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PubMed2000

The oral microbiota of children undergoing liver transplantation.

This study investigated the oral microbiota of children undergoing liver transplantation. Oral swabs were taken using a standardized procedure from 27 children before liver transplantation and at 3 and 100 days post-transplantation and from 27 healthy controls at baseline and 90 days. Viridans streptococci, yeasts, staphylococci, enterococci and Enterobacteriaceae were enumerated and identified using conventional techniques. The oral microbiota of the patients changed significantly immediately post-transplantation, but by the final examination, it had returned to baseline levels. The oral microbiota of the controls did not change significantly. The numbers and proportions of Streptococcus salivarius, Streptococcus sanguis and Streptococcus gordonii as percentages of the total streptococcal counts and of the total anaerobic counts decreased significantly 3 days post-transplantation (P < or = 0.006). There were no significant changes in the numbers and proportions of Streptococcus oralis and Streptococcus mitis isolated pre- and post-transplantation. The isolation frequencies and numbers of yeasts were significantly higher in patients than controls. Staphylococci were isolated in low numbers from all children. Enterococci and Enterobacteriaceae were isolated infrequently from patients.

Adolescent↗

PubMed2000

Streptococcal toxic shock in a horse.

A 14-year-old horse was admitted to the veterinary hospital for treatment of tachycardia and lethargy. Initial diagnoses were ventricular tachycardia and renal dysfunction. During hospitalization other findings included fever, renal failure, hepatic failure, hypotension, and intermittent ventricular arrhythmias. Bacteriologic culture of 2 blood samples collected during febrile crises 7 days apart yielded Streptococcus mitis. These culture results along with other clinical and physical examination findings fulfill the criteria for a diagnosis of streptococcal toxic shock syndrome, previously described for humans and dogs. To our knowledge this is the first reported instance of this disease in a horse.

Animals↗

PubMed1988

An in vitro model to study bacterial invasion of periodontal tissues.

In periodontal disease, the abilities of bacteria to adhere to and degrade in vivo basement membranes should be considered as two of the rate-limiting steps for the potential active or passive invasion of gingival connective tissues. To study these mechanisms in greater detail, we used the PF HR-9 basement-membrane-like matrix to establish an in vitro model of bacterial invasion and degradation. Three gram-negative anaerobic periodontopathic organisms, Bacteroides gingivalis, Fusobacterium nucleatum, and Actinobacillus actinomycetemcomitans, bound in considerably higher numbers to the HR-9 matrix than did 6 strains of gram-positive facultative organisms typically associated with periodontal health. In a further experiment with B. gingivalis, the organism rapidly degraded Type IV collagen, the major macromolecular component constituting the HR-9 matrix. Streptococcus mitis, the nonperiodontopathic bacterium tested, did not degrade this model matrix. This study provides evidence that B. gingivalis, a periodontopathic bacterium, is able to adhere to and degrade basement membranes, whereas nonperiodontopathic organisms appear not to share in these abilities.

Actinobacillus↗

PubMed1984

Growth and acid tolerance of human dental plaque bacteria.

Pure cultures of representative strains of cariogenic and non-cariogenic plaque bacteria were assessed for their ability to initiate and maintain growth in broths, adjusted to initial pH levels of 7.0, 5.5 or 5.0, and to produce lactic acid from sucrose or glucose in resting-cell suspensions at pH 6.5, 5.0, 4.5 and 4.0. Streptococcus mutans, Lactobacillus casei and Streptococcus faecalis showed greater acid tolerance than strains of Streptococcus sanguis, Streptococcus salivarius, Streptococcus mitis and Actinomyces viscosus. For all species, growth initiation in broth was more acid sensitive than lactic-acid production in resting-cell suspensions. These data confirm and extend previous observations that the species of plaque bacteria most closely associated with the initiation or progression of dental caries are more aciduric than non-cariogenic species.

Actinomyces↗

PubMed1983

Multiply resistant viridans streptococci: susceptibility to beta-lactam antibiotics and comparison of penicillin-binding protein patterns.

A unique group of viridans streptococci has been found in South Africa. These organisms were isolated in close temporal and physical proximity to the isolation of penicillin-resistant pneumococci. The strains were resistant to penicillin, oxacillin, the cephalosporins (all generations), piperacillin, azlocillin, and mezlocillin but were susceptible to vancomycin. Penicillin-binding proteins of two penicillin-resistant South African strains of Streptococcus mitis differed markedly from those of two penicillin-susceptible strains but were identical to those seen in a penicillin-resistant strain isolated in Boston. Although both susceptible strains were identified as S. mitis with identical biochemical profiles, their penicillin-binding protein patterns differed from each other. This finding may have significance with regard to the need for additional taxonomic classification of the viridans streptococci.

Anti-Bacterial Agents↗

PubMed1993

Synergistic activity of ceftriaxone combined with netilmicin administered once daily for treatment of experimental streptococcal endocarditis.

We have conducted experiments to determine if one daily injection of netilmicin (NET) would be synergistic with the broad-spectrum cephalosporin ceftriaxone (CRO) in the treatment of experimentally induced endocarditis. Rats with catheter-induced aortic vegetations were infected intravenously with 3 x 10(7) CFU of a beta-lactam-sensitive strain of Streptococcus sanguis or a beta-lactam-resistant strain of Streptococcus mitis. Treatment with the antibiotics alone (CRO, 10 mg/kg of body weight every 8 h; NET, 18 mg/kg every 24 h) or in combinations which had proved synergistic in in vitro time-kill curves was commenced 48 h postinfection and continued for 72 h. The results show that the combination was markedly effective against S. sanguis and moderately effective against S. mitis, while, with the protocol used here, the agents alone were not. The results suggest that CRO-NET should be an effective combination for treating streptococcal endocarditis in humans and may permit a shorter duration of treatment and once-a-day dosing to be used.

Animals↗

PubMed1992

Inhibition of microbial adherence by sphinganine.

Sphingosines (precursors and degeneration products of complex sphingolipids) are mediators in membrane second-messenger cascades and in a wide variety of functions in eukaryotic cells. Sphingosines are also lethal for gram-positive microorganisms. In addition to its direct effect, sphinganine is here reported to affect the adherence of Streptococcus mitis to buccal epithelial cells and of Staphylococcus aureus to nasal mucosal cells after incubation for 90 min at 37 degrees C. When the bacteria were pretreated with 8.1, 16.2, 32.5, or (for Strep. mitis) 65 microM sphinganine for 60 min at 37 degrees C, adherence counts were reduced for Staph. aureus by 27, 37, and 60% and for Strep. mitis by 19, 44, 54, and 73%, respectively (p < 0.001). In contrast, pretreatment of buccal cells with 81.2 microM lipid increased adherence by 14% (p < 0.01), but no change occurred at either 16.2 or 325 microM lipid. These results further demonstrate the double-edged ability of sphingosines to regulate cellular activities and their potential as multifunctional therapeutic agents for infectious diseases.

Bacterial Adhesion↗

PubMed2003

Viridans streptococcus bacteremia in children on chemotherapy for cancer: an underestimated problem.

The authors discuss the morbidity associated with viridans streptococcus bacteremia, and its implications on the choice of antibiotics used as prophylaxis and treatment. They retrospectively studied the case notes of 38 children who were being treated for various malignant conditions in their unit and developed 40 episodes of bacteremia with viridans streptococci between October 1995 and January 1999. Viridans streptococci were the third commonest blood culture isolate during this period, after coagulase-negative staphylococci and Staphylococcus aureus. The majority of the isolates were Streptococcus mitis (55%). Others were S. sanguis (25%), S. oralis (12.5%), S. salivarius (5%), and S. acidominimus (2.5%). Twenty-five percent of the patients had been treated with regimens that included cytosine arabinoside, 60% were receiving prophylactic co-trimoxazole, and 87.5% were neutropenic. Thirty percent of patients had abnormal chest X-rays, and 15% were hypotensive; 2 patients required admission to the intensive care unit. Initial antibiotic therapy was changed because of failure of clinical response in 60% of cases, despite the infecting organism being sensitive in vitro. This study confirms the importance of viridans streptococci as a cause of bacteremia in pediatric hematology and oncology patients, leading to significant morbidity. Further work is required to establish the optimal treatment for viridans streptococcus bacteremia.

Adolescent↗

PubMed1997

In-vitro activity of quinupristin/dalfopristin compared with other widely used antibiotics against strains isolated from patients with endocarditis.

The activity of quinupristin/dalfopristin was compared with that of other widely used antibiotics against 355 strains isolated from patients with endocarditis. MICs were determined by a standard agar dilution method. Quinupristin/dalfopristin was inhibitory at 1 mg/L for all coagulase-negative staphylococci (n = 36) and for the majority of Staphylococcus aureus strains (n = 87). The activity of quinupristin/dalfopristin against 186 viridans streptococci was somewhat dependent on the species, with MIC50s ranging from 0.5 to 2 mg/L, being least active against Streptococcus bovis and most active against Streptococcus gordonii and Streptococcus mitis. For the staphylococci, quinupristin/dalfopristin was as active against erythromycin-susceptible as erythromycin-resistant strains. Viridans streptococci showed a slight but significant correlation between sensitivity to erythromycin and quinupristin/dalfopristin. It is concluded that quinupristin/dalfopristin has the potential to treat serious infections such as endocarditis caused by Gram-positive cocci.

Anti-Bacterial Agents↗

PubMed2001

Antibiotic resistance rates and macrolide resistance phenotypes of viridans group streptococci from the oropharynx of healthy Greek children.

A total of 200 isolates of viridans group streptococci isolated from the oropharynx of healthy Greek children were studied. Vancomycin, rifampicin, fluoroquinolones and dalfopristin/quinupristin were active against all tested isolates. High level resistance to gentamicin was not seen. Intermediate and high-level penicillin resistance was present in 28.5 and 14.5% isolates, respectively, with 41.3% of the latter group, being also resistant to cefotaxime. Resistance rates to other antimicrobials were as follows - erythromycin 38.5%, clarithromycin 33.5%, clindamycin 7.5% and tetracycline 23%. Penicillin resistance occurred more frequently in Streptococcus mitis isolates, while macrolide resistance was more frequent in S. oralis. MLSB resistance phenotype M was dominant (74%) among erythromycin resistant isolates, with phenotypes IR and CR being represented by 6 and 20% of isolates, respectively.

Adolescent↗

PubMed1995

Homeologous recombination and mismatch repair during transformation in Streptococcus pneumoniae: saturation of the Hex mismatch repair system.

The ability of the Hex generalized mismatch repair system to prevent recombination between partially divergent (also called homeologous) sequences during transformation in Streptococcus pneumoniae was investigated. By using as donor in transformation cloned fragments 1.7-17.5% divergent in DNA sequence from the recipient, it was observed that the Hex system prevents chromosomal integration of the least and the most divergent fragments but frequently fails to do so for other fragments. In the latter case, the Hex system becomes saturated (inhibited) due to an excess of mismatches: it is unable to repair a single mismatch located elsewhere on the chromosome. Further investigation with chromosomal donor DNA, carrying only one genetically marked divergent region, revealed that a single divergent fragment can lead to saturation of the Hex system. Increase in cellular concentration of either HexA, the MutS homologue that binds mismatches, or HexB, the MutL homologue for which the essential role in repair as yet remains obscure, was shown to restore repair ability in previously saturating conditions. Investigation of heterospecific transformation by chromosomal DNA from two related streptococcal species, Streptococcus oralis and Streptococcus mitis, also revealed complete saturation of the Hex system. Therefore the Hex system is not a barrier to interspecies recombination in S. pneumoniae. These results are discussed in light of those described for the Mut system of Escherichia coli.

Adenosine Triphosphatases↗

PubMed1983

Vitamin B6-dependent Streptococcus mimicking fungi in a patient with endocarditis.

A patient was referred to our hospital with a tentative diagnosis of fungal endocarditis based upon clinical symptoms, suggestive travel history, and microscopic visualization in blood cultures of gram-negative bulbous filaments that appeared to be fungal elements. Subcultures of the blood culture bottles were unsuccessful on all media with the exception of blood agar plates, which had been cross-streaked with Staphylococcus aureus. These plates grew vitamin B6-dependent streptococci. This nutritionally variant organism was determined by biochemical tests to be Streptococcus mitis (mitior). It had a penicillin MIC and MBC of 0.015 micrograms/mL and 0.03 micrograms/mL, respectively and streptomycin MIC and MBC of 0.78 micrograms/mL and 1.56 micrograms/mL, respectively. The patient was treated with these two agents and recovered. We stress the importance of suspecting vitamin B6-dependent streptococci, even when gram stains may suggest presence of other microorganisms.

Diagnosis, Differential↗

PubMed1993

Effect of co-aggregation on the pathogenicity of oral bacteria.

The pathogenicity of oral bacteria was studied by measuring the development of subcutaneous abscesses in mice after infection with Actinomyces viscosus and Streptococcus mitis either singly or as co-aggregated pairs. Heat-treated cells were also tested. The pathogenicity of the co-aggregates was examined in various viable and heat-treated combinations of the two bacterial species. More abscesses were formed by A. viscosus than S. mitis at all the bacterial concentrations tested. Also, abscess formation by co-aggregates of the two strains produced a higher percentage of abscess formation than those caused by infection with pure suspensions of A. viscosus or S. mitis. Co-aggregated cells were more resistant to phagocytosis and killing by neutrophils in vitro and in vivo. Furthermore, A. viscosus in co-aggregates were resistant to killing after engulfment by neutrophils. These results suggest that oral bacteria that are able to co-aggregate may resist phagocytosis, and this ability may be linked with pathogenicity.

Abscess↗

PubMed2000

The effect of scaling and root planing on the clinical and microbiological parameters of periodontal diseases: 12-month results.

BACKGROUND/AIMS: Previously, we reported that SRP resulted in a decrease in mean pocket depth and attachment level and reduced prevalence and levels of Bacteroidesforsythus, Porphyromonas gingivalis, and Treponema denticola at 3 and 6 months post-SRP in 57 subjects with adult periodontitis. 32 of the 57 subjects were monitored at 9 and 12 months. Thus, the purpose of the present investigation was to evaluate the microbial and clinical effects of SRP in 32 (mean age 48+/-11) subjects over a 12-month period. METHOD: Clinical assessments of plaque, gingival redness, suppuration, bleeding on probing, pocket depth and attachment level were made prior to SRP and at 3, 6, 9, and 12 months post-therapy. Subgingival plaque samples were taken at each visit and analyzed using the checkerboard DNA-DNA hybridization technique for the presence and levels of 40 subgingival species. Each subject also received maintenance scaling at each of the subsequent monitoring visits. Differences in clinical parameters and prevalence and levels of bacterial species were analyzed pre- and post-therapy using the Wilcoxon signed ranks test. The Quade test for related samples was used for analysis of multiple visits. RESULTS: Mean pocket depth (mm+/-SEM) decreased from 3.2+/-0.3 at baseline to 2.9+/-0.3 at 12 months (p<0.01). Mean attachment level showed significant reduction at 6 months, but did not diminish further. Bleeding on probing and plaque were significantly reduced at 12 months (p<0.001, p<0.05, respectively). P. gingivalis, B. forsythus and T. denticola decreased in prevalence and levels up to the 6-month visit and remained at these lower levels at 9 and 12 months. Significant increases in levels and prevalence were noted at 12 months for Actinomyces naeslundii genospecies 2, Actinomyces odontolyticus, Fusobacterium nucleatum ss polymorphum, Streptococcus mitis, Capnocytophaga sp, and Veillonella parvula. CONCLUSIONS: The data suggest that the maintenance phase of therapy may be essential in consolidating clinical and microbiological improvements achieved as a result of initial therapy.

Actinomyces↗

PubMed1998

Acid-regulated proteins induced by Streptococcus mutans and other oral bacteria during acid shock.

Our previous research has demonstrated that with the more aciduric oral bacteria, an acid shock to sub-lethal pH values results in the induction of an acid tolerance response that protects the cells at extremely low pH (pH 3.0-4.0) that kills unadapted control cells maintained at pH 7.5 (Oral Microbiol Immunol 1997: 12: 266-273). In this study, we were interested in comparing the protein profiles of acid-shocked and control cells of nine organisms from three acid-ogenic genera that could be categorized as strong, weak and non-acid responders in an attempt to identify proteins that could be classified as acid-regulated proteins and which may be important in the process of survival at very low pH. For this, log-phase cultures were rapidly acidified from pH 7.5 to 5.5 in the presence of [14C]-amino acids for varying periods up to 2 h, the period previously shown to be required for maximum induction of the acid response. The cells were extracted for total protein and subjected to one-dimensional sodium dodecyl sulfate-polyacrylamide chromatography with comparable control and acid-shocked protein profiles compared by scanning and computer analysis. Of particular interest were the proteins in the acid-shocked cells that showed enhanced labeling (i.e., synthesis) over the control cells, since these were considered acid-regulated proteins of importance in pH homeostasis. Streptococcus mutans LT11 generated the most rapid and complex pattern: a total of 36 acid-regulated proteins showing enhanced synthesis, with 25 appearing within the first 30 min of acid shock. The enhanced synthesis was transient with all proteins, with the exception of two with molecular weights of 50/49 and 33/32 kDa. Within the acid-regulated proteins were proteins having molecular weights comparable to the heat shock proteins and the various subunits of the membrane H+/ATPase. By comparison, the strong responder, Lactobacillus casei 151, showed the enhanced formation of only nine proteins within the first 30 min of the acid shock, with a total of 11 acid-regulated proteins formed during the 2-h adaptation period with enhanced synthesis transient for seven of these proteins. Streptococcus salivarius AT2 and Streptococcus gordonii TH12 had the formation of 6 and 8 proteins enhanced, while the weakly responding organisms, Streptococcus sanguis ATCC 10,556 and Streptococcus oralis ATCC 10,557, exhibited 8 and 6 such proteins, respectively. Even non-responding strains unable to survive at very low pH, such as Streptococcus sobrinus CH125/43, Streptococcus mitis ATCC 12,261 and Actinomyces naeslundii 301-13 showed the initial formation of 3-9 acid-regulated proteins, but protein synthesis was not sustained over the entire adaptation period. Clearly, the survival of oral bacteria at very low pH is related, not to the total number of the acid-regulated proteins induced per se but to the formation of key proteins that function to augment normal pH homeostasis.

Acids↗

PubMed1981

Bacteremia caused by viridans streptococci in 71 children.

A review of the hospital records of 71 patients from whose blood viridans streptococci were isolated showed that in 13 cases the patient's illness was definitely related to the bacteremia: 4 patients had endocarditis, 3 had pneumonia, 2 had peritonitis and 1 each had meningitis, a scalp wound infection, sinusitis and otitis media. The bacteremia may have contributed to the two deaths among these 13 patients. In 45 cases the viridans streptococci may have contributed to the patient's illness: 15 patients had an infection of the lower respiratory tract and 7 an infection of the upper respiratory tract, 8 were neonates with suspected septicemia, 3 had soft tissue infections, 3 had leukemia and sepsis, and 9 had miscellaneous infections; the bacteremia was unrelated to the two deaths in this group. In another 13 cases the viridans streptococci could not be related to the patient's illness. The species most frequently isolated were Streptococcus mitis, S. sanguis II and S. MG-intermedius. The outcome of the bacteremia was generally good, even among the 11 patients not treated with antibiotics. When viridans streptococci are cultured from a single blood sample, further samples of blood and, if feasible, specimens from the associated focus of infection should be obtained for culture; further blood cultures are especially important in cases of suspected endocarditis.

Child, Preschool↗

PubMed1983

Meningitis--a complication of spinal anesthesia.

During a five-year period, 17 of 1429 patients admitted with meningitis had had recent spinal anesthesia in Cairo, Egypt. Ten of the 17 had positive cerebrospinal fluid cultures: 8 were Pseudomonas aeruginosa, 1 was Staphylococcus aureus, and 1 was Streptococcus mitis. These organisms were not cultured from patients who had not had spinal anesthesia. Two patients with negative cultures had lumbar spine x-ray changes consistent with tuberculosis. Antibiotic therapy was based upon the sensitivity of cultured organisms. Four of the 17 patients died. These data strongly suggest that meningitis in patients with recent spinal anesthesia is commonly due to unusual or nosocomial organisms. Aggressive, meticulous bacteriologic evaluation of these patients is essential.

Anesthesia, Spinal↗

PubMed1996

The establishment of a community of oral bacteria that controls the growth of Candida albicans in a chemostat.

The purpose of this study was to establish and identify a community of oral bacteria that controls the growth of Candida albicans in the chemostat. The chemostat was operated under glucose-limiting conditions at a dilution rate of 0.05 h-1 and inoculated with a yeast-free suspension of a tongue scraping. After a steady state had been reached, it was inoculated with C. albicans to establish the yeast and determine whether its growth could be contained. The steady-state community comprised the species Streptococcus sanguis, Streptococcus sobrinus, Streptococcus mitis, Lactobacillus casei, Eubacterium saburreum, Veillonella dispar and Fusobacterium nucleatum. Bacteroides gracilus and Haemophilus segnis were also detected but infrequently. Yeast growth was suppressed and yeast cells were lost at the same rate as the theoretical washout rate. It is concluded that this mixed community of oral bacteria can be used to identify the parameters that maintain the equilibrium between oral bacteria and C. albicans in the oral cavity.

Antibiosis↗