A broad-spectrum antibiotic can be used to treat a wide range of infections. A narrow-spectrum antibiotic is only effective against a few types of bacteria. There are antibiotics that attack aerobic bacteria, while others work against anaerobic bacteria. Aerobic bacteria need oxygen, while anaerobic bacteria don't.lthough there are a number of different types of antibiotic they all work in one of two ways: 1  A bactericidal antibiotic kills the bacteria. 2  Penicillin is a bactericidal. 3  A bactericidal usually either interferes with the formation of the bacterium's cell wall or its cell contents.