Which microorganism is responsible for causing the vast majority of urinary tract infections?

• A. Streptococcus pyogenes
• B. Escherichia coli
• C. Pseudomonas aeruginosa
• D. Staphylococcus aureus

Answer: (B)

Verified step by step guidance

1. Understand that urinary tract infections (UTIs) are commonly caused by bacteria that can colonize the urinary tract, especially the bladder and urethra.
2. Recall that among the listed microorganisms, Escherichia coli is a gram-negative bacterium that is part of the normal intestinal flora and is the most frequent cause of UTIs due to its ability to adhere to the urinary tract lining.
3. Recognize that Streptococcus pyogenes is primarily associated with throat infections and skin infections, not UTIs.
4. Note that Pseudomonas aeruginosa and Staphylococcus aureus can cause UTIs but are less common and usually associated with complicated or hospital-acquired infections.
5. Conclude that the microorganism responsible for the vast majority of urinary tract infections is Escherichia coli because of its prevalence and pathogenic mechanisms in the urinary tract.