Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:5.99.1.3 (topoisomerase)
9,911 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The increase in the use of the fluoroquinolones, including for the treatment of lower respiratory tract infections, seems to be associated with a parallel increase in bacterial resistance. We studied the activity of penicillin and six fluoroquinolones against 101 viridans group streptococci isolated from blood (58 erythromycin-susceptible and 43 erythromycin-resistant). The percentage of strains not susceptible to penicillin was 35% and there were statistically significant differences in the percentages of penicillin resistance between erythromycin-susceptible and -resistant strains. The fluoroquinolones studied showed good activity against our viridans group streptococci independent of their susceptibility to erythromycin. The norfloxacin MIC(50) and MIC(90) were 8 and 16 mg/l, respectively. Ofloxacin and ciprofloxacin showed the same activity (MIC(50) 1 mg/l and MIC(90) 2 mg/l); levofloxacin was similar with MIC(50) and MIC(90) of 1 mg/l. The fluoroquinolones with enhanced activity were moxifloxacin and trovafloxacin (MIC(50) 0.12 mg/l and MIC(90) 0.25 mg/l). However, we found two strains resistant to trovafloxacin (MIC = 4 mg/l) that showed reduced susceptibility to all the fluoroquinolones tested, including moxifloxacin (MIC = 2 mg/l). Mutations in the topoisomerase genes parC and gyrA have been shown to occur in strains with reduced susceptibility; therefore, ongoing surveillance for the development of fluoroquinolone resistance in viridans streptococci is necessary.
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PMID:[In vitro activity of six fluoroquinolones and penicillin against 101 viridans group streptococci characterized by their susceptibility to erythromycin]. 1185 83

OBJECTIVE: To determine whether similar mutations to quinolone resistance in the gyrA subunit of DNA gyrase and the parC subunit of topoisomerase IV are occurring independently in genotypically unrelated clinical isolates of Acinetobacter spp., or whether worldwide clonal spread of particular resistant strains is occurring. METHODS: The genotypic relationships of 25 nosocomial isolates of Acinetobacter spp. from 15 locations in 11 different countries worldwide were examined by randomly amplified polymorphic DNA analysis. Quinolone resistance-determining regions of gyrA and parC were amplified by PCR and mutations were analyzed by restriction digestion with Hinfl and DNA sequencing. RESULTS: Twenty-four of the 25 Acinetobacter isolates were genotypically heterogeneous and 12 were resistant to both nalidixic acid and ciprofloxacin. Analysis of conserved gyrA and parC regions showed that all isolates with a ciprofloxacin MIC of 4 mg/L had a substitution of Ser83 with either Leu or Phe in the GyrA protein. Five of six isolates with ciprofloxacin MICs of 64 mg/L had additional substitutions of Ser80 with Leu in the ParC protein. CONCLUSIONS: Similar mutations to quinolone resistance, predominantly at codons 82--83 of gyrA, are occurring independently in genotypically distinct isolates of Acinetobacter spp. from different worldwide locations. Most isolates with high ciprofloxacin MICs also exhibited secondary mutations in parC at codons 79--80.
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PMID:Molecular epidemiology of quinolone resistance in Acinetobacter spp. 1186 39

The in vitro and in vivo activity of T-3912, a novel non-fluorinated topical quinolone, was compared with that of nadifloxacin, ofloxacin, levofloxacin, clindamycin, erythromycin and gentamicin. The in vitro activity of T-3912 against methicillin-susceptible Staphylococcus aureus, ofloxacin-resistant and methicillin-resistant S. aureus, Staphylococcus epidermidis, ofloxacin-resistant S. epidermidis, penicillin-resistant Streptococcus pneumoniae and Propionibacterium acnes was four-fold to 16 000-fold greater than that of other agents at the MIC90 for the clinical isolates. The activity of T-3912 was not influenced by grlA mutation in S. aureus, and the degree of MIC increase of T-3912 for grlA-gyrA double and triple mutants was lowest among the quinolones tested (nadifloxacin, levofloxacin and ofloxacin). The inhibitory activity of T-3912 was compared with other quinolones for DNA gyrase and topoisomerase IV of S. aureus SA113. T-3912 showed the greatest inhibitory activity for both enzymes among the quinolones tested. The isolation frequency of spontaneous mutants resistant to T-3912 was < 1.7 x 10(-9) and < 2.0 x 10(-9) for S. aureus SA113 and P. acnes JCM 6425, respectively. Furthermore, resistance to T-3912 could not be clearly detected in the 28th transfer by the serial passage method. T-3912 exhibited more potent bactericidal activity against S. aureus and P. acnes than nadifloxacin and clindamycin in a short time period. T-3912 in a 1% gel formulation showed good therapeutic activity against a burn infection model caused by S. aureus SA113, P. acnes JCM6425 and multidrug-resistant S. aureus F-2161. These results indicate that T-3912 is potentially a useful quinolone for the treatment of skin and soft-tissue infections and that its potent bactericidal activity might be able to shorten the treatment period.
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PMID:In vitro and in vivo antibacterial activity of T-3912, a novel non-fluorinated topical quinolone. 1186 45

Four amino acid substitutions, two in GyrA and two in ParC subunits of DNA gyrase and topoisomerase IV, respectively, are commonly responsible for fluoroquinolone resistance in Escherichia coli. In this study, an economical and time-efficient mismatch amplification mutation assay (MAMA) PCR was developed to detect mutations in the chromosomal gyrA and parC genes causing these substitutions. One hundred and twenty-one clinical E. coli isolates were tested by this assay, and the results confirmed that accumulation of amino acid alterations in GyrA and ParC correlates closely with stepwise increases in the MIC of ciprofloxacin.
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PMID:Use of a rapid mismatch PCR method to detect gyrA and parC mutations in ciprofloxacin-resistant clinical isolates of Escherichia coli. 1186 58

The frequency of fluoroquinolone-resistant Streptococcus pneumoniae has increased as fluoroquinolone administration for treatment of respiratory tract infections has increased. Levofloxacin treatment failed in a patient who had pneumococcal pneumonia and had received three previous courses of levofloxacin therapy. Susceptibility testing revealed high-level resistance to levofloxacin (minimum inhibitory concentration [MIC] > 32 microg/ml), and cross-resistance to moxifloxacin (MIC 4 microg/ml), trovafloxacin (6 microg/ml), and gatifloxacin (12 microg/ml). Sequencing of the quinolone-resistance determining region revealed a mutation of serine-81 to phenylalanine (Ser81-->Phe) in the gyrA region of DNA gyrase and a Ser79-->Phe mutation in the parC region of topoisomerase IV The patient was treated successfully with intravenous ceftriaxone followed by oral cefprozil. Clinicians must be aware of local resistance patterns and the potential for fluoroquinolone treatment failures in patients with infections caused by S. pneumoniae.
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PMID:Levofloxacin treatment failure in a patient with fluoroquinolone-resistant Streptococcus pneumoniae pneumonia. 1189 97

Fluoroquinolones acting equally through DNA gyrase and topoisomerase IV in vivo are considered desirable in requiring two target mutations for emergence of resistant bacteria. To investigate this idea, we have studied the response of Staphylococcus aureus RN4220 to stepwise challenge with sparfloxacin, a known dual-target agent, and with NSFQ-105, a more potent sulfanilyl fluoroquinolone that behaves similarly. First-step mutants were obtained with both drugs but only at the MIC. These mutants exhibited distinctive small-colony phenotypes and two- to fourfold increases in MICs of NSFQ-105, sparfloxacin, and ciprofloxacin. No changes were detected in the quinolone resistance-determining regions of the gyrA, gyrB, grlA, or grlB gene. Quinolone-induced small-colony mutants shared the delayed coagulase response but not the requirement for menadione, hemin, or thymidine characteristic of small-colony variants, a subpopulation of S. aureus that is often defective in electron transport. Second-step mutants selected with NSFQ-105 had gyrA(S84L) alterations; those obtained with sparfloxacin carried a gyrA(D83A) mutation or a novel gyrB deletion (DeltaRKSAL, residues 405 to 409) affecting a trypsin-sensitive region linking functional domains of S. aureus GyrB. Each mutation was associated with four- to eightfold increases in MICs of NSFQ-105 and sparfloxacin, but not of ciprofloxacin, which we confirm targets topoisomerase IV. The presence of wild-type grlB-grlA gene sequences in second-step mutants excluded involvement of topoisomerase IV in the small-colony phenotype. Growth revertants retaining mutant gyrA or gyrB alleles were quinolone susceptible, indicating that resistance to NSFQ-105 and sparfloxacin was contingent on the small-colony mutation. We propose that small-colony mutations unbalance target sensitivities, perhaps through altered ATP or topoisomerase levels, such that gyrase becomes the primary drug target. Breaking of target parity by genetic or physiological means eliminates the need for two target mutations and provides a novel mechanism for stepwise selection of quinolone resistance.
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PMID:Small-colony mutants of Staphylococcus aureus allow selection of gyrase-mediated resistance to dual-target fluoroquinolones. 1212 24

From the roots of Salvia prionitis a new tricyclic diterpene, saprirearine (1), a new anhydride-type compound, saprionide (2), a new 7,8-seco-abietane diterpene derivative, 7,8-seco-para-ferruginone (3), and two new 4,5-seco-5,10-friedo-abietane diterpenoids, 4-hydroxysaprorthoquinone (4) and 3-keto-4-hydroxysaprorthoquinone (5), were isolated. Their structures were established by spectroscopic methods and chemical transformation. Compound 3 showed antimicrobial activities against two Gram-positive organisms, Staphylococcus aureus and Micrococcus luteus, with MIC values of 20.0 and 15.0 microM, respectively. Compound 4 showed significant inhibition against topoisomerase Iota with an IC50 value of 0.8 microM. Compound 5 exhibited cytotoxic activities against HL-60 human leukemia and the SGC-7901 and MKN-28 stomach cancer cell lines, with IC50 values of 4.6, 0.2, and 0.3 microM, respectively.
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PMID:Bioactive abietane and seco-abietane diterpenoids from Salvia prionitis. 1214 63

We investigated the in vitro and in vivo antibacterial activities of pazufloxacin mesilate (PZFX mesilate), a new injectable quinolone, and obtained the following results. 1) The MIC50 and MIC90 values of PZFX against clinically isolated Gram-positive and -negative bacteria, ranged from 0.0125 to 12.5 micrograms/ml and 0.025 to 100 micrograms/ml, respectively. PZFX showed broad spectrum activity. The antibacterial activities of PZFX against quinolone-susceptible, methicillin-resistant Staphylococcus aureus, beta-lactamase-negative, ampicillin-resistant Haemophilus influenzae, extended spectrum beta-lactamase possessing Klebsiella pneumoniae and imipenem/cilastatine (IPM/CS)-resistant Pseudomonas aeruginosa were superior to those of ceftazidime (CAZ), ceftriaxone, IPM/CS, meropenem and panipenem/betamipron. 2) PZFX showed superior bactericidal activity against S. aureus, Escherichia coli, Proteus mirabilis, Serratia marcescens and P. aeruginosa to those of CAZ and IPM/CS after treatment for 15 minutes at the drug concentration equivalent to that in human serum at clinical dose to be continued for 15 minutes. 3) CAZ and IPM/CS had no bactericidal activity at the 16 times of MIC against P. aeruginosa in human polymorphonuclear leucocytes, while PZFX exhibited potent bactericidal activity in a dose-dependent manner against such bacteria. 4) PZFX inhibited both DNA gyrase and topoisomerase IV from S. aureus at nearly the same level. PZFX showed poor inhibitory activity against topoisomerase II from human placenta and showed high selectivity to bacterial topoisomerase. 5) PZFX mesilate showed superior therapeutic activity to that of CAZ with following infection model caused by S. aureus and P. aeruginosa or each; systemic infection with cyclophosphamide-treated mice, systemic infection in mice with high challenge doses, CMC pouch infection in rat, and calculus infection in rat bladder. 6) Intravenous administration of PZFX with high plasma concentration just after administration, showed more excellent therapeutic effect against the rat intraperitoneal infection, than p.o. and s.c. administration.
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PMID:[In vitro and in vivo antibacterial activities of pazufloxacin mesilate, a new injectable quinolone]. 1237 71

We determined the target enzyme interactions of garenoxacin (BMS-284756, T-3811ME), a novel desfluoroquinolone, in Staphylococcus aureus by genetic and biochemical studies. We found garenoxacin to be four- to eightfold more active than ciprofloxacin against wild-type S. aureus. A single topoisomerase IV or gyrase mutation caused only a 2- to 4-fold increase in the MIC of garenoxacin, whereas a combination of mutations in both loci caused a substantial increase (128-fold). Overexpression of the NorA efflux pump had minimal effect on resistance to garenoxacin. With garenoxacin at twice the MIC, selection of resistant mutants (<7.4 x 10(-12) to 4.0 x 10(-11)) was 5 to 6 log units less than that with ciprofloxacin. Mutations inside or outside the quinolone resistance-determining regions (QRDR) of either topoisomerase IV, or gyrase, or both were selected in single-step mutants, suggesting dual targeting of topoisomerase IV and gyrase. Three of the novel mutations were shown by genetic experiments to be responsible for resistance. Studies with purified topoisomerase IV and gyrase from S. aureus also showed that garenoxacin had similar activity against topoisomerase IV and gyrase (50% inhibitory concentration, 1.25 to 2.5 and 1.25 micro g/ml, respectively), and although its activity against topoisomerase IV was 2-fold greater than that of ciprofloxacin, its activity against gyrase was 10-fold greater. This study provides the first genetic and biochemical data supporting the dual targeting of topoisomerase IV and gyrase in S. aureus by a quinolone as well as providing genetic proof for the expansion of the QRDRs to include the 5' terminus of grlB and the 3' terminus of gyrA.
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PMID:Dual targeting of DNA gyrase and topoisomerase IV: target interactions of garenoxacin (BMS-284756, T-3811ME), a new desfluoroquinolone. 1238 38

Gemifloxacin, a novel quinolone with potent activity against Staphylococcus aureus, was 8- to 16-fold more active against wild-type S. aureus than ciprofloxacin. The two- to fourfold increase in the MIC of gemifloxacin in genetically defined grlBA mutants and the twofold increase in a single gyrA mutant, supported by the low frequency of selection of resistant mutants at twice the MIC (7.4 x 10(-11) to 1.1 x 10(-10)), suggested similar targeting of the two enzymes by gemifloxacin. Dual mutations in both gyrase and topoisomerase IV caused a 64- to 128-fold increase in the MIC of gemifloxacin, similar to that seen with ciprofloxacin. Gemifloxacin also had similar activity in vitro against topoisomerase IV and gyrase purified from S. aureus (50% inhibitory concentrations of 0.25 and 0.31 micro g/ml, respectively). This activity was 10- to 20-fold higher than that of ciprofloxacin for topoisomerase IV and 33-fold higher than that for gyrase. In contrast to the in vitro findings, only topoisomerase IV mutants were selected in first-step mutants. Overexpression of the NorA efflux pump had a minimal effect on resistance to gemifloxacin, and a mutation in the promoter region of the gene for NorA was selected only in the sixth step of serial selection of mutants. Our data show that although gemifloxacin targets purified topoisomerase IV and gyrase similarly in vitro, topoisomerase IV is the preferred target in the bacteria. Selection of novel resistance mutations in grlA requires further expansion of quinolone-resistance-determining regions, and their study may provide increased insight into enzyme-quinolone interactions.
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PMID:Topoisomerase targeting with and resistance to gemifloxacin in Staphylococcus aureus. 1249 2


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