Microbial air monitoring in operating theatres: experience at the University Hospital of Parma

SummaryBackgroundMicrobial air monitoring in operating theatres has been a subject of interest and debate. No generally accepted sampling methods and threshold values are available.AimTo assess microbial air contamination in empty and working conventionally ventilated operating theatres over a three-year period at the University Hospital of Parma, Italy.MethodsAir sampling was performed in 29 operating theatres. Both active and passive sampling methods were used to assess bacterial and fungal contamination.FindingsIn empty theatres, median bacterial values of 12 colony-forming units (cfu)/m3 [interquartile range (IQR) 4–32] and 1 index of microbial air contamination (IMA) (IQR 0–3) were recorded. In working theatres, these values increased significantly (P < 0.001) to 80 cfu/m3 (IQR 42–176) and 7 IMA (IQR 4–13). Maximum recorded values were 166 cfu/m3 and 8 IMA for empty theatres, and 798 cfu/m3 and 42 IMA for working theatres. Combining active and passive samplings, fungi were isolated in 39.13% of samples collected in empty theatres and 56.95% of samples collected in working theatres. Over the three-year study period, bacterial contamination decreased in both empty and working theatres, and the percentage of samples devoid of fungi increased. In working theatres, a significant correlation was found between the bacterial contamination values assessed using passive and active sampling methods (P < 0.001).ConclusionMicrobiological monitoring is a useful tool for assessment of the contamination of operating theatres in order to improve air quality.