Selection of a fluoroquinolone-class disk for susceptibility tests

Area of Science:

• Microbiology
• Clinical Laboratory Science
• Pharmacology

Background:

• Accurate antimicrobial susceptibility testing (AST) is crucial for guiding antibiotic therapy.
• Fluoroquinolones represent a critical class of antibiotics used to treat various bacterial infections.
• Selecting a representative agent for class-wide AST simplifies laboratory procedures and ensures reliable results.

Purpose of the Study:

• To identify a single fluoroquinolone disk agent suitable for routine susceptibility testing of the entire fluoroquinolone class.
• To evaluate the performance of different fluoroquinolone disks against a diverse range of bacterial pathogens.

Main Methods:

• Disk diffusion and broth microdilution methods were employed for AST.
• A panel of 185 bacterial isolates was tested, including Enterobacteriaceae, Pseudomonas species, other gram-negative bacilli, and Staphylococcus aureus.
• Eight different fluoroquinolone agents were assessed for their representative capabilities.

Main Results:

• Pefloxacin, enoxacin, and ciprofloxacin disks demonstrated poor performance as class representatives.
• Amifloxacin, lomefloxacin, ofloxacin, temafloxacin, and fleroxacin disks showed potential for representing the fluoroquinolone class.
• Error rates (false-susceptible/false-resistant) ranged from 0-10% with resistant isolates, with lower rates expected in routine clinical settings.

Conclusions:

• Amifloxacin, lomefloxacin, ofloxacin, temafloxacin, or fleroxacin disks can serve as reliable representatives for routine fluoroquinolone susceptibility testing.
• These agents offer a minimal risk of significant errors in clinical laboratories.
• Pefloxacin, enoxacin, and ciprofloxacin are not recommended for broad fluoroquinolone class representation in AST.