Main topic : Animal Health
First description of Streptococcus ruminantium from diseased ruminants in France
PEGNE J. 1, THUILLIER B. 2, PLAINVERT C. 4, LE PIOUFFLE A. 2, BAYON-AUBOYER M. 3, DMYTRUK N. 4, FRIGO A. 4, POYART C. 4, TAZI A. 4, LEQUEUX G. 1
1 LABOCEA, FOUGERES, France; 2 LABOCEA, QUIMPER, France; 3 LABOCEA, PLOUFRAGAN, France; 4 CNR Streptocoques APHP-CUP, PARIS, France
Streptococcus suis, a major swine bacterial pathogen, has been frequently isolated from ruminants. Although its pathogenicity still remains unclear in ruminants, S. suis has been considered as the etiological agent in cases of pneumonias, arthritis and endocarditis (1). A new species described as Streptococcus ruminantium, previously S.suis serotype 33 (2) has been recently described in Japan (3) and Canada (4). To our best knowledge, isolation of Streptococcus ruminantium has never been described in France. This study describes for the first time the isolation of S. ruminantium from 16 diseased ruminants in France.
7 cases of clinical arthritis from young goats were detected by a veterinarian in a herd of 200 goats located in Eastern Brittany (France) in 2018. No mortality was reported. A joint sampled from a dead 15-day-old goat following necropsy at farm was submitted at LABOCEA for macroscopical examination and bacteriological investigation.
Alpha-hemolytic colonies in pure and abundant culture was isolated after 24 hours of incubation on Columbia Blood Agar. Colonies from Columbia Blood Agar showed following results in identification tests : Gram positive cocci, catalase -, Streptococus sp. by MALDI-TOF Mass Spectrometry (Biotyper, Bruker) : oralis (score 1.7), suis (1.69) or mitis (1.65). Further investigations at LABOCEA were conducted : S. suis (confidence scores 98 to 99.9 %) by MALDI-TOF Mass Spectrometry (VITEK MS, Biomérieux) and Api 20 Strep (Biomérieux), no agglutination with specific S. suis antisera (1 to 12) but a strain typed as S. suis serotype 33 by PCR (internal LABOCEA method). As S. suis serotype 33 was reclassified as S. ruminantium, the strain was sent to the Streptococcus National Reference Center (APHP-Paris) to confirm the identification to the species level. Sequencing of the sodA gene according confirmed a 99% homology with the reference sequence of S. ruminantium.
Further investigations : methods
The 15 available and non-redundant strains isolated since 2015 from ruminants (ovine, goats and cattle) and identified as S. suis but non-typable by antisera-agglutination at LABOCEA were sent to the Streptococcus National Reference Center for expertise : identification by VITEK 2 (Biomérieux), MALDI-TOF Mass Spectrometry (Biotyper, Bruker), sodA gene sequencing, antimicrobial susceptibility testing by disk-diffusion according to EUCAST recommendations and PCR identification of resistance determinants according to (5).
Further investigations : results
The 15 additional strains were all confirmed as S. ruminantium by sodA sequencing. Strains were isolated from various clinical presentations : arthritis, mastitis and respiratory infections. Strains were frequently resistant to tetracyclin and macrolides and mainly associated with tet(M), tet(O), erm(B) resistance genes.
In this study are described for the first time in France cases of isolation of confirmed Streptococcus ruminantium from clinical samples. Identification to the species level remains challenging without specific implementation of MALDI-TOF current commercial databases. As S. suis is considered as a zoonotic pathogen, further investigations would be necessary to clarify the potential zoonotic role of the closely related S. ruminantium species.