Which of the following is NOT a common route of transmission for microorganisms in healthcare settings?

In healthcare settings, the transmission of microorganisms typically occurs through well-defined and recognized routes. Airborne spread involves tiny respiratory droplets that can linger in the air, allowing pathogens to be breathed in by individuals. Direct contact occurs when there is physical touching between an infected person and another individual, transferring microorganisms through skin or mucous membranes. Indirect contact involves transferring pathogens from one surface to another via fomites or contaminated instruments.

Invasive procedures, while they can indeed introduce microorganisms into the body, do not represent a common or natural route of transmission in the same way the others do. Instead, they are specific medical interventions that may introduce risk if proper sterilization and infection control measures are not followed. Therefore, while invasive procedures can be a method for infection, they are not a standard route of transmission for microorganisms in the broader, more routine context of healthcare settings. This distinction makes it the least common option compared to the others.