Gram-negative bacteria are the most common primary pathogens: ○ Often, these organisms are part of the normal flora, but they may become opportunistic.

Are all Gram-negative bacteria pathogenic?

All gram negative bacteria of Enterobacteriacea which live in GIT (Gastro-Intestinal Tract) are considered normal flora and non-pathogenic unless some opportunistic conditions makes them pathogenic. It is also called Colon bacteria.

Why are Gram-negative bacteria pathogenic?

Gram-negative bacteria produce a variety of virulence factors, including toxins, fimbria, flagella, adhesins, invasins, and other secretory molecules, such as effectors and extracellular matrix, which are required for infection. Some virulence factors induce damage or death of host cells, while others ...