Expression of two different antiphagocytic M proteins by Streptococcus pyogenes of the OF+ lineage

All clinical isolates of Streptococcus pyogenes (group A streptococcus) share the ability to resist phagocytosis and grow in human blood. In many strains, this property is due to the expression of a single antiphagocytic M protein, while other strains express more than one M-like molecule, of which the role in phagocytosis resistance is unclear. In particular, all S. pyogenes strains of the OF+ lineage, representing approximately half of all isolates, express two M-like proteins, Mrp and Emm, which are immunologically unrelated. These two proteins bind different ligands that have been implicated in phagocytosis resistance: Mrp binds fibrinogen and Emm binds the complement inhibitor C4BP. Using a clinical isolate of the common serotype 22, we created mutants affected in the mrp and emm genes and characterized them in phagocytosis experiments and by electron microscopy. A double mutant mrp-emm- showed strongly decreased resistance to phagocytosis, while mrp- and emm- single mutants grew well in blood. However, optimal growth required the expression of both Mrp and Emm. Experiments in which coagulation was inhibited using the specific thrombin inhibitor, hirudin, rather than heparin, indicated that Emm is more important than Mrp for resistance to phagocytosis. Tuftlike surface structures typical for S. pyogenes were still present in the mrp-emm- double mutant, but not in a mutant affected in the regulatory gene mga, indicating that the presence of these surface structures is not directly correlated to phagocytosis resistance. Our data imply that OF+ strains of S. pyogenes express two antiphagocytic M proteins with different ligand-binding properties.

The fibronectin-binding protein of Streptococcus pyogenes, SfbI, is involved in the internalization of group A streptococci by epithelial cells

Streptococcus pyogenes organisms (group A streptococci) are considered to be highly adhesive extracellular pathogens. However, it has recently been reported that S. pyogenes has the capacity to efficiently invade eukaryotic cells. In this study, we demonstrate that the interaction of S. pyogenes fibronectin-binding protein (SfbI) with fibronectin on nonphagocytic HEp-2 cells triggers bacterial internalization. Blocking of the SfbI adhesin by either antibodies against the whole protein or antibodies against the fibronectin-binding domains of SfbI, as well as pretreatment of HEp-2 cells with purified SfbI protein, prevents both S. pyogenes attachment and internalization. Inert latex beads precoated with the purified SfbI protein are ingested by eukaryotic cells, demonstrating that SfbI is per se enough to trigger the internalization process. Experiments performed with a recombinant SfbI domain encompassing the two fibronectin-binding regions of the SfbI molecule demonstrated that these binding regions are essential and sufficient to activate uptake by HEp-2 cells. These results demonstrate that the fibronectin-binding protein SfbI is involved in both S. pyogenes' attachment to and ingestion by HEp-2 cells and contribute to elucidation of the underlying molecular events leading to eukaryotic cell invasion by S. pyogenes.

Mode of action of a lysostaphin-like bacteriolytic agent produced by Streptococcus zooepidemicus 4881

Electron microscopy of zoocin A-treated sensitive streptococcus cells revealed cytoplasmic disruption and ultimately complete rupture of the cell wall. Culture viability and optical density were shown to decrease rapidly and simultaneously in Streptococcus pyogenes FF22 but less quickly in the relatively more resistant Streptococcus mutans 10449. Zoocin A was shown to cleave hexaglycine in a colorimetric cell-free microtiter assay system, and it is concluded that the killing action of zoocin A, like that of lysostaphin, is most probably the result of direct cleavage of the peptidoglycan cross-links in the cell wall. The relationship between sensitivity to zoocin A and the peptidoglycan cross-linkage structure of Streptococcus zooepidemicus, Lactococcus spp., S. pyogenes, Streptococcus gordonii, Streptococcus oralis, S. mutans, and Streptococcus rattus has been evaluated.

In situ localization of Streptococcus pyogenes during acute tonsillitis: an immunocytochemical study with gold markers

Epithelial cells were harvested from the surface of the palatine tonsils of seven patients with current acute tonsillitis, proven culture-positive for Streptococcus pyogenes. The epithelial cells harboured attached bacteria, which expressed positive affinity to gold-labelled antiserum to S. pyogenes. The gold particles adhered selectively to the bacterial capsules. The microorganisms were held in place by projections protruding from the epithelial cells, which were in close contact with the pili of the bacteria. In some areas, positive immunogold-labelled bacteria intermingled with bacteria lacking such labelling. None of the culture-negative controls harboured epithelial cells with positive immunogold-labelled bacteria. Orally administered phenoxymethylpenicillin caused a significant reduction in both culture-positive S. pyogenes and bacteria displaying positive coating with specific gold-labelled antiserum to S. pyogenes.

Cross-reactivity between human sialyl Lewis(x) oligosaccharide and common causative oral bacteria of infective endocarditis

The expression of sialy-Lewis(x) (sLe(x); Neu5Ac alpha 2-3 Gal beta 1-4) (Fuc alpha 1-3) GlcNAc-R) on oral bacteria producing infective endocarditis was determined by a whole-cell enzyme linked immunosorbent assay and an immunoelectron microscopy using the well-characterized anti-sLe(x) monoclonal antibody SNH-3 (mAb SNH-3; IgM class). mAb SNH-3 reacted strongly with whole cells of oral bacteria: Streptococcus sanguis, Streptococcus mutans, Streptococcus mitis, Streptococcus salivarius, Streptococcus intermedius, Streptococcus constellatus, Streptococcus anginosus, Streptococcus pyogenes, Actinobacillus actinomycetemcomitans, Eikenella corrodens and Porphyromonas gingivalis. The negatively stained immuno-electron micrograph of Streptococcus pyogenes showed many reactive gold particles on the cell surface. Our findings demonstrated the existence of immunologic mimicry between the sLe(x) oligosaccharide and cell surface antigens of many species associated with infective endocarditis. We propose the hypothesis that if these bacteria escape their normal habitats, the surface components that mimic the sLe(x) oligosaccharide might bind to host antigens of the selectin family which could promote binding to endothelial cells and, consequently, initiation of the events leading to infective endocarditis.

Invasion of cultured human cells by Streptococcus pyogenes

The invasive capacity of streptococcal strains belonging to groups A and B was evaluated by infecting human epithelial and endothelial cells and monitoring the number of viable intracellular bacteria at different times postinfection. All strains tested entered eukaryotic cells (HeLa, HEp2 and HUVE), with Streptococcus pyogenes exhibiting a higher invasion efficiency than group B streptococci (GBS). No intracellular multiplication was observed, and GBS remained viable 24 h postinfection, whereas S. pyogenes were gradually killed. We found that cytochalasin D almost completely inhibited internalization of all bacterial strains, whereas colchicine had no effect, indicating that host microfilaments play a major role in bacterial internalization. Moreover, the use of the lysosomotropic agent ammonium chloride enabled us to demonstrate that a pH increase in the intracellular vesicles did not affect streptococcal entry. These results were documented by electron microscopic observations which revealed the different steps in the invasion pathway, including a fusion event between phagosomes containing S. pyogenes and lysosomes.

Antigenic determinants of Streptococcus pyogenes ribosomes

An attempt has been made to identify the ribosomal proteins responsible for the production of antibodies upon immunization of monkeys with 70S ribosomes of Streptococcus pyogenes group A 29 M type. Identification was carried out by immunoblotting after isolation and separation of the proteins of 70S, 50S and 30S ribosomal particles on one- and two-dimensional gel electrophoresis. Three major proteins of S. pyogenes 70S ribosomes with clearly expressed antigenic properties were identified by Western blotting. One of these proteins belonged to the 50S subunit and the other two--to the 30S ribosomal subunit. We assume that these proteins represent those of group A streptococci. As a result the antibodies are produced first of all against these antigenic proteins in contrast to the others evolutionary conservative ribosomal proteins.

Group A streptococci efficiently invade human respiratory epithelial cells

Although infection by group A streptococci is a model of extracellular mucosal pathogenesis, these organisms can be associated with highly invasive infections resulting in sepsis and shock. Over the last 6 yr this species has renewed its reputation as a significant cause of sepsis and has piqued interest in the mechanism by which some strains are better able to breach mucosal barriers to gain access to the bloodstream than are others. An internalization assay was developed on the basis of resistance of intracellular streptococci to penicillin and gentamicin. Experiments showed that stationary-phase, as opposed to logarithmic-phase, bacteria are efficiently internalized and can persist in cultured human cells. Electron microscopy confirmed that streptococci were contained within intracellular vacuoles. Various strains of streptococci revealed significant differences in their capacity to be internalized. Two type M1 streptococci isolated from blood infections were internalized at frequencies equal to those reported for Salmonella and Listeria monocytogenes and greater than the frequency of a clonal variant from a case of pharyngitis.

Persistent acylation of high-molecular-weight penicillin-binding proteins by penicillin induces the postantibiotic effect in Streptococcus pyogenes

Penicillin at 10X MIC induced a postantibiotic effect (PAE) of 2.1 h in Streptococcus pyogenes. Progressive increases in the densities of penicillin-binding proteins (PBPs) 1-3 of the bacterium were detected at 30, 60, and 90 min during the postantibiotic phase. The increase in colony-forming units during this phase paralleled the kinetics of incorporation of lysine into proteins, suggesting that growth was triggered by de novo synthesis of PBPs. The question was raised as to whether the progressive increases in densities of PBPs were due to the restoration of preexisting PBPs or to synthesis of new PBPs. With 10X MIC of clindamycin to inhibit PBP synthesis during the postantibiotic phase, the temporal increase in densities of PBPs 1-3 were totally inhibited. These results suggest that the PAE of penicillin in S. pyogenes is caused by irreversible binding of penicillin to PBPs 1-3 and represents the time necessary for synthesis of new PBPs required for normal growth.

High voltage immunoelectron microscopy of complement receptor type 3-mediated capping and internalization of group A streptococcal cell walls by human neutrophils

The mechanism of human neutrophil clearance of peptidoglycan group A-specific polysaccharide polymers derived from streptococcal cell walls (PG-APS) was investigated by high voltage immunoelectron microscopy (HVEM) in order to determine how neutrophils process this highly inflammatory bacterial debris. Neutrophil monolayers were incubated from 5-30 min with serum-opsonized PG-APS. Cells were lightly fixed with 0.5% glutaraldehyde, and the PG-APS was localized on the neutrophil surface by immunogold using antibodies to N-acetyl-glucosamine and 15 nm colloidal gold coupled to goat anti-rabbit IgG. Neutrophils were viewed unsectioned by stereo HVEM. Patches of PG-APS were distributed randomly on the plasmalemma of well-spread neutrophils within 5 min. In polarized cells, PG-APS was densely localized on the uropod and retraction fibers. Within 15 min, PG-APS was predominantly concentrated into a large aggregate, measuring approximately 1 micron in diameter, near the cell margin or nucleus. The aggregate of PG-APS was engulfed in the vicinity of the indentation of the nucleus (hof). Intact microfilaments were required for aggregation and internalization of PG-APS. Binding of PG-APS was dependent upon complement fixation. Furthermore, PG-APS elicited an increase in density of complement receptor type 3 (CR3, C3bi receptor) on the neutrophil surface as determined by morphometry of immunogold labeled anti-CR3. When cells were stained for both PG-APS and CR3, co-localization was observed, and stereomicroscopy revealed clusters of CR3 in areas associated with phagocytosis. These data suggest that neutrophils use an efficient mechanism for removal of bacterial debris. Unlike whole streptococci which are phagocytosed at multiple sites, these bacterial cell walls are first collected into a large aggregate, or cap, which is then internalized at one site.

Morphological alterations of Staphylococcus aureus and Streptococcus pyogenes exposed to cefdinir, a new oral broad-spectrum cephalosporin

Affinity for penicillin-binding proteins (PBPs) and the morphological alteration of Staphylococcus aureus 209-P JC and Streptococcus pyogenes C-203 exposed to cefdinir were studied. Although cefdinir was bactericidal against both strains, the extent of the decrease in colony-forming units (CFU) was similar in a fairly wide range of concentrations. Transmission electron microscopy of S. aureus 209-P JC revealed that cefdinir induced thickening of the cross wall and frequent cell lysis at low concentrations. The lytic sites were seen at the site of septum formation. In S. pyogenes C-203, cefdinir induced thickening of the peripheral wall and cross wall, and protoplast-like cells were observed during the incubation period. Cefdinir showed high affinity for all PBPs of S. aureus 209-P JC and S. pyogenes C-203. The drastic changes in the morphology of S. aureus and S. pyogenes were caused by binding of cefdinir to all PBPs.

The in vitro antibacterial activity of ceftriaxone against Streptococcus pyogenes is unrelated to penicillin-binding protein 4

The in vitro activities of penicillin and ceftriaxone were compared against 29 strains of Streptococcus pyogenes with the result that ceftriaxone showed greater activity than penicillin. The morphological changes induced by 1/2 and 1x MIC concentrations of penicillin and ceftriaxone, respectively, were very similar using scanning electron microscopy. Competitive binding studies using 'cold' penicillin or ceftriaxone as inhibitors of radiolabeled penicillin binding demonstrated that ceftriaxone had a very low affinity for penicillin binding protein (PBP) 4 compared to that of penicillin. Since ceftriaxone had greater antibacterial activity, this suggests that PBP 4 may not be important to the in vitro activity of ceftriaxone. In contrast, the IC50 for ceftriaxone was much lower (> 200 fold) for PBPs 2 and 3 compared to PBP 4, suggesting greater avidity of these high molecular mass PBPs for ceftriaxone. These data may at least in part explain the superior in vitro activity of ceftriaxone compared to penicillin against S. pyogenes. These data, together with the observation that PBP 1 was saturated at a lower concentration of penicillin than any of the other PBPs, suggest that the inhibition of PBPs 1, 2, and 3 mediates the bactericidal activity of beta-lactam antibiotics against group A streptococci.

Clonal specificity of human gamma delta T cells: V gamma 9+ T-cell clones frequently recognize Plasmodium falciparum merozoites, Mycobacterium tuberculosis, and group-A streptococci

Peripheral blood gamma delta T cells expressing a V gamma 9/V delta 2 T-cell receptor are stimulated by killed bacteria including Mycobacterium tuberculosis (m.tb.) and group-A streptococci (strep A). In addition, recent data indicate that V gamma 9/V delta 2 T cells from unexposed individuals also respond to Plasmodium falciparum (P. falcip.) merozoites. Here we analyzed the reactivity to these ligands of 23 V gamma 9/V delta 2, 3 V gamma 9/V delta 1, and 4 V gamma 9-/V delta 1 clones derived from 8 healthy individuals after phytohemagglutinin stimulation of cell sorter-selected gamma delta T cells. Upon restimulation in the presence of irradiated antigen-presenting cells, the majority of V gamma 9/V delta 2 clones recognized m.tb. and strep A (but not strep D), and about one third of the clones also recognized P. falcip. Some clones, however, recognized only one or two of the tested ligands, and 4 V gamma 9/V delta 2 clones did not react at all. Interestingly, 2 of 3 V gamma 9/V delta 1 clones proliferated in response to m.tb., P. falcip., strep A and strep D, while V gamma 9-/V delta 1 clones were not activated by any of the tested ligands. Nucleotide sequence analysis indicated a broad diversity of V gamma 9 N regions in V gamma 9/V delta 2 clones. At the clonal level, our results demonstrate that individual V gamma 9/V delta 2 T cells can recognize m.tb., strep A, as well as P. falcip.-infected erythrocytes, with no influence of the expressed V gamma 9 N region.

Role of streptococcal IgG Fc receptor in tissue deposition of IgG in rabbits immunized with Streptococcus pyogenes

Induction of anti-IgG during hyperimmunization of rabbit with Streptococcus pyogenes (group A streptococci; GAS) was previously shown to require the presence of IgG Fc receptors (FcR) in the vaccine strain. In the present work, we examined whether streptococcal FcR activity might also be of importance for heart and kidney deposition of IgG, known to occur in poststreptococcal sequelae as well as during experimental immunization of animals. Each of three IgG-binding (GAS types M1, M12 and M22) and two non-binding (GAS type T27 and S. agalactiae (GBS) type Ia) streptococcal strains were used for intravenous immunization of rabbits during two periods of eight and six weeks, respectively, separated by an interval of one month. Before use, vaccine strains were treated with KSCN and carefully washed in order to remove any surface-bound immunoglobulins. No deaths occurred among injected rabbits. No tissue deposition was elicited by the GAS type T27 or the GBS strain. In contrast, the strains of types M1, M12 and M22 all induced deposits of IgG in kidney and heart tissue, beginning during the first immunization period. In two tested animals, receiving GAS of types M1 or M22, circulating immune complexes containing anti-IgG antibodies were also detected. Finally, serum autoantibodies reacting with preparations of heart and kidney, but not lung or liver, were demonstrated in each of six animals receiving M1 or M22, reaching maximum levels during reimmunization; such antibodies were not evoked by the two strains not binding IgG. Our results suggest that, in GAS with capacity for non-immune binding of IgG, triggering of anti-IgG acted to enhance tissue deposition of IgG or immune complexes in immunized rabbits. Furthermore tissue-specific antibodies were elicited only by the IgG-binding strains and occurred comparatively late during immunization, suggesting that those antibodies might have been triggered due to the exposition of hidden kidney and heart determinants.

Surface hydrophobicity of "rheumatogenic" and "nephritogenic" strains of group A streptococci and the ultrastructural surface feature of pharyngeal cells exposed to group A streptococci

The present study was carried out to determine the surface hydrophobicity of group A streptococcal strains responsible for rheumatic fever (RF), "rheumatogenic" strains (RG strains) and strains causing glomerulonephritis, "nephritogenic" strains (NG strains) in relation to their adhesion to human pharyngeal cells. Scanning electronmicroscopic (SEM) studies were carried out to the difference, if any, in the adherence of group A streptococci (M type 5) to pharyngeal and buccal cells (PEC and BEC). By employing two techniques for hydrophobicity determination, salt aggregation titre (SAT) and n-hexadecane binding technique, it was observed that RG strains (M5, M1 and M6) were more hydrophobic than NG strain, M49. However, NG strain M12 was almost equally as hydrophobic as RG strains. The adherence of RG strains, except M1 and M24, to PEC was greater in number than that of NG strains. Although M1 strain was hydrophobic, its adherence to PEC was less. Pepsin and trypsin treatment with streptococci reduced the hydrophobicity and adherence of RG and NG strains to PEC. SEM studies revealed firmly adhered indigenous bacteria on PEC and BEC. Streptococci (M5) adhered more to PEC than to BEC. SEM studies also showed that PEC had a peculiar ultrastructural surface feature to which streptococci adhered. These findings suggest that streptococcal hydrophobicity alone does not determine their adhesion to PEC. The surface nature of PEC might be a characteristic feature of the epithelial cells that allows streptococci to adhere and colonize or it might be a consequence of streptococcal adhesion.

Possible role of Streptococcus pyogenes in mucocutaneous lymph node syndrome. XI. Immunoelectron microscopic observation of protoplast-like "spherical bodies" detected in peripheral blood of MCLS patients

Protoplast-like "spherical bodies" averaging 0.5-1.5 microns in diameter and devoid of cell walls were first detected by Ueno et al, in the buffy coat of heparinized venous blood from patients with mucocutaneous lymph node syndrome (MCLS). But the nature of the "bodies" has yet to be clarified because of the absence of convincing evidence pointing to their antigenic characteristics. The present investigations were designed solely to provide a serological identification of the "bodies" by the use of immunoelectron microscopy, with the following results. First, "spherical bodies" bearing a striking resemblance to those observed by the above-mentioned authors were detected in biopsy specimens from challenge sites in mice infected with Streptococcus pyogenes as well as in the buffy coat of peripheral blood from MCLS patients. Second, the "bodies" detected were stained distinctly in both cases by an immunohistochemical technique using, as the primary antibody, a rabbit antiserum raised toward S. pyogenes-derived protoplasts, which was then absorbed with protoplasts from Staphylococcus aureus and Escherichia coli. Third, the absorbed sera were proved to be not faultless, because complete specificity toward protoplasts from S. pyogenes was not attained due to the presence of a large amount of cross-reactive antigens between protoplasts from the immunizing and absorbing strains of bacteria. The implications of these findings are discussed, particularly in relation to the evaluation of the present serological test for the "spherical bodies".

[Study of the composition of cell wall of group A Streptococcus after hydrolysis using muramidase from Streptomyces levoris]

The aim of the experiment was to study the lysis products of cell walls of group A streptococci resulting from exposure to N-acetylmuramidase. It was shown that for isolating surface proteins free of polysaccharide and peptidoglycan fragments it was necessary to treat the streptococcal cell walls with endo-beta-N-acetylmuramidase for no more than 30 minutes. Prolonged hydrolysis with muramidase led to the presence of polysaccharide and the peptidoglycan fragments in the protein fractions, intracellular wall proteins covalently bound to the peptidoglycan fragments and polysaccharide being also released.

Ultrastructural localization of the fibrinogen-binding domain of streptococcal M protein

Binding of fibrinogen to the M protein located on the surface fibrillae of group A streptococci impedes deposition of complement and thus contributes to the virulence of these organisms. We investigated this binding by electron microscopy using postembedding immunogold labeling. Both fibrinogen and its D fragment formed a distinct dense layer in the surface fibrillae, separated by 10 nm from the compact part of the cell wall. Labeling the sections with anti-fibrinogen or anti-fragment D showed that the fibrinogen-binding region lay within a 25-nm segment of the fibrillae beginning approximately 30 nm from the inner surface of the cell wall. The outer surface of the fibrinogen layer could be labeled with antibody to the amino-terminal half of type 24 M protein, indicating that the fibrillar tips remained exposed after fibrinogen binding. The degree of labeling with anti-fibrinogen, determined by gold particle counting, was the same whether the bacterial cells had been incubated with purified fibrinogen or whole plasma. These results indicate that the fibrinogen-binding region lies in the distal (amino-terminal) half of the M protein molecule but excludes the most distal portion, which is the site of epitopes that interact with opsonic anti-M antibody, and that plasma proteins other than fibrinogen, a number of which are known to bind to group A streptococci, do not interfere with fibrinogen binding.

Cell surface proteins of a group A streptococcus type M4: the IgA receptor and a receptor related to M proteins are coded for by closely linked genes

Two genes coding for cell surface proteins were cloned from a group A streptococcus type M4: the gene for an IgA binding protein and the gene for a fibrinogen binding protein. Both proteins were purified and partially characterized after expression in Escherichia coli. There was no immunological cross-reaction between the two proteins. The IgA binding protein, called protein Arp4, is similar to an IgA receptor previously purified from another strain of group A streptococci, but the proteins are not identical. Characterization of many independent clones showed that the two proteins described here are coded for by closely linked genes. Bacterial mutants have been found which have simultaneously lost the ability to express both genes, and a simple method to isolate such mutants is described. The existence of these variants indicates that expression of the two cell surface proteins may be coordinately regulated. Binding of fibrinogen is a characteristic property of streptococcal M proteins, and the available evidence suggests that the fibrinogen binding protein is indeed an M protein.

Localization and characterization of fibronectin-binding to group A streptococci. An electron microscopic study using protein-gold-complexes

The location and nature of the binding sites for fibronectin (Fn) and its N-terminal 29 K fragment (FnF) on group A streptococci were studied by electron microscopy using these proteins labelled with colloidal gold. The investigated strains exhibited a different labelling intensity as well as a different labelling pattern varying from a strong regular distribution to a weak focal binding. Binding of Fn and FnF was inhibited by itself as well as by lipoteichoic acid (LTA), anti-LTA and concanavalin A. Simultaneous labelling of the bacteria with marker complexes of FnF, human serum albumin and fibrinogen revealed separate receptor sites for each protein. Our results confirmed LTA to be mainly responsible for the binding of Fn on group A streptococci.

Suppression of streptococcal cell wall-induced arthritis by a potent protease inhibitor, bis(5-amidino-2-benzimidazolyl)methane

Bis(5-amidino-2-benzimidazolyl)methane, a powerful synthetic trypsin inhibitor, proved to be highly effective in suppressing the arthritis induced by streptococcal cell wall fragments in Lewis rats. It reduced not only the degree of synovitis, osteitis, and hematopoietic hyperplasia in the distal extremities, but also the degree of associated granulomatous inflammation in the liver. The results suggest that trypsin-like proteases play an important role in this arthritis model and that inhibitors may be useful in the treatment of similar arthritic conditions in humans.

Electron microscopic localization of lipoteichoic acid on group A streptococci

The location of lipoteichoic acid (LTA) on the surface of group A streptococci was studied by immunoelectron microscopic and ultrastructural cytochemical methods, i.e. by means of LTA antibodies labelled with ferritin, or concanavalin A labelled with ferritin or colloidal gold. All these methods proved the LTA to be located on the outer cell surface of most group A streptococcus strains. The differences in the intensity of labelling paralleled the hydrophobicity of the strains, being substantially higher in the strains exhibiting a high degree of hydrophobicity. Treatment of streptococci with pronase or trypsin led to a complete loss of surface-located LTA. On the other hand, pepsin treatment of streptococci under mild conditions resulted in an increased amount of surface-located LTA in some strains. On the isolated cell walls, LTA could be demonstrated only on the outer surface of the walls. These findings correlated well with the presumed role of group A streptococcus LTA in the adherence of streptococci to the epithelial cells which is accomplished with the aid of surface-located LTA molecules.