Final answer:
Cross-infection requires exposure to a pathogen, followed by adhesion, invasion, and infection, facilitated by densely populated environments and contact with contaminated objects or surfaces.
Step-by-step explanation:
Principal prerequisites for cross-infection include a sequence of events: exposure, adhesion, invasion, and infection. For cross-infection to occur, there must be an encounter with a potential pathogen, termed exposure. Following exposure, pathogens must adhere to the host tissues; without adhesion, the infection process cannot begin. The pathogens then invade the tissues, which may lead to an infection if the body's defenses are bypassed or compromised.
Conditions facilitating cross-infection are diverse. For example, in the urban environment, the density of the population can increase the risk of spreading pathogenic organisms through touch or contact with contaminated objects, leading to cross-contamination. Moreover, the presence of a pathogen in a new host is essential for its transmission, and it may require passage through various portals of entry into the body, such as skin, mucous membranes, or parenteral routes.