北京市通州区食源性疾病监测病例中副溶血弧菌的病原特征分析

目的 了解通州区2015—2021年食源性疾病监测病例中副溶血弧菌的脉冲场凝胶电泳（PFGE）优势带型、耐药情况和毒力基因携带情况,为副溶血弧菌感染防控和治疗提供参考数据。方法 对2015—2021年通州区定点监测医院门诊腹泻病例的粪便样本进行副溶血弧菌分离培养,对其进行血清分型、毒力基因检测、PFGE聚类分析及药敏试验。结果 2 828份粪便标本中检出副溶血弧菌100株,检出率为3.54%,每年7~9月是检出高峰月份。不同年份副溶血弧菌检出率差异具有统计学意义（χ²=53.94,P<0.001）。100株副溶血弧菌中有一株未携带tlh基因,89.00%的菌株携带致病性毒力基因tdh。副溶血弧菌优势血清型为O3∶K6（66/100）,其次是O4∶K8（9/100）。98株菌副溶血弧菌（2株降解）PFGE分型结果显示副溶血性弧菌有39个PFGE带型,命名为V1-V39,条带相似度在79.6%~100%之间,基因分布呈高度多态性,V22和V25是通州区副溶血弧菌的优势带型。菌株对头孢唑林的耐药率最高（32.00%）,其次是氨苄西林（14.00%）和多黏菌素E（13.00%）,对四环素类、氯霉素类、氨基糖苷类、碳青霉烯类四类药物100%敏感。结论 通州区2015—2021年食源性疾病监测病例中检出的副溶血弧菌主要是O3∶K6型tdh⁺- trh^-菌株,对头孢唑林,氨苄西林和多黏菌素E耐药。PFGE图谱主要流行菌株带型相似度在93.1%以上,存在暴发风险,食品安全相关部门需做好副溶血弧菌监测及暴发预警工作,预防食源性疾病暴发。     

三文鱼来源副溶血性弧菌的血清分型、毒力基因及耐药性研究

目的 对2019年广州市售三文鱼中副溶血性弧菌的血清型、毒力基因分布及耐药特征进行研究,为防控因食用三文鱼引起副溶血性弧菌食源性疾病提供数据支持。方法 根据GB 4789.7—2013方法对90份广州市售三文鱼样品进行副溶血性弧菌分离、定量及血清分型,分离株的鉴定及耐药性分析采用全自动微生物鉴定仪分析,通过PCR扩增对毒力基因进行检测。结果 90份三文鱼样品中,有16份检出副溶血性弧菌,总检出率为17.78%,阳性样品污染量范围为3.6~93 MPN/g,其中批发市场的检出率（27.50%）最高。MPN计数阳性管分离得到的72株副溶血性弧菌经血清凝集共分出11个O群血清型,分型率为80.56%,其中O11、O9和O6群为主要血清型,占51.39%,其他血清型分布较分散。72株副溶血性弧菌均含有tlh基因,且均未检测到trh和tdh基因。药敏分析发现,全部分离株对碳青霉烯类、单酰胺环类、氨基糖苷类、喹诺酮类和硝基呋喃类等5类18种抗生素敏感。分离株对氨苄西林高度耐药,耐药率达97.22%,少数分离株对哌拉西林（1.39%）和复方新诺明（5.56%）耐药。6.94%的分离株同时对2种抗生素耐药,未出现多重耐药。结论 广州市售三文鱼受到副溶血性弧菌污染程度较高,分离株的血清型呈多样化,主要为非致病株,但具有一定程度的耐药,存在危害健康的潜在风险。     

温州市食品中小肠结肠炎耶尔森氏菌分布及分子分型研究

目的 了解温州市食品中小肠结肠炎耶尔森氏菌的分子分型及分布特征。方法 4 ℃增菌后用选择性培养基对食品中的小肠结肠炎耶尔森氏菌进行分离鉴定,分析阳性菌株的生物型、血清型、毒力基因型、耐药性和脉冲场凝胶电泳（PFGE）分子型别。结果 采集6类食品,共676份样品,其中68份样品检出69株小肠结肠炎耶尔森氏菌,检出率为10.1%（68/676）。调理肉制品检出率最高（20.5%,9/44）,其次为速冻食品（17.2%,11/64）。95.7%（66/69）的分离株为生物1A型,生物血清型以1A/O∶5（29.0%）为主,其次为1A/O∶8（14.5%）;88.4%（61/69）的菌株仅携带ystB基因,检出1株4/O∶3型菌株携带毒力基因ail、ystA、yadA、virF。分离株对14种抗菌药物的敏感率达到94%以上。32株血清已分型菌株,分为29种PFGE带型。结论 温州市食品中存在一定程度的小肠结肠炎耶尔森氏菌污染,且检出致病性小肠结肠炎耶尔森菌,菌株耐药率处于较低水平,分子分型提示菌株呈高度遗传多态性。     

市售水产品中副溶血性弧菌的毒力及药敏性分析

为了解市售水产品中副溶血性弧菌毒力基因携带情况及药敏性情况,本文采用《GB4789.7-2013食品安全国家标准食品微生物学检验副溶血性弧菌检验》分离培养方法,利用VITEK 2 compact全自动细菌鉴定系统及荧光PCR从市售水产品中分离鉴定出60株副溶血性弧菌分离株,通过常规PCR对60株分离株中四种毒力基因的分布进行筛查,并用VITEK 2 compact全自动细菌鉴定系统对副溶血性弧菌分离株进行药敏性试验。结果显示,市售水产样品的60株副溶血性弧菌分离株中tlh基因携带率为100.00%、tox R/S基因携带率为100.00%、tdh基因携带率为95.00%,trh基因携带率为65.00%,多重毒力基因携带率高,其中四重毒力基因携带率为61.67%;分析60株分离株对19种抗菌药物的药敏情况发现对氨苄西林有极高的耐药性,耐药率为96.67%,多重耐药现象不突出,仅有4株分离株对2种药物耐药。结果表明,市售水产样品中副溶血性弧菌分离株毒力基因携带率较高,且多数携带多重毒力基因;分离株耐药情况不突出,但对抗菌类药物氨苄西林的耐药率较高,需警惕水产食品中副溶血性弧菌的潜在威胁。     

2021年西安市食源性腹泻患者致泻大肠埃希菌耐药性及分子分型

目的 了解2021年西安市食源性腹泻患者致泻大肠埃希菌（DEC）的感染状况、致病型分布、耐药性及分子分型特征。方法 收集西安市5家哨点医院腹泻患者粪便标本,进行DEC分离和PCR毒力基因分型鉴定,采用微量肉汤稀释法和脉冲场凝胶电泳（PFGE）对分离株进行药敏试验和分子分型,结果采用SPSS 19.0软件进行统计学分析。结果 389份粪便标本检出DEC阳性40份,阳性检出率为10.28%（40/389）。共分离到41株DEC,以肠产毒性大肠埃希菌（ETEC）和肠集聚性大肠埃希菌（EAEC）为主,分别占41.46%（17/41）和39.02%（16/41）。ETEC以estIa/estIb基因型为主（70.59%,12/17）,EAEC以astA/pic基因型为主（87.50%,14/16）。40株菌（97.56%,40/41）对至少1种抗生素耐药,对氨苄西林、四环素、头孢噻肟和萘啶酸耐药率均超过50%,多重耐药率为56.10%（23/41）。41株DEC聚类分析得到40种带型,相似度为62.0%~100.0%。结论 2021年西安市食源性腹泻患者中DEC检出率较高,主要致病型为ETEC和EAEC,PFGE带型较为分散,菌株耐药及多重耐药现象比较严重。     

2021年新乡市一起山夫登堡沙门菌食物中毒分离株的病原特征分析

目的 分析2021年新乡市一起山夫登堡沙门菌食物中毒分离株的病原特征。方法 对食物中毒事件进行流行病学调查;对采集的11份样本进行致病菌分离鉴定;对分离出的10株沙门菌进行血清学分型、药敏试验、5种毒力岛（SPIs）特征基因片段（mogA、sseL、mgtC、bcfA、araB）检测及脉冲场凝胶电泳（PFGE）分型分析。结果 10株沙门菌血清抗原式均为1,3,19;g,s,t,即山夫登堡沙门菌。10株沙门菌对头孢唑啉、卡那霉素、庆大霉素、阿米卡星的耐药率为100%,其中从患者粪便中分离出的2株对氨苄西林、四环素、多西环素、氯霉素、复方新诺明的耐药率为100%。PFGE图谱聚类分析显示,10株菌（2株病例株,5株食品株,3株环境株）之间条带无差异,高度同源。10株菌中5种毒力岛特征基因片段均检出。结论 本起食物中毒事件致病因子为山夫登堡沙门菌,该菌携带5种毒力岛特征基因片段,2株病例株沙门菌具有多重耐药性,建议相关部门高度关注。     

广州地区创伤弧菌分子生物学特征分析

目的 了解广州地区创伤弧菌的分子生物学特征。方法 对采集自广州地区的38株创伤弧菌进行全基因组测序,结合从NCBI公共数据库下载的50株序列数据,利用fineSTRUCTURE软件解析创伤弧菌的种群结构,并利用CARD、ResFinder和VFDB数据库对其毒力基因和耐药基因进行鉴定。结果 创伤弧菌分为4个系统发育谱系（L1~L4）,广州地区分离株全部聚集于L1（占47%）和L2（占53%）谱系,ST分型主要为ST357、ST157、ST136、ST139、ST345、ST303等,呈现一定的区域聚集性。创伤弧菌多个基因组鉴定发现acrF、CRP、catB9、rpoC、ugd等11种耐药基因,并首次在创伤弧菌中发现与多黏菌素耐药相关的MCR基因。该物种还携带5类23种毒力基因,编码鞭毛蛋白、Ⅱ型分泌系统蛋白、荚膜多糖、RtxA毒素、铁超载等毒力相关基因。结论 广州地区创伤弧菌高度同源重组,并且携带多种耐药、毒力相关基因,应加强对其监测管理。     

2019—2020年枣庄市副溶血性弧菌病人分离株的耐药性、毒力基因及分子分型分析

目的 了解枣庄市2019—2020年副溶血性弧菌(VP)病人分离株的耐药性、毒力基因携带情况和分子分型特征。方法 参照GB4789.7—2013《食品安全国家标准 食品微生物学检验 副溶血性弧菌检验》进行VP菌株的分离和鉴定,采用微量肉汤稀释法测定VP分离株对12种抗生素的耐药性,利用荧光定量聚合酶链式反应(PCR)技术检测VP分离株的毒力基因(tlh、tdh、trh),使用脉冲场凝胶电泳(PFGE)对分离株进行分子分型检测,并进行聚类分析。采用χ²检验对结果进行统计分析。结果 678份病人粪便标本中VP的检出率为4.57%,31株VP分离株对头孢唑啉耐药率为58.06%,多重耐药率为12.90%,其毒力基因tlh、tdh、trh的携带率分别为100%、96.78%、3.22%。31株VP分为17个带型,2个带型簇,优势带型簇涵盖了93.55%的菌株。结论 枣庄市VP病人分离株对头孢唑啉有较高耐药率,出现了多重耐药株。携带的主要毒力基因为tdh和tlh。PFGE带型集中、同源性高,提示应加强该地区VP的流行病学调查和溯源工作。     

VFDB注释法在食源性金黄色葡萄球菌肠毒素基因分型分析中的应用

目的 应用VFDB注释法对食源性金黄色葡萄球菌肠毒素基因进行分型并评价其准确性。方法 分别使用VFDB注释法和特异引物PCR方法对2009—2016年从北京地区食品中分离的53株金黄色葡萄球菌的18种肠毒素基因（包括传统肠毒素基因sea~see,新型肠毒素基因seg~sej和类肠毒素基因sek~seu）携带情况进行分析。将VFDB注释法所得肠毒素基因序列上传至NCBI,使用BLASTX程序和refseq_protein数据库对注释结果进一步核对。结果 VFDB注释法和PCR方法都检测出53株金黄色葡萄球菌分离株中有45株携带1种或多种肠毒素基因,有8株未携带肠毒素基因,肠毒素基因的总携带率为84.91%（45/53）,经典肠毒素基因的携带率为58.49%（31/53）。45株携带肠毒素基因的分离株中,16株菌（35.56%,16/45）肠毒素基因VFDB分型结果与PCR一致,29株菌（64.44%,29/45）的肠毒素基因VFDB分型结果与PCR不一致。经BLASTX核对,VFDB注释法可能误判的基因型包括sea/sed、sea/sej、sea/sep、sea/ser、seg/ser和sek/sei（VFDB注释/BLASTX核对）。结论 VFDB注释法可对食源性金黄色葡萄球菌肠毒素基因进行分型分析,但是对注释为sea、seg和sek的序列建议采用BLASTX程序和refseq_protein数据库进一步核对,以提高基因分型的准确性。     

2020年辽宁省副溶血性弧菌PFGE分型、血清型分布和耐药谱分析

目的 了解辽宁省副溶血性弧菌（VP）的流行特征,为食源性疾病的防控提供可靠的技术支持,提高对食物中毒应急事件的处理能力。方法 对2020年从辽宁省内14个市内食源性疾病病人和食品中分离的VP进行PFGE分子分型、血清学分型、药物敏感试验并分析。结果 44株VP（食源性疾病分离株22株,食品分离株22株）共分为15个血清型,9个血清群,有8株不能进行K分型,不可分型率为18.2%。食源性疾病分离株分为4个血清型、3个血清群,主要血清群为O3,其次为O1;食品分离株分为11个血清型、6个血清群,主要血清群为O2,其次为O1和O3。44株VP对15种抗生素的药敏结果显示,头孢唑啉耐药率高达68.2%,其次是氨苄西林22.7%、红霉素13.6%、阿奇霉素4.5%、头孢西丁2.3%、头孢噻肟2.3%。菌株主要对β-内酰胺类和大环内酯类抗生素耐药,耐药性逐年增强,一些食源性疾病分离株出现多重耐药,且多重耐药株数量逐年增加。食源性疾病分离株较食品分离株耐药率高,血清型O3∶K6为主要流行菌株,且耐药率高,PFGE分子分型按相似度90%以上,可分为5种PFGE优势带型。食源性疾病分离株相似度较高,可聚类成3个组。而食品分离株相似度较低,除了两株菌相似度大于90%外,其余菌株间相似度均在85%以下。结论 O3与O1血清型菌株之间有高度同源性,提示O3与O1血清型菌株密切相关。食品分离株同源性较低,提示食品株间关联性较差。辽宁省2020年VP分离株耐药情况不容乐观,耐药趋势还需进一步关注。     

Nachweis von Clostridium botulinum Typ A, B, E und F mittels real-time-PCR

Clostridium botulinum is a Gram-positive, anaerobic, spore-performing bacterium with the ability to produce under certain conditions a protein with a characteristical neurotoxicity. Intoxications with C. botulinum toxin belong to the rare occuring food-poisonings; the mortality, however, is very high. C. botulinum produce seven different toxin types (type A to G), human intoxications are currently described to caused by toxin type A, B, E and F. C. botulinum is a strictly anaerobic growing bacterium, so the risk for the consumer’s health is mainly due to non-commercially produced food cans. A special form of botulism is the „infant botulism“. In contrast to the botulism of adults, where the disease is caused through toxin-containing food, spores of C. botulinum can sporulate and produce toxin in the intestines of an infant. The source of infant botulism can be honey, because it contains as a natural product C. botulinum spores. Because of the difficult and time-consuming cultural detection of C. botulinum, PCR methods to screen for the toxin genes A, B, E and F, which are relevant in the human medicine, have been used increasingly during the last years. In this presentation two real-time-PCR assays for C. botulinum, which can be applied in the routine laboratory, will be shown.

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Zusammenfassung: Clostridium botulinum z?hlt zu den anaeroben sporenbildenden Bakterien, die unter bestimmten Bedingungen in der Lage sind, sich in Lebensmitteln zu vermehren und ein Protein mit charakteristischer Neurotoxizit?t zu bilden. Intoxikationen mit Clostridium botulinum-Toxin geh?ren zu den seltenen lebensmittelassoziierten Intoxikationen; die Mortalit?t bei einer Erkrankung ist allerdings sehr hoch. C. botulinum produziert sieben unterschiedliche Toxintypen (Typ A-G), wobei für menschliche Erkrankungsf?lle bisher die Toxintypen A, B, E und F beschrieben sind. Da es sich bei den genannten Keimen um strikt anaerob wachsende Bakterien handelt, stellen vor allem nicht kommerziell hergestellte Konserven, wie z. B. Kesselkonserven, ein Risiko für den Verbraucher dar. Als besondere Form des Botulismus wird der so genannte „S?uglingsbotulismus“ beschrieben. Im Gegensatz zur der Erkrankung, die bei Erwachsenen auftritt und die durch die Aufnahme des bereits toxinhaltigen Lebensmittels verursacht wird, k?nnen Sporen von C. botulinum im Darm von S?uglingen auskeimen und dort Toxine bilden. Ursache für den S?uglingsbotulismus ist h?ufig Honig, der als Naturprodukt C. botulinum-Sporen enthalten kann. Da der kulturelle Nachweis von C. botulinum aufwendig und eine endgültige Differenzierung schwierig ist, wird im Bereich der Routinediagnostik seit einigen Jahren verst?rkt mit PCR-Nachweisverfahren gearbeitet, die ein schnelles Screening auf das Vorhandensein der vier in der Humanmedizin relevanten Toxingene A, B, E und F erm?glichen. In dieser Arbeit werden zwei real-time-PCR-Systeme vorgestellt, die im Bereich der Routinediagnostik einsetzbar sind.

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Eingegangen: 19. Januar 2007     

广西单核细胞增生李斯特菌的流行率、毒力特征和分子分型研究

目的 比较广西不同种类食品中单核细胞增生李斯特菌（以下简称单增李斯特菌）的流行情况、毒力特征和分子分型特征，更好地了解单增李斯特菌的遗传特点及其传播的潜力。方法 对来自2002—2020年的210株单增李斯特菌进行全基因组测序（WGS），分析其序列分型（ST）、克隆群（CC）型及毒力基因。结果 2002—2020年广西53.8%单增李斯特菌分离株来源于肉与肉制品，59.0%分离株来自于谱系Ⅱ，优势ST型为ST8和ST9。79.4%菌株携带LIPI-1基因（hly、prfA、plcA、plcB、mpl、actA），83.7%菌株携带LIPI-2基因（inlC、inlF、inlJ、inlK）。17.6%菌株携带LIPI-3基因（llsA、llsB、llsD、llsG、llsH、llsP、llsX、llsY）。结论 肉与肉制品是广西单增李斯特菌检出率最高的食品类型，分子分型结果证实了单增李斯特菌种群具有高度的遗传多样性，WGS的高分辨力可用于监测食源性单增李斯特菌病的暴发。毒力基因的分布表明广西单增李斯特菌存在不同程度毒力基因的缺失，应警惕高致病性的菌株引起的食源性暴发事件。     

Identification and characterization of Clostridium paraputrificum M-21, a chitinolytic, mesophilic and hydrogen-producing bacterium

A strictly anaerobic, mesophilic and chitinolytic bacterial strain, M-21, was isolated from a soil sample collected from Mie University campus and identified as Clostridium paraputrificum based on morphological and physiological characteristics, and 16S rRNA sequence analysis. C. paraputrificum M-21 utilized chitin and N-acetyl- -glucosamine (GlcNAc), a constituent monosaccharide of chitin, to produce a large amount of gas along with acetic acid and propionic acid as major fermentation products. Hydrogen and carbon dioxide accounted for 65% and 35% of the gas evolved, respectively. The conditions for 1 l batch culture of C. paraputrificum, including pH of the medium, incubation temperature and agitation speed, were optimized for hydrogen production with GlcNAc as the carbon source. The bacterium grew rapidly on GlcNAc with a doubling time of around 30 min, and produced hydrogen gas with a yield of 1.9 mol H₂/mol GlcNAc under the following cultivation conditions: initial medium pH of 6.5, incubation temperature of 45°C, agitation speed of 250 rpm, and working volume of 50% of the fermentor. The dry cell weight harvested from this culture was 2.0 g/l.     

Insecticidal effect of spinosad dust, in combination with diatomaceous earth, against two stored-grain beetle species

Laboratory bioassays were carried out to determine the efficacy of spinosad applied alone or combined with the diatomaceous earth (DE) SilicoSec against adult rice weevils, Sitophilus oryzae and confused flour beetles, Tribolium confusum. Efficacy was assessed on wheat and maize at three dosages of spinosad dust formulation (corresponding to 0.0625, 0.1875 and 0.625 ppm of active ingredient [AI] for S. oryzae and to 0.1875, 0.625 and 1.25 ppm of AI for T. confusum), alone or combined with SilicoSec at 150 ppm for S. oryzae and 250 ppm for T. confusum. The mortality of S. oryzae exposed for 14 d on wheat treated with spinosad ranged between 83% and 100%. Conversely, the mortality of S. oryzae on maize treated with DE or on maize treated with lower doses of spinosad dust did not exceed 19% and was only 59% on maize with the highest spinosad dust treatment. Generally, the presence of SilicoSec combined with spinosad did not significantly increase S. oryzae mortality compared with spinosad alone. For T. confusum, mortality on both commodities was lower than for S. oryzae. After 14 d of exposure on wheat, mortality was 14% at the highest dose of spinosad, but increased to 33% in the presence of DE. Similar results were also obtained for T. confusum exposed on treated maize, which indicated a joint action between spinosad and DE. In the case of S. oryzae, the inclusion of DE reduced progeny production in comparison with spinosad alone. Progeny production of T. confusum was relatively low in all treatments, compared to progeny production of S. oryzae. The results of the study show the potential of combination treatments of spinosad dust and DE, but efficacy varies with the target insect species and commodity.     

Behavior of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium in teewurst, a raw spreadable sausage

The fate of Listeria monocytogenes, Salmonella Typhimurium, or Escherichia coli O157:H7 were separately monitored both in and on teewurst, a traditional raw and spreadable sausage of Germanic origin. Multi-strain cocktails of each pathogen (ca. 5.0 log CFU/g) were used to separately inoculate teewurst that was subsequently stored at 1.5, 4, 10, and 21 °C. When inoculated into commercially-prepared batter just prior to stuffing, in general, the higher the storage temperature, the greater the lethality. Depending on the storage temperature, pathogen levels in the batter decreased by 2.3 to 3.4, ca. 3.8, and 2.2 to 3.6 log CFU/g for E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively, during storage for 30 days. When inoculated onto both the top and bottom faces of sliced commercially-prepared finished product, the results for all four temperatures showed a decrease of 0.9 to 1.4, 1.4 to 1.8, and 2.2 to 3.0 log CFU/g for E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively, over the course of 21 days. With the possible exceptions for salt and carbohydrate levels, chemical analyses of teewurst purchased from five commercial manufacturers revealed only subtle differences in proximate composition for this product type. Our data establish that teewurst does not provide a favourable environment for the survival of E. coli O157:H7, S. Typhimurium, or L. monocytogenes inoculated either into or onto the product.     

Staphylokokken-Enterotoxine: Bildung, Eigenschaften und Nachweis

Under appropriate conditions, Staphylococcus aureus can grow in food and produce enterotoxins which cause vomiting and diarrhoea when ingested. In contrast to the staphylococci staphylococci these toxins are resistant especially to high temperatures and are not inactivated by usual kitchen practice. As the presence of staphylococci is not essential to cause illness, this condition is a typical food poisoning. The estimation of a potential health risk by targeting the organism is therefore only appropriate to raw food. For products which underwent a procedure detrimental to the bacteria, e. g. heat treatment, testing for thermonuclease (indirect detection of a contamination with high numbers of staphylococci, irrespective of the presence of living bacteria at the time of testing) or the detection of enterotoxins can be applied. In this context, the detection of enterotoxin genes using molecular biological tests provides only supplemental information, as positive results are not evidentiary for gene expression and thus for the presence of toxins in the food. In this review, the causative organism and its toxins as well as methods of detection are discussed with special emphasis on molecular biological methods. Eingegangen: 18. Januar 2007; nach überarbeitung angenommen: 20. M?rz 2007     

Biosynthesis of PP-V, a monascorubramine homologue, by Penicillium sp. AZ

The biosynthetic pathway of PP-V, a new monascorubramine homologue, was elucidated by ¹³C-labeling studies. The [1-¹³C] of acetate was incorporated into 2-, 3a-, 4a-, 6-, 8-, 9-, 11-, 13-, 15-, 17-, and 19-Cs of PP-V, and the [2-¹³C], into 3-, 4-, 5-, 8a-, 9a-, 10-, 12-, 14-, 16-, 18-, and 20-Cs. These incorporation patterns coincide with those reported in the biosynthesis of a Monascus azaphilone pigment, monascorubrin.     

Characteristics of Rhodococcus pyridinovorans PYJ-1 for the biodegradation of benzene, toluene, m-xylene (BTX), and their mixtures

The degradation rates of benzene, toluene, and m-xylene (BTX) by Rhodococcus pyridinovorans PYJ-1, were highest at 30, 50, and 25 mg/l, respectively. The degradation rate was highest for toluene (0.106 mg/mg-protein x h) followed by benzene and m-xylene at the optimum pH and temperature of 7 and 32 degrees C, respectively. For BTX mixtures, toluene was the preferred substrate, but degradation of each BTX was competitively inhibited by other BTX compounds. The degradation rate of each component of in the BTX mixture decreased by 57-89% depending on the concentration (1-5 mg/l) of the component compared with that of the component as a single substrate.     

Effect of lactate-enhancement, modified atmosphere packaging, and muscle source on the internal cooked colour of beef steaks

Earlier studies on lactate-mediated colour stability in beef did not address the possible influence on cooked colour. Our objective was to examine the effect of lactate-enhancement, muscle source, and modified atmosphere packaging (MAP) on the internal cooked colour of beef steaks. Longissimus lumborum (LL) and Psoas major (PM) muscles from 16 (n = 16) beef carcasses (USDA Select) were randomly assigned to 4 enhancement treatments (non-injected control, distilled water-enhanced control, 1.25% and 2.5% lactate), and fabricated into 2.54-cm steaks. Steaks were individually packaged in either vacuum (VP), high-oxygen MAP (HIOX; 80% O₂ + 20% CO₂), or carbon monoxide MAP (CO; 0.4% CO + 19.6% CO₂ + 80% N₂), and stored for 0, 5, or 9 days at 1 °C. At the end of storage, surface and internal colour (visual and instrumental) was measured on raw steaks. Steaks were cooked to an internal temperature of 71 °C, and internal cooked colour (visual and instrumental) was evaluated. Lactate-enhancement at 2.5% level resulted in darker (P < 0.05) cooked interiors than other treatments. Interior cooked redness decreased (P < 0.05) during storage for steaks in VP and HIOX, whereas it was stable for steaks in CO. Our findings indicated that the beef industry could utilise a combination of lactate-enhancement and CO MAP to minimise premature browning in whole-muscle beef steaks.     

鼠伤寒沙门菌TA97、TA98、TA100、TA102即用型标准菌株的研制

目的 研制鼠伤寒沙门菌TA97、TA98、TA100、TA102即用型标准菌株。方法 对高、低浓度鼠伤寒沙门菌TA97、TA98、TA100、TA102的冻干菌株进行计数，测定了增菌3、5、7、18 h后冻干菌的自发回变率，依据CNAS-GL003 2018《能力验证样品均匀性和稳定性评价指南》（CNAS-GL003）和GB 15193.4—2014《食品安全国家标准 细菌回复突变试验》（GB 15193.4—2014），测定即用型标准菌株的均匀性、储藏和运输稳定性、自发回变率和诱变剂突变率。比较20株即用型标准菌株和新鲜菌株的自发回变率和诱变剂突变率测试结果的标准偏差。结果 高浓度冻干样品浓度为10⁷~10⁸ CFU/样品，低浓度样品浓度为10⁵~10⁶ CFU/样品；增菌18 h后自发回变率的结果基本符合GB 15193.4—2014要求；4株即用型标准菌株的均匀性结果的F值分别为1.12、1.05、1.68、1.38，F<F_0.05（19，20），符合CNAS-GL003要求。4株冻干菌株在25 ℃ 5 d、4 ℃ 14 d、-20 ℃ 6个月的储存条件，检测结果符合储存和运输稳定性要求。20株即用型冻干标准菌株的自发回变率较新鲜菌株标准偏差小。结论 本研究研制出适用于Ames试验的即用型标准菌株，其均匀性、储存和运输稳定性良好，自发回变的稳定性优于新鲜菌株。