Abstract:A marine bacterium associated with soft coral Sinularia polydactyla collected from Bandengan water, Jepara, North Java Sea, Indonesia, was successfully screened for antibacterial activity against pathogenic bacterium Streptococcus equi subsp. zooepidemicus K6. 72 isolated from infected monkey of the island of Bali and identified based on morphological, biochemical and molecular methods. Marine bacterium was identified as Pseudomonas sp. based on its 16S rDNA and was found to amplify gene fragments of Non-ribosomal peptide synthetase (NRPS). Cloning and subsequent sequencing, a 360 bp long DNA fragment was obtained and the deduced amino acid sequence showed conserved signature regions for peptide synthetases and revealed a high similarity of 61.1 % to genes peptide synthetase of Bacillus subtilis.
Summary
This study was designed to comparatively investigate 28 S. suis cultures isolated from various pathological processes of pigs. All cultures could be identified biochemically and most of the cultures could be serogrouped with specific antiserum against Lancefield's serogroup D. Serotyping of the S. suis isolates mainly revealed capsular types 2, 1, and 22. In addition, part of the cultures, mostly those of serotype 2, reacted with monoclonal antibodies to the virulence protein muraminidase‐released protein, and, in parallel with monoclonal antibodies against the virulence protein extracellular factor. Independently of serotype and the occurrence of both virulence proteins, four cultures haemagglutinated erythrocytes from pigs, humans and rabbits. The haemagglutination reaction appeared to be related to the surface hydrophobicity of the isolates. However, part of the cultures with hydrophobic surfaces did not haemagglutinate the available erythrocyte preparations. The surface characteristics of the S. suis isolates shown in this investigation could be used to characterize individual isolates of S. suis that might be of importance for epidemiological studies.
Encapsulation is thought to be a critical virulence factor in streptococci of serological group B. In the present study two encapsulated low‐density variants could be separated from their unencapsulated original strains by Percoll gradient centrifugation. The original strains had been isolated from human endocarditis and bovine mastitis. Type antigen preparations of the encapsulated human and bovine group B streptococcus reacted with type III‐ and type IV‐specific antiserum, respectively. No comparable reactions could be observed with their unencapsulated parent strains. In contrast to the original strains, the encapsulated variants grew with uniform turbidity in fluid medium and formed diffuse colonies in soft agar. The original strains grew as granular sediment and formed compact colonies in soft agar. In addition, the original strains appeared to have a more hydrophobic surface and showed significantly greater adherence to epithelial cells. In contrast to the nonencapsulated parent strains, the encapsulated variants were less phagocytosed by polymorphonuclear leukocytes. These findings may help our understanding of the pathogenic importance of phase variants in infections with this bacterial organism.
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