Microhotplate Temperature Sensor Calibration and BIST.

In this paper we describe a novel long-term microhotplate temperature sensor calibration technique suitable for Built-In Self Test (BIST). The microhotplate thermal resistance (thermal efficiency) and the thermal voltage from an integrated platinum-rhodium thermocouple were calibrated against a freshly calibrated four-wire polysilicon microhotplate-heater temperature sensor (heater) that is not stable over long periods of time when exposed to higher temperatures. To stress the microhotplate, its temperature was raised to around 400 °C and held there for days. The heater was then recalibrated as a temperature sensor, and microhotplate temperature measurements were made based on the fresh calibration of the heater, the first calibration of the heater, the microhotplate thermal resistance, and the thermocouple voltage. This procedure was repeated 10 times over a period of 80 days. The results show that the heater calibration drifted substantially during the period of the test while the microhotplate thermal resistance and the thermocouple-voltage remained stable to within about plus or minus 1 °C over the same period. Therefore, the combination of a microhotplate heater-temperature sensor and either the microhotplate thermal resistance or an integrated thin film platinum-rhodium thermocouple can be used to provide a stable, calibrated, microhotplate-temperature sensor, and the combination of the three sensor is suitable for implementing BIST functionality. Alternatively, if a stable microhotplate-heater temperature sensor is available, such as a properly annealed platinum heater-temperature sensor, then the thermal resistance of the microhotplate and the electrical resistance of the platinum heater will be sufficient to implement BIST. It is also shown that aluminum- and polysilicon-based temperature sensors, which are not stable enough for measuring high microhotplate temperatures (>220 °C) without impractically frequent recalibration, can be used to measure the silicon substrate temperature if never exposed to temperatures above about 220 °C.

Community-acquired pneumonia and bacteremia due to methicillin-resistant Staphylococcus aureus carrying Panton-Valentine-leukocidin gene in Greece: two case reports and literature review.

We report the first two cases of community-acquired necrotizing pneumonia and bacteremia complicated by acute respiratory distress syndrome (ARDS) due to Panton-Valantine leukocidin-producing methicillin-resistant Staphylococcus aureus (MRSA-PVL) in Greece, together with a short literature review. Diagnosis was made by culture and broad spectrum PCR of respiratory secretions and blood. One patient received appropriate therapy and recovered fully. The other one died rapidly due to septic shock and life-threatening hemoptysis. Clinicians should be suspicious of community-acquired pneumonia due to MRSA-PVL strain, because rigorous microbiological diagnosis, early and appropriate therapy is essential for favorable outcome.

Adjuvant nitrosourea therapy for glioblastoma.

An attempt was made to evaluate the potential advantages of chemotherapy in the treatment of 62 patients with glioblastoma. Twenty-four of the 62 patients received adjuvant nitrosourea chemotherapy with carmustine (BCNU), lomustine (CCNU), or semustine (methyl CCCNU) in addition to surgery and radiotherapy. Thirty-three of the 62 patients were involved in a controlled, prospective, randomly allocated study. Quality or quantity of survival was not prolonged in patients who received chemotherapy. Age greater than 64 years, a severe postoperative neurological deficit, or the onset of symptoms less than 12 months prior to surgery were associated with a worse prognosis. The valid evaluation of the effect of a form of treatment on survival in patients with glioblastoma is contingent on the regorous avoidance of preselected factors that may predispose the treated group to a more favorable prognosis.

Molecular epidemiology of ampicillin-resistant clinical isolates of Salmonella enteritidis.

During the last 6 years in Greece, there has been a significant increase in the number of ampicillin-resistant Salmonella clinical isolates reported. In this study 23 ampicillin-resistant Salmonella strains, consecutively isolated from patients with epidemiologically unrelated cases of food poisoning, were investigated. By serotyping and phage typing, 21 of these strains were identified as Salmonella enteritidis phage type 6a, 1 was identified as Salmonella typhimurium, and 1 was identified as Salmonella saintpaul. By plasmid pattern analysis, the 21 S. enteritidis strains were further differentiated into five groups. Group I consisted of 5 strains (carrying two plasmids of ca. 38 and 34 MDa), group II consisted of 10 strains (three plasmids of ca. 38, 34, and 2.5 MDa), group III consisted of 3 strains (four plasmids of ca. 38, 34, 15, and 2.5 MDa), group IV consisted of 1 strain (five plasmids of ca. 100, 38, 34, 24, and 15 MDa), and group V consisted of 2 strains (three plasmids of ca. 100, 38, and 24 MDa). Ampicillin resistance was easily transferred to Escherichia coli and was associated with the transfer of the 34-MDa plasmid, classified in the N incompatibility group for all strains of groups I to IV, and with the transfer of the 100-MDa plasmid for the group V strains. EcoRI restriction endonuclease digestions showed an extensive homology among the 34-MDa conjugative R plasmids. Hybridizations of the EcoRI restriction fragments of the 34-MDa plasmids with a TEM-type probe revealed the locus of the beta-lactamase gene to be situated on a ca. 6.6-MDa fragment, common in all plasmids. These results indicate that ampicillin resistance in Greece is due to the spread of a limited number of clones of S. enteritidis phage type 6A, carrying related 34-MDa R plasmids. Work is in progress to obtain a better understanding of ampicillin resistance in S. enteritidis.

Indications of in vivo transfer of an epidemic R plasmid from Salmonella enteritidis to Escherichia coli of the normal human gut flora.

The presence of conjugative R plasmids as well as the possible similarities among them were studied in nine ampicillin-resistant Salmonella enteritidis isolates and nine ampicillin-resistant Escherichia coli isolates from the normal fecal flora that were simultaneously isolated from nine epidemiologically unrelated outpatients. It was found that in eight patients, ampicillin resistance in S. enteritidis was encoded by ca. 34-MDa transferable plasmids very similar to those found in a recent study of the epidemiology of ampicillin-resistant S. enteritidis in Greece (A.C. Vatopoulos, E. Mainas, E. Balis, E.J. Threlfall, M. Kanelopoulou, V. Kalapothaki, H. Malamou-Lada, and N.J. Legakis, J. Clin. Microbiol. 32:1322-1325, 1994). Moreover, transferable R plasmids with the same molecular size and restriction pattern were found in the normal flora E. coli of two of these patients. This finding, if confirmed by further studies, is consistent with the hypothesis that normal flora E. coli could act as a reservoir of resistant genes and, consequently, as a factor in the dissemination of these genes among pathogens of human and animal origin such as Salmonella spp. and needs to be examined further.