Cephalosporins are molecules containing a four membered ring known as beta-lactam. Derived from a fungus called Acremonium, cephalosporins are used pharmaceutically to treat bacterial infections such as Staphylococcus and Streptococcus. While cephalosporin antibiotics are closely related to penicillin antibiotics and can be used to treat some of the same bacterial infections, but some cephalosporin agents are tolerated by individuals allergic to penicillin providing a possible alternative.