Mode of Binding of Fibrinogen, Fibronectin and Iron-binding Proteins by Animal Enterococci

Sixty-two animal enterococci were examined for their binding of bovine fibrinogen, porcine fibronectin, bovine lactoferrin, bovine apotransferrin and human holotransferrin in the particle agglutination assay (PAA). Individual strains expressed binding of selected glycoproteins to various degrees (0, 1, 2, 3), whereas bovine fibrinogen binding of enterococci from goats, rabbits and rodents was the strongest (3) in general. Porcine fibronectin was bound weakly (1 or 2) by enterococci from horses, dogs, poultry, rabbits and rodents, while most of the goat isolates and half of the dog feed isolates did not bind fibronectin (0). Bovine lactoferrin was bound especially by the isolates from rodents and rabbits. Bovine apotransferrin was bound very weakly (1) by only a few isolates. Human holotransferrin was bound to a greater extent than apotransferrin by some isolates from rabbits and rodents. Since multiresistant strains are preferred in our binding studies, enterococci were also examined for their antibiotic resistance pattern. Almost all investigated isolates were resistant at least to one antibiotic. However, some strains displayed resistance to five or six antibiotics of 10 antibiotics tested. In a study of the inhibitory effect of heparin, porcine mucin and hyaluronic acid, the greatest effect was observed after heparin treatment of bacterial cells. These observations, as well as the expression of heparin binding by most strains, may suggest that at least one mode of enterococcal attachment utilizes glycosaminoglycan chains present on the surface of adherent cells.

Binding of extracellular matrix molecules by probiotic bacteria

AIMS

The aim of this study was to investigate extracellular matrix (ECM) and mucin binding of selected bacterial isolates with probiotic features in comparison with commercially used probiotic bacteria.

METHODS AND RESULTS

ECM molecules were immobilized in microtitre plates (mucin and fetuin) or on the surface of latex beads. Porcine mucin was bound by all 13 probiotic strains tested with important inter-strain differences; however, fetuin binding was similar (weak) for all 14 strains tested. Strongly positive (three) binding of bovine fibrinogen was expressed by strains from fermented food (Lactobacillus rhamnosus GG, L. casei Shirota and L. johnsonii La1) as well as by L. casei L.c., Lactobacillus sp. 2I3 and by L. plantarum LP. The other strains expressed moderate (2) or weakly positive (1) binding of bovine fibrinogen. Strongly positive (3) binding of porcine fibronectin was observed only with two strains; however, all other strains also bound this molecule. Bovine lactoferrin was bound to a higher extent than transferrins.

SIGNIFICANCE AND IMPACT OF THE STUDY

Some animal strains (at least L. casei L.c. and Lactobacillus sp. 2I3) are comparable with the commercially used strains with respect to their ECM binding ability. As this feature is important for probiotic bacteria to be able to colonize intestine, these strains should be considered for their wider use in fermented feed (or probiotic preparations) for animals.

Polyphasic identification of Bacillus and Brevibacillus strains from clinical, dairy and industrial specimens and proposal of Brevibacillus invocatus sp. nov

Thirty-three clinical, dairy and industrial isolates of aerobic endospore-forming bacteria which were unreactive in routine identification tests were characterized genotypically by using amplified rDNA restriction analysis (ARDRA), 16S rDNA sequencing and DNA-DNA reassociation, and phenotypically by using fatty acid methyl ester (FAME) analysis, SDS-PAGE of whole-cell proteins, API Biotype 100 assimilation tests and 16 other routine phenotypic tests. Three isolates were identified as strains of Bacillus badius, 12 as Brevibacillus agri, including 3 strains associated with an outbreak of waterborne illness, 4 as Brevibacillus centrosporus and 2 as Brevibacillus parabrevis; 12 strains contaminating an antibiotic production plant were recognized as members of a new species, for which the name Brevibacillus invocatus is proposed, with the type strain LMG 18962T (= B2156T = CIP 106911T = NCIMB 13772T).

Identification of novel immunogenic proteins of Helicobacter pylori by proteome technology

Cell surface proteins of the human gastric pathogen Helicobacter pylori, reference strain CCUG 17874, were extracted with acid glycine and fractionated by heparin affinity chromatography. The extracts were subsequently analysed using high-resolution two-dimensional gel electrophoresis (2-DE) and immunoblotting. Four proteins of low molecular masses (25-30 kDa) stained by Coomassie R-350, were identified by peptide ESI-MS/MS sequencing after in-gel tryptic digestion. The identified proteins were recognised by sera from H. pylori-infected patients. Two of them are now described for the first time as immunogenic proteins of which one protein was determined to be distinct from all H. pylori proteins previously described. In addition, the specificity of the identified peptides was evaluated using both 1-D and 2-D immunoblotting against a panel of sera from patients with various bacterial infections. The present identification of highly specific antigens of H. pylori will encourage the improvement of serological diagnostic tests to diagnose and monitor H. pylori infection.

Binding of human clusterin by Staphylococcus epidermidis

To hypothesise that Staphylococcus epidermidis may possess clusterin receptor(s), bacterial binding of human clusterin was determined. In a fluid phase, the binding was markedly influenced by culture medium and three out of 12 S. epidermidis strains grown on ISO-sensitest agar expressed clusterin-binding ability. S. epidermidis J9P, selected for further study, showed saturable binding of iodine-labelled clusterin, and the binding was only inhibited by unlabelled clusterin. The binding was sensitive to protease treatment. Scatchard plot indicated one single class of binding sites (K(d)=104.2 nM). None of the S. epidermidis strains bound immobilised clusterin. These data imply that ligand-receptor interaction exists between S. epidermidis and clusterin in fluid phase, but the domain(s) recognised by bacteria may have been occluded when clusterin was adsorbed on a surface.

Binding of vitronectin and clusterin by coagulase-negative staphylococci interfering with complement function

Coagulase-negative staphylococci (CoNS) are commonly associated with infections of prosthetic devices mediated by adsorbed host factors on biomaterial surfaces. Complement activation is known to occur and induce unspecific inflammation around the biomaterials. Human vitronectin (Vn) and clusterin (Clu), two potent inhibitors of complement, can be bound by CoNS. With a hypothesis whether binding of Vn or Clu influences complement activation, two measurements were determined. For Vn, complement activation was measured with a mouse anti-activated human C9 antibody. In the presence of Vn-binding strain, Staphylococcus hemolyticus SM13I, complement activation on a surface pre-coated with Vn occurred as it did in the absence of Vn pre-coating. For S. epidermidis 3380, which does not express binding of Vn, complement activation on a Vn-presented surface was significantly decreased. For Clu, erythrocytes lysis was measured to reflect the end product of complement activation (membrane attack complex). The complement-induced hemolysis increased when human serum was pre-incubated with Clu-binding strains, S. epidermidis J9P. The enhancement of hemolysis by J9P decreased when serum was supplemented by exogenous Clu. The data imply that interaction between CoNS and Vn or Clu interferes with one of their physiological functions, complement inhibition.

External ventricular drainage catheters: effect of surface heparinization on bacterial colonization and infection

Surface heparinization of central venous catheters has earlier been shown to reduce the frequency of bacterial colonization and septicaemia. The present study was undertaken to investigate the benefit of surface heparinization of external ventricular drainage (EVD) catheters in relation to bacterial colonization, as measured by bacterial growth and examination by a 16S-rRNA PCR assay, of catheters and of samples of cerebrospinal fluid (CSF). Ninety-eight heparinized and one hundred unheparinized EVD catheters from the same batch of catheters were used. Twenty point five percent of the heparinized and 22.8% (p = 0.63) of the unheparinized EVD catheters were colonized with bacteria. Culture of CSF, which is the definition of clinical infection in this study, yielded growth in 10.3% of patients with heparinized and in 6.3% (p = 0.18) of those with unheparinized catheters. PCR examination yielded positive signal in 31.3% of patients with heparinized catheters and in 37.7% (p = 0.061) of patients without (CSF and catheters). In the subgroup of patients with subarachnoid haemorrhages, there was a tendency, though not statistically significant, towards a lowered frequency of colonization with 23.1% for heparinized and 33.3% (p = 0.31) for unheparinized catheters. PCR examination did not contribute any further to the diagnostic procedure in the patients concerned. The EVD catheters are skin-penetrating devices and contamination from the skin flora is common. Skin cultures, obtained after skin disinfection and insertion of catheters, showed growth of bacteria in 62% of the patients.

Two-dimensional electrophoretic and immunoblot analysis of cell surface proteins of spiral-shaped and coccoid forms of Helicobacter pylori

Cell surface proteins of the human gastric pathogen Helicobacter pylori extracted during different in vitro growth phases were analyzed by one- and two-dimensional gelelectrophoresis (1-DE and 2-DE) and by 2-DE immunoblot. Broth-cultured H. pylori cells were stained with an acridine-orange dye to monitor the morphological status of the organism. In 2-day-cultures, 96% of the bacterial cells were spiral-shaped and four days later a morphological switch to coccoid forms occurred. In 10-day cultures spiral-shaped forms were not found. By 1-DE, proteins with the molecular masses of 87 and 120 kDa were detected in the 2-day cultures that disappeared in cells of 12-day cultures. A protein corresponding in size to the heat shock protein (GroEl homolog, Hsp60) and a 62 kDa protein, the ureaseB-subunit, were identified in extracted proteins of 2-, 8-, and 12-day cultures. 2-DE revealed an increased number of silver-stained spots of 8-day cultures (in average 250 spots) compared with protein extracted from 2-day cells (in average 160 spots). 2-DE immunoblots performed with sera containing antibodies to major H. pylori proteins such as the A- and B-subunits of urease and the Hsp60 showed similar reactivity to surface proteins extracted from 2-, 8-, and 12-day cultures, suggesting that these proteins remain immunologically intact. Pooled sera from infected patients absorbed with spiral-shaped cells showed an almost total blocking of the antibody reactivity to extracted coccoid proteins in 2-DE immunoblot. Eighteen spots were still visible, but this reactivity probably represents a solid overexpression by the coccoid cells of Hsp60 and ureaseB proteins and is thus difficult to block.

Two-dimensional electrophoretic and immunoblot analysis of cell surface proteins of spiral-shaped and coccoid forms of Helicobacter pylori

Cell surface proteins of the human gastric pathogen Helicobacter pylori extracted during different in vitro growth phases were analyzed by one- and two-dimensional gelelectrophoresis (1-DE and 2-DE) and by 2-DE immunoblot. Broth-cultured H. pylori cells were stained with an acridine-orange dye to monitor the morphological status of the organism. In 2-day-cultures, 96% of the bacterial cells were spiral-shaped and four days later a morphological switch to coccoid forms occurred. In 10-day cultures spiral-shaped forms were not found. By 1-DE, proteins with the molecular masses of 87 and 120 kDa were detected in the 2-day cultures that disappeared in cells of 12-day cultures. A protein corresponding in size to the heat shock protein (GroEl homolog, Hsp60) and a 62 kDa protein, the ureaseB-subunit, were identified in extracted proteins of 2-, 8-, and 12-day cultures. 2-DE revealed an increased number of silver-stained spots of 8-day cultures (in average 250 spots) compared with protein extracted from 2-day cells (in average 160 spots). 2-DE immunoblots performed with sera containing antibodies to major H. pylori proteins such as the A- and B-subunits of urease and the Hsp60 showed similar reactivity to surface proteins extracted from 2-, 8-, and 12-day cultures, suggesting that these proteins remain immunologically intact. Pooled sera from infected patients absorbed with spiral-shaped cells showed an almost total blocking of the antibody reactivity to extracted coccoid proteins in 2-DE immunoblot. Eighteen spots were still visible, but this reactivity probably represents a solid overexpression by the coccoid cells of Hsp60 and ureaseB proteins and is thus difficult to block.

Two-dimensional electrophoretic and immunoblot analysis of cell surface proteins of spiral-shaped and coccoid forms of Helicobacter pylori

Cell surface proteins of the human gastric pathogen Helicobacter pylori extracted during different in vitro growth phases were analyzed by one- and two-dimensional gelelectrophoresis (1-DE and 2-DE) and by 2-DE immunoblot. Broth-cultured H. pylori cells were stained with an acridine-orange dye to monitor the morphological status of the organism. In 2-day-cultures, 96% of the bacterial cells were spiral-shaped and four days later a morphological switch to coccoid forms occurred. In 10-day cultures spiral-shaped forms were not found. By 1-DE, proteins with the molecular masses of 87 and 120 kDa were detected in the 2-day cultures that disappeared in cells of 12-day cultures. A protein corresponding in size to the heat shock protein (GroEl homolog, Hsp60) and a 62 kDa protein, the ureaseB-subunit, were identified in extracted proteins of 2-, 8-, and 12-day cultures. 2-DE revealed an increased number of silver-stained spots of 8-day cultures (in average 250 spots) compared with protein extracted from 2-day cells (in average 160 spots). 2-DE immunoblots performed with sera containing antibodies to major H. pylori proteins such as the A- and B-subunits of urease and the Hsp60 showed similar reactivity to surface proteins extracted from 2-, 8-, and 12-day cultures, suggesting that these proteins remain immunologically intact. Pooled sera from infected patients absorbed with spiral-shaped cells showed an almost total blocking of the antibody reactivity to extracted coccoid proteins in 2-DE immunoblot. Eighteen spots were still visible, but this reactivity probably represents a solid overexpression by the coccoid cells of Hsp60 and ureaseB proteins and is thus difficult to block.

Lactobacillus acidophilus autolysins inhibit Helicobacter pylori in vitro

Antibacterial activity of 17 strains of lactobacilli was tested against 10 strains of H. pylori. The inhibition observed was related to the acid production and the low pH attained. No relationship between CagA phenotype of H. pylori strains and tolerance to lactic acid was observed. In mixed cultures, L. acidophilus CRL 639 showed an autolytic behavior after 24 h of culture. At this moment, H. pylori CCUG17874 showed a decrease of 2 log-cycle, and no viable count was detected after 48 h. The bactericidal effect of L. acidophilus CRL 639 in mixed cultures is related to a proteinaceous compound released after cell lysis.

Two-dimensional electrophoretic and immunoblot analysis of cell surface proteins of spiral-shaped and coccoid forms of Helicobacter pylori

Cell surface proteins of the human gastric pathogen Helicobacter pylori extracted during different in vitro growth phases were analyzed by one- and two-dimensional gelelectrophoresis (1-DE and 2-DE) and by 2-DE immunoblot. Broth-cultured H. pylori cells were stained with an acridine-orange dye to monitor the morphological status of the organism. In 2-day-cultures, 96% of the bacterial cells were spiral-shaped and four days later a morphological switch to coccoid forms occurred. In 10-day cultures spiral-shaped forms were not found. By 1-DE, proteins with the molecular masses of 87 and 120 kDa were detected in the 2-day cultures that disappeared in cells of 12-day cultures. A protein corresponding in size to the heat shock protein (GroEl homolog, Hsp60) and a 62 kDa protein, the ureaseB-subunit, were identified in extracted proteins of 2-, 8-, and 12-day cultures. 2-DE revealed an increased number of silver-stained spots of 8-day cultures (in average 250 spots) compared with protein extracted from 2-day cells (in average 160 spots). 2-DE immunoblots performed with sera containing antibodies to major H. pylori proteins such as the A- and B-subunits of urease and the Hsp60 showed similar reactivity to surface proteins extracted from 2-, 8-, and 12-day cultures, suggesting that these proteins remain immunologically intact. Pooled sera from infected patients absorbed with spiral-shaped cells showed an almost total blocking of the antibody reactivity to extracted coccoid proteins in 2-DE immunoblot. Eighteen spots were still visible, but this reactivity probably represents a solid overexpression by the coccoid cells of Hsp60 and ureaseB proteins and is thus difficult to block.

Adhesion of staphylococci to polymers with and without immobilized heparin in cerebrospinal fluid

Infections of cerebrospinal fluid (CSF) shunts constitute a serious clinical problem. The role of adhesion by coagulase negative staphylococci, the most common etiological agent, was examined in vitro to polyvinyl chloride (PVC), silicone, and to PVC and silicone with end-point attached (EPA) heparin. These are flexible materials commonly used in neurosurgical implants. Bacterial adhesion was quantitated by bioluminescence. The bacterial adhesion to biomaterial surfaces increased with increasing concentrations of bacterial cells. Scatchard plot analysis showed continuous negative (concave) slopes, indicating multiple interactions between biomaterial and bacteria. The thermodynamic studies showed a positive value of the standard entropy change at 37 degrees C, which indicates that hydrophobic interactions are important in bacterial adhesion to polymers. Incubation with CSF for 1 h decreased bacterial adhesion in 75% of the samples compared to incubation in buffer. Thus, the contribution of CSF proteins, like fibronectin, for the initial bacterial adhesion might be small. Heparinization of silicone and PVC decreased the numbers of adhered bacteria by 23 to 54% and 0 to 43% compared to unheparinized surfaces. Among putative inhibitors tested, suramin, chondroitin sulfate, and fucoidan inhibited adhesion to 81 +/- 19, 78 +/- 22, and 64 +/- 7%, respectively. These findings indicate that hydrophobic interactions play an important role, and heparinization rendering the biomaterial surface hydrophilic is therefore effective to reduce bacterial adhesion. Heparinized polymers incubated with putative inhibitors may be the optimal way to prevent shunt infections.

Helicobacter pylori interactions with plasminogen

Helicobacter pylori is the causative agent of chronic gastritis, peptic ulcer, and gastric malignancies. A number of virulence factors have been described including several adhesins, a cytotoxin, neutrophil-activating protein, and expression of binding of extracellular matrix proteins, like collagen type IV, laminin, and vitronectin. H. pylori strains commonly express binding of soluble plasminogen. Coccoid forms also express binding. Plasminogen binding was optimal at pH 7.0. The binding is mediated by two cell surface proteins of 42 and 57 kDa. Scatchard plot analysis showed a straight line with a K(d) of 7 x 10(-7) M. Lysine and E-aminocaproic acid inhibited binding. The binding domain on the plasminogen molecule is the fifth kringle, miniplasminogen. Plasminogen is converted to plasmin by tissue plasminogen activator. During H. pylori infection the activity of tissue plasminogen activator is decreased and that of urokinase increased. This is reversed after eradication therapy. The plasminogen binding and conversion to plasmin is the only proteolytic activity of H. pylori, and may enhance tissue penetration and be involved in carcinogenesis.

Exposure of plasma proteins on Dacron and ePTFE vascular graft material in a perfusion model

OBJECTIVES

to compare the exposure of plasma proteins adsorbed onto three vascular graft materials (polytetrafluoroethylene ePTFE and two modifications of polyethyleneterephthalate Dacron).

METHODS

surface exposure of fibronectin, vitronectin, thrombospondin, antithrombin III, IgG, high molecular-weight kininogen, fibrinogen, albumin and plasminogen was studied by incubation with radiolabelled antibodies in a perfusion model. Perfusion times with human plasma were 1, 4, 24 and 48 hours.

RESULTS

all proteins could be detected at 1, 4, 24 and 48 hours after the start of perfusion. Overall, the least amount of proteins adsorbed onto ePTFE.

CONCLUSIONS

the low adsorption of proteins onto ePTFE may be one of the reasons for the lower incidence of infections reported with this material.

Cell surface characteristics of microbiological isolates from human percutaneous titanium implants in the head and neck

Percutaneous implants are commonly associated with several problems, and different failure modes have been described. Infections constitute one serious complication which may lead to the removal of the implant. In contrast to infections around polymer implants, infections around skin-penetrating titanium implants anchored in the temporal bone are often cured by local treatment. Coagulase-negative staphylococci are the most common etiological agents in infections related to polymers whereas Staphylococcus aureus is considered as the main pathogen in infections around metallic implants. Microbial adhesion is a prerequisite for an infection. In the present study, the cell surface of microbes isolated from the skin around skin-penetrating titanium implants, with and without signs of infection, was characterized with respect to expression of cell surface hydrophobicity and to binding of immobilized fibronectin, vitronectin and collagen type 1 which could mediate adhesion. Expression of protein binding was similar in strains isolated from the two groups. No strain expressed a hydrophobic cell surface as determined by two-phase separation, and we conclude that the microenvironment around a titanium implant promotes expression of a hydrophilic rather than a hydrophobic cell surface which in turn makes many infections around a titanium implant curable by local treatment.

Presence of vitronectin and activated complement factor C9 on ventriculoperitoneal shunts and temporary ventricular drainage catheters

OBJECT

The pathogenesis of cerebrospinal fluid (CSF) shunt infection is characterized by staphylococcal adhesion to the polymeric surface of the shunt catheter. Proteins from the CSF--fibronectin, vitronectin, and fibrinogen--are adsorbed to the surface of the catheter immediately after insertion. These proteins can interfere with the biological systems of the host and mediate staphylococcal adhesion to the surface of the catheter. In the present study, the presence of fibronectin, vitronectin, and fibrinogen on CSF shunts and temporary ventricular drainage catheters is shown. The presence of fragments of fibrinogen is also examined.

METHODS

The authors used the following methods: binding radiolabeled antibodies to the catheter surface, immunoblotting of catheter eluates, and scanning force microscopy of immunogold bound to the catheter surface. The immunoblot showed that vitronectin was adsorbed in its native form and that fibronectin was degraded into small fragments. Furthermore, the study demonstrated that the level of vitronectin in CSF increased in patients with an impaired CSF-blood barrier. To study complement activation, an antibody that recognizes the neoepitope of activated complement factor C9 was used. The presence of activated complement factor C9 was shown on both temporary catheters and shunts.

CONCLUSIONS

Activation of complement close to the surface of an inserted catheter could contribute to the pathogenesis of CSF shunt infection.

Bacterial infections of the small intestine and colon

Enterotoxigenic Escherichia coli, Vibrio cholerae O1, Campylobacter jejuni, Salmonella species, and Shigella species are major causes of morbidity and death in diarrheal disease. More recently recognized pathogens are V. cholerae O139 and enterohemorrhagic E. coli. In addition to this, several presumptive virulence factors have been identified in diarrheagenic E. coli and in other species. To confirm these as virulence factors we need good diagnostic tools and good epidemiological studies. These are of vital importance to create vaccines for diarrheal diseases.

A new model to assess staphylococcal adhesion to intraocular lenses under in vitro flow conditions

Adhesion of staphylococcal cells to intraocular lenses coated with heparin was studied under in vitro flow conditions (280 microl min(-1)) at 37 degrees C. The intraocular lenses were incubated with human cerebrospinal fluid for 1 h or with cerebrospinal fluid including 0.50% plasma for 12 h, prior to bacterial challenge. Two strains of Staphylococcus epidermidis selected for this study, were isolated from biomaterial-associated infections. Bacterial adhesion was quantitated by bioluminescence and visualized by fluorescence microscopy of acridine orange stained bacteria. Surface coating with heparin significantly decreased bacterial adhesion of both strains after incubation with cerebrospinal fluid including 0.50% plasma for 12 h (p = 0.0209). However, no difference in bacterial adhesion was obtained between intraocular lenses with and without heparin, after incubation with cerebrospinal fluid for 1 h (p = 0.327). Microscopy showed that more bacteria were present on intraocular lenses without heparin than on intraocular lenses with heparin. The results show that preincubation with a proteinaceous fluid influences subsequent bacterial adhesion to the polymer surface. The results suggest that IOLs with heparin coating may be less prone to bacterial adhesion under perfusion conditions after surface conditioning in human CSF with 0.50% plasma and a preincubation period of 12 h. Heparin coating might be a valuable tool to decrease implant-associated bacterial endophthalmitis.

Granulocyte-macrophage colony-stimulating factor (GM-CSF)-coated implants and their potential for reducing biomaterial-associated infection in neutropenic hosts

The incidence of infections associated with the use of medical biomaterials is high for skin-penetrating devices, when microbes of the normal skin flora like coagulase-positive and coagulase-negative staphylococci dominate as causative organisms. The most serious ones are infections in immunocompromised individuals. A mouse model of subcutaneous staphylococcal infection yielding abscesses in cyclophosphamide-induced neutropenic mice implanted with heparinized polyethylene (H-PE) was used. The present study addresses the question of the effects of implant modification with recombinant granulocyte-macrophage stimulating factor (rGM-CSF) on the course of infection. Our findings demonstrate that such modification reduces the proliferation of bacteria within the abscess and as a consequence limits the dissemination of bacteria from the local infection induced in the neutropenic host.

Plasminogen binding and activation at the surface of Helicobacter pylori CCUG 17874

The binding of iodine-labelled plasminogen to Helicobacter pylori CCUG 17874 was characterized. Inhibition of the binding was observed after preincubation of H. pylori cells with nonradiolabelled plasminogen, lysine, or the lysine analogue epsilon-aminocaproic acid. Fragments of plasminogen, kringles 1 to 3, kringle 4, and mini-plasminogen, were also studied as potential inhibitors. Mini-plasminogen caused total inhibition of the plasminogen binding, while the other fragments caused only partial inhibition. These findings suggest that H. pylori binds specifically the fifth kringle structure of the plasminogen molecule. Plasminogen binding to H. pylori seems to be independent of culture media and independent of the presence of the cytotoxin-associated CagA antigen. Immunoblot analysis identified two plasminogen binding proteins of 57 and 42 kDa. Scatchard plot analysis revealed one binding mechanism with a Kd value of 7 x 10(-7) M. Conversion of H. pylori cell-bound plasminogen to plasmin in the presence of a tissue-type plasminogen activator was demonstrated by digestion of the chromogenic substrate S-2251. No activation was noted when plasminogen or tissue-type plasminogen activator was incubated with H. pylori cells alone. Formation of H. pylori cell surface-bound plasmin may be important to provide a powerful proteolytic mechanism for gastric tissue penetration in type B gastritis and peptic ulcer disease, since plasmin degrades not only fibrin but also extracellular matrix proteins such as various collagens and fibronectin.

Binding of immobilized fibronectin by biliary drain isolates

Occlusion of biliary stents, as the result of bacterial adhesion and colonization onto biliary stents, still remains a major problem. Biliary proteins, such as fibronectin (Fn) and vitronectin (Vn), have been presumed to be involved in the process of bacterial adhesion to biliary biomaterial. In the present study, Fn binding by 5 strains of E. coli isolated from biliary drains or from bile was studied. All strains did not bind detectable amounts of soluble Fn but bound to immobilized plasma Fn. Adhesion of four strains of E. coli to ovalbumin was reduced by periodate treatment of ovalbumin, but adhesion to Fn was unaffected. Adhesion was inhibited by mannose-containing saccharides, trypsin treatment of the protein, and protease treatment of the bacterial cells. Autoradiography showed that components of cell extracts from three E. coli strains bind 125I-Fn but not a 150 kD Fn fragment. The findings indicate that the adhesion of these bacteria to Fn is a protein-protein interaction, inhibited by D-mannose, and possibly mediated by fimbrial components.

The lactosylceramide binding specificity of Helicobacter pylori

The possible role of glycosphingolipids as adhesion receptors for the human gastric pathogen Helicobacter pylori was examined by use of radiolabeled bacteria, or protein extracts from the bacterial cell surface, in the thin-layer chromatogram binding assay. Of several binding specificities found, the binding to lactosylceramide is described in detail here, the others being reported elsewhere. By autoradiography a preferential binding to lactosylceramide having sphingosine/phytosphingosine and 2-D hydroxy fatty acids was detected, whereas lactosylceramide having sphingosine and nonhydroxy fatty acids was consistently nonbinding. A selective binding of H. pylori to lactosylceramide with phytosphingosine and 2-D hydroxy fatty acid was obtained when the different lactosylceramide species were incorporated into liposomes, but only in the presence of cholesterol, suggesting that this selectivity may be present also in vivo . Importantly, lactosylceramide with sphingosine and hydroxy fatty acids does not bind in this assay. Furthermore, a lactosylceramide-based binding pattern obtained for different trisaccharide glycosphingolipids is consistent with the assumption that this selectivity is due to binding of a conformation of lactosylceramide in which the oxygen of the 2-D fatty acid hydroxyl group forms a hydrogen bond with the Glc hydroxy methyl group, yielding an epitope presentation different from other possible conformers. An alternative conformation that may come into consideration corresponds to the crystal structure found for cerebroside, in which the fatty acid hydroxyl group is free to interact directly with the adhesin. By isolating glycosphingolipids from epithelial cells of human stomach from seven individuals, a binding of H.pylori to the diglycosylceramide region of the non-acid fraction could be demonstrated in one of these cases. Mass spectrometry showed that the binding-active sample contained diglycosylceramides with phytosphingosine and 2-D hydroxy fatty acids with 16-24 carbon atoms in agreement with the results related above.

Virulence properties of Escherichia coli isolated from Ethiopian patients with acute or persistent diarrhoea

Escherichia coli strains isolated from faecal specimens of 108 Ethiopian patients with acute watery diarrhoea (n = 30), acute bloody (n = 9), and persistent (n = 25) diarrhoea, and from 44 patients who recently had recovered from diarrhoea were analyzed for the presence of virulence factors using DNA probes, and for adhesion to HeLa cells. Eighty-two patients were under five years of age. Enterotoxigenic E.coli (ETEC) were most frequently isolated (63 patients, 58%). Eighteen of the ETEC strains also hybridized with probes for EPEC adherence factor (EAF) and Enteroaggregative (EAgg) adherence. Enteroaggregative E. coli (EAggEC) were more frequently isolated than EAF positive E.coli, and more frequently from patients with persistent diarrhoea (10/25) than from patients with acute diarrhoea (11/39). In total, 103 of the patients harboured faecal E. coli which hybridized with one or more of the virulence probes. Haemagglutination of one or more erythrocyte species was expressed by 65/70 strains. Using monoclonal antibodies to Colonization Factor Antigen I and Coli Surface antigens 1-5, only 18/66 strains were found to produce one or more of these adhesions and no more than 15 of 43 ETEC strains were agglutinated by the antisera to these adhesins. Forty-nine strains adhered to HeLa cells in autoaggregative (23 strains), localized (17 strains) or diffuse (9 strains) pattern. The study shows that E.coli strains carrying genes for the different virulence factors are prevalent in Ethiopia. Testing for the presence of these virulence factors, as well as for putative colonization factor antigens, should be included in epidemiological studies in this area.

Altered immune response to staphylococcal antigens in long-lasting implanted mice

Staphylococcal infections constitute one of the main problems associated with clinical applications of various prosthetic medical devices (biomaterials). As the magnitude of the infection risk depends often on the duration of device installation, and the incidence of infections is higher in skin-penetrating devices, we studied some parameters of specific immune response to staphylococcal antigens in mice subcutaneously (s.c.) implanted for three months with heparinized polyethylene (H-PE). Three weeks before the evaluation of immune response, mice (implanted and non-implanted) were s.c. infected with 10(7) of Staphylococcus aureus Cowan 1. The proliferation of lymph node cells was determined on the basis of 3H-thymidine incorporation in 3-days cultures stimulated with: staphylococcal lipoteichoic acid (LTA), protein A (SpA), alpha-toxin, or with phytohemagglutinin (PHA). Moreover, the levels of specific antibodies to staphylococcal antigens were determined in serum samples (ELISA against: LTA, SpA, alpha-toxin). The data obtained indicate that long-lasting implantation caused evident changes in proliferative activity of lymphocytes and humoral response to staphylococcal antigens. It enhances alpha-toxin and LTA stimulated proliferation of lymph node lymphocytes in vitro. In contrast, H-PE-implanted animals demonstrated a significant decrease in the production of anti-SpA IgG2a and IgG2b and increase in the synthesis of anti-LTA IgG1 antibodies.

Enterobacteriaceae found in high numbers in fish, minced meat and pasteurised milk or cream and the presence of toxin encoding genes

Enterobacteriaceae were found in high numbers after storage at 7 degrees C in 6% of consumers packs of pasteurised milk or cream, in 31% of retailed fish and in 100% of retail packs of minced meat. Seventy two fresh-water fishes, 40 packs of minced meat and 430 milk packs were sampled. One hundred and eighty four isolates were randomly picked from Tryptone glucose extract (TGE) agar (30 degrees C for 3d) or Violet red bile glucose (VRBG) agar (37 degrees C for 1d). In minced meat, Serratia liquefaciens, Hafnia alvei, Rahnella aquatilis were frequently encountered. On fish, the most frequently found species were R. aquatilis, and in milk, the dominating species were S. liquefaciens, H. alvei and R. aquatilis. One to three isolates of Citrobacter freundii were found in all three food categories. Using a polymerase chain reaction (PCR) technique, the gene of Escherichia coli heat-labile toxin (lt) was indicated in one fish isolate of R. aquatilis whereas heat-stable toxin genes (s.t.) were indicated in four H. alvei isolates, two originating from fish and two from minced meat. Positive PCR-reaction for vero cytotoxin genes were found in one H. alvei strain originating from fish (vt1), in two S. liquefaciens strains from minced meat (vt2), and in a C. freundii reference strain. One of the st-positive H. alvei strains from meat harboured the eaeA gene involved in the attaching phenotype of enteropathogenic E. coli.

Doxorubicin reversibly decreases the antithrombogenicity of heparin immobilized on central venous catheters

This is an in vitro study of the effects of doxorubicin on heparin immobilized on polyvinyl chloride (PVC) tubing. Doxorubicin contains an amino group that binds up to 16 heparin molecules, forming insoluble complexes if they are added to the same infusion. Three systems were tested: doxorubicin in perfusing blood, cerebrospinal fluid, and 0.9% sodium chloride (NaCl). The antithrombogenicity of immobilized heparin is impaired on exposure to doxorubicin. However, the reaction is reversible provided the PVC tubing system is thoroughly washed. Heparinized tubing perfused for 12 hours in blood with doxorubicin (0.027 mg/mL) decreased the activity of the immobilized heparin to 6.0% compared with 43% of that exposed to blood only. Exposure to doxorubicin (0.27 mg/mL) for 15 minutes in NaCl decreased the activity to 3% compared with that of NaCl only. Continuous washing for 10 minutes (8 mL/min) resulted in regained activity. This indicated a reversible reaction between immobilized heparin and doxorubicin. Cyclophosphamide, netilmicin, and gentamicin did not affect the antithrombogenicity of heparin in any solution.

Quantitation of bacterial adhesion to polymer surfaces by bioluminescence

Quantitation of microbes adhering to a surface is commonly used in studies of microbial adhesion to different surfaces. We have quantified different staphylococcal strains adhering to polymer surfaces by measuring bacterial ATP (adenosine triphosphate) by bioluminescence. The method is sensitive, having a detection limit of 10(4) bacterial cells. Viable counting of bacterial cells may yield falsely low results due to the presence of "dormant" and adherent bacteria. By using bioluminescence, this can be avoided. Cells of different bacterial species and cells of strains of the same species were shown to differ significantly in their basal ATP content (8.7 x 10(-13) - 5.2 x 10(-22) MATP). The size of adherent and planktonic bacteria decreased with time (0.7 micron-->0.3 micron, 20 days). During incubation in nutrient-poor buffer ("starvation"), the ATP content of adherent bacteria decreased after 24-96 h whereas that of planktonic bacteria was stable over 20 days. The presence of human serum or plasma did not interfere significantly with the test results. Since the ATP concentration of bacterial strains of different species varies and is also influenced by the growth conditions of bacteria (solid or liquid culture medium), a species-specific standard curve has to be established for bacteria grown under the same culture conditions. We conclude that the method is a sensitive tool to quantify adherent bacteria during experiments lasting for less than 6 h and constitutes a valuable method to be used in conjunction with different microscopical techniques.

In vitro anti-staphylococcal activity of heparinized biomaterials bonded with combinations of rifampicin

Biomaterial implants in various human body tissues are highly susceptible to bacterial colonization. We report here on the coating of heparinized biomaterials with heparin binding extracellular matrix proteins giving special regard to the efficient adsorption and slow release of antibiotics. Heparin was partially degraded and the resulting fragments were covalently end-point attached to 0.5 cm long silicone biomaterial surface. Collagen type I was immobilized on the heparinized biomaterials and then cross-linked with acyl-azide or carbodiimide. Finally, the resulting biosurfaces were exposed to antibiotics, i.e. rifampicin in combination with cefuroxime, fusidic acid, ofloxacin or vancomycin, respectively. The antibiotic bonded biomaterials were evaluated for their anti-staphylococcal activity after elution in NaCl, serum or blood by measuring the zones of inhibition for S. epidermidis strain RP12. Furthermore, we examined the in-vitro colonization resistance to S. epidermidis RP12 for these combinations of rifampicin-bonded biomaterials by an ATP bioluminescence assay. The ATP measurements showed that initially adherent bacteria were eradicated from the polymer surface, for at least 24 or 48 h (fusidic acid > cefuroxime > vancomycin > ofloxacin). The anti-staphylococcal activity of rifampicin-fusidic acid bonded heparinized biomaterials seems of sufficient duration and efficacy to merit testing in an animal model.

Fibronectin binding by Propionibacterium acnes

Strains of Propionibacterium acnes, isolated from different kinds of orthopaedic and biomaterial-associated infections and from skin flora were shown to express binding of soluble as well as immobilized fibronectin. Among these 7 strains isolated from orthopaedic infections, 2 from breast prostheses, and 9 skin isolates, 2, 2, and 5 strains respectively bound immobilized fibronectin. The fibronectin binding was sensitive to protease and heat treatment, and was inhibited by a cell surface extract from one of the binding strains. In SDS-PAGE and autoradiography of cell surface extracts, a band corresponding to a MW of about 80 kD reacted with fibronectin and the 150 kD fragment of fibronectin. Binding to fibronectin and the 150 kD fragment of fibronectin could be inhibited with heparin. We thus present a first Fn binding protein of P. acnes, a surface exposed protein of 80 kD. None of the strains bound soluble collagen, and only one strain expressed weak binding of vitronectin and bone sialoprotein II.

Protein depositions on one hydrocephalus shunt and on fifteen temporary ventricular catheters

Biomaterials are commonly used in modern medicine. Proteins are adsorbed to the surface of the biomaterial immediately after insertion. This report demonstrates the presence of adsorbed proteins in one infected cerebrospinal shunt from a child with hydrocephalus and on fifteen temporary ventricular catheters from adult patients with spontaneous or traumatic brain injuries. Depositions of vitronectin, fibrinogen and thrombospondin-fibronectin to some extent--on the shunt surface was imaged by field-emission scanning electron microscopy. Vitronectin, fibronectin, fibrinogen, and thrombospondin on the ventricular catheters were shown with radio-actively labelled antibodies. Furthermore, protein adsorption from human cerebrospinal fluid to heparinized and unheparinized polymers was studied under flowing conditions in vitro. On heparinized polymer, significantly reduced levels of vitronectin, fibronectin, and thrombospondin were exposed, as measured after 4 hours in vitro perfusion. After 24 hours perfusion, the differences in protein exposition between heparinized and unheparinized polymers were substantially reduced.

Specific immune response to staphylococcal antigens during long-lasting biomaterial implantation

Biomaterial-associated infections caused by staphylococci are one of the main therapeutic problems in modern medicine. There is no doubt that local disfunction of polymorphonuclear leukocytes and macrophages predisposes to such infections. However, it is not clear how implantation of a foreign body influences the antibacterial immune response. We analyzed some parameters of the specific immune response to staphylococcal antigens, in mice implanted for 3 months with heparinized polyethylene. Three weeks before the evaluation of the immune response, mice (implanted and non-implanted) were infected i.p. with 2 x 10(7) cells of Staphylococcus aureus Cowan 1. The proliferation of splenocytes was determined on the basis of [3H]thymidine incorporation in cultures stimulated with staphylococcal lipoteichoic acid, protein A, alpha-toxin, or phytohemagglutinin. Moreover, the level of specific antibodies to staphylococcal antigens was determined in serum samples (ELISA with the antigens lipoteichoic acid, protein A, and alpha-toxin). The data obtained indicate that long-lasting implantation caused evident changes in proliferative activity of lymphocytes and in humoral response to staphylococcal antigens. It enhanced spontaneous and lipoteichoic acid- or alpha-toxin-stimulated proliferation of splenocytes, in vitro. In contrast, heparinized polyethylene-implanted animals showed a significant decrease in the production of anti-protein A IgG2b and anti-alpha-toxin IgG2a and IgG2b.

Ribotype delineation and description of Staphylococcus sciuri subspecies and their potential as reservoirs of methicillin resistance and staphylolytic enzyme genes

Three subspecies of Staphylococcus sciuri, S. sciuri subsp. sciuri Kloos, Schleifer, and Smith 1976, 23AL emend. Kloos et al. 1997 [corrected], S. sciuri subsp. carnaticus subsp. nov., and S. sciuri subsp. rodentium subsp. nov., are described on the basis of their ribotype patterns, DNA-DNA liquid hybridization data, and phenotypic characteristics. Normalized ribotyping subdivided the S. sciuri patterns into three blocks of patterns, each corresponding to a subspecies. Each subspecies formed a separate, well-defined DNA similarity group when DNA-DNA hybridizations were conducted under stringent (70 degrees C) reassociation conditions. S. sciuri subsp. sciuri could be distinguished from the other subspecies on the basis of its ability to produce acid from D-cellobiose, alkaline phosphatase activity, and inability to produce either clumping factor or protein A. S. sciuri subsp. carnaticus could be distinguished by its ability to produce acid aerobically from D-xylose and maltose, inability to produce acid from D-melezitose, and smaller colony size on P agar. S. sciuri subsp. rodentium could be distinguished by its positive reaction in the latex agglutination test for clumping factor and/or protein A and generally higher frequencies and levels of oxacillin and methicillin resistance. All 40 strains of S. sciuri tested (including representatives of all three subspecies) hybridized with the mecA gene probe. All strains of S. sciuri subsp. sciuri, 79% of the strains of S. sciuri subsp. carnaticus and 89% of the strains of S. sciuri subsp. rodentium exhibited extracellular, staphylolytic enzyme activity. This activity was associated with an enzyme(s) that immunoblotted with a lysostaphin-specific monoclonal antibody; however, only three strains hybridized with a lysostaphin (end) gene probe. The type strain of S. sciuri subsp. carnaticus is DD 791 (= ATCC 700058), and the type strain of S. sciuri subsp. rodentium is DD 4761 (= ATCC 700061).

A case control study of chorioamniotic infection and histological chorioamnionitis in stillbirth

In order to elucidate the role and aetiology of chorioamnionitis in stillbirth a case referent study was carried out in 58 pregnant women with late foetal death (cases) and in 58 pregnant women at term with live foetus (referents) matched for age and parity in Maputo Mozambique. Samples from women, stillborns and liveborns, were collected for microbiological and histological assessment. Histological chorioamnionitis was diagnosed in 96% of the cases and in 67% of the referents (OR = 13.5; 95% CI: 2.9-123.9). Escherichia coli was the species most frequently isolated in stillborns; in 14/16 (88%) cases it was isolated from intracardiac fluid. E. coli was associated with chorioamnionitis in 28% of the stillborns as compared to 5% of the referents (OR = 6.9; 95% CI: 1.4-65.4). No group B streptococci were recovered from any placenta or newborn. Vasculitis was present in 12 (21%) cases and in 3 (5%) referents (OR = 4.8; 95%, CI: 1.2-27.7). Histological chorioamnionitis was thus associated with stillbirth. E. coli was common in stillborns. The presence of vasculitis in one fifth of the stillborns indicated that the foetus was alive at the onset of infection.

Vitronectin may mediate staphylococcal adhesion to polymer surfaces in perfusing human cerebrospinal fluid

Prosthetic devices are frequently used for temporary or permanent drainage of cerebrospinal fluid (CSF), i.e., ventricular catheters with or without external monitoring devices and shunts. Infections constitute a serious complication in the use of biomaterials in contact with CSF; coagulase-negative staphylococci (CNS) are the most common aetiological agents. In the present study, polyvinylchloride (PVC) and PVC with endpoint-attached heparin were exposed to human CSF under perfusion to mimic conditions in vivo. Adhesion of strains of CNS isolated from patients with or without biomaterial-associated infection was determined: (i) after pre-incubation with fibronectin (Fn) or vitronectin (Vn) to block bacterial surface binding structures; and (ii) after preincubation of biomaterials with antibodies to Fn or Vn to block exposure of bacteria-binding domains on these host proteins. Pre-incubation of bacterial cells with Vn significantly reduced subsequent adhesion to polystyrene precoated with Vn 0.5 microg/well. When PVC pre-exposed to CSF was incubated with antibodies to Vn, subsequent bacterial adhesion of a Vn-binding strain, S. epidermidis 5703, was significantly reduced. The study shows that Vn may mediate adhesion of CNS in the presence of CSF. However, strains retrieved from biomaterials did not express binding of Vn or Fn to a higher extent than non-biomaterial-associated strains. Expression of heparin binding under static conditions did not correlate with staphylococcal adhesion to heparinised polymers under perfusion with CSF. The extent of adhesion of staphylococci to heparinised PVC was either reduced or the same as to unheparinised PVC.

Vitronectin-binding staphylococci enhance surface-associated complement activation

Coagulase-negative staphylococci are well recognized in medical device-associated infections. Complement activation is known to occur at the biomaterial surface, resulting in unspecific inflammation around the biomaterial. The human serum protein vitronectin (Vn), a potent inhibitor of complement activation by formation of an inactive terminal complement complex, adsorbs to biomaterial surfaces in contact with blood. In this report, we discuss the possibility that surface-immobilized Vn inhibits complement activation and the effect of Vn-binding staphylococci on complement activation on surfaces precoated with Vn. The extent of complement activation was measured with a rabbit anti-human C3c antibody and a mouse anti-human C9 antibody, raised against the neoepitope of C9. Our data show that Vn immobilized on a biomaterial surface retains its ability to inhibit complement activation. The additive complement activation-inhibitory effect of Vn on a heparinized surface is very small. In the presence of Vn-binding strain, Staphylococcus hemolyticus SM131, complement activation on a surface precoated with Vn occurred as it did in the absence of Vn precoating. For S. epidermidis 3380, which does not express binding of Vn, complement activation on a Vn-precoated surface was significantly decreased. The results could be repeated on heparinized surfaces. These data suggest that Vn adsorbed to a biomaterial surface may serve to protect against surface-associated complement activation. Furthermore, Vn-binding staphylococcal cells may enhance surface-associated complement activation by blocking the inhibitory effect of preadsorbed Vn.

Fibronectin exposes different domains after adsorption to a heparinized and an unheparinized poly(vinyl chloride) surface

The adsorption of fibronectin to poly(vinyl chloride) catheters with end-point attached (EPA) heparin and tridodecylmethylammonium chloride-heparinized poly(vinyl chloride) was compared to that of unheparinized poly(vinyl chloride) using antibodies directed against four different domains of the protein. After perfusion of human plasma on the EPA-heparinized surface, the exposure of the N-terminal 29-kD fragment increased during the first 5 h of perfusion. Also, the exposure of the 30-kD gelatin-binding and 65-kD cell-binding fragments increased with time, but at a lower level. On the unheparinized catheter, low levels of antibodies bound to the different domains, and the binding showed little variation during the 5 h of plasma perfusion, indicating that the fibronectin molecule does not change configuration to a significant extent on this surface after the initial adsorption. When the EPA-heparinized surface was preabsorbed with human fibrinogen before incubation with fibronectin, significantly less of the 29-kD (fibrin-binding) domain was exposed, and the 30-kD domain was not exposed. Exposure of the 31- and 65-kD domains increased after preadsorption of fibrinogen to the surface. Since fibronectin has heparin-binding domains, it adsorbs differently to a heparinized versus an unheparinized surface. This will influence subsequent binding of other proteins to the surface, as well as potential binding of microbes. The use of antibodies to defined domains of the fibronectin molecule provides a powerful tool in studies of configurational changes of fibronectin after adsorption to different surfaces.

Immunoblot assay for serodiagnosis of Helicobacter pylori infections

An immunoblot assay for the serological diagnosis of Helicobacter pylori infection was evaluated. Serum samples from patients whose gastric biopsy specimens were known to be positive or negative for H. pylori on culture were used to establish interpretive criteria for the immunoblot assay. A panel of sera from patients with diseases other than H. pylori infection and sera from healthy blood donors were included to validate these criteria. All sera were initially assessed in an enzyme immunoassay (Ge-EIA), based on acid glycine-extracted cell surface proteins of H. pylori NCTC 11637. The same antigen extract was used in the immunoblot assay. In addition, the Ge-EIA and the immunoblot assay were compared with a commercially available EIA (Seradyn, Color Vue Pylori). Bands of 110/120 kDa and/or two of five low-molecular-mass proteins (26, 29, 30, 31, and 33 kDa, in any combination) showed a strong correlation with the H. pylori culture-positive patients (97.5%) compared to the correlation obtained with the EIA results (Ge-EIA, 87.5%; Seradyn EIA, 92.5%), and the antibody responses to these proteins were considered specific reactions. In 37 of 40 serum samples from culture-negative patients and also in sera from patients with other disorders, a moderate antibody reactivity to the medium-size proteins (43 to 66 kDa) was observed, and these were considered not valuable for a specific immunoblot assay. Among sera from culture-positive patients, 39 of 40 serum samples were defined to be immunoblot positive, and from among sera from culture-negative patients, 3 of 40 serum samples were defined to be immunoblot positive. The use of sera from patients with negative cultures for H. pylori as negative controls may decrease the sensitivity due to sampling error and false-negative culture results. Immunoblot assay-positive results were detected among 10% of sera from patients with other diseases, whereas they were detected among 42.5% of sera by the Ge-EIA and 47.5% of sera by the Seradyn-EIA. The higher number of EIA-positive sera in this group reflects a possible cross-reactivity (false-positive EIA result). Of the blood donors, representing asymptomatic but possibly colonized subjects, 24% were immunoblot positive. In conclusion, our data indicate that immunoblotting is more sensitive as well as more specific than EIA. Moreover, it permits detection of antibody responses to specific antigens, e.g., the cytotoxin-associated CagA protein, which may have pathological implications.

Syphilis seroprevalence among pregnant women and its role as a risk factor for stillbirth in Maputo, Mozambique

OBJECTIVE

To elucidate the role of current syphilis as a risk factor for foetal death.

METHODS

Sera were obtained from 57 women with third trimester foetal death (cases) and 58 women with foetus alive (controls) matched for age and parity. All sera reactive in qualitative Rapid Plasma Reagin (RPR) analyses were tested with serial twofold dilutions to determine endpoint flocculation titres and tested with the micro-haemagglutination assay for Treponema pallidum (MHA-TP). Placental biopsies were sectioned and stained by haematoxylin-eosin and Warthin-Starry for light microscopy.

SETTING

Central Hospital, in Maputo, Mozambique, from January 1990 to June 1991.

RESULTS

The MHA-TP was reactive in 42% of cases and in 12% of controls (OR = 5.3; 95% CI: 1.9-15.4). The RPR card test was reactive at the dilution of 1.32 or greater in 28% of cases and in 7% of controls. All these results were confirmed by MHA-TP (OR = 5.3; 95% CI: 1.5-15.4). In 9/28 (32%) MHA-TP seroreactive women (7 cases and 2 controls) placental morphological changes indicated syphilitic infection.

CONCLUSION

MHA-TP seroreactivity and high titre RPR were associated with stillbirth. Morphological changes presumptive of syphilis infection were found in 32% placentas histologically studied. Syphilis is a risk factor for foetal death in Maputo, Mozambique.

A particle agglutination assay for rapid identification of heparin binding to coagulase-negative staphylococci

The heparin-binding properties of six different species of coagulase-negative staphylococci were examined by a particle agglutination assay. Heparin (mol. wt 4000-6000), mildly treated with sodium periodate, was covalently coupled to amino-modified latex beads (0.72 micron diameter). The particle agglutination assay was validated by comparing results with the adhesion (percentage binding of adherent cells) of coagulase-negative staphylococcal strains to heparinised microtitration plates. Of 38 different coagulase-negative staphylococcal strains tested, 30 showed agglutination reactivity with heparin-coated latex beads. Strains of different coagulase-negative staphylococcal species agglutinated heparin-coated latex beads to various extents (e.g., cells of Staphylococcus haemolyticus strains reacted more strongly than cells of S. epidermidis strains). The agglutination reaction was significantly inhibited by fucoidan, suramin, lambda-carrageenan and other sulphated compounds, but not by non-sulphated carbohydrate polymers such as hyaluronic acid. Agglutination of staphylococcal cells with heparin-coated latex beads was completely blocked by a cell-surface extract. These results suggest that structures responsible for heparin binding are exposed on the cell surface.

Stillbirths and intrauterine infection, histologic chorioamnionitis and microbiological findings

OBJECTIVE

To analyze whether placental inflammation is associated with stillbirth in Zimbabwe.

METHOD

Placentas from 66 stillbirths (> 22 weeks' gestation; patients with congenital malformations, diabetes or preeclampsia were excluded) and 66 term live births were studied for the presence and severity of chorioamnionitis. The morphological results were compared with earlier presented microbiological findings in the same material.

RESULTS

Chorioamnionitis was present in 79% of stillbirths and 30% of live births (O.R. 8.5, 95% C.I. 4.0-18). Nine percent of stillbirths but no live births presented vasculitis of the chorionic plate, which verified an inflammatory response from the infant (O.R. 14, 95% C.I. 2.8-72). The same types of microorganisms were isolated from stillbirths and liveborns, but Escherichia coli and group B streptococci were more frequent among stillbirths.

CONCLUSIONS

Morphological chorioamnionitis occurred 2.6 times more often in women with stillbirths than in women with live births. In 9% of stillbirths the infant showed an inflammatory response. Thus the infant was alive when the infection occurred and it is therefore reasonable to assume that infection was the cause of death.

The proliferation of human T lymphocytes stimulated by Helicobacter pylori antigens

Fractionated mononuclear cells (MNCs) were obtained from peripheral blood of healthy human volunteers, seronegative for H. pylori antibodies. The MNCs were stimulated in culture with whole live or heat-killed H. pylori cells or with bacterial cell surface (SA) or cytoplasmic (CA) antigens. There was a marked proliferative response of T cells in cultures stimulated with 10(5) cells/well of live H. pylori, 5 micrograms/well of CA or 5-20 micrograms/well of SA. However, no proliferation was observed in MNC cultures containing higher "doses" of live H. pylori organisms (10(7)/well) or CA (20 micrograms/well). Moreover, higher "doses" of the bacteria or CA entirely inhibited the response of T cells to PHA.

Invasion of tissue culture cells by diarrhoeagenic strains of Escherichia coli which lack the enteroinvasive inv gene

Invasive Escherichia coli strains of certain serotypes invade by the same mechanism as the Shigella sp. It has been proposed that invasion of epithelial cells by EPEC strains may also occur; this is a previously overlooked property. In the present study E. coli strains isolated from patients with diarrhoea or ulcerative colitis, lacking the inv plasmid mediating classical invasion, but hybridizing with probes for different adhesins, were analyzed for their ability to invade HeLa and Caco-2 cells. The majority of strains invaded Caco-2 cells to a higher extent than HeLa cells. Adhesion to Caco-2 cells was a prerequisite for subsequent invasion of the cells but EAF, eae, EAgg and other known virulence factors were not sufficient to mediate invasion. In 8/9 E. coli strains invasion was enhanced after growth under iron restriction. Growth during anaerobic conditions did not influence subsequent invasion by E. coli strains whereas 6/9 strains had their invasive ability significantly decreased after growth in the presence of 1% glucose. The invasive process was inhibited by mannose but not by lactose, fucose or galactose. Our data indicate that strains of E. coli may invade Caco-2 cells by novel mechanisms which require adhesion to the cells but which differ from those of Salmonella sp., Yersinia sp., Shigella sp. and classical enteroinvasive E. coli.