Final answer:
Methylene blue is incorrectly identified as an agent against gram-negative bacteria when discussing urinary anti-infective agents. Nitrofurantoin, norfloxacin, and cinoxacin are the correct urinary anti-infective agents against such bacteria, specifically in UTIs.
Step-by-step explanation:
After teaching a group of students about the action of urinary anti-infective agents, there is a need for additional teaching when students incorrectly identify methylene blue as an agent acting against gram-negative bacteria. The correct agents that work against gram-negative bacteria, particularly in the context of urinary tract infections (UTIs), include nitrofurantoin, norfloxacin, and cinoxacin (Cinobac). In contrast, methylene blue does not have antibacterial action and is mainly used as a dye in medical procedures. When treating a UTI caused by E. coli, a common gram-negative bacterium, one might consider fluoroquinolones like ciprofloxacin, nitrofurantoin, or the combination of trimethoprim/sulfamethoxazole.