ABSTRACT
The sialic acid content and the cell-surface hydrophobicity index of 40 group B streptococci (GBS) strains were assessed. GBS isolated from invasive infections (virulent strains) presented an increased level of sialic acid content (1.4%) when compared with GBS isolated from asymptomatic patients (0.53%). Treatment of GBS strain 85634 with neuraminidase resulted in a decrease (about 25%) in the net negative surface charge as assessed by cell electrophoresis. This finding suggests that sialic acid residues are important anionogenic groups exposed on GBS cell surface. N-acetylneuraminic acid was the only sialic acid derivative characterized in the strain 85634 as evaluated by gas-liquid chromatography. GBS from different serotypes presented a hydrophobic index mean value of 0.9. Even though the sialic acid contributed effectively to the negative charge on GBS cell surface, no difference was observed in the hydrophobic index when virulent and avirulent strains were compared.
Subject(s)
Sialic Acids/analysis , Streptococcus agalactiae/chemistry , Female , Humans , Infant , N-Acetylneuraminic Acid , Pregnancy , Streptococcal Infections/microbiology , Streptococcus agalactiae/isolation & purification , Streptococcus agalactiae/pathogenicity , Surface Properties , VirulenceABSTRACT
Production of extracellular deoxyribonuclease by 394 strains of beta hemolytic streptococci was examined employing a deoxyribonucleic acid-methyl green assay. Enzymatic activities were measured in supernatants of bacterial cultures. Of the strains tested, 316 (80%) produced the enzyme. Nuclease production was demonstrated in 100% of group A strains and in 85, 74 and 58% of groups B, C and G, respectively. Levels of nuclease activity were then evaluated statistically. The analysis of variance showed that group A strains produced more enzyme than did streptococci of groups B, C or G. Group B strains produced less nuclease than did isolates of groups C or G. There was no significant difference in the levels of nuclease produced by groups C and G or by the various serological types of group B streptococci. Human group C strains produced more enzyme than animal strains.
Subject(s)
Deoxyribonucleases/metabolism , Streptococcus/enzymology , Animals , Deoxyribonucleases/biosynthesis , Extracellular Space/enzymology , Humans , Serotyping , Species Specificity , Streptococcus/classification , Streptococcus/isolation & purificationABSTRACT
The effect of a subminimal inhibitory concentration of penicillin on the production of bound and free hemolysins by streptococci was examined using sheep red blood cells. A marked decrease of a group C cell-free and bound activities was observed with penicillin at a concentration of 1/3 of the MIC whereas an increase was observed with those of a group G strain. Potassium ferricyanide and anti-streptolysin O (group A streptococcus) were strongly inhibitory for the free activities of both strains. The cell-bound activities were stimulated by addition of RNA during bacterial growth in control cultures and also in drug-containing media.
