Isolation of Histamine-Producing Bacteria from Fish-Processing Facilities and FishingVessels

Abstract

The presence of histamine-forming bacteria in fishprocessing facilities was studied. Environmental sampling was conducted in the Hampton Roads area of Virginia in fishprocessing facilities that regularly handle scombroid fish or other fish which are known to potentially accumulate histamine levels greater than 50 ppm. Surfaces that come into contact with the fish were swabbed and the histamine-forming isolates from these areas were identified. One isolate each of Klebsiella ozaenaeand Vibrio alginolyticus, and two isolates of Aeromonassp. were found in the processing facilities. The study concluded that histamine-forming bacteria do not comprise a large part of the microflor a associated with fishprocessing facilities. Fishing vessels were also sampled and no histamine-forming bacteria were identified.     

弗兰克氏菌nifH及nifD基因的定位

利用限制性内切酶酶切和分子杂交等手段,对弗兰克氏菌菌株At4和Hr16的固氮基因克隆的nifH(pPC1201)、nifD(pPC1202)及nifK(pPC1203)基因为探针杂交,定位了At4和Hr16的nifH和nifD基因。同时发现,一条1.3kb的BamHI片段丢失。     

Fatal suppurative meningoencephalitis caused by Klebsiella pneumoniae in two calves

One calf died (No. 1) and another was euthanized following astasia (No. 2). Histopathological examination revealed suppurative meningoencephalitis in these calves. Klebsiella pneumoniae antigens were detected in lesions. Thymocytes were decreased in the thymus cortex in both cases. 16S rRNA gene sequencing of the No. 1 isolate and bacterial extracts from formalin fixed paraffin embedded sections of No. 2 revealed that both samples were K. pneumoniae. The No. 1 isolate showed multidrug resistance against penicillin antibiotics, fosfomycin, streptomycin, macrolide antibiotics, tetracycline antibiotics, and clindamycin. Immunosuppression is a significant septicemic K. pneumoniae infection risk factor. Our study provides new aspects regarding K. pneumoniae infections in cattle, bacterial meningoencephalitis differentiation, and K. pneumoniae and bacterial meningoencephalitis treatments.     

诃子提取物对3种致病菌的体外抑菌效果及其机制研究

为探究诃子在畜禽疫病防控中的作用及应用潜力，以大肠埃希菌、肺炎克雷伯菌和阴沟肠杆菌3种常见致病菌为对象，对比诃子和其他11种中药提取物的抑菌圈直径和最小抑菌浓度（MIC），分析诃子培养上清液的总漏出率和电导率、蛋白浓度及诃子对细菌DNA和蛋白含量的影响。结果显示：诃子比其他11种中药的抑菌效果更强，表现为抑菌圈直径更大，MIC更低。培养上清液的电导率和漏出率增加，用2倍MIC诃子药液处理8 h后，大肠埃希菌和肺炎克雷伯菌上清液蛋白浓度显著增加（P<0.05）。诃子抑制大肠埃希菌蛋白合成，使分子质量约为80 ku的蛋白缺失；对肺炎克雷伯菌和阴沟肠杆菌蛋白质合成影响不明显，对细菌DNA也没有明显的凝胶阻滞作用，但能降解DNA。以上结果表明：诃子具有较好的抑菌效果，其作用机制是通过破坏细菌细胞膜通透性，抑制细菌核酸和蛋白合成而发挥抑菌作用。     

Effects of a Nitrogen-Fixing Indigenous Bacterium (Klebsiella pneumoniae) on the Growth and Development of the Halophyte Salicornia bigelovii as a New Crop for Saline Environments

Salicornia bigelovii is a novel crop for salty soils, which can contribute to arid‐zone management where irrigation with salty water, including sea water, is now a necessity. Nitrogen fixation by bacteria associated with the roots of S. bigelovii and similar halophytes is an important source of available nitrogen in salt marsh ecosystems. However, the diversity of the rhizosphere of Salicornia is unknown. Five areas around the Bay of La Paz in Baja California Sur, Mexico were sampled to detect nitrogen‐fixing bacteria associated with this halophyte; from these, 18 colonies were isolated. Only one showed high acetylene reduction activity. This bacterium was identified as Klebsiella pneumoniae. The effects of K. pneumoniae were evaluated at the germination and early seedling growth stages of two genotypes of S. bigelovii (‘wild genotype’ and cultivar SOS‐10), as an alternative crop for semiarid and saline environments. This bacterium, in conjunction with Azospirillum halopraeferens, was tested for growth‐promoting ability when inoculated on S. bigelovii genotypes under various saline concentration conditions. During germination and early seedling growth, K. pneumoniae showed high specificity for the wild S. bigelovii genotype, while A. halopraeferens was more specific for the improved S. bigelovii genotype SOS‐10. This is the first report of K. pneumoniae as a nitrogen‐fixing bacterium associated with the oilseed S. bigelovii, a novel halophyte crop. A reliable biological method, based on beneficial bacteria, is suggested to help maintain or improve the fertility of soils sustaining Salicornia fields.     

Detection of bacteriuria and bacteremia in newborn calves by a catalase-based urine test

Background: Bacteremia occurs frequently in newborn calves. The predictive value of clinical signs is low, suggesting the use of calf‐side diagnostic tests. Objectives: To investigate testing of urine catalase activity (Uriscreen test) for bacteriuria and bacteremia detection. Animals: Five colostrum‐free calves and 3 colostrum‐fed control calves. Methods: Controlled experimental trial. Colostrum‐free calves were inoculated PO with Escherichia coli O78+. A clinical score was established to define the onset of the illness. Blood and urine (cystocentesis) samplings and cultures, and Uriscreen tests, were performed 4–6 times from inoculation to death. Three control calves received the same management as 3 inoculated calves, but with colostrum and without inoculation. Results: Bacteremia was demonstrated in all of the inoculated colostrum‐free calves and in none of the control calves. The E. coli O78+ strain, E. coli, and Klebsiella spp. were recovered from 4/5, 5/5, and 2/5 inoculated colostrum‐free calves, respectively. Urine cultures were negative for the 2 groups at the start of the experiment; 5/5 colostrum‐deprived inoculated calves were positive for E. coli thereafter whereas 3/3 controls remained negative. Concordance of Uriscreen tests with bacteremia and bacteriuria was 0.86 and 0.88, respectively. Kappa value of agreement between Uriscreen and bacteremia and bacteriuria was 0.73 and 0.76, respectively. Sensitivity of Uriscreen for bacteremia and bacteriuria was 80.0 and 86.6%, respectively, and specificity was 92.8 and 88.8%, respectively. Conclusions and Clinical Relevance: The results suggest that Uriscreen can be used for detection of bacteremia in neonatal calves in connection with a constant bacteriuria.     

一株七彩鸟肺炎克雷伯菌同时产TEM和SHV型β-内酰胺酶的基因型鉴定

用全自动细茵鉴定系统鉴定分离菌,用表型确证试验法检测超广谱β-内酰胺酶(ESBLs),并分别用TEM、SHV、CTX-M 3种特异性引物进行PCR扩增、基因克隆及测序分析,确定分离茵所产β-内酰胺酶的基因型和基因亚型.结果表明:分离茵为产ESBLs的肺炎克雷伯菌,具有多重耐药特性,其质粒上具有TEM序列和SHV序列,基因亚型分别TEM-1型和SHv-11型.     

桑细菌性枯萎病病原菌的分离鉴定与全基因组序列分析

为明确华南蚕区桑树细菌性枯萎病主要病原菌的种类,本研究从广西、广东等地桑园采集了多份桑树细菌性枯萎病病样,采用分离培养、形态学鉴定和分子生物学鉴定的方法,对病原菌进行了分离鉴定,并通过药敏试验分析病原菌的耐药性。结果表明,结合柯赫氏法则,将分离到的桑枯萎病病原菌鉴定为产酸克雷伯氏菌Klebsiella oxytoca,编号AKKL-001(菌种保藏号GDMCC No.1.1602)。该病原菌属革兰氏阴性菌,基因组全长6 149 586 bp,含有5 792个基因,GC含量55.80%;药敏试验结果表明,病原菌对氨苄西林、头孢唑啉、头孢呋辛、头孢噻吩、链霉素、麦迪霉素等抗生素具有耐受性。本研究报道了桑细菌性枯萎病病样上分离的产酸克雷伯氏菌,为桑细菌性枯萎病病原菌的研究提供理论依据,全基因组测序的结果为桑细菌性枯萎病的相关致病机制研究奠定了基础。     

患病黄额闭壳龟中产酸克雷伯菌的分离与鉴定

从患病黄额闭壳龟(Cuora galbinifrons)肝脏中分离到一株致病菌HE01,经人工感染健康巴西龟,可复制与自然发病相同的症状,且从人工感染病龟体内再次分离到相同的病原菌。经Biolog微生物自动鉴定系统的鉴定,以及进一步的16 S rDNA基因序列和系统发育分析都表明,此致病菌为产酸克雷伯菌(Klebsiella oxytoca)。药物敏感性试验表明,该菌株对头孢噻肟、头孢曲松、头孢哌酮等10种药物高度敏感。     

五指山猪肺炎克雷伯菌肺炎亚种的分离及鉴定

从发病猪场濒死的五指山小猪肝脏、脾脏、小肠中分离到3株革兰氏阴性杆菌,对分离菌株进行形态学、培养特性、生化特性和分子生物学鉴定,确定分离菌株为肺炎克雷伯菌肺炎亚种。利用细菌16S rRNA通用引物对3株细菌基因组DNA进行扩增,均可得到大小为1 503 bp的特异性片段,该序列与GenBank上已经登录的猪源肺炎克雷伯菌序列同源性达99%。动物毒性试验证明其对小鼠有较强的致病性。