Final answer:
Microbes require virulence factors to become pathogenic. For example, enterohemorrhagic E. coli produces Shiga toxin causing severe disease, while Staphylococcus epidermidis can cause infection when a host's defenses are weakened.
Step-by-step explanation:
Pathogenicity and Virulence Factors
Microbes need certain factors to become pathogenic. This capability, known as pathogenicity, along with the degree of harm they cause, known as virulence, are crucial for a microbe to cause disease. Primary pathogens, like enterohemorrhagic E. coli (EHEC), produce virulence factors such as Shiga toxin, which can cause severe symptoms regardless of the host's immune system. Opportunistic pathogens, such as Staphylococcus epidermidis, typically only cause disease when the host's defenses are compromised, such as during hospital stays with invasive procedures.
Examples of Pathogenic Microbes
EHEC is an example of a primary pathogen, capable of causing severe disease by producing Shiga toxin which leads to symptoms like bloody diarrhea and renal failure. Staphylococcus epidermidis, though normally not harmful on the skin, can become an opportunistic pathogen in hospital settings and cause serious infections like endocarditis, exploiting compromised immune defenses.