Enzymatic properties of group B streptococci (GBS) serotypes from bovine milk and human routine vaginal specimens were investigated. Out of the 56 human and 66 bovine GBS, 35 and 30 could be classified serologically by a co-agglutination test with type-specific antisera, respectively. Hyaluronidase (HYAL), streptokinase (SK) and protease activities were detected using culture media. HYAL activity was observed mostly in typable human GBS, and serotypes Ia, Ic and II comprised 77.3 % of the typable strains producing HYAL. Bovine GBS serotypes II, III and VII comprised 87.5 % of typable bovine strains exhibiting HYAL activity. SK activity was detected only in three human GBS. Human GBS serotypes Ia, Ic, II, III, VII and almost all typable bovine GBS strains showed protease activity. b-D-glucosidase activity was frequently observed in human GBS, whereas N-acetyl-b-D-glucosaminidase activity was mostly detected in nontypable GBS from humans. These results indicate that different GBS serotypes could vary in their virulence properties, and bovine and human GBS isolates could not be differentiated by their enzyme activities. Use of the culture media appeared to be a simple-to-apply and useful method for the detection of extracellular enzyme activity such as HYAL, protease and SK.
INTRODUCTIONGroup B streptococci (GBS) are a well-known causative agent of contagious bovine mastitis and serious human perinatal infections. GBS possess a variety of potential virulence factors on the bacterial surface, including capsular polysaccharides and c (a/b) protein with distinct structural and antigenic types or serine protease and C5a peptidase (Spellerberg, 2000;Yildirim et al., 2002). Capsular components may assist in enhancing adaptation of the organism to various tissues within the host and a sialylated GBS capsule protects GBS by interference with opsonophagocytosis. Fibronectin-binding protein possesses a peptidase domain that specifically cleaves human complement component C5a, ablating its neutrophil chemo-attractant property. Also, a related GBS cell surface protease, CspA, targets host fibrinogen, producing adherent fibrin-like cleavage products that coat the bacterial surface and interfere with opsonophagocytic clearance (Doran & Nizet, 2004).GBS are serologically classified into at least nine capsular polysaccharide antigen types (Ia, Ib, II, III, IV, V, VI, VII and VIII) and three protein antigen types (Ic, R and X) (Jelínkoá, 1977;Spellerberg, 2000). Serotyping based on the capsular polysaccharide and protein antigen of the cell wall gives more information about common or different characteristics between bovine and human GBS as well as their epidemiological distribution (Devriese, 1991;Ekin & Gurturk, 2006). Several different bacterial products, such as extracellular enzymes and toxins, are also considered to be important in pathogenesis of streptococcal infections. High-level enzyme production is frequently found in most virulent strains of GBS. One of them is an extracellular hyaluronidase (HYAL; hyaluronate lyase) ...