4 diseases caused by bacterial infections?
Anthrax; chlamydia; bacterial conjuctivitis; Gonorrhea; Leprosy; there are a lot more
Salmonella,Botulism, Legionnaires' disease,Tuberculosis, Bubonic Plague, Typhus, most stomach ulcers (specifically due to H. pylori), Rocky Mountain Spotted Fever, gas gangrene, sepsis....who can stop at just 4?
What's already been said is quite true. Many infections are bacterial in nature. But if all you want is four, then I don't quite understand why you couldn't have just Googled this question.
1. Brucellosis
2. Tuberculosis
3. Legionnaire's disease
4. Salmonellosis