Development of resistance during antibiotic therapy.

The frequency of development of resistance during antibiotic therapy was evaluated by reviewing the literature according to prescribed criteria. Mean resistance rates were calculated to be 9.2% for broad spectrum penicillins, 8.6% for second and third generation cephalosporins, 10.0% for latamoxef, 4.7% for imipenem, 11.8% for ciprofloxacin and 13.4% for aminoglycosides. Emergence of resistance of the infecting organism was associated with therapeutic failure in about half of the cases with the exception of patients treated with aminoglycosides in whom development of resistance resulted in treatment failure in 85% of the cases. The possible benefit of combination therapy in terms of resistance development is discussed.