Bacterial pathogens are harmful bacteria that can cause diseases in humans, animals, and plants. They invade the host's body, multiply, and produce toxins that disrupt normal functions. Common examples include Escherichia coli, which can lead to food poisoning, and Streptococcus pneumoniae, responsible for pneumonia. These pathogens can spread through various means, such as contaminated food, water, or direct contact with infected individuals. Prevention methods include proper hygiene, vaccination, and safe food handling practices. Understanding bacterial pathogens is crucial for public health and disease control efforts.