新一代红霉素衍生物及其构效关系研究进展

综述国内外关于十四元大环内酯类抗生素红霉素的结构修饰和所得衍生物抗菌活性的研究近况,介绍了若干个有较好抗菌活性的先导化合物。大环内酯类抗生素广泛应用于临床的同时,细菌对其产生耐药性的问题也愈发突出。以酮内酯为代表的新一代大环内酯类红霉素衍生物具有良好的药动学性质,且对耐药菌有很好的活性,成为近年来大环内酯类抗生素研发的重点。     

抗菌活性红霉素衍生物研究进展

目的综述具有抗菌活性红霉素衍生物的研究进展。方法依据国内外近期公开发表的53篇文献,对具有抗菌活性红霉素衍生物的研究进展进行分类、归纳与总结。结果长期以来,红霉素及其衍生物作为抗菌药物被广泛使用。20世纪80年代后期问世的第二代大环内酯类抗生素,具有药代动力学性质好、毒性及不良反应小的特点,现已广泛应用于临床。目前,红霉素化学修饰研究的主要目标是研制对大环内酯耐药菌有效的第三代大环内酯类药物。结论利用具有抗菌活性红霉素衍生物研制开发新药,已逐步成为红霉素衍生物研究的重要内容,呈现良好的发展势头。     

新红霉素衍生物结构修饰与抗菌活性研究进展

综述了近年来红霉素衍生物的结构修饰与抗菌活性关系研究的最新进展,结果显示,该红霉素类衍生物新药品种具有组织和血药浓度高,半衰期长和抗耐药菌等药代动力学新特性。     

4＂-0-取代红霉素衍生物的研究进展

随着大环内酯类抗生素广泛应用于临床,细菌耐药性的问题日趋严重,因此,开发对耐药菌有效的第3代红霉素衍生物成为目前的研究热点。综述红霉素分子上克拉定糖4＂位羟基结构修饰的研究进展,并介绍了若干个对耐药菌具有优良抗菌活性的新型4＂-0-取代红霉素衍生物。     

非抗菌活性红霉素衍生物研究进展

目的综述非抗菌活性红霉素衍生物的研究进展。方法依据国内外近期公开发表的40篇文献,对非抗菌活性红霉素衍生物的研究进展进行分类、归纳与总结。结果长期以来,红霉素及其衍生物作为抗菌药物被广泛使用。在临床实践中人们发现,该类化合物还具有一些新的生物活性,例如促进消化道运动、抗炎/免疫调节、抗寄生虫、抗肿瘤、拮抗黄体生成素释放激素、以及抑制磷酸二酯酶-3等活性。为提高新活性降低其抗菌作用,已经设计、合成了多种类型的新结构红霉素衍生物。结论利用红霉素衍生物的新活性研制、开发新药已经成为研究热点。     

新活性红霉素衍生物的研究进展

目的综述新活性红霉素衍生物的研究进展。方法依据国内外近期公开发表的30篇文献,对新活性红霉素衍生物的研究进展进行分类、归纳与总结。结果长期以来,红霉素及其衍生物作为抗菌药物被广泛使用。临床与实验数据显示,该类化合物还具有一些新的生物活性,例如促进消化道运动活性、抗炎与免疫调节活性、拮抗黄体生成素释放激素活性以及抑制磷酸二酯酶-3活性等。在提高红霉素的新活性并降低其抗菌作用的研究中,已设计、合成了多种类型的新结构的红霉素衍生物。结论利用红霉素衍生物的新活性研制、开发新药,已逐步成为红霉素衍生物研究的重要内容,呈现良好的发展势头。     

1-O-乙酰基大花旋覆花内酯及其衍生物的研究进展

1-O-乙酰基大花旋覆花内酯为倍半萜内酯类化合物,是中药旋覆花的活性成分之一,具有抗炎、抗肿瘤、抗菌等多种药理作用,近年来1-O-乙酰基大花旋覆花内酯类化合物的药理作用及其机制以及结构修饰得以较为深入的研究。此外,以该天然产物为原料,通过化学反应进行结构修饰的衍生物在细胞毒活性方面研究也取得了新的进展。本文综述了1-O-乙酰基大花旋覆花内酯及其衍生物的提取制备、含量测定、药理活性、作用机制和构效关系。     

新型红霉素类大环内酯衍生物的合成及抗菌活性研究

目的 对大环内酯类抗生素进行结构改造，拟筛选获得抗菌活性更高的候选药物；方法 分别对氟红霉素和克拉霉素的C-3及C-11，C-12进行结构修饰，设计合成了17个大环内酯类衍生物，采用微量稀释法测定了衍生物的最低抑菌浓度(MIC)。结果 12d、12e和12f对B. subtilis 168和 S. aureus USA 300表现出了较好的抗菌活性；结论 通过结构改造获得了抗菌活性增强的大环内酯类衍生物，进一步探讨了大环内酯类抗生素的构效关系，为后续研究提供了参考。     

1-O-乙酰基大花旋覆花内酯及其衍生物的研究进展

1-O-乙酰基大花旋覆花内酯为倍半萜内酯类化合物,是中药旋覆花的活性成分之一,具有抗炎、抗肿瘤、抗菌等多种药理作用,近年来1-O-乙酰基大花旋覆花内酯类化合物的药理作用及其机制以及结构修饰得以较为深入的研究.此外,以该天然产物为原料,通过化学反应进行结构修饰的衍生物在细胞毒活性方面研究也取得了新的进展.本文综述了1-O-乙酰基大花旋覆花内酯及其衍生物的提取制备、含量测定、药理活性、作用机制和构效关系.     

红霉素衍生物抗菌活性构效关系研究进展

为解决抗生素的耐药性问题，近年来在红霉素化学结构修饰方面开展了大量的研究，并发现了诸如酮内酯、酰内酯、双环内酯等多种具有良好抗耐药菌活性的新型大环内酯类化合物。该文对红霉素衍生物抗菌活性研究成果做一概括，并对构效关系研究的某些重要结论加以探讨。     

Macrolide resistance.

The macrolides have evolved through four chemical generations since erythromycin became available for clinical use in 1952. The first generation, the 14-membered ring macrolide erythromycin, induced resistance and was replaced by the second generation 16-membered ring macrolides which did not. The inability to induce came at the price of mutation, in the pathogenic target strain, to constitutive expression of resistance. A third generation of macrolides improved the acid-stability, and therefore the pharmacokinetics of erythromycin, extending the clinical use of macrolides to Helicobacter pylori and Mycobacterium tuberculosis. Improved pharmacokinetics resulted in the selection of intrinsically resistant mutant strains with rRNA structural alterations. Expression of resistance in these strains was unexpected, explainable by low rRNA gene copy number which made resistance dominant. A fourth generation of macrolides, the 14-membered ring ketolides are the most recent development. Members of this generation are reported to be effective against inducibly resistant strains, and ketolide resistant strains have not yet been reported. In this review we discuss details of the ways in which bacteria have become resistant to the first three generations of macrolides, both with respect to their biochemistry, and the genetic mechanisms by which their expression is regulated.     

Resistance to macrolides in Group A streptococci from the European section of Turkey: genetic and phenotypic characterization

The aim of this study was to determine the susceptibilities to macrolides of Group A streptococcal isolates from the European section of Turkey. In the case of resistant isolates, the patterns and genetic mechanisms of erythromycin resistance were studied. Seven (2.7%) of the 260 isolates were resistant to erythromycin. Four of them showed the M phenotype and harboured mefA genes whereas three isolates showed the inducible macrolide, lincosamide and streptogramin B resistance phenotype and harboured ermTR genes. In the European section of Turkey, the current resistance rate of Group A streptococci to macrolides remains low.     

The in vitro activity of some 14-, 15- and 16- membered macrolides against Staphylococcus spp., Legionella spp., Mycoplasma spp. and Ureaplasma urealyticum.

Erythromycin is a macrolide antimicrobial chemically comprised of a 14-membered lactone ring substituted with a neutral (cladinose) and an amino (desosamine) sugar. Recently, a number of new macrolide molecules have been identified containing either 14-, 15- or 16-membered substituted lactone rings. In this study the authors have determined the in vitro activity of roxithromycin and clarithromycin (both 14-membered macrolides), azithromycin (a 15-membered macrolide or azalide) and midecamycin acetate (a 16-membered macrolide) against clinical isolates of Staphylococcus spp., (including methicillin-susceptible and -resistant isolates), Legionella spp., Mycoplasma spp. and Ureaplasma urealyticum. Minimum inhibitory concentrations of the macrolides for the clinical isolates of Staphylococcus spp. examined were widely distributed. However, midecamycin acetate retained activity against those isolates of Staphylococcus spp. exhibiting inducible resistance to erythromycin and the other macrolides tested. Isolates characterised by constitutive resistance to erythromycin were also resistant to midecamycin acetate. All of the macrolides were very active against Legionella spp., with clarithromycin demonstrating the greatest potency (MIC range: less than or equal to 0.03-0.06 mg/l). Isolates of Mycoplasma pneumoniae and Ureaplasma urealyticum were susceptible to all of the macrolides tested. However, erythromycin, roxithromycin, clarithromycin and azithromycin were poorly active against isolates of Mycoplasma hominis. By contrast, the same isolates were susceptible (MIC range: 0.008-0.12 mg/l) to midecamycin acetate.     

广东东莞地区葡萄球菌对红霉素和克林霉素诱导耐药性的调查

目的了解广东东莞地区葡萄球菌大环内酯类药物的耐药情况及耐药机制。方法按美国临床实验室标准化研究所（CLSI）推荐的纸片扩散法测定葡萄球菌对红霉素及克林霉素的耐药性，并以D试验测定红霉索对克林霉素的诱导耐药表型。结果719株葡萄球菌红霉素及克林霉素同时耐药为45．5％，D试验阳性占所检的葡萄球菌的18.6％。在单一纸片红霉素耐药而克林霉素敏感的葡萄球菌中，D试验阳性即对克林霉索具有诱导型耐药的为50．8％。结论开展D试验检测葡萄球菌中红霉素对克林霉素的诱导耐药性可帮助临床医生正确选用大环内酯类、林可霉素类抗生素。     

The ketolides: a critical review

Ketolides are a new class of macrolides designed particularly to combat respiratory tract pathogens that have acquired resistance to macrolides. The ketolides are semi-synthetic derivatives of the 14-membered macrolide erythromycin A, and retain the erythromycin macrolactone ring structure as well as the D-desosamine sugar attached at position 5. The defining characteristic of the ketolides is the removal of the neutral sugar, L-cladinose from the 3 position of the ring and the subsequent oxidation of the 3-hydroxyl to a 3-keto functional group. The ketolides presently under development additionally contain an 11, 12 cyclic carbamate linkage in place of the two hydroxyl groups of erythromycin A and an arylalkyl or an arylallyl chain, imparting in vitro activity equal to or better than the newer macrolides. Telithromycin is the first member of this new class to be approved for clinical use, while ABT-773 is presently in phase III of development. Ketolides have a mechanism of action very similar to erythromycin A from which they have been derived. They potently inhibit protein synthesis by interacting close to the peptidyl transferase site of the bacterial 50S ribosomal subunit. Ketolides bind to ribosomes with higher affinity than macrolides. The ketolides exhibit good activity against Gram-positive aerobes and some Gram-negative aerobes, and have excellent activity against drug-resistant Streptococcus pneumoniae, including macrolide-resistant (mefA and ermB strains of S. pneumoniae). Ketolides such as telithromycin display excellent pharmacokinetics allowing once daily dose administration and extensive tissue distribution relative to serum. Evidence suggests the ketolides are primarily metabolised in the liver and that elimination is by a combination of biliary, hepatic and urinary excretion. Pharmacodynamically, ketolides display an element of concentration dependent killing unlike macrolides which are considered time dependent killers. Clinical trial data are only available for telithromycin and have focused on respiratory infections including community-acquired pneumonia, acute exacerbations of chronic bronchitis, sinusitis and streptococcal pharyngitis. Bacteriological and clinical cure rates have been similar to comparators. Limited data suggest very good eradication of macrolide-resistant and penicillin-resistant S. pneumoniae. As a class, the macrolides are well tolerated and can be used safely. Limited clinical trial data suggest that ketolides have similar safety profiles to the newer macrolides. Telithromycin interacts with the cytochrome P450 enzyme system (specifically CYP 3A4) in a reversible fashion and limited clinically significant drug interactions occur. In summary, clinical trials support the clinical efficacy of the ketolides in upper and lower respiratory tract infections caused by typical and atypical pathogens including strains resistant to penicillins and macrolides. Considerations such as local epidemiology, patterns of resistance and ketolide adverse effects, drug interactions and cost relative to existing agents will define the role of these agents. The addition of the ketolides in the era of antibacterial resistance provides clinicians with more options in the treatment of respiratory infections.     

Review of macrolides and ketolides: focus on respiratory tract infections

The first macrolide, erythromycin A, demonstrated broad-spectrum antimicrobial activity and was used primarily for respiratory and skin and soft tissue infections. Newer 14-, 15- and 16-membered ring macrolides such as clarithromycin and the azalide, azithromycin, have been developed to address the limitations of erythromycin. The main structural component of the macrolides is a large lactone ring that varies in size from 12 to 16 atoms. A new group of 14-membered macrolides known as the ketolides have recently been developed which have a 3-keto in place of the L-cladinose moiety. Macrolides reversibly bind to the 23S rRNA and thus, inhibit protein synthesis by blocking elongation. The ketolides have also been reported to bind to 23S rRNA and their mechanism of action is similar to that of macrolides. Macrolide resistance mechanisms include target site alteration, alteration in antibiotic transport and modification of the antibiotic. The macrolides and ketolides exhibit good activity against gram-positive aerobes and some gram-negative aerobes. Ketolides have excellent activity versus macrolide-resistant Streptococcus spp. Including mefA and ermB producing Streptococcus pneumoniae. The newer macrolides, such as azithromycin and clarithromycin, and the ketolides exhibit greater activity against Haemophilus influenzae than erythromycin. The bioavailability of macrolides ranges from 25 to 85%, with corresponding serum concentrations ranging from 0.4 to 12 mg/L and area under the concentration-time curves from 3 to 115 mg/L x h. Half-lives range from short for erythromycin to medium for clarithromycin, roxithromycin and ketolides, to very long for dirithromycin and azithromycin. All of these agents display large volumes of distribution with excellent uptake into respiratory tissues and fluids relative to serum. The majority of the agents are hepatically metabolised and excretion in the urine is limited, with the exception of clarithromycin. Clinical trials involving the macrolides are available for various respiratory infections. In general, macrolides are the preferred treatment for community-acquired pneumonia and alternative treatment for other respiratory infections. These agents are frequently used in patients with penicillin allergies. The macrolides are well-tolerated agents. Macrolides are divided into 3 groups for likely occurrence of drug-drug interactions: group 1 (e.g. erythromycin) are frequently involved, group 2 (e.g. clarithromycin, roxithromycin) are less commonly involved, whereas drug interactions have not been described for group 3 (e.g. azithromycin, dirithromycin). Few pharmacoeconomic studies involving macrolides are presently available. The ketolides are being developed in an attempt to address the increasingly prevalent problems of macrolide-resistant and multiresistant organisms.     

New research in macrolides and ketolides since 1997

Macrolide and ketolide antibacterials remain a very dynamically active group. To overcome erythromycin A resistance within Gram-positive cocci and bacteria, novel compounds have been semi-synthesised, such as ketolides and C-4' carbamate erythromycylamine derivatives. The continual efforts of those studying macrolides have led to molecular level investigations into the mechanism of action of these antibacterials. Among all novel derivatives, only telithromycin and AB-773 are currently under development. No real novel developments have been seen with the 15- and 16-membered ring macrolides, however, research is also continuing in this area. This review is an update of our knowledge in the field of macrolides.     

Evaluation of the degree of susceptibility of Streptococcus pyogenes erythromycin-resistant strains to rokitamycin (a 16-membered macrolide) using the Epsilometer test

Routine hospital screening of the resistance of Streptococcus pyogenes to macrolides is usually done using the erythromycin, clarithromycin or azithromycin disk diffusion technique. When a strain is found to be resistant to one of these macrolides, it is generally assumed to be resistant to the whole class. However this approach gives only partial qualitative information because S. pyogenes strains with inducible and M phenotype resistance are still susceptible to 16-membered ring macrolides such as rokitamycin. Seventy-four erythromycin-resistant (22 inducible and 52 M phenotype) strains of S. pyogenes were tested for their susceptibility to rokitamycin and clindamycin (control) by means of the agar disk diffusion test and the results were compared with those obtained using the Epsilometer test, a quantitative technique for measuring bacterial susceptibility and minimal inhibitory concentrations (MIC). Epsilometer testing of erythromycin in comparison with rokitamycin is useful for measuring the real degree of susceptibility of macrolide-resistant strains quickly and simply. This is important because strains with the same disk diffusion diameter do not necessarily have the same MIC, but a scattered distribution of susceptibility.     

772株葡萄球菌中红霉素对克林霉素诱导耐药检测

目的:了解葡萄球菌对红霉素及克林霉素的耐药性,结合药敏试验结果,为临床合理选择抗生素提供可靠依据。方法:按照2004年版美国临床实验室标准化委员会(NCCLs)推荐的纸片扩散方法,测定并判读葡萄球菌对红霉素和克林霉素的耐药性,并以D-试验测定红霉素对克林霉素的诱导耐药表型。结果:红霉素和克林霉素同时耐药在耐甲氧西林葡萄球菌(MRSA)和甲氧西林敏感型葡萄球菌(MSSA)中分别占45.50%(192/422)和55.14%(193/350);对红霉素耐药而克林霉素敏感的MRSA和MSSA中,D-试验阳性(即对克林霉素具有诱导耐药性者)分别为69.72%和30.58%。D-试验阳性占所测葡萄球菌的24.48%,占对红霉素耐药而克林霉素敏感菌株的30.58%。结论:红霉素诱导克林霉素发生耐药应引起关注,开展药敏试验及D-试验,检测葡萄球菌中红霉素对克林霉素诱导性耐药,可指导临床医师合理选用大环内酯类、克林霉素类抗菌药物。