Strains Of Viridans Streptococci Research Articles

Viridans streptococcal (Streptococcus intermedius) mitral valve subacute bacterial endocarditis (SBE) in a patient with mitral valve prolapse after a dental procedure: The importance of antibiotic prophylaxis

Subacute bacterial endocarditis (SBE) is an infection of the heart involving damaged valves or endothelium. The most common organisms causing SBE are the viridans streptococci. Viridans streptococci differ in their propensity to cause SBE, which is related to the ability to adhere to damaged heart valves and endothelium, which is a function of extracellular matrix production. Streptococcus intermedius is a member of the S. anginosus group. S. intermedius is one of the many strains of viridans streptococci and a rare cause of SBE. SBE may result following a high-grade, sustained veridans streptococcal bacteremia in patients with predisposing cardiac lesions. Because viridans streptococci are relatively avirulent pathogens in normal hosts, they usually present as SBE. Some strains of viridans streptococci are inherently more virulent (eg, S. intermedius) and clinically resemble S. lugdunensis or S. aureus. We report a case of S. intermedius SBE in a patient with mitral valve prolapse (MVP). Throughout the patient's life, she received antibiotic prophylaxis for dental procedures and never developed SBE. Because of changes in endocarditis prophylaxis guidelines in 2007, recommending no prophylaxis for dental procedures in patients with MVP, she did not receive prophylaxis for a dental procedure 3 months before admission. The change in prophylaxis recommendations was based on the relatively low incidence of endocarditis with certain cardiac lesions. The recommendations were also based on concern for antibiotic resistance from widespread antibiotic use for antibiotic prophylaxis. There has been no appreciable increase in penicillin resistance, and antimicrobial resistance is not an important consideration among the viridans streptococci. The incidence of SBE is not high after dental procedures in patients with MVP, but if SBE occurs, it may result in serious consequence for the patient. In this case, the patient developed S. intermedius, mitral valve SBE complicated by a cerebral vascular accident, and embolic occlusion of her leg. She was given optimal antibiotic treatment with ceftriaxone 2 g (intravenously) every 24 hours plus gentamicin 120 mg (intravenously) every 24 hours (synergy dose) but failed to respond to antimicrobial therapy. Although her S. intermedius bacteremia was rapidly cleared with antimicrobial therapy, sterilization of her vegetation was not accomplished, and during therapy, the size of her cardiac vegetation actually increased in size. Because of therapeutic failure despite optimal antibiotic therapy, the increasing size of her vegetation necessitated mitral valve replacement, which the patient underwent. Reasons for apparent/real antibiotic failure include inappropriate antimicrobial therapy, inadequately dosed antimicrobial therapy, antibiotic "tolerance," or increased pathogen virulence. Her strain of S. intermedius was sensitive to all antibiotics and not due to a "tolerant strain", i.e., her minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were the same (<0.25 microg/mL). In this case, despite optimal antimicrobial therapy, and in the absence of resistance/tolerance, therapeutic failure was best explained on the basis of S. intermedius virulence. The take-home lesson for clinicians is that it is better to err on the side of antibiotic prophylaxis even in patients with low-risk cardiac lesions. Failure to administer antibiotic prophylaxis for dental procedures may result in SBE and have disastrous consequences for the patient, which, in this case, resulted in a cerebral vascular accident, embolic occlusion of the leg, and mitral valve replacement. In terms of virulence in patients with endocarditis, S. intermedius may resemble S. lugdenesis.

Antibacterial activity of yoghurt against viridans streptococci in vitro

Objective Yoghurt consumption leads to a selective decrease in the oral level of mutans streptococci. It is not clear whether this decrease is due to the bactericidal activity of yoghurt or other mechanisms. The present study investigated the differences in susceptibility to yoghurt between several strains of viridans streptococci. Design The sources of variation were minimised, at the expense of the external validity of the study, using culture collection strains. Each strain was tested separately on five occasions in planktonic form and logarithmic growth phase. Two strains of each of the following Streptococcus species were tested: mutans, sobrinus, gordonii, oralis, parasanguinis and sanguinis. One millilitre [10 8 colony-forming units (cfu)] of each strain was incubated (37 °C, 60 min) with 9 mL of fat-free plain yoghurt containing Streptococcus thermophilus and Lactobacillus bulgaricus (10 8 and 10 7 cfu/g, respectively) in gently vortexed tubes. Survival rates were calculated every 15 min by dividing the number of viable cells, obtained using conventional laboratory procedures, by the baseline number. Results Survival rates were 8% ( S. mutans 6519T), 12% ( S. mutans 31738), 35% ( S. oralis 25671) and >50% (all other species tested) after 15 min, and 0.01% ( S. mutans) and >10% (all other species tested) after 30 min. Overall, S. parasanguinis and S. sobrinus were the most resistant species. When heat-treated yoghurt (<10 cfu/g bacteria and inactivated bacteriocins) was used, this antibacterial activity was not found. Conclusion In vitro, yoghurt with live bacteria showed selective anti-mutans activity, suggesting that the overall decrease in mutans streptococci in vivo could be due to a bactericidal effect on S. mutans but not on S. sobrinus.

Bacterial Interference of Penicillin-Sensitive and -Resistant Streptococcus Pneumoniae by Streptococcus Oralis in an Adenoid Organ Culture: Implications for the Treatment of Recurrent Upper Respiratory Tract Infections in Children and Adults

The role of the viridans group of streptococci (Streptococcus oralis) in the prevention of colonization with Streptococcus pneumoniae was investigated in an adenoid organ culture system. The adenoids from 10 patients who were undergoing adenoidectomy for either hypertrophy or recurrent otitis media were used. Streptococcus oralis Parker and S. oralis Booth (two organisms isolated from the nasopharynges of patients undergoing adenoidectomy only and patients undergoing adenoidectomy and bilateral tympanostomy with tubes, respectively) uniformly inhibited both penicillin-sensitive and penicillin-resistant S. pneumoniae. Although both strains of S. oralis inhibited the growth of both S. pneumoniae strains, strain Parker provided more complete inhibition than did strain Booth. The results indicate that some strains of S. oralis may inhibit the growth of the most serious pathogens in the nasopharynx. It is therefore possible that colonization of inhibitory strains of viridans streptococci may be used in the nasopharynx as a relatively safe and inexpensive approach to prevention of recurrent otitis media in some children and of recurrent suppurative sinusitis in both children and adults.

Bacteriology of Orofacial Infection

Objective: To establish the causative organisms of orofacial infections and their antimicrobial susceptibilities. Patients and Methods: In this retrospective chart review, 416 samples of pus were obtained from 409 patients with orofacial infection attending a dental school between 1994 and 1998 were sent for culture and susceptibility testing.Results: 109 samples grew normal oral flora and 228 samples grew pathogens. No organisms were isolated in 79 samples. The most common pathogens isolated were viridans streptococci (22.4%), Staphylococcus aureus (18.4%), enteric gram-negative bacteria (20.2%), and Pseudomonas aeruginosa (9.7%). All strains of viridans streptococci were susceptible to penicillin. Viridans streptococci and Staphylococcus aureus showed good susceptibilities to erythromycin of 85.7% and 87.1%, respectively. Of the enteric gram-negative bacteria, 47.8% were resistant to ampicillin. No anaerobic organisms were isolated in this study.Conclusions: The profile of aerobic isolates and their susceptibilities to antimicrobial agents should assist in selecting empirical therapy and directing therapy for orofacial infection. Inclusion of antimicrobial agents against anaerobic bacteria is recommended.

Optimisation of the prevention and treatment of bacterial endocarditis.

This paper reviews currently established guidelines for the prevention and treatment of bacterial endocarditis. Endocarditis remains a life-threatening disease with substantial morbidity and mortality. Primary prevention of endocarditis, whenever possible, is therefore very important. In an individual with endocarditis, rapid diagnosis and effective treatment are essential to good patient outcome. The guidelines discussed here are largely based on those issued by the American Heart Association. While most cases of endocarditis are not attributable to an invasive procedure, certain procedures are associated with bacteraemia by organisms commonly associated with endocarditis, and antibacterial prophylaxis is recommended before such procedures. Patient cardiac conditions are stratified into high, moderate and negligible risk categories based on potential outcome if endocarditis develops. For oral, dental, respiratory tract, and oesophageal procedures (most often associated with viridans streptococci) the standard antibacterial regimen is oral amoxicillin. For gastrointestinal and genitourinary procedures (most often associated with enterococci), parenteral antibacterials are most often recommended. For high-risk patients, intramuscular or intravenous ampicillin and gentamicin (or vancomycin and gentamicin in penicillin-allergic individuals) is recommended. For moderate risk patients, an option of oral amoxicillin or parenteral ampicillin is offered. Treatment of bacterial endocarditis is guided by identification of the causative micro-organism. Approximately 80% of cases of endocarditis are due to the gram-positive cocci: streptococci and staphylococci. Other gram-positive organisms include enterococci (predominantly Enterococcusfaecalis and E. faecium) and the HACEK group of organisms (Haemophilus parainfluenzae, H. aphrophilus, Actinobacillus [Haemophilus] actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae). In general, for uncomplicated cases of endocarditis due to penicillin-susceptible viridans streptococci or Streptococcus bovis 4 weeks of benzylpenicillin (or ceftriaxone) is the preferred regimen for most patients aged >65 years. A 2-week course of treatment can be used when gentamicin is added, in patients at low risk for adverse events caused by gentamicin therapy. When endocarditis is caused by strains of viridans streptococci or S. bovis relatively resistant to penicillin, or by enterococci, both benzylpenicillin and gentamicin are recommended. For staphylococcal endocarditis on native heart valves, nafcillin or oxacillin with or without gentamicin is the preferred regimen. In prosthetic valve staphylococcal endocarditis, nafcillin (or oxacillin) with rifampicin and gentamicin is recommended. For all of the above situations, vancomycin is recommended for the patient allergic to penicillin (or methicillin). Finally, consideration of out-of-hospital therapy in selected patients is discussed.

牛乳房炎由来黄色ブドウ球菌およびB群レンサ球菌の簡易同定

Staphylococci and streptococci from bovine mastitis cases were identified by latex agglutination test (LA) using commercial kits. Of a total of 140 milk samples, 162 isolates were obtained from 116 samples. Of those strains; 40 (24.7%) strains of Staphylococcus aureus, 39 (24.1%) strains of coagulase-negative staphylococci, 19 (11.7%) strains of viridans streptococci and 18 (11.1%) strains of group B streptococci. By LA using colonies grown on the agar plate, all the S. aureus isolates were positive for Staphaurex, and 30 (75.0%) for PS latex. All the group B streptococci strains and 5 of 7 Enterococcus faecalis strains were positive for all the kits used. In the direct LA using milk containing more than 104 CFU/ml of group B streptococci, all the samples were positive.

Adhesive Properties of Viridans Streptoccocal Species

Seventy-one strains of viridans streptococci, classified as Streptococcus sanguis, S. gordonii, S. oralis, S. mitis or S. anginosus by a revised taxonomic scheme, were characterized and compared by their specific adhesive properties. The frequency of bacterial adhesion to saliva-coated hydroxyapatite (SHA) was greater among strains of S. sanguis, S. gordonii and S. oralis than among those of S. mitis and S. anginosus . Similarly, the expression of sialic acid reactive adhesins, detected by neuraminidase sensitive bacterial haemagglutination, was noted more frequently with strains of S. sanguis (19 of 21), S. gordonii (14 of 16) and S. oralis (8 of 11) than those of S. mitis (2 of 12) and S. anginosus (0 of 11). Most strains of S. gordonii (14 of 16) and S. oralis (7 of 11) also aggregated acidic proline rich protein-coated latex beads, but this activity was observed rarely with strains of S. sanguis (2 of 21), S. mitis (1 of 12) and S. anginosus (0 of 11). Strains of S. anginosus (6 of 11) participated in lactose resistant coaggregations with actinomyces in coaggregation groups A (e.g. Actinomyces viscosus T14V-J1) and B (e.g. A. naeslundii WVU45). Lactose resistant coaggregations were also observed between strains of S. gordonii (9 of 16) and actinomyces in coaggregation group A. Lactose sensitive coaggregations occurred between actinomyces and each of 11 S. oralis strains but less frequently with strains of S. sanguis (6 of 21), S. gordonii (3 of 16), S. mitis (3 of 12) and S. anginosus (1 of 11). Certain streptococcal strains with receptors for the lactose sensitive lectins of actinomyces, including 9 of 11 S. oralis , also coaggregated frequently with strains of either S. sanguis (10 of 21) or S. gordonii (9 of 16). Further studies with representatives of these latter three streptococcal species suggested that the streptococci with receptors for the GalNAc sensitive lectins of S. sanguis and S. gordonii were those with GalNAc βl →3Gal- rather than Gal βl →3GalNAc-containing cell wall polysaccharides. Keywords - Streptococci, Adhesion, Coaggregation, Adhesins, Lectins, Receptors.

Reactivity of the glycocalyx of endocarditis-producing viridans group streptococci

We correlated quantity of streptococcal polysaccharides and endocarditis production by those bacterial strains. To investigate this finding further, we studied the composition of the glycocalyx using a spectrophotometric assay and lectin analysis of exopolysaccharides from endocarditis- and non-endocarditis-producing strains of viridans streptococci. Identical weights of glycocalyx from the clinical endocarditis isolates produced significantly different absorbances as compared with the nonendocarditis isolates ( P < 0.0012, Wilcoxon rank test). Lectinbinding experiments showed that endocarditis-producing streptococci contained increased amounts of glucose, galactose, sialic acid, and mannose. These data suggest that the glycocalyx of endocarditis-producing viridans streptococci is both qualitatively and quantitatively different from non-endocarditis-producing isolates. These differences can be measured in vitro.

Activity of teicoplanin compared with vancomycin alone, and combined with gentamicin, against penicillin tolerant viridans streptococci and enterococci causing endocarditis

Teicoplanin had greater inhibitory activity than vancomycin against most of 22 penicillin tolerant strains of streptococci, but both drugs failed to kill 99·9% of the inoculum when tested alone at concentrations less than 16mg1 −1. Bactericidal synergy between teicoplanin combined with gentamicin and vancomycin combined with gentamicin was always demonstrated in further tests with 16 penicillin tolerant strains. Teicoplanin had greater bactericidal activity than vancomycin against five of seven strains of viridans streptococci and five of nine strains of enterococci in MBC experiments, where each drug was combined with gentamicin. Killing curve experiments with five penicillin tolerant streptococci showed teicoplanin and vancomycin to have similar bactericidal activity within 24 h when tested at 5 mg1 −1 with 2 mg1 −1 gentamicin. However, at 0·5mg1 −1 only teicoplanin had a bactericidal synergic effect with gentamicin.

Penicillin therapy for treatment of experimental endocarditis caused by viridans streptococci in animals.

We studied the efficacy of penicillin and penicillin combined with streptomycin in the treatment of experimental endocarditis caused by viridans streptococci that are susceptible, tolerant, or relatively resistant to penicillin. Rabbits with experimental endocarditis were treated with procaine penicillin (1.5 X 10(5) U/kg) administered twice daily or with procaine penicillin (1.5 X 10(5) U/kg) plus streptomycin (20 mg/kg) administered twice daily for five days. Compared with control animals, animals treated with penicillin alone experienced a significant reduction (P less than .001) of colony forming units per gram of cardiac valve vegetations when infected with streptococci that are susceptible, tolerant, or resistant to penicillin. This antibiotic alone was less effective against streptococci that were tolerant or resistant to penicillin than against streptococci susceptible to the drug (P less than .01). The combination of penicillin and streptomycin was more effective therapy than was penicillin alone in animals with penicillin-tolerant or penicillin-resistant streptococci causing endocarditis (P less than .01). Penicillin-streptomycin therapy was less active against penicillin-resistant strains than against either penicillin-tolerant (P less than .04) or penicillin-susceptible (P less than .01) strains. The results of our study suggest that tolerance or relative resistance to penicillin in strains of viridans streptococci influences the response to therapy with penicillin alone or penicillin combined with streptomycin in the treatment of experimental endocarditis caused by viridans streptococci.

Detection of pneumococci in blood cultures by latex agglutination.

Latex agglutination by use of the Pneumoslide test on clinical blood cultures detected 22 Streptococcus pneumoniae strains as the etiological agents in 47 streptococcal septic episodes. The other 25 isolates were identified as viridans streptococci or streptococci of groups A, B, D, or G. The test demonstrated 100% sensitivity, 92% specificity, and predictive values for positive and negative reactions of 91 and 92%, respectively. Two false-positive reactions were caused by strains of viridans streptococci. The two strains continued to give positive reactions when colonies from blood agar plates were tested according to the instructions of the manufacturer. This latex agglutination test is an effective tool for the rapid diagnosis of pneumococci in blood cultures.

Cell-free released components of Streptococcus sanguis inhibit human platelet aggregation.

To study the role of surface components in the selective binding and aggregation of platelet-rich plasma (PRP) by strains of viridans streptococci, we treated the binding, aggregation strain Streptococcus sanguis I 2017-78 by sonication or trypsinization. Morphologically identifiable electron-dense fibrils were released from the cell wall, apparently from an inner electron-dense layer, under conditions that left cells intact. These controlled conditions were determined to cause submaximal loss in adhesion to platelet ghosts and PRP aggregation by treated, washed S. sanguis. Soluble components were recovered from the controlled sonic or L-(tosylamido 2-phenyl)ethyl chloromethyl ketone-trypsin treatments. Each showed dose-response inhibition of aggregation when preincubated with PRP before challenge with fresh, untreated S. sanguis. The time to onset of PRP aggregation was inhibited by 50% with 0.2 mg of TPCK-trypsin peptides or 1.0 mg of the sonicate per ml per 2 X 10(8) platelets. Components of both preparations were immunologically cross-reactive, but lipoteichoic acid was not a major antigen of either. By weight, the TPCK-trypsin peptides were virtually all protein; the sonicate residues identified were about 50% protein and 7% hexose. Each was a complex mixture of components as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. More than 8 TPCK-trypsin peptides and 16 sonicate components were so identified. In contrast, at least four or five components from either preparation were recognized as surface determinants by a rabbit antiserum to whole homologous microbes. Platelet-binding ligands of S. sanguis could be among these determinants.

Penicillin prophylaxis in children with cardiac disease: Postextraction bacteremia and penicillin-resistant strains of viridans streptococci

Penicillin prophylaxis in children with cardiac disease: Postextraction bacteremia and penicillin-resistant strains of viridans streptococci

ADP-like platelet aggregation activity generated by viridans streptococci incubated with exogenous ATP.

To explore the possibility that Streptococcus sanguis aggregation of platelet-rich plasma (PRP) might be mediated by soluble agents, we tested cell-free S. sanguis supernatant for aggregation activity. The supernatant of untreated S. sanguis was without measurable PRP aggregation activity. In contrast, the cell-free supernatant of ATP-incubated S. sanguis produced an immediate wave of PRP aggregation. The supernatant with PRP aggregating activity contained insufficient protease to produce a response. The response increased with the time of incubation with ATP. Active supernatant was desalted and chromatographed on nucleotide-calibrated columns of Dowex 1-X8. An active ADP function was identified. The activity was insensitive to dicyclohexylcarbodiimide, but was sensitive to both Ca2+ and Ca2+-Mg2+ chelating agents, cold (4 degrees C), heat (80 degrees C), pH (optimum between pH 7 and 8), apyrase, and sodium molybdate. In addition, preincubation of PRP with adenosine inhibited activity. Strains of viridans streptococci were screened for activity. Aggregation-promoting strains showed two times more activity than did other strains. Although it was not vigorously excluded that the ADP was discharged from the microbes, the existence of an exogenous ATPase on S. sanguis was strongly suggested. The expression of the activity was associated with the lag time to onset of PRP aggregation with intact S. sanguis. This activity could, therefore, be a synergistic promoter of PRP aggregation and an additional virulence factor in endocarditis.

Penicillin-aminoglycoside synergy in experimental Streptococcus viridans endocarditis.

In vitro synergism has been described for many strains of Streptococcus viridans with penicillin and streptomycin; however, the in vivo correlation of this phenomenon is lacking. Rabbits with catheter-induced aortic valve endocarditis caused by S. viridans (MIC, 0.06 [tg/ml) were treated with penicillin, penicillin plus streptomycin, and penicillin plus gentamicin. The bacteria were eradicated from the cardiac vegetations in approximately one-half of the time with the penicillinaminoglycoside combinations (three to four days) than was required with penicillin alone (seven to 10 days), as determined by titrations of viable bacteria from vegetations and relapse after discontinuation of therapy.

Transformation reactions between Pneumococcus and three strains of Streptococci.

Reciprocal transformation reactions to streptomycin resistance have been demonstrated between pneumococcus and 2 strains of viridans streptococci, which by the usual bacteriological criteria are distantly related to pneumococcus. Desoxyribonucleic acid (DNA) extracts of a strain of streptomycin-resistant Streptococcus salivarius have been found capable of transforming pneumococcus and two strains of viridans streptococci but the strain itself was not transformed by autologous or heterologous DNA extracts. The two strains of viridans streptococci were more efficient than pneumococcus as receptors of both autologous and heterologous transforming principles. It is inferred, therefore, that efficiency of transformation does not necessarily indicate closeness of relationship among bacteria. The efficiency of transforming principles (TP's) from three streptococcal strains to induce streptomycin resistance in pneumococcus increased following their reduplication in pneumococcus. At the same time the efficiency of two of these TP's to transform streptococcus was reduced. Resistance to optochin (ethylhydrocupreine), a characteristic of most streptococci, can be transferred to pneumococcus, a naturally susceptible species, by transformation reactions.

Antigenic similarity of some trained resistant strains of viridans streptococci to Streptococcus fecalis.

SummaryAntigens similar to those found in a strain of S. fecalis were found in all but one of the sulfathiazole, aureomycin, penicillin, and streptomycin-trained resistant strains of viridans streptococci. The antigens were not present in 5 of the parent strains with low sulfathiazole resistance but were present in 2 with higher resistance.

The Treatment of Bacterial Endocarditis with Penicillin

FLEMING,1 in his original studies on the antibacterial action of cultures of his strain of Penicillium, included some strains of Streptococcus viridans, which he found to vary considerably in their susceptibility. Others2 3 4 5 6 7 8 have since confirmed these findings with more purified preparations of penicillin in vitro, noting the wide differences in susceptibility of single strains and finding some to be relatively resistant. Clinical trials in the treatment of subacute bacterial endocarditis were begun in 1942. The earliest reports were somewhat discouraging,9 10 11 12 13 14 15 16 but they did suggest the possibility that larger doses of penicillin given over a longer time might produce better results. . . .

Pathology and Bacteriology of Streptococcus Endocarditis in Relationship to Sulfonamide Chemotherapy: II. The Effect of Temperature Elevation on the Action of Sulfathiazole upon Endocarditis Strains of Streptococcus Viridans, Enterococci and Group A Streptococci

Pathology and Bacteriology of Streptococcus Endocarditis in Relationship to Sulfonamide Chemotherapy: II. The Effect of Temperature Elevation on the Action of Sulfathiazole upon Endocarditis Strains of Streptococcus Viridans, Enterococci and Group A Streptococci

PENICILLIN IN THE TREATMENT OF MENINGITIS

Reports in the literature pertaining to the clinical effects of penicillin in the treatment of meningitis have in general been confined to observations on small groups of patients or on isolated cases. 1 No definite conclusions may be drawn from them concerning the efficacy of penicillin, the most satisfactory method of treatment or the minimum adequate dosage requirements. However, from in vitro studies demonstrating the pronounced sensitivity of the meningococcus, Streptococcus haemolyticus, pneumococcus and some strains of Streptococcus viridans to theaction of penicillin, this agent should prove to be of considerable therapeutic value in the management of such infections, particularly in individuals who are sulfonamide resistant or sulfonamide reactors. In a preliminary report 2 on 31 patients with cerebrospinal fever, we recorded 30 recoveries following the combined intrathecal and intravenous or intramuscular use of penicillin and concluded that penicillin is a safe, effective and highly potent agent in the treatment