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Biomedical subjects

A Ljungh

Publications and source records attributed to A Ljungh.

At least 91 records · Page 5Linked to original sources
PubMed1994

Protein adsorption of poly(ether urethane) surfaces modified by amphiphilic and hydrophilic polymers.

A commercial biomedical poly(ether urethane), Pellethane 2363-80AE, was surface modified through the use of amphiphilic polymeric additives, and through surface grafting with poly(ethylene glycol), PEG. Two different amphiphilic polymers, Polymer C and Pluronic PE9400, were used as additives. Polymer C, a segmented polyurethane, was prepared from PEG1500, 4,4'-diphenylmethane diisocyanate and a C16-C18 monoglyceride chain extender. Pluronic PE9400 is a propylene oxide-ethylene oxide tri-block co-polymer obtained from BASF. Adsorption of human albumin and fibrinogen to the modified surfaces was studied by means of radiolabelled proteins. By contact angle measurements and X-ray photoelectron spectra the amphiphilic polymers were shown to accumulate at the polyurethane surfaces. Adsorption of fibrinogen, in particular, was significantly reduced by the amphiphilic additives to levels similar to those obtained for Pellethane surfaces grafted with PEG 20,000. In vitro clotting times for citrate-buffered blood in contact with the amphiphilic surfaces increased as compared with the unmodified ones.

Adsorption↗
PubMed1994

Cell surface hydrophobicity and adherence to extra-cellular matrix proteins in two collections of methicillin-resistant Staphylococcus aureus.

Non-specific and specific mechanisms of adherence have been examined in two collections of methicillin-resistant Staphylococcus aureus (MRSA). Determination of hydrophobicity by salt aggregation, hydrophobicity indices and of adherence to the extra-cellular matrix proteins fibronectin, vitronectin, laminin and collagen type 1 have failed to reveal any correlation with phage-type, plasmid profile or antibiogram. Further, the strain collections, made over a period of years in two countries, differ markedly in their adherence characteristics; MRSA are heterogeneous in this respect. Such heterogeneity may explain the polarization of views on the epidemicity or 'virulence' of MRSA. With the exception of adherence to collagen a small group of methicillin sensitive S. aureus had characteristics intermediate between the two groups of MRSA.

Agglutination Tests↗
PubMed1994

Enteropathogenic and enteroadherent-aggregative Escherichia coli in children with persistent diarrhoea and malnutrition.

Our investigation of 61 children with persistent diarrhoea and malnutrition (PDM) aimed to characterize in them the range of enteropathogenic E. coli. Age- and sex-matched control groups consisted of 42 healthy children and 16 children with marasmus but without diarrhoea. E. coli isolates from stool cultures were serotyped, examined for Vero cells cytotoxicity, tested for enterotoxin production (LT, ST, VTI, and VTII). Synthetic oligonucleotide probes were used to test for enteroinvasivity, EPEC adherence factor, and for EAggEC. Classical E. coli serotypes commonly associated with diarrhoea (O18, O26, O119, O126) were isolated from six of 60 (10%) children with PDM. Serotype O126 was isolated from two of 42 (4.8%) healthy children and serotype O119 from one of 16 (6%) marasmic controls. Testing for Vero toxin production was negative in all isolates. Classical ETEC were confirmed in four of 60 (ST 2; LT 2) cases of PDM; no ETEC were recovered from 58 control patients. EAggEC were identified in five children with PDM and in five healthy controls without diarrhoea or malnutrition. This controlled study has shown that, in The Gambia, E. coli carrying known virulence factors are prevalent but, with the exception of enterotoxigenic E. coli, the various forms of pathogenic E. coli do not seem to be important pathogens in children with persistent diarrhoea.

Bacterial Adhesion↗
PubMed1994

Promotion of Escherichia coli adherence to rubber slices by adsorbed fibronectin.

Biomaterial-associated infections are a problem in the use of endoprosthetic materials in the palliative treatment of malignant obstructive jaundice. Fibronectin has been reported to mediate adherence of bacteria to host tissue and biomaterials. Adsorption of fibronectin to rubber--representing material used for biliary drainage--and subsequent adherence of Escherichia coli strain PSS1 and E. coli strain NG7C (which binds to immobilised fibronectin) were investigated. Quantitative adsorption of fibronectin to rubber slices was studied with 125I-labelled, purified human plasma fibronectin. In buffer solutions, fibronectin showed a high affinity for rubber slices. Adherence of the E. coli strains to uncoated rubber slices was similar and was significantly inhibited by the presence of plasma components and bile. Adherence of E. coli PSS1 to fibronectin-coated slices was poor. In contrast, E. coli NG7C adhered efficiently to coated slices in proportion to the amount of adsorbed fibronectin; adherence was not reduced by the presence of albumin or bile, or the fibronectin-binding ligands gelatin, heparin and fibrinogen. However, pre-digestion of coated slices with trypsin significantly reduced adherence.

Adsorption↗
PubMed1994

Orally administered phospholipids inhibit abdominal rubber-drain-induced bacterial translocation in the rat.

In order to determine the influence of phospholipid on abdominal biomaterial-induced bacterial translocation (BT), phsophatidylcholine (PC) or phosphatidylinositol (PI) was administered orally or intraperitoneally in rats with intraperitoneal implantation of 7-cm2 rubber drain pieces. Two days after surgery, the incidence of translocation to mesenteric lymph nodes and liver significantly decreased, the adherence of 3H-labeled Escherichia coli to the ileal mucosa was significantly inhibited and the phagocytic and bactericidal capacity of peritoneal macrophages increased in animals with PC or PI administered orally, but not intraperitoneally, as compared with rats without phospholipid administration. Scanning electron microscopy revealed a coating layer on the surface of the intestinal mucosa in phospholipid-gavaged rats. Thus, the results in the present study imply that oral, but not intraperitoneal, PC of PI administration reduces enteric BT induced by intraperitoneal drain implantation.

Administration, Oral↗
PubMed1994

An incident case-referent study of stillbirths at Harare Maternity Hospital: socio-economic and obstetric risk factors.

This incident case-referent study was conducted at Harare Maternity Hospital in 1989-1990 on 104 consecutive cases of stillbirth with unknown aetiology and 96 age- and parity-matched referents. Information was collected by interviewing the women following a standardized form and by review of antenatal cards. None of the women refused to participate. The most significant obstetric risk factors were prevalence of earlier stillbirths (odds ratio, OR = 6.1) and miscarriages (OR = 4.8). Low height and body mass index also increased the risk of having a stillborn baby significantly as well as a history of flue-like illness during pregnancy (OR = 4.6). The latter may have stimulated the women to book early causing the unexpectedly high OR for early booking among these cases. The pattern for the socio-economic risk factors was not easy to interpret. The most striking finding was the U-shaped relationship between socio-economic status and stillbirths with a higher risk among those with low and high status.

Adolescent↗
PubMed1993

Phospholipid impregnation of abdominal rubber drains: resistance to bacterial adherence but no effect on drain-induced bacterial translocation.

In order to evaluate the effect of surface modification of biomaterials on bacterial adherence and bacterial translocation after intraperitoneal biomaterial implantation, phosphatidylcholine- or phosphatidylinositol-impregnated rubber drain pieces, which had been intraperitoneally implanted in the rat for 2 and 7 days, or unimplanted, were incubated in vitro with 3H-labelled Escherichia coli and Enterobacter cloacae. As compared with unimpregnated pieces, the adherence of bacteria significantly decreased to phosphatidylcholine- and phosphatidylinositol-impregnated rubber drain pieces that were either unimplanted or implanted for 2 days, but not for 7 days. The supplementation of albumin in the medium reduced the adherence of bacteria to the unimplanted, unimpregnated drain pieces, but did not further decrease adherence of bacteria to the unimplanted, phospholipid-impregnated brain pieces. Bacterial growth was inhibited after incubation in nutrient broth supplemented with phospholipids. The incidence of enteric bacterial translocation induced by intraperitoneal drain implantation did not differ between phospholipid-impregnated and unimpregnated drain pieces. Scanning electron microscopy revealed a large amount of biofilm and fibrous deposition on the surface of the implanted, phospholipid-impregnated rubber drain pieces. Thus, phospholipid impregnation of rubber drains reduces bacterial adherence and inhibits bacterial growth, without influencing the incidence of bacterial translocation.

Abdomen↗
PubMed1993

Adhesion of staphylococci to chemically modified and native polymers, and the influence of preadsorbed fibronectin, vitronectin and fibrinogen.

A commercially available poly(ether urethane), polyethylene, and modifications of these polymers have been compared with respect to adsorption of fibronectin, fibrinogen and vitronectin. The adhesion of staphylococcal strains (characterized for ability to bind immobilized proteins, cell surface hydrophobicity and charge) was studied by bioluminescence with and without preadsorption of proteins to the surfaces. The least amount of proteins and the fewest bacteria adhered to the amphiphilic surfaces. When polymers were preincubated with plasma or albumin, lower numbers of bacteria adhered, except to Pellethane grafted with PEG 20,000, to which coagulase-negative staphylococci adhered to a higher extent.

Adsorption↗
PubMed1993

Binding of Escherichia coli to Penrose rubber drains--an in vitro study.

Ten different isolates of Escherichia coli were used to compare bacterial attachment to Penrose rubber drains at different temperatures and to investigate a possible relation with cell surface hydrophobicity and charges, as well as the capacity of autoaggregation. Penrose rubber drain pieces of 1 cm2 were incubated with 4.8 x 10(6) E. coli cells for 1 h at 22, 37 and 42 degrees C, respectively. After rinsing with phosphate buffered saline (PBS), the number of adhering bacteria on the drain pieces was calculated by measuring cellular ATP (adenosine triphosphate) bioluminescence. Bacterial cell surface properties at different temperatures were determined by two-phase partitioning and autoaggregation was determined by arbitrary scoring under the dissecting microscope. For most strains of E. coli, the number of adherence to Penrose rubber drain was higher at 22 degrees C than at 37 degrees C and 42 degrees C. Bacterial cell-surface properties and autoaggregation capacity were influenced by the growth temperature, but without correlation to bacterial ability to attach to rubber drains. Thus, the present study demonstrates that attachment of E. coli to Penrose rubber drains was significantly influenced by temperature, but bacterial cell-surface hydrophobicity and charge as well as autoaggregation capacity had no influence on bacterial attachment ability.

Bacterial Adhesion↗
PubMed1993

Isolation of a sialic acid-specific surface haemagglutinin of Helicobacter pylori strain NCTC 11637.

A deionized water extract of Helicobacter pylori NCTC 11637 contained haemagglutinin activity that was (i) soluble (i.e., not associated with particulate material sedimented by centrifugation at 100,000 x g for 1 h), (ii) stable to lyophilization, (iii) heat-labile, (iv) chymotrypsin-sensitive, (v) inhibited by fetuin, orosomucoid, and NANLac, but not by asialofetuin and (vi) inactive against guinea pig erythrocytes incubated with Clostridium perfringens neuraminidase, but active against untreated guinea pig erythrocytes. The data support the idea that the haemagglutinin is a protein which recognizes the alpha-(2-3) structure of sialylated glycoconjugates. Fractionation of the extract by isoelectric focusing and by gel filtration with Sephacryl S-400 indicated that the haemagglutinin has a pI of 3.7 and consist of high molecular-weight-protein aggregates. SDS-PAGE analysis of the preparation purified by gel filtration showed 3 protein bands at ca. 64 kD, 56 kD and 20 kD. Electron microscopy of H. pylori incubated with gold-labelled fetuin indicated that the haemagglutinin was associated with loosely adherent material on the bacterial surface, and that the purified haemagglutinin did not reveal a fimbrial structure. The ability to bind to sialoglycoconjugates on the erythrocyte membrane suggests that the haemagglutinin may be an important colonization factor enabling H. pylori to bind to similar saccharide structures on epithelial cells.

Animals↗
PubMed1993

The E test for antimicrobial susceptibility testing of Helicobacter pylori.

Antimicrobial susceptibility testing of Helicobacter pylori by conventional means (disc diffusion) is of questionable value because the bacterium grows so slowly. We have determined the susceptibilities of 20 isolates of H. pylori to ampicillin, erythromycin, gentamicin, metronidazole, rifampicin and tetracycline by the E test, a novel technique for measuring MICs, and compared the results with those determined by standard agar dilution and disc diffusion methods. Eighty-one per cent of E test-determined MICs were within one two-fold dilution and 93% were within two two-fold dilutions of those determined by the reference agar dilution method. MICs determined by the E test were highly reproducible; replicate results were invariably within one two-fold dilution. MICs were not affected by the size of the inoculum, preincubation or incubation times. Regression lines for disc diffusion could not be determined because of the lack of resistant strains. However, metronidazole-resistant strains (MIC > 32 mg/L) were easily distinguishable from susceptible strains (MIC < 1 mg/L). In conclusion, the E test is a reliable method for determining the antimicrobial susceptibility of H. pylori.

Anti-Bacterial Agents↗
PubMed1993

Serum and tissue protein binding and cell surface properties of Staphylococcus lugdunensis.

Eleven strains of Staphylococcus lugdunensis from different clinical sources were investigated for their ability to bind 125I-labelled collagen (Cn) type I and IV, fibronectin (Fn), vitronectin (Vn), laminin (Lm), fibrinogen (Fg), thrombospondin, plasminogen (glu- and lys-form) and human IgG. All the strains bound these proteins, although a higher degree of binding was obtained for Cn types I and IV and IgG with mean values of 36%, 32% and 26% binding, respectively. In tests with proteins immobilised on latex beads in a particle agglutination assay, eight of the 11 strains bound Cn type I and seven bound Fg, whereas no strain bound immobilised IgG. Binding to immobilised Cn-I, Fg, Lm and Vn was abolished when the bacterial cells were treated with proteases or heat, indicating cell-surface receptors with protein characteristics. Cell-surface extracts of S. lugdunensis 2342 were able to totally inhibit binding of the homologous strain and S. aureus Cowan 1 to latex-immobilised proteins Cn-I, Lm, Vn, Fn and Fg. The binding of 125I-labelled Cn IV by S. lugdunensis 2342, was heat sensitive, whereas the binding to S. aureus Cowan 1 was heat resistant. The strains gave negative results in tests for the presence of protein A with a S. aureus protein A gene probe and with sensitised red blood cells. No production of heat-stable nuclease (TNase) could be detected by monoclonal antibodies against TNase or by the polymerase chain reaction with an oligonucleotide sequence from S. aureus TNase as primer.(ABSTRACT TRUNCATED AT 250 WORDS)

Agglutination Tests↗
PubMed1993

High-affinity binding of laminin by Helicobacter pylori: evidence for a lectin-like interaction.

Laminin, the major glycoprotein of basement membranes, was shown to be bound by the human gastric pathogen Helicobacter pylori. Binding of 125I-laminin by strain 17874 was time-dependent, specific and saturable. Scatchard analysis of specific binding indicated about 2000 binding sites per cell with a dissociation constant of 8.5 pM. Treatment of the cells by heat (80 degrees) and with proteolytic enzymes drastically reduced laminin binding, suggesting that the laminin receptors are surface proteins. Some highly glycosylated glycoproteins inhibited laminin binding by 50%. Furthermore, N-acetylneuraminyllactose decreased laminin binding by 70% and neuraminidase treatment of laminin by 50%, while a recombinant B1 chain of laminin, containing high-mannose type oligosaccharides, inhibited binding by only 25%. This suggests that terminal sialic acids on laminin compete for a specific sugar binding protein(s) on H. pylori cells.

Bacterial Adhesion↗
PubMed1993

Reduction of E. coli adherence to rubber slices treated with phospholipids.

The present study aimed at modifying the surface of biliary drain material to reduce bacterial adherence. The adherence of cells of seven E. coli strains to rubber slices treated with phosphatidylcholin (PC) or phosphatidylinositol (PI) and the adherence of cells of E. coli strain NG7C to PC- or PI-treated rubber slices implanted in the common bile duct in rats were studied in vitro. The rubber slices were incubated with 1 x 10(7) cfu radiolabeled E. coli cells/ml at 37 degrees C for 60 min and then drained and washed thrice in 2 ml PBS, and adherent E. coli cells were quantified by radioactivity counting. The results show that both PC and PI absorbed on the surface of slices reduced the adherence of E. coli cells in at least two ways, i.e. by changing surface properties in vitro and by reducing deposition of host-derived molecules on phospholipid-treated surfaces in vivo. The results may be of use for modification of the biomaterial surface in the clinical situation.

Animals↗
PubMed1993

Rapid detection and characterization of sialic acid-specific lectins of Helicobacter pylori.

A particle agglutination assay (PAA) using fetuin (Ft) covalently coupled to carboxylate-modified latex (CML) particles was evaluated for rapid detection of sialic acid-specific haemagglutinins/lectins (SALs) of Helicobacter pylori isolates which bind sialoglycoconjugates. Sixty-three percent (20/32) of the isolates examined gave a positive PAA test. Cell-bound SALs were extracted by washing the bacteria with deionized water or isotonic saline, and their expression was influenced by pH and culture conditions. The Ft-CML reactivity of the PAA-positive isolates was inhibited by bovine submaxillary mucin, transferrin, fetuin, orosomucoid, vitronectin and lactoferrin in a manner which suggested that the isolates contain a lectin recognizing the alpha(2-6) linkage of terminal sialic acid. Western blots of strain NCTC 11637 SALs probed with horseradish peroxidase (HRP)-labelled Ft identified three bands (MW 64 kD, 62 kD, 56 kD) which also reacted with HRP-labelled mucin, transferrin, lactoferrin, orosomucoid, vitronectin and laminin. Sera from patients with a H. pylori infection and one polyclonal rabbit antiserum (strain NCTC 11637) also reacted with the SALs. Immunogold labelling of a polyclonal rabbit antiserum raised against the 64 kD protein of strain NCTC 11637 that reacted strongly with Ft-CML showed that abundant SALs were loosely cell-associated with the cell surface of both spiral and coccoidal forms of H. pylori. SALs were also present in low amounts on the surface of strain NCTC 11638 and 66, a clinical isolate that did not react with Ft-CML.

Animals↗
PubMed1993

Enteric bacterial translocation after intraperitoneal implantation of rubber drain pieces.

To study the kinetics and mechanisms of bacterial translocation from the gut after intraperitoneal (IP) implantation of prosthetic materials, different sizes of rubber drain pieces were intraperitoneally implanted in the rat, followed by evaluation of ileal mucosal permeability after 2 days and of the occurrence of bacterial translocation and gut oxygen extraction at various time points. Enteric bacteria translocated to mesenteric lymph nodes and disseminated to systemic organs (liver, spleen, lungs, and kidneys), the portal vein, and inferior vena cava 2, 4, and 6 h after IP implantation of rubber drain pieces with 10-, 7-, and 3-cm2 areas, respectively, and subsequently to the IP rubber drain piece and the peritoneal cavity on the 2nd postoperative day. The incidence of translocation correlated with the size of the implanted material and time after implantation. The gut oxygen extraction increased significantly after IP implantation of 7- and 10-cm2 rubber drain pieces. The ileal mucosal permeability was enhanced in the groups implanted with 7- and 10-cm2 drain pieces. Thus, bacterial translocation occurs already in the early period after IP implantation of rubber drain and increased with time. The increased gut oxygen extraction implies that the gut is susceptible to IP inflammatory stimulation, and the enhanced ileal permeability suggests that the integrity of the gastrointestinal tract is compromised, which might facilitate bacterial translocation.

Animals↗