TABLE 5.

Cross-resistance of azithromycin-nonsusceptible clones with other antibiotics following 10 serial passages in drug-free medium

H. influenzae strainAzithromycin MIC (μg/ml)Cross-resistance of the selected azithromycin-resistant clone
OriginalSelected (no. of days)Antimicrobial agentMIC (μg/ml)
Before drug-free passageAfter 10 drug-free passages
153-0081>64 (37)Ceftobiprole0.060.125
Amoxicillin-clavulanate0.50.5
Ceftriaxone0.0160.008
Azithromycin>6432
Telithromycin24
Moxifloxacin0.060.03
110-0611>64 (34)Ceftobiprole0.1250.125
Amoxicillin-clavulanate21
Ceftriaxone0.030.016
Azithromycin>64>64
Telithromycin4>32
Moxifloxacin10.125