**Question:** Which of the following statement is false: March 2007

A. Introduction of the first-generation cephalosporin, cephalexin
B. Discovery of penicillinase by Howard Florey and Ernst Chain
C. Development of the first-generation cephalosporin, cephalexin
D. Discovery of the first-generation cephalosporin, cephalothin

**Correct Answer: D.**

**Core Concept:** Cephalosporins are a class of beta-lactam antibiotics that inhibit bacterial cell wall synthesis, thereby leading to bacterial cell lysis. The first-generation cephalosporins include cephalexin, cephalothin, and cephalothin, which are structurally similar but have distinct pharmacokinetic and pharmacodynamic properties.

**Why the Correct Answer is Right:** The first-generation cephalosporin, cephalothin, was discovered, not cephalexin or cephalothin. Cephalexin is a beta-lactam antibiotic that is chemically similar to cephalothin but has a longer half-life due to its lipophilic properties. Cephalothin, on the other hand, has a shorter half-life and is primarily used in parenteral administration.

**Why Each Wrong Option is Incorrect:**

A. Cephalexin is false because it was first introduced later than cephalothin. Cephalexin was introduced in the 1970s, whereas cephalothin was first discovered in the 1950s.

B. The discovery of penicillinase by Howard Florey and Ernst Chain is unrelated to the history of cephalosporins. Penicillinase is an enzyme that inactivates penicillin antibiotics, while cephalosporins are a different class of antibiotics that share some similarities, including their antimicrobial activity.

**Clinical Pearl:** Cephalosporins are often used for treating bacterial infections caused by gram-positive and gram-negative bacteria, including Streptococcus, Staphylococcus, Escherichia coli, Klebsiella, and Pseudomonas species. However, they should not be used in patients with a history of penicillin allergy due to cross-reactivity between penicillins and cephalosporins.

For students preparing for their exams, it is essential to be aware of the correct history of antibiotic discovery, as incorrect information can lead to misguided treatment choices and potential adverse events in clinical practice.