Abstract
Erysipelothrix rhusiopathiae infections re-emerged as a matter of great concern particularly in the poultry industry. In contrast to porcine isolates, molecular epidemiological traits of avian E. rhusiopathiae isolates are less well known. Thus, we aimed to (i) develop a multilocus sequence typing (MLST) scheme for E. rhusiopathiae, (ii) study the congruence of strain grouping based on pulsed-field gel electrophoresis (PFGE) and MLST, (iii) determine the diversity of the dominant immunogenic protein SpaA, and (iv) examine the distribution of genes putatively linked with virulence among field isolates from poultry (120), swine (24) and other hosts (21), including humans (3). Using seven housekeeping genes for MLST analysis we determined 72 sequence types (STs) among 165 isolates. This indicated an overall high diversity, though 34.5% of all isolates belonged to a single predominant ST-complex, STC9, which grouped strains from birds and mammals, including humans, together. PFGE revealed 58 different clusters and congruence with the sequence-based MLST-method was not common. Based on polymorphisms in the N-terminal hyper-variable region of SpaA the isolates were classified into five groups, which followed the phylogenetic background of the strains. More than 90% of the isolates harboured all 16 putative virulence genes tested and only intI, encoding an internalin-like protein, showed infrequent distribution. MLST data determined E. rhusiopathiae as weakly clonal species with limited host specificity. A common evolutionary origin of isolates as well as shared SpaA variants and virulence genotypes obtained from avian and mammalian hosts indicates common reservoirs, pathogenic pathways and immunogenic properties of the pathogen.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0216-x) contains supplementary material, which is available to authorized users.
Highlights
Erysipelothrix rhusiopathiae is a ubiquitous gram-positive bacterial organism which causes erysipelas in mammals and birds, especially in pigs and poultry
Multilocus sequence typing Allele sizes for the genes included for multilocus sequence typing (MLST) analysis of 165 E. rhusiopathiae strains ranged between 531 bp for ldhA to 640 bp for recA (Table 1)
Discussion there is an increasing notion of severe outbreaks of Erysipelas in poultry [10,22,47], possibly related to the ban of conventional cages within EU from 2012 and the large changes of housing systems due to welfare demands for laying hens [9,10,12], only little is known about the molecular epidemiology of avian E. rhusiopathiae isolates
Summary
Erysipelothrix rhusiopathiae is a ubiquitous gram-positive bacterial organism which causes erysipelas in mammals and birds, especially in pigs and poultry. Healthy pigs carrying E. rhusiopathiae in their lymphoid tissues have been suggested as a reservoir of the pathogen [1]. The genus Erysipelothrix contains two main species: E. rhusiopathiae (including serotypes 1a, 1b, 2, 4, 5, 6, 8, 9, 11, 12, 15, 16, 17, 19, and N) and E. tonsillarum (serotypes 3, 7, 10, 14, 20, and 23), the latter being isolated from apparently healthy swine and considered to be non-pathogenic [1,2,3,4]. E. rhusiopathiae was first recognized as a human pathogen causing localized cutaneous lesions, called erysipeloid, and sporadic cases of generalized cutaneous forms or septicaemia, often associated with endocarditis [2,5]. Following the change from conventional (battery) cage system to alternative housing systems, problems due to E. rhusiopathiae increased in laying hen [2,6,7,8,9,10,11,12]
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