Salivary levels of suspected periodontal pathogens in relation to periodontal status and treatment

The primary ecological niche for suspected periodontal pathogens seems to be the subgingival area, even though periodontal pathogens are also frequently recovered from saliva. The interrelationship of different periodontal conditions and the salivary levels of suspected periodontal pathogens is not known. In the present study, salivary levels of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Campylobacter rectus, and Peptostreptococcus micros were determined by bacterial culture and related to clinical periodontal status in 40 subjects with either advanced, moderate, or initial/no periodontitis. Culture-positive subjects harbored the 5 bacterial species in mean numbers ranging from 2 x 10(5) to 6 x 10(7) colony-forming units (CFU)/mL saliva. A. actinomycetemcomitans was found in none and P. gingivalis in one of the subjects with initial periodontitis, whereas both species were found in 33% and 44%, respectively, of the subjects with moderate periodontitis and in 60% and 40%, respectively, of the subjects with advanced periodontitis. The mean numbers of CFU/mL of P. intermedia, C. rectus and P. micros were significantly higher in subjects with advanced periodontitis than in subjects with initial/no periodontitis. Ten patients with advanced periodontitis were treated mechanically and with adjunctive systemic metronidazole, and were re-examined 1 and 6 months after treatment. Periodontal treatment eradicated or significantly reduced the levels of salivary periodontal pathogens for half a year, whereas in untreated subjects, the levels and the detection frequencies generally remained fairly stable. In conclusion, the results showed that the salivary levels of periodontal pathogens reflect the periodontal status of the patient.

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.

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.

Actinobacillus actinomycetemcomitans genotypes in relation to serotypes and periodontal status

Actinobacillus actinomycetemcomitans is prevalent in periodontitis but is found in some periodontally healthy individuals as well. The arbitrarily primed polymerase chain reaction (AP-PCR) was used to fingerprint clinical A. actinomycetemcomitans isolates of different serotypes to determine the association between individual clonal types and periodontal conditions. Fifteen different AP-PCR genotypes were distinguished among 93 A. actinomycetemcomitans isolates from 86 uncohabiting individuals with adult periodontitis, localized juvenile periodontitis or no periodontal destruction. The 3 most common AP-PCR genotypes accounted for 68% of the isolates. Seven of the remaining AP-PCR genotypes were found only in periodontitis. The isolates of a given AP-PCR genotype usually belonged to the same serotype. The distribution of the AP-PCR genotypes among serotype b isolates seemed to differ among the subject groups. The results revealed a major genetic dissimilarity between A. actinomycetemcomitans serotypes and suggested a relationship between some A. actinomycetemcomitans clones and periodontal disease.

Periodontal findings in spouses. A clinical, radiographic and microbiological study

Clinical, radiographic and microbiological examination of periodontal conditions was carried out in 2 groups of married couples to assess similarities between husband and wife. The diseased probands (n = 10) exhibited advanced periodontitis and the healthy ones (n = 10) were periodontally normal. The clinical examination comprised the assessment of plaque, probing pocket depths, gingival bleeding on probing, suppuration, supragingival and subgingival calculus. The extent and type of alveolar bone loss was determined from panoramic radiographs. Bacterial samples were taken from the 6 deepest and most inflamed periodontal pockets and from stimulated saliva. The samples were cultured for Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Campylobacter rectus and Peptostreptococcus micros. The mean detection frequency of moderately deep pockets (4-5 mm) and deep pockets (> or = 6 mm) was significantly higher in the diseased probands than in their spouses. The mean detection frequency of moderately deep pockets was significantly higher in the spouses of the diseased probands than in the spouses of the healthy ones. Deep pockets were found in 6 spouses of the diseased probands, whereas only in 2 spouses of the healthy ones. Both diseased proband and his/her spouse harbored A. actinomycetemcomitans, P. gingivalis, P. intermedia, C. rectus and P. micros in 4, 6, 9, 9 and 4 couples, respectively. Both healthy proband and his/her spouse harbored the pathogens in 0, 1, 9, 5 and 3 couples, respectively. P. gingivalis was found in 7 spouses of the diseased probands, but only in 2 spouses of the healthy ones.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for absence in northern Europe of especially virulent clonal types of Actinobacillus actinomycetemcomitans

Genetic analysis of an Actinobacillus actinomycetemcomitans population consisting of 88 clinically well characterized Finnish isolates performed by multilocus enzyme electrophoresis confirmed that the five serotypes divide into two phylogenetic lineages, one comprising serotypes b and c and one comprising serotypes a, d, and e. There was no association between any subpopulation and the periodontal health status of the subject from whom the isolates originated, suggesting that the role of A. actinomycetemcomitans in periodontitis is largely opportunistic in the population examined. Southern blot analyses of genomic DNA digested with each of the restriction endonucleases MspI, RsaI, and TaqI revealed extremely limited genetic polymorphism of the structural leukotoxin gene, ltxA, and its associated promoter. All isolates hybridized to a 530-bp DNA fragment derived from the promoter region of the leukotoxin gene operon of a minimally leukotoxic A. actinomycetemcomitans strain. Deletion of the 530-bp sequence has been associated with significantly increased toxin production detected among isolates from patients with juvenile periodontitis in North America but was detected neither among the 88 isolates in the present collection analyzed nor among more than 60 strains in another population of northern European A. actinomycetemcomitans isolates analyzed previously.

Prognostic criteria for the efficiency of non-surgical periodontal therapy in advanced periodontitis

The aim of the study was to find out which clinical, radiographic and microbiological variables can be used as prognostic criteria for the efficiency of the commonly used initial treatment protocol comprising scaling, root planning and instruction on oral hygiene in advanced adult periodontitis. 46 patients (mean age 48 years) with untreated, advanced periodontitis volunteered for the study. The clinical examination included recordings of plaque, gingival and calculus indices, probing pocket depths, bleeding and suppuration after probing, probing attachment levels and furcation involvements. Infrabony and furcation lesions were assessed from panoramic radiographs. Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis were cultured from the deepest, most inflamed periodontal Pockets, from surface of the tongue and from saliva. 3 months after the completion of non-surgical treatment comprising meticulous scaling and root planing and instruction on oral hygiene, the healing was assessed clinically, and 13 patients were assigned to a maintenance care programme (MC) and 33 to further treatment procedures (FT). Evaluation of the baseline clinical and radiographic data showed a significantly higher %s of > or = 6 mm deep periodontal pockets, surfaces with suppuration, and sites with subgingival calculus, as well as higher numbers of infrabony lesions, in FT-patients than in MC-patients. Subgingival A. actinomycetemcomitans was isolated at baseline in 55% of the FT-patients and in 38% of the MC-patients, and P. gingivalis in 27% and 23%, respectively. A. actinomycetemcomitans was eradicated by non-surgical treatment from only one patient. P. gingivalis was detected in 15% of the patients in both groups after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Absence of Helicobacter pylori in subgingival samples determined by polymerase chain reaction

The polymerase chain reaction was used for the detection of Helicobacter pylori from subgingival plaque in 336 periodontitis patients. A pair of primers derived from the H. pylori urease gene A served to amplify a targeted 411-bp fragment of genomic DNA. This technique permitted the detection of as few as 60 H. pylori cells. Paper point samples from 3 deep periodontal pockets per patient were immersed in 1 ml of phosphate-buffered saline or distilled water, DNA was solubilized by detergent/protease method, 3.7 microliters or 37 microliters of lysate supernatant was used as template, and the amplification product was analyzed in 1% agarose gel containing ethidium bromide. Each experiment included purified DNA and cell lysate of H. pylori as positive controls. The presence of bacteria in the sample was verified by a primer pair common to prokaryote 16S rRNA. The present study did not reveal the specific polymerase chain reaction amplification product characteristic of H. pylori. We conclude that periodontal pockets do not constitute a natural reservoir for H. pylori.

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)

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.

Evaluation of the E test for antimicrobial susceptibility testing of Porphyromonas gingivalis

The antimicrobial susceptibilities of 81 recent clinical Porphyromonas gingivalis isolates and two reference strains were determined by the E test, a new method, and were compared with the minimal inhibitory concentrations for these strains obtained by the reference agar dilution method on supplemented Brucella blood agar. The following agreements were obtained: benzylpenicillin 100%, ampicillin 96%, cefaclor 82%, cefuroxime 91%, erythromycin 93%, clindamycin 99%, tetracycline 66%, doxycycline 89%, metronidazole 77% and ciprofloxacin 77%. Very major discrepancies were observed with ciprofloxacin. This study indicates that the E test is an acceptable method to determine the susceptibility of P. gingivalis for most antimicrobials.

The most frequently isolated gram-negative anaerobes in saliva and subgingival samples taken from young women

Stimulated saliva and a pooled subgingival sample from the first molars were collected from 30 Caucasian women (mean age 30 years) for the presence of gram-negative anaerobic bacteria. The samples were inoculated on nonselective and selective media. The gram-negative anaerobic species occurring in the oral cavity of more than 50% of the subjects were selected for further analysis. Fusobacterium nucleatum and Prevotella melaninogenica were not recovered from subgingival sites without a simultaneous recovery in saliva. When positive subgingivally, Leptotrichia spp., nonpigmented Prevotella spp., Prevotella intermedia, Capnocytophaga spp., Bacteroides gracilis and Prevotella loescheii were simultaneously detected from saliva in 76%, 72%, 64%, 64%, 61% and 55% of the subjects, respectively. Intraindividually, the proportions of F. nucleatum, nonpigmented Prevotella spp., Leptotrichia spp., B. gracilis and P. loescheii of the anaerobic flora were quite similar in the salivary and subgingival samples. Capnocytophaga spp. and P. intermedia were present in higher proportions in subgingival samples than in saliva, whereas P. melaningogenica was present in higher proportions in saliva. Our data indicate that many oral gram-negative anaerobes are frequently recovered from stimulated saliva. Furthermore, when subgingivally positive, most subjects harbored these anaerobes simultaneously in saliva.

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.

Bacteriology of dental infections

The most common dental diseases, periodontal disease and dental caries, are chronic infections caused by bacteria of normal oral flora. When these bacteria increase in number and irritation exceeds the host defence threshold, disease arises. The human oral flora comprises more than 300 different bacteria. During the last decade approximately 10 species, mainly Gram-negative anaerobes, have been noted as putative pathogens in periodontal disease. The Gram-positive and facultatively anaerobic mutans streptococci are aetiologically the most important bacteria in dental caries. Data have rapidly increased on the association of these bacteria with certain periodontal diseases or caries, on phenotypic and genotypic characteristics, pathogenic mechanisms, antibiotic susceptibility patterns and transmission among family members. Chronic dental infections have been the focus of renewed interest because of recent advances in oral microbiology as well as in medicine. We now know that in addition to oral streptococci, recently classified, fastidious periodontal anaerobes can be detected from various extra-oral infections. Oral bacteria may spread into the blood stream through ulcerated epithelium in diseased periodontal pockets and cause transient bacteraemias, which are regarded as increased risk, especially for immunocompromised patients or persons with endoprotheses. In these patients, routine antibiotic prophylaxis is recommended for invasive dental care procedures. Also the new association between dental infections and myocardial/cerebral infarction have offered new challenges for cooperation between dental and medical researchers.

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.

In vitro antimicrobial susceptibility of different serotypes of Actinobacillus actinomycetemcomitans

In vitro susceptibility of Actinobacillus actinomycetemcomitans (A.a.) serotypes to selected antimicrobial agents was investigated by the agar dilution method on supplemented Mueller-Hinton test medium. Eighty-three A.a. strains, 80 recent isolates from 40 periodontally healthy or diseased subjects, and three type strains were included in the study. Serotype a represented 20, serotype b 32, serotype c 17, and serotype e 7 and nontypable 4 of the tested strains. The most effective drugs against all A.a. serotypes in vitro were cefaclor, cefuroxime, tetracycline hydrochloride, doxycycline, trimethoprim-sulfamethoxazole (cotrimoxazole), and ciprofloxacin, which inhibited 100% of the strains at 4.0 micrograms/ml, 4.0 micrograms/ml, 1.0 microgram/ml, 2.0 micrograms/ml, 0.06 microgram/ml, and 0.015 microgram/ml, respectively. Serotypes a and e were more susceptible to cefaclor and cefuroxime than were serotypes b and c; 100% of the first two groups were inhibited at 2.0 micrograms/ml and 1.0 microgram/ml. Ampicillin inhibited 92% of the tested strains at 1.0 microgram/ml. Serotype b was always susceptible to ampicillin. Metronidazole exhibited the best activity against serotype a strains. The lowest minimal inhibitory concentration values for benzylpenicillin, ampicillin, erythromycin, doxycycline, and metronidazole were encountered among serotype b isolates. The results of the present study indicate minor differences in the in vitro antimicrobial susceptibility patterns of different A.a. serotypes, except to metronidazole. Also, the new oral cephalosporins and cotrimoxazole, rare antimicrobial agents in periodontology, showed promising efficacy against all A.a. strains.

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.

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.

beta-Lactamase production and in vitro antimicrobial susceptibility of Porphyromonas gingivalis

beta-Lactamase production by 98 Porphyromonas strains was investigated by the nitrocefin (chromogenic cephalosporin) test. Human isolates of P. gingivalis (91), P. endodontalis (2), and P. asaccharolytica (1) were tested, with four closely related Porphyromonas spp. of animal origin and four reference strains. The in vitro susceptibility of 64 P. gingivalis strains was investigated on Brucella blood agar by the E test. None of the human Porphyromonas isolates tested produced beta-lactamase, but one Porphyromonas strain of animal origin, most closely resembling P. endodontalis, produced beta-lactamase. P. gingivalis was susceptible to almost all of the drugs tested: benzylpenicillin, ampicillin, cefaclor, cefuroxime, erythromycin, clindamycin, tetracycline, doxycycline, metronidazole and ciprofloxacin; all strains were inhibited at 0.016 microgram/ml, 0.023 microgram/ml, 0.315 microgram/ml, 0.064 microgram/ml, 0.19 microgram/ml, 0.016 microgram/ml, 0.094 microgram/ml, 0.047 microgram/ml, 0.023 microgram/ml, and 0.75 microgram/ml of these drugs, respectively. Cotrimoxazole exhibited variable efficacy against P. gingivalis; the range of MICs was 0.1095-32.0 micrograms/ml. The results indicate that beta-lactamase production is currently not a problem amongst clinical isolates of P. gingivalis and strains are susceptible to most antimicrobial agents.

Occurrence of Porphyromonas gingivalis with Prevotella intermedia in periodontal samples

To further examine the previously suggested inverse relationship between Porphyromonas gingivalis and Prevotella intermedia in periodontal disease, 1016 samples taken from single or multiple (pooled) subgingival sites were cultured anaerobically and examined for the simultaneous occurrence of the microorganisms. P. gingivalis was isolated from 297 (29%) and Pr. intermedia from 501 (49%) samples. P. gingivalis was found as frequently with (14%) as without (15%) Pr. intermedia. The type of sampling had no effect on the occurrence of P. gingivalis with Pr. intermedia. However, female subjects harboured them in combination more frequently than male subjects. The mean proportions of P. gingivalis in the cultivable flora appeared to be lower when found with than without Pr. intermedia. Whether the detection of the combination, or P. gingivalis alone, has clinical relevance needs further clarification.

Genetic diversity within isolates of mutans streptococci recognized by an rRNA gene probe

A total of 79 clinical isolates of mutans streptococci and five laboratory strains representing serotypes c, d, e, f, and g were genotyped by a nonradioactive hybridization method with the rrnB rRNA operon of the Escherichia coli chromosome as a probe. The hybridization patterns of chromosomal DNA fragments obtained by digestion with restriction endonucleases HindIII, SmaI, and BamHI revealed genotypic heterogeneity among the serotypes and among isolates of the same serotype recovered from unrelated subjects. Diversity also existed among isolates obtained from a single subject. For 5 of 13 subjects studied, two or three genotypes within serotypes were found, while eight subjects harbored the same number of genotypes as serotypes. The data show that the method utilizing the rRNA gene probe is of value in determining the molecular epidemiology of isolates of mutans streptococci.

Intra- and inter-individual comparison of Porphyromonas gingivalis genotypes

Genetic analysis of 31 clinical strains of Porphyromonas gingivalis isolated from nine subjects, 2-6 strains per subject, was performed by Southern hybridization. Chromosomal DNA was extracted by the method of Moncla et al. [1] and digested to completion with restriction endonucleases PstI, ClaI and BglI. The DNA fragments were separated electrophoretically on agarose gels, transferred to nylon membranes and hybridized to the non-radioactively labelled plasmid pKK 3535 which contains the rmB ribosomal RNA operon of the Escherichia coli chromosome. Of the three enzymes, BglI was the most suitable for the genetic analysis of P. gingivalis. With this enzyme, the intra-individual strains were shown to be identical in eight of the nine subjects, whereas inter-individual strains were different.