Which Gram-negative anaerobe is resistant to penicillin?

Bacteroides fragilis is identified as a Gram-negative anaerobic bacterium that is resistant to penicillin. This resistance stems from its unique cell wall structure and the presence of β-lactamase enzymes, which can break down penicillin and similar antibiotics, rendering them ineffective.

The physiology of Bacteroides fragilis allows it to thrive in the human body, particularly in the gastrointestinal tract, where it plays a role in normal microbiota; however, when it enters sterile sites, it can cause significant infections. Its resistance to penicillin makes it particularly important in clinical settings, as infections caused by this organism may require alternative treatment strategies.

The other bacteria listed are largely susceptible to penicillin. For instance, Escherichia coli, while it may possess some strains that are resistant to various antibiotics, is generally sensitive to penicillin. Haemophilus influenzae is also typically susceptible to penicillin, though it may exhibit some resistance due to β-lactamase production. Clostridium botulinum is a Gram-positive organism, which does not relate to the question as it is not a Gram-negative anaerobe. Thus, Bacteroides fragilis stands out as the correct answer due to its established resistance to pen