Which statement about Cephalexin's activity against bacteria is true?

Cephalexin, a first-generation cephalosporin antibiotic, is primarily effective against gram-positive bacteria, which makes the statement about its effectiveness accurate. This class of antibiotics is modeled to target the peptidoglycan layer in the cell wall of bacteria, a feature that is more pronounced in gram-positive organisms.

In addition to its activity against streptococci and staphylococci, Cephalexin does possess some activity against gram-negative bacteria; however, its effectiveness is significantly lower in comparison to that against gram-positive bacteria. The first-generation cephalosporins tend to have a narrower spectrum of activity concerning gram-negative organisms.

The other statements mention characteristics that do not accurately reflect Cephalexin’s activity profile. While it shows some activity against select gram-negative bacteria, it certainly is not highly effective against all gram-negative strains. Additionally, although it has less efficacy against certain bacteria that produce penicillinase (which can break down some beta-lactam antibiotics), this does not mean it has no activity against them; rather, the effectiveness is diminished. Lastly, it is not equally effective against both types of bacteria, highlighting its primary strength in combatting gram-positive infections.