Bioinformatic evidence of widespread priming in type I and II CRISPR-Cas systems.

CRISPR-Cas systems provide bacteria and archaea with adaptive immunity against invading genetic elements, such as plasmids, bacteriophages and archaeal viruses. They consist of cas genes and CRISPR loci, which store genetic memories of previously encountered invaders as short sequences termed spacers. Spacers determine the specificity of CRISPR-Cas defence and immunity can be gained or updated by the addition of new spacers into CRISPR loci. There are two main routes to spacer acquisition, which are known as naïve and primed CRISPR adaptation. Naïve CRISPR adaptation involves the de novo formation of immunity, independent of pre-existing spacers. In contrast, primed CRISPR adaptation (priming) uses existing spacers to enhance the acquisition of new spacers. Priming typically results in spacer acquisition from locations near the site of target recognition by the existing (priming) spacer. Primed CRISPR adaptation has been observed in several type I CRISPR-Cas systems and it is potentially widespread. However, experimental evidence is unavailable for some subtypes, and for most systems, priming has only been shown in a small number of hosts. There is also no current evidence of priming by other CRISPR-Cas types. Here, we used a bioinformatic approach to search for evidence of priming in diverse CRISPR-Cas systems. By analysing the clustering of spacers acquired from phages, prophages and archaeal viruses, including strand and directional biases between subsequently acquired spacers, we demonstrate that two patterns of primed CRISPR adaptation dominate in type I systems. In addition, we find evidence of a priming-like pathway in type II CRISPR-Cas systems.

HIV/STI associated risk behaviors among self-identified lesbian, gay, bisexual, and transgender college students in the United States.

An Internet survey was conducted during the 2001-2002 academic year to examine the health risk behaviors, including HIV/STI associated behaviors, of self-identified lesbian, gay, bisexual, and transgender (LGBT) college students in the United States. A total of 450 LGBT college students completed the entire online survey. Most respondents attended a 4-year (96.9%), coeducational (98.6%), non-religiously affiliated (87.5%), public (68.6%) institution. Eighty-nine percent reported having sex with someone of the same sex and 45% had multiple (6 or more) sex partners during their lifetime. Most reported using a condom consistently during penile-vaginal (61%) and anal sex (63%). However, only 4% used a condom or other barrier consistently during oral sex and 28% used a condom or other barrier during their last sexual encounter. Injection drug use and needle-sharing behavior was low (2.1% and 1.1%, respectively). Comparisons with heterosexual college students' HIV/STI associated risk behaviors are included. Results may be useful for HIV/STI prevention programs targeting LGBT college students.

Sexual behaviors and sexually transmitted infections among self-identified lesbian and bisexual college women.

Sexually transmitted infections (STIs) are a significant health issue for lesbian and bisexual women. Older age and having a history of sexual intercourse with males are primary risk factors for STIs among this population. However, little research has been conducted to assess sexual risk among lesbian and bisexual college women exclusively. A cross-sectional Internet survey was conducted with 230 self-identified lesbian and bisexual female college students to examine their sexual risk and to determine with which, if any, STIs they had ever been diagnosed. Eight percent of lesbian and bisexual college women reported ever being diagnosed with an STI; the human papillomavirus, bacterial vaginosis, and genital herpes accounted for 84% of STI cases. Number of lifetime sex partners was significantly associated with an STI diagnosis among this population. Older age, engaging in penile-vaginal intercourse with a male (lifetime), and younger age at first same-sex experience were significantly associated with a greater number of lifetime sex partners. Results may be useful to sexual health programs targeting lesbian and bisexual college women and/or their providers.

Efficacy of topical metronidazole (10 percent) in the treatment of anorectal Crohn's disease.

PURPOSE: The aim of this study was to investigate the efficacy of 10 percent topical metronidazole in the treatment of symptomatic anorectal Crohn's disease. METHODS: Patients with symptomatic anorectal Crohn's disease were studied in a prospective, nonblinded, nonrandomized study to evaluate the efficacy of topical 10 percent metronidazole. Perianal Crohn's Disease Activity Index and each component (pain, discharge, induration, sexual dysfunction, and type of pathology) were recorded before treatment and at four weeks. Visual analog pain score (0-10) was recorded before treatment and at weekly intervals for up to four weeks. RESULTS: Fourteen patients were studied prospectively for four weeks. Mean Perianal Crohn's Disease Activity Index decreased from 8.8 +/- 0.9 before treatment to 4.1 +/- 0.7 after four weeks' treatment (P < 0.0001). Visual analog pain scores decreased from 5.4 +/- 0.7 before treatment to 2.4 +/- 0.5 at one week (P < 0.001) and to 1.0 +/- 0.4 after four weeks' treatment (P < 0.0001). Of the Perianal Crohn's Disease Activity Index components, significant decreases were noted in pain and discharge (P < 0.0001) and induration (P < 0.001). CONCLUSION: For patients with perianal Crohn's disease, topical 10 percent metronidazole decreases the Perianal Crohn's Disease Activity Index and anorectal pain.

Topical metronidazole (10 percent) decreases posthemorrhoidectomy pain and improves healing.

INTRODUCTION: Oral metronidazole has been previously demonstrated to decrease postoperative pain after open diathermy hemorrhoidectomy. The current study investigates the efficacy of topical metronidazole (10 percent) in reducing postoperative pain and promoting wound healing after Harmonic Scalpel hemorrhoidectomy. METHODS: A prospective, randomized trial was conducted to compare posthemorrhoidectomy pain and wound healing with use of topical metronidazole (10 percent) vs. placebo carrier, applied to the surgical site. Surgical indications included grade 3 or 4 internal or external hemorrhoidal disease, with or without a fissure-in-ano. Pain was assessed using a visual analog score (VAS) preoperatively and on postoperative days 1, 2, 7, 14, and 28. Twenty-four-hour narcotic use (hydrocodone 10 mg) was recorded on postoperative days 1, 2, 7, 14, and 28. Digital photographs of the surgical site were taken at 14 days postoperatively. The photographs were independently ranked by three blinded observers according to a) postoperative edema, b) primary vs. secondary healing, and c) overall wound healing. RESULTS: Twenty patients were randomized in a prospective manner, ten to the topical 10 percent metronidazole group and ten to the placebo carrier group. Patients in the topical metronidazole group experienced significantly less postoperative pain at day 7 (VAS +/- SEM, 3.4 +/- 0.4 vs. 6.3 +/- 0.5; P = 0.002) and day 14 (1.0 +/- 0.4 vs. 3.2 +/- 0.7, P = 0.02). There was no statistical difference in narcotic analgesic requirements between groups. In the metronidazole group, postoperative edema was ranked significantly lower (mean score, 3.0 vs. 7.0, P < 0.01) and overall wound healing ranked significantly better (4.0 vs. 7.0, P = 0.03) than in controls. CONCLUSION: Topical 10 percent metronidazole significantly reduces posthemorrhoidectomy discomfort at days 7 and 14 postoperatively. Postoperative edema is reduced and overall healing is improved, compared with that of carrier controls.