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Trends in antimicrobial susceptibility of the Streptococcus milleri group
Natsuo Yamamoto1, Toru Kubota, Masato Tohyama
1First Department of Internal Medicine, Faculty of Medicine, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan. k008743@med.u-ryukyu.ac.jp
Abstract:
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 microg/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.
Insights
This study analyzed 114 clinical Streptococcus milleri group strains, finding high intermediate susceptibility to penicillin G. Fluoroquinolones, particularly sitafloxacin, showed the greatest activity against these bacteria.
Area of Science:
- Microbiology
- Infectious Diseases
- Clinical Pharmacy
Background:
- The Streptococcus milleri group (SMG) comprises clinically significant bacteria often associated with various infections.
- Understanding antibiotic susceptibility patterns of SMG is crucial for effective treatment strategies.
Purpose of the Study:
- To identify clinical SMG strains and evaluate their susceptibility to a panel of 12 antibiotics.
- To determine the prevalence of resistance or intermediate susceptibility to commonly used antimicrobial agents.
Main Methods:
- Identification of 114 clinical SMG strains isolated at Ryukyu University Hospital between 1999 and 2000.
- Antimicrobial susceptibility testing was performed using standard methods for 12 different antibiotics.
Main Results:
- A notable 14% of SMG strains exhibited intermediate susceptibility to penicillin G.
- Cefaclor and cefotiam demonstrated lower activity compared to cefotaxime.
- Non-susceptibility rates were observed for erythromycin (8%), clindamycin (5%), and azithromycin (4%).
- Nearly all strains were susceptible to fluoroquinolones, with sitafloxacin being the most potent agent tested.
Conclusions:
- The study highlights a significant level of intermediate penicillin G resistance in clinical SMG isolates.
- Fluoroquinolones, especially sitafloxacin, represent a highly effective therapeutic option against SMG infections.
- Continuous monitoring of antibiotic resistance patterns is essential for guiding clinical practice.