Rapid diagnosis of experimental meningitis by bacterial heat production in cerebrospinal fluid

BACKGROUND: Calorimetry is a nonspecific technique which allows direct measurement of heat generated by biological processes in the living cell. We evaluated the potential of calorimetry for rapid detection of bacterial growth in cerebrospinal fluid (CSF) in a rat model of bacterial meningitis. METHODS: Infant rats were infected on postnatal day 11 by direct intracisternal injection with either Streptococcus pneumoniae, Neisseria meningitidis or Listeria monocytogenes. Control animals were injected with sterile saline or heat-inactivated S. pneumoniae. CSF was obtained at 18 hours after infection for quantitative cultures and heat flow measurement. For calorimetry, 10 microl and 1 microl CSF were inoculated in calorimetry ampoules containing 3 ml trypticase soy broth (TSB). RESULTS: The mean bacterial titer (+/- SD) in CSF was 1.5 +/- 0.6 x 108 for S. pneumoniae, 1.3 +/- 0.3 x 106 for N. meningitidis and 3.5 +/- 2.2 x 104 for L. monocytogenes. Calorimetric detection time was defined as the time until heat flow signal exceeded 10 microW. Heat signal was detected in 10-microl CSF samples from all infected animals with a mean (+/- SD) detection time of 1.5 +/- 0.2 hours for S. pneumoniae, 3.9 +/- 0.7 hours for N. meningitidis and 9.1 +/- 0.5 hours for L. monocytogenes. CSF samples from non-infected animals generated no increasing heat flow (<10 microW). The total heat was the highest in S. pneumoniae ranging from 6.7 to 7.5 Joules, followed by L. monocytogenes (5.6 to 6.1 Joules) and N. meningitidis (3.5 to 4.4 Joules). The lowest detectable bacterial titer by calorimetry was 2 cfu for S. pneumoniae, 4 cfu for N. meningitidis and 7 cfu for L. monocytogenes. CONCLUSION: By means of calorimetry, detection times of <4 hours for S. pneumoniae and N. meningitidis and <10 hours for Listeria monocytogenes using as little as 10 microl CSF were achieved. Calorimetry is a new diagnostic method allowing rapid and accurate diagnosis of bacterial meningitis from a small volume of CSF

Heat production in different populations of human blood cells exposed to immune complexes in vitro : The importance of the Fc parts of immunoglobulins and the influence of active complement

By use of a batch microcalorimeter of the thermopile type, heat production was measured in isolated populations of human peripheral blood cells exposed to defined immune complexes formed in vitro. It was found that most of the heat production recorded in whole blood after admixture of immune complexes occurs in the granulocytes. Under these conditions small but constantly higher activation values were found in the absence of active complement. It was shown that complexes consisting of antigen and F(ab)2 fragments prepared from the specific antibodies were able to initiate heat production in the cells only in the presence of active complement. These experiments indicate that immune complexes are able to induce increased heat production in the cells either by binding to Fc receptors or by activation of complement through the alternative pathway and subsequent binding of the generated C3b to C3b receptors on the heat-producing cells

Discontinuous ventilation in the rhinoceros beetle Oryctes nasicornis: Direct and indirect calorimetry

Discontinuous gas exchange cycles (DGCs) are frequently observed with insects, i.e. oxygen take up and carbon dioxide release occur interrupted by periods of a few minutes up to many hours. The paper presents direct and indirect calorimetric experiments on DGCs of the scarabid rhinoceros beetle Oryctes nasicornis. A direct/indirect calorimetric experiment is presented. Total and specific heat production rates amount to 0.56 mW and 0.42 mW g in the first period without DGCs and to 0.43 mW (0.32 mW g ) in the second phase, resp. The mean DGC amplitude is 0.184 mW and thus between 33 and 66% of the total turnover

Influence of pretreatments on metabolism and wounding response of fresh cut potatoes evaluated with isothermal calorimetry”. Acta Horticulturae, 682, vol.3: 1833-1838, 2005.

The anti-browning effects of acidificant and antioxidant substances in potatoes have been broadly studied in the literature. However, to our knowledge there is no information about their effects on the metabolism of the wounded tissue. We here have studied the influence of anti-browning substances on the metabolism of fresh-cut potatoes. Cylinders were prepared from potatoes and treated with solutions of citric and ascorbic acid, and of a citric-ascorbic acid combination. The metabolic heat production was measured in closed glass ampoules in a TAM Air isothermal calorimeter for 24 hours at 20°C. Interestingly, the results showed that all the treatments accelerated the metabolism of the samples, e.g. the treated potato pieces consumed the oxygen inside the calorimeter ampoules about 8h before than the untreated samples (control). The effect of ascorbic and in particular of citric acid on the measured metabolic heat was mainly on “normal” metabolic activity rather than on the wounding response