Calcium inhibition of efrotomycin production byNocardia lactamdurans

Summary Efrotomycin is a modified polyketide antibiotic of the elfamycin family that has use in the area of pig husbandry. Optimization of the fermentation medium for production of efrotomycin byNocardia lactamdurans revealed that the fermentation is sensitive to hard water and certain lots of cottonseed flour used to prepare a complex fermentation medium. A limited metal ion analysis of the hard water indicated that calcium ions are present at concentrations found to be inhibitory by the addition of calcium chloride to medium prepared with distilled water. Similarly, a correlation between lots of cottonseed flour that poorly supported the fermentation and high calcium levels is presented. Further experimentation revealed that by altering the sterilization conditions of the cottonseed flour, the inhibitory effect of poor lots could be prevented.     

Genetic recombination by protoplast fusion inNocardia asteroides

Summary Fusion and regeneration of protoplasts ofNocardia asteroides strains ATCC 3318, IMRU W3599 and HIK B971 have been used to study genetic recombination in this species. Protoplasts were produced by treatment with lysozyme, following incubation with glycine. Mutants of ATCC 3318 were grown in peptone yeast extract medium at 32°C prior to protoplast production to maximize protoplast frequency, whereas mutants of IMRU W3599 and HIK B971 were grown in trypticase-soy broth. Glycine concentrations favoring protoplast formation varied from 1.5% to 5% depending on strain. For all strains, protoplast formation was complete 1 h after addition of 5 mg/ml lysozyme. Protoplasts were fused by addition of 50% polyethylene glycol-1000. In general, 25% of the protoplasts could be regenerated. The incidence of recombinant recovery was increased up to 750-fold. The distribution of recombinant phenotypes in matings was similar for protoplast fusion and conventional crosses.     

Nocardiosis in Mediterranean bivalves: First detection of Nocardia crassostreae in a new host Mytilus galloprovincialis and in Ostrea edulis from the Gulf of Naples (Italy)

In this work M. galloprovincialis and O. edulis specimens were surveyed for a pathological study in the Gulf of Naples (Mediterranean sea, Campania Region, southern Italy). Clusters of Nocardia sp.-like cells were observed in histological slides. PCR amplification, sequencing and in situ hybridization were carried out in order to corroborate Nocardia species identification for both hosts. Blast results showed a 99% of maximum identity with Nocardia crassostreae sequences in Genbank. This is the first report of N. crassostreae in the new host M. galloprovincialis and, in a new area, the Mediterranean Sea.     

诺卡氏菌烈性噬菌体vB_Ncarnea_KYD1的分离纯化与基因组分析

【背景】诺卡氏菌是一种广泛分布的好氧放线菌,可在人体内引起局部或播散性感染,尤其是在免疫功能低下的个体中。诺卡氏菌感染在临床上较难鉴定,而且不断有新型诺卡氏菌种被发现。不同类型、不同地域的诺卡氏菌具有流行差异和抗生素敏感性差异,阻碍了适当治疗方式的选择。利用病灶处的宿主菌分离得到噬菌体来控制诺卡氏菌感染的这种方法在近年来受到了各界的关注。【目的】尝试从环境中分离出能够用于临床治疗的针对诺卡氏菌的烈性噬菌体,并研究其基因组学特征。【方法】利用双层平板法分离得到目标噬菌体,观察其噬菌斑形态,并对噬菌体进行分离纯化,在透射电镜下鉴定其特征。提取噬菌体DNA进行全基因组测序与注释,并与数据库内已知噬菌体基因组进行比较,同时构建系统进化树以进行遗传进化分析。【结果】本文以肉色诺卡氏菌为宿主,从环境样本中分离出一株烈性噬菌体vB_Ncarnea_KYD1,在双层平板上可形成直径<2 mm的透亮均匀的噬菌斑。基因组分析表明,vB_Ncarnea_KYD1DNA为环状,大小为66 621 bp,共发现102个蛋白质编码区(coding sequence,CDS)及一个tRNA-Ser编码序列。透射电镜观察与系统进化树综合分析可以确定,vB_Ncarnea_KYD1为长尾噬菌体科的一个新属。其在进化过程中经历了复杂的基因重组过程。暂未发现毒力因子相关基因与抗性基因,具备实用价值。【结论】从环境水体中分离出一株烈性肉色诺卡氏菌噬菌体vB_Ncarnea_KYD1,通过电镜观察与基因组分析可知,此株噬菌体为长尾噬菌体,基因组中暂未发现不利于临床应用的相关基因,是一株相对安全的烈性诺卡氏菌噬菌体。研究结果丰富了国内噬菌体资源库,并为后续诺卡氏菌感染疾病的治疗提供支持。     

A case of amniotic membrane transplantation in non-healing Nocardia asteroides keratitis

A patient with severe non-healing microscopically proven Nocardia keratitis was treated with maximal topical amikacin followed by amniotic membrane transplantation (AMT) 2 months later (single-layer epithelial side-down). Epithelial healing was achieved, but neovascularization continued. This case report indicates that AMT combined with topical antibiotic provides pain relief and allows epithelial healing in severe Nocardia keratitis.     

Characterization of Nocardia plasmid pXT107

Nocardia,Rhodococcus and Streptomyces,all members of the actinomycetes family,areGram-positive eubacteria with high G C content and able to form mycelium.We report here a newlyidentified plasmid pXT107 of Nocardia sp.107,one of the smallest circular plasmids found in Nocardia.The complete nucleotide sequence of pXT107 consisted of 4335 bp with 65% G C content,and encodedone replication extragenic palindromic (Rep) and six hypothetical proteins.The Rep,double-strand originand single-strand origin of pXT 107 resembled those of typical rolling-circle-replication plasmids,such aspNI100 of Nocardia,pRE8424 of Rhodococcus and pIJ101 of Streptomyces.The Escherichia coli-Nocardiashuttle plasmid pHAQ22,containing the rep gene of pXT107,is able to propagate in Nocardia but not inStreptomyces.     

Immunogenicity and biophysical properties of a Nocardia brasiliensis protease involved in pathogenesis of mycetoma

We isolated and purified to homogeneity a caseinolytic protease from a Nocardia brasiliensis cell extract. Preparative polyacrylamide gel electrophoresis and electroelution were employed for purification. This purified protease was injected in BALB/c mice and induced IgM and IgG anti-protease antibodies. Active immunization of mice with this protease prevented mycetoma development in experimentally infected animals. Passive immunization with hyperimmune sera containing a high anti-protease antibody titer conferred partial but transient protection when collected 30 days after donor's immunization. The protective effect of hyperimmune sera was lost when obtained from donors after 60 days from their immunization despite its higher anti-protease antibody concentration. Cytokines are good candidates to explain these findings.     

Antimicrobial susceptibilities of strains of Nocardia brasiliensis isolated from soil of Tucumán

The activity of antimicrobial agents against soil isolates of N. brasiliensis was studied by determination of the minimum inhibitory concentrations (MICs) and disk diffusion technique, according to the National Committee for Clinical Laboratory Standards (NCCLS). The objectives were: (a) to study the patterns of sensitivity among regional strains of N. brasiliensis isolated from natural sources (soil) of different zones of Tucumán province; (b) to correlate these results with those previously obtained with regional strains of N. brasiliensis isolated from human mycetomas, as a contribution in the evaluation of the importance of the natural reservoir area of the potentially pathogen strains. The results obtained by both methods identified strains of N. brasiliensis from soils with similar patterns of susceptibility to the strains N. brasiliensis isolated from human mycetomas. This showed strains sensitive and resistant to antibiotics. The majority of the isolates of N. brasiliensis from soils showed higher susceptibilities to antibiotics than the strains isolated from human mycetomas. Among the antibiotics studied, cefotaxime, ceftriaxone and gentamicin were the most effective against all the regional strains tested, and these results are correlated with those obtained with regional strains that cause human mycetomas. This revised version was published online in June 2006 with corrections to the Cover Date.     

A phylogeny of the genus Nocardia deduced from the analysis of small-subunit ribosomal DNA sequences, including transfer of Nocardia amarae to the genus Gordona as Gordona amarae comb. nov.

Abstract According to phylogenetic analyses of nearly complete small-subunit ribosomal DNA sequences, the genus Nocardia should not comprise the two species Nocardia petroleophila and Nocardia amarae. N. amarae should be reassigned to the genus Gordona as Gordona amarae . All of the other Nocardia species form a monophyletic unit, closely related to species of the genus Rhodococcus . It is proposed to revive the name 'CMN' to comprise the genera Corynebacterium, Tsukamurella, Mycobacterium, Gordona, Rhodococcus and Nocardia that form a well identified and monophyletic unit. They are all characterized by a cell wall chemotype IV with mycolic acids.