Comparison of pathogenic and non-pathogenic Enterococcus cecorum strains from different animal species

Abstract

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.

Prevalence, antibiotic susceptibility and virulence factors of Enterococcus species in racing pigeons (Columba livia f. domestica)

“…A higher prevalence of gelE, asa1 and ace was in line with other studies concerning enterococci in farm animals [9,16] but not with the results for enterococci isolated from food-stuffs [26]. The lower detection rate of cylA and esp in racing pigeons was in near agreement with poultry isolates [9,16,27]. Incidences of esp detection in enterococci isolated from cattle and pigs were higher than in our study [16,27].…”

“…In this study we confirmed the presence of 6 different virulence genes in Enterococcus isolated from intestinal microbiota of racing pigeons. A higher prevalence of gelE, asa1 and ace was in line with other studies concerning enterococci in farm animals [9,16] but not with the results for enterococci isolated from food-stuffs [26]. The lower detection rate of cylA and esp in racing pigeons was in near agreement with poultry isolates [9,16,27].…”

“…Interestingly, among the known Enterococcus species, only E. cecorum was described as the cause of enterococcal infections in racing pigeons [6,7]. Recently, E. cecorum commonly considered as a part of physiologic intestinal microbiota of animals, has grown into one of the leading bacterial cause of lameness in broiler chickens [7][8][9]24]. Similarly to Zigo et al [22] E. mundtii was a rarely identified in racing pigeons.…”

“…In contrast to pigeon, hyl was often reported in human, wild bird, food and water isolates [13,15,24,28]. Jung et al [9] found hyl among single pathogenic E. cecorum from poultry.…”

“…Although enterococci are usually thought to be harmless commensals, they can also act as opportunistic pathogens. In recent years, their increased role has been noted in poultry and pigeon pathology [6][7][8][9]. According to the literature the drug-resistance of the bacteria isolated from pigeons may be very high [4,10].…”