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Biomedical subjects

G Kronvall

Publications and source records attributed to G Kronvall.

At least 73 records · Page 4Linked to original sources
PubMed1988

Non-immune Fab- and Fc- mediated interactions of avian Ig with S. aureus and group C and G streptococci.

Serum samples from 19 avian species representing 8 orders were tested for their capacity to inhibit the Fab- and Fc-mediated immunoglobulin binding to protein A-carrying S. aureus and protein G-carrying group C and G streptococci. Four species (mallard, dunlin, starling and blackbird) belonging to three different orders showed a high degree of Fc-mediated protein A- and protein G-reactivity. Five species demonstrated a high level and nine species exhibited a low level of Fab-mediated protein A-reactivity. The four species identified as Fc-reactive were capable of Fab-mediated immunoglobulin binding with streptococcal surface proteins but incapable of Fab-mediated protein A binding. SDS-PAGE analysis confirmed that the protein A-Sepharose affinity purified material contained proteins corresponding to immunoglobulin chains. Inhibition results by avian sera were confirmed by direct binding of protein A-reactive proteins to bacteria, by precipitation in gel and by Western blot analysis of binding to protein A and protein G, respectively.

Animals↗
PubMed1988

Laboratory- and species-specific interpretive breakpoints for disk diffusion tests of chloramphenicol susceptibility of Haemophilus influenzae.

A total of 601 clinical isolates of Haemophilus influenzae isolated in six different regions of Sweden were tested for chloramphenicol susceptibility by using agar dilution MIC determinations and disk diffusion tests. For seven strains MICs were 4 micrograms/ml or higher, and for one strain the MIC was 2 micrograms/ml. All eight strains produced chloramphenicol acetyltransferase. For the remaining 593 strains, MICs were less than or equal to 1 microgram/ml, and the MICs for 50% and 90% of the strains were both 0.5 microgram/ml. Disk diffusion tests carried out by using revised interpretive criteria introduced in 1984 by the Swedish Reference Group for Antibiotics correctly identified the 593 strains as susceptible and the 8 strains as resistant. Quality assessments were performed in 29 clinical microbiology laboratories. The revised criteria for chloramphenicol disk diffusion testing gave rise to false resistance results in some laboratories. The interpretive accuracy improved when the interlaboratory variation was compensated for by using adjusted breakpoints. Such revision was possible through peak correction, single-strain regression analysis, and standard curve regression analysis. Peak-corrected breakpoints improved the accuracy from an overall incidence of false-resistant isolates of 4.4% to 2.3%. Single-strain regression analysis and standard curve regression analysis provided laboratory- and species-specific breakpoints which reduced false resistance rates of 0.14% and 0%, respectively.

Chloramphenicol↗
PubMed1988

Bacteriology of maxillary sinusitis in relation to character of inflammation and prior treatment.

By antral aspiration, 200 sinus secretions were obtained from the same number of adult patients with maxillary sinusitis. The bacteriological findings were related to the character of the secretions as well as to the duration of symptoms, previous antibacterial treatment and possible dental genesis. Pathogens were isolated in 87% of 54 patients with untreated acute sinus empyema, Streptococcus pneumoniae being the most prevalent (57%). In 47 cases of treatment failure Haemophilus influenzae predominated and was found in 60% of the purulent secretions. In all, 11% of the 47 cases showed growth of beta-lactamase-producing H. influenzae, corresponding to 18% of all H. influenzae in this group. Staphylococcus aureus and anaerobic bacteria were infrequent findings except in purulent sinus secretion from patients with a long history. In contrast to patients with sinus empyema, no pathogens were found in the majority of 37 patients with non-purulent sinusitis.

Adolescent↗
PubMed1988

Susceptibility to beta-lactam antibiotics and gentamicin of gram-negative bacilli isolated from hospitalized patients: a Swedish multicenter study.

A total of 952 blood and 1543 urine isolates of gram-negative bacilli from hospitalized patients in 1986-1987 were consecutively collected by 10 Swedish laboratories and tested for susceptibility to 8 beta-lactam antibiotics and to gentamicin. The isolates were mostly Escherichia coli (58% and 44%, respectively) and Klebsiella sp. (17% and 18%). Resistance to ampicillin in blood and urine isolates was found in 35% and 45%, respectively, to piperacillin in 5% and 6%, to cephalothin in 26% and 34%, to cefuroxime in 12% and 22%, to cefotaxime in 3% and 5%, to ceftazidime in 1% and 1%, to imipenem in 0.5% and 0.1%, to aztreonam in 3% and 2%, and to gentamicin in 0.8% and 0%. Resistance of clinically important gram-negative bacilli to new beta-lactam antibiotics and to gentamicin is infrequent in Sweden.

Ampicillin↗
PubMed1988

On the theory of the disk diffusion test. Evidence for a non-linear relationship between critical concentration and MIC, and its practical implications for susceptibility testing of Haemophilus influenzae.

The procedure for disk diffusion susceptibility testing has been worked out for rapidly growing non-fastidious bacteria. Using the general zone diameter breakpoints for interpretation of susceptibility, it was found that clinical isolates of H. influenzae were assigned to the wrong SIR category in fifty per cent of the strains for erythromycin, and ten per cent for doxycycline. New species- and laboratory-specific interpretive zone diameter breakpoints corresponding to the recommended MIC limits were therefore worked out. The Standard Curve regression Analysis (SCA) method used for this purpose is based on the correlation between zone size and disk content, using two reference strains with different MICs. In its original version (the Single strain Regression Analysis, SRA) only one reference strain was used. This equation was found not to be generally valid since the relationship between MIC and the critical concentration is not constant, as was originally assumed. The slope and intercept of the regression line obtained by SCA is species related, while a general regression line based on results from many different species assumes that there is the same relation between the zone size and MIC for all species. Breakpoints for erythromycin and doxycycline calculated by the SCA equation gave more accurate results in routine susceptibility testing of H. influenzae and reduced the error rate from fifty three and ten per cent to four and three per cent for the two antibiotics.

Doxycycline↗
PubMed1987

Isolation of a specific albumin receptor from a group G streptococcal strain.

The albumin receptor, a bacterial cell-wall protein with affinity for albumin, has been isolated from a bovine group G streptococcal strain (DG-8). Bacterial surface proteins were solubilized by boiling in 0.6M HCl for 5 min. The albumin receptor was isolated by sequential use of ion-exchange chromatography on DEAE-Sephadex A-50 and affinity chromatography on albumin coupled Sepharose 4B. The presence of albumin receptor in various pools and fractions during the isolation was followed by their ability to inhibit the binding of radiolabelled albumin to DG-8 bacteria. A highly purified albumin receptor was obtained according to Western blot analysis. The albumin binding band obtained showed a molecular weight of about 30,000. The purified receptor did not possess any IgG binding capacity. 50 micrograms albumin receptor was prepared from each gram of bacteria.

Bacterial Proteins↗
PubMed1987

The bacteriology of nosocomial infections at Tikur Anbessa Teaching Hospital, Addis Ababa.

Patients admitted to a teaching hospital in Addis Ababa were studied for nosocomial infection. Of 2506 patients, 13% developed clinical infections, with the highest rate among obstetric/gynaecologic patients (17.0%). Wound infection was the most frequent type of nosocomial infection (49%) followed by urinary tract infection (25%). Antibiotic prophylaxis was given to 43% of the patients. Gram-negative bacteria comprised 88% of all isolated strains Enterobacteriaceae; 75% of all isolates were found in over 60% of the infection, Proteus 25%, Escherichia coli 20% and Klebsiella 19%. The most widely used antibiotics were ineffective against 65 to 85% of the Gram-negative strains. Cefotaxime and gentamicin were more effective. Staphylococcus aureus isolates were also similarly resistant, against which cephalothin, lincomycin and gentamicin were the more effective ones. Over 70% of the strains were multiple resistant. The findings underscore the need for a surveillance program and infection control system to reduce the high rate of infection and to institute appropriate guidelines for the use of prophylactic and therapeutic antibiotics.

Anti-Bacterial Agents↗
PubMed1987

Increased use of erythromycin causes resistance in Haemophilus influenzae.

The use of erythromycin in Sweden has increased since 1975. An increasing prevalence of Haemophilus influenzae (H.i.) with reduced susceptibility to erythromycin has been noted in our laboratory during the years 1980 to 1985. The largest consumers of erythromycin were found to be children less than 4 years of age. Variations in resistance level of H.i. isolated from patients within this age group and variations in consumption of erythromycin were analysed for each year. The highest prevalence of resistant strains was found during spring and summer. The consumption of the antibiotic was highest during the first quarter of the year, gradually decreasing, and increasing sharply again during the fourth quarter of the year. Judging also from deviations from this pattern there seems to be an association between consumption and resistance. The different levels of resistance reported in the literature may reflect different populations of patients with different consumption of erythromycin, and different levels at different time of the year. Considering the present high level of H.i. with decreased susceptibility to erythromycin the drug is not likely to have clinical effect in H.i. infections.

Child, Preschool↗
PubMed1986

Two separate non-immune interactions between staphylococcal protein A and immunoglobulins are mediated by structures on gamma chains.

The present investigation was undertaken to determine whether the light or the heavy immunoglobulin chain is involved in the alternative, non-immune F(ab')2-mediated binding to staphylococcal protein A. Purified human polyclonal IgG was mildly reduced with dithiothreitol and alkylated with iodoacetamide. Intact IgG, purified light and heavy chains of polyclonal immunoglobulin G were tested in an inhibition assay for alternative non-immune F(ab')2-mediated binding to the protein A-carrying S. aureus, strain Cowan I. The IgG Fc-mediated binding to protein A was studied in parallel inhibition experiments. Heavy chains inhibited both the alternative F(ab')2- and the classical Fc-mediated binding to protein A. Isolated light chains were non-reactive. Intact IgG molecules were more potent inhibitors than isolated heavy chains tested in equimolar concentrations. Our results indicate that the alternative non-immune interaction between staphylococcal protein A and human immunoglobulins is mediated by structures expressed on the heavy immunoglobulin G chain. Thus, there are two separate protein A binding sites on gamma chains.

Immunoglobulin Fab Fragments↗
PubMed1986

Non-immune F(ab')2- and Fc-mediated interactions of mammalian immunoglobulins with S. aureus and group C and G streptococci.

The distribution among mammalian species of non-immune F(ab')2- and Fc-mediated immunoglobulin interactions with surface proteins of S. aureus (protein A) and of group C and G streptococci was studied. Serum samples from 48 mammalian species representing 15 orders were first tested for their capacity to inhibit streptococcal F(ab')2-mediated binding; 26 of these sera were also tested for streptococcal IgG Fc-mediated binding. Analogous inhibition experiments were then carried out with staphylococci. All mammalian species studied inhibited both types of immunoglobulin binding to streptococci, viz the serum samples contained both F(ab')2- and Fc-reactive immunoglobulins. The reactivity was equal to that of human serum in 26 out of 47 mammalian sera. Seven sera showed a low degree of inhibition compared to human serum. The inhibiting capacities of the two streptococcal non-immune interactions showed a direct correlation (r = 0.91, p less than 0.0001 for the r-value) for individual species. The inhibition patterns observed with S. aureus differed from the profiles recorded with the streptococcal strains, suggesting that these organisms interact with separate sites on the immunoglobulin molecules. Isolated F(ab')2-binding was recorded in 5 out of 24 sera, and Fc-binding alone was noted in 7 sera. Taken together, the present studies demonstrate that mammalian immunoglobulins possess F(ab')2- and Fc-binding sites for protein A and for receptors on group C and G streptococci. The F(ab')2-mediated binding to streptococci is associated with Fc-reactivity, in contrast to protein A which may interact exclusively with a complementary structure in either the F(ab')2- or the Fc-portion of the immunoglobulins.

Animals↗
PubMed1985

Non-immune IgG F(ab')2 binding to group C and G streptococci is mediated by structures on gamma chains.

The present investigation was designed to determine whether the heavy or the light immunoglobulin chain is involved in the non-immune binding of IgG F(ab')2 fragments to specific surface receptors on human group C and G streptococci. Purified human polyclonal IgG was mildly reduced with dithiothreitol and alkylated with iodoacetamide. Light (L) and heavy (H) chains were separated. Intact IgG and purified L and H chains of polyclonal immunoglobulin G were tested in an inhibition assay for non-immune IgG F(ab')2-mediated binding to group C and G streptococci. H chains inhibited the uptake of isotope-labelled IgG F(ab')2 fragments. Isolated L chains were non-reactive. Intact IgG molecules were more potent inhibitors than isolated H chains tested in equimolar concentrations. These results indicate that the non-immune interaction between human group C and G streptococci and F(ab')2 fragments of human IgG is mediated by reactive sites exposed on the immunoglobulin G H chains. The observation that intact IgG on a molar basis was more inhibitory than purified gamma chains suggests that the L chains may contribute to the reactivity, presumably by passive stabilization of the immunoglobulin molecule.

Antibodies, Bacterial↗
PubMed1985

Determination of species- and laboratory-related interpretive breakpoints for doxycycline susceptibility testing using single-strain regression analysis.

Single-strain Regression Analysis (SRA) was performed for doxycycline on a total of 68 bacterial strains representing 16 different species. Species- and laboratory-related zone diameter breakpoints were determined and compared with histograms of zone diameter values obtained from 942 routine susceptibility tests. Calculated breakpoints were similar within individual species. When considering the homogeneity of susceptibility groups within bacterial species, the calculated breakpoints gave rise to relatively few interpretive errors. In contrast, general breakpoints for doxycycline as recommended by the Swedish Reference Group (SRG) (R less than = 20 mm and S greater than = 26 mm) would give rise to a high proportion of false interpretations in the present laboratory. Fifty-three per cent of H.influenzae strains would have been assigned to the wrong susceptibility group. For E.coli and K.pneumoniae, 22 and 35 per cent, respectively, would have been erroneously categorized using SRG breakpoints. E.cloacae and E.aerogenes would have been assigned another category in 39 and 50 per cent, respectively. The procedure for setting species-specific and laboratory-related interpretive breakpoints is described. Determination of species- and laboratory-related interpretive breakpoints using SRA provides a new approach towards improved accuracy of disc-diffusion susceptibility testing.

Doxycycline↗
PubMed1985

Variations in binding of mammalian fibrinogens to streptococci groups A, B, C, E, G and to Staphylococcus aureus.

Twenty-eight beta-hemolytic streptococci of groups A, B, E, G and Streptococcus equisimilis as well as four Staphylococcus aureus strains were tested for their ability to bind fibrinogen preparations from different animal species: homo, baboon, rabbit, rat, guinea-pig, dog, horse, pig, cow and sheep. The patterns of binding indicated differences in the structures of the bacterial fibrinogen receptors. There were higher binding levels in streptococci groups A, G, and S. equisimilis than in representative group B and E strains. Considerable differences in the binding capacity were found within streptococci groups A and E. Group C and group G strains showed rather similar patterns and could be further divided into high-level and low-level binding strains. There is no correlation between binding levels of different animal fibrinogen preparations and the strains isolated from corresponding animals. Recent studies by others have shown that resistance to phagocytosis is mediated by fibrinogen-binding in streptococci group A. The existence of similar fibrinogen-binding structures in several streptococcal species indicates an important role with a definite survival value. It also suggests that M or T protein analogues are present in streptococci groups C, G and E.

Animals↗
PubMed1985

Determination of interpretive breakpoints for ceftazidime disc-diffusion susceptibility testing using single-strain regression analysis.

Interpretive breakpoints for ceftazidime disc-diffusion susceptibility testing were determined using single-strain regression analysis (SRA). Regression lines were determined for a total of 58 strains representing 15 species, from inhibition zone diameters obtained for discs containing six different ceftazidime concentrations. Statistical analysis for excluding non-linearity of test-results was performed. A minimum of five tests on consecutive days was required for maximal precision of regression analysis according to the SRA-method. Calculated regression lines showed similarities within individual and groups of bacterial species. A minimum of five strains could be used to represent these groups. Interpretive breakpoints according to recommended MIC-limits were determined for each species taking into consideration confidence limits for zone correlates of MIC-values. Single-strain regression analysis for the determination of interpretive breakpoints for ceftazidime disc-diffusion susceptibility testing in individual laboratories.

Ceftazidime↗
PubMed1985

Serological assays against Staphylococcus aureus peptidoglycan, crude staphylococcal antigen and staphylolysin in the diagnosis of serious S. aureus infections.

Immunoglobulin G antibody levels against Staphylococcus aureus peptidoglycan (PG) and crude staphylococcal antigen (SA) using enzyme-linked immunosorbent assay (ELISA) and antistaphylolysin (ASTA) antibody levels by gel diffusion were determined in 53 patients with S. aureus and 54 patients with non-S. aureus endocarditis and septicemia as compared with 63 febrile control patients. The two ELISAs were the most sensitive assays indicating S. aureus endocarditis in 83% and 88% in the PG- and SA-assays, respectively. 39% of non-S. aureus endocarditis patients were positive in the PG-assay due to antibodies cross-reacting with streptococci. A 100% specificity for S. aureus infections was obtained with the ASTA test, but this assay was less sensitive. A significant rise in anti-PG or anti-SA antibody levels was not only seen among S. aureus infections but also in some streptococcal and S. epidermidis infections as well as in 3 febrile control patients. When at least 2 of the 3 assays showed positive peak antibody levels 1-4 weeks after onset of infection together with a significant rise of both anti-PG and anti-SA antibody levels the S. aureus endocarditis diagnosis was highly suggestive. Thus, we recommend the combined use of these 3 assays using paired serum samples in diagnosing serious S. aureus infections.

Adolescent↗
PubMed1984

On the interaction between beta 2-microglobulin and group A streptococci.

beta 2-microglobulin (beta 2m) was found to interact with many group A streptococcal strains. The interaction appeared to require multipoint attachment, since monomeric beta 2m in solution showed no binding, whereas both beta 2m monomers bound to liposomes, and beta 2m in aggregates showed affinity for the bacteria. Aggregated HLA antigens (-A, -B and -C) and aggregated beta 2m exhibited the same binding patterns when tested in binding experiments with various group A streptococcal strains. Furthermore, beta 2m aggregates in excess completely blocked the binding of aggregated HLA antigens, thereby demonstrating that beta 2m is able to interact with streptococcal surface structures also when it is part of the HLA antigen complex. M protein-positive group A streptococcal strains bound significantly more beta 2m than M protein-negative variants of these strains. Purified M 12 protein partly inhibited the binding of radiolabelled beta 2m aggregates to whole streptococci, and in gel filtration and affinity chromatography experiments, the M 12 protein interacted with beta 2m. These various data suggest that the interaction between beta 2m and group A streptococci could be mediated by M protein. Lipoteichoic acid (LTA) is a constituent of the streptococcal cell wall that has been reported to form complexes with M protein at the bacterial cell surface. However, LTA did not influence the interaction between beta 2m and streptococci, suggesting that the binding of beta 2m to streptococcal M protein represents a pure protein-protein interaction. In vivo such an interaction could be established between infecting streptococci and host cells. Among 45 strains of different M types large differences in beta 2m binding were recorded, whereas among 60 strains of the classical nephritogenic M types 12 and 49, all were highly beta 2m-reactive, which points towards a role for beta 2m in streptococcal pathogenicity.

Bacterial Proteins↗
PubMed1984

Single-strain regression analysis for quality control of cephalothin-susceptibility testing and determination of interpretive breakpoints.

Histogram analysis of inhibition zone diameters around the 30 micrograms cephalothin disk for E. coli, P. mirabilis, and K. pneumoniae in samples from 1975 to 1982 showed a marked reproducibility of the disk-diffusion antibiotic-susceptibility test in the routine laboratory. A comparison of interpretive breakpoints with histograms for E. coli, P. mirabilis, K. pneumoniae, S. aureus, coagulase-negative staphylococci, and S. faecalis showed a higher proportion of possible misinterpretations using the breakpoints of the Swedish Reference Group, SRG, as compared to international (NCCLS) breakpoints. Further analysis using single-strain regression analysis revealed two major causes of interpretive errors. Firstly, the laboratory-related regression line for a bacterial species can be different from the general regression line of the reference laboratory. This difference has to be corrected by using species-related breakpoints. For E. coli, a species-specific breakpoint was determined to R = greater than 13 mm. Secondly, MIC limits recommended for the susceptibility categories of cephalothin by SRG are lower than the international limits and close to the true MIC values of many bacterial isolates, leading to misinterpretations due to the methodological variation. These studies suggest an adoption of international MIC limits for the susceptibility categories of cephalothin in Scandinavia. The "I" category should denote an indeterminate zone. A multi-laboratory quality control assessment using histogram analysis is recommended with optional single-strain regression analysis to determine breakpoints for problem combinations of bacterial species and antibiotics.

Bacteria↗