Drinking water hygiene: the presence of which class of bacteria in a water sample indicates disease-causing potential such as typhoid risk to consumers?

Introduction / Context:
Microbiological safety is the most critical aspect of drinking water quality. Bacteria that can cause disease in humans are termed pathogenic. Their presence indicates the potential for waterborne illnesses including typhoid, cholera, and dysentery.

Given Data / Assumptions:

• Sample type: water intended for human use.
• Concern: diseases such as typhoid.
• Indicator concept: presence of disease-causing organisms.

Concept / Approach:
Pathogenic bacteria (e.g., Salmonella typhi for typhoid) are organisms capable of causing disease. Routine monitoring often uses indicator organisms (e.g., fecal coliforms) because direct detection of every pathogen is impractical, but the class that directly causes disease is pathogenic bacteria.

Step-by-Step Solution:

Verification / Alternative check:
Public health guidance classifies organisms as pathogenic when they cause disease in humans. Water quality standards target zero tolerance for fecal indicators precisely to minimize pathogenic risk.

Why Other Options Are Wrong:

• Aerobic: describes oxygen use, not disease causation.
• Anaerobic: metabolism category, not inherently disease-causing.
• Non-pathogenic: explicitly not disease-causing.
• Commensal: coexists without harming the host.

Common Pitfalls:
Confusing metabolic descriptors (aerobic/anaerobic) with pathogenicity; assuming all bacteria in water are harmful, which is incorrect.

Final Answer:
Pathogenic