Group A rotaviruses are the most common cause of dehydrating diarrhea in infants and young children worldwide, with more than 2 million hospitalizations yearly and approximately 440,000 deaths. It is estimated that 82% of rotavirus deaths occur in children in the poorest countries (23). Rotavirus transmission occurs mainly by the fecal-oral route, although respiratory transmission has been suggested to occur (7).Rotavirus infection was thought to be limited to the gastrointestinal tract. However, respiratory symptoms and rotavirus shedding in nasopharyngeal secretions have been reported in children with and without gastrointestinal symptoms (19,26,42). Rotavirus antigen was detected in the lung of 1 of 13 experimentally infected 3-week-old conventional pigs at postinoculation day 2 (30) and in liver and kidney specimens from immunodeficient children (9). Rotavirus RNA has also been detected in cerebrospinal fluid and blood of children with central nervous system disease (20,34). Recently, Blutt and colleagues (2) detected rotavirus antigenemia in the serum of children, mice, rabbits, and calves. They further demonstrated that serum from infected mice induced rectal rotavirus antigen shedding after oral inoculation of rotavirus-negative adult mice with the serum. Previously, another enteric virus, the porcine enteric calicivirus (PEC), has also been associated with transient viremia (infectious virus in serum) after oral inoculation of gnotobiotic pigs (11).We choose gnotobiotic pigs because they constitute an animal model of HRV-induced disease. Their gastrointestinal tract physiology and their development of mucosal immunity resemble that of humans. These similarities with HRV infections of infants allow us to establish correlations which could be applied for rotavirus vaccine development (14,25) The question addressed in our study was whether an attenuated human rotavirus and virulent HRV causes upper respiratory tract infections or viremia in naïve neonatal gnotobiotic pigs after various routes of inoculation. In this study we evaluated nasal and rectal virus shedding and viremia after oral, intranasal, feeding tube (gavage), and intravenous inoculation of neonatal gnotobiotic pigs with the Wa strain of attenuated HRV or virulent HRV. The presence of infectious virus in serum of gnotobiotic pigs after oral inoculation with Wa HRV was also investigated by oral and intravenous reinoculation of gnotobiotic pigs with a pool of the HRV-positive sera. MATERIALS AND METHODSVirus. The attenuated cell culture-adapted Wa strain HRV (P1A [8]G1), derived from the 27th HRV passage in African Green monkey kidney cells (MA104) and the virulent Wa HRV from pooled intestinal contents of gnotobiotic pigs were used for inoculation of the gnotobiotic pigs at doses of 5 ϫ 10 7

An actinomycete, isolated as a contaminant of a culture medium containing 25% NaCl, has been classified as Actinopolyspora halophila gen. et sp. nov. in the family Nocardiaceae. The morphology and biochemical characteristics of this organism distinguish it from other members of the family Nocardiaceae and other genera possessing a type IV cell wall. It requires high NaCl concentrations for growth and can grow in saturated NaCl. The lowest concentration permitting growth in liquid medium is 12%, and on solid medium, 10%. Colonies developing at lower salt concentrations contain holes resembling viral plaques. No growth occurred in a medium containing 30% KCl instead of NaCl. This organism can grow in simple media with NH4+ salts as nitrogen source and different sugars and other compounds as carbon source. Though it has a salt requirement almost as great as the extremely halophilic rods and cocci, it differs from these in containing diaminopimelic acid and in sensitivity to lysozyme; both properties suggest that it has a mucopeptide cell wall. It also contains some phospholipids common to other actinomycetes, but does not contain any phytanyl ether linked lipids characteristic of other extremely halophilic bacteria.

Growth of Halobacterium cutirubrum, H. salinarium, and H. halobium was followed by viable counts and optical density measurements. The last species, which grows most vigorously, was most intensively studied.The increase of optical densities and the increase in viable counts corresponded through the exponential growth phase. Dead cells did not lyse, and viable counts were needed to show that after the stationary phase was reached some cultures died off rapidly. Others remained stable for several days. Potassium can limit growth in synthetic media; in all media abundant growth could be obtained only when about 1 mg/ml K+ was present. Growth was stimulated by glycerol, certain carbohydrates, related metabolites, and vitamins. The most effective growth-promoting vitamins tested were thiamine, folic acid, biotin, and vitamin B12. Metabolites that stimulated growth were galactose, glucose, sodium lactate, and glutamine. One-tenth percent glycerol, sodium succinate, and sodium pyruvate were stimulatory, although 2.0% concentrations were inhibitory. Though carbohydrates may stimulate growth, the medium does not become acid; this may explain why standard bacteriological tests indicate that many extreme halophiles do not "utilize" carbohydrates. H. halobium produced considerable acid only when grown in the presence of 2% glycerol.

Quantitative measurements were carried out on pigmented and colorless isoprenoid compounds in several species of extremely and moderately halophilic bacteria. Phytoene was found in most extreme halophiles; it was present in high concentrations in a moderately halophilic coccus (H5) and absent from a moderately halophilic rod (A31C). Only the pigmented extreme halophiles contained β-carotene. Halobacterium cutirubrum contained substantial amounts of lycopene; this compound was present only in small amounts or missing from the other bacteria. Though lycopene is a precursor of β-carotene in plants, there was no correlation between the amounts of lycopene and β-carotene in the different bacterial species. C50 pigments (bacterioruberins) were found only in pigmented extreme halophiles. There was no consistent correlation between the amounts of C40 and C50 compounds in these bacteria. This suggests that the latter may have a biosynthetic pathway independent of the former.Squalene, dihydrosqualene, and tetrahydrosqualene were found in most of the bacteria studied. Menaquinone was found in all species, except the moderately halophilic rod A31C which contained ubiquinone instead. The visual pigment retinal was found in most of the pigmented extreme halophiles, but was not detected in the moderate halophiles.

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