Conserved regions about 420 bp long of the pelADE cluster specific to Erwinia chrysanthemi were amplified by PCR and used to differentiate 78 strains of E. chrysanthemi that were obtained from different hosts and geographical areas. No PCR products were obtained from DNA samples extracted from other pectinolytic and nonpectinolytic species and genera. The pel fragments amplified from the E. chrysanthemi strains studied were compared by performing a restriction fragment length polymorphism (RFLP) analysis. On the basis of similarity coefficients derived from the RFLP analysis, the strains were separated into 16 PCR RFLP patterns grouped in six clusters. These clusters appeared to be correlated with other infraspecific levels of E. chrysanthemi classification, such as pathovar and biovar, and occasionally with geographical origin. Moreover, the clusters correlated well with the polymorphism of pectate lyase and pectin methylesterase isoenzymes. While the pectin methylesterase profiles correlated with host monocot-dicot classification, the pectate lyase polymorphism might reflect the cell wall microdomains of the plants belonging to these classes.

16S and 23S rRNAs from Escherichia coli were used to study the relationship among a representative collection of strains of Erwinia chrysanthemi differing in their original host and geographical origin. Phenetic analysis of restriction fragment length polymorphisms allowed the distribution of the studied strains into seven clusters. These clusters were similar to those obtained by cladistic methods and appeared to correlate well with the established pathovars and biovars but to a lesser extent with geographical distribution. Except for two groups of strains defined as tropical and temperate isolates (clusters 3 and 4, respectively), our clustering correlated well with botanical classifications of host plants. However, the rRNA groupings were shown to be more discriminative than biovar analysis. To assess the relationship between rRNA clusters and pathogenicity, 12 representative strains from different clusters were tested for pathogenicity on different plants. The two typical symptoms, maceration and wilting, were observed for these strains. The occurrence of the tobacco

The virulence genotype profile and presence of a pathogenicity island(s) (PAI) were studied in 18 strains of F165-positive Escherichia coli originally isolated from diseased calves or piglets. On the basis of their adhesion phenotypes and genotypes, these extraintestinal pathogenic strains were classified into three groups. The F165 fimbrial complex consists of at least two serologically and genetically distinct fimbriae: F165 1 and F165 2 . F165 1 is encoded by the foo operon (pap-like), and F165 2 is encoded by fot (sfa related). Strains in group 1 were foo and fot positive, strains in group 2 were foo and afa positive, and strains in group 3 were foo positive only. The strains were tested for the presence of virulence genes found mainly in extraintestinal pathogenic E. coli (ExPEC) strains. Although all the strains were positive for the papA variant encoding F11 fimbriae incD, traT, and papC, the prevalence of virulence genes commonly found in PAIs associated with ExPEC strains was highly variable, with strains of group 2 harboring most of the virulence genes tested. papG allele III was detected in all strains in group 1 and in one strain in group 3. All other strains were negative for the known alleles encoding PapG adhesins. The association of virulence genes with tRNA genes was characterized in these strains by using pulsed-field gel electrophoresis and DNA hybridization. The insertion site of the foo operon was found at the pheU tRNA locus in 16 of the 18 strains and at the selC tRNA locus in the other 2 strains. Furthermore, 8 of the 18 strains harbored a high-pathogenicity island which was inserted in either the asnT or the asnV/U tRNA locus. These results suggest the presence of one or more PAIs in septicemic strains from animals and the association of the foo operon with at least one of these islands. F165-positive strains share certain virulence traits with ExPEC, and most of them are pathogenic in piglets, as tested in experimental infections.Escherichia coli is a frequent cause of intestinal and extraintestinal diseases in humans and animals. Typical extraintestinal infections include urinary tract infections, newborn meningitis, polyserositis, and septicemia. All these groups of pathogenic E. coli strains have been called extraintestinal pathogenic E. coli (ExPEC). The recognized virulence factors of ExPEC include diverse adhesins (e.g., P fimbriae, S/F1C fimbriae, F165 fimbriae, Afa/Dr adhesins, and type 1 fimbriae), toxins (e.g., hemolysin, cytotoxic necrotizing factor, and cytolethal distending toxin), surface antigens (e.g., group II and group III capsules and lipopolysaccharide), invasins (e.g., an invasin responsible for invasion of brain endothelium [IbeA, also called Ibe10]), iron uptake systems (e.g., the aerobactin system), and secretion systems (e.g., type III secretion systems). These virulence factors facilitate colonization and invasion of the host, avoidance or disruption of host defense mechanisms, injury to host tissues, and/or stimulation of a noxious host inflammatory response (...

gusz, D, 1997, Cloning of a full-length symbiotic hemoglobin cDNA and in situ localization of the corresponding mRNA in Casuarina giauca root nodule, -Physiol, Plant, 99:608-616,We have characterized a full-length cDNA (hb-Cg\¥) that represents symbiotic mRNA hemoglobin (hb) from Casuarina glauca root nodules. In situ hybridization was used to examine the correlation between hb-CgW mRNA and the state of the Frankia infection process. The efficiency of in situ hybridization using DIG-labeled vs ['^SJ-labeled probes was compared. The expression of hb-CgW gene is induced in young infected host cells prior to the detection of Frankia nifH mRNA, Since Frankia does not form vesicles in C, giauca nodules, it is proposed that Hb is necessary to reduce the O; concentration in the cytoplasm of the host cells before the nif genes are expressed.

Erwinia chrysanthemi pv dianthicola / œillet / enrichissement / Das-Elisa Summary — Detection of Erwinia chrysanthemi pv dianthicola (Ech) by the DAS-ELISA method in symptomless carnation cuttings. This method, using a polyclonal antiserum, the specificity of which was evaluated in this study, can detect up to 5 x 10 3 cfu.mL -1 . Different incubation conditions of carnation stem samples to be tested by DAS-ELISA were studied, in order to amplify the primary inoculum in weakly-infected symptomless samples. The aim was to increase the detection limits. The media LB and CVP, which ensure enrichment of Ech in samples, interfere with efficient antigen-antibody interaction. By contrast, incubation of samples in saline at 30 °C allows amplification without loss of antibody recognition. The exploitation of this method for routine analysis of carnation stem samples is discussed.E chrysanthemi pv dianthicola / carnation / enrichment / DAS-ELISA