Biomedical subjects

G Kronvall

Publications and source records attributed to G Kronvall.

At least 19 recordsLinked to original sources

PubMed1992

A one-year study of streptococcal infections and their complications among Ethiopian children.

Post-streptococcal complications are known to be common among Ethiopian children. Little is known, however, about the epidemiology of beta-haemolytic streptococci in Ethiopia. A total of 816 children were studied during a one-year period: 24 cases of acute rheumatic fever (ARF), 44 chronic rheumatic heart disease (CRHD), 44 acute post streptococcal glomerulonephritis (APSGN), 143 tonsillitis, 55 impetigo, and 506 were apparently healthy children. Both ARF and APSGN occurred throughout the year with two peaks during the rainy and cold seasons. The female:male ratio among ARF patients was 1.4:1 and 1:1.9 among APSGN. The monthly carrier rate of beta-haemolytic streptococci group A varied from 7.5-39%, average being 17%. T type 2 was the most frequent serotype. Marked seasonal fluctuations were noted in the distribution of serogroups among apparently healthy children. Beta-haemolytic streptococci group A dominated during the hot and humid months of February-May. Strains were susceptible to commonly used antibiotics, except for tetracycline.

Carrier State↗

PubMed1992

Binding of plasminogen to Neisseria meningitidis and Neisseria gonorrhoeae and formation of surface-associated plasmin.

Forty-two strains of Neisseria meningitidis and 17 of Neisseria gonorrhoeae were tested for their ability to interact with 125I-labeled Glu-plasminogen. All strains tested reacted substantially with plasminogen, resulting in uptake values of 20%-48%. Scatchard analysis with selected N. meningitidis strains demonstrated a dual-phase receptor interaction, one more avid receptor with a Kd of 50 nM and 3000-6000 receptors per bacterium and a second receptor with a Kd of 200 nM and 10,000-20,000 receptors per bacterium. Plasminogen uptake could be completely eliminated by low concentrations of epsilon-aminocaproic acid, suggesting that the lysine binding sites on the plasminogen molecule are involved in the receptor-ligand interaction. The binding of plasminogen to the bacterial receptor facilitates the tissue-type plasminogen activator-mediated conversion to Glu-plasmin, which also modifies itself to the Lys form. Receptor-associated plasmin is enzymatically active, monitored as a breakdown of the chromogenic substrate S-2251, and retains its activity in the presence of naturally occurring inhibitors in plasma.

Aprotinin↗

PubMed1992

Extended spectrum beta-lactamase from Klebsiella oxytoca, not belonging to the TEM or SHV family.

In clinical isolates of Klebsiella oxytoca resistance to cefuroxime and aztreonam was mediated by a beta-lactamase, designated KH, (pI 5.25) which could be transferred into Escherichia coli by electroporation, but not by conjugation. The transformants produced two enzymes with pIs 5.25 and 8.4 respectively, and showed resistance to cefuroxime, aztreonam, cefotaxime and ceftazidime. Substrate and inhibition profiles indicated that KH beta-lactamase was different from TEM- or SHV-like enzymes, but similar to chromosomal K1 beta-lactamase. The enzyme profile with pI 8.4 was similar to the enzyme from the recipient and showed elevated activity in transformants. The plasmid profiles of the transformants were different from those of their donors. However, a plasmid fragment of the K. oxytoca isolate KH11 hybridized with a plasmid ranging in size from 4.8 to 7.8 kilobases in all the transformants and most of the donors. Gene probes encoding TEM-1 or SHV-1 did not hybridize with plasmid DNA from the K. oxytoca isolates. Furthermore, a probe of the ampC gene did not hybridize with the plasmid but to DNA fragments of the same size in whole cell DNA preparations from the E. coli XAC recipient and the TKH11 transformants. This indicates that no gross rearrangements in the chromosomal beta-lactamase gene region had occurred in the transformants which could explain the increased expression of the pI 8.4 beta-lactamase.

Aztreonam↗

PubMed1992

Two types of receptors for human plasminogen on group G streptococci.

To investigate the nature of plasminogen binding to streptococci, strains selected for high reactivity with human plasminogen were examined for binding pattern against a panel of plasminogen fragments. The strains included human isolates of groups A, C and G as well as bovine isolates of group G. All strains reacted substantially with the plasminogen fragment kringle 1-3. Using the miniplasminogen fragment (kringle 5 and the B chain) a small but reproducible uptake was detected for human group G strains but not for group A or C strains. The group G strains of bovine origin on the other hand demonstrated high uptake of miniplasminogen, suggesting the possibility of an alternative plasminogen receptor for this species. This interpretation was supported by blocking experiments with the lysine analogue EACA where low concentrations (1 mM) completely blocked plasminogen binding to human streptococci, whereas a 100-fold higher concentration was needed for bovine group G strains. Scatchard plots with human isolates resulted in straight lines and Kd values were generally in the range of 20-80 nM. The number of receptors was estimated to be 45,000 for a selected group A strain and about 10,000 for the selected group C and G strains. Scatchard analysis with bovine group G isolates on the other hand revealed a two phase interaction, supporting the assumption of two different receptor structures on these strains. Kd for the first phase was estimated to be about 20 nM (10,000-20,000 receptors per bacterium), which was similar to the human strains, whereas the second phase was in the range of 400-500 nM (50,000 and 150,000 receptors per bacterium with two selected strains). Scatchard plots with the miniplasminogen fragment as ligand mimicked the phase two reaction with plasminogen, supporting the concept that this reaction represents a new and not previously described receptor. Both the receptor reacting with the kringle 1-3 portion and the one reacting with the miniplasminogen portion bound plasmin and plasminogen with similar affinity.

Aprotinin↗

PubMed1992

Surface-associated activation of plasminogen on gram-positive bacteria. Effect of plasmin on the adherence of Staphylococcus aureus.

In this article we review a novel type of plasminogen activation on staphylococcal and streptococcal cells. The activation mechanism implies a specific binding of glu-plasminogen to bacterial surface via the lysine-binding sites of plasminogen. Association of plasminogen with bacterial surfaces greatly enhances the t-PA mediated activation which takes place only poorly in solution. The end product, surface-associated plasmin, is enzymatically active, protected against high molecular weight plasmin inhibitors and capable of converting itself from glu-plasmin to the lys-form. The modification is associated with an increased affinity of the bound lys-plasmin towards the binding molecules on bacterial surface. This novel way of retaining plasmin on the surface may be important for the bacteria to invade and penetrate surrounding tissues. Our data on the effect of plasmin on staphylococcal adherence indicate that plasmin is not very effective in cleaning bacteria from surfaces coated with extracellular matrix components, fibronectin and fibrinogen.

Bacterial Adhesion↗

PubMed1992

Tissue-type plasminogen activator-mediated activation of plasminogen on the surface of group A, C, and G streptococci.

The interaction of Glu-plasminogen with group A, C, and G streptococci and subsequent formation of surface-associated plasminogen by tissue-type plasminogen activator (t-PA) were studied. Binding of 125I-Glu-plasminogen to streptococci greatly facilitated its activation to 125I-Glu-plasmin by exogenous t-PA, whereas activation in the absence of bacteria took place only slowly. Glu-plasmin formed on the streptococcal surface was further converted to the Lys form. Similar activation and modification took place also in the presence of plasminogen-depleted plasma, containing functional t-PA and plasmin inhibitors, indicating that the surface-associated enzymes were protected against these inhibitors. Lys-plasminogen was 10- to 30-fold more potent than Glu-plasminogen or Glu-plasmin in inhibiting the binding of 125I-Glu-plasminogen to streptococci. This indicated a higher affinity of the Lys form towards plasminogen-binding molecule(s) on the streptococcal surface. The surface-associated plasmin was also enzymically active as judged by digestion of chromogenic substrate S-2251. Surface-associated plasmin activity was observed only when the incubations were carried out in the presence of t-PA and Glu-plasminogen or human plasma as the source of plasminogen. Under these conditions, soluble enzymatic activity was also recovered in the supernatant of group A streptococci. This favors the idea that plasmin can be released from the bacterial surface. The findings provide a mechanism for streptococci to adopt proteolytic activity by binding a host-derived enzyme zymogen on their surface, where the subsequent activation then takes place. The results suggest a role for surface-associated plasmin activity in tissue tropism and tissue invasiveness of streptococci.

Aprotinin↗

PubMed1991

Characterization of Klebsiella oxytoca septicaemia isolates resistant to aztreonam and cefuroxime.

Eleven clinical isolates of Klebsiella oxytoca from Stockholm hospitals were found to be resistant to aztreonam and cefuroxime, but susceptible to cefotaxime, ceftazidime and imipenem. Resistance could be overcome by combining the beta-lactams with the inhibitor clavulanic acid. Crude beta-lactamase preparations from the isolates inactivated aztreonam and cefuroxime rapidly. By isoelectric focusing, a single common beta-lactamase of pI 5.25 was detected. The K. oxytoca isolates belonged to three subgroups, based on their plasmid profiles and Bg/II restriction endonuclease digestion of plasmid DNA. It was concluded that resistance to aztreonam and cefuroxime in these isolates was conferred by a beta-lactamase distinct from TEM-1, TEM-2 and SHV-1, but possibly derived from TEM-like enzymes.

Aztreonam↗

PubMed1991

Comparison of 30 microgram and 120 microgram gentamicin disks for the prediction of gentamicin resistance in Enterococcus faecalis.

Single strain regression analysis was performed on PDM II medium for E. faecalis with 10, 30 and 120 micrograms gentamicin disks using E. faecalis, strain ATCC 29212 as the reference. This method permits the calculation of zone diameters corresponding to different MIC values for different disk contents. The lack of discrimination between normal low-level resistant strains and high-level resistance using the 10 micrograms disk was confirmed. However, both the 30 micrograms and 120 micrograms disks seemed to provide a separation of the normal low-level gentamicin-resistant population from strains with increased resistance. Since the 30 micrograms disk is used routinely in some countries, there should be no need for an extra high content disk in these laboratories. This was confirmed when 96 clinical isolates of E. faecalis were analysed and the results of routine disk diffusion tests were compared with the MIC values. Two of the strains showed high-level gentamicin resistance (greater than 2000 mg/l) and produced no zone of inhibition. The other 94 isolates showed gentamicin MIC values between 4-16 mg/l, and 72 of the MIC results were 8 mg/l. The zone diameters for these strains ranged between 15 and 25 mm with a mean of 18.2 and a median value of 18 mm. In order to include statistical considerations of the zone size populations for setting of breakpoints, a study of gentamicin zone size distributions was performed for several bacterial species. Inhibition zone diameter values around the 30 micrograms gentamicin disk for 2079 clinical isolates of E. faecalis, 2268 S. aureus, 3201 E. coli and 547 strains of P. mirabilis from different years were plotted as histograms. Tests for agreement with a Gaussian distribution showed that the histograms were slightly peaked and skewed towards higher zone values. Parametric and non-parametric statistical tests were compared and the results showed that means and medians were very similar and that parametric fractile estimations at the lower end of the histogram populations were conservative and could be used in view of a slightly lower rate of false resistance. The 1% parametric fractile of 12 mm was selected as a suitable breakpoint for the identification of normal, low-level resistant isolates of E. faecalis using the standardized disk test of the Swedish Reference Group for Antibiotics.

Drug Resistance, Microbial↗

PubMed1991

Antibiotic disk diffusion testing revisited. Single strain regression analysis. Review article.

The standardized (NCCLS, ICS, DIN etc.) disk diffusion method is the most widespread technique for antibiotic susceptibility testing. Interpretive zone breakpoints are calculated from the regular regression line between minimum inhibitory concentrations (MIC) of bacterial isolates and the corresponding inhibition zone diameters around the disk containing the antibiotic. Studies of the regression line has revealed marked differences between different bacterial species. A newly described equation, the single strain regression analysis (SRA) equation, can be used to determine the regression line constants for individual strains. This method was applied to ciprofloxacin and S. aureus, E. faecalis, E. coli, P. mirabilis, P. aeruginosa, and P. maltophilia. The slope and intercept constants were determined for all 40 strains and showed a strong similarity within each species. A close similarity was also observed between the two Pseudomonas species and between S. aureus and E. faecalis. When the regression lines calculated by SRA for individual strains were extrapolated towards higher MIC values, the lines obtained for the more susceptible strains predicted the zones of more resistant strains within the species. The applications of SRA to several other antibiotics and bacterial species in earlier studies were reviewed. One exception to the predictive power of SRA has been detected earlier, H. influenzae and erythromycin. This led to the formulation of the standard curve regression analysis (SCA) equation which requires the use of two or more strains. Methodological aspects of SRA/SCA applications were presented. Three areas are particularly well suited for the use of SRA/SCA: 1. Calculation of interpretive zone breakpoints corresponding to recommended MIC limits in the individual laboratory. 2. Analysis of the effects of various disk contents of antibiotic on the resulting inhibition zones for various bacteria when new antibiotics are introduced. 3. Analytical tool as part of external quality control programmes.

Diffusion↗

PubMed1991

Disk diffusion method for susceptibility testing of Neisseria gonorrhoeae.

The standard medium for disk diffusion and MIC testing of Neisseria gonorrhoeae (that of the National Committee for Clinical Laboratory Standards) was tested to establish zone correlations for the MIC breakpoints currently used in Sweden. Eight gonococcal control strains representing both susceptible and resistant strains and 50 clinical isolates were tested. The standard medium did not support the growth of two control strains and three clinical isolates when the standardized inoculum was used in the disk diffusion test. The same medium with the addition of hemoglobin was introduced. This medium supported the growth of all strains. The correlations between the MICs and the zones of inhibition were calculated for penicillin, ampicillin, cefuroxime, erythromycin, tetracycline, doxycycline, ciprofloxacin, and spectinomycin. The range of MICs for the clinical isolates were broad, without bimodal distribution, for all antibiotics, except ciprofloxacin and spectinomycin. With the susceptibility distribution of MICs and zones near the current susceptible and intermediate or intermediate and resistant limits, a low reproducibility of tests and a high frequency of minor interpretive errors can be expected. A revision of MIC breakpoints seems warranted but can only be done after renewed clinical evaluation of different treatment regimens.

Ampicillin↗

PubMed1990

Antimicrobial susceptibility testing of Haemophilus influenzae. Improvement of accuracy of the disc diffusion test.

A national quality control study was performed in 1986 to investigate the standard of performance of the disc diffusion antimicrobial susceptibility testing of Haemophilus influenzae in Sweden. The accuracy of susceptibility interpretations was unacceptably low. A new standardized method for susceptibility testing of H. influenzae was then worked out, and a new method of setting interpretive zone breakpoints was introduced. The susceptibility category of the main population of clinical isolates was determined according to the MIC50 of the strains. The zone histograms of clinical isolates from five reference laboratories were used for the calculation of interpretive breakpoints. For instance, for susceptible strains the mean of the combined zone values from these laboratories +/- 2 S.D. covered the zone range of the susceptible group, and one more S.D. below covered the intermediate/indeterminate group. The new zone breakpoints would place the main population of clinical isolates in the correct susceptibility group, and even make it possible to detect strains with different degrees of reduced susceptibility in the routine test. In a follow-up quality control study in 1988 the interpretive errors for clinical isolates were eliminated for all antibiotics except doxycycline in some laboratories. Laboratory-related zone breakpoints for doxycycline calculated by the single strain regression analysis method led to correct susceptibility interpretations also in these cases.

Diffusion↗

PubMed1990

Receptors for human plasminogen on gram-negative bacteria.

A total of 188 strains representing 11 species of gram-negative bacteria were examined for the ability to interact with human plasminogen. Highly purified human plasminogen was labeled with 125I, and its uptake by different bacterial strains was measured. All 14 strains of Haemophilus influenzae and all 13 strains of Branhamella catarrhalis tested were positive with respect to plasminogen uptake. Also, eight species belonging to the family Enterobacteriaceae were tested, and of those, Proteus mirabilis demonstrated the most substantial uptake, with 28 of 39 strains taking up more than 10% of the plasminogen. Ten strains of Pseudomonas aeruginosa were also tested, of which seven showed uptake values higher than 10%. With H. influenzae and B. catarrhalis strains, Scatchard analysis indicated a two-phase receptor interaction, one more-avid receptor with a Kd of 6 to 8 nM and 2,000 to 2,500 sites per bacterium and a second receptor with a Kd of 50 to 80 nM and 9,000 sites per bacterium. With Pseudomonas aeruginosa strains, a single receptor interaction was detected with a Kd of 60 nM and the number of sites was estimated as 8,000 per bacterium. Scatchard analysis with strains of P. mirabilis indicated binding of a less-specific nature. However, plasminogen uptake by this species could be reduced by 50% by the addition of 2 mM unlabeled plasminogen. This estimate of Kd, as well as uptake studies with plasminogen fragments, suggests different properties of this receptor. With all receptor types, the addition of plasmin-aprotinin complex inhibited plasminogen uptake, which demonstrates that both forms of the molecule react with the same receptors. Plasminogen uptake could be eliminated by the addition of lysine or epsilon-aminocaproic acid, which suggests that the lysine-binding sites of the plasminogen molecule are involved in the receptor-ligand interaction.

Aprotinin↗

PubMed1990

Receptors for human plasminogen on the biological response modifier OK-432.

The biological response modifier OK-432, constituting cell wall fragments from a group A Streptococcus strain and used in anticancer therapy trials, was tested for its ability to interact with different plasma proteins. The uptake of 125I-labelled protein was measured using a panel of six different plasma proteins all known to react with receptors on a majority of streptococcal strains. Of the proteins tested, plasminogen demonstrated the most substantial uptake, with uptake values ranging from 70 to 79%. A slight interaction with fibrinogen was also detected whereas no significant interaction was found with either human immunoglobulin (Ig)A, IgG, serum albumin, or mouse albumin. The results with plasminogen suggest the possibility of a new explanation of the antitumor activity described for OK-432.

Blood Proteins↗

PubMed1990

Antibiotic susceptibility of Escherichia coli isolates from inpatients with urinary tract infections in hospitals in Addis Ababa and Stockholm.

A high level of antimicrobial resistance of bacteria has been detected at the Tikur Anbessa Hospital (TAH), Addis Ababa, for many years. In contrast, at the Karolinska Hospital (KH), Stockholm, the level of resistance is low. Reported are the results of an investigation of the correlation between antibiotic usage and the antimicrobial resistance rates of Escherichia coli isolates from patients with urinary tract infections in these hospitals. At TAH the strains of E. coli isolated were considerably more resistant to all seven antibiotics tested. The level of multiresistance was 63% at TAH and 7% at KH. There were no significant differences in the total amount of antibiotics used in the two hospitals, except for antituberculosis agents. The strain biotypes and antibiograms, together with the length of patients' hospitalization before a positive urine culture was obtained, suggest that the majority of the strains from TAH were of nosocomial origin.

Cross Infection↗

PubMed1989

In-vitro activity of FCE 22101 against respiratory tract pathogens with reference to production of beta-lactamases.

FCE 22101 is a new penem with broad antibacterial spectrum, excluding the pseudomonads, and has stability to many beta-lactamases. FCE 22101 and imipenem were very potent against the bacteria studied, including beta-lactamase producing strains, which can be isolated from patients with respiratory tract infections (MIC less than or equal to 8 mg/l). No strains were found to be resistant to FCE 22101. FCE 22101 was rapidly bactericidal and more stable to inactivation by beta-lactamases from Branhamella catarrhalis, Haemophilus influenzae, Enterobacter cloacae and Klebsiella pneumoniae than imipenem and ceftibuten. The other antibiotics tested varied in their activities against the respiratory tract pathogens.

Anti-Bacterial Agents↗

PubMed1989

Comparative in-vitro activity of the penem FCE 22101 against recent European blood culture isolates.

Recent blood culture isolates (462 strains of Gram-negative bacilli and 288 strains of staphylococci) collected in 30 European laboratories were tested for susceptibility to five beta-lactam antibiotics by a microdilution method in Mueller-Hinton broth. The penem FCE 22101 and imipenem were very active against the Gram-negative bacilli, except the pseudomonads, FCE 22101 being four- to 16-fold less active (MIC50 2 mg/l; MIC90 8 mg/l) than imipenem MIC50 0.5 mg/l; MIC90 2 mg/l). Ceftibuten and ceftazidime were also active (MIC50 0.25 mg/l; MIC90 greater than 16 mg/l). The MIC of piperacillin (MIC50 8 mg/l; MIC90 greater than 64 mg/l) were two- to 16-fold reduced in the presence of the beta-lactamase inhibitor YTR-830 against these bacteria. Only imipenem and piperacillin inhibited the pseudomonads (MIC50 4 and 8 mg/l respectively; MIC90 16 mg/l and greater than 64 mg/l), with two-fold reduction in MIC50 of piperacillin in the presence of YTR-830. The staphylococci were very susceptible to FCE 22101 and imipenem (MIC50 less than or equal to 0.25 mg/l) except some cefazolin-resistant strains. In Staphylococcus aureus penem resistance was better expressed after bacterial growth at 30 degrees C. Some strains of Staph. epidermidis were susceptible to FCE 22101 but resistant to imipenem. The cephalosporins were not active against the staphylococci, and the presence of YTR-830 caused a four- to 16-fold reduction in MIC of piperacillin.

Anti-Bacterial Agents↗

PubMed1989

Types of interpretive errors in susceptibility testing. Zone breakpoints for norfloxacin disk diffusion testing.

A total of 548 strains of the eleven most common urinary tract pathogens were investigated for possible errors in norfloxacin susceptibility tests comparing MIC determinations with disk diffusion assays. Most strains were found to be sensitive with MIC-90 values below 1.0 for the Enterobacteriaceae while the classical nalidixic acid resistant species, the gram-positive bacteria and Pseudomonas aeruginosa, were less susceptible to norfloxacin with MIC-90 above 1.0 mg/l. MIC-values close to interpretive MIC-limits were recorded for S. faecalis and S. agalactiae using the recommendations of the national Committee for Clinical Laboratory Standards (NCCLS) (susceptible, S less than or equal to 4.0) and for P. aeruginosa and S. aureus using the Swedish Reference Group for Antibiotics (SRGA) standards (S less than or equal to 1.0). Susceptibility interpretations for these species showed a lack of accuracy consistent with methodological problems of reproducibility, an error called type I. The changes in the MIC-limits required for these strains to correct the error would be S less than or equal to 4 for P. aeruginosa and S. aureus, S less than or equal to 8 for S. agalactiae and S less than or equal to 0.5 for S. faecalis. A type II error, occurring when a bacterial species shows a regression line different from the regular line, was also identified for S. saprophyticus. The use of breakpoints derived from single strains regression analysis corrected this error and also reduced the frequency of similar misinterpretations in other species. The term "species-specific MIC-limits" should be introduced along with the established concept of "species-specific interpretive zone breakpoints" to allow for the correction of type I interpretive errors. Type II errors can be corrected by using species-specific interpretive breakpoints, either issued by reference laboratories or derived by calculations from single-strain regression analysis in the individual laboratory.

Microbial Sensitivity Tests↗

PubMed1989

New receptor for human plasminogen on gram positive cocci.

180 bacterial strains representing 17 different species of gram positive cocci were tested for the ability to interact with human plasminogen. Receptors for plasminogen could be detected on 23/24 strains of S. pyogenes, 15/15 strains of S. equisimilis, 14/16 strains of human group G streptococci and 14/14 strains of S. pneumoniae. Eight of nineteen strains representing five species of alpha-hemolytic streptococci were also positive. S. equisimilis demonstrated the highest uptake with a median value of 58 per cent (20%-67%). On the other hand, all strains of S. agalactiae, the majority of S. faecalis and all S. aureus, S. epidermidis and S. saprophyticus strains tested were negative. The concentration of unlabelled plasminogen causing a 50 per cent reduction of bound tracer was between 50 and 150 mM. These estimates of the dissociation constant confirmed the specific nature of the interaction. Binding of plasminogen could be blocked by addition of plasmin-aprotinin complex, suggesting that plasminogen and plasmin bind to the same receptor. Binding was also blocked by the plasminogen fragment kringle 1-3, but not by miniplasminogen, a fragment containing kringle 5 and the B-chain region. As streptokinase interacts mainly with the B-chain of plasmin it is clear that the bacterial receptor for plasminogen is not identical to streptokinase.

Animals↗