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Biomedical subjects

M Saarela

Publications and source records attributed to M Saarela.

At least 55 records · Page 3Linked to original sources
PubMed1996

Oral colonization by more than one clonal type of mutans streptococcus in children with nursing-bottle dental caries.

By ribotyping the genetic diversity of mutans streptococci in six 1.5-3-yr-old children with nursing-bottle caries and in six caries-free, age-matched children and in their mothers was examined. The proportion of mutans streptococci in the dental plaque of the children and their levels in the saliva of the mothers were also examined. For ribotyping, chromosomal DNA of isolates obtained from the plaque of the children (3-12 isolates per child) and from the saliva of the mothers (4-13 isolates per mother) was digested with restriction endonuclease HindIII. The DNA fragments were hybridized to the plasmid pKK3535 which contains the rRNA operon of the Escherichia coli chromosome. The results showed that children with nursing-bottle caries exposed to frequent consumption of sucrose had a high proportion of mutans streptococci in plaque and four of them were colonized with more than one ribotype, whereas caries-free children had a low proportion of mutans streptococci in plaque and only one of them harboured more than one ribotype. Mothers of children with nursing bottle caries had similar levels and numbers of ribotypes of mutans streptococci in saliva as the mothers of the caries-free children. In both child groups, mothers were probably the main source of infection with mutans streptococci. Thus, children with nursing-bottle caries were not only heavily infected with mutans streptococci but also often colonized with more than one clonal type. In the child's acquisition of such clones, frequent sugar consumption may have an important role.

Adult↗
PubMed1996

Similarity of salivary and subgingival Prevotella intermedia and Prevotella nigrescens isolates by arbitrarily primed polymerase chain reaction.

The distribution and the genetic similarity of Prevotella intermedia and Prevotella nigrescens in saliva and in subgingival samples recovered from the same subject were studied in 16 subjects with different periodontal status. The isolates (4 salivary and 4 subgingival P. intermedia/nigrescens group isolates per subject) were identified to species level by hybridization with species-specific oligonucleotide probes, and the clonal analysis was performed using arbitrarily primed polymerase chain reaction (AP-PCR) (all isolates) and ribotyping (isolates from 5 subjects). In addition, the applicability of AP-PCR in differentiating between P. intermedia and P. nigrescens species was tested using 18 P. intermedia and 20 P. nigrescens isolates from 34 subjects. P. intermedia was detected in 7 and P. nigrescens in 14 of the 16 subjects. In all subjects the same species was found both in saliva and in subgingival plaque. In 15 of the 16 subjects, similar AP-PCR types of P. intermedia and/or P. nigrescens between salivary and subgingival samples were found. The salivary and subgingival isolates that were similar by AP-PCR were indistinguishable also by ribotyping. The AP-PCR analysis revealed a P. intermedia or P. nigrescens species-specific AP-PCR product in most isolates. This study indicates that both P. intermedia and P. nigrescens were found both in salivary and in subgingival samples, and both sampling sites within the same individual were usually colonized with identical AP-PCR types of the species. Thus, in addition to a subgingival sample a salivary sample seems to be suitable for detection and clonal analysis of these species. The AP-PCR method proved to be a simple method applicable for differentiation and clonal analysis of P. intermedia and P. nigrescens.

DNA, Bacterial↗
PubMed1996

Distribution and genetic analysis of oral Prevotella intermedia and Prevotella nigrescens.

A total of 344 Prevotella intermedia and nigrescens group isolates from 59 subjects were identified by hybridization with nonradioactively labeled species-specific oligonucleotide probes. Identification of 20 P. intermedia and 46 P. nigrescens isolates was confirmed by analyzing the electrophoretic mobilities of malate and glutamate dehydrogenase enzymes. A total of 111 isolates (32%) were identified as P. intermedia and 233 isolates (68%) as P. nigrescens. Identification performed with oligonucleotide probes and with malate and glutamate dehydrogenase electrophoresis matched perfectly. The distribution of oral P. intermedia and P. nigrescens in various periodontal status groups was investigated in periodontally healthy or diseased individuals. To reveal intra- and interindividual genetic diversity and possible intrafamilial transmission, P. intermedia and P. nigrescens isolates from 16 to 59 subjects, representing 8 married couples, were ribotyped. The stability of colonization was examined in 12 of the 59 subjects, of whom 6 received periodontal treatment and 6 were untreated. All children and periodontally healthy adults and most subjects with initial periodontitis (13/21) harbored only P. nigrescens. Of the 20 subjects with advanced periodontitis, 7 harbored both P. intermedia and P. nigrescens, 7 only P. intermedia and 6 only P. nigrescens. One or two ribotypes of P. intermedia and/or P. nigrescens were found intraindividually. The spouses in 5 of the 8 married couples shared an identical ribotype of P. intermedia or P. nigrescens, whereas ribotypes from unrelated subjects were mostly unique. Colonization was stable, since the same ribotypes were found 1-6 months apart in both periodontally treated and untreated subjects. In conclusion, the study indicates that P. intermedia and P. nigrescens may occur simultaneously in the oral cavity, the colonization is stable and P. intermedia is associated with periodontal diseases. Ribotyping revealed considerable genetic heterogeneity in unrelated subjects, whereas isolates obtained from spouses could represent the same ribotype, which suggests transmission of these species.

Adult↗
PubMed1996

Source of suspected periodontal pathogens re-emerging after periodontal treatment.

To clarify the source of re-emerging periodontal pathogens after treatment, we compared the ribotypes of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia/Prevotella nigrescens group and Campylobacter rectus before and after treatment in 7 periodontitis patients and in 6 of the spouses. The patients harbored A. actinomycetemcomitans, P. gingivalis, P. intermedia/P. nigrescens group or C. rectus in their subgingival or salivary samples before treatment. The respective bacterial species were not detected 1 month after treatment, but reappeared by 6 months later. When available, 4 random colonies of each of the 4 species were isolated from both subgingival and salivary samples at each sampling occasion, the isolates were subcultured, identified and typed applying pheno- and genotypic intraspecies characterization methods. Altogether 90 strains of A. actinomycetemcomitans, P. gingivalis, P. intermedia/P. nigrescens group and C. rectus were available from 2, 3, 2 and 4 patients, respectively. The pre- and post-treatment ribotypes of A. actinomycetemcomitans-, P. gingivalis- and P. intermedia/P. nigrescens group-isolates were identical in all respective patients. The pre- and post-treatment ribotypes of C. rectus were identical in 1 of 4 patients, whereas 2 patients harbored a previously not detected post-treatment ribotype and 1 patient harbored the initial and a previously not detected post-treatment ribotype. To study the possibility that periodontitis patients may acquire strains from the spouse after treatment, isolates of A. actinomycetemcomitans, P. gingivalis, P. intermedia/P. nigrescens group and C. rectus (n = 95) from the patients' spouses were ribotyped and compared with those of the patients. The patient exhibited his own post-treatment ribotypes, different from those of the spouse, of A. actinomycetemcomitans and P. gingivalis in 1 couple and of P. intermedia/P. nigrescens group and C. rectus in 1 couple. In the 2 patients who harbored a previously not detected post-treatment ribotype of C. rectus, one patient shared the new ribotype with the spouse, whereas the other one did not. Although an exogenous source cannot be fully ruled out, the patient's own oral flora seems to be the main source of re-emerging periodontal pathogens after treatment.

Aggregatibacter actinomycetemcomitans↗
PubMed1995

Comparison of arbitrarily primed polymerase chain reaction and ribotyping for subtyping Actinobacillus actinomycetemcomitans.

This study investigated the compatibility of arbitrarily primed polymerase chain reaction (AP-PCR) and ribotyping in the characterization of Actinobacillus actinomycetemcomitans , a major pathogen in the mixed anaerobic microflora of human periodontitis. AP-PCR was performed directly on lysed bacterial colonies using a random-sequence 10-base oligonucleotide primer. Ribotyping was carried out by using purified bacterial chromosomal DNA digested with BglI. DNA fragments were separated electrophoretically, blotted onto a nylon membrane and hybridized with the plasmid pKK3535 containing the rRNA operon of Escherichia coli. The two genetic methods were evaluated on isolates from single individuals and from family members. Twelve AP-PCR types and 47 ribotypes were distinguished among 76 A. actinomycetemcomitans isolates of different serotypes. AP-PCR typing and ribotyping gave compatible results in 18 of 20 comparisons. Although AP-PCR detected less genetic heterogeneity in A. actinomycetemcomitans than ribotyping, the rapid and relatively simple AP-PCR technique seems to be sufficiently discriminative to be used in large scale epidemiological studies which preclude the application of the more laborious ribotyping technique.

Journal Article↗
PubMed1995

Chlorhexidine susceptibilities of mutans streptococcal serotypes and ribotypes.

The susceptibilities of 379 clinical mutans streptococcal isolates to chlorhexidine (CHX) were tested by agar dilution according to the standards of the National Committee for Clinical Laboratory Standards. Isolates were obtained from saliva samples of 34 young mothers who had high or moderate salivary levels of mutans streptococci at baseline. Samples were collected on three occasions, before childbirth, when each child was 6 months old, and 1 year later. Of these isolates, 50% were inhibited at 1 microgram of CHX per ml, 90% were inhibited at 2.0 micrograms/ml, and all were inhibited at 4.0 micrograms/ml. The MICs for Streptococcus mutans isolates (serotypes c, e, and f) were lower than those for Streptococcus sobrinus isolates (serotypes d and g). In some subjects, the MICs for isolates of the same serotype were different. This phenomenon was studied by ribotyping isolates (n = 45) from selected subjects (n = 7). It was found that if there were intraindividual differences in the MICs for isolates of the same serotype, then the ribotypes of these isolates were different. In order to decrease the mutans streptococcal infection risk for children, 24 mothers (test group) brushed their teeth periodically with a gel that contained 0.3% CHX digluconate and 0.2% NaF, pH 5.8, between the second and third sampling occasions. The gel was used twice a day for the first 10 days of each month. Development of resistant strains during CHX-NaF gel use was not detected. The serotype distribution of isolates from the test group after 1 year of periodic CHX-NaF gel use did not differ from that at baseline. Periodic CHX-NaF gel brushing did not lead to lower salivary mutans streptococcal counts.

Adolescent↗
PubMed1994

A variant of the staphylococcal chloramphenicol resistance plasmid pC194 with enhanced ability to transform Lactococcus lactis subsp. lactis.

In our attempts to transform Lactococcus lactis subsp. lactis with pC194, a staphylococcal chloramphenicol resistance plasmid, only a few transformants could be obtained and only when relatively large amounts of plasmid DNA were used. However, when pC194 DNA from lactococcal transformants was introduced back to Staphylococcus aureus and reisolated, it could be retransformed into L. lactis at substantially higher frequencies. It was concluded that pC194 had undergone mutation expanding its host range. By exchanging DNA fragments between the original pC194 and the variant transforming L. lactis (named pVS41), the mutation could tentatively be located within the 1.1-kbp AccI-HaeIII fragment. Comparison of the DNA sequences in the vicinity of the replication plus-origin revealed the formation of an "opal" stop codon (TGA) apparently interrupting the synthesis of the putative protein C for which no function has been described. Cloning this mutation within a 194 bp AccI-MspI fragment on pC194 made this plasmid able to transform L. lactis. Whether the mutation somehow affects functions controlling plasmid host-specificity, or whether the extended host range reflects, for example, mutational inactivation of some lactococcal restriction site, cannot yet be stated on the basis of these data.

Base Sequence↗
PubMed1994

The demonstration by ribotyping of the stability of oral Streptococcus mutans infection over 5 to 7 years in children.

The distribution of serotypes and ribotypes of mutans streptococcal isolates obtained from seven unrelated children at 5 and at 10 or 12 yr of age was investigated. For ribotyping, chromosomal DNA from 5 to 13 isolates per subject was digested with restriction endonucleases EcoRI and HindIII. The DNA fragments were electrophoretically separated, blotted on to nylon membrane and hybridized to the plasmid pKK3535, which contains the rRNA operon of the Escherichia coli chromosome. The ribotypes were unique for each child. In five children only one ribotype and serotype (c, e or f) was found. In one child two serotypes (c and f) were found at baseline and only one (serotype c) in the follow-up sample. In one child the same serotype was not found in the baseline (serotype e) and in the follow-up (serotype c) samples. Every child except one had a ribotype that was identical to one found 5-7 yr later. The results suggest that, at the age of 5 yr, infection by Streptococcus mutans has already stabilized and the colonizing strain remains permanent.

Bacterial Typing Techniques↗
PubMed1994

The oral gram-negative anaerobic microflora in young children: longitudinal changes from edentulous to dentate mouth.

Eruption of primary teeth has a great influence on the oral environment by providing suitable niches for bacterial colonization. The composition of oral gram-negative anaerobic microflora was investigated in 21 young children (mean age 32 months) with primary dentition. The bacterial findings of samples were compared with those of the same children collected at their edentulous infant period (mean age 3 months). During the primary period, 2 samples were collected from each child: a sample with dental floss from gingival margin of 2 teeth and stimulated saliva pooled with a mucosal swab sample. Both samples were cultured aerobically and anaerobically using nonselective and selective media. Prevotella melaninogenica, nonpigmented Prevotella spp., Fusobacterium nucleatum group and Capnocytophaga spp. were found in all children at the older age, whereas they occurred in edentulous mouth in 76%, 62%, 67% and 19%, respectively. The occurrence of Prevotella loescheii increased from 14% to 90%, Prevotella intermedia from 10% to 67%, Leptotrichia spp. from 24 to 71%, Campylobacter (Wolinella) spp. from 5 to 43% and Eikenella corrodens from 5 to 57%. Only the occurrence of Bacteroides gracilis and Veillonella spp. remained at about the same level. Species not isolated from the edentulous mouth, such as Prevotella denticola, Fusobacterium spp. other than the F. nucleatum group and Selenomonas spp. were now detected in 71%, 71% and 43% of the children. The stability of the colonizing P. melaninogenica strain(s) in the oral cavity was determined by using ribotyping; 1-2 isolates per child from the edentulous infant period of 9 children and 3-15 isolates per child from their primary dentition period were analyzed.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Typing Techniques↗
PubMed1994

Transmission of oral Prevotella melaninogenica between a mother and her young child.

Most likely, young children acquire their oral microflora by frequent transfer of bacteria between family members. The possible transmission of obligately anaerobic Prevotella melaninogenica recovered from 11 mother-child pairs was examined by ribotyping. One to 18 isolates (mean 13) per child from different oral sampling sites and 4 to 17 (mean 10) isolates per mother from stimulated salivary samples, collected on 2 occasions, were analyzed. On sampling, the mean ages of the children were 4 months and 32 months, respectively. Restriction endonucleases KpnI and ClaI were chosen for the digestion of chromosomal DNA. DNA fragments were electrophoretically separated, blotted onto a nylon membrane and hybridized with rRNA operon of Escherichia coli. DNA-DNA hybrids were detected immunologically. Extensive genetic heterogeneity, 101 distinct ribotypes, was observed among 248 P. melaninogenica isolates studied. Both mothers and children harbored several (up to 7) ribotypes which, apart from 3 ribotypes, were distinguishable in unrelated subjects. Several P. melaninogenica ribotypes were detected on both sampling occasions over 2 years apart. Identical ribotypes were found in 6 of the 11 mother-child pairs, 1 to 2 similar ribotypes per pair. This suggests the transmission of P. melaninogenica between the mother and her child, probably via maternal saliva. However, the unique ribotypes found in these children also indicate that other sources besides the mother influence the oral colonization of young children.

Adult↗
PubMed1994

Isolation frequency and serotype distribution of mutans streptococci and Actinobacillus actinomycetemcomitans, and clinical periodontal status in Finnish and Vietnamese children.

The isolation frequency and serotype distribution of mutans streptococci and A. actinomycetemcomitans (A.a.) were investigated in a group of Finnish (n = 16) and Vietnamese (n = 16) children, matched by sex, age, and caries status. In the Vietnamese children, the isolation frequencies were higher than in the Finnish children: 100%/62% for mutans streptococci and 78%/13% for A.a. Isolates (n = 3-8) from plaque and saliva were serotyped by immunodiffusion technique using serotype-specific antisera against serotypes c, e, f, d, and g for mutans streptococci and a, b, c, d, and e for A.a. The distribution of mutans streptococci serotypes in Finnish/Vietnamese children was: c 100%/50%; e 10%/31%; d 0%/56%; g 20%/38%. The frequency of plural serotypes was 30%/75%, respectively. In the Vietnamese group the serotype distribution of A.a. was: a 36%, b 27%, and c 63%; 45% of children carried two serotypes. One Finnish child harbored serotype a and one serotype b. The mean percentage of bleeding gingival sites was 7.4 in the Finnish and 15.1 in the Vietnamese group. Calculus and clinically deepened gingival pockets were more frequent findings in the Vietnamese children. The results indicate considerable differences in bacteriologic status and in clinical periodontal status between these Finnish and Vietnamese children.

Aggregatibacter actinomycetemcomitans↗
PubMed1993

Hybridization patterns of Actinobacillus actinomycetemcomitans serotypes a-e detected with an rRNA gene probe.

This study reports a genetic characterization of Actinobacillus actinomycetemcomitans strains in relation to serotypes by using rRNA gene restriction patterns. Eighty-eight clinical strains were isolated from 20 unrelated subjects at one or several occasions. The strains were serotyped by using serotype-specific rabbit antisera against serotypes a, b, c, d or e. Three subjects harbored 2 A. actinomycetemcomitans serotypes, 15 subjects 1 serotype and 2 subjects untypable strains. Chromosomal DNA was digested with restriction endonuclease ClaI, BamHI, BglI or HindIII and hybridized to the rrnB ribosomal RNA operon of the Escherichia coli chromosome. Isolates belonging to the same serotype were genetically identical in the same individual but nonidentical if they belonged to different serotypes. Isolates of the same or different serotypes were genetically nonidentical in different individuals. The banding patterns of A. actinomycetemcomitans isolates recovered from the same individuals during several years always remained identical. The hybridization method using pKK3535 as a probe seemed suitable as an epidemiological tool for comparing the clonal identity of A. actinomycetemcomitans strains.

Adolescent↗
PubMed1993

Ribotyping shows intrafamilial similarity in Actinobacillus actinomycetemcomitans isolates.

This study reports ribosomal RNA gene restriction patterns of 54 Actinobacillus actinomycetemcomitans isolates obtained from 9 families (12 children and 11 parents). The isolates represented serotypes a, b, c and d. The chromosomal DNA extracted from A. actinomycetemcomitans isolates was digested with the restriction endonucleases EcoRI, BamHI, HindIII, ClaI and Bg/I. The DNA fragments were hybridized to the rrnB ribosomal RNA operon of the Escherichia coli chromosome. In 5 families, isolates belonging to the same family (mother and/or father and the children) had identical hybridization patterns when analyzed with all 5 enzymes. In 3 families, each family member harbored only one ribotype of A. actinomycetemcomitans, but at least one member harbored isolates that were of a different ribotype than the other members of the family. In one family, the mother harbored 2 ribotypes (and serotypes), one common with the daughter and one different. In conclusion, the study confirms the previous results that A. actinomycetemcomitans is transmitted intrafamilially.

Adolescent↗
PubMed1993

Transmission of oral bacterial species between spouses.

The transmission of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and mutans streptococci was studied between 4 married couples who suffered from advanced periodontitis. Of the 20 couples investigated, the 4 in which both spouses harbored A. actinomycetemcomitans and P. gingivalis were chosen for the transmission study. Three of these couples also harbored mutans streptococci. A. actinomycetemcomitans isolates (8-24 per subject) and mutans streptococcal isolates (5-23 per subject) were serotyped by immunodiffusion technique. For ribotyping, chromosomal DNA from A. actinomycetemcomitans isolates (4-5 per subject) and mutans streptococcal isolates (4-11 per subject) was digested with restriction endonucleases ClaI or BglI and HindIII or SmaI, respectively. P. gingivalis isolates (2-15 per subject) were ribotyped by using ClaI, BglI and SmaI. The blotted restriction fragments were hybridized to the plasmid pKK3535, which contains the rRNA operon of the E. coli chromosome. The spouses in 2 couples shared the same sero- and ribotypes of A. actinomycetemcomitans and S. mutans. P. gingivalis ribotypes were identical in 2 couples. The result suggests transmission of oral bacteria between spouses.

Adult↗