Induction of resistance of Streptococcus pneumoniae to quinolones in vitro

Area of Science:

• Microbiology
• Pharmacology
• Infectious Diseases

Background:

• Antibiotic resistance in Streptococcus pneumoniae is a growing public health concern.
• Fluoroquinolones are important antibiotics for treating pneumococcal infections.
• Understanding resistance mechanisms is crucial for effective treatment strategies.

Purpose of the Study:

• To evaluate the development of resistance in Streptococcus pneumoniae exposed to increasing concentrations of fluoroquinolones.
• To compare the resistance profiles of levofloxacin, temafloxacin, ciprofloxacin, and norfloxacin.
• To assess cross-resistance patterns to other antibiotic classes.

Main Methods:

• Serial passage of twelve Streptococcus pneumoniae strains with increasing fluoroquinolone concentrations.
• Determination of minimum inhibitory concentrations (MIC90) for quinolones, macrolides, and penicillin G.
• Susceptibility testing of wild-type and passaged strains.

Main Results:

• A 2-fold increase in levofloxacin MIC90 was observed, significantly lower than increases for ciprofloxacin (32-fold), temafloxacin (16-fold), and norfloxacin (8-fold).
• Fourteen out of sixteen ciprofloxacin-induced resistant strains remained susceptible to levofloxacin.
• No cross-resistance was detected with macrolide or penicillin G antibiotics.

Conclusions:

• Levofloxacin demonstrated a lower propensity for inducing resistance in Streptococcus pneumoniae compared to other tested fluoroquinolones.
• Levofloxacin may be a valuable therapeutic option for pneumococcal infections, even in the presence of resistance to other fluoroquinolones.
• The absence of cross-resistance suggests targeted use of levofloxacin can be effective.