Treatment of genitourinary tract infections with fluoroquinolones: clinical efficacy in genital infections and adverse effects.
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4-Quinolones↗
Biomedical subjects
D C Hooper
Publications and source records attributed to D C Hooper.
Mechanisms of quinolone resistance in Escherichia coli: characterization of nfxB and cfxB, two mutant resistance loci decreasing norfloxacin accumulation.
Two genetic loci selected for norfloxacin (nfxB) and ciprofloxacin (cfxB) resistance were characterized. Both mutations have previously been shown to confer pleiotropic resistance to quinolones, chloramphenicol, and tetracycline and to decrease expression of porin outer-membrane protein OmpF. nfxB was shown to map at about 19 min and thus to be genetically distinct from ompF (21 min), and cfxB was shown to be very closely linked to marA (34 min). cfxB was dominant over cfxB+ in merodiploids, in contrast to other quinolone resistance mutations. The two loci appear to interact functionally, because nfxB was not expressed in the presence of marA::Tn5. Both nfxB and cfxB decreased the expression of ompF up to 50-fold at the posttranscriptional level as determined in strains containing ompF-lacZ operon and protein fusions. Both mutations also decreased norfloxacin accumulation in intact cells. This decrease in accumulation was abolished by energy inhibitors and by removal of the outer membrane. These findings, in conjunction with those of Cohen et al. (S. P. Cohen, D. C. Hooper, J. S. Wolfson, K. S. Souza, L. M. McMurry, and S. B. Levy, Antimicrob. Agents Chemother. 32:1187-1191, 1988), suggest a model for quinolone resistance by decreased permeation in which decreased diffusion through porin channels in the outer membrane interacts with a saturable drug efflux system at the inner membrane.
Anti-Infective Agents↗
Isolation and characterization of an Escherichia coli strain exhibiting partial tolerance to quinolones.
Quinolone antimicrobial agents rapidly kill bacteria by largely unknown mechanisms. To study this phenomenon, a strain of Escherichia coli inhibited but inefficiently killed by (i.e., partially tolerant to) norfloxacin was isolated and characterized. E. coli KL16 (norfloxacin MIC, 0.10 microgram/ml; MBC, 0.20 microgram/ml) was mutagenized with nitrosoguanidine and cyclically exposed to 3 micrograms of norfloxacin per ml. After five cycles, a bacterial strain (DS1) which was killed 1,000-fold less than KL16 during 3 h of drug exposure was isolated. The MIC and MBC of norfloxacin for DS1 were 0.20 and 1.5 micrograms/ml, respectively. Over a range of norfloxacin concentrations, DS1 was killed 2 to 4 orders of magnitude less than KL16. DS1 grew more slowly than KL16 but after normalization for growth rate was killed four times less rapidly than KL16 at drug concentrations 10-fold higher than respective MICs. DS1 and KL16 cells filamented similarly upon exposure to norfloxacin. DS1 exhibited tolerance to other DNA gyrase A subunit antagonists (ofloxacin and ciprofloxacin) and DNA gyrase B subunit antagonists (novobiocin and coumermycin) but not to the aminoglycoside gentamicin, suggesting involvement of DNA gyrase. DS1 also appeared to be minimally tolerant to the beta-lactam cefoxitin. DS1 exhibited increased susceptibility to the mutagen methyl methanesulfonate, implying a defect in DNA repair. This report describes the first use of quinolone enrichment for isolation of a bacterial strain partially tolerant to quinolones. The study of defects in such tolerant strains offers an approach to an increased understanding of the mechanisms of bacterial killing by quinolones.
Anti-Infective Agents↗
Cross-resistance to fluoroquinolones in multiple-antibiotic-resistant (Mar) Escherichia coli selected by tetracycline or chloramphenicol: decreased drug accumulation associated with membrane changes in addition to OmpF reduction.
Chromosomal multiple-antibiotic-resistant (Mar) mutants of Escherichia coli, selected on agar containing low concentrations of tetracycline or chloramphenicol, were 6- to 18-fold less susceptible to the fluoroquinolones than were their wild-type E. coli K-12 or E. coli C parental strains. The frequency of emergence of such mutants was at least 1,000-fold higher than that of those selected by the fluoroquinolone norfloxacin directly. When Mar mutants, but not wild-type cells, were plated on norfloxacin, mutants resistant to high levels of norfloxacin (2 micrograms/ml) appeared at a relatively high (approximately 10(-7] frequency. In addition to decreased amounts of OmpF, Mar mutants had other outer membrane protein changes and were four- to eightfold less susceptible to fluoroquinolones than was an ompF::Tn5 mutant lacking only OmpF. Accumulation of [3H]norfloxacin was more than threefold lower in the Mar mutants than in wild-type cells and twofold lower than in the OmpF-deficient derivative. These differences were not attributable to a change in the endogenous active efflux system for norfloxacin in E. coli. Norfloxacin-induced inhibition of DNA synthesis was threefold lower in intact cells of a Mar mutant than in susceptible cells, but this difference was not seen in toluene-permeabilized cells. Insertion of Tn5 into marA (min 34.05 on the chromosome) led to a return of the wild-type patterns of norfloxacin accumulation, fluoroquinolone and other antimicrobial agent susceptibilities, and outer membrane protein profile, including partial restoration of OmpF. These findings together suggest that marA-dependent fluoroquinolone resistance is linked to decreased cell permeability, only part of which can be accounted for by the reduction in OmpF. Once mutated to marA, cells can achieve high levels of quinolone resistance at a relatively high frequency.
Anti-Infective Agents↗
Fluoroquinolone antimicrobial agents.
The fluoroquinolones, a new class of potent orally absorbed antimicrobial agents, are reviewed, considering structure, mechanisms of action and resistance, spectrum, variables affecting activity in vitro, pharmacokinetic properties, clinical efficacy, emergence of resistance, and tolerability. The primary bacterial target is the enzyme deoxyribonucleic acid gyrase. Bacterial resistance occurs by chromosomal mutations altering deoxyribonucleic acid gyrase and decreasing drug permeation. The drugs are bactericidal and potent in vitro against members of the family Enterobacteriaceae, Haemophilus spp., and Neisseria spp., have good activity against Pseudomonas aeruginosa and staphylococci, and (with several exceptions) are less potent against streptococci and have fair to poor activity against anaerobic species. Potency in vitro decreases in the presence of low pH, magnesium ions, or urine but is little affected by different media, increased inoculum, or serum. The effects of the drugs in combination with a beta-lactam or aminoglycoside are often additive, occasionally synergistic, and rarely antagonistic. The agents are orally absorbed, require at most twice-daily dosing, and achieve high concentrations in urine, feces, and kidney and good concentrations in lung, bone, prostate, and other tissues. The drugs are efficacious in treatment of a variety of bacterial infections, including uncomplicated and complicated urinary tract infections, bacterial gastroenteritis, and gonorrhea, and show promise for therapy of prostatitis, respiratory tract infections, osteomyelitis, and cutaneous infections, particularly when caused by aerobic gram-negative bacilli. Fluoroquinolones have also proved to be efficacious for prophylaxis against travelers' diarrhea and infection with gram-negative bacilli in neutropenic patients. The drugs are effective in eliminating carriage of Neisseria meningitidis. Patient tolerability appears acceptable, with gastrointestinal or central nervous system toxicities occurring most commonly, but only rarely necessitating discontinuance of therapy. In 17 of 18 prospective, randomized, double-blind comparisons with another agent or placebo, fluoroquinolones were tolerated as well as or better than the comparison regimen. Bacterial resistance has been uncommonly documented but occurs, most notably with P. aeruginosa and Staphylococcus aureus and occasionally other species for which the therapeutic ratio is less favorable. Fluoroquinolones offer an efficacious, well-tolerated, and cost-effective alternative to parenteral therapies of selected infections.
4-Quinolones↗
Effects of inhibition of the B subunit of DNA gyrase on conjugation in Escherichia coli.
Antagonism of the DNA gyrase B subunit in the donor bacterium by coumermycin or thermal inactivation inhibited transfer of plasmid R64drd-11. Coumermycin also inhibited Hfr transfer, with kinetics after drug removal suggesting that transfer resumed from the point of inhibition, in contrast to inhibition with nalidixic acid, after which transfer reinitiated from the origin of transfer.
Aminocoumarins↗
Norfloxacin, ciprofloxacin, and ofloxacin: current clinical roles.
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Bacteria↗
Endogenous active efflux of norfloxacin in susceptible Escherichia coli.
Escherichia coli was shown to have an energy-dependent reduced uptake of the fluoroquinolone antimicrobial agent norfloxacin. Studies of everted inner membrane vesicles suggested that this reduced accumulation involved a carrier-mediated norfloxacin active efflux generated by proton motive force with an apparent Km of 0.2 mM and a Vmax of 3 nmol min-1 mg of protein-1. Other hydrophilic, but not hydrophobic, quinolones competed with norfloxacin for transport. Porin (OmpF)-deficient E. coli cells were twofold less susceptible to norfloxacin and showed twice as much energy-dependent reduction in drug uptake. However, active efflux assayed in everted vesicles from the OmpF strain was unchanged compared with that in the parental strain. These findings suggest that in the OmpF mutant decreased outer membrane permeability, combined with active efflux across the inner membrane, in some manner results in decreased steady-state uptake of norfloxacin and lowered drug susceptibility.
Anti-Infective Agents↗
Norfloxacin: a new targeted fluoroquinolone antimicrobial agent.
Norfloxacin is an oral fluoroquinolone antimicrobial agent recently released for the treatment of uncomplicated and complicated urinary tract infections. The drug antagonizes DNA gyrase, an enzyme essential for bacterial DNA replication. Norfloxacin is more potent and broader in spectrum than the earlier developed analogue, nalidixic acid, and is active in vitro against virtually all bacterial pathogens causing urinary tract and gastrointestinal infections, aerobic gram-negative bacilli causing sepsis in neutropenic patients, and Neisseria gonorrhoeae. The drug is administered orally twice daily and achieves high concentrations in urine, stool, renal tissue, and bile. Norfloxacin was at least as effective as currently used agents in treating urinary tract infections, and, in limited studies, bacterial gastroenteritis, gonorrhea, bacterial prostatitis, and prevention of gram-negative bacillary infection in neutropenic patients. Adverse drug effects were mild and included disturbances of the gastrointestinal tract and the central nervous system. Norfloxacin shows promise as an antibacterial agent for genitourinary and gastrointestinal infections.
Animals↗
Mechanisms of action of and resistance to ciprofloxacin.
Ciprofloxacin and other newer quinolone antimicrobial agents exhibit increased potency and decreased frequency of spontaneous bacterial resistance in comparison with older analogues such as nalidixic acid. New and published observations on the mechanisms of action of and resistance to ciprofloxacin in Escherichia coli are presented and discussed. Genetic and biochemical studies have identified the A subunit of the essential bacterial enzyme DNA gyrase as a target of ciprofloxacin and other quinolones. For a series of quinolones, inhibition of purified DNA gyrase correlated with antibacterial activity. The bactericidal activity of ciprofloxacin and ofloxacin is, in contrast to that of certain other quinolones, somewhat less affected by rifampin and cell starvation, suggesting the existence of a site of drug action in addition to DNA gyrase. The frequency of selection of spontaneous single-step resistance mutants of E. coli was more than 100-fold lower with ciprofloxacin than with nalidixic acid. Strains highly resistant to ciprofloxacin could, nevertheless, be selected by serial passage on drug-containing agar. Two mutations contributing to this high level of resistance were analyzed. One, designated cfxA, conferred a 16-fold increase in drug resistance and mapped in a location consistent with a gyrA mutation; similar increases in resistance to ciprofloxacin were seen with gyrA mutations selected for resistance to other quinolones. The other mutation, cfxB, conferred pleiotropic resistance to ciprofloxacin, tetracycline, and chloramphenicol and appeared to be an allele of the multiple antibiotic resistance gene marA. The mutation cfxB was associated with a decreased amount of porin outer membrane protein OmpF, suggesting that drug permeation may occur in part through this channel. In summary, the A subunit of DNA gyrase is a target of ciprofloxacin and other quinolones. Ciprofloxacin resistance appears to occur both by mutation in this target and by alteration of drug permeation through the outer membrane of the cell.
Anti-Bacterial Agents↗
Murine T cells reactive against autologous erythrocytes: evidence for in vitro and in vivo priming with mouse and rat red blood cells.
Normal mice are shown to harbor T cells that can be sensitized to proliferate against autologous red blood cells (RBC). These autoreactive cells were primed in vitro and in vivo with mouse as well as heterologous rat RBC, the in vivo administration of which has been previously shown to trigger the production of auto-RBC antibodies. Two broad classes of specificity are detected following priming: T cells cross-reactive for similar determinants coexpressed by mouse and rat RBC, and T cells specific for antigens restricted to self-RBC. These findings indicate that clonal deletion of self-RBC-reactive T cells is far from complete. The comparison of different in vitro and in vivo immunization protocols revealed the possible existence of several levels of immunoregulatory control which may prevent the expression of autoimmunity by these T cells.
Animals↗
Specific helper T cell reactivity against autologous erythrocytes implies that self tolerance need not depend on clonal deletion.
Using a culture system which supports primary T cell proliferative responses to various antigens we have detected mouse red blood cell (RBC)-reactive T cells in lymphoid tissues from untreated mice. The release of significant amounts of interleukin 2 (IL2) indicates that T helper (or helper/inducer) cells are activated by stimulation with RBC. Upon restimulation in vitro these cells proliferate specifically against mouse RBC with the kinetics and magnitude characteristic of a secondary response. Since autologous RBC are tolerated in vivo in spite of the presence of such specifically reactive T helper cells, these findings imply that self tolerance, even to certain nonsequestered antigens, may depend largely on regulatory mechanisms rather than on clonal deletion or inactivation.
Animals↗
Murine pregnancy-associated modulations in lymphocyte reactivity to mitogens: identification of the cell populations affected.
Lymphocytes from the thymus, spleen and inguinal lymph nodes of syngeneically pregnant and non-pregnant mice were compared in their responsiveness to polyclonal stimulation by mitogen. Pregnancy-associated changes in mitogen reactivity were detected, on a cell-per-cell basis, in thymocytes (increased) and spleen cells (decreased) but not in lymph node cells. The hyperreactivity of thymocytes during pregnancy correlated with physiological involution of the thymus occurring through the selective loss of relatively immature, non-mitogen-reactive, Lyt 1+2+ cells. The remaining cells were found largely to be mature Lyt 1+2- T cells with the capacity to respond to mitogenic stimulation. It is most likely the relative increase in the proportion of these Lyt 1+2- cells that causes the hyper-responsiveness of thymocytes to mitogens observed during pregnancy. On the other hand, while spleen cells from pregnant animals gave lower responses to mitogens than those from control virgin females, isolated splenic T cells from the two groups proved equally reactive to T cell mitogens. This supports the contention that at least some aspects of immunity during pregnancy are down-regulated by inhibitory cells within the non-T cell compartment. The results demonstrate the importance of identifying the reactive cell population in studies on changes in lymphocyte responsiveness in pregnancy.
Animals↗
Antagonism of wild-type and resistant Escherichia coli and its DNA gyrase by the tricyclic 4-quinolone analogs ofloxacin and S-25930 stereoisomers.
The mechanism of action of the quinolone analogs ofloxacin and S-25930, which are unusual because of the presence of a third ring with an asymmetric carbon, was studied. Drug-resistant strains of Escherichia coli were selected by serial passage in the presence of ofloxacin, and a mutation was mapped near the gyrA gene of DNA gyrase. DNA gyrase containing the A subunit purified from this strain as compared with the isogenic wild-type strain exhibited increased resistance to ofloxacin, proving that the mutation was located in the gyrA gene. For S-25930, the S stereoisomer was more potent than the R isomer in inhibiting wild-type E. coli and DNA gyrase containing an A subunit isolated from this strain. Both isomers had decreased potency against the isogenic ofloxacin-resistant (gyrA) strain and its purified enzyme, but the S isomer remained more potent than the R isomer. These studies, using a combined genetic and biochemical approach, demonstrate (i) that DNA gyrase is a target of the tricyclics ofloxacin and S-25930, (ii) that serial exposure to ofloxacin can select resistance to tricyclic quinolone agents by mutation in the gyrA gene, and (iii) that the more potent antibacterial activity of S relative to R S-25930 correlates with increased activity against DNA gyrase for both wild-type and ofloxacin-resistant (gyrA) isogenic strains.
Anti-Bacterial Agents↗
Visualization of the mitochondrion-kinetoplast in viable Trypanosoma cruzi with rhodamine 123.
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Animals↗
Solid-phase radioimmunoassay for IgG antibodies to Staphylococcus epidermidis. Use in serious coagulase-negative staphylococcal infections.
A radioimmunoassay (RIA) for human IgG antibodies to Staphylococcus epidermidis was compared with an agar-gel-diffusion assay in patients with a variety of infections. The RIA was sensitive and reproducible and discriminated between endocarditis and uncomplicated bacteremias due to coagulase-negative staphylococci. Anti-S epidermidis antibodies by RIA were elevated in 16 (89%) of 18 patients with coagulase-negative staphylococcal endocarditis but in none of 28 patients with uncomplicated bacteremia (n = 18) or with blood culture contaminated with these organisms (n = 10). Cross-reacting IgG antibodies to S epidermidis antigens were also detected by RIA in 13 (76%) of 17 patients with Staphylococcus aureus endocarditis but in none of 17 patients with nonvalvular S aureus bacteremias and in none of 25 patients with endocarditis or bacteremia caused by other pathogens. Agar-gel-diffusion assay was less sensitive than RIA for detecting coagulase-negative staphylococcal endocarditis, being positive in nine (50%) of 18 such patients. This RIA may be useful in distinguishing patients with endocarditis from those with nonvalvular staphylococcemias or blood culture contamination.
Antibodies, Bacterial↗
Characterization of suppressor-inducer cells which control the production of rat erythrocyte-induced anti-erythrocyte autoantibodies.
Mice immunized with rat erythrocytes produce autoantibodies to their own red blood cells, distinct anti-rat agglutinins and autoantigen-specific suppressor cells. Suppressor cells were detected by adoptive transfer of rat erythrocyte-immunized spleen cells to naive recipients. Such recipients failed to make erythrocyte autoantibodies after immunization with rat erythrocytes although their anti-rat erythrocyte response was unimpaired. Depletion and enrichment studies were performed to identify the cell type(s) which transfer suppression. B cell depletion of rat erythrocyte-immunized spleen cells by passage over Ig/anti-Ig-coated bead columns abrogated the transfer of suppression. However, suppression was still transferred after rat erythrocyte immunized spleen cells were passed over beads coated with a complex of 4-azido-2-nitrophenyl (NAP)-mouse IgG-rabbit IgG anti-NAP suggesting that T cells bearing Fc gamma receptors are not responsible for suppression. Positively selected B cells from rat erythrocyte-immunized spleen cells caused some suppression of erythrocyte autoantibodies but only after high numbers of cells were transferred. Neither positively selected Lyt-1+2- nor Lyt-1-2+ T cell subpopulations transferred suppression. By contrast, rat erythrocyte-immunized spleen cells which contained a mixture of B memory and T cells were suppressive and retained their suppressor activity after removal of Lyt-1-2+ but not Lyt-1+2- cells. It is proposed that these Lyt-1+2-T cells belong to a distinct population of suppressor-inducer cells which together with memory B cells stimulate the generation of effector T suppressor cells in naive recipients.
Animals↗
Murine neonatal spleen contains natural T and non-T suppressor cells capable of inhibiting adult alloreactive and newborn autoreactive T-cell proliferation.
The spleen of neonatal mice is known to be a rich source of cells capable of suppressing a variety of immune functions of adult lymphocytes in vitro. From such observations has emerged the concept that the gradual development in ability to express immune functions after birth is due in part to the parallel normal physiological decay of naturally occurring regulatory suppressor cells. There is, however, some confusion in the literature as to the exact nature of the newborn of the newborn inhibitory cell type(s). In contrast to most previous reports which detect only a single type of neonatal suppressor cell, usually a T cell, we show here that newborn spleen harbors both T and non-T inhibitory cells. Both types of suppressor cells could be shown to suppress the proliferative response of adult spleen to alloantigens as well as newborn T cells reacting against self-Ia antigen in the autologous mixed lymphocyte reaction (AMLR). Newborn suppressor T cells were characterized as being non-adherent to Ig-anti-Ig affinity columns, soybean agglutinin receptor negative (SBA-), and susceptible to lysis by anti-T-cell specific antiserum plus complement. Non-T suppressor cells were identified as non-phagocytic, SBA receptor positive (SBA+), and resistant to cytotoxic treatment with anti-T-cell antibodies and complement. The apparent controversy surrounding previous reports as to the T versus non-T nature of newborn suppressor cells can be reconciled by the present observation that both types of inhibitory cells coexist in the spleen. Furthermore, the demonstration that newborn suppressor cells can effectively regulate T-cell proliferative activity mediated by other newborn cells provides more direct support for the contention that such inhibitory cells play a physiological role in controlling immune responsiveness during early ontogeny.
Animals↗