Detection of arbovirus antibodies in avian sera by the complement fixation-inhibition test.

The complement fixation-inhibition (CFI) test was described for the detection of antibodies to arboviruses in bird sera. The CFI antibody present in bird sera inhibited the standard complement-fixation reaction of a reference complement-fixing antigen-antibody pair. Using reference antigens (St. Louis encephalitis, eastern equine encephalomyelitis, western equine encephalomyelitis, and yellow fever) prepared from infected mouse brains and reference antisera prepared in rabbits or horses, reproducible CFI antibody titers were obtained in artificially immunized chickens. Time-course studies on the CFI immune response in birds inoculated with live St. Louis encephalitis virus indicated that the CFI antibody was distinct from the antibody detected by the hemagglutination-inhibition test.

Detection of coagulase activity in Erysipelothrix rhusiopathiae.

Coagulase activity was detected in 99% of 225 strains of Erysipelothrix rhusiopathiae. These strains included isolates from a variety of animal and environmental sources. Activity could be detected by the tube or slide technique, with the tube reactions being easier to interpret. Coagulation of rabbit and/or bovine plasma was observed, with most strains reacting in both. The activity appeared to be a common characteristic of the species and may be useful in differentiating E. rhusiopathiae from Listeria and Corynebacterium species, which fail to demonstrate the activity. There was no correlation noted between coagulase activity and the serotype, source, geographic origin, or virulence (as detected by mouse pathogenicity tests) of the isolates.

Arginine biosynthesis in Legionella pneumophila: absence of N-acetylglutamate synthetase.

Legionella pneumophila was unable to grow in a chemically defined medium without arginine because it could not carry out the first step in the biosynthetic pathway, the conversion of glutamate to N-acetylglutamate. All strains examined could grow when N-acetylglutamate (or other later arginine precursors) were substituted for arginine. No activity corresponding to N-acetylglutamate synthetase could be detected in cell extracts of L. pneumophila.

Growth of Legionella pneumophila in defined media: requirement for magnesium and potassium.

The inorganic ions magnesium and potassium were required for optimal growth of Legionella pneumophila in a chemically defined medium composed of amino acids and inorganic salts. Optimum growth was obtained at concentrations of approximately 20 micrograms/mL (80 microM) MgSO4 X 7H2O and 150 micrograms/mL (2 mM) KCl. Comparable results were obtained with all six serogroups of L. pneumophila as well as with both laboratory-adapted and animal-passed strains.

Amino acid requirements for Legionella pneumophila growth.

The amino acids L-arginine, L-isoleucine, L-leucine, L-methionine, L-serine, L-threonine, and L-valine were essential for the growth of Legionella pneumophila in a chemically defined medium. A partial requirement for L-cysteine (or L-cystine) was also observed. A minimal medium containing only the eight required amino acids supported the growth of this bacterium only if the medium was supplemented with L-glutamic acid. This latter compound was the only amino acid capable of stimulating growth in the eight-amino acid medium.

Intermediary metabolism in Legionella pneumophila: utilization of amino acids and other compounds as energy sources.

The utilization of amino acids and other compounds as carbon and energy sources by Legionella pneumophila was examined. Based on the stimulation of oxygen consumption in washed-cell suspensions, glutamate, serine, threonine, and tyrosine were the only amino acids which were utilized as energy sources. Other stimulators of oxygen uptake were lactate, pyruvate, acetate, fumarate, and succinate. Citrate was a good stimulator only when the bacteria were grown in the presence of the substrate. Radiolabeling studies showed that [14C]glutamate was rapidly metabolized, with the label distributed evenly in all cell fractions. [14C]pyruvate and [14C]acetate were incorporated into the lipid-containing cell fraction, whereas glucose and glycerol were found in both the lipid- and polysaccharide-containing cell fractions. Radiorespirometry of differentially labeled [14C]glucose indicated that this compound was metabolized primarily by the pentose phosphate and Entner-Doudoroff pathways rather than by the glycolytic pathway.