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PubMed2000

Post-pH effect in oral streptococci.

OBJECTIVES: To study the post-pH effect (PpHE) in 11 strains of oral streptococci belonging to Streptococcus sanguis, S. mitis, S. gordonii, S. mutans and S. sobrinus by using the BacT/Alert microbial detection system. METHODS: The bacterial cultures were exposed to a different pH (3.6, 4.0, 4.6, 5.0, 5.6, 7.0, 7.5, 8.0 and 8.6) for 1 h, and then returned to a neutral medium. The automated BacT/Alert system determined resumed microbial growth by measuring CO2 generation. The PpHE expresses the time difference between resumed growth (after pH shock) and optimal growth (pH 7.0 used as the control). RESULTS: PpHE was found to be minimal for alkaline pH values, and to be strain and species dependent. CONCLUSIONS: The PpHE may be useful as an ecological determinant or as an indicator of the cariogenicity of oral streptococci.

Carbon Dioxide↗

PubMed1983

Prevalence of Streptococcus mutans with different colonial morphologies in human plaque and saliva.

Plaque and saliva samples were obtained twice from 58 children at an interval of 1 year and examined for the prevalence of Streptococcus mutans on Mitis salivarius (MS) and Mitis salivarius bacitracin (MSB) agar. Two types of S. mutans colonies with different colonial morphologies were seen on both media. They were serologically identified as serotypes c/e/f and d/g respectively. The first type, morphogroup c/e/f, had the typical "frosted-glass" appearance. It was the most prevalent and was found in 97% of the children. The second type, morphogroup d/g, had a creamy marzipan consistency with a dull, granular surface, gray to brown in color and often with some liquid around or on top of the colony. Group d/g was detected in 21 children (36%) and then together with colonies of group c/e/f. Children infected with single or multiple morphogroups of S. mutans generally harbored the same groups 1 year later. There was a significant positive correlation between the proportion of S. mutans in plaque and their numbers in saliva.

Adolescent↗

PubMed1992

Dental caries and its determinants among recent immigrants from rural Ethiopia.

Adults (35-45 yr old) and children (5 and 12 yr old) recently arrived in Israel from rural areas in Ethiopia were examined. Caries levels were low: e.g. DMFT = 0.31 among 12-yr-olds, and 1.27 amongst adults. The 5-yr-olds were 86.8% caries-free, while 12-yr-olds were 81.8% and adults 54% caries-free respectively. According to interview data, the diet in Ethiopia had been based on local agricultural products and was almost sugar-free. The mean total count of salivary bacteria, as determined on blood agar, was 3.4 x 10(8); mean count of Streptococcus viridans, on mitis salivarius, was 6.7 x 10(7); and mean count of S. mutans, as determined on mitis salivarius with bacitracin, was 1.7 x 10(7). These levels were all high and were not significantly different from a control group of 20 Israelis. The mean number of lactobacilli, on Rogosa agar, was 2.75 x 10(4), which was significantly higher than among the controls (3.6 x 10(3). Salivary pH levels were generally similar between the Ethiopian group and the controls. Salivary flow was significantly higher for the Ethiopians (1.93 ml/min) than for controls (1.16 ml/min). Low levels of caries in this population can be attributed to an almost sugar-free diet and high salivary flow, but not to the composition of oral microflora.

Adult↗

PubMed2000

The formation of mixed culture biofilms of oral species along a gradient of shear stress.

A chemostat mixed culture system was used to produce two distinct ecological states, state-1 (caries-like microcosm) and state-2 (periodontal-like microcosm). Eleven bacterial species (Streptococcus gordonii, Strep. mitis I, Strep. mutans, Strep. oralis, Actinomyces naeslundii, Lactobacillus casei, Neisseria subflava, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella nigrescens, Veillonella dispar) were used to inoculate the planktonic system. A flow cell, designed to produce convergent flow with increasing shear stress, was attached to the chemostat system, and the resultant biofilms developed from the state-1 and state-2 microcosms along the shear stress gradient were examined and compared using image analysis and viable counts. The biofilm produced from state-1 showed a lower shear stress tolerance (0.146 Pa) than the state-2 biofilm (0.236 Pa). The biofilm compositions did not vary along the gradient of shear stress and were dependent on the initial inoculum conditions. Gram-positive species were predominant in the state-1 biofilm, while Gram-negative species were predominant in state-2.

Actinomyces↗

PubMed1983

Comparative hydrophobicities of oral bacteria and their adherence to salivary pellicles.

Oral bacteria were found to differ in their surface hydrophobicities as determined by their ability to adsorb to hexadecane. Strains of Actinomyces viscosus, A. naeslundii, Streptococcus sanguis, S. mitis, and Bacteroides gingivalis proved highly hydrophobic. Strains of B. intermedius, S. salivarius, S. mutans, and B. melaninogenicus were less hydrophobic, whereas strains of Actinobacillus actinomycetemcomitans were hydrophilic. An overall correlation was noted between the adsorption of bacteria to hexadecane and their numbers which attached to experimental salivary pellicles formed on hydroxyapatite surfaces. This suggests that hydrophobic bonding plays an important role in this process. Pellicles prepared from saliva which had been extracted with chloroform-methanol to remove lipids adsorbed comparable numbers of S. sanguis and A. viscosus and increased numbers of S. mutans. Analyses of adsorption isotherms indicated that pellicles formed from lipid-depleted saliva contained increased numbers of binding sites for the S. mutans strains studied, and this likely accounts for their enhanced adsorption. Absorption of saliva with 10% octyl or phenyl Sepharose reduced the protein content of saliva by almost half, but the numbers of bacteria which attached to pellicles prepared from such absorbed saliva were similar to or higher than those which attached to control pellicles. These observations suggest that saliva does not contain unique highly hydrophobic salivary macromolecules which serve as essential pellicle receptors for the bacteria studied. The data obtained are consistent with the view that hydrophobic bonding together with interactions between complementary molecules are involved in bacterial attachment to salivary pellicles on teeth.

Adsorption↗

PubMedDate not supplied

[Oral cavity microbial coenobia in healthy children and children with chronic recurrent aphthous stomatitis].

Peculiarities of quantitative and qualitative composition of microbiocenosis of the oral cavity in healthy children and children with chronic aphthous recurrent stomatitis have been studied. Strains of microorganisms (n = 259) have been isolated and identified. The results obtained showed that the studied biotope is characterised by a wide spectrum of isolated microflora. The growth of microorganism association is observed in all the studied samples. The analysis of genus and species composition of microbiocenosis of the mucous membrane indicated that streptococci, neiserii, corynebacteria, enterococci, lactobacilli, epidermal staphylococci and candidas were distinguished as to isolation frequency among the isolated strains. These bacteria were isolated from oral cavity of healthy and sick children, but their quantity in 1 mm2 of sick children mucosa prevailed, except for Streptococcus salivarius, S. mitis and Lactobacillus sp.: their quantity was far less. Golden staphylococci, escherichia, klebsiella, clostridia, hemophilic rods and campylobacteria were isolated from sick children only.

Adolescent↗

PubMed2006

Characteristic signatures of the lytA gene provide a basis for rapid and reliable diagnosis of Streptococcus pneumoniae infections.

The nucleotide sequences of the lytA gene from 29 pneumococcal isolates of various serotypes and 22 additional streptococci of the mitis group (including two Streptococcus pseudopneumoniae strains) have been compared and found to correspond to 19 typical (927-bp-long) and 20 atypical (921-bp-long) alleles. All the Streptococcus pneumoniae strains harbored typical lytA alleles, whereas nonpneumococcal isolates belonging to the mitis group always carried atypical alleles. A sequence alignment showed that the main difference between typical and atypical lytA alleles resided in 102 nucleotide positions (including the 6 bp absent from atypical alleles). These nucleotides were perfectly conserved in all the typical alleles studied, and the corresponding nucleotides of the atypical alleles were also perfectly conserved. The presence in these signatures of distinctive restriction sites (namely, SnaBI, XmnI, and BsaAI) allowed the development of a simple, reliable, and fast method that combines PCR amplification of the lytA gene, digestion with BsaAI, and separation of the products by agarose gel electrophoresis. This assay allows the rapid and consistent identification of true S. pneumoniae strains and represents an improved diagnostic tool for the study of pneumococcal carriage.

Alleles↗

PubMed2004

Oral streptococci exhibit diverse susceptibility to human beta-defensin-2: antimicrobial effects of hBD-2 on oral streptococci.

We examined the antimicrobial effects of human beta-defensin-2 (hBD-2) on 17 species of oral streptococci to investigate the involvement of antimicrobial peptide activity in oral microflora development and the clinical use of the antimicrobial peptide for oral microflora control. Oral streptococci exhibit diverse levels of susceptibility to human beta-defensin-2 (hBD-2). Two major cariogenic bacterial species, Streptococcus mutans ( S. mutans) and S. sobrinus, were found to be susceptible to the peptide, indicating that it is a potential therapeutic agent for preventing dental caries. S. mitis exhibited the lowest susceptibility to the peptide. S. mitis is a major indigenous bacterium in the oral microflora, and our results suggest that it might possess a certain resistance mechanism against hBD-2.

Anti-Infective Agents↗

PubMed2006

Viridans streptococci isolated by culture from blood of cancer patients: clinical and microbiologic analysis of 50 cases.

Clinical and microbiologic studies of 50 cases of viridans streptococcal bacteremia in cancer patients were performed. The bacteria were identified to species level by sequencing analysis of the 16S rRNA gene. At least nine Streptococcus spp. were found, including S. mitis (25 strains, 50.0% of 50); currently unnamed Streptococcus spp. (11 strains); S. parasanguis (five strains); S. anginosus (three strains); S. salivarius (two strains); and one strain each of S. gordonii, S. sanguis, S. sobrinus, and S. vestibularis. There were no S. oralis strains. Among 11 antibiotics of nine classes tested, no resistance to vancomycin, linezolid, or quinupristin-dalfopristin was seen. Resistance to penicillin (MIC, 4 to 12 mug/ml) was noted only among S. mitis strains (28.0%, 7/25) and not non-S. mitis strains (0/25) (P = 0.004). Significantly more S. mitis strains than non-S. mitis strains were resistant to fluoroquinolones and to > or =3 classes of antibiotics. Isolation of quinolone-resistant organisms was associated with the prior usage of quinolones (P = 0.002). Quantitative blood cultures showed that the strains resistant to levofloxacin or gatifloxacin were associated with higher colony counts than were their corresponding nonresistant strains. The young and elderly patients also had higher levels of bacteremia caused predominantly by S. mitis. Septic shock was present in 17 (34.0% of 50) patients, and 13 of those cases were caused by S. mitis (P = 0.007). These results suggest that S. mitis is the most common cause of viridans streptococcal bacteremia in cancer patients and is more resistant to antibiotics than other species.

Anti-Bacterial Agents↗

PubMed1989

Differentiation of Listeria and Streptococcus strains.

Colonial morphology of non-beta haemolytic Listeria strains is frequently similar to that of non-haemolytic streptococci. Biochemical characteristics, motility, haemolysis on ox blood agar, growth on Clauberg, selective streptococcus (Si) and Mitis-Salivarius agar medium, CAMP test, serological behaviour of 16 Listeria strains were studied and the results were compared with the properties of Streptococcus strains. Microscopic morphology, motility and catalase activity are useful for distinguishing these strains. To avoid a false diagnosis, latex-agglutination should be supplemented with the above tests.

Listeria↗

PubMed2000

Genotypic heterogeneity of Streptococcus oralis and distinct aciduric subpopulations in human dental plaque.

The genotypic heterogeneity of Streptococcus oralis isolated from the oral cavity was investigated using repetitive extragenic palindromic PCR. Unrelated subjects harbored unique genotypes, with numerous genotypes being isolated from an individual. S. oralis is the predominant aciduric bacterium isolated from noncarious tooth sites. Genotypic comparison of the aciduric populations isolated at pH 5.2 with those isolated from mitis-salivarius agar (MSA) (pH 7.0) indicated that the aciduric populations were genotypically distinct in the majority of subjects (chi(2) = 13.09; P = 0.0031). Neither the aciduric nor the MSA-isolated strains were stable, with no strains isolated at baseline being isolated 4 or 12 weeks later in the majority of subjects. The basis of this instability is unknown but is similar to that reported for Streptococcus mitis. Examination of S. oralis strains isolated from cohabiting couples demonstrated that in three of five couples, genotypically identical strains were isolated from both partners and this was confirmed by using Salmonella enteritidis repetitive element PCR and enterobacterial PCR typing. These data provide further evidence of the physiological and genotypic heterogeneity of non-mutans streptococci. The demonstration of distinct aciduric populations of S. oralis implies that the role of these and other non-mutans streptococci in the caries process requires reevaluation.

Dental Plaque↗

PubMed1979

Specificity of coaggregation reactions between human oral streptococci and strains of Actinomyces viscosus or Actinomyces naeslundii.

Coaggregation reactions between actinomycete and streptococcal cells occurred frequently when human strains of Actinomyces viscosus or A. naeslundii were mixed with human isolates of Streptococcus sanguis or S. mitis, but were infrequent with other oral actinomycetes and streptococci. Two groups of actinomycetes and four groups of streptococci were defined by the patterns of their coaggregation reactions and by the ability of beta-linked galactosides (i.e., lactose) to reverse these reactions. Coaggregations occurred by one of the following three kinds to cell-cell interactions: (i) coaggregation that was blocked by heating the streptococcus but not the actinomycete and was not reversed by lactose; (ii) coaggregation that was blocked by heating the actinomycete but not the streptococcus and was reversed by lactose; and (iii) coaggregation that was blocked only by heating both cell types. The latter reaction was a combination of the first two since lactose reversed coaggregation between heated streptococci and unheated actinomycetes but did not reverse coaggregations between unheated streptococci and heated actinomycetes. Cells that could be heat inactivated also were inactivated by amino group acetylation or protease digestion, whereas cells that were unaffected by heat were not inactivated by these treatments. Coaggregation reactions of each kind were Ca2+ dependent and insensitive to dextranase treatment. These findings are consistent with the hypothesis that human strains of A. viscosus and A. naeslundii coaggregate with strains of S. sanguis and S. mitis by a system of specific cell surface interactions between protein or glycoprotein receptors on one cell type and carbohydrates on the other type.

Acetylation↗

PubMed1998

Effect of an alum-containing mouthrinse in children for plaque and salivary levels of selected oral microflora.

The purpose of the study was to assess the effect of daily supervised rinsing with a specially formulated, alum-containing mouthrinse on plaque and salivary levels of S. mutans, S. mitis and S. salivarius in caries susceptible children (12-14 years old) and to monitor the effect on the oral tissues and acceptability to subjects. Forty-five subjects were divided into 3 groups (n = 15). Group I received an experimental group with a mouthrinse containing hydrated aluminum potassium sulfate (alum). Group 2 received a vehicle control group containing the same mouthrinse, but without alum and Group 3 had a treatment control with distilled water. All subjects continued normal oral hygiene habits during the study. Salivary and plaque levels were obtained at base line, 2 weeks and 4 weeks and evaluated for microbiologic procedures. Also, potential adverse effects on oral tissues were performed during every visit. The mean plaque and salivary levels of oral Streptococcus (S. mutans, S. mitis, S. salivarius) for the experimental group were significantly reduced after 2 weeks and 4 weeks compared with baseline. The plaque and salivary levels of oral Streptococcus of experimental and vehicle control group differed statistically from each other after 4 weeks, with the strongest reduction in the experimental group and there was statistically difference between treatment control and vehicle control or experimental groups at each time interval. No evidence of deleterious effects to the oral tissues was observed. Daily use of an alum-containing mouthrinse was safe and produced significant reduction effect on plaque and salivary levels of oral Streptococcus and can be used in children for the preventive dentistry.

Adolescent↗

PubMed1996

Emergence of high rates of antimicrobial resistance among viridans group streptococci in the United States.

Three hundred fifty-two blood culture isolates of viridans group streptococci obtained from 43 U.S. medical centers during 1993 and 1994 were characterized. Included were 48 isolates of "Streptococcus milleri," 219 S. mitis isolates, 29 S. salivarius isolates, and 56 S. sanguis isolates. High-level penicillin resistance (MIC, > or = 4.0 micrograms/ml) was noted among 13.4% of the strains; for 42.9% of the strains, penicillin MICs were 0.25 to 2.0 micrograms/ml (i.e., intermediate resistance). In general, amoxicillin was slightly more active than penicillin. The rank order of activity for five cephalosporins versus viridans group streptococci was cefpodoxime = ceftriaxone > cefprozil = cefuroxime >> cephalexin. The percentages of isolates resistant (MIC, > or = 2 micrograms/ml) to these agents were 15, 17, 18, 20, and 96, respectively. The rates of resistance to erythromycin, tetracycline, and trimethoprim-sulfamethoxazole were 12 to 38%. Resistance to either chloramphenicol or ofloxacin was uncommon (i.e., < 1%). In general, among the four species, S. mitis was the most resistant and "S. milleri" was the most susceptible.

Anti-Bacterial Agents↗

PubMed1990

Predominance of resistant oral streptococci in saliva and the effect of a single course of josamycin or erythromycin.

We have investigated the influence of the macrolides erythromycin and josamycin on the selection of resistant oral streptococci by sampling saliva of volunteers before and after oral administration of 1.5 g of either agent followed by a further 0.5 g of the same drug after 6 h, as in routine prophylaxis for oral or dental procedures. The small proportion of resistant organisms present before antibiotic administration increased substantially 48 h after the macrolides were given. After antibiotic administration mean counts of oral streptococci resistant to 1, 4 and 64 mg/l erythromycin were 23%, 17% and 6%, respectively, of the total numbers of streptococci isolated; after josamycin, the values were 13%, 6% and 4% respectively. The proportion of resistant streptococci then declined gradually but remained above pre-antibiotic levels three months later. Streptococci isolated on media containing 64 mg/l of macrolides were mainly Streptococcus sanguis and S. mitis with one isolate of S. salivarius; the majority were resistant to 256 mg/l erythromycin, josamycin, all other macrolides tested and clindamycin. Amoxycillin and pristinamycin were the only compounds tested that were inhibitory to these organisms at therapeutically attainable concentrations.

Adolescent↗

PubMed1972

Saliva-induced aggregation of oral streptococci.

Cells of several species of oral microorganisms have been shown, in earlier studies, to be aggregated by saliva. In the present study some of the basic properties of the aggregation system are examined. The observation is made that the saliva-induced aggregates of Streptococcus sanguis and S. mitis can be dissociated to stable particles which consist of about 100 cells and have a median diameter of about 4.5 mum. It is proposed that these are subunits, or core aggregates, of the large primary aggregates. Counts of the core aggregates can be taken as a precise and accurate measure of aggregation. Experiments based on this procedure show that the aggregation of S. sanguis is maximal at 10 C and at 1 meq of Ca(2+) ions per liter and is not affected by a change in pH between 3.9 and 8.7 or by a change in the phase of growth of the microorganisms. Core aggregates diminish in number with prolonged incubation, suggesting that the aggregating factors break down with time. Formalinized cells yield stable aggregates. However, with Formalinized cell aggregation is maximal between 20 and 30 C and proceeds in the absence of calcium ions. Evidence is presented that whole saliva contains separate aggregating factors for S. sanguis and S. mitis. The factors differ in their affinity for intact cells and for hydroxyapatite and differ in their stability to dialysis. These findings suggest that many different aggregating factors exist in saliva, each of which may be capable of interacting with cells of one or several bacterial species.

Adsorption↗

PubMed1997

Antimicrobial susceptibility of viridans group streptococci.

A total of 68 viridans group streptococci, including 31 Streptococcus sanguis, 12 S. mitis, 3 S. salivarius, and 8 S. milleri from blood, and an additional 14 S. milleri from abscesses and normally sterile sites, were tested against penicillin, amoxicillin, cefazolin, ceftriaxone, meropenem, clindamycin, quinupristin/dalfopristin, rifampin, levofloxacin, ofloxacin, vancomycin, and gentamicin with the microdilution method. The susceptibility rates for S. sanguis were: penicillin, 74%; amoxicillin, 84%; ceftriaxone, 94%; clindamycin, 87%, and vancomycin, 100%. The susceptibility rates for S. mitis were: penicillin, 42%; amoxicillin, 67%; ceftriaxone, 58%; clindamycin, 100%; and vancomycin, 100%. The susceptibility rates for S. milleri were: penicillin, 100%, amoxicillin. 100%; ceftriaxone, 100%, clindamycin, 100%; and vancomycin, 100%. Two of the three isolates of S. salivarius were susceptible to penicillin, amoxicillin, and ceftriaxone; all were susceptible to clindamycin and vancomycin. Levofloxacin, quinupristin/dalfopristin, and rifampin were highly active against all isolates.

Amoxicillin↗

PubMed2000

Serious streptococcal infections produced by isolates resistant to streptogramins (quinupristin/dalfopristin): case reports from the SENTRY antimicrobial surveillance program.

The emergence and sustained prevalence of Gram-positive organisms resistant to antimicrobials has been of interest for over a decade. Quinupristin/dalfopristin (formerly RP 59500 or Synercid) is a new injectable streptogramin combination that has been reported to have activity against Gram-positive organisms, even those with documented MLS(B) resistance. However, the two case reports presented here illustrate three well-documented Streptococcus spp. strains (S. mitis, S. pneumoniae) to be resistant to quinupristin/dalfopristin (MICs at 3, 8, and 12 microg/ml) following referral as routine isolates in the SENTRY Antimicrobial Surveillance Program. The S. pneumoniae pleural fluid isolate was cross-resistant to erythromycin. Both bacteremic S. mitis strains were resistant to macrolides (erythromycin, azithromycin, clarithromycin), lincosamides (clindamycin), and fluoroquinolones. Patient histories indicated no prior use of MLS class antimicrobials for the S. mitis case, but the patient having the S. pneumoniae isolate did receive prior treatment of erythromycin and clindamycin. All isolates had modestly increased penicillin MICs of 0.12 microg/ml. The mode of resistance to quinupristin/dalfopristin was not evident (sat A-negative by PCR); and these cases illustrate the existence of streptogramin-resistant isolates before the introduction of this antimicrobial class into human clinical practice.

Adult↗