In-vitro activity of ceftriaxone combined with newer agents against MRSA

In this study, in vitro synergism in combinations of agents as ceftriaxone/dalbavancin, ceftriaxone/linezolid and ceftriaxone/daptomycin against MRSA strains were investigated. Thirty clinical MRSA strains were tested. The minimum inhibitory concentrations of all antibiotics were determined using reference broth microdilution method. In-vitro activities of antibiotics combined against the strains were tested using two-dimensional checkerboard microdilution method. Results were interpreted as follows: synergy = FICI ≤0.5; ‘no interaction’ effect = FICI ?0.5-≤4; antagonism = FICI ?4. The MIC₅₀, MIC₉₀ and MIC_range of ceftriaxone, daptomycin, dalbavancin and linezolid were found as 128, 1024 and 16-2048 mg/L; 1, 1 and 0.5–1 mg/L; 0.12, 0.12 and 0.03–0.12 mg/L; and 1, 2 and 1–2 mg/L, respectively. Our results showed that the frequency of synergistic effects (FICI: ≤0.5) of three combinations were all at the same rate of 77% (23/30). No in vitro antagonism (FICI >4) was observed.     

Antimicrobial activity of dalbavancin tested against Gram-positive clinical isolates from Latin American medical centres

The activity of dalbavancin, a new semi-synthetic lipoglycopeptide antibiotic, was evaluated in comparison with other antibacterial agents against 1229 Gram-positive organisms collected from medical centres in Latin America. Dalbavancin was the most potent compound tested against isolates of Staphylococcus aureus (MIC(50), 0.06 mg/L) and coagulase-negative staphylococci (MIC(50), 0.03 mg/L), independently of methicillin susceptibility. Dalbavancin inhibited all Streptococcus pneumoniae isolates at Dalbavancin also demonstrated excellent activity against beta-haemolytic (MIC(50), /= 8 mg/L. Dalbavancin exhibited excellent activity against isolates of Corynebacterium spp. and Listeria spp. Dalbavancin may provide an important therapeutic option for Gram-positive infections, excluding those caused by enterococci with VanA-type resistance.     

Update of dalbavancin spectrum and potency in the USA: report from the SENTRY Antimicrobial Surveillance Program (2011)

Dalbavancin (DAL) is an investigational lipoglycopeptide with a prolonged serum half-life allowing once weekly dosing. DAL potency was assessed in the 2011 SENTRY Antimicrobial Surveillance Program among 1555 isolates sampled from all 9 US Census regions. Monitored Gram-positive cocci included Staphylococcus aureus (SA; 1,036/50.4% MRSA), coagulase-negative staphylococci (CoNS; 115), Enterococcus faecalis (25), E. faecium (31), Streptococcus pyogenes (155), Streptococcus agalactiae (153), and viridans group streptococci (VGS; 40). All susceptibility (S) testing used Clinical and Laboratory Standards Institute reference broth microdilution methods and interpretations. DAL (MIC_50/90, 0.06/0.06 μg/mL) was 8- and 16-fold more active than daptomycin (DAP) and vancomycin (VAN), respectively against SA, with MSSA and MRSA having the same MIC₉₀ results. CoNS was slightly more DAL-S (MIC₅₀, ≤0.03μg/mL). The highest staphylococcal DAL MIC was only 0.25 μg/mL. β-Haemolytic streptococci (βHS) and VGS had DAL MIC results ranging from ≤0.03 to 0.25 μg/mL (MIC₉₀, 0.06–0.12 μg/mL), and only enterococci showed elevated DAL MIC results. VanA phenotype–resistant E. faecalis or E. faecium had DAL MIC values at ≥1 μg/mL; VanB strains were DAL-S (MIC, ≤0.25 μg/mL). All cited DAL quantitative values were consistent with earlier surveillance data (2006–2009), without evidence of MIC creep. In conclusion, year 2011 SENTRY Program data for DAL documents sustained potent activity against SA, CoNS, βHS, VGS, and VAN-S enterococci, which averaged 4- to 32-fold greater than VAN, DAP, or linezolid.     

A40926高产菌株的选育及发酵工艺优化

目的通过菌种选育与发酵工艺优化,提高A40926发酵产量。方法本文采用紫外线和亚硝基胍两种方法诱变,结合抗生素抗性筛选方法,对A40926的产生菌Nonomuraea sp.SIPI-H3020进行诱变选育,并通过工艺优化提高发酵产量。结果筛选得到一株高产突变株Nonomuraea sp.SIPI-H5972,其发酵效价比出发菌株提高了257%。在优化的摇瓶发酵工艺下,突变株SIPI-H5972的发酵效价达到990μg/m L,又提高了153%。通过补料工艺优化,在50L发酵罐中发酵效价为1223μg/m L,比摇瓶发酵提高了23.5%。结论紫外线和亚硝基胍诱变并结合抗生素抗性筛选对提高A40926发酵单位效果明显,补料工艺可以显著提高其产量。     

第二代糖肽类抗生素的研究进展

随着细菌耐药的不断升级，耐万古霉素肠球菌、高度耐糖肽类抗生素的金葡菌的出现，给临床抗感染治疗带来极大困难。开发新型糖肽类抗生素刻不容缓。人们对万古霉素等天然糖肽类抗生素进行化学修饰，得到了一系列有价值的衍生物，其中oritavancin、dalbavancin和telavancin已进入Ⅲ期临床和新药注册。本文对第二代糖肽类抗生素的结构特征、药效学与药动学特征以及临床应用作一综述。