Biomedical subjects
Publications and source records attributed to D F Brown.
Results with the E-Test minimum inhibitory concentration (MIC) method correlated well with an agar dilution method in tests using a wide range of selected bacteria. Detection of methicillin resistance in Staphylococcus aureus was as reliable as agar dilution and disk diffusion methods. The ease of use of the E-Test makes it particularly suitable for routine clinical microbiology laboratories.
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AIMS: To survey blood culture methods in use in the United Kingdom. METHODS: A questionnaire was distributed to the 415 United Kingdom laboratories participating in the clinical bacteriology subscheme of the UK National External Quality Assessment Scheme for Microbiology. RESULTS: Two hundred and eighty seven laboratories completed the questionnaire. The responses indicated wide variations in methods used including considerable differences among laboratories using the same basic methods. The most widely used techniques were the Bactec and conventional broth systems. CONCLUSIONS: Although many published comparisons have failed to show that any basic method is outstandingly successful in the isolation of all organisms, there is evidence that several factors can contribute to good performance. In some laboratories suboptimal conditions were in use. The variations in technique probably reflect differences in practical suitability of a system for any particular laboratory, costs, and personal preferences.
It has been demonstrated that the ventromedial hypothalamus (VMH) of alloxan-induced diabetic mice is protected from subsequent gold thioglucose (GTG)-induced lesions. Another compound, 3,3'-methyliminobis-(N-methylpropylamine) (MIMPA), a triamine structurally unrelated to GTG, has been shown to cause similar VMH lesions in mice. We chose to investigate the effect of alloxan-induced diabetes on VMH lesion formation in MIMPA-treated mice. In this study CF-1 female mice were made diabetic by a simple intravenous (IV) injection of alloxan and subsequently treated with MIMPA by subcutaneous injection (SC). Contrary to studies which showed that GTG-induced VMH lesions are insulin dependent, an insulin deficiency did not inhibit MIMPA-induced lesions in the VMH of mice. Our data suggests, albeit GTG is suspected to induce VMH necrosis by attaching to glucoreceptors and insulin-sensitive neurons, MIMPA works by a different and as yet unknown mechanism. We conclude that MIMPA-induced lesions in the VMH of mice are not insulin dependent.
Age-related changes in psychological measurements of pain and well-being were studied in patients undergoing full fixed appliance orthodontic treatment. A longitudinal series of four questionnaires was used to obtain measurements of these factors after the separation phase of treatment, banding (2 to 7 days after separation), the first adjustment visit (3 to 4 weeks after placement of full fixed appliances), and the second adjustment visit (3-4 months after banding was completed). The results suggest an interaction between the phases of treatment and reported pain and psychological well-being and significant differences in the response profiles of the adolescent age group (14 to 17 years) compared to the preadolescent (11 to 13 years) and adult groups (18 years and older). These findings did not appear to be due simply to group differences in the use of analgesics, class of malocclusion, or type of full fixed appliance used. The profile comparisons indicated that the adolescent age group generally reported lower levels of psychological well-being and higher levels of pain during the phases of treatment examined. Consistent with these results was the finding that the adolescents differed from the preadolescents and adults in the quality of the pain experience reported during treatment. The results indicate an age difference in adjustment to fixed orthodontic therapy, which suggests that adolescents are more vulnerable to undesirable psychological effects of treatment.
The mechanism of nitrofuran resistance in Salmonella enteritidis phage type 4 was studied. Nitrofuran reductase activity was inversely related to the furazolidone MIC for the organism. Strains with low-level nitrofuran resistance, typically found in almost all isolates of S. enteritidis PT4, had intermediate nitrofuran reductase activity. Disc diffusion tests with furazolidone, 15 or 50 micrograms discs, and nitrofurantoin, 50 or 300 micrograms discs, failed to distinguish reliably between susceptible populations and those with low-level resistance. In order to detect low-level resistance to nitrofurans a dilution method should be used with a furazolidone breakpoint of 1 mg/l or a nitrofurantoin breakpoint of 16 mg/l.
The 'E test' is a method for measuring MICs of antimicrobial agents against bacteria and is based on diffusion of a pre-formed antibiotic gradient from a plastic strip. The performance of the E test was evaluated by comparison with a conventional agar dilution MIC method in tests with ten agents and a variety of organisms. Correlation between MICs by the agar dilution and E test methods was good, 98.85% results were within 2 log2 dilution steps in a total of 1304 tests. The E test is technically straightforward as tests are set up in the same way as the disc diffusion method. The versatility and ease of use of the E test make the method an attractive alternative to conventional dilution tests.
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An average of 358 (13%) of United Kingdom laboratories failed to detect resistance to chloramphenicol in strains of Haemophilus influenzae distributed by the United Kingdom National External Quality Assessment Scheme for Microbiology. Clear associations between methods used and results obtained show that error rates are minimised by the use of low content (10 micrograms) disc and a sensitive control strain of H influenzae.
Life-threatening episodes of ventricular tachycardia were documented in a patient with an implanted Omni-Stanicor pacemaker due to episodic pacemaker runaway. The unit generated impulses at rates varying from 73 to 500 per minute. Ventricular capture at high rates was variable, but frequently resulted in heart rates in excess of 200 per minute. These episodes were associated with loss of consciousness secondary to inadequate cardiac output. Although the pacemaker could be inactivated by reprogramming its output to 2 mA, and suppressed by chest wall stimulation with an external pulse generator, no spontaneous rhythm resulted during these maneuvers. Urgent removal of the battery at the bedside and immediate resumption of pacing with an external generator was required to resolve the problem. Although runaway is infrequent with current generation pacemakers, it should be considered in addition to the more common causes of pacemaker malfunction in the patient with appropriate symptoms.
The effects of epinephrine on cyclic AMP content and protein kinase activity were examined in an in situ rat heart preparation. Bolus injection of epinephrine into the superior vena cava caused an increase in the activity ratio (-cyclic AMP/"cyclic AMP) of 12 000 X g supernatant protein kinase. The increase was significant within 5 s and maximal in 10 s. Epinephrine produced a dose-dependent increase in both protein kinase activity ratio and cyclic AMP content. The increases in both parameters exhibited a high degree of correlation. The increase in protein kinase activity ratio observed with low doses of epinephrine (less than or equal to 1 microgram/kg) resulted from an increase in independent protein kinase activity (-cyclic AMP) without a change in total protein kinase activity (+cyclic AMP). However, the increase in the activity ratio observed with higher doses of epinephrine (greater than 1 microgram/kg) was due mainly to a decrease in total protein kinase activity rather than a further increase in independent protein kinase activity. The loss of supernatant total protein kinase activity could be accounted for by an increase in activity associated with particulate fractions obtained from the homogenates. A similar redistribution of protein kinase could be demonstrated by the addition of cyclic AMP to homogenates prepared from hearts not stimulated with epinephrine. These results demonstrate that epinephrine over a wide dose range produces a parallel increase in the content of cyclic AMP and the activation of soluble protein kinase. The findings also suggest that protein kinase translocation to particulate material may depend on the degree of epinephrine-induced enzyme activation.
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The aetiological agent of contagious equine metritis (CEM) has been investigated bacteriologically in a wide range of cultural and conventional biochemical tests, in the eletron microscope, for DNA base composition (36.1 per cent GC), for susceptibility to various antimicrobial agents and antigenically by means of tube and slide agglutination tests. The organism is a fastidious, Gramnegative, non acid-fast coccobacillus which in biochemical tests is very unreactive. In conventional tests, only the oxidase, catalase and phosphatase tests were positive. Dependance on neither X nor V factors could be demonstrated, but some stimulation of growth by X factor was observed. The organism could not be identified with any known species and even allocation to an appropriate characters, we propose the organism as a new species of the genus Haemophilus: H. equigenitalis, type strain NCTC 11184 (61717/77).
A strain of Vibrio parahaemolyticus, serotype O4/K4, that was Kanagawa positive and reactive in the rabbit ileal loop test, was isolated in low numbers from raw oysters implicated in a case of acute gastroenteritis. To our knowledge, this is the first report of the isolation of a Kanagawa-positive strain from suspect food in the United States.
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