Final answer:
Narrow spectrum penicillinase-sensitive penicillins target gram-positive bacteria and some gram-negative bacteria, including E. coli, treating conditions like diphtheria and pneumonia. Their use is challenged by penicillinase-producing bacteria, leading to the development of resistant analogs like methicillin.
Step-by-step explanation:
The narrow spectrum penicillinase-sensitive penicillins are primarily effective against gram-positive bacteria and some gram-negative bacteria, like Escherichia coli. These antibiotics are particularly used in the treatment of infections caused by susceptible strains of bacteria, such as diphtheria, gonorrhea, pneumonia, syphilis, and various skin infections. The clinical use of narrow-spectrum penicillins is however limited by the presence of penicillinase-producing bacteria, which can degrade these antibiotics. To overcome this issue, scientists have created penicillin analogs, such as methicillin, that are resistant to penicillinase, although methicillin-resistant Staphylococcus aureus (MRSA) represents a significant challenge to these drugs.