Antibiotics fall into several main classes, including penicillins, such as amoxicillin; cephalosporins, such as Keflex; macrolides, such as Biaxin and Zithromax; and fluroquinolones, such as Cipro and Levaquin, notes eMedicineHealth. Sulfonamides, such as Bactrim, and tetracyclines, including Vibramycin and Sumycin, are others.
There are more than 100 antibiotics, according to eMedicineHealth. Doctors choose antibiotics for patients based on the causes of infections or the bacteria believed to be responsible. The doctor may base the choice of antibiotic solely on a clinical exam, or he may order laboratory tests to identify the bacteria responsible for symptoms and then select an antibiotic based on the results of laboratory findings.