A Risk for Nosocomial Infection: Contamination of Hospital Air Cooling Systems by Acanthamoeba spp.

Background and Objectives: In the most Iranian hospitals the internal air is cooled by a system comprising centrifugal blower fan and excelsior filters. Because amoeba can be present in air and dust it may enter into filters of cooling systems. It has been suggested that diffusion of amoebae cyst through air canals may contribute to various types of nosocomial infections. This study thus aimed to examine the possible contamination of filters of the conventional hospital cooling systems with free-living amoebae (FLA). Methods: Eighty-four cooling systems from four hospitals in Arak city (Central Iran) were sampled. Samples were cultured in defined medium and were tested from presence of Acanthamoeba spp. Findings: Ten out of the 18 hospital wards/sites and 23 out of 84 cooling systems surveyed (27.3%) were found to be contaminated by amoebae. Conclusions: Our results indicate a significant level of amoebae cysts contamination of cooling systems with excelsior filters in various hospital wards. Given the potential contribution of cyst to nosocomial infection, a prompt addressing of the problem is warranted. This may partly be accomplished by using non-aqueous or closed circulation cooling systems. Our study also highlights the need for similar investigations in other health settings and in larger scales to gain insight into the extent of the problem and the associated risks.