In E. coli true is –
**Core Concept**
E. coli is a gram-negative bacterium that exhibits diverse pathogenic potential, including enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), and uropathogenic E. coli (UPEC). Each of these pathotypes has distinct virulence factors that enable them to colonize and infect different parts of the human body.
**Why the Correct Answer is Right**
Uropathogenic E. coli (UPEC) is a significant cause of urinary tract infections (UTIs), particularly in women. The presence of pili (also known as fimbriae) in UPEC is a critical virulence factor that enables the bacteria to adhere to the uroepithelial cells in the bladder and kidneys. This adherence is a crucial initial step in the development of UTIs, allowing UPEC to establish a persistent infection. The pili of UPEC interact with mannose-containing receptors on the surface of uroepithelial cells, facilitating their attachment and subsequent colonization.
**Why Each Wrong Option is Incorrect**
**Option A:** ETEC (enterotoxigenic E. coli) is not typically invasive, as it primarily causes watery diarrhea by producing heat-labile and heat-stable enterotoxins. In contrast to UPEC, ETEC does not exhibit a strong invasive potential.
**Option B:** EPEC (enteropathogenic E. coli) does not act via cAMP (cyclic adenosine monophosphate). Instead, EPEC adheres to the intestinal epithelial cells and forms attaching-and-effacing lesions, which disrupt the normal brush border of the intestine and lead to diarrhea.
**Option D:** ETEC (enterotoxigenic E. coli) is responsible for causing traveler's diarrhea and other forms of watery diarrhea, but it is not associated with hemorrhagic uremic syndrome (HUS).
**Clinical Pearl / High-Yield Fact**
The presence of pili in UPEC is a key virulence factor that enables the bacteria to adhere to uroepithelial cells and establish a persistent UTI. Understanding the role of pili in UPEC pathogenesis is essential for developing effective therapeutic strategies to prevent and treat UTIs.
**✓ Correct Answer: C. Pilli present in uropathogenic type**