Effectiveness of Preventive Therapy for Persons Exposed at Home to Drug-Resistant Tuberculosis,Karachi, Pakistan

In Karachi, Pakistan, a South Asian megacity with a high prevalence of tuberculosis (TB) and low HIV prevalence, we assessed the effectiveness of fluoroquinolone-based preventive therapy for drug-resistant (DR) TB exposure. During February 2016–March 2017, high-risk household contacts of DR TB patients began a 6-month course of preventive therapy with a fluoroquinolone-based, 2-drug regimen. We assessed effectiveness in this cohort by comparing the rate and risk for TB disease over 2 years to the rates and risks reported in the literature. Of 172 participants, TB occurred in 2 persons over 336 person-years of observation. TB disease incidence rate observed in the cohort was 6.0/1,000 person-years. The incidence rate ratio ranged from 0.29 (95% CI 0.04–1.3) to 0.50 (95% CI 0.06–2.8), with a pooled estimate of 0.35 (95% CI 0.14–0.87). Overall, fluoroquinolone-based preventive therapy for DR TB exposure reduced risk for TB disease by 65%.     

Mechanisms of Pefloxacin-Induced Pain

In electrophysiological and behavioral experiments on rats we studied the effects of pefloxacin, a member of fluoroquinolone family, on the nociceptive system. Intraperitoneal injection of pefloxacin (80 mg/kg) decreased the thresholds of nociceptive response to noxious stimulation in the hot-plate test. In addition, it decreased the threshold of the late component of nociceptive flexor reflex. Intrathecal application of pefloxacin in a dose of 20 microg provoked allodynia, while the higher dose of 400 microg induced behavioral pattern characteristic of central pain syndrome. It was hypothesized that pain induced by pefloxacin results from disturbances in GABAergic inhibition in the central subdivisions of the nociceptive system.     

氟喹诺酮类药物的进展与临床应用评价

目的 :介绍第 4代氟喹诺酮类药物的抗菌作用特点和临床应用的进展历程。方法 :采用中、外文献综述方法。结果 :新 1代氟氟喹诺酮类药物的抗菌谱更趋广泛 ,对需氧菌和厌氧菌的抗菌能力较前 3代的同类药物均有所增强。结论 :第 4代氟喹诺酮类药物的抗菌谱广、杀菌力强、吸收快、体内分布广、血浆半衰期较长 ,有望在临床上广泛用于各种感染 ,但其所致的心脏和肝脏的毒性仍值得警惕     

Achilles tendinopathy after treatment with fluoroquinolone

Fluoroquinolone antibiotic therapy is a recognized but poorly understood cause for Achilles tendinopathy. We report here a patient who developed bilateral partial Achilles tendon tears as a result of fluoroquinolone therapy. Ultrasound and MRI were both useful in identifying and distinguishing between Achilles tendinosis and tendon rupture. The current published literature on this problem was also reviewed.     

普卢利沙星的合成

目的改进氟喹诺酮类抗菌药普卢利沙星的合成工艺.方法以3,4-二氟苯胺为起始原料经过8步反应制得关键中间体(±)6,7-二氟-1-甲基-4-氧代-1H,4H-[1,3]硫氮杂环丁烷并[3,2-a]喹啉-3-羧酸乙酯(10),化合物10经氢氧化钾水解,然后与4-(1-哌嗪基)甲基-5-甲基-2-氧代-1,3-二氧杂环戊烯(15)反应合成普卢利沙星.结果与结论合成的普卢利沙星的结构经元素分析和1H-NMR确证,总收率为18.6%.     

离子液体促进氟罗沙星的合成

2,3,4-三氟苯胺经与EMME缩合、环合、氟乙基化、与N-甲基哌嗪缩合和水解反应制得氟罗沙星,前4步反应可被离子溶剂1-丁基-3-甲基咪唑六氟磷酸盐促进,如环合反应温度由300℃降至200℃,总收率61%.     

6,7-二氟-4-羟基-2-甲氧甲硫基-3-喹啉羧酸乙酯的合成

3,4-二氟苯胺在三乙胺存在下与二硫化碳生成芳基取代的二硫代氨基甲酸后与氯甲酸乙酯反应得到3,4-二氟苯基异硫氰酸酯,先后与由丙二酸二乙酯在无机碱中成的盐和氯甲基甲醚反应后加热环合,得到氟喹诺酮类抗菌剂普卢利沙星的中间体6,7-二氟-4-羟基-2-甲氧甲硫基-3-喹啉羧酸乙酯,总收率85.7%.     

氟喹诺酮类药物对嗜麦芽窄食单胞菌主动外排泵表型特征研究

目的 研究氟喹诺酮类药物(FQNS)对嗜麦芽窄食单胞菌的抗菌活性及氰氯苯腙(CCCP)对其主动外排泵表型特征的影响。方法　用琼脂二倍稀释法测定FQNS的最低抑菌浓度(MIC),测定CCCP对FQNS的MIC值的影响。结果　111株嗜麦芽窄食单胞菌对FQNS耐药率较低,尤以新型FQNS抗菌活性较高,其中抗菌活性由高到低依次是加替沙星、司帕沙星、左氧氟沙星和环丙沙星。主动外排泵抑制剂CCCP在体外能增强FQNS抗菌活性,主动外排机制即存在于FQNS耐药菌株,也存在于FQNS敏感菌株。但是CCCP对4种FQNS耐药菌株影响更大。结论　主动外排泵抑制剂在体外能降低FQNS对嗜麦芽窄食单胞菌的MIC,若能保证安全性,可能成为临床克服细菌耐药性的一种方法。     

Doxorubicin,Paclitaxel and Gemcitabine: a Phase I Study of a New Sequential Treatment in Stage III B - IV Breast Cancer

Abstract

Based on the synergistic interactions of the sequence doxorubicin-paclitaxelgemcitabine obtained in our preclinical study, a Phase I trial was conducted to evaluate the feasibility of this new sequence in breast cancer. Patients with stage IIIBIV breast cancer received doxorubicin on day 1, paclitaxel on day 2 and gemcitabine on day 6 and 13 (steps IIa, III and V) in cohorts of 3 patients. From March 1999 to December 2000, 9 patients were treated. The most important toxicity was hematological. The maximum tolerated dose was reached at the second level because dose-limiting toxicity occurred in 3 patients. Non hematological toxicities were alopecia, diarrhea, asthenia, nausea, mucositis, paresthesia and myalgia. A Phase II trial is ongoing to further investigate the activity of this new sequential treatment with doxorubicin (50 mg/m² day 1), paclitaxel (160 mg/m² day 2) and gemcitabine (800 mg/m² day 6) in advanced breast cancer.     

INAUGURAL ARTICLE by a Recently Elected Academy Member:Crystal structure and stability of gyrase–fluoroquinolone cleaved complexes from Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) infects one-third of the world’s population and in 2013 accounted for 1.5 million deaths. Fluoroquinolone antibacterials, which target DNA gyrase, are critical agents used to halt the progression from multidrug-resistant tuberculosis to extensively resistant disease; however, fluoroquinolone resistance is emerging and new ways to bypass resistance are required. To better explain known differences in fluoroquinolone action, the crystal structures of the WT Mtb DNA gyrase cleavage core and a fluoroquinolone-sensitized mutant were determined in complex with DNA and five fluoroquinolones. The structures, ranging from 2.4- to 2.6-Å resolution, show that the intrinsically low susceptibility of Mtb to fluoroquinolones correlates with a reduction in contacts to the water shell of an associated magnesium ion, which bridges fluoroquinolone–gyrase interactions. Surprisingly, the structural data revealed few differences in fluoroquinolone–enzyme contacts from drugs that have very different activities against Mtb. By contrast, a stability assay using purified components showed a clear relationship between ternary complex reversibility and inhibitory activities reported with cultured cells. Collectively, our data indicate that the stability of fluoroquinolone/DNA interactions is a major determinant of fluoroquinolone activity and that moieties that have been appended to the C7 position of different quinolone scaffolds do not take advantage of specific contacts that might be made with the enzyme. These concepts point to new approaches for developing quinolone-class compounds that have increased potency against Mtb and the ability to overcome resistance.The causative agent of tuberculosis (TB), Mycobacterium tuberculosis (Mtb), is one of the most important pathogens of humans, second only to the HIV in the number of deaths caused annually (1). Mtb is estimated to latently infect one-third of the world’s population (2), thereby also creating a huge reservoir for future disease. Particularly problematic are cases of multidrug-resistant (MDR)-TB, which is defined as resistance to two primary anti-TB drugs, rifampicin and isoniazid. MDR-TB now represents 3.5% of new TB cases; of these, 9% are classified as extensively drug-resistant (XDR)-TB (1), which is defined as MDR-TB with additional resistance to any fluoroquinolone and one injectable second-line drug (3). TB isolates are also being recovered that are totally drug-resistant (3–5). Thus, controlling TB, in particular drug-resistant TB, is a major health problem.Fluoroquinolones are one of the most successful classes of drugs against bacterial pathogens, accounting for 24% of the $10 billion antibiotic market (6). Fluoroquinolones are also currently receiving considerable attention in the treatment of TB, with two new C8-methoxy derivatives, moxifloxacin and gatifloxacin, currently under evaluation as promising first-line therapeutics (7–10). These compounds have been used to restrict the development of XDR-TB from MDR-TB; however, emerging resistance threatens both first-line and second-line use (11). The widespread testing of fluoroquinolones against TB has revealed considerable variation in efficacy of different drug variants against Mtb. For example, ciprofloxacin is only marginally active, and its early use with Mtb was halted in favor of ofloxacin and levofloxacin (7). These two agents are now proving to be less effective than moxifloxacin and gatifloxacin (7, 10); however, the newest two compounds also exhibit some nonideality. For example, gatifloxacin can elicit side effects such as hypo/hyperglycemia (12), whereas moxifloxacin has potential cardiovascular risks (13). Although recent clinical trials that have included fluoroquinolones as part of an alternative drug regimen have faltered (14), there are prospects for other nonfluoroquinolone molecules to make an impact on the treatment of MDR- and XDR-TB (15, 16). Moreover, a promising recent trial that uses moxifloxacin as part of a three-drug regimen together with pretomanid and pyrazinamide reports superior bactericidal activity against TB and MDR-TB versus current regimens (17). These new data make it clear that new quinolone-class agents, which are also capable of circumventing known resistance mutations, might be useful therapeutic agents in the treatment of TB.Progress is presently being made toward developing new fluoroquinolone derivatives. For example, a methoxy group at fluoroquinolone position C8 (Fig. 1A) increases activity against mycobacteria, particularly resistant mutants (18–20). Indeed, moxifloxacin, along with a more active C8-methyl derivative, retains high inhibitory activity against purified Mtb gyrase even when the enzyme contains commonly acquired fluoroquinolone-resistance substitutions [as described in the accompanying paper by Aldred et al. (21)]. In another example, quinazolinediones (diones) have been shown to have an ability to bypass existing resistance within mycobacteria and other bacterial species (20, 22–24). Thus, there still exist opportunities to design more effective quinolone-class molecules for treatment of TB.Open in a separate windowFig. 1.DNA cleavage by Mtb gyrase induced by fluoroquinolones. (A) Fluoroquinolones tested in this study. The constant quinolone core of each drug is highlighted in orange, numbered as shown around C8-Me-moxifloxacin. (B) DNA cleavage assays with full-length Mtb gyrase, using WT (upper gels) and a GyrA A90S (lower gels) sensitizing mutant. Each fluoroquinolone is titrated against a constant amount of protein (125 nM) and supercoiled (SC) plasmid DNA substrate (12.5 nM). The “no protein” control shows the supercoiled substrate DNA, along with a nicked (N) and linear (L) control lanes. Each gel is representative of triplicate data. (C) Graphical analysis of data in B. The relative amount of DNA cleavage is plotted as an increase in linear product (obtained by densitometry) compared with the zero drug control as a function of drug concentration. (Left) WT. (Right) A90S. Data points and error bars represent the mean and SD of triplicate data, respectively.DNA gyrase is a heterotetrameric (GyrA₂GyrB₂) enzyme that transiently catalyzes dsDNA breaks as it negatively supercoils DNA. Fluoroquinolones prevent the resealing of the ds breaks that normally follows DNA strand passage (25), generating persistent, covalent enzyme–DNA adducts called cleaved complexes. Cleaved-complex formation, which is reversible, blocks bacterial growth; at elevated fluoroquinolone concentrations, release of DNA breaks from the complexes leads to chromosome fragmentation and cell death (26). Although numerous crystallographic studies have defined the primary binding site of fluoroquinolones against gyrase (and against topoisomerase IV, a gyrase paralog) (27–30), there has been debate as to whether fluoroquinolones use a magnesium ion to bridge their interaction with the enzyme (28, 29). Resolving this question is important, because the intrinsic resistance of certain species of gyrase to quinolones (e.g., Mtb) has been proposed to result from natural sequence variation that leads to the loss of a magnesium-ion “bridge” formed between the drug and enzyme (31–33). At the same time, there currently exists no clear chemical explanation as to why certain fluoroquinolone derivatives act with different efficacies against Mtb gyrase.To better understand such questions, we carried out a structural and biochemical analysis of Mtb gyrase in the presence of a panel of four different, clinically used fluoroquinolones (ciprofloxacin, levofloxacin, gatifloxacin, and moxifloxacin) and one new fluoroquinolone derivative (C8-Me-moxifloxacin). X-ray crystallography revealed that Mtb gyrase indeed makes an intrinsically low number of interactions with a magnesium ion that accompanies fluoroquinolone binding, and that the introduction of a drug-sensitizing mutation (GyrA A90S) restores interactions seen in nonresistant gyrase homologs. In vitro, we find that C8-Me-moxifloxacin and moxifloxacin are most effective at promoting cleaved complex formation and inhibiting DNA supercoiling by Mtb gyrase, followed by gatifloxacin, and then ciprofloxacin and levofloxacin; however, crystal structures of the DNA-binding-and-cleavage core of Mtb gyrase with both DNA and drug surprisingly failed to reveal any substantial differences in the contacts formed between the protein and different drugs. Further biochemical investigations using an assay that monitors the stability of preformed cleaved complexes largely corroborated the rank order of inhibition seen in DNA cleavage experiments and moreover resulted in drug efficacy trends that closely accord with clinical effectiveness. Collectively, our data explain why Mtb gyrase is naturally quinolone-resistant and show that the relative activities of existing panels of anti-TB quinolone therapeutics are heavily influenced by base-stacking interactions and have yet to take advantage of direct gyrase contacts to maximize therapeutic potential.