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M Saarela

Publications and source records attributed to M Saarela.

At least 37 records · Page 2Linked to original sources
PubMed2000

Comparison of virulence factors of oral Candida dubliniensis and Candida albicans isolates in healthy people and patients with chronic candidosis.

We determined differences in the expression of certain virulence factors between oral Candida dubliniensis and Candida albicans species. In addition, clonal differences were sought among C. albicans isolates recovered from patients with and without compromised immune system. The material comprised 93 clinical yeast isolates originated in 40 subjects (1-5 isolates per subject). All 26 C. dubliniensis isolates and 46 C. albicans isolates originated from healthy routine dental clinic patients. Additionally, 21 C. albicans isolates were collected from patients with autoimmune polyendocrinopathy-candidosis-ectodermal dystrophy (APECED), who have chronic candidosis as one manifestation of their immunocompromising disease. Polymerase chain reaction amplification using the random sequence primer OPE-03 enabled grouping of the C. dubliniensis isolates in 2 genotypes (I and II) and C. albicans isolates in 15 genotypes (I-XV). No significant difference was found in the distribution of genotypes between the patients with APECED and the healthy subjects. C. dubliniensis isolates exhibited high-frequency phenotypic switching significantly more frequently than did C. albicans isolates, and vice versa regarding phospholipase and proteinase production. Proteinase production was significantly more frequent among C. albicans genotype V than genotype IX isolates. No significant difference was found in expression of virulence factors of C. albicans isolates between the patients with APECED and the healthy subjects.

Candida↗
PubMed2000

Altered antigenicity is seen in the lipopolysaccharide profile of non-serotypeable Actinobacillus actinomycetemcomitans strains.

Non-serotypeable Actinobacillus actinomycetemcomitans strains may be derived from the serotypeable ones. In the present study, we compared the outer membrane proteins (OMPs) and lipopolysaccharides (LPSs) of serotypeable and non-serotypeable A. actinomycetemcomitans strains (n=24) of the same genotype in the same subject (n=6) to find out if alterations on the cell-surface contribute to the non-serotypeability. Serotypeable and non-serotypeable A. actinomycetemcomitans strains showed great similarity in the OMP patterns both within and between subjects. Using serotype-specific antisera, clear immunoblotting LPS profiles in the O-antigenic region were seen in serotype b and c strains but not in non-serotypeable strains from the same subjects. The results suggest that changes in LPS lead to the altered antigenicity of non-serotypeable A. actinomycetemcomitans strains.

Actinobacillus Infections↗
PubMed2000

Lactic acid permeabilizes gram-negative bacteria by disrupting the outer membrane.

The effect of lactic acid on the outer membrane permeability of Escherichia coli O157:H7, Pseudomonas aeruginosa, and Salmonella enterica serovar Typhimurium was studied utilizing a fluorescent-probe uptake assay and sensitization to bacteriolysis. For control purposes, similar assays were performed with EDTA (a permeabilizer acting by chelation) and with hydrochloric acid, the latter at pH values corresponding to those yielded by lactic acid, and also in the presence of KCN. Already 5 mM (pH 4.0) lactic acid caused prominent permeabilization in each species, the effect in the fluorescence assay being stronger than that of EDTA or HCl. Similar results were obtained in the presence of KCN, except for P. aeruginosa, for which an increase in the effect of HCl was observed in the presence of KCN. The permeabilization by lactic and hydrochloric acid was partly abolished by MgCl(2). Lactic acid sensitized E. coli and serovar Typhimurium to the lytic action of sodium dodecyl sulfate (SDS) more efficiently than did HCl, whereas both acids sensitized P. aeruginosa to SDS and to Triton X-100. P. aeruginosa was effectively sensitized to lysozyme by lactic acid and by HCl. Considerable proportions of lipopolysaccharide were liberated from serovar Typhimurium by these acids; analysis of liberated material by electrophoresis and by fatty acid analysis showed that lactic acid was more active than EDTA or HCl in liberating lipopolysaccharide from the outer membrane. Thus, lactic acid, in addition to its antimicrobial property due to the lowering of the pH, also functions as a permeabilizer of the gram-negative bacterial outer membrane and may act as a potentiator of the effects of other antimicrobial substances.

Cell Membrane↗
PubMed1999

Age-related acquisition of oral and nasopharyngeal yeast species and stability of colonization in young children.

The occurrence and stability of colonization of oral yeast species and strains was determined from 40 healthy children during a 22-month follow-up at the ages 2, 6, 12, 18 and 24 months. In addition, salivary samples were obtained from the mothers at baseline (2 months) to study the role of the mother as the source of yeasts for the child. Yeasts were recovered at least once from 17/40 (43%) children by the age of 2 years. Of the 40 children, 11 (28%) were yeast-positive at multiple sampling occasions. No significant differences were found in recovery frequency of yeasts at different ages. Candida parapsilosis was isolated in 18/33 (55%) yeast-positive samples, and it predominated (share of positive findings 76%) at ages 12 to 24 months. The same yeast species was rarely detected in successive follow-up samples and thus on species level yeasts were transient colonizers in the developing oral flora of the children. Of the mothers 20/40 (50%) harbored yeasts. Candida albicans was recovered from 19/20 (95%) of the yeast-positive mothers and C. parapsilosis from none. Only 7/20 (35%) of the mothers with a yeast-positive finding had a yeast-positive child. In 5/7 (71%) of these mother-child pairs, both harbored the same yeast species (C. albicans) and in 3/5 (60%) of the pairs the AP-PCR profiles of the yeast isolates were identical suggesting possible transmission. In children, significant relationships (Fisher's exact-test, P < 0.05) were found between recovery of yeasts and use of pacifier at age over 12 months, eruption of first teeth at age over 6 months, mother cooling the child's food by blowing and mother cleaning the child's pacifier in her own mouth. In mothers, a significant relationship existed between recovery of yeasts and use of antibiotics.

Adult↗
PubMed1999

Genotyping of Actinobacillus actinomycetemcomitans serotype d isolates based on polymerase chain reaction.

The aims of the study were to determine the genetic diversity of the rare Actinobacillus actinomycetemcomitans serotype d and to compare the ability of the repetitive extragenic palindromic element (REP)-based polymerase chain reaction (PCR) with that of the arbitrarily primed (AP)-PCR to discriminate between and within A. actinomycetemcomitans serotypes. The material included 26 A. actinomycetemcomitans serotype d isolates, 3 reference strains, and 21 A. actinomycetemcomitans isolates, representing the previously described 17 AP-PCR genotypes from 4 serotypes (a, b, c and e). Among A. actinomycetemcomitans serotype d isolates (n = 26), the AP-PCR primer distinguished 2 genotypes, whereas the REP-primer pair (REP1R-I and REP2-I) and the (GACA)4 primer each produced one genotype. Among the total of 50 A. actinomycetemcomitans isolates, REP-primer pair distinguished 6 genotypes, the primer (GACA)4 7 genotypes, and the AP-PCR 19 genotypes. Among A. actinomycetemcomitans serotype a isolates (n = 6), REP-primer pair yielded 3 genotypes and (GACA)4 and AP-PCR primer 4 genotypes, and among serotype e isolates (n = 6) 3 genotypes. All serotype b isolates (n = 7), representing the AP-PCR genotypes 2, 9, 8, 12, 13, 16 and serotype c isolates (n = 5), AP-PCR genotypes 3, 4, 14, 15, belonged to the (REP1R-I and REP2-I)-PCR genotype 4 and to the (GACA)4-PCR genotype 4. In conclusion, based on both the AP-PCR method and the less discriminative REP-PCR methods, the present genotyping results indicated limited genetic diversity among serotype d isolates of A. actinomycetemcomitans.

Aggregatibacter actinomycetemcomitans↗
PubMed1999

Beta-lactamase production in Prevotella intermedia, Prevotella nigrescens, and Prevotella pallens genotypes and in vitro susceptibilities to selected antimicrobial agents.

The present study investigated the beta-lactamase production of 73 Prevotella intermedia, 84 Prevotella nigrescens, and 14 Prevotella pallens isolates and their in vitro susceptibilities to six antimicrobial agents. The P. intermedia and P. nigrescens isolates were recovered from oral and extraoral samples obtained from subjects in two geographic locations from 1985 to 1995. The clonality of the beta-lactamase-positive and beta-lactamase-negative isolates and the clustering of the genotypes were studied by arbitrarily primed-PCR fingerprinting. beta-Lactamase production was detected in 29% of P. intermedia isolates, 29% of P. nigrescens isolates, and 57% of P. pallens isolates. No difference in the frequencies of beta-lactamase production by P. intermedia and P. nigrescens between isolates from oral and extraoral sites, between isolates obtained at different time periods, or between P. intermedia isolates from different geographic locations was observed. However, the P. nigrescens isolates from the United States were significantly more frequently (P = 0.015) beta-lactamase positive than those from Finland. No association between the genotypes and beta-lactamase production or between the genotypes and the sources of the isolates was found. The penicillin G MICs at which 90% of the isolates were inhibited were 8 microg/ml for P. intermedia, 8 microg/ml for P. nigrescens, and 16 microg/ml for P. pallens. For the beta-lactamase-negative isolates, the corresponding values were 0.031, 0.031, and 0.125 microg/ml, and for the beta-lactamase-positive isolates, the corresponding values were 16, 8, and 32 microg/ml. All isolates were susceptible to amoxicillin-clavulanate, cefoxitin, metronidazole, azithromycin, and trovafloxacin. The MICs of amoxicillin-clavulanate and cefoxitin were relatively higher for the beta-lactamase-positive population than for the beta-lactamase-negative population.

Anti-Bacterial Agents↗
PubMed1999

Comparison of ribotyping, randomly amplified polymorphic DNA analysis, and pulsed-field gel electrophoresis in typing of Lactobacillus rhamnosus and L. casei strains.

A total of 24 strains, biochemically identified as members of the Lactobacillus casei group, were identified by PCR with species-specific primers. The same set of strains was typed by randomly amplified polymorphic DNA (RAPD) analysis, ribotyping, and pulsed-field gel electrophoresis (PFGE) in order to compare the discriminatory power of the methods. Species-specific primers for L. rhamnosus and L. casei identified the type strain L. rhamnosus ATCC 7469 and the neotype strain L. casei ATCC 334, respectively, but did not give any signal with the recently revived species L. zeae, which contains the type strain ATCC 15820 and the strain ATCC 393, which was previously classified as L. casei. Our results are in accordance with the suggested new classification of the L. casei group. Altogether, 21 of the 24 strains studied were identified with the species-specific primers. In strain typing, PFGE was the most discriminatory method, revealing 17 genotypes for the 24 strains studied. Ribotyping and RAPD analysis yielded 15 and 12 genotypes, respectively.

Bacterial Typing Techniques↗
PubMed1998

apaH polymorphism in Clinical Actinobacillus actinomycetemcomitans isolates.

In the present study the apaH polymorphism in clinical A. actinomycetemcomitans isolates were investigated in relation to their serotype and periodontal status of the donor subjects. The material included 122A. actinomycetemcomitans isolates representing serotypes a-e from 103 periodontally healthy and diseased subjects. The apaH polymorphism was investigated by both restriction analysis of the specific PCR amplification product and also by sequencing of PCR amplification products from selected clinical isolates. An apaH specific PCR amplification product was obtained from all isolates but the restriction patterns of the amplification products varied. Serotype c and genogroup 2 within serotype e formed genetically distinct groups, whereas isolates of serotype a, b, d and genogroup 1 within serotype e could not be separated from each other based on the apaH restriction analysis. No relation between the restriction pattern of apaH and the periodontal status of the individuals was detected. These results indicate that serotype c isolates form a uniformly distinct group within A. actinomycetemcomitans and that a subpopulation of serotype e isolates clearly diverge from all other A. actinomycetemcomitans isolates.

Journal Article↗
PubMed1998

Mutacin production by Streptococcus mutans may promote transmission of bacteria from mother to child.

The production of bacteriocin-like inhibitory substances, mutacins, by mutans streptococci varies among isolates. To find if the degree of mutacin activity of an isolate was related to its transmission between mother and her child, 19 mothers and their 18-month- to 3-year-old children were sampled for their oral mutans streptococci. In addition, the stability of mutacin activity was studied with isolates from the mothers and with isolates from five unrelated 5-year-old children in 5- to 7-year follow-up studies. A total of 145 oral mutans streptococcal isolates were serotyped by immunodiffusion, ribotyped, and mutacin typed by the stab culture technique. Mutacin was produced by 88% of the strains against more than 1 of the 14 indicator strains, representing mutans streptococci, Streptococcus sanguis, Streptococcus salivarius, Streptococcus oralis, Streptococcus gordonii, and Streptococcus pyogenes. Streptococcus mutans isolates showed more inhibitory activity than did Streptococcus sobrinus isolates. Identical ribotypes had similar mutacin activity profiles within a subject, initially and in the follow-up studies, in all but two cases. The mothers harbored a total of 37 different mutans streptococcal ribotypes. Six children were negative for mutans streptococci. Transmission was probable in 9 of 20 mother-child pairs on the basis of the presence of identical strains, as determined by ribotyping and bacteriocin (mutacin) typing. S. mutans strains shared between a mother and her child showed a broader spectrum of inhibitory activity than did nontransmitted strains. In conclusion, the mutacin activity of clinical isolates is reasonably stable, and this virulence factor seems to be of clinical importance in early colonization by S. mutans.

Adolescent↗
PubMed1998

Detection of Porphyromonas gingivalis from saliva by PCR by using a simple sample-processing method.

Simple sample-processing methods for PCR detection of Porphyromonas gingivalis, a major pathogen causing adult periodontitis, from saliva were studied. The ability to detect P. gingivalis from 118 salivary samples by PCR after boiling and Chelex 100 processing was compared with bacterial culture. P. gingivalis was detected three times more often by PCR than by culture. Chelex 100 processing of saliva proved to be effective in preventing PCR inhibition and was applied to determine the occurrence of P. gingivalis in saliva samples from 263 Finnish subjects between 5 and 80 years of age. The occurrence of P. gingivalis increased with age, and it was detected by PCR in the saliva of 5.0% of subjects between 5 and 10 years of age, 13.8% of subjects between 11 and 20 years of age, 13.4% of subjects between 21 and 30 years of age, and 63.3% of subjects between 31 and 80 years of age. The results indicate that P. gingivalis is a rare finding in saliva from periodontally healthy children and young adults but a frequent one in saliva from adult periodontitis patients.

Adolescent↗
PubMed1998

Characterization of serologically nontypeable Actinobacillus actinomycetemcomitans isolates.

Our previous studies have shown that Actinobacillus actinomycetemcomitans isolates of a given arbitrarily primed PCR (AP-PCR) genotype belong to the same serotype (of serotypes a through e). In the present study we investigated whether the AP-PCR genotypes of nonserotypeable A. actinomycetemcomitans isolates match those of the serotypeable isolates. The isolates were additionally characterized by restriction analysis of the apaH PCR amplification products. The material included 75 nonserotypeable and 18 serotypeable A. actinomycetemcomitans isolates from 34 epidemiologically unrelated subjects. The serotypeable isolates were obtained from subjects who also harbored nonserotypeable isolates. Eight AP-PCR genotypes were distinguished among the isolates; six genotypes matched those detected in our previous studies, whereas two genotypes were new. Intraindividually, the A. actinomycetemcomitans isolates produced identical AP-PCR banding patterns, regardless of whether they were serotypeable or nonserotypeable, in 22 of 23 subjects participating with multiple isolates. AP-PCR genotype 3, corresponding to serotype c, was by far the most common among the nonserotypeable isolates (62% of subjects). Results obtained with the apaH restriction analysis confirmed the results obtained with AP-PCR for 31 of the 34 subjects. The results suggest that nonserotypeable A. actinomycetemcomitans isolates originate from serotypeable isolates, especially from serotype c isolates, and the likelihood of the existence of additional serotypes is small.

Actinobacillus Infections↗
PubMed1997

Production of glucosyltransferases by clinical mutans streptococcal isolates as determined by semiquantitative cross-dot assay.

Forty-four clinical isolates of mutans streptococci were examined by a semiquantitative cross-dot assay for in vitro production of glucosyltransferases GTF-I, GTF-SI and GTF-S of Streptococcus mutans, and GTF-I of Strep. sobrinus, using monospecific antibodies. The isolates were obtained from 12 1.5- to 3-year old children, six caries-active and six caries-free, and from their mothers. The isolates were selected originally from 243 isolates and they represented 35 genetically distinct types as analysed by serotyping and ribotyping. 27 isolates were of serotype c, nine of serotype e and eight of serotype g. Mother child pairs shared nine ribotypes, suggesting vertical transmission. The results showed that, when cultured in Todd-Hewitt broth supplemented with 1% glucose, all Strep. mutans isolates produced GTF-I and GTF-S and all except two produced GTF-SI of Strep. mutans. All Strep. sobrinus isolates produced GTF-I of Strep. sobrinus. The Strep. mutans GTF-I, GTF-SI and GTF-S production of isolates exhibiting a different ribotype showed variability. The variability of GTF-SI and GTF-S production was less pronounced for serotype e isolates. The GTF-I production by Strep. sobrinus isolates did not vary. Transmitted strains produced the same levels of GTFs as strains that were distinct (not transmitted). Strep. mutans isolates of caries-active children produced the same levels of GTF-I and GTF-S, but tended to produce lower levels of GTF-SI than isolates of caries-free children. In conclusion, the results suggested that Strep. mutans isolates exhibiting a different ribotype often had differences in production of GTFs. However, no clear superiority of the high-producer over the low-producer strains was found in regard to their colonization or caries promotion in young children.

Adult↗
PubMed1997

Role of Porphyromonas gingivalis, Prevotella intermedia, and Prevotella nigrescens in extraoral and some odontogenic infections.

Porphyromonas gingivalis, Prevotella intermedia, and Prevotella nigrescens were isolated from 138 subjects with various infections (intraabdominal, skin and soft-tissue, head and neck, pleuropulmonary, and odontogenic infections and bacteremia). The phenotypic identification of 173 isolates was completed by molecular methods. Arbitrarily primed polymerase chain reaction (AP PCR) analysis was used to determine the genetic similarity of intraindividual P. intermedia/P. nigrescens group isolates recovered from 12 subjects. All 19 P. gingivalis isolates (16 intraabdominal isolates and three odontogenic isolates) hybridized with the P. gingivalis-specific DNA probe. Of the 154 P. intermedia/ P. nigrescens group isolates, 74 were identified as P. intermedia; 78, as P. nigrescens; and 2, as P intermedia/P. nigrescens-like isolates. P. intermedia and P. nigrescens were isolated with equal frequency from patients with all other infections except those with bacteremia, from whom only P. nigrescens isolates were recovered. There were 12 cases in which multiple P. intermedia/ P. nigrescens group isolates were recovered; in nine, only one of the species was isolated, whereas in three, two different species were detected. The intraindividual isolates representing the same species always exhibited identical AP PCR genotypes.

Bacterial Infections↗
PubMed1997

Occurrence of temperate bacteriophages in different Actinobacillus actinomycetemcomitans serotypes isolated from periodontally healthy individuals.

The occurrence of temperate bacteriophages was studied in 34 isolates of Actinobacillus actinomycetemcomitans derived from 27 periodontally healthy Finnish individuals both by lysis/plaque assays and by DNA hybridizations. In addition the serotype, the ribotype and the arbitrarily primed polymerase chain reaction (AP-PCR) profile were determined for each A. actinomycetemcomitans strain. Fourteen isolates showed hybridization patterns very similar to that of a known lysogen when probed with the genome of the previously characterized temperate phage Aa phi 23. Only 6 of these 14 strains had produced lysis or single plaques on suitable indicator strains. Phage Aa phi 247 derived from one of these lysogens was indistinguishable from Aa phi 23 by electron microscopy, and the genomes showed highly related DNA hybridization patterns. The remaining 20 isolates exhibited hybridization patterns very different from that of Aa phi 23 DNA. Seven of these strains also gave lysis or single plaques, suggesting that 21 of the 34 strains were lysogenic. These data indicate that the prophages per se do not represent a virulence factor exclusively associated with periodontal disease. Presence of an Aa phi 23-related prophage correlated with serotype a and AP-PCR type 1 of the bacterial host. This may indicate that Aa phi 23 and related phages have a limited host range.

Adolescent↗
PubMed1997

Phenotypic and genotypic characterization of oral yeasts from Finland and the United States.

A total of 4-22 isolates of oral yeasts per subjects from 48 yeast-positive Finnish and American subjects (25 females and 23 males) were phenotyped and genotyped to determine the frequency of simultaneous oral carriage of multiple yeast taxa. An oral sample from either periodontal pockets, oral mucosa or saliva was obtained. All subjects yielded Candida albicans and 3 subjects an additional yeast species (Candida krusei, Candida glabrata or Saccharomyces cerevisiae). The API 20C Aux kit distinguished 9 different carbohydrate assimilation profiles among the C. albicans isolates. Thirty-eight of 46 C. albicans biotype I isolates were categorized in a single numerical profile. PCR analysis, using a random primer OPA-03 and a repetitive primer (GACA)4, detected 2 major genotypic groups among the C. albicans isolates; 44 subjects showing isolates with a "typical" PCR-profile and 4 subjects isolates with an "atypical" PCR-profile. The "atypical" PCR-profile was similar to that of Candida dubliniensis. All C. albicans isolates assimilated xylose, except 5, including the 4 with an "atypical" PCR-profile. No difference was found in distribution of oral yeast species, and of C. albicans phenotypes and genotypes between Finnish and American subjects. The present PCR method may offer a rapid and easy means of distinguishing oral Candida species.

Adult↗