The effects of oxygen on β-lactam biosynthesis by alginate entrapped streptomyces clavuligerus

The physiology of Streptomyces clavuligerus has been studied by investigating oxygen uptake and β-lactam (clavulanic acid) production by free and alginate entrapped cells. The specific oxygen uptake rate of cells entrapped in strontium or calcium alginate was only about 35% of the rate in free cells. This reduction in oxygen uptake was due to reduced internal diffusion of oxygen; in addition calcium, barium and strontium ions could also cause oxygen uptake in free cells to be inhibited. Measurements of the deformation of individual gel beads showed that maximum hardness was reached after 15 min exposure to 0.14 mol dm^?3 Ca²⁺. Exposure of cells to Ca²⁺ for this time caused a 15% reduction in the rate of oxygen uptake. Levels of clavulanic acid produced by free cells were higher than those produced by immobilized cells; production was dependent on the degree of aeration of the cells.     

牛奶中β-内酰胺类和三聚氰胺检测方法的建立

建立一种快速、简便,同时针对牛奶中β-内酰胺类抗生素和三聚氰胺残留的检测方法。应用竞争抑制免疫层析原理,研制β-内酰胺类和三聚氰胺胶体金试纸条。该试纸条检测限分别为青霉素G2μg/L、氨苄青霉素3μg/L、阿莫西林3μg/L、苯唑青霉素6μg/L、邻氯青霉素6μg/L、双氯青霉素6μg/L、萘夫西林20μg/L、头孢喹肟20μg/L、头孢哌酮40μg/L、头孢曲松50μg/L、头孢噻呋90μg/L、头孢洛宁10μg/L、三聚氰胺50μg/L,假阳性率低于5%、假阴性率为0,检测时间不超过15min。该方法操作简便、灵敏度高、特异性强,适用于乳品流通环节中β-内酰胺类抗生素和三聚氰胺残留的快速检测。     

β-内酰胺类抗生素质谱裂解机理研究

采用电喷雾-四极杆-飞行时间串联质谱(ESI-Q-TOF-MS/MS)对3种头孢类和2种青霉素类药物的[M+Na]⁺ 裂解规律进行研究。头孢类药物[M+Na]⁺裂解可产生许多互补的碎片离子,1,3-H重排和retro-Diels-Alder (RDA)是其重要的裂解方式;青霉素类药物[M+Na]⁺裂解除了一些常规的中性分子丢失外,在氘代实验的基础上提出了比以往更合理的H₂S丢失途径,即1,5-H重排。本实验丰富了β-内酰胺类药物的质谱裂解途径,对应用质谱技术快速鉴定复杂体系中β-内酰胺类抗生素具有重要作用。     

牛乳源金黄色葡萄球菌耐药性变迁及β内酰胺类药物耐药基因分析

采用肉汤微量稀释法,对203 株源于2006—2011年四川牛乳源金黄色葡萄球菌(Staphylococcus aureus,Sa)进行10 种常用抗生素药敏性检测,多重聚合酶链式反应(multiplex polymerase chain reaction,M-PCR)法对其耐甲氧西林基因(mecA)和β-内酰胺类药物耐药基因(blaZ)进行分析,了解Sa耐药性变迁。结果表明:牛乳源Sa菌株对青霉素、氨苄西林耐药率一直居高不下;对阿莫西林/克拉维酸、红霉素、甲氧苄啶/磺胺甲噁唑耐药率有增强趋势;对林可霉素、四环素耐药率呈降低趋势;对环丙沙星耐药率不定;对苯唑西林和头孢噻呋敏感;Sa分离株多重耐药率介于72.1%～100.0%,显示出不尽相同的耐药谱,却呈现出不断增宽的趋势。M-PCR检测显示,2006—2011年分离Sa菌株未从基因水平扩增出mecA基因;不同年度分离株均不同程度携带blaZ基因,不同年度分离株blaZ+检出率介于49.1%～87.5%。药敏实验结果与相关耐药基因检测结果存在对应关系,部分菌株的耐药性与耐药基因的检出率不一致,推测还存在其他耐药机制。结论:四川地区牛乳源金黄色葡萄球菌耐药性不容乐观。     

Multivariate calibration methods applied to the monitoring of the enzymatic synthesis of amipicilin

An integrated semi-continuous rector, with simultaneous crystallization of the antibiotic, is the most promising alternative for the enzymatic synthesis of semi-synthetic penicillins. Closed-loop optimization of the reactor operation requires the measurement of its state variables. An efficient method for on-line monitoring of these variables, i.e., the species concentrations, which is consistent with the dynamics of the process, is presented here. Multivariate calibration has been used to reduce times of analysis in multicomponent systems, and this is the approach of this work. Three multivariate calibration methods are compared for prediction of the concentrations of the components present in the enzymatic synthesis of ampicillin. UV spectra and their first-order derivatives were used as input data for the models. Results showed that all methods (SPA, PCR and PLS) had similar performances for this system. The use of first-order derivatives of the spectra did not improve substantially the performance of the methods. Bench assays of synthesis of ampicillin using immobilized penicillin G acylase (PGA) as catalyst were carried out to validate the methodology. Its results were compared with HPLC analyses. The technique showed to be very accurate for monitoring the concentrations of ampicillin (desired product) and 6-aminopenicillanic acid (6-APA, most expensive substrate), with precision similar to those obtained by HPLC. Prior information of the initial reactor state may be used to improve the estimation of less sensitive components (phenylglycine methyl ester, PGME and phenylglycine, PG). Modifications on the biocatalyst must be made in order to use the proposed automatic sampler when crystallization of products occurs.     

N-脱氢枞基单环β-内酰胺衍生物的合成

脱氢枞胺与取代芳香基甲醛缩合反应合成Schiff碱衍生物,Schiff碱化合物继续在三乙胺催化剂的无水苯反应液中分别与氯乙酰氯[2+2]环加成常温合成了6种标题化合物,其产率为31%~49%,目标产物经IR、1HNMR、13CNMR光谱分析确证。     

1,5-苯并硫氮杂-α氨基-β-内酰胺的合成

甘氨酸和邻苯二甲酸酐反应 ,首先得到邻苯二甲酰基保护的甘氨酰氯 ,继而和 1 ,5 -苯并硫氮杂在三乙胺的存在下作用 ,得到 6个 1 ,5 -苯并硫氮杂 -α氨基 -β-内酰胺衍生物。所有产物的结构均经 1H NMR、IR、MS、和元素分析验证     

Efficacy of a lactoferrin-penicillin combination to treat {beta}-lactam-resistant Staphylococcus aureus mastitis

The efficacy of intramammary (IM) treatments containing penicillin G (PG) alone or a combination of PG and bovine lactoferrin (bLF) was evaluated using a model of experimentally induced chronic bovine mastitis caused by a clinical isolate of Staphylococcus aureus highly resistant to β-lactam antibiotics. First, we confirmed that this strain could cause mastitis and infection could not be cured with PG alone. In a second trial, chronic mastitis was induced in 19 late-lactating cows by injecting a low dose of Staph. aureus through the teat canal of all quarters. After 15 d, cows with stable infections in their 4 quarters had their mammary quarters randomly assigned, within cow, to 1 of 4 IM treatments as follows: 1) citrate buffer, 2) 100,000 IU of PG, (3) 1 g of bLF, or 4) 1 g of bLF + 100,000 IU of PG. Treatments were repeated twice a day for 5 d. A third trial was undertaken to investigate the effect of an extended therapy on chronic mastitis acquired in a previous lactation. One month before dry-off, 20 gravid cows regrouped by dates of calving were infected in their 4 quarters. Once infections were established, cows were dried off abruptly. After calving, aseptic milk samples were collected separately from all quarters for 4 wk to monitor infection. Mammary quarters from enrolled cows were then randomly assigned, within cow, to 1 of 2 treatments as follows: 1) 100,000 IU of PG or 2) 250 mg of bLF + 100,000 IU of PG. Treatments were administered IM twice a day for 7 d. For all trials, milk samples were taken to monitor bacterial concentration and somatic cell count. Bacteriological cure rate was determined using milk samples taken 3 and 4 wk after initiation of treatments. For the second trial, cure rate was null for control quarters, 11.1% for bLF, 9.1% for PG, and 45.5% for the bLF + PG combination. For cows infected in their previous lactation, cure rate was higher for the bLF + PG combination (33.3%) compared with PG alone (12.5%). In conclusion, bLF added to PG is an effective combination (i.e., 3- to 5-times higher cure rate) for the treatment of stable Staph. aureu infections highly resistant to β-lactam antibiotics.     

The Effect of Rotating Magnetic Field on Susceptibility Profile of Methicillin-Resistant Staphylococcus aureus Strains Exposed to Activity of Different Groups of Antibiotics

Methicillin-resistant strains of Staphylococcus aureus (MRSA) have become a global issue for healthcare systems due to their resistance to most β-lactam antibiotics, frequently accompanied by resistance to other classes of antibiotics. In this work, we analyzed the impact of combined use of rotating magnetic field (RMF) with various classes of antibiotics (β-lactams, glycopeptides, macrolides, lincosamides, aminoglycosides, tetracyclines, and fluoroquinolones) against nine S. aureus strains (eight methicillin-resistant and one methicillin-sensitive). The results indicated that the application of RMF combined with antibiotics interfering with cell walls (particularly with the β-lactam antibiotics) translate into favorable changes in staphylococcal growth inhibition zones or in minimal inhibitory concentration values compared to the control settings, which were unexposed to RMF. As an example, the MIC value of cefoxitin was reduced in all MRSA strains by up to 42 times. Apart from the β-lactams, the reduced MIC values were also found for erythromycin, clindamycin, and tetracycline (three strains), ciprofloxacin (one strain), gentamicin (six strains), and teicoplanin (seven strains). The results obtained with the use of in vitro biofilm model confirm that the disturbances caused by RMF in the bacterial cell walls increase the effectiveness of the antibiotics towards MRSA. Because the clinical demand for new therapeutic options effective against MRSA is undisputable, the outcomes and conclusions drawn from the present study may be considered an important road into the application of magnetic fields to fight infections caused by methicillin-resistant staphylococci.