Which of the following best describes the spectrum of activity for Cephalexin?

Cephalexin is a first-generation cephalosporin antibiotic that exhibits a broad spectrum of activity primarily against both Gram-positive and some Gram-negative bacteria. It is particularly effective against a variety of Gram-positive organisms, including Streptococcus and Staphylococcus species, and has some activity against Gram-negative bacteria such as Escherichia coli and Klebsiella. This characteristic of targeting multiple types of bacteria, rather than being limited to just one category, is why the answer indicating effects against most bacteria is correct.

The option suggesting limitation to Gram-positive bacteria does not account for Cephalexin's ability to also combat certain Gram-negative organisms. Additionally, the choice mentioning effectiveness solely against anaerobic bacteria overlooks the fact that Cephalexin’s primary action is not confined to anaerobic environments; it is often utilized in treating infections caused by aerobic bacteria as well. Lastly, the description of effectiveness against viral pathogens is incorrect, as Cephalexin, like other antibiotics, does not target viruses and is not effective in treating viral infections. Thus, the option reflecting effects against most bacteria provides the most accurate representation of Cephalexin’s spectrum of activity.