庆大霉素适应性菌株遗传稳定性研究

适应性进化是工业微生物遗传育种的重要技术手段之一。以庆大霉素连续进化1 200代的干酪乳杆菌Zhang为研究对象,将其在去掉选择压力的培养基中连续传1 000代,对其细胞形态、活菌数、浊度、耐药表型、基因型的变化进行跟踪监测。研究结果显示:适应性菌株在去掉选择压力环境中进化1 000代后,其细胞形态、活菌数、浊度及耐药表型趋于稳定;基因组仅检测到11个突变位点,包括4个同义突变位点和7个非同义突变位点。干酪乳杆菌Zhang庆大霉素适应性菌株具有良好的遗传稳定性。     

Monoolein–Water Liquid Crystalline Gels of Gentamicin as Bioresorbable Implants for the Local Treatment of Chronic Osteomyelitis: In Vitro Characterization

To maximize the efficacy of chronic osteomyelitis antibiotherapy while reducing antibiotic systemic toxicity, as well as time and costs of hospitalizations, it has been thought that monoolein–water gels incorporating gentamicin sulfate could be used as local, bioresorbable, and sustained-release implants. For this purpose, four formulations were examined with regard to their physicochemical and in vitro drug release characteristics. Hot stage microscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction showed cubic liquid crystalline and eutectic structures. The more suitable formulation consisting of 80–15–5% wt/wt monoolein–water–gentamicin sulfate progressively released the antibiotic for a period of 3 weeks without burst effect. Moreover, the content and the release profile of gentamicin sulfate were not significantly changed after storage at 2–6°C for a period of 10 months.     

Prevalence and antimicrobial resistance of Salmonella isolated from an integrated broiler chicken supply chain in Qingdao,China

The present study analyzed the prevalence and antimicrobial resistance of Salmonella along an integrated broiler chicken supply chain. A total of 172 Salmonella isolates were recovered from 1148 samples collected from four sample sources (breeder farms, broiler farms, abattoir, and retail markets), representing nine production stages. These Salmonella isolates were examined for antimicrobial susceptibility to 12 different antimicrobial agents using a disk diffusion assay. Among them, 168 were identified as six different serotypes of Salmonella enterica. The predominant serotype was S. Enteritidis (n = 116), followed by S. Infantis (n = 18), S. Gueuletapee (n = 16), S. Derby (n = 12), S. Meleagridis (n = 4), and S. London (n = 2). The remaining four isolates were serogroup-untypeable. A majority of the 172 isolates (96.51%) was resistant to one or more antibiotics and 61.05% of the Salmonella isolates showed a multidrug resistance phenotype. Statistical analysis indicated the one risk product stage for Salmonella contamination occurred in the sample source at the abattoir, specifically the stage of Carcasses after chilling. The majority of S. Enteritidis isolates shared the same pulsed-field gel electrophoresis (PFGE) cluster, suggesting that the S. Enteritidis strain might spread along the broiler chicken supply chain. The prevalence and antimicrobial resistance of Salmonella in different production stages suggest the importance of controlling Salmonella in the broiler chicken supply chain for public health, underlying the need for improved measures of reducing carcass contamination in abattoirs and the appropriate use of antimicrobials in broiler flocks.     

Differential patterns of antimicrobial resistance in population subsets of Escherichia coli isolated from waste- and surface waters

The species Escherichia coli comprises different subgroups with distinct phylogeny, physiology and ecology and, thus, presumably, with different roles in antimicrobial resistance dissemination. E. coli strains isolated from raw and treated municipal wastewater and from urban water streams were characterized in terms of phylogenetic groups, antimicrobial resistance patterns and the presence of class 1 and class 2 integrons. Our main objective was to investigate the contribution of the different phylo-groups in antimicrobial resistance dissemination in urban waters. Groups A and B1 were predominant in all types of water, evidencing, respectively, the lowest and the highest resistance prevalence. Municipal wastewater treatment was accompanied by significant increases of ciprofloxacin and streptomycin resistance (p < 0.01). Antimicrobial resistance prevalence differed significantly between the different phylo-groups and within the same group, mainly in group A. Such differences contributed to explain the higher ciprofloxacin and streptomycin resistance rates observed in treated effluent in comparison with the raw wastewater. We conclude that the dynamics of the bacterial populations has a major role on the dissemination of antimicrobial resistance in the environment.     

Artificial Channels in an Infectious Biofilm Created by Magnetic Nanoparticles Enhanced Bacterial Killing by Antibiotics

The poor penetrability of many biofilms contributes to the recalcitrance of infectious biofilms to antimicrobial treatment. Here, a new application for the use of magnetic nanoparticles in nanomedicine to create artificial channels in infectious biofilms to enhance antimicrobial penetration and bacterial killing is proposed. Staphylococcus aureus biofilms are exposed to magnetic‐iron‐oxide nanoparticles (MIONPs), while magnetically forcing MIONP movement through the biofilm. Confocal laser scanning microscopy demonstrates artificial channel digging perpendicular to the substratum surface. Artificial channel digging significantly (4–6‐fold) enhances biofilm penetration and bacterial killing efficacy by gentamicin in two S. aureus strains with and without the ability to produce extracellular polymeric substances. Herewith, this work provides a simple, new, and easy way to enhance the eradication of infectious biofilms using MIONPs combined with clinically applied antibiotic therapies.     

羊同种庆大霉素抗菌骨的制备及抗感染和成骨效果的扫描电镜观察

目的：研制一种既有抗感染能力，又有成骨作用，且免疫原性低的新型植骨材料。方法：采用超声和负压双重复合法制备复合庆大霉素羊同种抗菌骨，辐照灭菌后，植入羊股（肱）骨骨缺损合并感染模型，通过扫描电镜观察其抗感染效果及成骨能力。结果：抗菌骨组在体内抗感染和成骨效果明显优于对照组。结论：庆大霉素羊同种抗菌骨具有较好的局部抗感染效果及成骨能力。     

阿莫西林与庆大霉素或奈替米星联合应用PAE的比较

目的 阿莫西林(AMPC)与庆大霉素(GM)或奈替米星(NTL)联合应用抗生素后效应(PAE)的比较。方法 应用光密度法测定PAE。结果 AMPC单用时对金黄色葡萄球菌和粪肠球菌有较长的PAE,对大肠埃希氏菌PAE甚小;GM和NTL单用对G'球菌的PAE亦很明显,对大肠埃希氏菌PAE稍短,但比单用AMPC要长。NTL的PAE比GM长,可能与受试菌对NTL敏感性高于GM有关。三种药物PAE均有随药物浓度增加而延长的趋势。AMPC与4倍MIC的GM或NTL联用时对受试菌的PAE均呈协同或相加效应;对G⁺球菌的联合PAE比G^-杆菌明显延长;AMPC与NTL的联合PAE长于与GM联合的PAE。结论 AMPC与GM或NTL联用时延长给药间隔,仍可维持强大的抗菌活性,减轻不良反应,AMPC与NTL联用优于与GM联用。     

Formulation development and in vitro evaluation of gentamicin sulfate-loaded PLGA nanoparticles based film for the treatment of surgical site infection by Box–Behnken design

Objective: Gentamicin sulfate (GS)–loaded poly lactic-co-glycolic acid (PLGA) polymeric nanoparticles (PNPs) were developed and incorporated in film for the treatment of surgical site infection (SSI).

Method: PNPs were prepared by double emulsification solvent removal technique using ethyl acetate solution containing PLGA and polyvinyl alcohol (PVA) as an emulsifier. The emulsion was re-emulsified using Gum Kondagogu (GKK). PNPs loaded film was prepared with 5% w/v solution of pullulan in PNPs using solvent casting technique. Design of Experiment (DoE) study using Box–Behnken design was performed for the optimization of PNPs. Drug release study was carried out for PNPs at phosphate buffer saline (PBS) pH 6.4 and simulated wound fluid (SWF) pH 7.4.

Result: PNPs were found to have average particle size 280?±?12.04?nm, polydispersity index (PDI) 0.15?±?0.01 and zeta potential – 4.9?±?0.84?mV. Scanning electron microscopy (SEM) showed spherical nature of PNPs along with particle size of 160?±?35.30?nm confirmed with transmission electron microscopy (TEM). PNPs were found to be effective against Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA). Optimized batch of film showed in vitro disintegration time below 8?min with tensile strength (TS) 0.06?±?0.03 N/cm² and percentage elongation (% E) 70.95?±?4.29. X-ray diffraction study (XRD) confirmed amorphous nature of GS, PLGA, pullulan, GKK and film.

Conclusion: PNPs showed controlled release of GS after an initial burst release. Developed film can be an effective approach for management of SSI and control of antibiotic induced drug resistance.     

Gentamicin Blocks the ACh-Induced BK Current in Guinea Pig Type II Vestibular Hair Cells by Competing with Ca2+ at the l-Type Calcium Channel

Type II vestibular hair cells (VHCs II) contain big-conductance Ca²⁺-dependent K⁺ channels (BK) and l-type calcium channels. Our previous studies in guinea pig VHCs II indicated that acetylcholine (ACh) evoked the BK current by triggering the influx of Ca²⁺ ions through l-type Ca²⁺ channels, which was mediated by M2 muscarinic ACh receptor (mAChRs). Aminoglycoside antibiotics, such as gentamicin (GM), are known to have vestibulotoxicity, including damaging effects on the efferent nerve endings on VHCs II. This study used the whole-cell patch clamp technique to determine whether GM affects the vestibular efferent system at postsynaptic M2-mAChRs or the membrane ion channels. We found that GM could block the ACh-induced BK current and that inhibition was reversible, voltage-independent, and dose-dependent with an IC₅₀ value of 36.3 ± 7.8 μM. Increasing the ACh concentration had little influence on GM blocking effect, but increasing the extracellular Ca²⁺ concentration ([Ca²⁺]_o) could antagonize it. Moreover, 50 μM GM potently blocked Ca²⁺ currents activated by (−)-Bay-K8644, but did not block BK currents induced by NS1619. These observations indicate that GM most likely blocks the M2 mAChR-mediated response by competing with Ca²⁺ at the l-type calcium channel. These results provide insights into the vestibulotoxicity of aminoglycoside antibiotics on mammalian VHCs II.