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Sexually transmitted diseases (STDs)--a synoptic overview for urologists.

The classical bacteria that cause venereal diseases, e.g. gonorrhea, syphilis, chancroid and inguinal granuloma only account for a small proportion of all known STDs today. Other bacteria and viruses as well as yeasts, protozoa and epizoa must also be regarded as causative organisms of STD. Taken together, all sexually transmitted infections (STI) comprise more than 30 relevant STD pathogens. However, not all pathogens that can be sexually transmitted manifest diseases in the genitals and not all infections of the genitals are exclusively sexually transmitted. Concise information and tables summarising the diagnostic and therapeutic management of STDs in the field of Urology allow a synoptic overview and are in agreement with recent international guidelines of other specialties. Special considerations (i.e. HIV infection, pregnancy, infants, allergy) and recommended regimens may be looked up here.

Bacterial Infections↗

The sodA gene of Haemophilus ducreyi encodes a hydrogen peroxide-inhibitable superoxide dismutase.

Haemophilus ducreyi is the etiologic agent of the sexually transmitted disease chancroid, an ulcerative condition implicated in increased HIV transmission. There is increasing evidence for the roles of oxidative stress proteins including superoxide dismutase enzymes in the survival and persistence of pathogenic organisms within the host. The sodA gene of Haemophilus ducreyi was isolated from a genomic plasmid library on the basis of its ability to rescue the hydrogen peroxide hypersensitivity of an Escherichia coli sodA sodB strain. The H. ducreyi SodA protein also complemented the aerobic growth defect of the E. coli sodA sodB strain in minimal medium. The deduced amino-acid sequence of the H. ducreyi sodA gene product is 74 and 70% identical to the Mn-SODs of Haemophilus influenzae and E. coli, respectively. However, unlike Mn-SODs, the H ducreyi SodA protein was inhibited by hydrogen peroxide in native gels stained for SOD activity.

Amino Acid Sequence↗

The dnaK/dnaJ operon of Haemophilus ducreyi contains a unique combination of regulatory elements.

Haemophilus ducreyi, which causes the genital ulcer disease chancroid, requires high basal levels of the 60-kDa heat-shock (hs) protein GroEL in order to survive and adhere to host cells in the presence of common environmental stresses. In contrast, the 70-kDa hs protein, DnaK, a negative modulator of the hs response in prokaryotes, is not produced at as high a level as GroEL. Because of these differences, we were interested in identifying regulatory elements affecting the expression of the H. ducreyi dnaK/dnaJ operon. First, the genes encoding H. ducreyi DnaK (Hsp70) and DnaJ (Hsp40) were sequenced. The deduced amino acid sequences shared 82.8 and 63. 9% identity with the Escherichia coli DnaK and DnaJ homologs, respectively. Despite the presence of highly similar (but not identical) hs promoter sequences preceding both the H. ducreyi groES/groEL and dnaK/dnaJ operons, transcription levels for groEL were found to exceed that of dnaK. Subsequently, other genetic elements that could contribute to a lower basal expression of dnaK in H. ducreyi were identified. These elements include: (1) a complex promoter for dnaK consisting of four transcriptional start points (two for sigma32 and two for sigma70) identified by primer extension; (2) a putative binding site for Fur (a transcriptional repressor of iron-regulated genes) that overlaps the initiating AUG of dnaK; and (3) the potential for extensive secondary structure of the long leader sequences of the dnaK transcripts, which could interfere with efficient translation of DnaK. This unique combination of regulatory elements may be responsible for the relatively low-level expression of dnaK in this fastidious genital pathogen.

Amino Acid Sequence↗

The situation in Africa.

More than three million women world-wide are infected with HIV, and women will constitute 40% of the new AIDS cases in 1990-1991. Unlike in the industrialized world, HIV in Africa is heterosexually transmitted and thus affects at least as many women as men. Already the leading cause of death in a major African city, HIV may be spreading to rural areas. In spite of improvement in surveillance, under-reporting makes it difficult to project trends, document differences within and between urban and rural areas, and identify at-risk groups. Increasing evidence shows that STDs play a major role in spreading the HIV epidemic. Male-to-female transmission is more efficient owing to factors related to the pathogen and the host. Ulcerative STDs such as chancroid, syphilis and herpes facilitate HIV entry through mucosal discontinuation and recruitment of HIV target cells. The role of non-ulcerative STDs such as gonorrhoeal, chlamydial and trichomonal infections needs further elucidation. Lack of circumcision, traditional healing practices and oral contraceptives may affect the risk of viral transmission, but may not be major or modifiable risk factors. Pregnancy and pregnancy-associated immune alterations do not seem to affect the clinical course of HIV/AIDS in African women or impair immunocompetence. Maternal HIV can adversely affect pregnancy outcome in Africa, causing low birth-weight, prematurity, intrauterine and intrapartum fetal death. The risk for these outcomes is likely to depend on the degree of immunological and clinical deterioration. Breast-feeding does not appreciably increase the risk of HIV transmission to the infant and should be actively promoted in Africa. Control of HIV/AIDS in Africa, in the absence of an effective vaccine, will focus on behavioural changes through health education and condom use. High frequency STD transmitter core groups, mainly prostitutes and their clients, are currently the target of prevention campaigns which are proving to be successful and affordable.

Africa↗

Non-radioactive ribotyping of Haemophilus ducreyi using a digoxigenin labelled cDNA probe.

Haemophilus ducreyi, the causal organism of chancroid, has increased in significance recently due to its association with HIV transmission. Most previous typing systems have exploited phenotypic characteristics. Detection of ribosomal RNA cistrons, ribotyping, was successfully developed to examine H. ducreyi, but required the use of 32P. We have used digoxigenin to define ribotypes from 30 strains of H. ducreyi from diverse geographical locations. This was achieved by agarose gel electrophoresis of restriction enzyme (RE) digested DNA extracts. These extracts were vacublotted onto nylon membrane and probed using digoxigenin labelled complementary DNA probe, prepared from Escherichia coli 16S and 23S ribosomal RNA. From 19 REs tested, Ava II, Hinc II, Bgl II and BstE II gave clear ribotypes. The ribotypes of BstE II and Bgl II used together gave the highest index of discrimination (D = 0.95), 16 types, and showed good reproducibility. This non-radioactive method demonstrates the three important features of a typing system; discrimination, typability and reproducibility.

Bacterial Typing Techniques↗

Structure of the major oligosaccharide from the lipooligosaccharide of Haemophilus ducreyi strain 35000 and evidence for additional glycoforms.

Haemophilus ducreyi is a sexually transmitted pathogen that colonizes the genital epithelium in humans, causing genital ulcers or chancroid. Its surface lipooligosaccharides (LOSs) have been shown to play a role in ulcer formation and may also be important in cell adhesion and invasion of host tissue. Earlier we presented a preliminary structure of the major LOS from strain 35000 that suggested the presence of terminal lactosamine [Melaugh, W., Phillips, N.J., Campagnari, A.A., Karalus, R., & Gibson, B. W. (1992) J. Biol. Chem. 267, 13434-13439]. We have now confirmed this structure and assigned the anomeric linkages by 2D NMR studies. In addition to this major structure, analysis by electrospray ionization mass spectrometry of both O-deacylated LOSs and the oligosaccharides released after treatment with mild acid indicates the presence of several other LOS glycoforms. These glycoforms constitute a series of both truncated and elongated analogs of the major oligosaccharide determined by NMR. One of these glycoforms exists as a smaller oligosaccharide corresponding to the major structure minus terminal galactose. Three other glycoforms appear as larger molecular weight species formed by the addition of phosphoethanolamine, N-acetylhexosamine, and N-acetylhexosamine plus hexose. Two sialylated glycoforms were also identified and subsequently confirmed by treatment with neuraminidase, but these glycoforms were not found in the released oligosaccharide pool due to the acid lability of of sialic acid. This study clearly indicates that the LOSs from H. ducreyi strain 35000 exist as a heterogeneous population whose structures differ primarily in their phosphorylation states and terminal sugars and whose terminal glycan structures can resemble those of human antigens.

Acylation↗

Biosynthesis of sialylated lipooligosaccharides in Haemophilus ducreyi is dependent on exogenous sialic acid and not mannosamine. Incorporation studies using N-acylmannosamine analogues, N-glycolylneuraminic acid, and 13C-labeled N-acetylneuraminic acid.

Haemophilus ducreyi is a Gram-negative bacterium that causes chancroid, a sexually transmitted disease. Cell surface lipooligosaccharides (LOS) of H. ducreyi are thought to play important biological roles in host infection. The vast majority of H. ducreyi strains contain high levels of sialic acid (N-acetylneuraminic acid, NeuAc) in their LOS. Here we investigate the biosynthetic origin of H. ducreyi sialosides by metabolic incorporation studies using a panel of N-acylmannosamine and sialic acid analogues. Incorporation of sialosides into LOS was assessed by matrix-assisted laser desorption and electrospray ionization mass spectrometry. A Fourier transform ion cyclotron resonance mass spectrometer provided accurate mass measurements, and a quadrupole time-of-flight instrument was used to obtain characteristic fragment ions and partial carbohydrate sequences. Exogenously supplied N-acetylmannosamine analogues were not converted to LOS-associated sialosides at a detectable level. In contrast, exogenous (13)C-labeled N-acetylneuraminic acid ([(13)C]NeuAc) and N-glycolylneuraminic acid (NeuGc) were efficiently incorporated into LOS in a dose-dependent fashion. Moreover, approximately 1.3 microM total exogenous sialic acid was sufficient to obtain about 50% of the maximum production of sialic acid-containing glycoforms observed under in vitro growth conditions. Together, these data suggest that the expressed levels of sialylated LOS glycoforms observed in H. ducreyi are in large part controlled by the exogenous concentrations of sialic acid and at levels one might expect in vivo. Moreover, these studies show that to properly exploit the sialic acid biosynthetic pathway for metabolic oligosaccharide engineering in H. ducreyi and possibly other prokaryotes that share similar pathways, precursors based on sialic acid and not mannosamine must be used.

Biological Transport↗

Investigation of the kinetic mechanism of cytidine 5'-monophosphate N-acetylneuraminic acid synthetase from Haemophilus ducreyi with new insights on rate-limiting steps from product inhibition analysis.

The presence of sialic acid as a component of cell surface lipooligosaccharides or capsular polysaccharides has been shown to be correlated with the virulence of a number of Gram-negative mucosal pathogens, including several Haemophilus and Neisseria spp. As part of our efforts to evaluate the role of sialic acid in the pathobiology of these organisms, we have initiated studies of the enzymes from Haemophilus ducreyi (the infectious agent of chancroid) responsible for the activation and attachment of sialic acid to the lipooligosaccharide. In this report, we describe results of an investigation of the steady-state kinetic mechanism of the activating enzyme, cytidine 5'-monophosphate N-acetylneuraminic acid (CMP-NeuAc) synthetase. Using a combination of initial velocity, product inhibition, and dead-end inhibition studies, the reaction is shown to be freely reversible and to proceed through an ordered bi-bi kinetic mechanism in which CTP binds first and CMP-NeuAc dissociates last. In addition, a detailed analysis of the kinetic expressions for the observable constants is presented showing how the variation in apparent product inhibition constants (Kii) can be used to predict the rate-limiting step in kcat, which appears to be dissociation of CMP-NeuAc in this enzyme. To our knowledge, this relationship has not been previously recognized.

Binding, Competitive↗

Periplasmic copper-zinc superoxide dismutase protects Haemophilus ducreyi from exogenous superoxide.

Haemophilus ducreyi causes chancroid, a sexually transmitted genital ulcer disease implicated in increased heterosexual transmission of HIV. As part of an effort to identify H. ducreyi gene products involved in virulence and pathogenesis, we created random TnphoA insertion mutations in an H. ducreyi 35000 library cloned in Escherichia coli. Inserts encoding exported or secreted PhoA fusion proteins were characterized by DNA sequencing. One such clone encoded a Cu-Zn superoxide dismutase (SOD) enzyme. The Cu-Zn SOD was periplasmic in H. ducreyi and accounted for most of the detectable SOD activity in whole-cell lysates of H. ducreyi grown in vitro. To investigate the function of the Cu-Zn SOD, we created a Cu-Zn SOD-deficient H. ducreyi strain by inserting a cat cassette into the sodC gene. The wild-type and Cu-Zn SOD null mutant strains were equally resistant to excess cytoplasmic superoxide induced by paraquat, demonstrating that the Cu-Zn SOD did not function in the detoxification of cytoplasmic superoxide. However, the Cu-Zn SOD null strain was significantly more susceptible to killing by extracellular superoxide than the wild type. This result suggests that the H. ducreyi Cu-Zn SOD may play a role in bacterial defence against oxidative killing by host immune cells during infection.

Alkaline Phosphatase↗

Case report. Paraphimosis due to erotic dancing.

Paraphimosis usually develops when a tight foreskin is retracted over the glans penis for a prolonged period. Many esoteric aetiologies have been implicated in the development of paraphimosis including piercing the foreskin, Plasmodium falciparum infection, application of celadine juice to the foreskin, chancroid, pessaries and the implantation of pearls. We report the first two cases of paraphimosis developing during wining, an erotic dance native to Trinidad & Tobago.

Adolescent↗

Functional studies of the recombinant subunits of a cytolethal distending holotoxin.

Cytolethal distending toxin (CDT) is a multicomponent bacterial holotoxin that targets most eukarytotic cells causing distension and cell cycle arrest. A number of diverse pathogenic bacterial species associated with diarrhoea, chancroid, chronic hepatitis and periodontal disease produce a CDT. Synthesis of the holotoxin is directed by the expression of three genes, cdtA, cdtB and cdtC. Although the product of the CdtB gene was previously identified as a type I deoxyribonuclease, the functions of the cdtA and cdtC products have not been characterized. Using the periodontal pathogen, Actinobacillus actinomycetemcomitans, we demonstrate that the recombinant product of the CdtA gene binds to the surface of Chinese hamster ovary (CHO) cells. This protein did not induce distension or cytotoxicity when introduced into the cytosol using a lipid-based protein delivery system. Recombinant CdtB and CdtC proteins failed to bind to CHO cells. However, the delivery of either CdtB or CdtC into the cytosol resulted in the characteristic pattern of distension followed by cell death. Based on these results, it appears that the CdtA protein subunit alone is responsible for anchoring the holotoxin to the cell surface. The CdtC subunit, in concert with CdtB, contributes to the cytotoxic activities of the holotoxin. The specific mechanism of CdtC cytotoxicity is currently unknown.

Animals↗

Improving the National Board of Medical Examiners internal Medicine Subject Exam for use in clerkship evaluation.

OBJECTIVE: To provide a consensus opinion on modifying the National Board of Medical Examiners (NBME) Medicine Subject Exam (Shelf) to: 1) reflect the internal medicine clerkship curriculum, developed by the Society of General Internal Medicine (SGIM) and the Clerkship Directors in Internal Medicine (CDIM); 2) emphasize knowledge important for a clerkship student; and 3) obtain feedback about students' performances on the Shelf. DESIGN: Two-round Delphi technique. PARTICIPANTS: The CDIM Research and Evaluation Committee and CDIM members on NBME Step 2 Committees. MEASUREMENTS: Using 1-5 Likert scales (5 = highest ratings), the group rated test question content for relevance to the SGIM-CDIM Curriculum Guide and importance for clerkship students' knowledge. The Shelf content is organized into 4 physician tasks and into 11 sections that are generally organ system based. Each iteration of the Shelf has 100 questions. Participants indicated a desired distribution of questions by physician task and section, topics critical for inclusion on each exam, and new topics to include. They specified the types of feedback clerkship directors desired on students' performances. Following the first round, participants viewed pooled results prior to submitting their second-round responses. RESULTS: Of 15 individuals contacted, 12 (80%) participated in each round. The desired distribution by physician task was: diagnosis (43), treatment (23), mechanism of disease (20), and health maintenance (15). The sections with the most questions requested were the cardiovascular (17), respiratory (15), and gastroenterology (12) sections. The fewest were requested in aging/ethics (4) and neurology, dermatology, and immunology (5 each). Examples of low-rated content were Wilson's Disease, chancroid and tracheal rupture (all <2.0). Health maintenance in type 2 diabetes, hypertension, and cardiovascular disease all received 5.0 ratings. Participants desired feedback by: section (4.6) and physician task (3.9), on performances of the entire class (4.0), and for individual students (3.8). CONCLUSION: Clerkship directors identified test content that was relevant to the curricular content and important for clerkship students to know, and they indicated a desired question distribution. They would most like feedback on their students' performance by organ system-based sections for the complete academic year. This collaborative effort could serve as a model for aligning national exams with course goals.

Clinical Clerkship↗

An overview of sexually transmitted diseases. Part III. Sexually transmitted diseases in HIV-infected patients.

UNLABELLED: The HIV epidemic has dramatically altered the field of sexually transmitted diseases (STDs). HIV infection is unique among sexually transmitted diseases because it can modify the clinical presentation and features of other STDs. Conversely, other STDs can affect the transmission of HIV. This review is the third part of a series that has provided a general overview of STDs. In this article, genital ulcer diseases (genital herpes, syphilis, chancroid, lymphogranuloma venereum, and granuloma inguinale), human papillomavirus infection (anogenital warts and subclinical infections), molluscum contagiosum, human herpesvirus 8 infection, viral hepatitis, and ectoparasitic infestations (scabies and pediculosis pubis) are discussed as they occur in HIV-infected hosts. Additional features as they relate to HIV-infected patients, such as epidemiology and transmission, are discussed when applicable. LEARNING OBJECTIVE: At the conclusion of this learning activity, participants should improve their understanding of sexually transmitted diseases in the HIV-infected host.

HIV Infections↗

Vaccines for bacterial sexually transmitted infections: a realistic goal?

Bacterial infections of the genital tract (gonorrhea, chlamydia, chancroid, syphilis) are common and cause significant morbidity. Their importance is heightened by recent appreciation of their roles in facilitation of transmission of the human immunodeficiency virus (HIV). Each is capable of causing repeated infections, suggesting lack of permanent broadly effective immunity. An effective vaccine has yet to be developed for any of these diseases. Rapid progress in understanding the molecular basis for pathogenesis of infection, including mechanisms for escape from otherwise effective immune surveillance and mechanisms for causing injury to host cells, has stimulated renewed efforts to make vaccines for some of these infections. Progress has been greatest for Neisseria gonorrhoeae and Chlamydia trachomatis. Present emphasis is on the major or principal outer membrane proteins of N. gonorrhoeae and C. trachomatis, based on evidence for neutralizing antibodies directed against surface-exposed variable domains of each of these proteins. Other surface-exposed proteins, including the iron-repressible transferrin receptor in gonococci and certain heat-shock proteins in chlamydia, also may be targets for vaccines. Although much remains to be learned, cautious optimism is warranted.

Humans↗

A diffusible cytotoxin of Haemophilus ducreyi.

Little is known about the virulence mechanisms employed by Haemophilus ducreyi in the production of genital ulcers. This Gram-negative bacterium previously has been shown to produce a soluble cytotoxic activity that kills HeLa and HEp-2 cells. We have now identified a cluster of three H. ducreyi genes that encode this cytotoxic activity. The predicted proteins encoded by these genes are most similar to the products of the Escherichia coli cdtABC genes that comprise the cytolethal distending toxin (CDT) of this enteric pathogen. Eleven of 12 H. ducreyi strains were shown to possess this gene cluster and culture supernatants from these strains readily killed HeLa cells. The culture supernatant from a single strain of H. ducreyi that lacked these genes was unable to kill HeLa cells. When the H. ducreyi cdtABC gene cluster was cloned into E. coli, culture supernatant from the recombinant E. coli clone killed HeLa cells. A monoclonal antibody that neutralized this soluble cytotoxic activity of H. ducreyi was shown to bind to the H. ducreyi cdtC gene product. This soluble H. ducreyi cytotoxin may play a role in the development or persistence of the ulcerative lesions characteristic of chancroid.

Amino Acid Sequence↗

Haemophilus ducreyi produces a novel sialyltransferase. Identification of the sialyltransferase gene and construction of mutants deficient in the production of the sialic acid-containing glycoform of the lipooligosaccharide.

Haemophilus ducreyi, the cause of the sexually transmitted disease chancroid produces a lipooligosaccharide (LOS) containing a terminal sialyl N-acetyllactosamine trisaccharide. Previously, we reported the identification and characterization of the N-acetylneuraminic acid cytidylsynthetase gene (neuA). Forty-nine base pairs downstream of the synthetase gene is an open reading frame (ORF) encoding a protein with a predicted molecular weight of 34,646. This protein has weak homology to the polysialyltransferase of Escherichia coli K92. Downstream of this ORF is the gene encoding the H. ducreyi homologue of the Salmonella typhimurium rmlB gene. Mutations were constructed in the neuA gene and the gene encoding the second ORF by insertion of an Omega kanamycin cassette, and isogenic strains were constructed. LOS was isolated from each strain and characterized by SDS-polyacrylamide gel electrophoresis, carbohydrate, and mass spectrometric analysis. LOS isolated from strains containing a mutation in neuA or in the second ORF, designated lst, lacked the sialic acid-containing glycoform. Complementation studies were performed. The neuA gene and the lst gene were each cloned into the shuttle vector pLS88 after polymerase chain reaction amplification. Complementation of the mutation in the lst gene was observed, but we were unable to complement the neuA mutation. Since it is possible that transcription of the neuA gene and the lst gene were coupled, we constructed a nonpolar mutation in the neuA gene. In this construct, the neuA mutation was complemented, suggesting transcriptional coupling of the neuA gene and the lst gene. Sialyltransferase activity was detected by incorporation of 14C-labeled NeuAc from CMP-NeuAc into trichloroacetic acid-precipitable material when the lst gene was overexpressed in the nonpolar neuA mutant. We conclude that the lst gene encodes the H. ducreyi sialyltransferase. Since the lst gene product has little, if any, structural relationship to other sialyltransferases, this protein represents a new class of sialyltransferase.

Amino Acid Sequence↗

A novel heme protein, the Cu,Zn-superoxide dismutase from Haemophilus ducreyi.

Haemophilus ducreyi, the causative agent of the genital ulcerative disease known as chancroid, is unable to synthesize heme, which it acquires from humans, its only known host. Here we provide evidence that the periplasmic Cu,Zn-superoxide dismutase from this organism is a heme-binding protein, unlike all the other known Cu,Zn-superoxide dismutases from bacterial and eukaryotic species. When the H. ducreyi enzyme was expressed in Escherichia coli cells grown in standard LB medium, it contained only limited amounts of heme covalently bound to the polypeptide but was able efficiently to bind exogenously added hemin. Resonance Raman and electronic spectra at neutral pH indicate that H. ducreyi Cu,Zn-superoxide dismutase contains a 6-coordinated low spin heme, with two histidines as the most likely axial ligands. By site-directed mutagenesis and analysis of a structural model of the enzyme, we identified as a putative axial ligand a histidine residue (His-64) that is present only in the H. ducreyi enzyme and that was located at the bottom of the dimer interface. The introduction of a histidine residue in the corresponding position of the Cu,Zn-superoxide dismutase from Haemophilus parainfluenzae was not sufficient to confer the ability to bind heme, indicating that other residues neighboring His-64 are involved in the formation of the heme-binding pocket. Our results suggest that periplasmic Cu,Zn-superoxide dismutase plays a role in heme metabolism of H. ducreyi and provide further evidence for the structural flexibility of bacterial enzymes of this class.

Amino Acid Sequence↗

Sexually-transmitted diseases, AIDS and traditional healers in Mozambique.

Qualitative research was conducted with traditional healers in Manica Province, Mozambique to develop an empirical, culturally-appropriate strategy for communication between government and traditional healers related to the prevention of STDs including AIDS. Most Manica healers regard AIDS as a new disease for which they lack medicines. However, when questioned on other sexually transmitted diseases, as defined by healers themselves, relatively complex disease taxonomies based on fine distinctions between symptoms emerged. Manica healers recognize two broad categories of STDs: siki and nyoka-related. The former seems to correspond with the more serious common STDs of Western biomedicine--syphilis, gonorrhea, chlamydia and chancroid--and is believed to be caused by a common invisible, microscopic agent, khoma. Nyoka-related illnesses are understood in terms of traditional ideas of pollution, and denote less serious, self-limiting genito-urinary conditions. Healers express great faith in the efficacy of traditional medicines. Based on the ethnomedical research findings, a culturally-sensitive and -specific AIDS/STD health education strategy for Manica indigenous healers was developed and began operating in a week-long workshop held in Chimoio, Mozambique in November 1991.

Acquired Immunodeficiency Syndrome↗