Capability of 11 antipneumococcal antibiotics to select for resistance by multistep and single-step methodologies

Area of Science:

• Microbiology
• Antimicrobial Resistance
• Infectious Diseases

Background:

• * Streptococcus pneumoniae* is a major cause of bacterial infections.
• * Antibiotic resistance in pneumococci is a growing public health concern.
• * Understanding the resistance selection potential of different antibiotics is crucial.

Purpose of the Study:

• * To evaluate the in vitro resistance selection potential of tigecycline and other antibiotics against *Streptococcus pneumoniae*.
• * To compare the frequency of resistance development under sequential subculture and single-step selection.

Main Methods:

• * Twelve *Streptococcus pneumoniae* strains with diverse resistotypes were subjected to 50 sequential subcultures in the presence of sub-inhibitory concentrations of antibiotics.
• * Single-step resistance selection tests were performed for tigecycline, beta-lactams, macrolides/ketolides, and quinolones.

Main Results:

• * Tigecycline, amoxicillin-clavulanate, imipenem, and ceftriaxone did not select for resistant pneumococcal clones after prolonged exposure.
• * Azithromycin, clarithromycin, clindamycin, telithromycin, levofloxacin, moxifloxacin, and gemifloxacin selected for resistant clones.
• * Tigecycline demonstrated a low frequency of resistance in single-step tests compared to other antibiotic classes tested.

Conclusions:

• * Tigecycline and certain beta-lactams exhibit a low propensity for selecting resistant *Streptococcus pneumoniae* clones.
• * Macrolides, ketolides, and quinolones are more likely to select for resistant pneumococcal strains.
• * These findings have implications for antibiotic stewardship and the treatment of pneumococcal infections.