Final answer:
The broadest spectrum agents in the penicillin family are the carbapenems, including drugs like imipenem, meropenem, and doripenem, effective against a wide range of bacteria including MRSA.
Step-by-step explanation:
The agents with the broadest spectrum of activity within the penicillin family are the carbapenems. These include semisynthetic drugs such as imipenem, meropenem, and doripenem. Carbapenems exhibit a very broad spectrum of activity against both gram-positive and gram-negative bacteria, including those resistant to other ß-lactam antibiotics like the methicillin-resistant Staphylococcus aureus (MRSA).
The ß-lactam ring is central to the structure and function of these compounds, as it inhibits transpeptidase activity of penicillin-binding proteins, which are crucial for cell wall synthesis in bacteria. Cephalosporins also have a broad spectrum, including a new fifth-generation cephalosporin which is particularly significant. Unlike the monobactam aztreonam, which has activity only against gram-negative bacteria, carbapenems and cephalosporins cover a wide range of bacterial infections.