details are given of the results of the preoperative and postoperative assessment. The outcome on the whole has been disappointing, and possible reasons for this are discussed. The discussion includes an evaluation of the use of somatosensory evoked potentials as part of the diagnostic method.

Blood Loss, Surgical↗
PubMed1990

A method of assessment in cases of lingual nerve injury.

A method for assessing lingual sensation is described, comprising sensory testing, using touch and moving two-point discrimination and patient subjective reporting. The clinical application is seen to be the evaluation of lingual nerve injury consequent upon lower third molar surgery. Using this method it is considered possible to identify many of those patients unlikely to make full spontaneous recovery at the stage of 3 months following injury, with a view to achieving an earlier timing of surgical repair than that which prevails at present.

Adolescent↗
PubMed1990

Spindle-cell carcinoma: a case report.

An unusual case of an exophytic spindle-cell carcinoma of the maxilla arising from an area of erythroplakia is presented. The epithelial nature of the spindle cells was demonstrated by electron microscopy and immunohistochemistry. After initial surgery the tumour recurred and was then extensively infiltrative and rapidly destructive. Magnetic resonance imaging (MRI) revealed an invasive tumour of the contra-lateral maxillary antrum suggesting a multicentric origin.

Aged↗
PubMed1989

Lingual nerve damage associated with the removal of lower third molars.

In a study of 1117 consecutive surgical procedures by a variety of operators to remove a lower third molar, the incidence of lingual nerve damage was determined to be 11%. Slightly more than half the cases made a full recovery within 6 weeks. All who would recover fully did so within 36 weeks. Six cases (0.5%) in the series failed to make a full recovery. Most strongly implicated in the temporary dysaesthesias was the raising and retraction of the lingual mucoperiosteal flap, especially in the case of unerupted teeth, when general anaesthesia was used. A variable incidence was found between individual operators. Cases of permanent damage arose when distal bone was removed with a bur, despite the use of a lingual flap retractor. The high incidence of lingual nerve damage in this series suggests that dental surgeons should be much more alert to the danger of this complication, and also that a warning of its possible occurrence should be given as part of the process of obtaining informed consent to operation.

Humans↗
PubMed1988

Blue rubber-bleb naevus syndrome.

A case is reported of a patient who presented with facial pain and was found to have phleboliths associated with venous anomalies of the face and neck. Systemic investigation revealed a microcytic, hypochromic anaemia which was the result of haemorrhage from multiple haemangiomas of the gastro-intestinal tract. The finding of anaemia together with cutaneous and intestinal haemangiomas fits with a diagnosis of blue rubber-bleb naevus syndrome.

Adult↗
PubMed1987

Trigeminal somatosensory evoked potentials. A review of the literature as applicable to oral dysaesthesias.

Oro-facial sensory impairment is a common event following third molar extractions, osteotomies and maxillo-facial trauma. Trigeminal somatosensory-evoked potentials (TSEPs) may offer an objective means of assessing neuronal function in such cases. TSEPs may be recorded non-invasively in man following peripheral stimulation of the trigeminal nerve, the principal nerve of oro-facial sensation. TSEP recording has gained popularity over the last decade and it is thus timely to review experimental methods and proven clinical applications in the light of recent interest in this technique within oral and maxillo-facial surgery.

Animals↗
PubMed1982

Lung water quantitation by nuclear magnetic resonance imaging.

Nuclear magnetic resonance imaging was used to determine quantitatively the water distribution of saline-filled and normal rat lungs in both isolated lung and in situ preparations. Regional lung edema was easily detected. Studies of an isolated lung fragment indicate an accuracy of better than 1 percent and images of H2O/D2O phantoms indicate an average error of 2.7 percent.

Animals↗
PubMedDate not supplied

Nicotine, but not cotinine, has a direct toxic effect on ovarian function in the immature gonadotropin-stimulated rat.

PMSG-primed and hCG-triggered rat ovaries were exposed to nicotine and its major metabolite, cotinine, using in vitro and in vivo experimental approaches. In vivo, a dose-dependent reduction in oocytes within the fallopian tube was noted in nicotine treated rats (6.25 ng/g animal weight, P < 0.001). Serum estradiol concentrations were also reduced in rats receiving nicotine (P < 0.04). There were no significant differences in weight gain. Cotinine had no effects. In vitro, nicotine also caused a dose-dependent reduction in oocytes in the collection chamber (P < 0.0001). Estradiol levels in nicotine-treated perfusions were reduced and reached statistical significance at 7 h (P < 0.003). The in vitro fertilization rate was reduced for nicotine-treated perfusions exposed to 1.43 pg/mL of nicotine (P < 0.001). Cotinine had no effect in vitro. We conclude that nicotine inhibits ovulation, estradiol production, and fertilization both in vivo and in vitro in rat models of ovulation. Cotinine did not affect these parameters. These effects of nicotine are notably independent of nicotine's known effect on the midcycle gonadotropin surge.

Animals↗