In Vitro Susceptibility of Streptococcus agalactiae Clinical Isolates to Beta-lactam Antibiotics.
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Accession number;99A0385877
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| Title;In Vitro Susceptibility of Streptococcus agalactiae Clinical Isolates to Beta-lactam Antibiotics. |
| Author;
IKEDA NOBUYUKI
(Juntendo Univ., Sch. of Med.)
HANAKI HIDEAKI
(Juntendo Univ., Sch. of Med.)
HIRAMATSU KEIICHI
(Juntendo Univ., Sch. of Med.)
KUWABARA YOSHINORI
(Juntendo Univ., Sch. of Med.)
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Journal Title;Journal of the Japanese Association for Infectious Diseases
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Journal Code:Z0760A
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ISSN:0387-5911
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VOL.73;NO.2;PAGE.163-170(1999)
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| Figure&Table&Reference;FIG.6, TBL.1, REF.18 |
| Pub. Country;Japan |
| Language;Japanese |
| Abstract;The susceptibility of Streptococcus agalactiae(S. agalactiae) clinical isolates of Juntendo University Urayasu Hospital, and type strain ATCC 13813 to beta-lactam antimicrobial agents was evaluated by means of macro-broth dilution MIC determination, killing kinetics and population analysis. When 106 cells of S. agalactiae were inoculated and cultured in Todd-Hewitt broth containing two-fold serial dilutions of penicillin, the viable cell count showed that about 102 cells survived irrespective of the penicillin concentration which ranged from 0.063 to 128.MU.g/ml. The result indicated that S. agalactiae had tolerance to penicillin (MICs were around 0.063.MU.g/ml). Furthermore, the S. agalactiae strains were found to have a paradoxical response to penicillin in an acidic condition (pH5.5). When the cell counts were performed at pH5.5, about 102 cells survived at penicillin concentrations from 0.016 to 0.125.MU.g/ml, while about 104 cells survived at the concentrations of 1 to 8.MU.g/ml. The antibiotic tolerance and paradoxical effects of S. agalactiae were also observed in killing kinetics. The ATCC 13813 and 10 out of 11 clinical strains showed slow response to penicillin-mediated killing at pH7.8, and ATCC 13813 and one of the clinical strains showed a reduced response with increase in penicillin concentration at pH5.5. These results suggested that the tolerance and paradoxical effect of S. agalactiae cells to betalactam antibiotics may be one of the reasons for frequent re-colonization of S. agalactiae at the time of delivery after the chemophylaxis in the 2nd trimester. (author abst.) |
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