楚雄市1起蜡样芽胞杆菌食物中毒调查报告

目的通过流行病学调查和实验室检测探讨1起食物中毒的流行因素及病原学。方法按照流行病学现场调查方法和实验室细菌学鉴定方法。结果共有18人进餐,10人出现食物中毒症状,罹患率为55.56%,采集到剩余米饭、腌卤腐及腌豆豉样品各1份,中毒者呕吐物2份,患者呕吐物及米饭中均检出蜡样芽胞杆菌。结论该起食物中毒为蜡样芽胞杆菌污染食品所致。     

2012-2015年贵州省炭疽芽胞杆菌分离鉴定及MLVA分型分析

目的 了解菌株的分子流行病学特征,为贵州省炭疽疫情的预防控制提供科学依据。方法 对2012-2015年贵州省间不同地区的409份标本(外环境388份、患者19份和牲畜2份)进行炭疽芽胞杆菌分离培养,采用革兰染色镜检、青霉素抑制试验和噬菌体裂解试验对可疑炭疽菌落进行鉴定,分析菌株检出情况。运用MLVA-15技术对炭疽芽胞杆菌分离株进行基因分型获得各VNTR位点的扩增长度并计算重复单元的重复数目。结合各VNTR位点重复数目,利用NTsys 2.10e软件对不同地区菌株进行聚类分析。结果 从409份标本中分离出34株炭疽芽胞杆菌,检出率为8.31%。其中341份土壤检出33株,检出率为9.68%;17份患者皮肤病灶渗出液检出1株,检出率为5.88%。2015年分离出炭疽杆菌的阳性率最高,占48.72% (19/39)。MLVA-15分析显示,34株菌株被分为3个MLVA型;聚类分析显示,34株菌株被分为A和B两簇,其中A簇又被进一步分为A1和A2分支。来自相同地区或年份的多数菌株聚类关系相对较近。结论 2012-2015年贵州省间各种疑似炭疽送检标本中,土壤的检出阳性率最高,贵州省炭疽芽胞杆菌菌株具有MLVA型别多样性,型别分布和聚类关系具有明显的地域性。     

2011-2018年天水市食品中蜡样芽胞杆菌监测分析

目的了解甘肃省天水市食品中蜡样芽胞杆菌污染情况,为防治由该菌引起的食源性疾病提供科学依据。方法2011—2018年从天水市餐饮服务环节和流通环节随机采集7类共计586份食品样本,按《国家食品污染和有害因素风险监测工作手册》中方法,分离鉴定蜡样芽胞杆菌。结果 586份样品中,检出蜡样芽胞杆菌115份,总检出率为19.62%,其中2015年检出率最高(40.00%);食品以天水浆水检出率最高(40.00%),差异有统计学意义(χ2=21.92,P0.05);蜡样芽胞杆菌定量检测,菌落数小于100 cfu/g(ml)的占53.91%,100～1 000 cfu/g(ml)的占33.91%,1 000 cfu/g(ml)以上的占12.18%。结论甘肃省天水市食品中蜡样芽胞杆菌污染较严重;相关部门应加大食品卫生监管力度、加强从业人员培训、扩大健康教育宣传,确保食品安全。     

2019-2020年宁夏炭疽芽胞杆菌毒力鉴定及基因分型研究

目的 了解宁夏2019-2020年分离的炭疽芽胞杆菌菌株致病力及基因分型特征,为宁夏皮肤炭疽疫情判定与分子溯源提供实验室依据。方法 收集2019-2020年宁夏各地区分离的炭疽芽胞杆菌,对其进行毒力鉴定,并运用MLVA-15和canSNP分型技术进行基因分型研究。结果 2019-2020年宁夏分离到的炭疽芽胞杆菌均为强毒株,MLVA-15分型为同一种群,canSNP分型为A.Br.001/002组。结论 2019-2020年宁夏分离到的炭疽芽胞杆菌致病力较强,且菌株呈现相同的基因分型特征,提示菌株间存在流行病学关联。此研究结果填补了宁夏炭疽芽胞杆菌实验室检测中菌株致病力及基因分型的空白。     

2006-2016年贵州省炭疽芽胞杆菌SNR分型分析

目的 对贵州省2006-2016年分离的炭疽芽胞杆菌进行单核苷酸重复序列分型分析(SNR),了解菌株SNR型别特征,为炭疽疫情监测、调查与溯源提供技术手段和科学依据.方法 提取贵州省2006-2016年间不同地区的炭疽芽胞杆菌菌株基因组DNA,应用SNR各位点引物进行PCR扩增,将扩增产物进行毛细管电泳分析获得各位点序...     

市售婴幼儿食品蜡样芽胞杆菌污染状况调查

目的 了解甘肃省市售婴幼儿食品蜡样芽胞杆菌污染状况.方法 2018-2020年随机抽取甘肃省14个地(州、市)的百货商场、便利店/零售店、超市和网店等场所在售婴幼儿食品640份,应用平板计数法检测蜡样芽胞杆菌,以荧光PCR方法检测呕吐型基因.结果 640份样本中,蜡样芽胞杆菌总阳性率为15.00％(96/640),其中婴儿配方食品17.98％(41/228)、较大婴儿和幼儿配方食品18.64％(22/118)、婴幼儿谷类辅助食品11.22％(33/294);网店阳性率最高26.04％(25/96),呕吐型蜡样芽胞杆菌阳性率为6.25％(6/96);定量结果大于100 cfu/g的阳性样本占16.67％(16/96).结论 甘肃省市售婴幼儿食品存在蜡样芽胞杆菌污染,有潜在食品安全隐患,建议相关监管部门严格监督检查.     

贵州省2006-2011年炭疽芽胞杆菌检出情况与致病性研究

目的了解贵州省2006—2011年炭疽芽胞杆菌感染和分布情况,为贵州省炭疽疫情的预防控制和炭疽病09分子流行病学研究提供科学依据。方法对来自贵州省2006—2011年不同地区09830份疑似炭疽标本（外环境标本667份、患者标本151份和牲畜标本12份）,采用传统的革兰染色镜检、普通营养琼脂平板和血琼脂平板培养基分离培养炭疽芽胞杆菌,运用青霉素抑制试验和噬菌体裂解试验对可疑炭疽芽胞杆菌菌落进行鉴定。采用Real—time PCR技术检测88株经传统细菌学方法鉴定为炭疽芽胞杆菌菌株pX01质粒上的PA基因和pX02质粒上的CAP基因。结果从830份标本中分离出88株炭疽芽胞杆菌,总检出率为10．60％。2007年分离出炭疽杆菌的阳性标本最多,占36．36％;其次为2009年,占29．55％。阳性标本主要分布在黔西南州,其次为毕节地区和黔南州;册亨县、织金县和望谟县为炭疽杆菌检出数较多的监测县。88株炭疽芽胞杆菌CAP基因均为阳性。除2007年2株炭疽菌株PA基因为阴性外,其余86株PA基因均为阳性。结论贵州省炭疽疫源地面积广大,污染严重;检出的88株炭疽芽胞杆菌中97．73％的菌株同时具有两种毒力质粒,具有强致病性;该研究结果对贵州省炭疽疫情的预防控制及分子流行病学研究具有重要意义。     

蜡样芽胞杆菌溶血性肠毒素的提取及生物学活性分析

蜡样芽胞杆菌是国内引起细菌性食物中毒的常见细菌之一, 提取其溶血性肠毒素有助于阐明它的发病机理,有可能制备诊断试剂, 从而达到预防和控制蜡样芽胞杆菌食物中毒的目的。从国内引起食物中毒的１００ 株蜡样芽胞杆菌中,选出试验用菌株。从培养后的上清液中, 经过盐析、离子交换柱层析、制备性凝胶电泳提取蜡样芽胞杆菌溶血素。溶血素由 Ｂ、 Ｌ１ 和 Ｌ２ ３ 种成份组成, 分子量分别为３５ 、３６ 和４５ｋ Ｄａ ３ 种成份的协同作用在血琼脂上引起靶状溶血, 使兔皮肤血管通透性增加, 兔小肠肠段结扎产生积液反应, Ｖｅｒｏ 细胞形态学改变。提示蜡样芽胞杆菌溶血素具有肠毒素的性质, 试验也证实所提取的溶血素有免疫原性和免疫反应性     

辽宁省炭疽芽胞杆菌MLVA分型研究

目的 了解辽宁地区炭疽芽胞杆菌的流行特征及菌型基因特征。方法 通过多位点可变数目串联重复序列(Multiple locus variable numbers of tandem repeats analysis,MLVA)分型实验,对2001—2011年辽宁省分离到的6株炭疽芽胞杆菌分离株DNA进行检测,DNA指纹图谱使用BioNumerics 4.0 软件进行统计分析,得出聚类分析结果。结果 聚类分析发现,6株炭疽芽胞杆菌株可分为2个基因型。对于炭疽暴发而言,其可变数目串联重复序列遗传标记具有高度相似性。结论 炭疽芽胞杆菌基因组中的串联重复序列可作为炭疽芽胞杆菌基因分型的指标,在炭疽暴发事件中的病原体溯源上具有重要的意义。     

蜡样芽孢杆菌食物中毒的研究进展

蜡样芽孢杆菌是芽孢杆菌属的一种,会引起食物中毒,因此与人类关系密切。本文概述了蜡样芽孢杆菌的病原学特征、致病性及其引起食物中毒的流行病学特征,以提出科学的防控措施来有效控制该菌在食品中的污染,保护公众健康。     

Fatal Bacillus cereus sepsis following resolving neutropenic enterocolitis during the treatment of acute leukemia

Bacillus cereus is increasingly being acknowledged as a serious bacterial pathogen in immunosuppressed hosts. We report a case of fatal B. cereus sepsis in a patient with newly diagnosed acute leukemia following resolving neutropenic enterocolitis. Gastrointestinal complaints are common during induction chemotherapy, yet some antimicrobial coverage suitable for generalized neutropenia is not optimal for the eradication of B. cereus. This case demonstrates that, in the neutropenic patient with gastrointestinal complaints or in the setting of resolving neutropenic enterocolitis, it is important to anticipate possible B. cereus infection and sepsis.     

眼源性蜡样芽孢杆菌vrrA基因型及其与病情和预后关系

目的建立PCR检测眼源性蜡样芽孢杆菌,了解不同vrrA基因型蜡样芽孢杆菌感染与临床病情和预后关系。方法选择vrrA为靶基因设计引物,建立检测蜡样芽胞杆菌PCR。PCR产物用琼脂糖凝胶电泳检测并进行序列测定。采用Clustal 软件对获得的vrrA基因序列进行分型。对不同vrrA基因型蜡样芽胞杆菌感染与眼内炎患者病情严重程度及转归分析与比较。结果所建立的PCR可有效检测眼源性蜡样芽胞杆菌并有较高的敏感性和特异性。5株分离自眼内炎患者标本中的蜡样芽胞杆菌可分为MT1、MT2、MT3三种vrrA基因型,其中MT1、MT2型各2株,MT3型1株。MT1和MT2型蜡样芽胞杆菌感染性眼内炎病情重、预后差,MT3型蜡样芽胞杆菌感染性眼内炎病情较轻、预后较好。结论vrrA基因为靶基因的PCR可用于眼源性蜡样芽孢杆菌快速检测。不同蜡样芽孢杆菌vrrA基因型感染所致的眼内炎病情严重程度及转归有明显差异。     

A cluster of Bacillus cereus bacteremia cases among injection drug users

Bacillus cereus is a ubiquitous spore-forming organism that is infrequently implicated in extraintestinal infections. The authors report three cases of B cereus bacteremia among injection drug users presenting within one month to an urban tertiary care hospital. Treatment with intravenous vancomycin was successful in all three cases. While temporal association suggested an outbreak, molecular studies of patient isolates using pulsed-field gel electrophoresis did not suggest a common source. A review of the association of B cereus infections with heroin use and treatment of this pathogen is provided.     

Phospholipase C from Pseudomonas aeruginosa and Bacillus cereus:characterization of catalytic activity

Objective:To study characteristics of phospholipases C(PLCs),their importance for producing microorganisms us well us the potential of their use for industrial purposes.Methods:PLC from Bacillus cereus(B.cereus) D101 was selected as an example of Gram-positive PLCs and PLC from Pseudomanas aeruginosa(P.aeruginosa) D183 of Gram-negative ones.Enzymes were partially purified by ammonium sulfate precipitation followed by membrane dialysis.Partially purified preparations were used to study effect of different factors on activities as well as in substrate specificity tests which were conducted using a turbidimetric assay method.Results:Maximum activity was at pH 7 and 8 and 40 ℃ for P.aeruginosa PLC,and pH 8-10 and 37 ℃ for B.cereus PLC.Both PLCs were inhibited by Pi at 5 mM or higher,whereas,PLC from B.cereus only was inhibited by EDTA.Activity of P.aeruginosa PLC was not affected by removing Zn~(2+) ions from reaction mixture or their replacement with Ca~(2+),Ba~(2+),Mg~(2+) or Mn~(2+)ions.Vis-a-vis,activity of B.cereus PLC was found to be metal ion dependent PLCs from both isolates were relatively thermostable and showed maximum affinity toward phosphatidylcholine.Sphingomyelin and phosphatidylethanolamine were not good substrates and phosphatidylinositol,phosphatidylserine,phosphatidylglycerol and cardiolipin could be considered nonsubstrates.Conclusions:Human body physiological conditions could favor activity of P.aeruginosa and B.cereus PLCs.These enzymes may participate in phosphate scavenging and virulence of producing isolates but not in autolysis.PLCs from both isolates are potential candidates for industrial use.     

Novel Bacillus-Infecting Bacteriophage B13—The Founding Member of the Proposed New Genus Bunatrivirus

In this work, we describe a novel temperate bacteriophage, Bacillus phage B13. Bacillus-infecting phages are widespread and abundant, though often overlooked including because of their temperate lifestyle. B13 was isolated from its bacterial host via mitomycin C induction. Its host range was determined, and its pH and thermal stability were evaluated. The whole genome of B13 was sequenced and annotated. The genome is 36,864 bp long and contains 53 genes. The tail genes of B13 suggest that the phage has a siphovirus morphotype. It was found both in vitro and in silico that the phage uses the 3′-cos DNA packaging strategy, and the phage genome termini were located. Comparative analyses revealed that B13 has no close relatives and should therefore be assigned to a new viral genus, for which we propose the name Bunatrivirus.     

Identification and Characterization of a New Type of Holin-Endolysin Lysis Cassette in Acidovorax oryzae Phage AP1

Phages utilize lysis systems to allow the release of newly assembled viral particles that kill the bacterial host. This is also the case for phage AP1, which infects the rice pathogen Acidovorax oryzae. However, how lysis occurs on a molecular level is currently unknown. We performed in silico bioinformatics analyses, which indicated that the lysis cassette contains a holin (HolAP) and endolysin (LysAP), which are encoded by two adjacent genes. Recombinant expression of LysAP caused Escherichia coli lysis, while HolAP arrested growth. Co-expression of both proteins resulted in enhanced lysis activity compared to the individual proteins alone. Interestingly, LysAP contains a C-terminal region transmembrane domain, which is different from most known endolysins where a N-terminal hydrophobic region is found, with the potential to insert into the membrane. We show that the C-terminal transmembrane domain is crucial for protein localization and bacterial lysis in phage AP1. Our study characterizes the new phage lysis cassette and the mechanism to induce cell disruption, giving new insight in the understanding of phage life cycles.     

Coevolutionary phage training leads to greater bacterial suppression and delays the evolution of phage resistance

The evolution of antibiotic-resistant bacteria threatens to become the leading cause of worldwide mortality. This crisis has renewed interest in the practice of phage therapy. Yet, bacteria’s capacity to evolve resistance may debilitate this therapy as well. To combat the evolution of phage resistance and improve treatment outcomes, many suggest leveraging phages’ ability to counter resistance by evolving phages on target hosts before using them in therapy (phage training). We found that in vitro, λtrn, a phage trained for 28 d, suppressed bacteria ∼1,000-fold for three to eight times longer than its untrained ancestor. Prolonged suppression was due to a delay in the evolution of resistance caused by several factors. Mutations that confer resistance to λtrn are ∼100× less common, and while the target bacterium can evolve complete resistance to the untrained phage in a single step, multiple mutations are required to evolve complete resistance to λtrn. Mutations that confer resistance to λtrn are more costly than mutations for untrained phage resistance. Furthermore, when resistance does evolve, λtrn is better able to suppress these forms of resistance. One way that λtrn improved was through recombination with a gene in a defunct prophage in the host genome, which doubled phage fitness. This transfer of information from the host genome is an unexpected but highly efficient mode of training phage. Lastly, we found that many other independently trained λ phages were able to suppress bacterial populations, supporting the important role training could play during phage therapeutic development.

In 30 y, the World Health Organization predicts that antibiotic-resistant bacteria will kill over 10 million people each year—more deaths than are caused by cancer (1). This health crisis, in part caused by the heavy and often inappropriate way we use antibiotic drugs, has led to the spread of resistance genes through clinical, agricultural, and natural environments and to the emergence of multidrug-resistant (MDR) “superbugs” that are untreatable due to their resistance against all available classes of antibiotics (2–4). As bacteria continue to outpace our discovery and development of new drugs, the evolution of resistance threatens to return us to a preantibiotic era of infectious disease (5, 6).This crisis has renewed interest in the century-old practice of phage therapy: the use of phages, viruses that infect bacteria, to treat bacterial infections (7–11). Recently, phage therapy has shown promise in cases where drugs of last resort fail to treat life-threatening MDR bacterial infections (9–13). However, even in successful cases, the evolution of phage resistance poses a considerable threat to the efficacy of treatment (9, 12, 14). For example, in 2016, at the University of California San Diego, a patient with acute pancreatitis complicated by an MDR Acinetobacter baumannii infection was treated with two four-phage mixtures that suppressed the pathogen in vitro (9). Within 8 d, A. baumannii isolated from the patient was resistant to all eight phages used. Fortunately, the infection resolved following delivery of a ninth phage, and the patient survived. This case is representative of numerous phage therapy studies (9–12, 14). A metanalysis in 2018 reported that phage resistance evolved in 82% of animal gut decolonization studies, 50% of meningitis/sepsis models, and 75% of human clinical cases in which the evolution of resistance was monitored (14). These observations of rapid phage resistance evolution in therapy mirror decades of basic research in the laboratory; mutations that confer resistance to phages are often as common as those for antibiotic resistance (15–17). Furthermore, many of these resistance mutations confer cross-resistance to multiple phages (18).Although resistance to phages is as or more common than to antibiotics, potential advantages of using phages as therapeutics have been proposed time and again (7, 8, 19–22). Notably, unlike antibiotics, phages are biological entities that evolve. By reciprocally adapting to changes in their hosts (coevolution), phages have maintained the ability to infect their hosts for millennia. Many have proposed harnessing this inherent evolutionary potential by preemptively coevolving phages with target bacterial prey (22–24). Proponents of this “phage training” approach suggest that, by experiencing the ways their host can evolve resistance, trained phages will evolve to counter host defenses. Then, trained phages “from the future” can be used to trap the ancestral, uncoevolved bacteria “from their past” that are infecting the patient, making their evolution futile.While the idea of phage training is enticing, it has not yet been adopted for therapy. Contrasting theories of bacteria–phage coevolutionary dynamics make the success of phage training uncertain (12, 24, 25). According to some conceptual models of coevolution (e.g., matching alleles), as phages adapt to their evolving host, they lose the ability to infect past hosts (24). In such cases, phage training would not work because trained phages would lose the ability to infect the original target bacterium. Alternatively, other models of coevolution (e.g., gene for gene and arms race dynamics) argue that as phages adapt to their evolving host, they maintain the ability to infect their original host (24). In this scenario, training would expand phage host range to encompass both original and contemporary bacteria. Regardless of how coevolution affects host range, some opponents of phage training contend that the use of trained phages will apply stronger selection on target bacteria which will accelerate the evolution of resistance and loss of therapeutic efficacy (22).In this study, we conducted a coevolution experiment using Escherichia coli and either untrained or trained phages to evaluate the potential of phage training for therapy. By comparing the population dynamics of coevolving bacteria and phages, we find that trained phages suppress the target bacteria more strongly and for longer than untrained phages. Through post hoc analyses on the bacteria and phages that evolved in our experiment, we identify the factors that allowed trained phages to suppress host populations and delay the evolution of resistance.     

Meningitis due to Bacillus cereus: A case report and review of the literature

Bacillus cereus is infrequently associated with invasive central nervous system (CNS) disease. Infection is associated with conditions that lead to reduced host immunity and provide direct access to the CNS, such as spinal anesthesia and ventricular tubes and shunts. A case of ventriculitis secondary to B cereus in a patient receiving intrathecal chemotherapy is reported, along with a review of the current literature. B cereus can colonize medical devices, thus posing a risk for invasive disease. Despite aggressive treatment with broad-spectrum anti-infectives, the mortality of CNS invasive B cereus is high. Clinicians should not dismiss Gram-positive rods resembling Bacillus species from normally sterile sites as contaminants in critically ill patients. Appropriate antibiotic therapy should be promptly initiated to limit morbidity and mortality.