Introduction: Bioaerosols are agents that can cause infection, allergy or induce other toxic effects in the human body. If the person exposed to such particles is not capable of their destruction or elimination from the body, the established chemical and physiological disorders can result in disease or death. The aim of this study was to assess the concentrations of bioaerosols in several wards of a teaching hospital.

Methods: Given that gas air-conditioners (split and window types) were used for ventilation in the eye operating room, internal intensive care unit, and the respiratory isolation room, these wards were selected for passive sampling. Sterile plates containing culture medium were exposed for two hours to the wards’ indoor ambient air. After this time, they were transferred to a lab to undergo incubation, colony count, and identification of the microorganisms. The data were analyzed using SPSS software, version 18, and the significance level of less than 0.05 was used. 

Results: Based on our findings, the highest colony-forming bacterial unit was observed 22 cfu/plate/h in the eye operating room and, the highest colony-forming fungal unit was observed 4 cfu/plate/h in the internal intensive care unit. Based on the results of the differential tests, the most prevalent bacteria identified were Staphylococcus epidermidis (75%) in the air of eye operating room and Staphylococcus saprophyticus (52%) in the internal intensive care unit and isolation room. The most prevalent identified fungi in the air of selected wards were related to Alternaria alternata (43%), Aspergillus flavus (24%), Penicillium (36%) and Curvularia (21%) types. Based on Spearman's correlation test, no significant relationship was observed between the factor of temperature and the number of fungal and bacterial colonies (r = 0.201, p = 0.42; r = -0.197, p = 0.41). Moreover, a meaningful relationship was observed only between the number of individuals and the bacterial colonies present in the air (r = 0.749, p = 0.0001).

Conclusion: Comparing the number of diagnosed colonies by 25 cfu/plate/h value showed that the numbers of colonies in all samples were lower than the mentioned values. So, the air-conditioning systems’ performance in reducing the number of bioaerosols in the studied wards was satisfactory. However, since the remaining bacterial and fungal contamination can cause serious infections in patients, it is highly necessary that the cleaning intervals and replacement time points of such filters be programmed based on the number of individuals present in the wards and their active surgical hours.


Keywords: bioaerosol, hospital, air-conditioning, indoor air
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