抗菌药物对产超广谱β内酰胺酶大肠埃希菌和肺炎克雷伯菌接种效应的研究

目的研究美罗培南、头孢米诺、哌拉西林-他唑巴坦、头孢吡肟、头孢他啶、头孢噻肟和头孢曲松7种常见抗生素对产ESBLs大肠埃希菌和肺炎克雷伯菌的接种效应。方法用微量肉汤稀释法测定7种抗生素对22株产ESBLs大肠埃希菌和肺炎克雷伯菌在标准细菌接种量(5×10~5CFU/mL)和高接种菌量(5×10~7CFU/mL)时的MIC。结果随着接种菌量增加,美罗培南和头孢米诺对所有受试菌株的MIC无接种效应;哌拉西林-他唑巴坦对SHV-12型和1株CTX-M-14菌的MIC表现出接种效应;头孢吡肟、头孢他啶、头孢噻肟和头孢曲松存在接种效应的菌种分别占所有受试菌株的86.4%(19/22)、40.9%(9/22)、10%(22/22)和100%(22/22)。结论对22株产ESBLs大肠埃希菌和肺炎克雷伯菌,美罗培南和头孢米诺不存在接种效应,哌拉西林-他唑巴坦对部分基因型ESBLs菌株(SHV-12型和1株CTX-M-14菌株)存在接种效应,头孢吡肟、头孢他啶、头孢噻肟和头孢曲松存在接种效应。     

Different Kinetic of Enzymatic Inactivation of Lincomycin and Clindamycin in Staphylococcus aureus

Summary

Lincosamide inactivation nucleotidylation (Lin) enzyme determined by the pBI109PGL plasmid of Staphylococcus epidermidis exhibits high level resistance to lincomycin but sensitivity to clindamycin by standard susceptibility methods. Substrate profile determination showed clindamycin to be a better substrate for the enzyme than lincomycin. In cultures of the plasmid-harboring strain, the level of clindamycin decreased below the inhibitory concentration in the first 4 hours of incubation but the level of lincomycin persisted longer. The initial extended inhibitory effect of clindamycin is due to better membrane penetrating ability, resulting in a higher intracellular concentration than that of lincomycin. Moreover, energy-dependent reduction in clindamycin uptake, probably due to active efflux of clindamycin but not of lincomycin, was observed. A therapeutic effect of clindamycin is not expected in infections caused by Lin-producer strains because the bacteriostatic effect of the drug is rapidly eliminated after administration.     

Norwalk virus: How infectious is it?

Noroviruses are major agents of viral gastroenteritis worldwide. The infectivity of Norwalk virus, the prototype norovirus, has been studied in susceptible human volunteers. A new variant of the hit theory model of microbial infection was developed to estimate the variation in Norwalk virus infectivity, as well as the degree of virus aggregation, consistent with independent (electron microscopic) observations. Explicit modeling of viral aggregation allows us to express virus infectivity per single infectious unit (particle). Comparison of a primary and a secondary inoculum showed that passage through a human host does not change Norwalk virus infectivity. We estimate the average probability of infection for a single Norwalk virus particle to be close to 0.5, exceeding that reported for any other virus studied to date. Infected subjects had a dose-dependent probability of becoming ill, ranging from 0.1 (at a dose of 10(3) NV genomes) to 0.7 (at 10(8) virus genomes). A norovirus dose response model is important for understanding its transmission and essential for development of a quantitative risk model. Norwalk virus is a valuable model system to study virulence because genetic factors are known for both complete and partial protection; the latter can be quantitatively described as heterogeneity in dose response models.     

不同器材在制备菌片中所滴10μl菌液菌量误差的试验观察

经试验，用注射器、２０μｌ移液器与０．１ｍｌ微量吸管所滴枯草杆菌黑色变种芽胞菌悬液（１０μｌ），回收菌量在平均值±１０％范围内者分别占样本数的８６．６％、８５．０％与４１．７％。其可重复性，以前两者为优。     

利用气升式生物反应器培养铁皮石斛原球茎

目的:探明影响反应器内铁皮石斛原球茎生长及物质合成的因素,为铁皮石斛原材料的大量生产提供一种新方法.方法:利用3L气升式生物反应器,以组培原球茎为材料,研究了接种量、光照强度和通气量对原球茎增殖生长和多糖及石斛碱积累的影响.结果:当接种量为10g· L-1时,培养30 d后原球茎颜色深绿,生长健壮.多糖含量在接种量处理间无差异,但石斛碱含量有差异(接种量10g· L-1处理最高),多糖和石斛碱生产量在10g·L-1接种密度中最高.光照强度1600lx条件下原球茎生长最旺盛,光照对铁皮石斛原球茎多糖的积累起到促进作用,但对石斛碱的积累则有抑制作用,多糖含量和生产量在1 600,2 400 lx光照处理下好于暗条件处理;石斛碱的含量虽然在暗处理中最高,但因原球茎生长不佳,石斛碱的生产量在1 600 lx的光照强度处理中出现最大值.通气量为0.2(空气体积/培养体积/min)时原球茎生长健壮,颜色鲜绿,生长优于0.1,0.3处理,且多糖和石斛碱含量和产量均达最大值.结论:在工作体积为2L的气升式球型生物反应器内,接入10g·L-1原球茎外植体,光照强度调节为1 600 lx,通气量为0.2有利于原球茎生长和多糖及石斛碱的生产,铁皮石斛原球茎生物反应器培养是大量快速生产多糖和石斛碱的有效途径.     

Factors Influencing Deoxynivalenol Accumulation in Small Grain Cereals

Deoxynivalenol (DON) is a mycotoxin produced by the plant pathogenic fungi Fusarium graminearum and F. culmorum. These and other closely related fungi cause a disease known as Fusarium head blight (FHB) in small grain cereals. Other mycotoxins produced by FHB-causing fungi include nivalenol, T-2 toxin, and zearalenone. Ingestion of mycotoxin-contaminated food and feed can lead to toxicosis in humans and animals, respectively. DON is the predominant and most economically important of these mycotoxins in the majority of small grain-producing regions of the world. This review examines the factors that influence DON accumulation in small grain cereals from an agricultural perspective. The occurrence and economic importance of FHB and DON in small grain cereals, epidemiological factors and cereal production practices that favor FHB development and DON accumulation in grain under field conditions, and regulatory/advisory standards for DON in food and feed are discussed. This information can be used to develop strategies that reduce DON accumulation in grain before harvest and to mitigate the human and animal health risks associated with DON contamination of food and feed.     

MIC distribution and inoculum effect of LY333328: A study of vancomycin-susceptible and VanA-type and VanC-type enterococci obtained from intensive care unit patient surveillance cultures

Objectives: To determine the in vitro activity and inoculum effect of LY333328, a semisynthetic glycopeptide, against vancomycin-susceptible and vancomycin-resistant enterococcal isolates.
Methods: One hundred and seventy-six enterococcal isolates (117 vancomycin-susceptible, 29 VanA-type and 30 VanC-type isolates) obtained from surveillance cultures of 139 intensive care unit patients were studied by the standard agar dilution method. Vancomycin resistance determinants were characterized by PCR.
Results: The activity of LY333328 was comparable (MIC range, 0.1–2 mg/L) to those of vancomycin (0.1–4 mg/L) and teicoplanin (0.06–1 mg/L) for vancomycin-susceptible isolates. LY333328 was more active (0.1–8 mg/L) than vancomycin (256 to >1024 mg/L) and teicoplanin (32–512 mg/L) against VanA-type isolates, and similar (0.2–1 mg/L) to teicoplanin (0.1–0.5 mg/L) against VanC-type isolates. The MIC distribution of LY333328 displayed a narrower range than that of vancomycin, with no clear distinction between susceptible and resistant populations. The increment in the inoculum size, from 10⁴ to 10⁶ CFU/spot, of susceptible isolates increased the MIC values of LY333328, vancomycin and teicoplanin by factors of 11.4, 1.6 and 3.8, respectively. The corresponding factors for LY333328 for VanA-type and VanC-type isolates were 3.5 and 6.4, respectively.
Conclusions: LY333328 displays an excellent in vitro activity against vancomycin-susceptible and -resistant enterococci. Nevertheless, the inoculum size used in susceptibility tests should be carefully controlled.     

中国药典抗生素微生物检定上层培养基中加菌量的研究

首次对中国药典抗生素微生物检定法中试验菌为藤黄八叠球菌、枯草芽孢杆菌、短小芽孢杆菌所检定抗生素品种的上层培养基中的加菌量进行了较为系统的研究。实验表明以规定原菌液的透光率和稀释数即可直接获得符合药典规定的抑菌圈大小，方法简便可靠、易于规范化统一操作。     

Preanalytical conditions for broth microdilution antifungal susceptibility of Microsporum spp

Dermatophytoses caused by the genus Microsporum require a long-duration therapy compared to infections caused by other genera. Treatment of these cutaneous infections includes topical and systemic antifungal agents. Tinea capitis and tinea unguium caused by M. canis and M. gypseum are the most difficult-to-treat dermatophytoses. There are few specific studies about corresponding antifungal susceptibility in vitro. Recently, the Clinical and Laboratory Standards Institute proposed the M38A document as standard to determine the minimum inhibitory concentrations (MICs) of several antifungal agents against conidium-forming filamentous fungi; however, dermatophytes were not included in this document. This study aimed to contribute to continuing investigations concerning the optimal antifungal susceptibility testing conditions of Microsporum spp. to terbinafine, ciclopiroxolamine and griseofulvin . The results pointed out potato dextrose agar as the best culture medium for inducing conidia sporulation, inoculum density amounting to 1 × 10³ conidia ml⁻¹, containing only microconidia, with an incubation time of 7 days at 28 °C and 100% growth inhibition serving as an endpoint. The minimum fungicidal concentration values were in accordance with the MICs values, showing a fungicidal activity of these drugs towards the tested strains. According to our results, in general, terbinafine was more active than griseofulvin and ciclopiroxolamine.     

Antibiotic susceptibilities of livestock isolates of leptospira

Leptospirosis is the most common zoonotic disease and is endemic worldwide. The antibiotic susceptibilities of Leptospira strains isolated from both humans and animals are poorly documented. This issue is particularly important for isolates from food-producing animals which are regularly exposed to antibiotic treatments. This study assessed the susceptibility of 35 leptospira strains isolated from food-producing animals of diverse geographical origins between 1936 and 2016 to the antimicrobial agents used most commonly in animals. A broth microdilution method was used to determine the susceptibilities of Leptospira strains isolated from livestock to 11 antibiotics. All isolates were susceptible to penicillin, amoxicillin, clavulanate, cephalexin, ceftriaxone, doxycycline, tetracycline, streptomycin, enrofloxacin and spectinomycin, but not polymyxin [minimum inhibitory concentration (MIC)?≥?4?μg/L]. For tetracycline and doxycycline, the MIC was significantly higher for the recent isolates from Sardinia, Italy than for the other isolates. Antimicrobial susceptibilities were also determined with 10- and 100-fold higher inocula. High inocula significantly diminished the antibacterial effect by at least 10-fold for enrofloxacin (MIC ≥256?μg/L), streptomycin (MIC ≥16?μg/L) and tetracycline (MIC ≥32?μg/L), suggesting selection of resistant strains for high inocula. These findings contribute to the assessment of whether certain antibiotics are potentially useful for the treatment of leptospirosis, and point out the risk of failure for some antibiotics during infection with a high inoculum in both animals and humans. This study strengthens the need to detect and prevent the emergence of antimicrobial resistance of this major emerging zoonotic pathogen.