Final answer:
The most common pathogen associated with Surgical Site Infections (SSIs) is Staphylococcus aureus, which can cause severe conditions such as septic shock, particularly in hospital settings where it can be introduced to the body through contaminated medical materials.
Step-by-step explanation:
The pathogen leading in the percentage of Surgical Site Infections (SSIs) is Staphylococcus aureus, often referred to as MRSA when it's methicillin-resistant. SSIs can be introduced through various means, including trauma, prosthetic joint replacement, or from other infected body sites via the bloodstream. The pathogen's infective dose and the severity of the disease can vary significantly; for instance, while Salmonella enterica serotype Typhimurium can cause infection with just a single cell, other pathogens like S. aureus can lead to more severe diseases such as septic shock or endocarditis, particularly when introduced to the body through contaminated catheters or other medical procedures. The risk factors for SSIs include the immune status of the host and environmental factors, such as the pathogen's survival in different conditions such as the acidic pH of the stomach.