Background Enterococcus cecorum (EC) infection currently is one of the most important bacterial diseases of modern broiler chickens but can also affect ducks or other avian species. However, little is known concerning pathogenesis of EC and most studies concentrate on examinations of EC strains from broilers only. The objective of this study was to compare pathogenic and commensal EC strains from different animal species concerning different phenotypic and genotypic traits.ResultsPathogenic and commensal EC strains were not clearly separated from each other in a phylogenetic tree based on partial sequences of the 16S-rRNA-gene and also based on the fatty acid profile determined with gas chromatography. C12:0, C14:0, C15:0, C16:0, C17:0, C18:0, C18:1 w7c, C18:1 w9c and C20:4 w6,9,12,15c were detected as the major fatty acids. None of the 21 pathogenic EC strains was able to utilize mannitol, while 9 of 29 commensal strains were mannitol positive. In a dendrogram based on MALDI-TOF MS data, pathogenic strains were not clearly separated from commensal isolates. However, significant differences concerning the prevalence of several mass peaks were confirmed between the two groups. Two different antisera were produced but none of the serotypes was predominantly found in the pathogenic or commensal EC isolates. Enterococcal virulence factors gelE, esp, asa1, ccf, hyl and efaAfs were only detected in single isolates via PCR. No virulence factor was found significantly more often in the pathogenic isolates. The chicken embryo lethality of the examined EC isolates varied from 0 up to 100%. The mean embryo lethality in the pathogenic EC isolates was 39.7%, which was significantly higher than the lethality of the commensal strains, which was 18.9%. Additionally, five of the commensal isolates showed small colony variant growth, which was never reported for EC before.ConclusionsPathogenic and commensal EC isolates from different animal species varied in chicken embryo lethality, in their ability to metabolize mannitol and probably showed divergent mass peak patterns with MALDI-TOF MS. These differences may be explained by a separate evolution of pathogenic EC isolates. Furthermore, different serotypes of EC were demonstrated for the first time.

A total of 199 Riemerella anatipestifer (RA) and RA-like field strains isolated culturally from birds of 12 different species and from pigs were characterized using classical phenotypic and chemotaxonomic tests. The RA reference strain ATCC 11845 was included in the study. On the basis of the classical phenotypic characteristics studied and the numerical analysis of the whole-cell fatty acid patterns, the RA reference strain and 123 field isolates were assigned to the indole negative (IN) variant and 10 isolates to the indole positive (IP) variant of the species RA. The IN strains were isolated not only from poultry and free-living wild ducks, but also from pigs, guillemots and from a budgerigar and a herring gull. All the IP isolates were isolated from domestic ducks. One field strain from a chicken and one from a black-headed gull, which were distinguished from RA mainly by the negative a-glucosidase reaction and production of yellow pigment respectively, showed fatty acid methyl ester profiles chemotaxometrically different from those of RA. Another 64 field strains isolated from domesticated ducks, geese and muscovy ducks with signs and lesions very similar to those caused by RA were phenotypically and chemotaxometrically clearly different from RA and could not be classified to any of the known species. This possible bacterial pathogen is therefore given the preliminary designation of Riemerella-like (RA-L) taxon 1502.

~Twenty-four strains isolated mainly from infected respiratory tracts of pigeons were characterized by an integrated genotypic and phenotypic approach. An extensive biochemical examination using conventional tests and several API microtest systems indicated that all isolates formed a phenotypically homogeneous taxon with a DNA G+C content between 42 and 43 mol%. Whole-cell protein and fatty acid analysis revealed an unexpected heterogeneity which was confirmed by DNA-DNA hybridizations. Four main genotypic sub-groups (genomovars) were delineated. 165 rDNA sequence analysis of a representative strain indicated that this taxon belongs to the beta-subclass of the Proteobacteria with Taylorella equigenitalis as its closest neighbour (about 94.8% similarity). A comparison of phenotypic and genotypic characteristics of both taxa suggested that the pigeon isolates represented a novel genus for which the name Pelistega is proposed. In the absence of differential phenotypic characteristics between the genomovars, it was preferred to include all of the isolates into a single species, Pelistega europaea, and strain LMG 10982 was selected as the type strain. The latter strain belongs to fatty acid cluster I and protein electrophoretic sub-group 1 , which comprise 13 and 5 isolates, respectively. It is not unlikely that the name P. eumpaea will be restricted in the future to organisms belonging to fatty acid cluster I , or even to protein electrophoretic sub-group 1 , upon discovery of differential diagnostic features.

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A total of 44 bacterial strains obtained from 49 clinically healthy ducklings of different ages originating from four different farms were identified as members of the species Riemerella anatipestifer (RA) using conventional biochemical test methods. Numerical analysis of the whole-cell fatty acid patterns of these isolates resulted in two different clusters, one of which showed a similar pattern to that of the type strain of RA. Strains having a different fatty acid methyl esters (FAME)-profile (cluster II) were designated R. anatipestifer-like (RA-like). Sequencing of 16S rRNA genes of RA-like field isolates revealed 99% identity to RA. The significance of these observations are discussed. The present findings document for the first time that RA seems to represent a normal part of the pharyngeal flora of healthy Pekin ducks.