Final answer:
True, the normal flora and microbiota of an individual can cause disease. Under certain conditions, certain microorganisms can overgrow and cause opportunistic infections.
Step-by-step explanation:
The statement is True. The normal flora and microbiota of an individual can cause disease. While the resident microbiota plays an important role in immunity by inhibiting the growth of transient pathogens, certain conditions can lead to overgrowth of specific microorganisms, causing opportunistic infections. For example, E. coli normally found in the large intestine can cause a urinary tract infection if it enters the bladder. Similarly, antibiotics can disrupt the normal gut bacteria, allowing antibiotic-resistant species like Clostridium difficile to overgrow, leading to gastric problems.