The term "bacterial agents" refers to bacteria that are responsible for causing diseases in humans or animals. These microorganisms can be pathogenic, which means they have the ability to cause illness when introduced into a host organism. Bacterial agents include various types of bacteria such as Streptococcus, Staphylococcus, Salmonella, and Escherichia coli (E.coli), among others. These microorganisms can be transmitted through direct contact, ingestion of contaminated food or water, or via vectors like insects. When bacterial agents infect a host organism, they can cause symptoms ranging from mild to severe illnesses such as pneumonia, meningitis, and gastroenteritis.