CLED medium is preferred over MacConkey for culture of organisms implicated in urine infection. The reason is:
## Core Concept
The question tests the understanding of microbiological media used for culturing urinary pathogens. CLED (Cystine Lactose Electrolyte Deficient) and MacConkey agar are selective media used for isolating and differentiating gram-negative bacteria, commonly implicated in urinary tract infections (UTIs).
## Why the Correct Answer is Right
CLED medium is preferred over MacConkey for the culture of organisms implicated in urine infections because it allows the growth of a wider range of urinary pathogens, including gram-positive bacteria and *Streptococcus* species, in addition to gram-negative bacteria. CLED agar supports the growth of *Enterococcus* and *Staphylococcus* species, which can also cause UTIs. The medium's ability to differentiate lactose fermenters (which produce acid and turn the colonies yellow) from non-lactose fermenters (which remain colorless or blue) aids in the identification of pathogens.
## Why Each Wrong Option is Incorrect
* **Option A:** This option is incorrect because while MacConkey agar does inhibit the growth of gram-positive bacteria, making it less suitable for isolating mixed cultures from urine.
* **Option B:** This option is incorrect as there's no direct correlation provided in standard microbiological practices that would make this statement universally applicable or accurate in this context.
* **Option D:** This option is incorrect because the primary reason for choosing CLED over MacConkey isn't directly related to the colony characteristics on blood agar.
## Clinical Pearl / High-Yield Fact
A key point to remember is that CLED agar is particularly useful in clinical settings for urine cultures because it supports the growth of a broad spectrum of bacteria that can cause UTIs, including both gram-negative and gram-positive organisms. This makes it a versatile medium for initial urine culture.
## Correct Answer: C.