Partial characterization of Streptococcus suis type 2 hemolysin

Abstract

Streptococcus suis type 2 was evaluated for hemolysin production. Supernatants of S. suis type 2 grown in Todd-Hewitt broth were assayed for hemolytic activity by a photometric assay. Twenty-two additional serotypes of S. suis (1, 3 to 22, and 1/2) were evaluated for hemolysin production; nine of them (1/2, 1, 4, 5, 14, 15, 17, 19, and 20) were positive. The effects of temperature, atmosphere, centrifugation, sonication, chemicals, bovine serum albumin, fetal calf serum, and enzymes on S. suis type 2 hemolysin activity were studied. Maximum hemolysis occurred after incubation in RPMI 1640 medium at 40°C in 6% CO2 and after growth in Todd-Hewitt broth at 37°C under anaerobic conditions. Hemolytic activity was absent after the addition of fetal calf serum and decreased after the addition of trypsin or amylase. However, treatment of erythrocytes with amylase or trypsin prior to incubation with supernatant also resulted in a decrease in hemolytic activity. The addition of bovine serum albumin caused increased hemolytic activity. Dipyridyl and EDTA had negligible effects on hemolysis. Hemolytic S. suis type 2 culture supernatant injected intraperitoneally failed to cause death in BALB/c mice. Data from our study indicate that S. suis type 2 hemolysin is a secreted or loosely cell bound, thermolabile molecule whose activity is growth condition dependent.

Use of Ribotyping and Hemolysin Activity To Identify Highly Virulent Streptococcus suis Type 2 Isolates

“…S. suis isolates also produce a thiol-activated hemolysin (8,16), which has been implicated as a virulence factor in a number of bacteria (1,9,26); however, its role as a virulence factor in S. suis infection is not known. The in vitro production of hemolysin by S. suis strains isolated from diseased pigs suggests a correlation with disease (18), and protection studies with pigs (16) and mice (17) indicate that it is involved in protection.…”

“…Hemolysin assay. Hemolysin assays were carried out for each isolate as described previously (8). Briefly, colonies were harvested from tryptic soy agar (Difco) plates with cold RPMI 1640 (RPMI; GIBCO Laboratories, Grand Island, N.Y.), and the optical density at 560 nm was adjusted to 1.6.…”

Detection of genomic heterogeneity in Streptococcus suis isolates by DNA restriction fragment length polymorphisms of rRNA genes (ribotyping)

“…Titration of hemolytic activity. Titration of hemolytic activity was carried out as previously described (10).…”

Identification and Characterization of thecpsLocus ofStreptococcus suisSerotype 2: the Capsule Protects against Phagocytosis and Is an Important Virulence Factor

“…This suggests that there is only a minor contribution of the capsule to the virulence of S. suis. Indeed, various bacterial components, such as extracellular and cell membrane-associated proteins, fimbriae, hemagglutinins, and hemolysin, have been suggested as virulence factors (7,9,10,14,15,39,41). However, the precise role of these protein components in the pathogenesis of the disease has not been established (29).…”