Kasugamycin resistance: 30S ribosomal mutation with an unusual location on the Escherichia coli chromosome.

A mutation in Escherichia coli to resistance to the aminoglycoside antibiotic kasugamycin alters the 30S ribosomal subunit. Though all other known 30S ribosomal mutations are located in a cluster in the streptomycin region, kasugamycin resistance is located at a distance from this region, near the leucine region.

Conjugal transfer of the gonococcal penicillinase plasmid.

Certain gonococci, which heretofore have lacked a conjugal mating system, can sexually transfer a small plasmid (4.5 x 10)6) daltons) which carries the gene for beta-lactamase production. Frequencies of conjugal transfer were similar into diverse recipients (other gonococci, Neisseria flava, and Escherichia coli), which suggests that gonococci may transfer the plasmid promiscuously in nature.

Cloning and constitutive expression of structural genes encoding gonococcal porin protein in Escherichia coli and attenuated Salmonella typhimurium vaccine strains.

Previous reports [Gotschlich et al., Proc. Natl. Acad. Sci. USA 84 (1987) 8135-8139; Carbonetti and Sparling, Proc. Natl. Acad. Sci. USA 84 (1987) 9084-9088; Carbonetti et al., Proc. Natl. Acad. Sci. USA 85 (1988) 6841-6845] concluded that synthesis of the porin protein (Por) from Neisseria gonorrhoeae in Escherichia coli was toxic to that organism, which limited studies of the biology of Por in foreign hosts. We assembled intact por genes from the gonococcal strains, FA19 (serogroup PIA) and FA6434 (a hybrid Por containing epitopes from serogroups PIA and PIB), and observed stable expression in E. coli without evident toxicity. Expression of por from strain MS11 (serogroup PIB) in E. coli was difficult, but por from MS11 was expressed without toxicity when the -35 region of the por promoter was removed. Encouraged by this, we moved por from E. coli into attenuated Salmonella typhimurium strains and expressed por either in single copy from the chromosome or in multiple copy from plasmids. Expression levels of por in S. typhimurium were higher from plasmids than from the chromosome, probably due to a gene dosage effect. This work will enable study of the immune response to Por in mice vaccinated orally with live S. typhimurium.

Intravenous acyclovir therapy of first episodes of genital herpes: a multicenter double-blind, placebo-controlled trial.

PURPOSE: A collaborative multicenter double-blind, placebo-controlled trial of intravenous acyclovir treatment of first-episode genital herpes was performed in order to substantiate previous findings on the efficacy and safety of this drug, to evaluate the influence of parenteral therapy on recurrence frequency, and to obtain further data on the natural history of genital herpes. PATIENTS AND METHODS: Eighty-two patients with first episodes of genital herpes simplex virus (HSV) infection were randomly assigned in a double-blind fashion to treatment with intravenous acyclovir (5 mg/kg every eight hours) or placebo for five days. Before therapy, all lesions in the genital/perineal area and in extragenital sites were cultured. New lesions appearing in both areas after the onset of therapy were cultured separately. Lesions in all groups were cultured until completely healed. Sera were collected from all patients on entry to the study and on Day 21 to determine presence or absence of antibodies to HSV-1 and HSV-2. Time to healing, time to crusting, time to cessation of viral shedding, and appearance of new lesions during therapy were compared for each treatment group. RESULTS: Patients receiving acyclovir experienced a significant reduction in the median duration of pain (4.3 versus 4.8 days, p = 0.019), viral shedding (1.9 versus 8.4 days, p less than 0.001), and time to healing (8.4 versus 11.5 days, p = 0.02) compared with placebo recipients. These differences were largely attributable to the effect of therapy in the subset of patients with primary disease in whom acyclovir reduced the median duration of pain from 10.6 days to 4.2 days, the median duration of viral shedding from 17.1 days to 1.9 days, and the median time to healing from 14.2 days to 8.3 days. The rate of subsequent recurrence of genital herpes was not altered by acyclovir treatment: 24 of 32 acyclovir recipients (75 percent) experienced one or more recurrences during a mean follow-up of 14 months compared with 19 of 27 placebo recipients (70 percent). Among patients experiencing recurrences, the mean number of recurrences per month among acyclovir recipients was 0.25 compared with 0.19 for patients given placebo. CONCLUSION: This multicenter trial confirms the efficacy of intravenous acyclovir in the management of first-episode genital herpes, especially in patients with primary infection. However, therapy did not alter the frequency of recurrences.

Vaccines for classic sexually transmitted diseases.

Sexually transmitted diseases (STDs) can substantially increase the morbidity and mortality of exposed adults and children. Despite the advent of new antibiotics and focus on behavioral interventions such as condom use, attempts to limit the spread of STDs have been largely unsuccessful. Vaccines have received increasing attention as a potential strategy for STD control. This article focuses on the current status of vaccine research for five classic STDs: gonorrhea, genital herpes, syphilis, chancroid, and chlamydia.

Pseudo-transposition of a Tn5 derivative in Neisseria gonorrhoeae.

We constructed a Tn5 derivative for potential use in transposon mutagenesis of Neisseria gonorrhoeae. It was incorporated into the chromosome apparently at random following transformation, but the insertion events were dependent on a functional RecA and independent of a functional transposase. Furthermore, in most cases there was an incomplete transposon inserted with little or no IS50 insertion sequence. These observations suggest that Tn5 transposition may not be possible in N. gonorrhoeae and that this organism may have an unexplored illegitimate recombination system.

The roles of sexual and asexual gene transfer in emergence of antibiotic resistant gonococci.

Antibiotic resistance is an increasing problem among gonococci, not only in Asia, Africa and other regions, but also in the U.S.A. Resistance is of two fundamental types: plasmid-mediated, due to production of a beta-lactamase, and non-plasmid-mediated, due to additive effects of chromosomal mutations that decrease antibiotic entry or alter the target site for antibiotic action. Evidence suggests that conjugal (sexual) transfer of plasmids takes place between gonococci in nature, and that asexual transfer by naked transforming DNA may result in transfer of chromosomal resistance genes in nature. Although these events may be relatively rare in vivo, they probably contribute to the ability of the gonococcus to adapt to selective pressure of antibiotics.

The Impact of Molecular Technology on STD Control : A Historical Perspective.

Sexually transmitted diseases have afflicted humankind for millennia, based on references to apparent gonorrhea or nongonococcal urethritis in the Old Testament (Leviticus). For most of history there has been no means of specific diagnosis, and clinical diagnosis of syndromes was fraught with error. Usually, this made no difference because there was no specific therapy and no means of prevention other than abstinence or monogamy, which was slightly effective at best (witness the very high prevalence of syphilis in much of Europe and the USA before advent of specific therapy, approaching 10% in many populations and 25% in some). Occasionally, syndromic diagnosis did cause serious consequences. If we could talk with John Hunter today, he certainly would bemoan the absence in his time of specific diagnostic tests for gonorrhea and syphilis. Had he had access to such tests, he certainly would not have inoculated himself with urethral exudate from a patient with gonorrhea and subclinical syphilis, resulting in the acquisition of both gonorrhea and syphilis (1)! Not only did he suffer from both diseases, but he also understandably but incorrectly concluded that both diseases had the same etiology, which held back the entire field until the discovery that Neisseria gonorrhoeae and Treponema pallidum were separate causes of the very distinctive diseases.

An epidemiological evaluation of the use of microbiological tools for identifying gonorrhoea infection networks.

We aimed to assess the utility of various techniques for identifying gonorrhoea infection networks. All residents of a non-metropolitan North Carolina county visiting a sexually transmitted disease (STD) clinic during a 17-month period were screened for gonorrhoea. Infection networks were estimated by serovar type combined with antibiotic resistance, arbitrarily primed polymerase chain reaction (AP-PCR), or temporal clustering. The residential addresses of infected patients were geocoded and mapped. Among 2 serovar types, the presence of distinguishing characteristics of a network, based on questionnaire data, was assessed with prevalence ratios and 95% confidence intervals (CIs) relative to those not in the network. Twenty-five serovar types were identified among 759 gonorrhoea infections. In one serovar, the networks further delineated by temporal clusters correlated with particular AP-PCR types. In most instances, however, different typing techniques painted different network pictures. No refined serovar network stood out as having a particular set of characteristics that could be used to shape intervention. Teasing out an individual infection network with unique characteristics will require the development and use of other microbiological tools.

Host defences and the vaginal mucosa. A re-evaluation.

The portal of entry for most pathogens is at the mucosal surface, and mucosal defences afford the host the earliest opportunity to ward off infection. The vagina is exposed to considerable trauma, and harbours a complex microflora, but only a small number of microorganisms are associated with disease. It seems likely that mucosal defenses are important in this process. Mucosal secretions contain mucus, lysozyme, lactoferrin, zinc, fibronectin, and complement, all of which afford non-specific protection. In addition, secretory immunoglobulin A (IgA) concentration in these secretions increases in response to specific pathogens. Blood leukocytes migrate onto mucosal surfaces during infection with some microorganisms, and the interaction between phagocytic cells and genital pathogens has been the focus of intense investigation. Improved understanding of mucosal defences is crucial for prevention of infection.