Which of the following statements about Enterobacteriaceae is true?

• A. They are all non-pathogenic
• B. They can be found in the human gastrointestinal tract
• C. They are exclusively aerobic organisms
• D. They do not develop resistance to antibiotics

Answer: (B)

The statement that Enterobacteriaceae can be found in the human gastrointestinal tract is true because this family of bacteria naturally includes many species that are part of the normal gut flora in humans and other animals. Species such as Escherichia coli are particularly well-known for their role in the intestines, where they aid in digestion and contribute to the microbial balance. While some members of this family can become pathogenic under certain conditions, such as with the presence of specific virulence factors, many species are fundamentally non-pathogenic and coexist with humans without causing disease.

The other statements reflect misconceptions about Enterobacteriaceae. Not all members are non-pathogenic, as some can lead to infections and diseases. The idea that they are exclusively aerobic is incorrect, as many species in this group are facultatively anaerobic, which means they can thrive in both the presence and absence of oxygen. Lastly, bacteria within the Enterobacteriaceae family are known to develop antibiotic resistance, which has become a significant concern in medical settings, highlighting the adaptability and resilience of these organisms in the face of antibiotic pressure.