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Biomedical subjects

B Wretlind

Publications and source records attributed to B Wretlind.

At least 109 records · Page 6Linked to original sources
PubMed1981

The role of proteases and exotoxin A in the pathogenicity of Pseudomonas aeruginosa infections.

Most Pseudomonas aeruginosa strains produce exotoxin A and two extracellular proteases (elastase and alkaline protease). Exotoxin A is a lethal toxin that inhibits protein synthesis in mammalian cells by the same mechanism as diphtheria toxin. It is generated in clinical and experimental animal infections. Passive or active immunization against this toxin gives significant protection against experimental infections with exotoxin-producing strains. The proteases have tissue-damaging activity and are capable of degrading various plasma proteins such as complement and coagulation factors. Proteases probably play a part in localized pseudomonas infections such as keratitis, pneumonia and burn infection. When invasion and colonization have occurred and septicemia is established, these enzymes probably are less important.

ADP Ribose Transferases↗
PubMed1979

Assessment of protease (elastase) as a Pseudomonas aeruginosa virulence factor in experimental mouse burn infection.

The data presented indicate that in experimental Pseudomonas aeruginosa infection of mice, protease enhances the virulence of the organism. Anesthetized CBA/Lü mice were subjected to a 15-s flame burn and infected with a wild-type protease-producing strain and two of its protease-deficient mutants. The average bacterial cell mean lethal dose (LD50) of 3.8 +/- 0.3 standard deviation (log10) for mice infected with the protease-producing P. aeruginosa was at least 1 log lower than the LD50 of the protease-deficient mutants (0.02 greater than P greater than 0.01). The addition of purified protease to the infecting inoculum of protease-deficient strains reduced the LD50. Although the generation time in vitro was the same for all three bacterial strains used, there were consistently fewer viable bacteria in the blood of mice infected with protease-deficient strains than in those infected with the protease-producing strain. When a protease-deficient strain was mixed with the protease-producing wild-type strain, the number of protease-producing pseudomonas found in the blood remained constant, whereas the number of protease-deficient organisms increased, suggesting that protease contributed to the invasiveness of the organisms. The survival of mice infected with protease-producing pseudomonas was enhanced by antiprotease serum. Antiprotease serum had no effect in mice infected with protease-deficient mutants.

Animals↗
PubMed1978

Experimental infections with protease-deficient mutants of Pseudomonas aeruginosa in mice.

The virulence of a protease-producing strain of Psuedomonas aeruginosa was compared with that of mutants that had lost the ability to produce proteases and other extracellular enzymes. Lethal infections were produced by inoculating mice intraperitoneally with bacteria in mucin, or by inoculating mice intraperitoneally or intravenously with bacteria 4 days after treatment with cyclophosphamide, 200 mg per kg body weight. No significant difference in virulence between the wild-type parent strain and some of its protease-deficient mutants was found. Histopatholoical examination of different organs in the cyclophosphamide-treated and infected mice showed striking fatty infiltration and focal necrosis of liver, multiple necrotic foci in the spleen and haemorrhagic cystitis with necorsis. The cystitis was produced by cyclophosphamide alone but was aggravated by the infection. In conclusion, no correlation between the production of protease in broth culture and the ability to produce lethal septicaemia in mice was found, and extracellular proteases probably didnot contribute to the virulence of P. aeruginosa. However, the histopathological changes in the liver suggested a role for exotoxin A insystemic infections.

Animals↗
PubMed1977

Evaluation of two test-kits--API and Oxi Ferm tube--for identification of oxidative-fermentative Gram-negative rods.

Two test-kits--API and Oxi Ferm tube--have been compared for accuracy in individual tests and for identification on the genus or species level with conventional biochemical tests on 154 oxidative-fermentative gram-negative rods. The two test systems were found to be reliable and permit identification of the clinically most significant oxidative-fermentative strains.

Bacteriological Techniques↗
PubMed1977

Purification and properties of a protease with elastase activity from Pseudomonas aeruginosa.

The isoelectric points of three proteases (I, II and III), separated from culture supernatants of Pseudomonas aeruginosa strain PAKS-I by isoelectric focusing, were 8.5, 6.6 and 4.5 respectively. Collagenase activity was not detected. More than 75% of the extracellular protease activity of this strain was due to protease II. This enzyme also possessed elastase activity. When purified by ammonium sulphate precipitation, isoelectric focusing and gel chromatography, protease II showed one band on disc electrophoresis and one band on conventional immunoelectrophoresis. The pH optimum, stability and effect of inhibitors and substrate concentration were examined. The molecular weight was 23000 +/- 5000. Protease II was lethal for mice when injected intraperitoneally at a high dose (minimum lethal dose 0.1 mg). Dermonecrosis and subcutaneous haemorrhages were produced in new-born mice upon subcutaneous injection of 10 microgram protease II. A sensitive test for cytotoxicity showed no evidence of cytoplasmic membrane damage to HeLa cells or human diploid embryonic lung fibroblasts by protease II. Morphological changes similar to those produced by trypsin were found.

Animals↗
PubMed1977

Protease-deficient mutants of Pseudomonas aeruginosa: pleiotropic changes in activity of other extracellular enzymes.

Mutants of Pseudomonas aeruginosa strain PAKS-I which are defective in the formation of extracellular protease activity have been characterized. The mutants produced between approximately 1 and 25% of the protease activity of the wild type and no strains completely lacking extracellular protease were found, even after repeated mutagen treatment. Most mutants also had changed activities of extracellular staphylolytic enzyme, lipase and lecithinase. Four of 13 mutants were unable to release alkaline phosphatase and staphylolytic enzyme into the medium in contrast to the wild type. Serotype, phage type and biochemical reactions were essentially unchanged. The results indicate that some of the mutations affected the cell envelope structure of function leading to decreased ability to release extracellular proteins, and that other mutations possibly affected a common regulatory mechanism for extracellular enzymes.

Alkaline Phosphatase↗
PubMed1975

Extracellular proteins in five clostridial species from human infections.

347 strains from human infections were identified by gas-liquid chromatography of metabolic products and by conventional tests. Simple agar-plate assays were used to analyze the ability to form extracellular proteins. More than 90% of all strains were hemolytic on agar containing rabbit erythrocytes and all were gelatinase producers. All strains of C. bifermantans, C. sordelli, and C. sporogenes were also caseinolytic on skimmed-milk agar, but strains of C. perfringens, C. novyi types A and B were not. Less than 10% of C. perfringens strains were producers of elastase and staphylolytic enzyme and all other species were non-producers. All C. perfringens, C. novyii, C. bifermentans, and C. sordelli were lecithinase producers, but C. sporogenes was not. All strains of C. sporogenes formed deoxyribonuclease, while a varying number of the other species showed a positive reaction.

Bacterial Proteins↗
PubMed1975

Characterization of three Aeromonas and nine pseudomonas species by extracellular enzymes and haemolysins.

Strains from type culture collections and clinical isolates belonging to the Aeromonas and Pseudomonas genera were identified with conventional tests. Production of extra-cellular enzymes and haemolysins were detected by simple plate agar methods. The following enzymes were found to be of special value for a rapid and simple classification of certain species in both genera: potease (casein and gelatin agar), lecithinase (lecithin agar), and deoxyribonuclease (DNA agar). Elastase, staphylolytic enzyme, lipase, ribonuclease, amylase, and egg yolk reaction were other enzymes studied. However, these tests were not positive for more than 90% of any species. A. hydrophila, A. salmonicida, and P. aeruginosa were haemolytic on agar containing rabbit erythrocytes.

Aeromonas↗
PubMed1975

Antibiotic sensitivity of two Aeromonas and nine Pseudomonas species.

An agar dilution method was used to determine the in vitro sensitivity of different Pseudomonas and Aeromonas species to sulphonamide, tetracycline, colistin, gentamicin, tobramycin, amplicillin, carbenicillin, and cephalothin. P. aeruginosa was generally sensitive to carbenicillin, colistin, tobramycin, and gentamicin. P. putida and P. fluorescens were generally resistant to beta-lactam antibodies but sensitive to gentamicin and tobramycin. P. cepacia and P. maltophilia were mostly resistant to colistin, gentamicin and tobramycin. Other Pseudomonas species were usually more sensitive to the antibodies tested. Strains of Aeromonas hydrophila were mostly resistant to beta-lactam antibiotics but sensitive to other antibiotics, while strains of A. shigelloides were very sensitive to all antibiotics tested.

Aeromonas↗
PubMed1975

Antibiotic concentrations in maxillary sinus secretions and in the sinus mucosa.

In maxillary sinusitis, the blood circulation is supposed to be impaired in the oedematous sinus mucosa, and in such cases the transport of antibiotics into the maxillary sinus should be reduced. To prove the accuracy of this assumption a comparison has been made between the concentrations of penicillin and doxycycline (Vibramycin, Pfizer) in sinus mucosa and secretions and the serum concentrations in patients under treatment with these antibiotics. Measureable concentrations of penicillin (greater than 0.2 mug/ml) were reached in the secretions only if the serum concentration was high (greater than 4-5 mug/ml). In contrast, measurable concentrations of doxycycline were achieved in both mucosa and secretions in all patients treated with this antibiotic. This must depend on the fact that doxycycline, due to its optimal lipid solubility, was able to penetrate poorly vascularized tissue. In most cases, the concentrations of doxycycline far exceeded the minimum inhibitory concentrations of the isolated organisms, and in some cases the local concentrations were higher than those found in the serum. The clinical response to doxycycline was good and correlated well to the laboratory data.

Doxycycline↗
PubMed1975

Evaluation of the antibiotic effect of treatment of maxillary sinusitis.

As the effect of antibiotic treatment of maxillary sinusitis has been questioned, the elimination of bacteria from sinus secretions was studied during antibiotic treatment. Penicillin V, azidocillin, tetracycline or doxycycline was administered to 54 patients with maxillary sinusitis. Samples of sinus secretion were aspirated both before treatment and 2-3 days after the onset of treatment. When the antibiotic concentration was below the upper limit of MIC for sensitivity group 1, bacterial growth was present in practically all samples. When the antibiotic concentration equalled or was above this limit, there was no bacterial growth in about half of the samples. A prerequisite for antibiotic effect--elimination of bacteria--is that the antibiotic concentration is well above the MIC of the bacteria at the site of infection. The choice between bactericidal or bacteriostatic antibiotics appeared unimportant. Bacterial survival in the maxillary sinus despite a high antibiotic concentration in the sinus illustrates that MIC values determined in the laboratory do not always mirror the sensitivity of bacteria to antibiotics in vivo.

Anti-Bacterial Agents↗
PubMed1971

Separation of two hemolysins from Aeromonas hydrophila by isoelectric focusing.

Two hemolytic proteins (hemolysin I and II) with isoelectric points of 5.5 and 4.3 were purified by isoelectric focusing from the culture supernatant fluid of Aeromonas hydrophila. The purified hemolysins were unstable after dialysis and upon heating at 37 C and were inactivated by proteolytic enzymes. The two hemolysins were lethal for mice in a dose of 10 mug (hemolysin I) and 3 mug (hemolysin II) and showed similar hemolytic spectra on red cells of different species. Both were also cytotoxic for HeLa cells and human fibroblasts and gave dermonecrosis in rabbits.

Aeromonas↗