Jennie Ciak

Efficacy trial of a parenteral gonococcal pilus vaccine in men

A randomized, placebo-controlled, double-blind efficacy trial of a purified gonococcal pilus vaccine composed of a single pilus type was tested in 3123 men and 127 women volunteers. Either 100 micrograms of vaccine or a placebo was given intradermally on day 1 and day 14. Each group was evenly matched with respect to age, sex, prior history of a sexually transmitted disease, sexual exposure during the study and attrition from the study. None of the women volunteers acquired gonorrhoea during the trial. In the male volunteers, 108 vaccine and 102 placebo recipients acquired gonorrhoea 15 days or later after the initial immunization. Vaccines developed a sustained ELISA antibody response to homologous and heterologous pili, but the latter titres were approximately 40% as high as the homologous pilus antibody rises. There were, however, no increases in inhibition of attachment antibody (IEA) titres. Local antibodies (semen) against homologous and heterologous strains were also elicited (ELISA). The vaccine was safe and did not alter the clinical expression of disease. This gonococcal pilus vaccine composed of a single pilus type failed to protect men against gonococcal urethritis.

Chloroquine: Mode of Action

The drug chloroquine is bactericidal for Bacillus megaterium; it inhibits DNA and RNA biosynthesis and produces rapid degradation of ribosomes and dissimilation of ribosomal RNA. Inhibition of protein synthesis is also observed, evidently as a secondary effect. Inhibition of DNA replication is proposed as a general mechanism of the antimicrobial action of chloroquine.

Quinacrine (Atebrin): Mode of Action

Quinacrine at a concentration of 8 x 10-4 mole per liter is bactericidal for Escherichia coli, blocks DNA synthesis, and inhibits the syntheses of RNA and protein strongly. At a concentration of 2x 10-4 mole per liter, the drug is bacteriostatic, the syntheses of protein and DNA (but not that of RNA) are partially inhibited, and the bacteria grow into giant filaments. Impairment of DNA replication is proposed as the mode of action of quinacrine.

Interralations between nucleic acid and protein biosynthesis I. Synthesis and fate of bacterial nucleic acids during exposure to, and recovery from the action of chloramphenicol☆

Cells of E. coli B/r, whose protein synthesis is inhibited by chloramphenicol, accumulate several times the amounts of intracellular nucleic acids contained in log-phase bacteria before the onset of chloramphenicol-induced bacteriostasis. Upon removal of chloramphenicol the bacteria pass through a recovery phase during which much of the excess of nucleic acids is ejected from the cells before growth and multiplication are resumed. It is thought that these conditions result from the imbalanced synthesis of normal nucleic acids under the influence of chloramphenicol rather than from the formation and elimination of abnormal polynucleotides.

ELIMINATION OF BACTERIAL EPISOMES BY DNA-COMPLEXING COMPOUNDS

We propose the hypothesis that chemical substances which bind to doublehelical DNA by intercalation will eliminate bacterial episomes through a molecular mechanism of action by which closed, circular episomal DNA is converted into unnatural left-handed supercoils and cannot be replicated in this artificial conformation; the present study was undertaken in order to test this hypothesis, which was originally suggested to us by the effects of aminocridines on bacterial episomes. Aminoacridines produce a variety of genetic effects in microorganisms. Acriflavine is a mitochondria1 mutagen in yeast1 and in trypanosomesgl as well as a chromosomal frameshift mutagen in bacterial viruses.2 In contrast, the antimalarial drug, quinacrine, acts as an antimutagen in b a ~ t e r i a . ~ , ~ The first indication that aminoacridines have effects on episomes came from observations5 that acriflavine eliminated the F factor in Escherichia coli K-12, and from the work of Watanabe and F ~ k a s a w a ~ ~ ~ on the elimination of R factors from enteric bacteria by acriflavine and acridine orange. The elimination of R factors is conventionally referred to as the “curing” effect. Freifelder and Freifelder have recently found8.9 the F’ lac episome to be supercoiled, closed circular DNA. That R factors are DNA has been established by numerous workers,lO-lZ and two R factors conferring upon Proteus mirabilis resistance to streptomycin and sulfanilamide, have been shown to be closed, circular supercoiled DNA.13 In our work we have assumed that the R factors in our test strain of E. coli in vivo were likewise supercoiled in conformation. Stimulated by the mutagenic effects of aminoacridines, Lerman14 undertook a series of studies on the structure of the complex of acridines with linear DNA, which resulted in the establishment of the intercalation theory and explained the strong binding of substituted acridines to double-helical DNA. The theory holds that the acridine ring system becomes inserted or intercalated between the levels of base pairs into the double helix. The spaces for these insertions are created through local untwisting of DNA by an estimated 12” of rotation per one intercalated molecule that causes a separation between normally adjacent base pairs of approximately 3.5 A but does not disturb the pattern of hydrogen bonds between the paired bases. Not only acridines, but also other flat N-heterocyclic substances are intercalated into DNA, e.g., ethidium bromide,15 chloroquine,16 miracil D,17 quininela and berberine.lO Intercalation into supercoiled DNA produces characteristic conformational transitions in this type of DNA.20,21 Increasing numbers of individual intercalations cause progressive unwinding of superhelices by local untwisting and gradual decrease in the number of right-handed supercoils. At a defined equivalence

Elimination of Resistance Determinants from R-Factor R1 by Intercalative Compounds

Eighteen deoxyribonucleic acid (DNA)-complexing compounds, among them 15 intercalative substances, and, additionally, nalidixic acid eliminated with different frequencies four antibiotic resistance determinants from the R-factor R1, carried by Salmonella typhimurium. Eliminating concentrations did not inhibit growth of the bacteria. The most active compound was “nitroacridine II” {1-diethylamino-3-[(6-nitro-9-acridinyl)amino]propanol}. When 14 compounds which had been tested at a standard concentration of 10−4 M were listed according to decreasing activities of elimination of the four resistance determinants, a nearly consistent activity sequence was revealed. Frequencies of elimination of the kanamycin resistance determinant correlated directly with the binding of compounds to DNA, i.e., with end points of their displacement of methyl green from the methyl green-DNA complex. We propose that the observed eliminations resulted from selective toxicity for plasmidic template DNA and inhibitions of R-factor replication.

A Prospective Randomized Trial of Ofloxacin vs. Doxycycline in the Treatment of Uncomplicated Male Urethritis

One hundred fourteen men with uncomplicated urethritis were randomized to receive 1 week of therapy with either doxycycline (100 mg twice daily) or ofloxacin (300 mg twice daily). Of the 109 men completing the post-treatment visit, 56 received ofloxacin and 52 (93%) were clinically cured. Forty four (83%) of the 53 men treated with doxycycline were cured. All 30 patients with gonorrhea (including three with penicillinase-producing Neisseria gonorrhoeae [PPNG] isolates) who were treated with ofloxacin became culture-negative, as compared with 32 of 34 patients receiving doxycycline. In contrast, three of 18 patients with Chlamydia trachomatis were microbiologic failures after ofloxacin therapy, while all ten treated with doxycycline were cured. Adverse effects of both treatment regimens were generally mild, and compliance was excellent except for one patient receiving doxycycline. These results show that ofloxacin, in a dosage of 300 mg taken orally twice daily for seven days, is an effective treatment for uncomplicated urethritis in men but may not reliably cure chlamydial infections.

Studies on the mode of action of streptomycin II. Effects of streptomycin on the synthesis of proteins and nucleic acids and on cellular multiplication in Escherichia coli

Abstract Addition of streptomycin to exponentially growing cultures of Escherichia coli resulted in cessation of net protein formation. This effect is considered to be specific because other important processes, such as cellular multiplication and biosynthesis of RNA and DNA, were less affected by streptomycin and did proceed at decreasing rates. While the primary mechanism of action of streptomycin remains to be elucidated, no cellular process of a vital importance equal to that of protein synthesis is known to be inhibited by streptomycin to an equal extent.

Elimination of Plasmidic Determinants by DNA-Complexing Compounds

Solutions to problems posed by R-factor determined multiresistance of pathogenic bacteria to chemotherapeutic drugs might be approached by several avenues. Firstly, one might search for new chemotherapeutic drugs. Secondly, one could think of interfering with the formation of R-factor gene products through inhibition of the transcription of messenger RNA or of its translation into proteins. In instances in which new drugs had these modes of action, the two first approaches would become unitary. Thirdly, one might hope to forestall the recombinatorial formation of new R-factors. Fourthly, one could think of inhibiting the transmission of R-factors, and, lastly, one might attempt to eliminate R-factors by selective inhibition of R-factor DNA replication. To the extent to which this replication is required for recombination of plasmidic genes into new R-factors or for transmission, the last three approaches would be served jointly by effective inhibition of plasmidic DNA replication. This is the approach which we have taken.

Bactericidal Effects of Combinations of Ampicillin with Anti-R-Plasmid Compounds on Salmonella typhimurium R1+

Salmonella typhimurium R1+, resistant to 2,500 μg of ampicillin per ml, was rapidly killed by combinations of 60 μg of ampicillin per ml with quinacrine (4 × 10−4 M), ethidium bromide (10−4 M), tilorone (10−4 M), or Nitroakridin 3582 (5 × 10−6 M).