Which is NOT a mode of transmission in the chain of infection?

The correct choice relates to the understanding of modes of transmission within the chain of infection, which identifies how pathogens move from one host to another. Direct contact, droplet spread, and airborne particles are all recognized modes through which infectious agents can be transmitted.

Direct contact involves the transfer of pathogens through physical interaction with an infected person or their bodily fluids. Droplet spread refers to the transmission of pathogens through respiratory droplets that are expelled during actions like coughing or sneezing, which can infect others at close range. Airborne particles also allow for transmission, as these tiny particles can remain suspended in the air and be inhaled by individuals over a distance.

Invasive pathogens, however, refer to the characteristics of certain pathogens that can penetrate host defenses and cause disease rather than describing a method of how they are transmitted. Therefore, this choice does not fit the definition of a transmission modality in the context of the chain of infection, making it the correct answer for the question asked.