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Biomedical subjects

S Edwardsson

Publications and source records attributed to S Edwardsson.

At least 55 records · Page 3Linked to original sources
PubMed1990

Effect of pH on acid production from sorbitol in washed cell suspensions of oral bacteria.

The acid production from sorbitol and glucose was studied under anaerobic conditions in resting cell suspensions of bacteria from the predominant sorbitol-fermenting human dental plaque flora, belonging to the genera Streptococcus, Lactobacillus and Actinomyces. The acid production activity of the bacterial cells was followed by titration with alkali, at environmental pH 7.0, 6.0 and 5.0 after addition of carbohydrate solution. The metabolic end products formed in the suspensions were analyzed thereafter by isotachophoretic and enzymatic methods. The results showed that sorbitol was fermented at a slower rate than glucose. Lowering the environmental pH decreased the acid production activity from the two carbohydrates. Compared with glucose, the catabolism of sorbitol was affected to greater extent by the pH conditions. The total amount of acids formed from sorbitol was considerably less than from glucose. Lactic acid, which was the major end product in glucose-challenged suspensions, was produced only in low concentrations from sorbitol by all strains tested. The ratio strong (formic + lactic)/weak acids was moreover lower for sorbitol than for glucose. The present results further illustrate some of the mechanisms behind the low cariogenic potential of this sugar substitute.

Acetates↗
PubMed1990

Sorbitol adaptation of dental plaque in people with low and normal salivary-secretion rates.

Caries-related bacteriological and biochemical factors were studied in 12 persons with low and 11 persons with normal salivary-secretion rates before and after a four-week period of frequent mouthrinses with 10% sorbitol solution (adaptation period). After the adaptation period, an increase in total numbers of sorbitol-fermenting bacteria and mutans streptococci was found in plaque samples from both groups. The pH drop in dental plaque in situ after a mouthrinse with sorbitol was more pronounced after the adaptation period, especially in the group with the low salivary-secretion rate. Increased acid production in plaque from sorbitol was also observed in the two groups in vitro. The composition of the fermentation end-products was affected by the sorbitol exposure. It is suggested that in subjects with diminished natural protection against caries development, such as patients with low salivary-secretion rate, a cariogenic potential of sorbitol should be considered when this polyol is included in products that might be used frequently.

Adaptation, Physiological↗
PubMed1990

Effect of culture medium on acid production from sorbitol by oral bacteria.

The fermentation of sorbitol or glucose and the acid production by strains belonging to the genera Actinomyces, Lactobacillus, and Streptococcus isolated from the predominant sorbitol-fermenting human dental plaque flora were studied in cultures in complex or defined bacteriologic broths and in saliva-based broth. The growth yields of Lactobacillus and Streptococcus in the saliva-based media and of Actinomyces in the defined broth were poor. Addition of fermentable carbohydrate to the saliva-based broth favored the growth of Streptococcus and Lactobacillus but not that of Actinomyces. The results showed obvious differences in the capacity of oral bacteria to ferment sorbitol between cultures in saliva-based and bacteriologic broths. Lactobacillus failed to utilize sorbitol when saliva was the only source of nutrients. Lower proportions of lactic and formic acids were formed from sorbitol by Actinomyces and Lactobacillus in the saliva-based than in the bacteriologic media. The findings illustrate some mechanisms possibly involved in the interactions between sorbitol and dental plaque flora.

Actinomyces↗
PubMed1988

Effects of cations on the colloidal stability of some oral bacteria.

The colloidal stability of seven strains of oral bacteria was studied at various concentrations of mono-, di-, and multi-valent metal counterions in the suspending media. Alterations in the concentration and the valency of the counterions were shown to influence the colloidal stability of the bacterial suspensions, as determined by their rate and time of initial sedimentation. The observations were in general in agreement with the accepted theories for colloidal stability. The results support previously made suggestions that under certain experimental conditions oral bacteria behave like colloidal particles.

Actinomyces↗
PubMed1988

Influence of pH on the suspension stability of some oral bacteria.

The purpose of the present study was to investigate the suspension stability of some oral bacteria at some clinically relevant pH levels. Through determinations of the electrophoretic mobility and sedimentation behavior at pH 5, 6, and 7, it was shown that within this pH range estimations of both the zeta-potentials and colloidal stability were pH-dependent for the bacteria and bacterial suspensions tested. The observations are in line with the DLVO theory for lyophobic sols and indicate that bacteria behave like colloidal particles when suspended in certain media. The colloidal behavior further seemed to vary in relation to bacterial species and strains.

Actinomyces↗
PubMed1987

Dietary habits, gingival status and occurrence of Streptococcus mutans and lactobacilli as predictors of caries in 3-year-olds in Sweden.

The aim was to study whether dietary habits, oral hygiene expressed as gingival status, and presence/absence of S. mutans and lactobacilli, singly or in combinations, could be used as caries predictors. Sensitivity, specificity and predictive values for positive (PV+) and negative tests (PV-) were calculated. 133 children, 3 yr of age, were examined for caries and presence/absence of S. mutans and lactobacilli. Three levels of gingival status and dietary habits, respectively, were registered. Two groups in respect of dietary habits and oral hygiene were formed by stepwise pooling of the caries data for the nine possible combinations of oral hygiene and dietary habits, setting the most discriminating border (screening level) where sensitivity (0.86) and specificity (0.69) simultaneously reached their highest value. PV + was 0.58 and PV- 0.91. Higher predictive values were obtained when presence/absence of lactobacilli and of S. mutans were combined. Combinations of defined levels of dietary habits, gingival status and presence/absence of lactobacilli showed sensitivity 0.87, specificity 0.95, PV + 0.87 and PV- 0.95, presence/absence of S. mutans sensitivity 0.94, specificity 0.76, PV + 0.74 and PV- 0.95. A two-step prediction, with gingival status as the first predictor and presence/absence of lactobacilli or S. mutans as the second, was the most efficient when lactobacilli were involved.

Child, Preschool↗
PubMed1987

Improved selective culture media for Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus.

By modifying the previously described media tryptic soy-serum-bacitracin-vancomycin (TSBV) agar and tryptic soy-serum-bacitracin-vancomycin-fluoride (TSBVF) agar, two improved selective culture media were developed for isolation and enumeration of Actinobacillus actinomycetemcomitans (A medium) and Haemophilus aphrophilus (H medium) in oral specimens. Both media were supplemented with fusidic acid and spiramycin, and carbenicillin was also added to A medium. The growth yields of pure cultures of A. actinomycetemcomitans on A medium and of H. aphrophilus on H medium were comparable with those on the reference media. Compared with blood agar, the selective media inhibited these species about 10-fold or less. In addition, A and H media suppressed the growth of pure cultures of Capnocytophaga spp. and Neisseria spp., commonly found as contaminants on TSBV and TSBVF, 10(5) times or more compared with that on blood agar. In samples from diseased periodontal pockets, the recoveries of A. actinomycetemcomitans on A medium and H. aphrophilus on H medium equaled those on TSBV and TSBVF, respectively. In about 50% of the cultures on the reference media, contaminating bacteria were detected at levels higher than 10(4) CFU/ml of sample. The corresponding value for both A and H media was about 2%.

Actinobacillus↗
PubMed1987

Biophysical and microbiologic studies of "heavy" and "light" plaque formers.

In order to trace factors possibly influencing initial bacterial colonization of tooth surfaces, a multiple linear regression analysis was performed on the present results as well as on those from certain clinical and biochemical studies previously performed in the same subjects. No statistically significant differences were observed between the two groups of plaque formers for the individual parameters. The multiple regression analysis showed, however, that the calculated work of adhesion for two polar and one non polar test liquid, the rate of unstimulated salivary secretion, morphologic differences in the dento-gingival areas of maxillary premolars and saliva-induced aggregation of S. mitior were crucial for about 90% of the variation in the number of CFU colonizing tooth surfaces after both 2 and 6 h. Both electrostatic and van der Waal's forces, as well as salivary flow conditions could thus have influenced the initial attachment of bacteria to the test surfaces. It is concluded that saliva including its suspended microorganisms could be looked upon as being a colloidal biological system, and if so, the initial bacterial colonization of tooth surfaces should follow known, general biophysical laws.

Adhesiveness↗
PubMed1985

Evaluation of a simplified diagnostic aid (Oricult-N) for detection of oral candidoses.

The validity of a simplified diagnostic aid, Oricult-N, for detection of oral candidoses was compared with smears stained according to the periodic acid-Schiff's method. Samples were taken from 80 locations in 36 patients with lesions suspected for candidal infection. There was a statistically significant correlation between the two methods (P less than 0.001).

Adult↗
PubMed1985

Effect of repeated intake of a sugar free fluoride-containing chewing gum on acidogenicity and microbial composition of dental plaque.

In a double blind cross-over study, 20 subjects were given either a sugar free chewing gum containing 0.25 mg fluoride or the same chewing gum without fluoride, eight times a day for 7 days. The pH of 3-day-old plaque was determined before and after each experimental period following a 30-s mouth-rinse with 10 ml 15% sucrose. The pH-decrease was significantly less pronounced after using the fluoride gum than after the placebo gum (P less than 0.001). In a second study, 20 subjects participated in a similar study. In this experiment the acid production activity from sucrose in dental plaque in vitro was determined with the aid of a titration method. In addition, the dental plaque wet weight and the total number of cultivable organisms, Streptococcus mutans and lactobacilli, expressed as the number of colonies per mg plaque, were determined. No significant effect was found on any of these parameters after using the fluoride gum compared to the placebo gum. Thus, the results indicate that slightly elevated levels of fluoride in saliva during daytime, achieved by repeated intake of fluoride gums for 7 days, are sufficient to influence the acidogenicity of dental plaque in vivo.

Chewing Gum↗
PubMed1985

Agar media that indicate acid production from sorbitol by oral microorganisms.

Two varieties of agar medium (Trypticase [BBL Microbiology Systems]-serum-sorbitol-bromcresol purple agar [TSSB] and Trypticase-blood-sorbitol-CaCO3 agar [TBSCa]) indicating microbial acid production from sorbitol were tested. The media were devised for use in studies on the prevalence of sorbitol-fermenting human oral microorganisms incubated in an anaerobic or microaerophilic atmosphere containing 5 to 6% CO2. TSSB contains bromcresol purple as the pH indicator and NaHCO3 as the main buffering salt. TBSCa contains CaCO3 as both the buffering salt and the indicator of acid production. The growth yield of pure cultures of oral microorganisms on TBSCa was shown to equal that on blood agar incubated under similar conditions. TSSB inhibited the growth of several bacteria to various extents. The recovery of sorbitol-fermenting microorganisms from oral specimens was the greatest when the specimens were assayed with TBSCa. The poorer results obtained with TSSB were mainly due to the decoloration of the pH indicator in this medium and the presence of greater numbers of sorbitol false-positive colonies.

Acids↗
PubMed1985

Anaerobic and aerobic metabolism of sorbitol in Streptococcus sanguis and Streptococcus mitior.

Sorbitol-fermenting strains of Streptococcus sanguis and Streptococcus mitior were grown both anaerobically and in the presence of oxygen in a sorbitol-containing complex medium. Washed-cell suspensions were incubated with an excess of sorbitol, and the production of lactate, formate, ethanol, and acetate was analyzed. Moreover, we determined the lactate dehydrogenase and pyruvate formate-lyase activities in cell-free extracts of anaerobically grown cells. The anaerobically grown cells produced lactate, formate, ethanol, and acetate under anaerobic conditions. When these cells were exposed to air, the amounts of formate, ethanol, and acetate were reduced in comparison with those of the strictly anaerobic cells. Cells grown in the presence of oxygen only produced detectable levels of lactate and acetate. Anaerobically grown cells possessed lactate dehydrogenase and pyruvate formate-lyase activities under strictly anaerobic conditions. The level of pyruvate formate-lyase was dramatically reduced when cells were exposed to air, while the level of lactate dehydrogenase was about the same as that under strictly anaerobic conditions. Thus, the results indicate that S. sanguis and S. mitior both metabolize sorbitol differently under anaerobic and aerobic conditions. This difference may depend on the oxygen-sensitivity of the pyruvate formatelyase of these micro-organisms.

Acetates↗
PubMed1985

Microbiological aspects of some caloric sugar substitutes.

Several caloric sugar substitutes are available today, e.g. maltitol, Lycasin, sorbitol, xylitol, palatinit, sorbose, coupling sugar, palatinose, fructose and invert sugar. When evaluating the cariogenicity of these sugar substitutes from a bacteriological point of view, different analytical procedures should be considered. In vitro studies on the capacity of pure oral bacterial strains and dental plaque material to decompose the substitute to acid. Studies on the catabolism of the substitute. Possible adaptation of the oral microflora to metabolize the substitute in vivo as well as in vitro. Studies on any inhibitory effect of the substitute on the microbial activities in dental plaque and on the oral microflora. The capacity of oral bacteria, e.g. Streptococcus mutans, to induce caries in animal experiments should also be considered. Results from such microbiological studies make it possible to classify the caloric sugar substitutes into different groups. The first, most suitable, group seems to consist of xylitol and sorbose. These substitutes are fermented by few oral bacteria and no negative adaptation of the oral flora has been observed. A reducing effect upon dental plaque formation and on acid production from glucose has been reported. A second group consists of maltitol, palatinite, palatinose, sorbitol and Lycasin. These substitutes are fermented by certain groups of organisms within the oral genera Actinomyces, Lactobacillus and Streptococcus. Adaptation of oral bacteria to palatinose and to sorbitol, resulting in a more pronounced acid production, has been observed. No inhibitory effects have been reported. The results from experimental studies suggest that these sugar substitutes have no or little cariogenic action in rodents inoculated with S. mutans.(ABSTRACT TRUNCATED AT 250 WORDS)

Acids↗