David H. Martin

Trichomonas vaginalis associated with Low birth weight and preterm delivery

Background: Several studies have suggested that pregnant women infected with Trichomonas vaginalis may be at increased risk of an adverse outcome. Goal: To evaluate prospectively the association between T. vaginalis and risk of adverse pregnancy outcome in a large cohort of ethnically diverse women. Study Design: At University‐affiliated hospitals and antepartum clinics in five United States cities, 13,816 women (5,241 black, 4,226 Hispanic, and 4,349 white women) were enrolled at mid‐gestation, tested for T. vaginalis by culture, and followed up until delivery. Results: The prevalence of T. vaginalis infection at enrollment was 12.6%. Race‐specific prevalence rates were 22.8% for black, 6.6% for Hispanic, and 6.1% for white women. After multivariate analysis, vaginal infection with T. vaginalis at mid‐gestation was significantly associated with low birth weight (odds ratio 1.3; 95% confidence interval 1.1 to 1.5), preterm delivery (odds ratio 1.3; 95% confidence interval 1.1 to 1.4), and preterm delivery of a low birth weight infant (odds ratio 1.4; 95% confidence interval 1.1 to 1.6). The attributable risk of T. vaginalis infection associated with low birth weight in blacks was 11% compared with 1.6% in Hispanics and 1.5% in whites. Conclusions: After considering other recognized risk factors including co‐infections, pregnant women infected with T. vaginalis at mid‐gestation were statistically significantly more likely to have a low birth weight infant, to deliver preterm, and to have a preterm low birth weight infant. Compared with whites and Hispanics, T. vaginalis infection accounts for a disproportionately larger share of the low birth weight rate in blacks.

Exploring the Diversity of Gardnerella vaginalis in the Genitourinary Tract Microbiota of Monogamous Couples Through Subtle Nucleotide Variation

Background Bacterial vaginosis (BV) is an enigmatic disease of unknown origin that affects a large percentage of women. The vaginal microbiota of women with BV is associated with serious sequelae, including abnormal pregnancies. The etiology of BV is not fully understood, however, it has been suggested that it is transmissible, and that G. vaginalis may be an etiological agent. Studies using enzymatic assays to define G. vaginalis biotypes, as well as more recent genomic comparisons of G. vaginalis isolates from symptomatic and asymptomatic women, suggest that particular G. vaginalis strains may play a key role in the pathogenesis of BV. Methodology/Principal Findings To explore G. vaginalis diversity, distribution and sexual transmission, we developed a Shannon entropy-based method to analyze low-level sequence variation in 65,710 G. vaginalis 16S rRNA gene segments that were PCR-amplified from vaginal samples of 53 monogamous women and from urethral and penile skin samples of their male partners. We observed a high degree of low-level diversity among G. vaginalis sequences with a total of 46 unique sequence variants (oligotypes), and also found strong correlations of these oligotypes between sexual partners. Even though Gram stain-defined normal and some Gram stain-defined intermediate oligotype profiles clustered together in UniFrac analysis, no single G. vaginalis oligotype was found to be specific to BV or normal vaginal samples. Conclusions This study describes a novel method for investigating G. vaginalis diversity at a low level of taxonomic discrimination. The findings support cultivation-based studies that indicate sexual partners harbor the same strains of G. vaginalis. This study also highlights the fact that a few, reproducible nucleotide variations within the 16S rRNA gene can reveal clinical or epidemiological associations that would be missed by genus-level or species-level categorization of 16S rRNA data.

Head-to-Head Multicenter Comparison of DNA Probe and Nucleic Acid Amplification Tests for Chlamydia trachomatis Infection in Women Performed with an Improved Reference Standard

ABSTRACT Few evaluations of tests for Chlamydia trachomatis have compared nucleic acid amplification tests (NAATs) with diagnostic tests other than those by culture. In a five-city study of 3,551 women, we compared the results of commercial ligase chain reaction (LCR) and PCR tests performed on cervical swabs and urine with the results of PACE 2 tests performed on cervical swabs, using independent reference standards that included both cervical swabs and urethral swab-urine specimens. Using cervical culture as a standard, the sensitivities of PACE 2, LCR, and PCR tests with cervical specimens were 78.1, 96.9, and 89.9%, respectively, and the specificities were 99.3, 97.5, and 98.2%, respectively. Using either cervical swab or urine LCR-positive tests as the standard decreased sensitivities to 60.8% for PACE 2 and to 75.8 and 74.9% for PCR with cervical swabs and urine, respectively. Specificities increased to 99.7% for PACE 2 and to 99.7 and 99.4% for PCR with cervical swabs and urine, respectively. Sensitivities with a cervical swab-urine PCR standard were 61.9% for PACE 2 and 85.5 and 80.8% for LCR with cervical swabs and urine, respectively. Specificities were 99.6% for PACE 2 and 99.0 and 98.9% for LCR with cervical swabs and urine, respectively. Cervical swab versus urine differences were significant only for PCR specificities (P = 0.034). Overall, LCR sensitivity exceeded that of PCR, and sensitivities obtained with cervical swabs exceeded those obtained with urine specimens by small amounts. These data have substantiated, using a large multicenter sample and a patient standard, that LCR and PCR tests performed on endocervical swabs and urine are superior to PACE 2 tests for screening C. trachomatis infections in women. In our study, NAATs improved the detection of infected women by 17 to 38% compared to PACE 2.

The Microbiota of the Vagina and Its Influence on Women’s Health and Disease

Abstract:Explorations of the vaginal microbiota (VMB) began over 150 years ago. Using light microscopy and bacterial cultures, the concept of normal versus abnormal microbiota in women began to emerge. The latter became known by the term “bacterial vaginosis” (BV). BV microbiota is dominated by Gardnerella vaginalis and includes a number of anaerobic organisms. In contrast, normal flora is dominated by various Lactobacilli. BV microbiota is associated with vaginal discharge, poor pregnancy outcomes, pelvic inflammatory disease, postoperative wound infections and endometritis after elective abortions. In addition, BV flora predisposes women to infection by human immunodeficiency virus and sexually transmitted diseases. Application of molecular techniques over the past decade has significantly advanced our understanding of the VMB. It is far more complex than previously recognized and is composed of many previously unknown organisms in addition to those already identified by culture. Analyses using high-throughput sequencing techniques have revealed unique microbial communities not previously recognized within the older, established vaginal flora categories. These new findings will inform the design of future clinical investigations of the role of the VMB in health and disease.

Anal intercourse among young heterosexuals in three sexually transmitted disease clinics in the United States.

Objective: To examine factors associated with heterosexual anal intercourse (AI). Methods: Between 2001 and 2004, 1084 heterosexual adults aged 18 to 26 attending public sexually transmitted disease clinics in Seattle, New Orleans, and St Louis were interviewed using computer-assisted self interview and tested for STIs; Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium, Trichomonas vaginalis, and genital herpes (HSV-2). Characteristics associated with AI were identified using logistic regression. Results: Overall 400 (37%) reported ever having had AI, 266 (28.9%) reported AI with at least 1 of their last 3 partners, and 19% reported AI with their last partner. Fewer women than men reported condom use at last AI (26% vs. 45%, P <0.001). Ever having AI was associated with sex on the same day as meeting a partner [AOR 3.9 (95% CI, 2.46–6.21)], receiving money for sex [AOR 2.8 (1.40–5.45)], and >3 lifetime sex partners [AOR 2.8 (1.56–5.07)] among women, and sex on the same day as meeting a partner [AOR 2.0 (1.33–3.06]) among men. AI with the last partner was associated with sex toy use [AOR 5.6 (2.63–12.0)] and having concurrent partners [AOR 2.2 (1.21–4.11)] among men, and with sex within a week of meeting [AOR 2.4 (1.28–4.37)], believing the partner was concurrent (AOR 1.9 [1.12–3.22]), and sex toy use [AOR 5.7 (2.31–14.0)] among women. Prevalent vaginal and urethral sexually transmitted infections were not associated with AI. Conclusions: Many young heterosexuals attending sexually transmitted disease clinics reported AI, which was associated with other sexual risk behaviors, suggesting a confluence of risks for HIV infection.

Use of Multiple Nucleic Acid Amplification Tests To Define the Infected-Patient “Gold Standard” in Clinical Trials of New Diagnostic Tests for Chlamydia trachomatis Infections

ABSTRACT Nucleic acid amplification tests (NAATs) can be used to define the infected-patient “gold standard” for the purpose of designing studies of the performance of Chlamydia trachomatis diagnostic tests. It is unclear how many test results run by different NAATs and what combinations of specimens comprise the best infected-patient gold standard. We approached this question with data from a large study of the performance of a new NAAT. Data were available from three endocervical swabs and a urine specimen collected from each of 1,412 women and tested by three different NAATs. Results from all three assays were used equally in a rotating fashion to define the infected-patient gold standard. Multiple different infected-patient gold standards for estimating swab and urine specimen sensitivity and specificity for one NAAT method were created by varying the number and combinations of swab and urine comparator results with two different NAATs, The effect of changing the infected-patient gold standard definition was determined by constructing receiver-operator-like curves with calculated sensitivities and specificities for each test. The one-positive-of-two-results or two-positive-of-two-results (same or two different assays) infected-patient gold standard definitions produced low sensitivity and low specificity estimates, respectively. If four comparator NAAT results were used, the any-three-positive-of-four-results definition or the at-least-one-specimen-positive-by-each-of-two-comparator-assays definition appeared to provide better combinations of sensitivity and specificity estimates. The any-two-positive-out-of-three-results definition resulted in estimates that were as good as produced with the former two definitions. This analytic approach provides a means of clearly visualizing the effects of changing NAAT-based infected-patient gold standards and should be helpful in designing future studies of new C. trachomatis diagnostic tests.

Management of Women with Cervicitis

In the past several years, the collective understanding of cervicitis has extended beyond the recognition of Chlamydia trachomatis and Neisseria gonorrhoeae as the prime etiologic suspects. Trichomonas vaginalis and herpes simplex virus cause cervicitis, and both Mycoplasma genitalium and bacterial vaginosis have emerged as new candidate etiologic agents or conditions. However, major gaps in our knowledge of this common condition remain. Putative etiologic agents have not been identified in many women with cervicitis. Moreover, cervicitis occurs in a relatively small proportion of women with chlamydia or gonorrhea. Finally, scant research has addressed the clinical response of nonchlamydial and nongonococcal cervicitis to antibiotic therapy, and there are no data on the benefit of sex partner treatment for such women. New research into the etiology, immunology, and natural history of this common condition is needed, especially in view of the well-established links between cervicitis and an increased risk of upper genital tract infection and human immunodeficiency virus type 1 acquisition.

An engineered R-type pyocin is a highly specific and sensitive bactericidal agent for the food-borne pathogen Escherichia coli O157:H7.

ABSTRACT Some strains of Pseudomonas aeruginosa produce R-type pyocins, which are high-molecular-weight phage tail-like protein complexes that have bactericidal activity against other Pseudomonas strains. These particles recognize and bind to bacterial surface structures via tail fibers, their primary spectrum determinant. R-type pyocins kill the cell by contracting a sheath-like structure and inserting their hollow core through the cell envelope, resulting in dissipation of the cellular membrane potential. We have retargeted an R-type pyocin to Escherichia coli O157:H7 by fusing a tail spike protein from an O157-specific phage, φV10, to the pyocin tail fiber. The φV10 tail spike protein recognizes and degrades the O157 lipopolysaccharide. This engineered pyocin, termed AVR2-V10, is sensitive and specific, killing 100% of diverse E. coli O157:H7 isolates but no other serotypes tested. AVR2-V10 can kill E. coli O157:H7 on beef surfaces, making it a candidate agent for the elimination of this pathogen from food products. All rare AVR2-V10-resistant mutants isolated and examined have lost the ability to produce the O157 antigen and are expected to have compromised virulence. In addition, E. coli O157:H7 exposed to and killed by AVR2-V10 do not release Shiga toxin, as is often the case with many antibiotics, suggesting potential therapeutic applications. The demonstration that a novel R-type pyocin can be created in the laboratory by fusing a catalytic tail spike from the family Podoviridae to a tail fiber of a member of the family Myoviridae is evidence that the plasticity observed among bacteriophage tail genes can, with modern molecular techniques, be exploited to produce nonnatural, targeted antimicrobial agents.

Early repeated infections with Trichomonas vaginalis among HIV-positive and HIV-negative women.

BACKGROUNDnThe purpose of the study was to examine whether early repeated infections due to Trichomonas vaginalis among human immunuodeficiency virus (HIV)-positive and HIV-negative women are reinfections, new infections, or cases of treatment failure.nnnMETHODSnWomen attending an HIV outpatient clinic and a family planning clinic in New Orleans, Louisiana, who had culture results positive for T. vaginalis were treated with 2 g of metronidazole under directly observed therapy. At 1 month, detailed sexual exposure and sexual partner treatment information was collected. Isolates from women who had clinical resistance (i.e., who tested positive for a third time after treatment at a higher dose) were tested for metronidazole susceptibility in vitro.nnnRESULTSnOf 60 HIV-positive women with trichomoniasis, 11 (18.3%) were T. vaginalis positive 1 month after treatment. The 11 recurrences were classified as 3 probable reinfections (27%), 2 probable infections from a new sexual partner (18%), and 6 probable treatment failures (55%); 2 of the 6 patients who experienced probable treatment failure had isolates with mild resistance to metronidazole. Of 301 HIV-negative women, 24 (8.0%) were T. vaginalis positive 1 month after treatment. The 24 recurrences were classified as 2 probable reinfections (8%) and 22 probable treatment failures (92%); of the 22 patients who experienced probable treatment failure, 2 had strains with moderate resistance to metronidazole, and 1 had a strain with mild resistance to metronidazole.nnnCONCLUSIONnHIV-positive women were more likely to have sexual re-exposure than were HIV-negative women, although the rate of treatment failure was similar in both groups. High rates of treatment failure among both HIV-positive and HIV-negative women indicate that a 2-g dose of metronidazole may not be adequate for treatment of some women and that rescreening should be considered.

Mycoplasma genitalium: an efficient strategy to generate genetic variation from a minimal genome

Mycoplasma genitalium, a human pathogen associated with sexually transmitted diseases, is unique in that it has smallest genome of any known free‐living organism. The goal of this study was to investigate if and how M.u2003genitalium uses a minimal genome to generate genetic variations. We analysed the sequence variability of the third gene (MG192 or mgpC) of the M.u2003genitalium MgPa adhesion operon, demonstrated that the MG192 gene is highly variable among and within M.u2003genitalium strains in vitro and in vivo, and identified MG192 sequence shifts in the course of in vitro passage of the G37 type strain and in sequential specimens from an M.u2003genitalium‐infected patient. In order to establish the origin of the MG192 variants, we examined nine genomic loci containing partial copies of the MgPa operon, known as MgPar sequences. Our analysis suggests that the MG192 sequence variation is achieved by recombination between the MG192 expression site and MgPar sequences via gene cross‐over and, possibly, also by gene conversion. It appears plausible that M.u2003genitalium has the ability to generate unlimited variants from its minimized genome, which presumably allows the organism to adapt to diverse environments and/or to evade host defences by antigenic variation.