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The yeast, Pityrosporum orbiculare, isolated from lesions from lesions of tinea versicolor, grows in vitro only if fatty acids from the C12 to C24 series are added to the culture medium. Except for elaidinic and nervonic acids, all saturated and unsaturated fatty acids tested support growth. P. orbiculare can synthesize various lipid fractions containing both saturated and unsaturated fatty acids from a single fatty acid. Glucose and asparagine stimulate growth but exogenous vitamins do not.

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In this cohort, HCV infection was confirmed to be strongly associated with intravenous drug use. Nonetheless, the occurrence of two thirds of the total HCV seroconversions in non-IDU individuals engaging in at-risk behavior suggests a role of sexual practices in the transmission of the infection. Among non-IDU individuals, the risk for development of HCV infection tended to increase in those who were HIV-1 infected.

A seroprevalence study was carried out on 1757 outpatients consecutively seen in a sexually transmitted disease (STD) clinic in order to evaluate the sexual transmission of hepatitis C virus (HCV). A total of 1442 consenting patients were tested for hepatitis C, hepatitis B and human immunodeficiency virus type 1 (HCV, HBV, HIV-1) antibodies. The relations between anti-HCV, anti-HBc and anti-HIV-1 were studied. Of 73 anti-HCV positive reactions, 45 (61.6%) were confirmed by the recombinant immunoblot assay (RIBA). The proportion of individuals with anti-HCV was higher in outpatients with a history of sexually transmitted disease than without. It was 2.8% in non drug user heterosexuals and 2.9% in non drug user homosexuals. Intravenous drug users (IDU) had higher anti-HCV prevalence when a history of STD was taken into account (42.3% in subjects with STD versus 36.7% in subjects without STD). Among non drug user heterosexuals an association was found between anti-HCV and anti-HBc. These data suggest that sexual transmission of HCV occurs, although it seems to be less efficient than other parenteral modes of transmission. When a more sensitive and specific marker of HCV infection become available, a more accurate estimate of the frequency and efficiency of the sexual transmission will be possible.

The effect of cholesterol and cholesterol esters on Pityrosporum cultures has been studied. A mixture of 0.25% to 2.0% of cholesterol:cholesteryl stearate:glyceryl monostearate (2.0:1.5:2.0) added to Bacto Yeast Morphology Agar plus oleic acid was able to induce hyphae in cultures of both Pityrosporum orbiculare and P. ovale. This result is discussed with respect to the cholesterol effect on cell membranes and to the occurrence of cholesterol and cholesterol esters in the scaling patches of Pityriasis versicolor.

The seroprevalence and risk factors for hepatitis B virus (HBV) infection were determined among 1,497 heterosexuals with no history of intravenous drug use (median age 32, range 15-78) treated at a sexually transmitted disease clinic in Rome. A total of 329 (22.0%) had antibodies to HBV core antigen (anti-HBc), a rate nearly four times as high as the 5.8% found recently in a national sample of young male adults, ages 18-26 years. Multiple logistic regression analysis showed that the risk of anti-HBc positivity was independently associated with male sex, increasing age, lower level of education, three or more sexual partners in the previous year, and positive syphilis serology. Lack of condom use, history of nonulcerative sexually transmitted diseases, and genital herpes were not associated with anti-HBc positivity. These findings confirm that heterosexual exposure plays an important role in the spread of HBV infection. Furthermore, these data indicate that individuals with more than two sexual partners a year and those with positive syphilis serology should be immunised against HBV.