Herpes simplex virus type 2 seroprevalence and incidence in acute and chronic HIV-1 infection

Herpes simplex virus type 2 (HSV-2) HIV co-infection is common and associated with increased risk of HIV transmission. HSV-2 seroprevalence was assessed on stored samples from baseline and one year follow-up from 81 patients identified with acute HIV infection and 81 age-matched chronically infected men. HSV-2 seroprevalence at baseline was lower for those with acute rather than chronic HIV-infection, 51.9 versus 71.6% (P = 0.01); relative risk 0.72 (95% confidence interval [CI] 0.57-0.92). Since HSV-2 seroprevalence is lower in those newly HIV-infected, the diagnosis of early HIV infection may allow for counselling to reduce subsequent HSV-2 acquisition.

Seminal plasma HIV levels in men with asymptomatic sexually transmitted infections

The effect of asymptomatic sexually transmitted urethral infections on human immunodeficiency virus (HIV) RNA viral load in semen is poorly defined. We studied five such patients. Those on antiretrovirals (n = 2) had lower seminal plasma viral loads (SPVL) (2.11 and 1.98 log(10) copies/mL) than those not on antiretrovirals (n = 3) (2.27-3.78 log(10) copies/mL). One patient who was not taking antiretrovirals had a 94% decline in SPVL after treatment of asymptomatic Chlamydia trachomatis urethritis, suggesting that asymptomatic infection may be a co-factor for HIV transmission.

Body site colonization in patients with community-associated methicillin-resistant Staphylococcus aureus and other types of S. aureus skin infections

Efforts to control spread of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) are often based on eradication of colonization. However, the role of nasal and non-nasal colonization in the pathogenesis of these infections remains poorly understood. Patients with acute S. aureus skin and soft tissue infection (SSTI) were prospectively enrolled. Each subject's nasal, axillary, inguinal and rectal areas were swabbed for S. aureus and epidemiological risk factors were surveyed. Among the 117 patients enrolled, there were 99 patients who had an SSTI and for whom data could be analysed. Sixty-five patients had a CA-MRSA SSTI. Among these patients, MRSA colonization in the nares, axilla, inguinal area and rectum was 25, 6, 11 and 13%, respectively, and 37% overall were MRSA colonized. Most (96%) MRSA colonization was detected using nose and inguinal screening alone. Non-nasal colonization was 25% among CA-MRSA patients, but only 6% among patients with CA-methicillin-susceptible S. aureus (MSSA) or healthcare-associated MRSA or MSSA. These findings suggest that colonization patterns in CA-MRSA infection are distinct from those in non-CA-MRSA S. aureus infections. The relatively high prevalence of non-nasal colonization may play a key role in CA-MRSA transmission and acquisition of infection.

Unanticipated heterogeneity in growth rate and virulence among Candida albicans AAF1 null mutants

The disruption of a specific gene in Candida albicans is commonly used to determine the function of the gene product. We disrupted AAF1, a gene of C. albicans that causes Saccharomyces cerevisiae to flocculate and adhere to endothelial cells. We then characterized multiple heterozygous and homozygous mutants. These null mutants adhered to endothelial cells to the same extent as did the parent organism. However, mutants with presumably the same genotype revealed significant heterogeneity in their growth rates in vitro. This heterogeneity was not the result of the transformation procedure per se, nor was it caused by differences in the expression or function of URA3, a marker used in the process of gene disruption. The growth rate among the different heterozygous and homozygous null mutants was positively correlated with in vivo virulence in mice. It is possible that the variable phenotypes of C. albicans were due to mutations outside of the AAF1 coding region that were introduced during the gene disruption process. These results indicate that careful phenotypic characterization of mutants of C. albicans generated through targeted gene disruption should be performed to exclude the introduction of unexpected mutations that may influence pathogenicity in mice.

Expression of the Candida albicans gene ALS1 in Saccharomyces cerevisiae induces adherence to endothelial and epithelial cells

To identify genes encoding adhesins that mediate the binding of Candida albicans to endothelial cells, a genomic library from this organism was constructed and used to transform Saccharomyces cerevisiae. These transformed organisms were screened for adherence to endothelial cells, and a highly adherent clone was identified. The adherence of this clone to endothelial cells was over 100-fold greater than that of control S. cerevisiae transformed with the empty plasmid. This clone also exhibited enhanced adherence to epithelial cells. The C. albicans gene contained within this clone was found to be ALS1. These results indicate that ALS1 may encode a candidal adhesin.