Four hepatitis C virus transmission chains at three dialysis units were disclosed by limited sequencing; three of these were disclosed by analysis of the NS5-B region of the genome. Dialysis on the same shift as that during which infected patients were dialyzed was the common factor for seven patients in two chains. Two nurses exposed to needle sticks and their sources of infection constituted two other chains. The strains of three chains belonged to subtype 1a and formed clusters with an intrachain variability of 0 to 6 nucleotides compared to 8 to 37 nucleotides for unrelated strains within this subtype. The clusters were supported by bootstrap values ranging from 89 to 100%.
SUMMARY After intradermal infection of rabbits with 3 x 106 Treponemapallidum (Melbourne 1 strain) samples of serum were taken at one, two, three, four, and six months after infection.Normal rabbits were passively immunised with these sera, challenged with intradermal doses (104, 103, 102, 10) of T. pallidum, and the latent periods of infection, lesion diameters, and the number of inoculation sites developing into lesions were observed. The sera taken at three, four, and six months reduced the number of intradermal inoculation sites that developed into syphilitic lesions after challenge with 10 T. pallidum. These same three sera also increased the latent period of infection after challenge with 104 T. pallidum. The transfer of 50 ml of immune serum per rabbit over a nine-day period before challenge had very little effect on the course of the challenge infection. Only a low level of immunity in rabbits to this strain of T. pallidum appears to be mediated by immune serum but this small degree of protection did increase with time after infection. Enhanced growth of T. pallidum in the serum-recipient rabbits did not occur, thus suggesting that none of the sera was immunosuppressive.
Normally, only one isolate of Listeria monocytogenes from a case of listeriosis is subjected to characterization. Here we show that two isolates from different sites of the body were not the same strain. Such a phenomenon may not have any clinical relevance, although it may confuse the epidemiologist trying to match infection source with infection target.
Susceptibility to enteric infection with Salmonella was studied in mice housed at different temperatures. The oral doses of S. typhimurium SR-11 and RIA, which caused 50% mortality in animals at 10 C, were about J%0 and M00 of the respective values at 23 C, and that of an avirulent strain of S. enteritidis was also lower in the cold-exposed mice. The frequency of mortality due to Salmonella infection was essentially the same in mice exposed to 34 or 23 C. The divergent responses in the cold and heat probably stem from basic differences in the physiological changes mediated by the two extremes. The pattern and extent of change in weight and rectal temperature were the same among infected mice housed at 10 and 23 C and controls at 10 C, but differed from controls at 23 C. The incidence of Salmonella in samples of liver-spleen, lung, colon, blood, or feces was similar among infected mice housed at 10 and 23 C during a 14-day period of observation. The increased frequency of mortality in cold-exposed infected animals is not due to alterations in invasiveness of the bacteria nor to greater impairment of the thermoregulatory capacity of the mice. It may be attributable, in part at least, to a greater effectiveness of Salmonella toxins as metabolic poisons at low temperatures.
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