Which organism is the focus of control in cooling water tower systems to prevent disease, as noted in guidelines?

• A. Streptococcus
• B. Legionella sp.
• C. Mycobacterium
• D. Clostridium

Answer: (B)

Legionella control is emphasized because these bacteria thrive in warm, stagnant water found in cooling towers and can be released as fine aerosols, which people can inhale. Guidelines point to Legionella as the primary disease risk in cooling-tower systems because outbreaks are tied to aerosols from these water sources, leading to Legionnaires’ disease or Pontiac fever. Managing this risk involves keeping water temperatures unfriendly to Legionella, maintaining disinfectant residuals, preventing stagnation and biofilm buildup, and conducting regular monitoring and maintenance. The other organisms listed aren’t the main focus of cooling-tower disease prevention—Streptococcus is usually spread person-to-person, not via aerosolized cooling-water exposure; Mycobacterium can be present in water but is not the key outbreak pathogen associated with cooling towers; Clostridium species are anaerobic and not typically dispersed through cooling-tower aerosols.