Search PubMed⌕ Search

Biomedical subjects

M Kilian

Publications and source records attributed to M Kilian.

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

Population structure of Actinobacillus actinomycetemcomitans: a framework for studies of disease-associated properties.

The Actinobacillus actinomycetemcomitans population consists of a large number of clones among which the ubiquitous leukotoxin gene operon appears very homogeneous. Population genetic analyses performed by multilocus enzyme electrophoresis together with DNA fingerprinting and analyses of genomic DNA restriction fragment length polymorphisms (RFLP) on 97 strains isolated over a period of 45 years revealed that each of the serotypes a, b, c, d and e comprise genetically isolated subpopulations and that successful horizontal transfer of genomic DNA between strains of different serotypes appears to be extremely rare in vivo. In contrast, recombination between strains of the same serotype in general appears to take place in nature. The results provide evidence that non-serotypeable strains are serotype antigen-deficient variants originating from strains of the known serotypes. Serotype b and c strains may contain transmittable DNA sequences not found in strains of the other serotypes.

Actinobacillus Infections↗
PubMed1994

Regulation of Actinobacillus actinomycetemcomitans leukotoxin expression: analysis of the promoter regions of leukotoxic and minimally leukotoxic strains.

The leukotoxin of Actinobacillus actinomycetemcomitans has been implicated as a virulence determinant in various human infections and is encoded by a multigene operon consisting of four known genes, designated ltxC, ltxA, ltxB, and ltxD. The ltx operon appears to be present in all A. actinomycetemcomitans strains, but levels of toxin expression vary greatly among strains. Thus, to gain a better understanding of the expression and regulation of the ltx operon, we have analyzed the ltx promoters of a highly toxic (JP2) and a minimally toxic (652) strain of A. actinomycetemcomitans. The nucleotide sequence of the JP2 ltx promoter contains -10 and -35 elements situated 350 bases upstream of ltxC, and primer extension of JP2 RNA confirmed that they are functional in vivo. However, a second primer extension product of 40 bases was present, and analysis of a series of truncated JP2 promoters fused to lacZ suggested that the region immediately upstream of ltxC also promotes transcription in Escherichia coli. These results suggest that two promoters may direct ltx expression in JP2. In addition, a small open reading frame capable of encoding a peptide of 78 amino acids was identified upstream of ltxC. Northern blots showed that this open reading frame is transcribed as part of a 4.2-kb mRNA, a transcript not previously identified as being derived from the ltx operon. In contrast, strain 652 expresses low steady-state levels of ltx mRNA, and its intact ltx promoter was inefficient in transcribing lacZ in E. coli. The nucleotide sequence of the 652 promoter is similar to that of the JP2 promoter but contains a region of 530 bp that is not present in JP2. Of 15 additional strains of A. actinomycetemcomitans that were analyzed, 13 contained promoters resembling the 652 sequence and 2 possessed JP2-like promoters. Both strains possessing the JP2-like promoter expressed 10- to 20-fold-higher levels of leukotoxin than did the strains possessing promoters resembling the 652 promoter. These results suggest that high levels of leukotoxin expression may correlate with the presence of the JP2-like promoter.

Actinobacillus Infections↗
PubMed1994

Antigenic relationships among immunoglobulin A1 proteases from Haemophilus, Neisseria, and Streptococcus species.

To investigate the antigenic variation and relationships of immunoglobulin A1 (IgA1) proteases among different species and genera, we examined a comprehensive collection of serine type and metallo-type IgA1 proteases and corresponding antisera in enzyme neutralization assays. Sharing of neutralizing epitopes of metallo-type IgA1 proteases from Streptococcus pneumoniae, Streptococcus sanguis, Streptococcus mitis, and Streptococcus oralis and of serine type IgA1 proteases from Haemophilus and pathogenic Neisseria species was extremely limited. A number of limited to strong cross-reactions in such epitopes were found among serine type IgA1 proteases released by members of the genera Haemophilus and Neisseria, reflecting the common origin of their iga gene. However, the relatively limited prevalence of shared "neutralizing" epitopes of IgA1 proteases from the two genera indicates that they rarely induce immunity to each other. In contrast, extensive sharing of neutralizing epitopes was found between N. meningitidis and N. gonorrhoeae IgA1 proteases, making them potentially attractive vaccine components. Among metallo-type IgA1 proteases, several pneumococcal proteases were found to induce neutralizing antibodies to IgA1 proteases of oral streptococci whereas the opposite was not the case.

Animals↗
PubMed1993

Optimalization of the detection of NAD dependent Pasteurellaceae from the respiratory tract of slaughterhouse pigs.

NAD dependent members of the family Pasteurellaceae were cultured from the nasal cavity, surface and cut surface of the tonsils, and from the apical and caudal lobes of the lungs of 303 slaughterhouse pigs from 5 different herds in order to obtain information on the ecology of these bacteria. The specimens were plated on two different selective agar media using a special dilution technique that resulted in a good separation of individual colonies. Bacteriological results were compared with serological and pathological findings. The bacteriological examination demonstrated that NAD dependent Pasteurellaceae belonging to the taxa previously described could be isolated from the surface and cut surface of the tonsils, and from lungs with and without gross pathologic lesions. Haemophilus parasuis was detected mainly from the nasal cavity, and Actinobacillus pleuropneumoniae mainly from the surface and cut surface of the tonsils (42%). From two herds, 19% and 24% respectively of the animals without antibodies against A. pleuropneumoniae serotypes 1 and 2 harboured the bacteria mainly in the tonsils. This may reflect a very recent infection or may suggest that A. pleuropneumoniae can colonize the tonsils without inducing a serologic reaction. Serological and bacteriological evidence of more than one serotype in the same herd indicates that natural infection with one serotype does not necessarily protect against another.

Actinobacillus pleuropneumoniae↗
PubMed1993

Chelate root filling cements: biological properties.

The purpose of this study was to test in vivo and in vitro the toxicity and the antibacterial activity of an experimental chelate cement (HN cement) using zinc oxide-eugenol cement as a reference. After subcutaneous injection of the spatulated HN cement paste in rats, it induced markedly less tissue injuries than did the zinc oxide-eugenol cement. In toxicity tests using cultures of human fibroblasts, the HN cement was found to be less toxic than the reference cement. Bacteriologically, blood agar plates inoculated with Streptococcus sanguis, Staphylococcus aureus, and the anaerobic Prevotella intermedia developed inhibition zones between 3 and 12 mm upon application of both cements. Both demonstrated marked bacteriostatic and bactericidal properties.

Animals↗
PubMed1993

Clonal analysis of Streptococcus agalactiae isolated from infants with neonatal sepsis or meningitis and their mothers and from healthy pregnant women.

The purpose of this study was to evaluate if group B streptococci (GBS) isolated from infants with neonatal sepsis or meningitis and their mothers differ from GBS isolated from healthy pregnant women who gave birth to healthy infants. Danish clinical isolates of GBS (n = 118) were characterized by multilocus enzyme electrophoresis, a method recently used to identify virulent clones of GBS type III from North American infants. By analysis of allelic profiles of 11 metabolic enzyme loci, 43 different electrophoretic types were found. Clustering analysis revealed two primary phylogenetic divisions at a distance of > 0.8, both containing serotype III isolates. One division, comprising virtually all disease isolates, showed a population structure like that of traditional pathogens. The other division, containing the majority of carrier isolates, had a structure reminiscent of that of mucosal commensals, with each isolate being different.

Bacteremia↗
PubMed1993

Antigenic variation of immunoglobulin A1 proteases among sequential isolates of Haemophilus influenzae from healthy children and patients with chronic obstructive pulmonary disease.

Considerable antigenic heterogeneity has been identified among Haemophilus influenzae immunoglobulin A1 (IgA1) proteases, and this study increases the number of antigenic types to more than 30. To address the role played in vivo by this polymorphism, sequential H. influenzae isolates from three healthy children and three patients with chronic obstructive pulmonary disease (COPD) were examined. Healthy children showed a frequent clonal exchange, with each replacing clone expressing an antigenic type of IgA1 protease not previously encountered. In contrast, COPD patients were colonized by a single clone for a significantly longer period. In one COPD clone, a change occurred in IgA1 protease cleavage specificity and antigenic properties. In conclusion, frequent exchange of clones expressing antigenically different IgA1 proteases seems to be the principal mechanism by which H. influenzae evades the immune response of healthy children against IgA1 protease. The results support the view that IgA1 protease activity is important for successful colonization of H. influenzae on mucosal membranes.

Adolescent↗
PubMed1993

Similar proportions of immunoglobulin A1 (IgA1) protease-producing streptococci in initial dental plaque of selectively IgA-deficient and normal individuals.

By comparing the initial colonization of cleaned teeth in immunoglobulin A (IgA)-deficient, IgM-compensating individuals with that in normal individuals, no significant difference in the proportion of IgA1 protease-producing streptococci was found. Thus, as one of several bacterial means of immune evasion, the ability to cleave secretory IgA1 does not appear essential to the successful adherence of oral streptococci.

Adolescent↗
PubMed1992

Molecular polymorphism and epidemiology of Neisseria meningitidis immunoglobulin A1 proteases.

Neisseria meningitidis is one of several important bacterial pathogens that secrete a specific protease capable of cleaving human immunoglobulin A1 (IgA1) in the hinge region. To obtain further information on this putative virulence factor, we examined the IgA1 protease and iga gene region of 133 isolates of N. meningitidis assigned to 88 multilocus enzyme genotypes and representing major epidemics and carrier strains from 19 countries. Of the two IgA1 cleavage specificities previously observed, isolates associated with epidemics of meningococcal disease showed exclusively type 1 IgA1 protease activity. Considerable heterogeneity of the N. meningitidis IgA1 protease was demonstrated at both the protein and gene levels. Thus, five different forms of IgA1 protease were detected with enzyme-neutralizing antibodies raised in rabbits. An antiserum raised against a single type 2 IgA1 protease inhibited the enzyme activity of all strains examined, a finding of potential significance for the possible application of IgA1 protease in a vaccine against meningococcal disease. Examination of the iga gene region with restriction endonucleases revealed a high degree of polymorphism among strains belonging to some multilocus enzyme genotypes. The different iga gene types did not correlate with cleavage type or inhibition of the IgA1 protease. Our findings indicate that horizontal genetic exchange occurs in vivo with considerably different frequency in different clones of meningococci.

Carrier State↗
PubMed1992

Serum antibody responses to Streptococcus mutans antigens in humans systemically infected with oral streptococci.

Sera from patients with subacute bacterial endocarditis (SBE) due to Streptococcus mutans or other oral streptococci and from normal subjects were assayed by enzyme-linked immunosorbent assay for antibodies to defined S. mutans antigens. Antibodies of IgG and IgA isotypes to Ag I/II and Ag III were greatly elevated in S. mutans-SBE sera, and the IgA antibodies in 3 sera included both polymeric and monomeric forms. Elevated IgM and IgG anti-lipoteichoic acid and IgG and IgA anti-serotype c polysaccharide antibodies were also found. The sera of 4 of 6 patients infected with other oral streptococci also displayed antibodies to S. mutans Ag I/II. Sera of 3 patients infected with Streptococcus mitis or Streptococcus oralis, but none of the S. mutans-infected cases, showed elevated antibodies to human heart sarcolemma, and all SBE sera had elevated rheumatoid factor. These results suggest that the known surface protein antigens of S. mutans are immunodominant in humans, and are not likely to be heart cross-reactive.

Antibodies, Bacterial↗
PubMed1992

Comparative clinical and microbiological effects of topical subgingival application of metronidazole 25% dental gel and scaling in the treatment of adult periodontitis.

The aim of the study was to compare the clinical and microbiological effects of topical application of a metronidazole gel and a single session of subgingival scaling in the treatment of adult periodontitis. An open, randomized controlled clinical study design was employed. Each of 24 subjects received the 2 treatments simultaneously each in 2 randomly selected quadrants of the dentition. The metronidazole, 25% gel was applied subgingivally on days 0 and 7. Scaling was carried out in one quadrant on day 0 and in one quadrant on day 7. Clinical and microbiological examinations were carried out before treatment and on days 21, 49, 91, 133, and 175 of the experimental period. The microbiological analyses included determination of total anaerobically cultivable bacteria, and relative proportions of anaerobes, aerobes, black-pigmented anaerobic Gram negative rods, Actinobacillus actinomycetemcomitans, streptococci, and spirochetes. Both treatments were effective in reducing probing pocket depth and bleeding on probing. Metronidazole tended to be a little better than scaling during the study period and the clinical effects of both treatments persisted during the whole 6 months observation period. Local metronidazole treatment induced a significant and long-lasting shift in the subgingival flora towards a composition more compatible with health and comparable to that obtained by mechanical debridement. Proportions of black pigmented anaerobes including Prevotella intermedia, and the number of spirochetes were significantly reduced after both treatments with a concomitant increase in the proportions of streptococci. While scaling resulted in a statistically significant increase in the proportion of A. actinomycetemcomitans, this was avoided after metronidazole treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

A comparative genetic study of serologically distinct Haemophilus influenzae type 1 immunoglobulin A1 proteases.

The bacterial immunoglobulin A1 (IgA1) proteases are putative virulence factors secreted by a number of human pathogens capable of penetrating the mucosal barrier. Among Haemophilus influenzae strains, the IgA1 protease is found in several allelic forms with different serological neutralizing properties. A comparison of the primary structures of four serologically distinct H. influenzae IgA1 proteases suggests that this variation is caused by epitopes of the discontinuous conformational type. Analysis of the homologies among the four iga genes indicates that the variation results from transformation and subsequent homologous recombination in the iga gene region among H. influenzae strains. We find evidence for gene rearrangements, including transpositions in the iga gene region encoding the secretory part of the IgA1 preprotease. The amino acid sequence of the C terminus of the preprotease (the beta-core), which is assumed to be involved in secretion of the protease by forming a pore in the outer membrane, is highly conserved. In contrast to conserved areas in the protease domain, the nucleotide sequence encoding the beta-core showed a striking paucity of synonymous site variation.

Alleles↗
PubMed1992

Clonal analysis of the Actinobacillus pleuropneumoniae population in a geographically restricted area by multilocus enzyme electrophoresis.

The genetic diversity among 250 isolates of Actinobacillus pleuropneumoniae from lungs of pigs with pleuropneumonia and from tonsils of apparently healthy pigs at slaughter was estimated by multilocus enzyme electrophoresis. The Danish strains were derived from both specific-pathogen-free and conventional herds. Sixty-six percent of the isolates belonged to three electrophoretic types (ETs) of a total of 37 ETs detected. While five biotype 2 isolates constituted a separate ET closely related to biotype 1 isolates, the type strain of the species (Shope 4074) belonged to its own ET, with a genetic distance of 0.30 from its nearest neighbor. Isolates of serotypes traditionally considered to have less pathogenic potential (serotypes 6, 10, and 12) from herds with acute outbreaks of pleuropneumonia belonged to the same ETs as isolates from apparently healthy pigs, suggesting that factors such as cross immunity and management may lead to divergent clinical results. Isolates from four herds harboring more than one serotype showed distinct profiles between the serotypes, indicating no or only limited chromosomal recombination among clones. Isolates from tonsils belonged to the same ET as isolates from lungs. The same ET was isolated from widely different parts of the world. Evidence from this study indicates that multilocus enzyme electrophoresis may be a valuable tool for the epidemiological analysis of A. pleuropneumoniae.

Actinobacillus pleuropneumoniae↗
PubMed1992

Isolation and characterization of a newly identified Haemophilus species from cats: "Haemophilus felis".

A gram-negative coccobacillus was isolated from the lower respiratory tract of a cat with chronic obstructive pulmonary disease. The isolate required CO2 and V factor for growth and was initially identified as Haemophilus paraphrophilus on the basis of its nutritional requirements, colony morphology, and some biochemical tests. Because of the host specificity of Haemophilus species and discrepancies in catalase, oxidase, and hemolytic activities, additional testing was done. Extensive biochemical testing, G+C content, and DNA reassociation studies indicated that the organism was distinct from other Haemophilus species. Therefore, the organism was identified as a previously unrecognized Haemophilus species and was tentatively named "Haemophilus felis." Bacteria identical to the original isolate were isolated from the nasopharynxes of 6 of 28 apparently normal cats, indicating that H. felis or H. felis-like organisms may be common members of the feline upper respiratory tract flora.

Animals↗
PubMed1991

Ecology of viridans streptococci in the oral cavity and pharynx.

Recently published taxonomic studies of viridans streptococci have resulted in several changes in the nomenclature and definition of oral streptococcal species. With this background, the ecology of streptococci in the oropharyngeal cavities was reinvestigated. The results based on the examination of 1426 streptococcal isolates confirmed and extended earlier findings. Apart from mature supragingival plaque, which contained a mixture of all orally encountered streptococci, each site showed a characteristic streptococcal flora. Initial dental plaque formation is primarily associated with Streptococcus sanguis, Streptococcus mitis biovar 1 and Streptococcus oralis. Our investigation showed that S. sanguis and S. mitis biovar 1 were the most prominent streptococci, also on buccal mucosa. In contrast, S. oralis was almost exclusively found in initial dental plaque. Streptococcus gordonii, formerly part of S. sanguis, was found in small numbers on the oropharyngeal mucosa and in mature supragingival plaque. The dorsum of the tongue was dominated by S. mitis biovar 2 and Streptococcus salivarius, the latter of which was predominant also on the pharyngeal mucosa. Streptococcus anginosus was by far the most predominant streptococcus in subgingival plaque. Immunoglobulin A1 (IgA1) protease-producing streptococci were primarily isolated from initial dental plaque and from the buccal mucosa. This lends further support to the concept of IgA1 proteases being important for the ability of streptococci to evade the local immune defence during their initial colonization of certain oral surfaces.

Adult↗
PubMed1991

Effect of surgical and non-surgical periodontal treatment on periodontal status and subgingival microbiota.

The purpose of this study was to evaluate, on a short-term basis, the clinical and microbiological effects of a single course of scaling and root planing as compared with those obtained by flap surgery in patients with moderate to advanced periodontitis. 11 patients participated in the study. Using a split-mouth design, one quadrant of the mouth was treated with reverse bevel flap surgery, whereas the contralateral one was subjected to a single course of scaling and root planing. 2 approximal sites on single-rooted teeth with a pocket depth greater than or equal to 5 mm were monitored clinically and microbiologically for 16 weeks after active treatment. Both techniques resulted in a gain of probable attachment levels, a reduction in bleeding on probing and a reduced mean pocket depth, although 31.2% of the sites in the scaling and root planing group still had 6-7 mm deep pockets at 8 and 16 weeks after treatment. Both techniques reduced median relative proportions and frequencies of detection of black-pigmented Bacteroides species. A highly statistically significant increase (p less than 0.01) in median proportions of oral streptococci was recorded only for surgery within the 1st month post-operatively. No correlation was found between residual pocket depth and any of the microbiological parameters considered in the study, suggesting that residual pocket depth does not exert a significant influence on bacterial subgingival recolonization after therapy. The results from this study suggest that surgery can be as effective as scaling and root planing in favoring the establishment of micro-organisms compatible with periodontal health, although this effect is limited to the 1st month after therapy.

Adult↗