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K Blom

Publications and source records attributed to K Blom.

14 recordsLinked to original sources
PubMed2004

Pseudomonas aeruginosa-induced infection and degradation of human wound fluid and skin proteins ex vivo are eradicated by a synthetic cationic polymer.

OBJECTIVES: Antimicrobial peptides are important effectors of innate immunity. Bacteria display multiple defence mechanisms against these peptides. For example, Pseudomonas aeruginosa releases potent proteinases that inactivate the human cathelicidin LL-37. Hence, in conditions characterized by persistent bacterial colonization, such as in P. aeruginosa-infected skin wounds, there is a need for efficient means of reducing bacterial load. Here, the effect of the cationic molecule polyhexamethylenebiguanide (PHMB) was evaluated. METHODS: Infection models in human wound fluid and human skin were established. Radial diffusion methods, bacterial growth and bactericidal assays were used for determination of effects of PHMB on bacteria in the presence of plasma, wound fluid or human skin. At the protein and tissue levels, SDS-PAGE, light microscopy and scanning electron microscopy were used to study the effects of P. aeruginosa infection before and after addition of PHMB. RESULTS: PHMB killed common ulcer-derived bacteria in the presence of human wound fluid. Furthermore, elastase-expressing P. aeruginosa completely degraded wound fluid proteins as well as human skin during infection ex vivo. The infection, and consequent protein degradation, was reversed by PHMB. CONCLUSIONS: The ex vivo infection models presented here should be helpful in the screening of novel antimicrobials and constitute a prerequisite for future clinical studies.

Antimicrobial Cationic Peptides↗
PubMed2001

HpaA shows variable surface localization but the gene expression is similar in different Helicobacter pylori strains.

Due to earlier contradictory results regarding the localization of the putative Helicobacter pylori adhesin A (HpaA), we aimed to compare the gene and protein expression and surface localization of HpaA in different H. pylori strains. Five H. pylori strains were cultivated for 11 days and analysed by Northern blot analysis, flow cytometry (FCM), semi-quantitative dot blot, colony blot, immuno-electron microscopy (IEM), and phase-contrast microscopy. The highest transcriptional activity of the hapA gene as observed after 3-4 days of cultivation and two mRNA transcripts of 1600 and 3100 nucleotides, respectively, were detected in all five strains with the hpaA probe. We also showed by reverse transcription-polymerase chain reaction (RT-PCR) that the hpaA gene is co-transcribed with the downstream omp18 gene. The highest total HpaA protein production in bacteria occurred between day 3 and 7, as determined by semi-quantitative dot blot, and was similar in the different strains. The maximal proportion of cells with HpaA on the bacterial surface, detected by FCM, was for strain SS1, 90%; Hel 344, 60%; CCUG 17875, 61%; CCUG 17874, 86% and for strain AH 244 only 35%. By IEM HpaA was detected in all strains both on the bacterial surface and on the flagellar sheath.

Adhesins, Bacterial↗
PubMed2001

Flow cytometric analysis of the localization of Helicobacter pylori antigens during different growth phases.

Previous studies on the localization of several different Helicobacter pylori antigens have been contradictory. We have therefore examined by using both one- and two-color flow cytometry (FCM), immunofluorescence (IF), and immunoelectron microscopy (IEM), the possible surface localization of some H. pylori antigens that may be important virulence factors. All four methods detected the lipopolysaccharide and the N-acetyl-neuroaminyllactose-binding hemagglutinin protein (HpaA) as surface-exposed, while the urease enzyme was not detected at all and the neutrophil activating protein only in low concentration on the surface of the H. pylori bacteria during culture of H. pylori in liquid broth for 11 days. The FCM analysis was found to be quite sensitive and specific and also extremely fast compared with IF and IEM, and therefore the preferred method for detection of surface-localized antigens of H. pylori.

Adhesins, Bacterial↗
PubMed1997

Molecular characterization of the gene encoding H antigen in Escherichia coli and development of a PCR-restriction fragment length polymorphism test for identification of E. coli O157:H7 and O157:NM.

Recent outbreaks of disease caused by Escherichia coli O157:H7 have focused much attention on this newly emerged pathogen. Identification of the H7 flagellar antigen is critical for the confirmation of E. coli O157:H7; however, clinical isolates are frequently nonmotile and do not produce detectable H antigen. To further characterize nonmotile isolates (designated NM), we developed a PCR-restriction fragment length polymorphism (PCR-RFLP) test to identify and characterize the gene encoding the H antigen (fliC) in E. coli. The entire coding sequence of fliC was amplified by PCR, the amplicon was restricted with RsaI, and the restriction fragment pattern was examined after gel electrophoresis. Two hundred eighty E. coli isolates representing serotypes O157:H7 and O157:NM, flagellar antigen H7 groups associated with other O serogroups, and all other flagellar antigen groups were analyzed. A single restriction pattern (pattern A) was identified for O157:H7 isolates, O157:NM isolates that produced Shiga toxin (formerly Shiga-like toxin or verotoxin), and 16 of 18 O55:H7 isolates. Flagellar antigen group H7 isolates of non-O157 serotypes had one of three banding patterns distinct from pattern A. A wide variety of patterns were found among isolates of the other 52 flagellar antigen groups; however, none was identical to the O157:H7 pattern. Thirteen of 15 nonmotile strains that did not produce the A pattern had patterns that matched those of other known H groups. The PCR-RFLP in conjunction with O serogroup determination will be useful in identifying E. coli O157:H7 and related strains that do not express immunoreactive H antigen and could be expanded to include other clinically important E. coli strains.

Antigens, Bacterial↗
PubMed1996

Rapid identification of Campylobacter species by restriction fragment length polymorphism analysis of a PCR-amplified fragment of the gene coding for 16S rRNA.

Restriction fragment length polymorphism analysis of a PCR-amplified DNA fragment of the gene coding for 16S rRNA was performed on 148 previously characterized strains of Campylobacter, Helicobacter, Arcobacter, and Wolinella succinogenes and 13 Campylobacter-like isolates. These strains included clinical, animal, and environmental isolates. PCR amplification generated a 283-bp fragment from all species. The amplicon from each strain was digested with six restriction endonucleases (AccI, AvaI, DdeI, HaeIII, HpaII, XhoI). DdeI was useful for the initial grouping of the strains. Additional discrimination within the different DdeI groups was obtained with AccI, HaeIII, HpaII, and XhoI digestions. The PCR-restriction fragment length polymorphism analysis allowed for the discrimination of members of the genus Campylobacter from members of closely related genera and discrimination between Campylobacter species. The proposed method is simple and rapid and can be useful for the routine identification of Campylobacter-like organisms in clinical or epidemiologic studies.

Animals↗
PubMed1995

Isolation and characterization of a beta-D-glucuronidase-producing strain of Escherichia coli serotype O157:H7 in the United States.

A phenotypic variant of Escherichia coli serotype O157:H7 (G5101) was isolated from a patient with bloody diarrhea. Strain G5101 does not ferment sorbitol but is beta-D-glucuronidase and urease positive. Serotyping and colony hybridization using a serotype-specific DNA probe confirmed that the isolate was O157:H7. G5101 produces Shiga-like toxins I and II and contains an eae gene that is highly conserved in the O157:H7 serotype. This strain would have been missed by laboratories that screen for the sorbitol-negative, beta-D-glucuronidase-negative phenotype in isolating E. coli O157:H7 from clinical and food specimens.

DNA Probes↗
PubMed1995

Identification of Campylobacter fetus by PCR-DNA probe method.

A PCR method for rapid identification of Campylobacter fetus subsp. fetus was evaluated. A fragment of the gene coding for 16S rRNA was amplified from crude cell lysates of 18 C. fetus strains and 30 strains representing other Campylobacter species and subspecies. The amplicons were probed by dot blot hybridization with a digoxigenin-labeled C. fetus-specific oligonucleotide probe. The probe reacted only with C. fetus subsp. fetus and C. fetus subsp. venerealis and may be useful for rapid identification in clinical laboratories.

Bacteriological Techniques↗
PubMed1987

Heredity and alcohol-induced brain anomalies: effects of alcohol on anomalous prenatal development of the corpus callosum and anterior commissure in BALB/c and C57BL/6 mice.

Using two inbred strains of mice which have similar rates of alcohol metabolism, we asked whether prenatal alcohol exposure would cause greater incidence and severity of defects in the development of two forebrain fiber tracts, the corpus callosum and the anterior commissure, in mice prone to these defects (BALB/c) than in mice not prone to these defects (C57BL/6). Pregnant animals were fed 0.6 kcal/g body weight of a Sustacal-based liquid diet containing 0, 15, 17.5, 20, or 25% ethanol-derived calories from day 7 to fetal assessment on day 18 of gestation. Most of alcohol's greatest effects and the greatest strain differences in alcohol's effects on fetal variables were produced by the 17.5% diet. This dose had inhibitory effects on fetal body, brain, and midsagittal corpus callosum and anterior commissure growth. All these effects, except that on brain weight, were significantly greater in C57s than in BALBs. When the results were compared with prenatal growth curves for normal untreated mice, the effect of alcohol on corpus callosum but not anterior commissure growth was largely explained by its effects on overall development. The 17.5% diet had a greater specific effect on size of the anterior commissure in C57s than BALBs but increased the incidence and severity of its permanent dysmorphology in BALBs more than in C57s. Anterior commissure size and morphology may be sensitive indicators of alcohol's effects on prenatal brain development. Hereditary differences in rate of maternal alcohol metabolism no doubt have important consequences for risks arising from prenatal alcohol exposure. However, this study clearly indicates that inherited factors, other than those that influence rate of alcohol metabolism, are important influences on the overall fetal response and the specific responses of the anterior commissure to prenatal alcohol exposure.

Abnormalities, Drug-Induced↗
PubMed1987

Lasting effects on mouse brain growth of 24 hr postpartum deprivation.

When inbred BALB/c mice were separated from their mother for 24 or 36 hr beginning shortly after birth, growth of the body, whole brain and corpus callosum was almost completely stopped. After being returned to their mother, mice deprived for 24 hr gained weight more slowly than non-deprived littermates over the next 6 days but later showed moderate catch-up growth after weaning at 4 weeks of age. After 55 days of recovery, mice deprived for only 24 hr showed significant reductions in brain weight and size of forebrain commissures compared to littermate controls. Approximately twice as many deprived mice had a corpus callosum that was abnormally small compared to controls. These results demonstrate that a rather brief but severe period of separation from the mother can have lasting effects on brain growth.

Animals↗
PubMed1985

Combined effects of moderate ethanol consumption and a low-protein diet during gestation on brain development in BALB/c mice.

We investigated whether or not moderate ethanol consumption during gestation would interact with the effects of a low-protein diet in affecting brain development in BALB/c mice. The independent variables included fetal body and brain weights and cross-sectional area in midsagittal sections of the corpus callosum (CC) and anterior commissure (CA). Pregnant animals were fed either ethanol 12% v/v or an isocaloric sucrose solution from days 5 to 19 of gestation, when fetal development was assessed. In addition, the animals were fed semisynthetic isocaloric diets containing either 8 or 20% casein. All animals were pair-fed to those in the group receiving ethanol and 20% casein; an additional control group was fed lab chow ad libitum. There was clearly an interactive effect of diet and ethanol consumption on blood alcohol concentrations: those in the low-protein group were significantly higher than in the normal-protein group. Similarly, the effect on body weight in the group receiving low protein plus ethanol was greater than the additive effect of either treatment alone, although this may have been due partly to differences in litter size. Brain weight in this group was also significantly less than in the other three groups, which did not differ from each other. Covariance analysis, adjusting brain weight for body weight, suggested a brain-sparing effect of low protein but not ethanol. Neither treatment affected the incidence of the CC being absent at midline. The low-protein treatment decreased the cross-sectional area of both the CC and CA; the effect on the CC was independent of brain weight. There was no effect of ethanol on either of those measures.

Analysis of Variance↗