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In vitro susceptibility of six fluoroquinolones against invasive Streptococcus pneumoniae isolated from 1996 to 2001
1Division of Clinical Research, National Health Research Institutes, Taipei, Taiwan.
Abstract:
A total of 331 invasive nonduplicated Streptococcus pneumoniae isolates from three sampling periods during 1996 to 2001 were tested for susceptibility to recently developed fluoroquinolones. Five major serotypes, 23F, 6B, 14, 19F, and 3, were frequently encountered in this collection. Penicillin nonsusceptible isolates constituted 52.9% from 1996 to 1997, 61.6% from 1998 to 1999, and 60.0% from 2000 to 2001. Fifty-seven percent of the isolates were susceptible to cefotaxime, 56.5% to ceftriaxone, 54.1% to cefepime, and 52.6% to cefuroxime. Macrolide-susceptible isolates constituted less than 14% of the total sample, and no vancomycin-resistant isolates were detected. For fluoroquinolones, MIC90 was lowest for gemifloxacin (MIC90 = < or = 0.12 microg/ml), followed by moxifloxacin (MIC90 = 0.25 microg/ml), gatifloxacin (MIC90 = 0.5 microg/ml), sparfloxacin (MIC90 = 0.5 microg/ml), levofloxacin (MIC90 = 1 microg/ml), and ciprofloxacin (MIC90 = 2 microg/ml). All isolates were susceptible to sparfloxacin, levofloxacin, gatifloxacin, and gemifloxacin apart from one isolate (0.3%), which was simultaneously resistant to sparfloxacin, levofloxacin, and gatifloxacin. Mutations at the positions S81F of GyrA and D435N and I460V of ParC were detected for this multiple drug resistant isolate. The in vitro results suggest that recently developed fluoroquinolones are very effective against invasive S. pneumoniae isolates in Taiwan. Nevertheless, emerging fluoroquinolone resistance should be acknowledged and clinicians alerted. Surveillance should be carried out to monitor any changes in antibiotic resistance of S. pneumoniae.
Insights
Invasive Streptococcus pneumoniae isolates in Taiwan show high susceptibility to newer fluoroquinolones, with gemifloxacin being the most effective. Emerging fluoroquinolone resistance necessitates ongoing surveillance and clinical awareness.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Streptococcus pneumoniae is a leading cause of invasive bacterial infections.
- Antibiotic resistance in S. pneumoniae is a growing global health concern.
- Understanding susceptibility patterns is crucial for effective treatment strategies.
Purpose of the Study:
- To evaluate the in vitro susceptibility of invasive Streptococcus pneumoniae isolates to newer fluoroquinolones.
- To assess the prevalence of resistance to other antibiotic classes.
- To identify potential trends in antibiotic resistance in Taiwan.
Main Methods:
- Testing of 331 invasive non-duplicated S. pneumoniae isolates collected between 1996 and 2001.
- Determination of minimum inhibitory concentrations (MICs) for various fluoroquinolones.
- Phenotypic and genotypic analysis for antibiotic resistance mechanisms.
Main Results:
- High susceptibility rates observed for newer fluoroquinolones, particularly gemifloxacin (MIC90 ≤ 0.12 µg/ml).
- Significant penicillin non-susceptibility (over 50%) and moderate resistance to cephalosporins were noted.
- A single isolate exhibited multi-drug resistance to several fluoroquinolones, linked to specific GyrA and ParC mutations.
Conclusions:
- Recently developed fluoroquinolones demonstrate high in vitro efficacy against invasive S. pneumoniae in Taiwan.
- The emergence of fluoroquinolone resistance, though rare, requires attention and clinical vigilance.
- Continuous surveillance is essential to monitor evolving antibiotic resistance patterns of S. pneumoniae.
