BETA-LACTAMASE: The capacity to produce beta-lactamase, an enzyme which hydrolyses penicillin and cephalosporines, is the main source of bacterial resistance to beta-lactamines, thus the important contribution of beta-lactamase inhibitors (clavanulanic acid, sulbactam and tazobactam).Beta-lactamase inhibitors inactivate these enzymes and, in association with beta-lactamines, offer wide spectrum bactericidal action (Gram negative bacilli, anaerobic germs, methicillin-sensitive staphylococci and streptococci) and can be used as first-line treatment in certain community-acquired and nosocomial infections.Widespread use of these inhibitors selects intermediate or resistant strains. Toxicity is low. Undesirable effects (poor digestive tolerance for oral formulations) are dose-dependent. RIGOROUS PRESCRIPTION: Recent development of bacterial resistance emphasizes the importance of rational use of these associations and the need for a better definition of the optimal doses. Prescriptions must avoid underdosing and excessively long treatments. Treatment should be simplified if sensitivity to an antibiotic with a narrower spectrum is recognized.