Which of the following is a pathogenic member of the Enterobacteriaceae family?

• A. Klebsiella pneumoniae
• B. Staphylococcus aureus
• C. Escherichia coli
• D. Streptococcus pneumoniae

Answer: (C)

The choice of Escherichia coli as a pathogenic member of the Enterobacteriaceae family is correct because this bacterium includes some strains that are well-known for causing various pathogenic effects in humans. For instance, certain strains like E. coli O157:H7 are notorious for causing severe gastrointestinal disease, including hemorrhagic colitis and hemolytic uremic syndrome. Other pathogenic variants can lead to urinary tract infections, neonatal meningitis, and sepsis.

Escherichia coli is a significant part of the normal gut microbiota but also has a wide spectrum of pathogenic strains that can lead to different infections depending on the virulence factors they possess. This highlights its dual role as both a benign inhabitant of the human intestine and a potential pathogen.

In contrast, the other options include organisms outside of the Enterobacteriaceae family. Klebsiella pneumoniae is also a member of Enterobacteriaceae and can cause pathogenic infections, but Escherichia coli is more frequently recognized for its pathogenic strains in clinical settings. Staphylococcus aureus and Streptococcus pneumoniae belong to different bacterial families, specifically Staphylococcaceae and Streptococcaceae, respectively, and are not classified under Enterobacteri