European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology, Jan 29, 2015
Biofilms are heterogeneous structures composed of bacterial cells surrounded by a matrix and atta... more Biofilms are heterogeneous structures composed of bacterial cells surrounded by a matrix and attached to solid surfaces. The bacteria here are 100 to 1,000 times more tolerant to antimicrobials than corresponding planktonic cells. Biofilms can be difficult to eradicate when they cause biofilm-related diseases, e.g., implant infections, cystic fibrosis, urinary tract infections, and periodontal diseases. A number of phenotypic features of the biofilm can be involved in biofilm-specific tolerance and resistance. Little is known about the molecular mechanisms involved. The current review deals with both phenotypic and molecular mechanisms of biofilm-specific antibiotic tolerance and resistance.
The aim of this study was to determine how fixed orthodontic appliances affect microbiota of supr... more The aim of this study was to determine how fixed orthodontic appliances affect microbiota of supragingival plaque over 5 months. Twenty individuals of Scandinavian origin, aged 10-16 years, were included. All subjects were fitted with fixed orthodontic appliances in both the maxillary and mandibular tooth arches. Pooled supragingival plaque samples from the labial surface of the two maxillary central incisors were collected before bonding (T1) and afterwards at 4 weeks (T2), 3 months (T3) and 5 months (T4). The plaque index (PI) was recorded for each sampling. The gingival status was documented at T1 and T4 by using clinical photographs. Plaque microbiota was identified using the Human Oral Microbe Identification Microarray (HOMIM). Increased plaque levels were recorded after bonding, however the increase was not significant. The prevalence of gingivitis at the maxillary central incisors increased from 25% at T1 to 74% at T4. No significant changes of the plaque microbiota from the ...
International journal of oral and maxillofacial surgery, 2005
According to the current concept of osteoradionecrosis such tissue has become hypoxic, hypovascul... more According to the current concept of osteoradionecrosis such tissue has become hypoxic, hypovascular and hypocellular and it has previously failed to show any bacterial growth. By using a molecular method, i.e., DNA-DNA hybridization, the presence of microorganisms in radionecrotic bone has formerly been demonstrated by us. The aim of the present study was to visualise bacteria in such bone by using scanning and transmission electron microscopy. Fourteen deep medullar specimens from resected radionecrotic mandibles were studied. Microorganisms were detected in 9 of the 14 samples (64%). The bacteria seen included rods, spirochetes and cocci, with rods being the predominant cells. One sample also contained yeasts (blastoconida and pseudohyphae). The data from this study strongly suggest an association between microorganisms and osteoradionecrosis. This may call for a revision of its presumed pathophysiology, including the possibility of an infectious etiology.
The polymerase chain reaction was used to examine 114 tetracycline-resistant anaerobic and facult... more The polymerase chain reaction was used to examine 114 tetracycline-resistant anaerobic and facultative anaerobic bacterial isolates from patients with periodontal disease for the tet(M) and tet(O) genes. A 740-base-pair fragment of the tet(M) gene was amplified from 84 of 114 isolates, and a 519-base-pair fragment of the tet(O) gene was amplified from 13 streptococcal isolates. Six of 7 tetracycline-resistant isolates of Veillonella spp. and tetracycline-resistant isolates of Eubacterium spp. (n = 3), Eubacterium saburreum (n = 1), Streptococcus intermedius (n = 5) and Gemella morbillorum (n = 2) all harbored the tet(M) gene. The tet(M) and tet(O) negative as well as selected positive isolates were tested for the tet(K) and tet(L) genes using DNA probes. All isolates of Staphylococcus spp. (n = 11) hybridized with the tet(K) probe. None of the isolates tested hybridized with the probe for tet(L). This is the first report of the tet(M) gene in the facultative bacterium G. morbillorum...
Oral surgery, oral medicine, and oral pathology, 1984
In nine cases of chronic pericoronitis of lower third molars, the affected teeth were carefully r... more In nine cases of chronic pericoronitis of lower third molars, the affected teeth were carefully removed with the follicles in situ and prepared for scanning electron microscopic (SEM) study. The study disclosed great heterogeneity in the distribution and density of microorganisms on hard as well as soft tissues surrounding the pericoronal pouch. Common features were presence of discrete microenvironments with clusters of bacteria, a decrease in the number of organisms toward the bottom of the pericoronal pouch, and the high proportion of spirochetes, which tended to increase in an apical direction. The study showed leukocytic activity in all areas, and phagocytosis apparently took place on the tissue surfaces within the pericoronal space.
Determination of the composition of the oral microflora has traditionally been based on cultivati... more Determination of the composition of the oral microflora has traditionally been based on cultivation. Treponemes are prevalent in many oral infections but, unfortunately, are not regularly cultured. In this study a new method was established for routine isolation of oral treponemes from clinical samples. Bacterial samples from 47 periodontal pockets and 4 endodontic infections were incubated anaerobically under nitrogen atmosphere at 37 degrees C in U-tubes containing pectin medium. In the U-tube a 'bacterial sample side' and a 'sterile medium side' were established on separate sides of a membrane filter and an agar plug. Using this method we were able to isolate viable treponemes from all bacterial samples. This was in contrast to previously established methods such as the agar dilution technique, the technique involving the membrane filter placed on the surface of solid agar media and the well in agar plate technique. We believe that the 'U-tube method' is a valuable supplement to previously described techniques in routine isolation of treponemes from clinical samples.
Porphyromonas gingivalis and Prevotella intermedia are black-pigmented, putative periodontopathog... more Porphyromonas gingivalis and Prevotella intermedia are black-pigmented, putative periodontopathogenic bacteria considered to cause some forms of periodontal disease. Porphyromonas gingivalis and P. intermedia can be transmitted between humans and produce periodontal disease in susceptible hosts. In this article, studies using molecular typing methods for determining the transmission of black-pigmented, putative periodontopathogens between family members are reviewed. As individuals living close to each other are more prone to transmit bacteria, the studies on transmission of periodontopathogens have been performed on family members. It has been shown that black-pigmented bacteria are not only transferred between spouses but also between parents and child. Since only a limited number of studies have been done, longitudinal and controlled studies should be carried out to elucidate further the transmittance potential of these bacteria.
The focus has traditionally been on bacteria and fungi when discussing microbiological aspects of... more The focus has traditionally been on bacteria and fungi when discussing microbiological aspects of oral disease. Viruses are probably more involved in diseases associated with the oral cavity than has been previously thought. The role of several viruses in ulceration is well known, but viruses of the herpes family may play a role in periodontitis, and papillomaviruses are probably involved in oral cancer. This review offers a brief introduction to virology before discussing the role of the more relevant viruses in oral disease. As to clinical application, it is concluded that the anti-herpes medication may, in some cases, be relevant in treating periodontitis, while papillomavirus vaccine would be expected to decrease the prevalence of oral cancer.
Whole-body autoradiography was used to study thallium uptake and retention in mice during gestati... more Whole-body autoradiography was used to study thallium uptake and retention in mice during gestation. Fifteen minutes after an intraperitoneal injection of 50 microCi 204Tl2SO4 into a 15-day pregnant mouse, thallium could be seen within the fetuses. Maximum fetal accumulation occurred 2-4 h after injection, and minimum at the last observation 4 days after injection. The fetal concentration of 204Tl was constantly lower than the placental. Uptake of 204Tl in embryos, fetuses and placentas of mice with gestation ages varying from 5 days to 16 days indicated that thallium crosses the placental barriers throughout gestation. Thallium was retained by the visceral yolk sac placenta during early gestation, by the visceral yolk sac, chorioallantoic placenta and amnion during late gestation. Over a period of time placental transfer and embryonic/fetal retention of small amounts of thallium may be hazardous to the offspring due to the high cumulative toxicity of this metal.
This study assessed the extent of beta-lactamase-producing bacteria in subgingival plaque samples... more This study assessed the extent of beta-lactamase-producing bacteria in subgingival plaque samples obtained from 25 patients with refractory marginal periodontitis in the USA. beta-Lactamase-positive isolates were characterized using commercial diagnostic kits and partial sequencing of the 16S rRNA gene. The susceptibilities to different antimicrobial agents were tested and, in addition, the isolates were screened for the presence of extended spectrum beta-lactamases (ESBLs). beta-lactamase-producing bacteria were detected in 18 (72%) patients. The most prominent beta-lactamase-producing organisms belonged to the anaerobic genus Prevotella. Other enzyme-producing anaerobic strains were Fusobacterium nucleatum, Propionibacterium acnes and Peptostreptococcus sp. Facultative bacteria, such as Burkholderia spp., Ralstonia pickettii, Capnocytophaga spp., Bacillus spp., Staphylococcus spp. and Neisseria sp., were also detected among the enzyme-producers. Minimum inhibitory concentrations (MICs) of ampicillin and amoxicillin were in the range 1.5-256 micrograms/ml and 4-256 micrograms/ml, respectively, for the isolates of the Prevotella species. All Prevotella isolates were susceptible to amoxicillin/clavulanate and metronidazole, but they showed variable resistance to tetracyclines. Two of the Prevotella isolates had high MICs of cefotaxime and ceftazidime. ESBL activity was not detected in any of the beta-lactamase-producing isolates by the Etest method. Thus, our study demonstrated a wide variety of beta-lactamase-producing bacteria that may play a role in refractory periodontal disease.
The tet(M) genes were characterized from 84 isolates of 10 different bacterial species isolated f... more The tet(M) genes were characterized from 84 isolates of 10 different bacterial species isolated from the periodontal pockets of 16 patients with periodontal disease. A 740 bp polymerase chain reaction product from the hypervariable region of the tet(M) stmctural gene was cleaved with the restriction enzymes Alul and HinfL. Three different restriction pattems were identified for each of the two enzymes. By DNA sequencing, using a direct solid-phase automated sequencing method, the isolates could be grouped into 3 different clusters oftet(M) subtypes. The intemal DNA homology within each subtype was 98-100%; the homology between clusters was 89-94%. Two different subtypes were identified in 9 of 10 bacterial species, and the remaining species had 3 different subtypes. One of the subtypes (M3) was seen mainly in the anaerobic isolates. This subtype was different from all earlier sequenced stmctural tet(M) genes present in the Genbank. Most patients had two different subtypes of tet(M), and a third subtype was seen in the 3 patients who exhibited the greatest variety of tetracycline-resistant bacterial species. It appears that the presence of one subtype of the tet{M) gene within a patient or bacterial species does not prevent the acquisition of another subtype of the same gene. This study identified a new subtype of the tet(M) gene and grouped it into 3 distinct yet highly homologous genetic subtypes.
A 32-yr-old white North American male resident of Norway presented with an asymptomatic radioluce... more A 32-yr-old white North American male resident of Norway presented with an asymptomatic radiolucency first identified 3 yr after the removal of an impacted mandibular right third molar in Southern California 16 yr previously. Surgical exploration revealed an intraosseous cavity filled with a black, homogeneous, gelatinous substance thought to be foreign material, but which was diagnosed histologically as containing black yeasts. Cultivation of a microbiologic sample for 6 wk grew black yeast-like colonies. The yeast isolate was identified as an Aureobasidium species different from the typical A. pullulans. A blood sample was negative with regard to antibodies both with double diffusion technique and ELISA. Also, examination with respect to dermatologic manifestations gave negative results. Flucytocin 10 g/d was administered systemically for 30 d. Six months postoperatively bone regeneration was satisfactory radiologically.
The presence of yeasts in periodontal pockets has been described in a few studies. The associatio... more The presence of yeasts in periodontal pockets has been described in a few studies. The association between yeasts and putative periodontal pathogens is not well described. This study aims at assessing the prevalence of yeasts in periodontal pockets and possible associations with the clinical conditions of the sampled sites and other micro-organisms present. 2 subject groups form the basis for this study. The 1st comprises results from microbiological samples from periodontal pockets of 128 subjects. The 2nd originates from 126 periodontal patients with untreated pockets. Microbiological identification was performed after cultivation on blood and Sabouraud agar plates, and "checkerboard" DNA-DNA hybridisation. The prevalence of subjects with yeasts in the pockets was 15.6% and 17.5% in the 2 groups respectively and was inconsistent according to gender. No correlation was found between age and the presence of yeasts. Eubacterium saburreum was weakly correlated with presence of yeasts (r=0.194 p=0.03). Yeasts were rarely found in both samples from the same individual. Our results indicate that yeasts can be expected to be present in periodontal pockets in one out of 6 periodontal patients independent of gender and age. Eubacterium saburreum seems to occur frequently together with yeasts.
Culture-based studies have shown that Streptococcus mutans and lactobacilli are associated with r... more Culture-based studies have shown that Streptococcus mutans and lactobacilli are associated with root caries (RC). The purpose of the present study was to assess the bacterial diversity of RC in elderly patients by use of culture-independent molecular techniques and to determine the associations of specific bacterial species or bacterial communities with healthy and carious roots. Plaque was collected from root surfaces of 10 control subjects with no RC and from 11 subjects with RC. The bacterial 16S rRNA genes from extracted DNA were PCR amplified, cloned, and sequenced to determine species identity. From a total of 3,544 clones, 245 predominant species or phylotypes were observed, representing eight bacterial phyla. The majority (54%) of the species detected have not yet been cultivated. Species of Selenomonas and Veillonella were common in all samples. The healthy microbiota included Fusobacterium nucleatum subsp. polymorphum , Leptotrichia spp., Selenomonas noxia , Streptococcus ...
In this study, an unusual observation of Saccharomyces cerevisiae isolated from an infected root ... more In this study, an unusual observation of Saccharomyces cerevisiae isolated from an infected root canal and from the blood of a patient undergoing endodontic therapy of a tooth with asymptomatic apical periodontitis is reported. Phenotypic (biochemical tests, antifungal susceptibility tests and SDS-PAGE of cellular proteins) and genetic (ribotyping) methods were used to characterize the strains. By using these methods it was found that the blood and root canal isolates were identical but differed from S. cerevisiae strains of other sources. It was therefore more than likely that the root canal was the source of the blood isolate and that it had been transferred unintentionally to the bloodstream during root canal treatment.
This study compared the sonic sensitivity of 12 Gram-negative and two Gram-positive bacteria comm... more This study compared the sonic sensitivity of 12 Gram-negative and two Gram-positive bacteria commonly encountered in plaque associated with periodontal diseases. Pure bacterial cultures were grown to standard turbidity, diluted in 1/4 strength prereduced anaerobically sterilized Ringer's solution, and aliquots dispersed for 0-180 s, using an MSE sonic oscillator at 6 micron under 80% N2, 10% H2 and 10% CO2. Viable recoveries were determined on anaerobically cultured trypticase soy 5% blood agar plates. Breakage of T. denticola was assessed by electron microscopy. Gram-positive organisms tolerated sonication better than Gram-negative. A. viscous was more resistant than Strep sanguis. Gram-negative bacteria could be divided into groups according to their sensitivity. Eikenella corrodens was most resistant, followed by F. nucleatum B asaccharolyticus, Capnocytophaga gingivalis, A actinomycetemcomitans, a strain (2097) of Group IV Bacteroides, and B melaninogenicus ss intermedius resisted sonication better than "corroding' Bacteroides and oral Campylobacter. T. denticola, Selenomonas sputigena and Wolinella were most sensitive with viable counts which declined after sonication for 5-10 s. Recoveries from plaque taken from five patients with periodontal diseases increased with sonication time, reaching higher values for suprangingival than for subgingival samples.
The distribution patterns of 90Sr in five littermate, 8-day-old Wistar rats were studied by whole... more The distribution patterns of 90Sr in five littermate, 8-day-old Wistar rats were studied by whole body autoradiography. Rats were killed 15 min, 1, 4, 24, and 72 h after a single intraperitoneal injection of the isotope. Immediately after administration, 90Sr was distributed throughout most of the soft tissues of the body. The soft tissue deposits had practically disappeared after 4 h. In the hard tissues of the body 90Sr accumulated up to 24-72 h. Fifteen minutes after injection the uptake of 90Sr in the enamel of the teeth was highest in the occlusal and incisal regions. 90Sr gradually accumulated throughout the enamel and after 72 h its distribution in this layer was fairly uniform. Immediately after injection a narrow zone of radioactivity appeared in the dentin near the pulp. This zone broadened with time towards the dentinoenamel junction and included the entire dentin layer 72 h after injection. Initially, the uptake of 90Sr was higher in the dentin thatn in the enamel, particularly in the cervical areas of the crown. This difference became less apparent with time. There was good correlation between the uptake in teeth and bones, supporting the use of teeth as indicators of the 90Sr body burden.
An experimental model of yeast-induced denture stomatitis has been set up in the rat by inoculati... more An experimental model of yeast-induced denture stomatitis has been set up in the rat by inoculating Candida albicans on the fitting side of a maxillary acrylic plate retained by an orthodontic band around the incisors. Thirty-eight Wistar rats were used in two series of experiments with an observation period of 2 weeks. In each of the series there were one control and three experimental groups. Control rats were left untreated, while rats of the experimental groups wore either uninoculated or inoculated plates, or had their palatal mucosa smeared with the yeast. For cytologic examination the palate was scraped in Series I and the fitting side of the plate in Series II. After 1 week a generalized simple inflammation had developed in the palate of most animals of the experimental groups. It was most severe and persistent in rats with inoculated plates. Histologic signs of inflammation and hyphal formation were also most pronounced in this group. Hyphae did not invade the epithelium. Except for an initial loss of body weight, which was restored by day 10 or 12, the rats tolerated their plates. The Wistar rat seems to be well suited for experimental studies on denture stomatitis.
European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology, Jan 29, 2015
Biofilms are heterogeneous structures composed of bacterial cells surrounded by a matrix and atta... more Biofilms are heterogeneous structures composed of bacterial cells surrounded by a matrix and attached to solid surfaces. The bacteria here are 100 to 1,000 times more tolerant to antimicrobials than corresponding planktonic cells. Biofilms can be difficult to eradicate when they cause biofilm-related diseases, e.g., implant infections, cystic fibrosis, urinary tract infections, and periodontal diseases. A number of phenotypic features of the biofilm can be involved in biofilm-specific tolerance and resistance. Little is known about the molecular mechanisms involved. The current review deals with both phenotypic and molecular mechanisms of biofilm-specific antibiotic tolerance and resistance.
The aim of this study was to determine how fixed orthodontic appliances affect microbiota of supr... more The aim of this study was to determine how fixed orthodontic appliances affect microbiota of supragingival plaque over 5 months. Twenty individuals of Scandinavian origin, aged 10-16 years, were included. All subjects were fitted with fixed orthodontic appliances in both the maxillary and mandibular tooth arches. Pooled supragingival plaque samples from the labial surface of the two maxillary central incisors were collected before bonding (T1) and afterwards at 4 weeks (T2), 3 months (T3) and 5 months (T4). The plaque index (PI) was recorded for each sampling. The gingival status was documented at T1 and T4 by using clinical photographs. Plaque microbiota was identified using the Human Oral Microbe Identification Microarray (HOMIM). Increased plaque levels were recorded after bonding, however the increase was not significant. The prevalence of gingivitis at the maxillary central incisors increased from 25% at T1 to 74% at T4. No significant changes of the plaque microbiota from the ...
International journal of oral and maxillofacial surgery, 2005
According to the current concept of osteoradionecrosis such tissue has become hypoxic, hypovascul... more According to the current concept of osteoradionecrosis such tissue has become hypoxic, hypovascular and hypocellular and it has previously failed to show any bacterial growth. By using a molecular method, i.e., DNA-DNA hybridization, the presence of microorganisms in radionecrotic bone has formerly been demonstrated by us. The aim of the present study was to visualise bacteria in such bone by using scanning and transmission electron microscopy. Fourteen deep medullar specimens from resected radionecrotic mandibles were studied. Microorganisms were detected in 9 of the 14 samples (64%). The bacteria seen included rods, spirochetes and cocci, with rods being the predominant cells. One sample also contained yeasts (blastoconida and pseudohyphae). The data from this study strongly suggest an association between microorganisms and osteoradionecrosis. This may call for a revision of its presumed pathophysiology, including the possibility of an infectious etiology.
The polymerase chain reaction was used to examine 114 tetracycline-resistant anaerobic and facult... more The polymerase chain reaction was used to examine 114 tetracycline-resistant anaerobic and facultative anaerobic bacterial isolates from patients with periodontal disease for the tet(M) and tet(O) genes. A 740-base-pair fragment of the tet(M) gene was amplified from 84 of 114 isolates, and a 519-base-pair fragment of the tet(O) gene was amplified from 13 streptococcal isolates. Six of 7 tetracycline-resistant isolates of Veillonella spp. and tetracycline-resistant isolates of Eubacterium spp. (n = 3), Eubacterium saburreum (n = 1), Streptococcus intermedius (n = 5) and Gemella morbillorum (n = 2) all harbored the tet(M) gene. The tet(M) and tet(O) negative as well as selected positive isolates were tested for the tet(K) and tet(L) genes using DNA probes. All isolates of Staphylococcus spp. (n = 11) hybridized with the tet(K) probe. None of the isolates tested hybridized with the probe for tet(L). This is the first report of the tet(M) gene in the facultative bacterium G. morbillorum...
Oral surgery, oral medicine, and oral pathology, 1984
In nine cases of chronic pericoronitis of lower third molars, the affected teeth were carefully r... more In nine cases of chronic pericoronitis of lower third molars, the affected teeth were carefully removed with the follicles in situ and prepared for scanning electron microscopic (SEM) study. The study disclosed great heterogeneity in the distribution and density of microorganisms on hard as well as soft tissues surrounding the pericoronal pouch. Common features were presence of discrete microenvironments with clusters of bacteria, a decrease in the number of organisms toward the bottom of the pericoronal pouch, and the high proportion of spirochetes, which tended to increase in an apical direction. The study showed leukocytic activity in all areas, and phagocytosis apparently took place on the tissue surfaces within the pericoronal space.
Determination of the composition of the oral microflora has traditionally been based on cultivati... more Determination of the composition of the oral microflora has traditionally been based on cultivation. Treponemes are prevalent in many oral infections but, unfortunately, are not regularly cultured. In this study a new method was established for routine isolation of oral treponemes from clinical samples. Bacterial samples from 47 periodontal pockets and 4 endodontic infections were incubated anaerobically under nitrogen atmosphere at 37 degrees C in U-tubes containing pectin medium. In the U-tube a 'bacterial sample side' and a 'sterile medium side' were established on separate sides of a membrane filter and an agar plug. Using this method we were able to isolate viable treponemes from all bacterial samples. This was in contrast to previously established methods such as the agar dilution technique, the technique involving the membrane filter placed on the surface of solid agar media and the well in agar plate technique. We believe that the 'U-tube method' is a valuable supplement to previously described techniques in routine isolation of treponemes from clinical samples.
Porphyromonas gingivalis and Prevotella intermedia are black-pigmented, putative periodontopathog... more Porphyromonas gingivalis and Prevotella intermedia are black-pigmented, putative periodontopathogenic bacteria considered to cause some forms of periodontal disease. Porphyromonas gingivalis and P. intermedia can be transmitted between humans and produce periodontal disease in susceptible hosts. In this article, studies using molecular typing methods for determining the transmission of black-pigmented, putative periodontopathogens between family members are reviewed. As individuals living close to each other are more prone to transmit bacteria, the studies on transmission of periodontopathogens have been performed on family members. It has been shown that black-pigmented bacteria are not only transferred between spouses but also between parents and child. Since only a limited number of studies have been done, longitudinal and controlled studies should be carried out to elucidate further the transmittance potential of these bacteria.
The focus has traditionally been on bacteria and fungi when discussing microbiological aspects of... more The focus has traditionally been on bacteria and fungi when discussing microbiological aspects of oral disease. Viruses are probably more involved in diseases associated with the oral cavity than has been previously thought. The role of several viruses in ulceration is well known, but viruses of the herpes family may play a role in periodontitis, and papillomaviruses are probably involved in oral cancer. This review offers a brief introduction to virology before discussing the role of the more relevant viruses in oral disease. As to clinical application, it is concluded that the anti-herpes medication may, in some cases, be relevant in treating periodontitis, while papillomavirus vaccine would be expected to decrease the prevalence of oral cancer.
Whole-body autoradiography was used to study thallium uptake and retention in mice during gestati... more Whole-body autoradiography was used to study thallium uptake and retention in mice during gestation. Fifteen minutes after an intraperitoneal injection of 50 microCi 204Tl2SO4 into a 15-day pregnant mouse, thallium could be seen within the fetuses. Maximum fetal accumulation occurred 2-4 h after injection, and minimum at the last observation 4 days after injection. The fetal concentration of 204Tl was constantly lower than the placental. Uptake of 204Tl in embryos, fetuses and placentas of mice with gestation ages varying from 5 days to 16 days indicated that thallium crosses the placental barriers throughout gestation. Thallium was retained by the visceral yolk sac placenta during early gestation, by the visceral yolk sac, chorioallantoic placenta and amnion during late gestation. Over a period of time placental transfer and embryonic/fetal retention of small amounts of thallium may be hazardous to the offspring due to the high cumulative toxicity of this metal.
This study assessed the extent of beta-lactamase-producing bacteria in subgingival plaque samples... more This study assessed the extent of beta-lactamase-producing bacteria in subgingival plaque samples obtained from 25 patients with refractory marginal periodontitis in the USA. beta-Lactamase-positive isolates were characterized using commercial diagnostic kits and partial sequencing of the 16S rRNA gene. The susceptibilities to different antimicrobial agents were tested and, in addition, the isolates were screened for the presence of extended spectrum beta-lactamases (ESBLs). beta-lactamase-producing bacteria were detected in 18 (72%) patients. The most prominent beta-lactamase-producing organisms belonged to the anaerobic genus Prevotella. Other enzyme-producing anaerobic strains were Fusobacterium nucleatum, Propionibacterium acnes and Peptostreptococcus sp. Facultative bacteria, such as Burkholderia spp., Ralstonia pickettii, Capnocytophaga spp., Bacillus spp., Staphylococcus spp. and Neisseria sp., were also detected among the enzyme-producers. Minimum inhibitory concentrations (MICs) of ampicillin and amoxicillin were in the range 1.5-256 micrograms/ml and 4-256 micrograms/ml, respectively, for the isolates of the Prevotella species. All Prevotella isolates were susceptible to amoxicillin/clavulanate and metronidazole, but they showed variable resistance to tetracyclines. Two of the Prevotella isolates had high MICs of cefotaxime and ceftazidime. ESBL activity was not detected in any of the beta-lactamase-producing isolates by the Etest method. Thus, our study demonstrated a wide variety of beta-lactamase-producing bacteria that may play a role in refractory periodontal disease.
The tet(M) genes were characterized from 84 isolates of 10 different bacterial species isolated f... more The tet(M) genes were characterized from 84 isolates of 10 different bacterial species isolated from the periodontal pockets of 16 patients with periodontal disease. A 740 bp polymerase chain reaction product from the hypervariable region of the tet(M) stmctural gene was cleaved with the restriction enzymes Alul and HinfL. Three different restriction pattems were identified for each of the two enzymes. By DNA sequencing, using a direct solid-phase automated sequencing method, the isolates could be grouped into 3 different clusters oftet(M) subtypes. The intemal DNA homology within each subtype was 98-100%; the homology between clusters was 89-94%. Two different subtypes were identified in 9 of 10 bacterial species, and the remaining species had 3 different subtypes. One of the subtypes (M3) was seen mainly in the anaerobic isolates. This subtype was different from all earlier sequenced stmctural tet(M) genes present in the Genbank. Most patients had two different subtypes of tet(M), and a third subtype was seen in the 3 patients who exhibited the greatest variety of tetracycline-resistant bacterial species. It appears that the presence of one subtype of the tet{M) gene within a patient or bacterial species does not prevent the acquisition of another subtype of the same gene. This study identified a new subtype of the tet(M) gene and grouped it into 3 distinct yet highly homologous genetic subtypes.
A 32-yr-old white North American male resident of Norway presented with an asymptomatic radioluce... more A 32-yr-old white North American male resident of Norway presented with an asymptomatic radiolucency first identified 3 yr after the removal of an impacted mandibular right third molar in Southern California 16 yr previously. Surgical exploration revealed an intraosseous cavity filled with a black, homogeneous, gelatinous substance thought to be foreign material, but which was diagnosed histologically as containing black yeasts. Cultivation of a microbiologic sample for 6 wk grew black yeast-like colonies. The yeast isolate was identified as an Aureobasidium species different from the typical A. pullulans. A blood sample was negative with regard to antibodies both with double diffusion technique and ELISA. Also, examination with respect to dermatologic manifestations gave negative results. Flucytocin 10 g/d was administered systemically for 30 d. Six months postoperatively bone regeneration was satisfactory radiologically.
The presence of yeasts in periodontal pockets has been described in a few studies. The associatio... more The presence of yeasts in periodontal pockets has been described in a few studies. The association between yeasts and putative periodontal pathogens is not well described. This study aims at assessing the prevalence of yeasts in periodontal pockets and possible associations with the clinical conditions of the sampled sites and other micro-organisms present. 2 subject groups form the basis for this study. The 1st comprises results from microbiological samples from periodontal pockets of 128 subjects. The 2nd originates from 126 periodontal patients with untreated pockets. Microbiological identification was performed after cultivation on blood and Sabouraud agar plates, and "checkerboard" DNA-DNA hybridisation. The prevalence of subjects with yeasts in the pockets was 15.6% and 17.5% in the 2 groups respectively and was inconsistent according to gender. No correlation was found between age and the presence of yeasts. Eubacterium saburreum was weakly correlated with presence of yeasts (r=0.194 p=0.03). Yeasts were rarely found in both samples from the same individual. Our results indicate that yeasts can be expected to be present in periodontal pockets in one out of 6 periodontal patients independent of gender and age. Eubacterium saburreum seems to occur frequently together with yeasts.
Culture-based studies have shown that Streptococcus mutans and lactobacilli are associated with r... more Culture-based studies have shown that Streptococcus mutans and lactobacilli are associated with root caries (RC). The purpose of the present study was to assess the bacterial diversity of RC in elderly patients by use of culture-independent molecular techniques and to determine the associations of specific bacterial species or bacterial communities with healthy and carious roots. Plaque was collected from root surfaces of 10 control subjects with no RC and from 11 subjects with RC. The bacterial 16S rRNA genes from extracted DNA were PCR amplified, cloned, and sequenced to determine species identity. From a total of 3,544 clones, 245 predominant species or phylotypes were observed, representing eight bacterial phyla. The majority (54%) of the species detected have not yet been cultivated. Species of Selenomonas and Veillonella were common in all samples. The healthy microbiota included Fusobacterium nucleatum subsp. polymorphum , Leptotrichia spp., Selenomonas noxia , Streptococcus ...
In this study, an unusual observation of Saccharomyces cerevisiae isolated from an infected root ... more In this study, an unusual observation of Saccharomyces cerevisiae isolated from an infected root canal and from the blood of a patient undergoing endodontic therapy of a tooth with asymptomatic apical periodontitis is reported. Phenotypic (biochemical tests, antifungal susceptibility tests and SDS-PAGE of cellular proteins) and genetic (ribotyping) methods were used to characterize the strains. By using these methods it was found that the blood and root canal isolates were identical but differed from S. cerevisiae strains of other sources. It was therefore more than likely that the root canal was the source of the blood isolate and that it had been transferred unintentionally to the bloodstream during root canal treatment.
This study compared the sonic sensitivity of 12 Gram-negative and two Gram-positive bacteria comm... more This study compared the sonic sensitivity of 12 Gram-negative and two Gram-positive bacteria commonly encountered in plaque associated with periodontal diseases. Pure bacterial cultures were grown to standard turbidity, diluted in 1/4 strength prereduced anaerobically sterilized Ringer's solution, and aliquots dispersed for 0-180 s, using an MSE sonic oscillator at 6 micron under 80% N2, 10% H2 and 10% CO2. Viable recoveries were determined on anaerobically cultured trypticase soy 5% blood agar plates. Breakage of T. denticola was assessed by electron microscopy. Gram-positive organisms tolerated sonication better than Gram-negative. A. viscous was more resistant than Strep sanguis. Gram-negative bacteria could be divided into groups according to their sensitivity. Eikenella corrodens was most resistant, followed by F. nucleatum B asaccharolyticus, Capnocytophaga gingivalis, A actinomycetemcomitans, a strain (2097) of Group IV Bacteroides, and B melaninogenicus ss intermedius resisted sonication better than "corroding' Bacteroides and oral Campylobacter. T. denticola, Selenomonas sputigena and Wolinella were most sensitive with viable counts which declined after sonication for 5-10 s. Recoveries from plaque taken from five patients with periodontal diseases increased with sonication time, reaching higher values for suprangingival than for subgingival samples.
The distribution patterns of 90Sr in five littermate, 8-day-old Wistar rats were studied by whole... more The distribution patterns of 90Sr in five littermate, 8-day-old Wistar rats were studied by whole body autoradiography. Rats were killed 15 min, 1, 4, 24, and 72 h after a single intraperitoneal injection of the isotope. Immediately after administration, 90Sr was distributed throughout most of the soft tissues of the body. The soft tissue deposits had practically disappeared after 4 h. In the hard tissues of the body 90Sr accumulated up to 24-72 h. Fifteen minutes after injection the uptake of 90Sr in the enamel of the teeth was highest in the occlusal and incisal regions. 90Sr gradually accumulated throughout the enamel and after 72 h its distribution in this layer was fairly uniform. Immediately after injection a narrow zone of radioactivity appeared in the dentin near the pulp. This zone broadened with time towards the dentinoenamel junction and included the entire dentin layer 72 h after injection. Initially, the uptake of 90Sr was higher in the dentin thatn in the enamel, particularly in the cervical areas of the crown. This difference became less apparent with time. There was good correlation between the uptake in teeth and bones, supporting the use of teeth as indicators of the 90Sr body burden.
An experimental model of yeast-induced denture stomatitis has been set up in the rat by inoculati... more An experimental model of yeast-induced denture stomatitis has been set up in the rat by inoculating Candida albicans on the fitting side of a maxillary acrylic plate retained by an orthodontic band around the incisors. Thirty-eight Wistar rats were used in two series of experiments with an observation period of 2 weeks. In each of the series there were one control and three experimental groups. Control rats were left untreated, while rats of the experimental groups wore either uninoculated or inoculated plates, or had their palatal mucosa smeared with the yeast. For cytologic examination the palate was scraped in Series I and the fitting side of the plate in Series II. After 1 week a generalized simple inflammation had developed in the palate of most animals of the experimental groups. It was most severe and persistent in rats with inoculated plates. Histologic signs of inflammation and hyphal formation were also most pronounced in this group. Hyphae did not invade the epithelium. Except for an initial loss of body weight, which was restored by day 10 or 12, the rats tolerated their plates. The Wistar rat seems to be well suited for experimental studies on denture stomatitis.
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