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Atsushi Saito - One of the best experts on this subject based on the ideXlab platform.
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The role of the capsule of the Streptococcus milleri group in its pathogenicity
Journal of Infection and Chemotherapy, 2004Co-Authors: Shuzo Kanamori, Takashi Shinzato, Nobuchika Kusano, Atsushi SaitoAbstract:Study of the pathogenicity of encapsulated strains of the Streptococcus milleri group (SMG) was performed by examination of the ability to cause subcutaneous abscesses in mice and by phagocytosis and phagocytic killing of human polymorphonuclear neutrophils (PMNs) against the organisms. All 3 encapsulated isolates from patients with pneumonia or lung abscess induced abscesses in the mice; however, only 2 of 20 unencapsulated isolates from patients with lung abscess or thoracic empyema did so. The 3 encapsulated strains inhibited more phagocytosis and phagocytic killing of PMNs than the unencapsulated strains. In addition, encapsular material separated from Streptococcus constellatus RZYK001 also inhibited phagocytosis and phagocytic killing in proportion to increasing concentrations of the capsular material. These results suggest that capsular material produced by SMG might be a pathogenic factor.
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trends in antimicrobial susceptibility of the Streptococcus milleri group
Journal of Infection and Chemotherapy, 2002Co-Authors: Natsuo Yamamoto, Futoshi Higa, Masao Tateyama, Toru Kubota, Masato Tohyama, Shuzo Kanamori, Takashi Shinzato, Atsushi SaitoAbstract:A collection of 114 clinical Streptococcus milleri group (SMG) strains at the Ryukyu University Hospital obtained in 1999 and 2000, was identified and tested for susceptibility to 12 antibiotics. The percentage of strains with intermediate susceptibility to penicillin G was relatively high (14%). Cefaclor and cefotiam, with a MIC 90 of 2 μg/ml, were less active than cefotaxime. Strains nonsusceptible to erythromycin, clindamycin, and azithromycin were found with a frequency of 8%, 5%, and 4%, respectively. Almost all of the SMG strains were susceptible to fluoroquinolones (except for 1% of the strains nonsusceptible to levofloxacin), and sitafloxacin (DU-6859a) was the most active agent among the 12 tested antibiotics.
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the Streptococcus milleri group as a cause of pulmonary infections
Clinical Infectious Diseases, 1995Co-Authors: Takashi Shinzato, Atsushi SaitoAbstract:Streptococci that colonize the mouth and upper respiratory tract tend to be considered harmless commensals. In 45 cases of acute pneumonia and/or pulmonary abscess and 25 cases of thoracic empyema, the predominant species recovered were anaerobic bacteria and the Streptococcus milleri group, which encompasses the oral species Streptococcus anginosus, Streptococcus constellatus, and Streptococcus intermedius. The isolation of most S. milleri organisms along with oral anaerobes indicated synergy between these groups. Studies in a mouse model of pneumonia demonstrated this synergy ; mortality was higher, histopathologic abnormalities were more marked (reflecting acute pneumonia followed by pulmonary abscess or empyema), and viable bacteria were more numerous in the lungs of mice with mixed infections caused by the S. milleri group and anaerobes than in the lungs of those with monomicrobial infection. In vitro studies elucidated a possible mechanism of this synergistic effect : anaerobes may enhance the growth of the S. milleri group and/or inhibit the bactericidal activity of the host. We conclude that the S. milleri group is more important in pulmonary infections than has previously been recognized.
Jill E. Clarridge - One of the best experts on this subject based on the ideXlab platform.
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interaction between human polymorphonuclear leukocytes and Streptococcus milleri group bacteria
The Journal of Infectious Diseases, 2002Co-Authors: Anna Wanahita, Jill E. Clarridge, Daniel M. Musher, Elizabeth A Goldsmith, Jose Rubio, Bhuvaneswari Krishnan, Joann TrialAbstract:Because Streptococcus milleri group (SMG) bacteria--Streptococcus constellatus, Streptococcus intermedius, and Streptococcus anginosus--exhibit a striking propensity to cause abscesses, the interaction of these organisms with human polymorphonuclear leukocytes (PMNL) was examined. After incubation in pooled normal human serum, SMG stimulated less chemotaxis than did Staphylococcus aureus, in contrast to viridans streptococci, which caused greater chemotaxis than did S. aureus. PMNL ingested greater numbers of SMG and viridans streptococci than S. aureus but killed these organisms more slowly and less completely. Relative resistance to killing by PMNL is expected in organisms that cause abscesses, and inhibition of chemotaxis may contribute to pathogenicity, because delayed arrival of PMNL gives a head start to proliferating bacteria. This study helps explain the capacity of SMG to cause abscesses. It is unclear, however, why viridans streptococci, bacteria that rarely produce abscesses, share some of these same properties.
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antibiotic susceptibilities of genetically characterized Streptococcus milleri group strains
Antimicrobial Agents and Chemotherapy, 2001Co-Authors: Michael Tracy, Jill E. Clarridge, Anna Wanahita, Yevgeny Shuhatovich, Elizabeth A Goldsmith, Daniel M. MusherAbstract:Previous studies of the antibiotic susceptibility of Streptococcus milleri group organisms have distinguished among species by using phenotypic techniques. Using 44 isolates that were speciated by 16S rRNA gene sequencing, we studied the MICs and minimum bactericidal concentrations of penicillin, ampicillin, ceftriaxone, and clindamycin for Streptococcus intermedius, Streptococcus constellatus, and Streptococcus anginosus. None of the organisms was resistant to beta-lactam antibiotics, although a few isolates were intermediately resistant; one strain of S. anginosus was tolerant to ampicillin, and another was tolerant to ceftriaxone. Six isolates were resistant to clindamycin, with representation from each of the three species. Relatively small differences in antibiotic susceptibilities among species of the S. milleri group show that speciation is unlikely to be important in selecting an antibiotic to treat infection caused by one of these isolates.
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genotypic and phenotypic characterization of Streptococcus milleri group isolates from a veterans administration hospital population
Journal of Clinical Microbiology, 1999Co-Authors: Jill E. Clarridge, Cheryl Osting, Mehri Jalali, Janet Osborne, Michael WaddingtonAbstract:Because identification of the species within the “Streptococcus milleri” group is difficult for the clinical laboratory as the species share overlapping phenotypic characteristics, we wished to confirm biochemical identification with identification by 16S rRNA gene sequence analysis. Ninety-four clinical isolates previously identified as the “Streptococcus milleri” group were reclassified as S. anginosus, S. constellatus, or S. intermedius with the API 20 Strep system (bioMerieux Vikek, Hazelton, Mo.) and the Fluo-card (Key Scientific, Round Rock, Tex.). In addition, we determined the Lancefield group, hemolysis, colony size, colony texture, repetitive extragenic palindromic PCR (rep-PCR) pattern, and cellular fatty acid (CFA) profile (MIDI, Newark, Del.). 16S rRNA gene sequence analysis with 40 selected representative strains showed three distinct groups, with S. constellatus and S. intermedius found to be more closely related to each other than to S. anginosus, and further distinguished a biochemically distinct group of urogenital isolates within the S. anginosus group of isolates. Except for strains unreactive with the Fluo-card (8%), all S. anginosus and S. intermedius strains identified by sequencing were similarly identified by biochemical testing. However, 23% of the selected S. constellatus isolates identified by sequencing (9% of all S. constellatus isolates) would have been identified as S. anginosus or S. intermedius by biochemical tests. Although most S. anginosus strains formed one unique cluster by CFA analysis and most S. constellatus strains showed similar rep-PCR patterns, neither method was sufficiently dependable for identification. Whereas Lancefield group or lactose fermentation did not correspond to sequence or biochemical type, S. constellatus was most likely to be beta-hemolytic and S. intermedius was most likely to have a dry colony type. The most frequent isolate in our population was S. constellatus, followed by S. anginosus. There was an association of S. anginosus with a gastrointestinal or urogenital source, and there was an association of S. constellatus and S. intermedius with both the respiratory tract and upper-body abscesses.
E E Stobberingh - One of the best experts on this subject based on the ideXlab platform.
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in vitro antimicrobial susceptibility of the Streptococcus milleri group Streptococcus anginosus Streptococcus constellatus and Streptococcus intermedius
Journal of Antimicrobial Chemotherapy, 1996Co-Authors: Jan Jacobs, E E StobberinghAbstract:A collection of 423 clinical "Streptococcus milleri' strains was speciated and tested for susceptibilities to twelve antibiotics. Only 1.4% of the strains were of intermediate susceptibility to penicillin. None of the strains exhibited high-level resistance to gentamicin. Strains resistant to erythromycin, roxithromycin and clindamycin were found with a frequency of 2.6%, 2.4% and 2.4% respectively. Doxycycline resistance was found in 5.7% of the strains and occurred most frequently in Streptococcus anginosus. All the strains were susceptible to cefotaxime, vancomycin and teicoplanin. The results of this study do not indicate changing antibiotic resistance in strains of the "S. milleri' group, but local differences in antibiotic susceptibilities may occur.
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bacteremia involving the Streptococcus milleri group analysis of 19 cases
Clinical Infectious Diseases, 1994Co-Authors: Jan Jacobs, Henk G Pietersen, E E Stobberingh, Peter B SoetersAbstract:During a 3-year study period, 19 patients at the University Hospital of Maastricht developed bloodstream infections with species of the "Streptococcus milleri" group, for an incidence of 0.33 per 1,000 admissions. The patients' median age was 48 years; the male-to-female ratio was 2.8. Eleven patients (57.9%) had underlying diseases, among which malignancy was predominant. Local trauma to the mucosal barrier was an important risk factor. An associated site of infection was found most frequently in the abdominal and thoracic cavities (nine and five cases, respectively). Bacteremia was polymicrobial in four of 19 episodes. The 20 infecting S. milleri strains were identified to the species level; Streptococcus anginosus was the most prevalent (16 strains). Eight strains carried Lancefield group C. The isolates were sensitive to most antibiotics. Abscess formation was documented in nine cases (47.3%); repeated drainage procedures were required in half of these episodes. Mortality was high (five of 19 patients, or 26.3%).
A Coira - One of the best experts on this subject based on the ideXlab platform.
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prospective study of Streptococcus milleri hepatic abscess
European Journal of Clinical Microbiology & Infectious Diseases, 1998Co-Authors: J Corredoira, E Casariego, C Moreno, Luis Guillermo Villanueva, M Lopez J Alvarez, Jesus A Varela, Anibal Rodriguez, Pilar Alonso, A CoiraAbstract:Thirty-seven cases of microbiologically demonstrated pyogenic hepatic abscess were observed in a prospective study over a seven-year period. Biliary disease was the most common source of liver abscess (42%). Streptococcus milleri was the most common cause of hepatic abscess, accounting for 51% of the cases. Hepatic abscess is due to Streptococcus milleri clinically distinct from other forms of pyogenic liver abscess due to its torpid nature and the longer duration of its symptoms [42 vs. 11 days]. Occult hepatic abscess should be suspected if the blood culture is positive for Streptococcus milleri, since 28% of bacteremia cases due to Streptococcus milleri stem from hepatic abscesses. It is important to distinguish Streptococcus milleri from other members of the viridans streptococci group, which are frequently isolated as contaminants, but only exceptionally cause hepatic abscess. Unlike other pyogenic hepatic abscesses, those caused by Streptococcus milleri are frequently monomicrobial (79%). In the present study, empirical therapy of pyogenic hepatic abscess always included a drug that is effective against Streptococcus milleri.
Jorge P Parada - One of the best experts on this subject based on the ideXlab platform.
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Streptococcus milleri aortic valve endocarditis and hepatic abscess
Journal of Medical Microbiology, 2007Co-Authors: Rashid M Rashid, Wajeeh Salah, Jorge P ParadaAbstract:Although well-recognized animal pathogens, group C streptococci are relatively rare causes of human infection. The phenotypically small-colony group C ‘Streptococcus milleri’ are typically associated with suppurative disease of soft tissue and organs, including liver abscesses, while bacteraemia and endocarditis are distinctly less common. Herein, a case of ‘S. milleri’ causing both endocarditis and liver abscess in the same patient is reported.