Thermal disinfection at suboptimal temperature of Pseudomonas aeruginosa biofilm on copper pipe and shower hose materials

Background: Hospital-acquired infections caused by Pseudomonas aeruginosa have been linked to contaminated shower systems in health care. Thermal disinfection, whereby colonized outlets are flushed with existing hot water supplies, is a commonly used method to disinfect contaminated systems. Temperatures of 60°C are recommended for inactivation of P. aeruginosa; however, this is often not achievable at outlets.

Aim: To investigate whether thermal disinfection at a suboptimal temperature (58°C) can effectively eradicate planktonic P. aeruginosa and biofilm adherent on copper piping and shower hoses. Exposure times of up to 60 min and efficacy of repeated cycles were evaluated.

Methods: A type culture and an environmental strain of P. aeruginosa isolated from a hospital shower were tested. Planktonic bacteria and biofilm adhered to sections of copper pipe and shower hoses were exposed to water at 58°C for up to 60 min. Biofilms were tested with static water, flushing water and repeated cycles of disinfection. Remaining viable bacteria after disinfection were enumerated.

Findings: Planktonic P. aeruginosa remained viable after up to 60 min of thermal disinfection. With static water, biofilm was removed from copper piping after 15 min, but remained viable in shower hoses for up to 60 min. With thermal flushing, biofilm was fully eradicated from copper piping after 2 min, but remained viable on shower hoses. Repeated cycles did not shorten thermal disinfection exposure times.

Conclusion: Thermal disinfection at 58°C was effective at eliminating biofilm on copper; however, biofilm on shower hoses remained viable after 60 min of exposure.