Final answer:
The assertion that exogenous infections are caused by non-native microorganisms, like Salmonella, is correct. Normal flora such as staphylococci, enterococci, and streptococci can indeed cause endogenous infections when they end up in parts of the body where they're not typically found.
Step-by-step explanation:
The statement that microorganisms associated with an exogenous infection are those that do not exist as normal flora in humans such as salmonella is true.
Organisms like Salmonella are indeed part of the normal intestinal microbiota of many individuals, but specific strains are capable of causing exogenous infections when ingested in contaminated food or through other means. On the other hand, Staphylococci, enterococci, and streptococci, which exist as normal flora in an individual, are indeed responsible for endogenous infections. They can cause disease if they find their way into parts of the body where they are not normally present or if the immune system is compromised.
For example, Staphylococcus epidermis is generally avirulent when part of the skin's microbiota. However, it can cause serious infections such as endocarditis when introduced to the bloodstream, especially during surgical procedures. Similarly, E. coli typically resides harmlessly in the large intestine but can lead to a urinary tract infection if it enters the bladder, especially in women.