Identifizierung und weitergehende Charakterisierung von ß-hämolysierenden Streptokokken, isoliert von Seehunden und Kegelrobben aus der deutschen Nord- und Ostsee
Abstract
The present study allowed an identification and further characterisation of 72 ß-haemolytic streptococci isolated from harbour seals and grey seals of the German North and Baltic Seas. As a result of cultural, biochemical, serological and also molecular methods 69 bacterial cultures could be identified as S. phocae and three cultures as S. dysgalactiae subsp. dysgalactiae Serovar L. This is the first evidence of the species S. phocae occurring in grey seals. Eight of the 69 S. phocae-cultures belonged to the serological group C and 61 cultures to the serological group F. Some typical biochemical properties of the S. phocae-cultures, investigated in the present study, were a positive fructose, D-mannose and ribose reaction as well as a missing reaction with lactose, salicin, sorbitol, trehalose, esculin, arginine and hippurate. A molecular characterisation of the S. phocae-isolates resulted from an amplification of the 16S ribosomal RNA-gene after sequencing. The amplicons were proven to be species specific using the restriction enzymes EarI and HincII. A second strategy for a PCR arranged species identification were the design of S. phocae-specific oligonucleotide primers in consideration of the S. phocae-specific V2-region. Using this species specific oligonucleotide primers a clear species affiliation of all 69 S. phocae-cultures as well as the S. phocae-reference cultures were possible. Further phaenotypic properties of most of the S. phocae-cultures were a long streptococci typical chain formation, growing as a cotton-granular sediment in fluid media with a simultaneously clear supernatant, compact growing in soft agar and an aggregation reaction in a 0,1 mol/l ammonium sulfate concentration. In addition the S. phocae-cultures were susceptible to most of the antibiotics investigated. DNA-fragment patterns of 66 S. phocae-cultures were created by macrorestriction analysis of chromosomal DNA of the bacterial cultures using pulsed-field gel electrophoresis. This resulted in 29 different DNA-fragment pattern. Predominantly there was no consistence of the DNA-fragment patterns realised. Consequently cross infections between particular animals seems to occur rarely. DNA-fingerprints" of the isolated S. dysgalactiae subsp. dysgalactiae Serovar L-cultures resulted in an obvious distinction of isolates from the North and Baltic Seas. Furthermore a group L-streptococci-North Sea-isolate, isolated from a harbour seal, showed a partial relationship to a comparatively investigated group L-streptococci-isolate from a harbour porpoise of the North Sea. The occurrence of both animal species in the same habitat might have caused a transmission of the group L-streptococci.
