Penicillins in perspective.

Fifty-three years after their discovery the penicillins still present a challenge to laboratory workers and clinicians. They are members of the broader beta-lactam group and are susceptible to inactivation by beta-lactamases from Gram-positive and Gram-negative bacteria. Countering these enzymes is achieved by producing more stable penicillin molecules or by using enzyme-blocking agents like clavulanic acid to protect the antibiotics. The field is confusing and to assist in defining the present-day role of the group, the concept of a microbiological profile is considered. The modes and sites of action of the penicillins and the beta-lactamases are presented and both are classified. The place of penicillins in the treatment of life-threatening and lesser infections, and in prophylaxis, is discussed.