Drinking-water microbiology: Which of the following water-borne diseases are caused by non-pathogenic bacteria?

Introduction / Context:
Water-borne diseases result from ingestion of water contaminated with pathogenic organisms (disease-causing microbes). Understanding which agents are pathogenic is essential for public-health protection, disinfection design, and monitoring programs.

Given Data / Assumptions:

• “Non-pathogenic bacteria” by definition do not cause disease.
• Cholera is caused by Vibrio cholerae (pathogenic bacteria).
• Typhoid fever is caused by Salmonella Typhi (pathogenic bacteria).
• Infectious hepatitis (commonly Hepatitis A or E) is caused by viruses, not non-pathogenic bacteria.

Concept / Approach:
Clarify terminology: pathogenic vs non-pathogenic organisms. Relate each listed disease to its causative agent. If any disease is caused by pathogens (bacteria or viruses), it cannot be attributed to non-pathogenic bacteria.

Step-by-Step Solution:

Verification / Alternative check:
Public-health references list Vibrio cholerae and Salmonella Typhi among notifiable pathogens; Hepatitis A/E are enteric viruses controlled by source protection and disinfection.

Why Other Options Are Wrong:

• Cholera and typhoid are explicitly caused by pathogenic bacteria.
• Infectious hepatitis is viral, not bacterial.
• “All of these” contradicts definitions; “None of these” is consistent with causation.

Common Pitfalls:
Confusing “indicator bacteria” (e.g., coliforms) with pathogens; assuming all water-borne illnesses are bacterial; overlooking viruses and protozoa in control strategies.

Final Answer:
None of these.