DNA relatedness of Thermus strains, description of Thermus brockianus sp. nov., and proposal to reestablish Thermus thermophilus (Oshima and Imahori)

Aerobic, thermophilic, gram-negative bacteria obtained from Yellowstone National Park that were placed in the genus Thermus on the basis of phenotypic data were examined by chemotaxonomic techniques to determine their peptidoglycan compositions, their respiratory quinones, their mean DNA base compositions, and their levels of DNA-DNA homology as determined by both the filter hybridization and reassociation rate methods. These isolates from hot springs included Thermus aquaticus strains and strains of a new genospecies. We propose the name Thermus brockianus for this new genospecies; strain YS38 is the type strain of this taxon. A collection of 10 strains, including the type strain of "Thermus thermophilus", which were isolated from widely separated geothermal sites, exhibited high levels of DNA-DNA homology with each other and had similar physiological properties. Therefore, we propose that the species Thermus thermophilus (Oshima and Imahori) should be reestablished, with strain HB8 as the type strain.

[Pneumocystis carinii pneumonia in infants with vertically acquired HIV infection in Switzerland]

OBJECTIVE

Review of incidence, clinical picture, therapy, and outcome of Pneumocystis carinii pneumonia (PCP) in infants with vertically-acquired HIV infection in Switzerland.

METHODS

Inquiry among members of the Swiss Pediatrics AIDS Group, review of the data base of the Swiss Neonatal HIV Study and retrospective analysis of the charts from infants with PCP.

RESULTS

Since 1986 PCP has been diagnosed in 10 out of 107 infants with vertically-acquired HIV infection. PCP occurred in 7 infants at the age of 3-6 months and in 3 at the age of 9-11 months. 4 infants showed symptoms related to HIV infection before developing PCP. Before the development of PCP, infection with HIV had been ascertained in 6 infants. In 2 the diagnosis was still unclear and in the 2 remaining the risk of HIV infection was not known. None of the infants was on primary prophylaxis against PCP. Signs and symptoms of PCP included cough and tachypnea (100%) as well as high fever up to 40 degrees C (90%). Transcutaneous oxygen saturation was 70-95%. Chest X-rays revealed interstitial infiltrates in 6 infants, localized infiltrates in 2 and interstitial as well as localized infiltrates in 2. The CD4+ cell count was, with one exception, < 1500/microliters, i.e. below the normal value for age. Side effects of high dose cotrimoxazole were noted in 6 patients. 5 infants required intubation and mechanical ventilation. 4 infants died due to PCP, including 3 of those who required intubation and mechanical ventilation.

CONCLUSIONS

PCP in infants with vertically-acquired HIV infection preferentially occurs at the age of 3 to 6 months and is often lethal, especially in patients requiring intubation. Evaluation for HIV infection should be done as early as possible in order to introduce primary PCP prophylaxis in infants at risk for this opportunistic infection.

High specific activity chemiluminescent and fluorescent markers: their potential application to high sensitivity and 'multi-analyte' immunoassays

The sensitivities of immunoassays relying on conventional radioisotopic labels (i.e. radioimmunoassay (RIA) and immunoradiometric assay (IRMA) permit the measurement of analyte concentrations above ca 10(7) molecules/ml. This limitation primarily derives, in the case of 'competitive' or 'limited reagent' assays, from the 'manipulation errors arising in the system combined with the physicochemical characteristics of the particular antibody used; however, in the case of 'non-competitive' systems, the specific activity of the label may play a more important constraining role. It is theoretically demonstrable that the development of assay techniques yielding detection limits significantly lower than 10(7) molecules/ml depends on: (1) the adoption of 'non-competitive' assays designs; (2) the use of labels of higher specific activity than radioisotopes; (3) highly efficient discrimination between the products of the immunological reactions involved. Chemiluminescent and fluorescent substances are capable of yielding higher specific activities than commonly used radioisotopes when used as direct reagent labels in this context, and both thus provide a basis for the development of 'ultra-sensitive', non-competitive, immunoassay methodologies. Enzymes catalysing chemiluminescent reactions or yielding fluorescent reaction products can likewise be used as labels yielding high effective specific activities and hence enhanced assay sensitivities. A particular advantage of fluorescent labels (albeit one not necessarily confined to them) lies in the possibility they offer of revealing immunological reactions localized in 'microspots' distributed on an inert solid support. This opens the way to the development of an entirely new generation of 'ambient analyte' microspot immunoassays permitting the simultaneous measurement of tens or even hundreds of different analytes in the same small sample, using (for example) laser scanning techniques. Early experience suggests that microspot assays with sensitivities surpassing that of isotopically based methodologies can readily be developed.

Relationship of high density lipoprotein cholesterol with total and free testosterone and sex hormone binding globulin

A cross-sectional study was performed to see if the previously described association between high density lipoprotein (HDL) cholesterol and plasma total testosterone concentration reflected a relationship with free testosterone or with sex hormone binding globulin (SHBG). In 295 employed middle-aged men, measurements were made of total testosterone and SHBG in serum and of testosterone in saliva, and also of plasma total and HDL cholesterol, plasma triglycerides and other factors which might influence HDL cholesterol levels such as body mass index, alcohol and smoking habits and thyroid hormone levels. In a multiple regression analysis using the GLIM package programme total testosterone concentrations had a persistent positive association with HDL cholesterol (t = 3.5, P less than 0.001) - this association was independent of SHBG (which had a negative association with HDL: t = -1.8, P less than 0.07. The association of HDL cholesterol with testosterone was independent of and stronger than the association of HDL cholesterol with body mass index, alcohol intake and cigarette smoking. Salivary testosterone (a measure of the circulating free hormone) also had a positive independent association with HDL cholesterol. The relationship between HDL cholesterol and testosterone thus appears to reflect an association with circulating hormone levels rather than with the hormone binding globulin.