This study was undertaken to determine the frequency of Legionella infection in a dental clinic setting. Serum samples from 270 dental clinic personnel were evaluated using an enzyme-linked immunosorbent assay to detect Legionella-specific IgM and IgG antibodies. The pooled-species whole-cell-antigen preparation used in these assays was derived from six Legionella pneumophila strains and one strain each from Legionella bozemanii and Legionella micdadei. Significant levels of IgG and IgM antibodies were found in 20% and 16%, respectively, of the samples. This compares with 8% and 10%, respectively, for a randomly selected non-clinical group from the region (P less than 0.005). Samples from clinic personnel with significant IgG titers (greater than 1:128) were also evaluated for activity to each of the eight single-species antigens, with the following results: L. pneumophila, 45% (combined six strains); L. micdadei, 37%; and L. bozemanii, 18%. Comparing individuals' "years spent in the clinic environment" with the incidence of significant antibody levels strongly suggests that the risk of Legionella infection increases proportionately with increased clinic exposure time (P less than 0.05). Analysis of these data implies that Legionella may be present in the dental clinic environment, thus creating an increased risk for clinical personnel or patients.

The in vitro metabolic activities of two monocytic species of Ehrlichia were investigated. The Miyayama strain of Ehrlichia sennetsu and two strains of Ehrlichia risticii, isolated in Illinois and Maryland, were cultivated in a P388D1 mouse macrophage cell line. The ehrlichia particles from heavily infected cultures were separated from host constituents by a Renografin gradient centrifugation procedure modified from those employed for rickettsiae and chlamydiae. The metabolic activities of the isolated ehrlichiae were measured by their formation of CO2 after incubation for 1 h or longer at 34°C with 14C-labeled substrates. Of the substrates tested, glutamine was utilized most vigorously. The greatest activity was obtained at pH 7.2 to 8.0, while the activity rapidly declined at pH below 7. The most favorable buffer was one that contained 0.05 M potassium phosphate as well as 0.2 M sucrose, thus affording some osmotic protection. Glutamate was utilized to a much lesser extent than glutamine, and glucose was not utilized at all. No consistent differences in metabolic activities among the three strains were observed.During the past several years there has been a resurgence of veterinary, medical, and biological interest in the genus Ehrlichia, previously believed to include only veterinary pathogens. In 1981 Ristic et al. (21) observed that there was a serological relationship between Rickettsia sennetsu and Ehrlichia canis. This was quickly followed by a report by Hoilien et al. (10), who illustrated the pronounced similarity in the developmental cycles of the two agents. This led to the reclassification of R. sennetsu as Ehrlichia sennetsu by Ristic and Huxsoll (20). E. sennetsu is a human pathogen isolated in 1953 in Japan (15), and until recently it was believed to be confined to a small region of that country (19). E. canis has been recognized for over 50 years as a worldwide pathogen of dogs (20).Cole et al. (3) greatly facilitated the investigation of E. sennetsu by demonstrating that this agent can be cultivated readily in an established cell line, P388D1, derived from murine macrophages. When Potomac horse fever, a disease that made its first appearance in Maryland about a decade ago, was investigated, it became obvious that the etiologic agent was an ehrlichia related to E. canis but more closely related to E. sennetsu (11). The agent was named Ehrlichia risticii (12), and the disease was renamed equine monocytic ehrlichiosis. These findings raise many questions about the ecology and phylogeny of E. sennetsu and E. risticii, which are widely separated geographically and are pathogenic for different mammalian hosts. The possibility that E. canis is the common link and that the dog is the common reservoir was raised by the discovery that E. canis can infect humans and produce a disease that is somewhat similar to Rocky Mountain spotted fever (7,14).Information on the biological properties of Ehrlichia spp. is quite limited. No detailed studies of the metabolic properties of any of the ehrlichiae have been r...

Spirochetes of the genus Leptospira have previously been shown to use an unusual pathway to synthesize isoleucine. For reasons of convenience, we assume that only one unusual pathway is found in the genus, and we refer to it as the pyruvate pathway. We determined the distribution of this pyruvate pathway in representatives of the seven Leptospira DNA hybridization groups. Our method included labeling the representative strains with radioactive carbon dioxide and other radioactive precursors, fractionating the cells, and determining the specific activities (counts detected per nanomole) of the amino acids found in the protein fractions. On the basis of isoleucine biosynthesis, we found that the genus can be classified as follows: class I primarily, if not exclusively, uses the well-known threonine pathway; class II uses mostly the pyruvate pathway, with a minor amount of isoleucine being synthesized via the threonine pathway; and class III uses the pyruvate pathway exclusively. No relationship appears to exist between the degree of DNA hybridization and the classes of isoleucine biosynthesis. Although the precise intermediates on the pyruvate pathway are unknown, the origin of the carbon skeleton of isoleucine synthesized by this pathway is consistent with a borrowing of the leucine biosynthetic enzymes. However, we found that the pyruvate pathway is not controlled by leucine and that the two isoleucine pathways are independently regulated. Finding major and highly evolved multiple biosynthetic pathways of a specific amino acid within one genus is unique, and, conceivably, represents phylogenetic diversity within Leptospira.

An attempt was made to elucidate in Campylobacter spp. some of the physiologic characteristics that are reflected in the kinetics of CO2 formation from four '4C-labeled substrates. Campylobacterjejuni and C. coli were grown in a biphasic medium, and highly motile spiral cells were harvested at 12 h. Of the media evaluated for use in the metabolic tests, minimal essential medium without glutamine, diluted with an equal volume of potassium sodium phosphate buffer (pH 7.2), provided the greatest stability and least competition with the substrates to be tested. The cells were incubated with 0.02 M glutamate, glutamine, a-ketoglutarate, or formate, or with concentrations of these substrates ranging from 0.0032 to 0.125 M. All four substrates were metabolized very rapidly by both species. A feature of many of these reactions, particularly obvious with a-ketoglutarate, was an immediate burst of CO2 production followed by CO2 evolution at a more moderate rate. These diphasic kinetics of substrate utilization were not seen in comparable experiments with Escherichia coli grown and tested under identical conditions. With C. jejuni, C02 production from formate proceeded rapidly for the entire period of incubation. The rate of metabolism of glutamate, glutamine, and aketoglutarate by both species was greatly enhanced by increased substrate concentration. The approach to the study of the metabolism of campylobacters here described may be useful in detecting subtle changes in the physiology of cells as they are maintained past their logarithmic growth phase.

The objective of this study was to evaluate by relatively simple metabolic tests the usefulness of buffers and energy sources commonly used in Legionella growth media. Legionella pneumophila serogroups 1 to 6, Legionella micdadei, and Legionella bozemanii were grown in an enriched charcoal-yeast extract diphasic medium. The cells were washed thrice, suspended in various buffers (pH 6.9) with 1 or 5 mM MgSO4, and used immediately or after controlled-rate cryopreservation. CO2 produced and C incorporated into the cold trichloroacetic acid-insoluble fractions from "4C-labeled substrates were determined. Potassium phosphate buffer (0.02 M) was as satisfactory as organic buffers for glutamate metabolism, but the addition of KCI or NaCI reduced activity. Metabolic activity for glutamate was not lost upon cryopreservation, and cryopreserved cells were used to test the utilization of other single or paired substrates. Rates of activity for serine, glutamate, threonine, and pyruvate, in this descending order, were high, and those for a-ketoglutarate, succinate, and 'yaminobutyrate were low. Although glutamine was not used as rapidly as glutamate, when added to glutamate it was preferentially metabolized, possibly because of more rapid transport. When glutamate and serine were combined, glutamate furnished more C for CO2 and less for incorporation, whereas the reverse was true of serine. In conclusion, glutamate as an energy source may in some cases spare other amino acids for synthesis. a-Ketoglutarate, a common constituent of Legionella media, may reduce oxygen toxicity but is probably not a chief energy source. * Corresponding author. Laboratories, Richmond, Calif.), as specified by the manufacturer. Before the Bio-Rad reagent was added, the cells